Digital Dentistry 2018/19

PROFESSIONAL DENTISTRY PRESENTS...

DIGITAL DENTISTRY 2018/19 Edition

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Software that blends the old and the new. Now, that’s impressive.

Behold the CS 3600 Intraoral Scanner with the latest acquisition software. Updated capabilities include Software that blends the old and the new. Now, that’s impressive. a patent pending Hybrid Scan Workfl ow that’s to capture evenimpressive. the most challenging margin lines.

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Call 0800 169 9692 tothe speak to aNow, Carestream Dental representative.

The CSFrom 3600scanning enables restorative to obtain a more complete capture andimpressive. thereby create better fitting prosthetics. speed improvements to custom sound options, see what’s new at Behold the CS 3600 Intraoral Scanner with the latest acquisition software. Updated capabilities include prosthetics. From scanning speed improvements to custom sound options, see what’s new at carestreamdental.co.uk/CS3600.

Call 0800 169 9692 to speak to a Carestream Dental representative.

Software that blends theow oldthat’s anddesigned the new. impressive. a patent pending Hybrid Scan Workfl to Now, capturethat’s even the most challenging margin lines. carestreamdental.co.uk/CS3600.

Call 0800 169 9692 to speak to a Carestream Dental representative.

Behold the CSrestorative 3600 Intraoral Scanner withathe latest acquisition software.

Updated capabilities The CS 3600 enables dentists to obtain more complete capture and thereby create better fiinclude tting a patent pending Hybrid Scan Workfl ow that’s designed to capture even the most challenging prosthetics. From scanning speed improvements to custom sound options, see what’s new at margin lines.

The CS 3600 enables restorative to 9692 obtaintoa speak more complete capture and thereby create better fitting carestreamdental.co.uk/CS3600.

Call dentists 0800 169 to a Carestream Dental representative. prosthetics. From scanning speed improvements to custom sound options, see what’s new at carestreamdental.co.uk/CS3600. Call 0800 169 9692 to speak to a Carestream Dental representative.

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© 2018 Carestream Dental LLC. mark margin lines scan impression WORKFLOW INTEGRATION I HUMANISED TECHNOLOGY I DIAGNOSTIC EXCELLENCE

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Learning.

Networking.

Sourcing.

Calling all

Practice Managers Get a year’s worth of verifiable CPD for everyone in your practice!

As a practice manager, if you attend any of our 4 upcoming events, you and any of your colleagues who attend will be eligible for a FREE CPD top-up!* To redeem this offer all you have to do is attend any verifiable CPD conference OR the leading exhibition. Visit professionaldentistry.co.uk for more information.

/ProDentistry.co.uk

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*All colleagues must attend a CPD conference to qualify for a top-up. The amount of top-up CPD content provided will be determined by the annual verifiable CPD requirements of each attendee. An email address for each user is required in order to use Professional Dentistry CPD E-Publications.

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Contents...

1 Update on digital imaging and radiography.............................. 4

Creating the virtual digital patient.................................................... 10

Advantages of digital radiography.................................................. 10

Viewing can be critical....................................................................... 12

Monitor specifications......................................................................... 13

References........................................................................................... 15

CT Dent Editorial...................................................................................... 16 Why refer to a specialist dental imaging centre?........................... 16

Why CT Dent......................................................................................... 16

2 Advances in digital partial dentures............................................... 18

Communication issues........................................................................ 19

3 How digital dental software aids the practitioner...................... 24

A wider picture.................................................................................... 25

Future proof?........................................................................................ 29

References........................................................................................... 30

4 Digitally guided implant design and treatment.......................... 32

Digital versus analogue for single implants...................................... 32

Digital workflow scrutinised................................................................. 33

Time-efficiency..................................................................................... 34

Digital frameworks tested................................................................... 34

Scanning accuracy............................................................................. 35

Placement is key.................................................................................. 36

References........................................................................................... 37

5 Digital impressions – the ultimate overview?............................... 38 Advantages......................................................................................... 38 Disadvantages..................................................................................... 40

The question of accuracy.................................................................. 41

Clinical uses to date............................................................................ 41

Combining digital technologies........................................................ 42

References........................................................................................... 43

6 3D printing and digital dentistry........................................................ 44

3D printing technologies used in dentistry........................................ 45

3D printing uses in dentistry................................................................ 47

Advantages and disadvantages of 3D printing.............................. 49

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Chapter 1

Update on digital imaging and radiography

Make this CPD Verifiable Turn to page 50 to find out how

Digital radiography is increasingly accepted as the future direction in dentistry. In this article we look at some of the recent developments and advice in relation to its use and to patient care.

Radiography is considered the most frequent diagnostic tool in daily dental practice, with more than one quarter of all medical radiographs in Europe being made by dentists. Since the discovery of x-rays 120 years ago, dental radiographs have been the predominant source of diagnostic information in the oral and maxillofacial region. Yet, two-dimensional (2D) imaging techniques are unable to depict complicated three-dimensional (3D) anatomical structures and related pathologies.

In the 1990s, there was a growing tendency in using 3D information as an aid for dentomaxillofacial diagnosis and treatment, while in the early years of the 21st century cone beam computed tomography (CBCT) imaging started to offer a solution for this growth by being made available in specialty clinics. These developments went hand in hand with the increasing use of 3D imaging applications for presurgical planning and transfer of oral implant treatment. While the required 3D acquisition for dental applications was initially realised by medical computed tomography (CT), dental CBCT rapidly took over. The main reasons for the triumph of CBCT are its capabilities of volumetric jaw bone imaging at reasonable costs and doses, with a relative advantage of having a compact, affordable, and nearby or in-house equipment.

For clinicians involved in implant rehabilitation, the power of a dental 3D dataset is not only situated in the diagnostic field, but also in the potential of gathering integrated patient information for presurgical and treatment applications related to oral implant placement. Nowadays, rapid advances of digital technology and computer-aided design/computer-aided manufacturing (CAD/CAM) systems are indeed creating challenging opportunities for diagnosis, surgical implant planning and delivery of implant-supported prostheses. While there is still a huge demand for

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maximised integration of 3D datasets acquired from various imaging sources, there is also a call for simplified solutions. Yet, when striving for optimised patient-specific implant rehabilitation, the ultimate goal remains to fully integrate the available 3D imaging data thus creating the virtual patient, aiding presurgical simulation and peroperative transfer to the surgical field with further prosthetic rehabilitation.1 Dental cone beam computed tomography (CBCT) uses a special type of x-ray equipment when a clinician feels that regular dental or facial x-rays are not sufficient or further information is required for treatment planning purposes. CBCT scans provide three dimensional (3D) images of teeth, soft tissues, nerve pathways and bone in a single scan.

With CBCT, an x-ray beam in the shape of a cone is moved around the patient to produce a large number of images called views. Dental cone beam CT was developed as a means of producing similar types of images but with a much smaller and less expensive machine that could be placed in an outpatient department or even a dental practice. CBCT provides detailed images of the bone and is performed to evaluate diseases of the jaw, dentition, bony structures of the face, nasal cavity and sinuses. It does not provide the full diagnostic information available with conventional CT, particularly in evaluation of soft tissue structures such as muscles, lymph nodes, glands and nerves. However, cone beam CT has the advantage of lower radiation exposure compared to conventional CT. Dental cone beam CT is commonly used for treatment planning of orthodontic issues. It is also useful for more complex cases that involve: •

Surgical planning for impacted teeth

•

Diagnosing temporomandibular joint disorder (TMJ)

•

Accurate placement of dental implants

•

Evaluation of the jaw, sinuses, nerve canals and nasal cavity

•

Detecting, measuring and treating jaw tumours

•

Determining bone structure and tooth orientation

•

Locating the origin of pain or pathology

•

Cephalometric analysis

•

Reconstructive surgery.

6

3Shape TRIOS3 and Roland DWX-4W 3Shape 3Shape 3Shape TRIOS3 TRIOS3 TRIOS3 and and and Roland Roland Roland DWX-4W DWX-4W DWX-4W

A truly open CAD/CAM system delivered by a truly open partner AA truly truly A truly open open open CAD/CAM CAD/CAM CAD/CAM system system system delivered delivered delivered byby aby a truly truly a truly open open open partner partner partner

3Shape TRIOS3 and Roland DWX-4W A truly open CAD/CAM system delivered by a truly open partner

3Shape TRIOS3 and Roland DWX-4W A truly open CAD/CAM system delivered by a truly open partner

3Shape TRIOS3 and Roland DWX-4W 3Shape TRIOS3 and Roland DWX-4W

A truly open CAD/CAM system delivered by a truly open partner

A truly open CAD/CAM system delivered by a truly open partner 3Shape TRIOS3 and Roland DWX-4W A truly open CAD/CAM system delivered by a truly open partner

Scan Scan Scan Scan With 3Shape TRIOS3 Scan

With 3Shape TRIOS3

Design

With 3Shape Practice Lab

Mill

With Roland DWX-4W

ESM Digital Solutions brings together two dental laboratory household names and offers an attractive and effective CAD/CAM solution for practices wishing to embrace CAD/CAM workflows in house.

3Shape TRIOS3, confirmed as the most accurate intra-oral scanner offer fast, patient friendly scanning for use in-house with 3Shape Practice Lab, Implant Studio and OrthoSystem or to simply send cases to your preferred ‘TRIOS Ready’ laboratory. 3Shape Practice Lab offers an efficient and user friendly design workflow for a wide range of monolithic indications. Roland’s DWX-4W delivers laboratory quality results for a wide range of materials. Together with ESM’s experience, commitment and support, this solution offers you the most flexible and open in-house CAD/CAM system available. For further information and to experience this workflow first hand, contact us today. We look forward to taking care of you.

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ESM Digital Solutions brings together two dental laboratory household names and offers an attractive and effective CAD/CAM solution for practices wishing to embrace CAD/CAM workflows in house.

3Shape TRIOS3, confirmed as the most accurate intra-oral scanner offer fast, patient friendly scanning for use in-house with 3Shape Practice Lab, Implant Studio and OrthoSystem or to simply send cases to your preferred ‘TRIOS Ready’ laboratory. 3Shape Practice Lab offers an efficient and user friendly design workflow for a wide range of monolithic indications. Roland’s DWX-4W delivers laboratory quality results for a wide range of materials. Together with ESM’s experience, commitment and support, this solution offers you the most flexible and open in-house CAD/CAM system available. For further information and to experience this workflow first hand, contact us today. We look forward to taking care of you.

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Roland’s Roland’s Roland’s DWX-4W DWX-4W DWX-4W delivers delivers delivers laboratory laboratory laboratory design workflow for a wide range of monolithic indications. Roland’s DWX-4W delivers laboratory quality results for a wide range of materials. Together with ESM’s experience, quality results for aawide range Together with ESM’s experience, quality quality quality results results results for for a wide for a wide range wide range range ofofmaterials. ofmaterials. materials. of materials.

Together Together Together with with ESM’s with ESM’s ESM’s experience, experience, experience, commitment and support, this solution you and theopen most flexible and open commitment and support, this solution offers you the offers most flexible commitment commitment commitment andand support, and support, support, thisthis solution this solution solution offers offers offers youyou the you the most the most flexible most flexible flexible andand open and open open in-house CAD/CAM system available.

For further information and toinformation experience in-house CAD/CAM system available.

For further and to experience in-house in-house in-house CAD/CAM CAD/CAM CAD/CAM system system system available. available. available.

For For further For further further information information information and and to and experience to experience to experience this workflow first hand, contact us today. We look forward to taking care of you. this workflow first hand, contact us today. We look forward to taking care of you. thisthis workflow this workflow workflow firstfirst hand, first hand, contact hand, contact contact us today. us today. us today.

WeWe look We look forward look forward forward to taking to taking to taking care care ofcare you. of you. of you.

UK: (020) 8816 7840

info@esmdigitalsolutions.com

Ireland: (01) 808 4446

www.esmdigitalsolutions.com

Authorized Reseller

UK: (020) 8816 7840

UK: (020) 8816 7840

info@esmdigitalsolutions.com

Ireland: (01) 808 4446

www.esmdigitalsolutions.com

Authorized Reseller

Scan

With 3Shape TRIOS3

Design

With 3Shape Practice Lab

ESM Digital Solutions brings together two dental laboratory household names and offers an attractive and effective CAD/CAM solution for practices wishing to embrace CAD/CAM workflows in house.

3Shape TRIOS3, confirmed as the most accurate intra-oral scanner offer fast, patient friendly scanning for use in-house with 3Shape Practice Lab, Implant Studio and OrthoSystem or to simply send cases to your preferred ‘TRIOS Ready’ laboratory. 3Shape Practice Lab offers an efficient and user friendly design workflow for a wide range of monolithic indications. Roland’s DWX-4W delivers laboratory quality results for a wide range of materials. Together with ESM’s experience, commitment and support, this solution offers you the most flexible and open in-house CAD/CAM system available. For further information and to experience this workflow first hand, contact us today. We look forward to taking care of you.

UK: (020) 8816 7840

info@esmdigitalsolutions.com

Ireland: (01) 808 4446

www.esmdigitalsolutions.com

info@esmdigitalsolutions.com

Ireland: (01) 808 44467840 www.esmdigitalsolutions.com Authorized Reseller UK: (020) 8816 info@esmdigitalsolutions.com

UK:UK: (020) UK: (020) 8816 (020) 8816 7840 8816 7840 7840 info@esmdigitalsolutions.com info@esmdigitalsolutions.com info@esmdigitalsolutions.com Ireland: (01) 808 4446 www.esmdigitalsolutions.com Authorized Reseller Ireland: Ireland: Ireland: (01)(01) 808 (01) 808 4446 808 4446 4446 www.esmdigitalsolutions.com www.esmdigitalsolutions.com www.esmdigitalsolutions.com Authorized Authorized Authorized Reseller Reseller Reseller

7

Mill

With Roland DWX-4W

Authorized Reseller

“So glad I had Traxodent retraction paste for this case!”

Dr. Timothy Bizga describes how he successfully used Traxodent® Hemodent® Paste Retraction System help capture an outstanding final impression

1.

The pre-operative situation.

Tooth No. 20 had root canal therapy and a large composite build-up.

A full coverage crown was recommended, and the patient agreed.

Because of the size of the build-up I was certain that a subgingival preparation would be needed and adequate tissue management for a good impression.

2.

Occlusal view of the completed preparation on tooth No. 20.

Based on the amount of sulcular fluid and blood, tissue management and hemostasis was needed.

Although much of the preparation ended up being equi-gingival, there were some areas of the marginal gingiva that were traumatized during the procedure to ensure clean margins on sound tooth structure.

3.

Traxodent paste in-place.

Traxodent retraction paste was dispensed around the tooth.

Even with careful dispensing, more bleeding is seen from the surrounding inflamed tissue.

Call: +610-239-6029

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4.

Patient biting on a Retraction Cap (PremierÂŽ Dental).

Retraction Caps are a dense cotton pellet and come in three sizes.

In this case, I selected a #2 (medium) size Retraction Cap that fit snuggly over the tooth and when the patient bit down, forced the Traxodent in the sulcus and created direct pressure to facilitate hemostasis.

5.

After Traxodent paste is rinsed away.

Wow! After approximately 2 minutes, using water, the Traxodent paste is completely rinsed away leaving a clean and dry prep ready for impressioning.

The thing that I was so pleased about at this stage was that after the Traxodent was removed the bleeding had stopped and I was very confident my impression would turn out perfectly.

6.

Final impression of tooth No. 20.

Using a T-LOC Triple Tray, the final impression for tooth No. 20 was precisely captured.

I really like T-LOC trays because the retentive grooves on the side of the trays eliminate the need for tray adhesive; they are rigid to prevent distortion, and come in many shapes and sizes.

7.

Close-up of the final impression for tooth No. 20.

I am so glad I had Traxdodent when I did this case.

I was able to achieve the tissue management required to capture the final impression, and no retraction cord was needed.

To me this means that I did not have to pack retraction cord – a tedious and time consuming step for me – and for my patients this means that there is less chance of post-operative discomfort from the surrounding gingiva.

Visit: www.premusa.com/dental-home

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Creating the virtual digital patient The aforementioned evolution towards the concept of a virtual patient for dental implant surgery, creates new challenges for appropriate CBCT scanning. The virtual patient is a digital record that is used to plan the ideal implant position with respect to aesthetic, prosthetic and surgical requirements. It integrates information (datasets) obtained from facial scanning technology, digital intra-oral impressions and CBCT imaging in one virtual coordinate system. The arrangement of the virtual teeth is planned with regards to aesthetic and prosthetic functional requirements so that the ideal prospective implant position can be identified. Subsequently, a surgical guide is fabricated for fully guided implant insertion, and the treatment can then proceed with creating the provisional and final prosthesis using the same pre-operatively planned prosthetic setup.

There are several imaging requirements to achieve this functional, prosthetically oriented surgical goal, which are related to the accuracy of each scanning modality as well as to the fidelity of the image integration procedure. Three-dimensional (3D) facial scanning provides information regarding the external soft tissue profile in three dimensions, and it can be of tremendous aid during the 3D digital smile design phase of the treatment. In prosthodontics, facial scanning needs to provide high resolution 3D mesh data and photorealistic texture rendering in order to permit a virtual clinical evaluation phase. Several facial scans in neutral head position, maximum smile and using cheek retractors need to be obtained and merged together and the labial surfaces of the anterior teeth should be clearly depicted to allow registration with the digital dental model scans. In order to integrate facial scanning with CBCT, the forehead region needs to be clearly visible in both scans. This approach has been previously validated and the accuracy was found within clinically acceptable limits. Recent studies demonstrated the applicability of the virtual patient approach to preoperatively plan the surgical placement of dental implants and to CADCAM design and fabricate screw retained prosthesis in partially and completely edentulous patients.

Advantages of digital radiography Digital radiography requires 90% lesser dose compared to E-speed film. In digital imaging, image quality may be interactively manipulated after image acquisition, i.e., contrast, blur and noise may be altered digitally. Filtering of the digital image may result in a reduction of blur of structure boundaries. Diagnostic accuracy of

10

STEP 1

Advantages for the Clinician

Anesthetizing the attached gingiva

• When anesthetic solution is delivered into cancellous bone, excellent pulpal anesthesia is obtained, even in patients with irreversible pulpitis or hypersensitive teeth.

STEP 2 Perforating the cortial plate

• Intraosseous Anesthesia saves valuable time because there is no delay between injection and effect. Work on the tooth can commence in less than 30 seconds after the injection.

STEP 3

Advantages for the patient

Inserting the injection-needle in the perforation

• The patient experiences minimal pain during the dental procedure itself, and on leaving the dental office there will be no balooning of soft tissues and a much lessened feeling of numbness.

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the detection of carious lesions is increased by digital contrast enhancement and filtering. Measurements of length, angle, and area can be made on a digital image.

Low-pass spatial filtering (smoothing) reduces the image noise. However, it decreases image resolution. High-pass spatial filtering (hardening) enhances edges to create a crisper image, but with more noise. It facilitates the detection of boundaries of low-contrast regions. In digital radiography, the same image can be used for various diagnostic purposes, for instance, marginal bone loss which requires lighter images and caries detection requiring darker images. With the solid-state sensor system, the image is displayed immediately post-exposure. Although there is a lag time between scanning and the appearance of an image it is faster than the conventional method. Digital Imaging and Communications in Medicine (DICOM) standards encompass primary and secondary diagnostic images acquired digitally that provide a basis for interoperability of digital systems’ output, facilitating a common method of transmission for medical radiographic images. DICOM compliant systems utilise common file formats that are universally recognised. For instance, when one is contemplating digital image submission to colleagues for referral or to insurance companies or other third party organisations.2

Viewing can be critical Many dental practitioners use flat panel monitors in their practices on a daily basis, and for those who have made the move to digital imaging, the use of this device often extends to viewing digital radiographs. Monitors that present good quality images should be used and the image quality should be checked. Some of the key areas to be considered when selecting or buying a flat panel monitor for dental radiology purposes are given below.3 As with many film-based modalities, dental radiography is making the switch from conventional film to digital. It should be remembered that dental film that has been properly exposed and developed, and viewed on an adequately maintained illuminator under reduced ambient light will still produce a quality image that is permanent. A dentist who is considering the move from film-based to digital imaging needs to consider radiation dose, infection control, the type of image receptor, digital image manipulation, image storage and mode of display.

Computer monitors, and even handheld devices such as personal digital assistants (PDAs), smartphones, and tablet devices can be used to view a variety of images.

However, until further research is carried out on the use of these handheld devices

12

for image display in dental radiology and appropriate guidelines from professional bodies are developed, it may be prudent to view these images on the type of monitors one would normally encounter in the dental practice, which are usually positioned to facilitate suitable ergonomics. The greyscale values that are displayed by the monitor help to evaluate the type of tissues being examined, to assist in determining the origin of lesions and to look for density changes within the displayed structures, especially bone, so it is important that the monitor provides a good overall presentation of greyscale. The use of colour in dental imaging has also increased significantly in the past few years, and both extra-oral and intra-oral photography is now an increasing part of dental record-keeping and so accurate colour display is also important. Soft copy dental images may also be shared among practitioners as part of the patient’s care pathway in a number of disciplines and particularly in the area of implant planning and treatment, so there is a need to select monitors that are appropriate for viewing these images and an increasing expectation that quality assurance is undertaken on these display devices.

Monitor specifications Brightness is a subjective quality, a perception that humans express in terms of ‘dark’, ‘dim’, ‘bright’ or something intermediate. Flat panel monitors are usually liquid crystal display (LCD) or light emitting diodes (LED). LCDs use cold cathode fluorescent lamps (CCFLs) to provide backlighting, whereas LED monitors use an array of smaller usually more efficient light emitting diodes to illuminate the screen so that one can perceive the level of brightness. Whatever the type of flat panel monitor, the fundamental function is to emit a quanta of light (luminance) which is detected by the retina and processed by the visual cortex. Luminance can be measured with a photometer and can be expressed in absolute numbers such as candela per metre squared (cd/m2).

When one sees a maximum luminance of the order of 250-300 cd/m2 quoted in the list of specifications for a particular monitor, this value would produce an acceptable brightness for assessing and interpreting dental radiographs.

Practically all flat panel monitors used routinely in dentistry are colour monitors and are connected to a display controller (graphics card, video card) which is a piece of electronic circuitry inside the computer that creates the picture on a monitor.

It is recommended for viewing and manipulating Cone Beam Computed Tomography (CBCT) images that the monitor is connected to a dedicated graphics card. Flat panel monitors transmit light, and the brightness levels of the red (R), green (G) and blue (B) subpixel components of the monitor screen is what determines the

13

colour and appearance of a presented image. However, for a greyscale image these subpixels transmit light at brightness levels R = G = B = 0 (black) and R = G = B = 255 (white), meaning that a colour monitor will display a radiographic image in 256 shades of grey. In the list of specifications it would state that these monitors can display over 16 million colours often referred to as true colour or 32 bit colour, which translates into 256 shades of grey or 8 bit greyscale when displaying dental radiographs.

Finally ambient light or diffuse light can come from many directions in the dental surgery as indirect light sources, it will add to the minimum luminance that the monitor can display and the contribution from this bright surrounding light could effectively wash out the display of some structures in the dark area of a displayed image, therefore it is good practice to view the displayed image on the monitor in subdued lighting.

The future will see medical grade monitor manufacturers understanding the imaging needs of the dental profession by providing monitors with screen panels that can offer 12 and 16 bit greyscale precision for the display of dental images. At the present time 10 bit precision is already the norm for the screen panels of most of these medical grade monitors available for dental use. An agreed standard for the high quality visualisation of colour medical images will be established. Dedicated monitors for dental radiology will come with an associated display controller that will allow 10 bit or higher input of data to allow the display of more of the data that has been captured during the acquisition stage and possibly more structures within the image could be visualised. In CBCT imaging these display controllers will integrate with the reconstruction software through their own graphics processor units to allow parallel processing of the captured image data and produce much clearer and sharper segmented aspects of the 3D rendered views resulting in crisper and anatomically accurate dento-alveolar structures. Flat panel monitors have a space saving design, they are light, consume low levels of electricity and have a low heat production. With regular quality assurance checks by staff within the dental practice, one would expect monitors used for dental radiology to display optimal and consistent images. However, dental practitioners should also consider patient safety and other quality factors along with luminance profile when selecting monitors for clinical practice.

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References 1.

Jacobs R et al. Cone beam computed tomography in implant dentistry:

recommendations for clinical use. BMC Oral Health 2018; 18: 88.

2.

Jayachandran S. Digital imaging in dentistry: a review.

Contemp Clin Dent 2017; 8: 193-194.

3.

McIlgorm D. Viewing your digital radiographs: which monitor is best?

Br Dent J 220: 393-397.

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2018 Digital Dentistry E-Publication – Editorial

Why refer to a specialist dental imaging centre?

CBCT scanning is widely being used by dentists across the UK to provide valuable 3D imaging to help in the accurate diagnosis, treatment planning and evaluation of many conditions. Many dental professionals believe it is best for their patients to undergo a CBCT scan in-house and so invest in costly equipment and training to provide this. However, many are now finding that referring their patients to a specialist dental imaging centre is by far the best option for both patients and practice. Whether you refer or purchase a CBCT scanner, there are factors which should be considered. For instance, scanning equipment can often cost in excess of £100k and can quickly become dated. Compare this to a fee of just £105* per scan per patient; no large initial outlay or loan is required. There are also other additional costs. A CBCT scanner requires its own dedicated room, which can be difficult for practices with limited space. In addition to this, a maintenance contract is required and annual checks. When making your decision, the expertise and support for dentists is particularly important when dealing with more complex cases. Within a specialised dental imaging setting, highly qualified diagnostic radiographers with hospital experience take all x-ray images, provide support to the referring dental team and keep up-to-date with the latest CBCT and x-ray technology.

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Chapter 2

Advances in digital partial dentures

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By Ashley Byrne

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It is a well known fact that crown and bridge restorative work can be manufactured using a nearly 100% digital process through computer aided design and computer aided manufacture (CAD/CAM). Yet most digital work flow in prosthetics, or dentures, is still in its infancy of development and actual usage in the lab. There have been some early developments of using CAD/CAM to design and mill or print dentures but the technology is still in its infancy. Whilst a few milling and printing companies have developed materials for full denture designs and construction, the technology has yet to be adopted into the mainstream. There is one area of prosthetics that has seen huge development has been the removable partial denture or RPD. This technology has now started to hit the mainstream with many labs now with several thousand successful cases behind them.

The growth of the intra oral scanner (IOS) in the dental market has been led by orthodontics and restorative crown and bridge but the RPD and denture market has encountered a lot of problems with the usage of IOS. The accuracy for a denture is in question because a compressive impression cannot be taken. However, for a partial denture that is tooth-borne, an RPD digital intra oral scan is perfectly acceptable.

Whilst the digital impression is possible, one of the primary problems with making RPDs when IOS is used has been the lack of digital options to manufacture actual RPD frameworks. In crown and bridge we can mill restorations in zirconia, metals and hybrid materials like polymers but it simply is not cost effective to mill partial dentures in those materials. The wastage and time taken in milling makes conventional casting from the lost wax technique still far more cost effective. The alternative has been to wax on a 3D printed model however that has its own issues around accuracy and reliability. In an ideal digital work flow we would be avoiding the waxing and cast an RPD from a digital scan. The ideal would be the ability to digitally design and digitally produce the RPD framework with minimal analog steps like waxing and casting.

Software specifically designed for RPDs has been around for many years now.

Companies like 3Shape, Exocad and Dental Wings have given labs plenty of options

18

for RPD design and the costs have become a lot more affordable. These CAD softwares allow labs to take an intra oral scan or using an ‘ab’ based light and laser scanner an .stl scan file of a stone cast and design an RPD. This software allows us to make all aspects of a conventional chrome partial denture from primary and secondary connectors, spaces, arms, classification designs and surface finishes.

The benefits of a digital design are ever increasing as technology improves and offers the technician an increased portfolio of designs and treatment plans. We are even seeing mainstream attachments appearing in the software which allows us to reduce the costs of complex designs even greater.

Communication issues One of the areas that has always been a struggle with RPD design and manufacture has been communicating that design between the patient, clinician and laboratory.

Paper designs can easily be misunderstood and once a frame has been cast it is usually a complete and costly remake if the RPD design is not correct. Using digital technology now allows communication in RPD design between the clinician and technician in a way that has never been easier. The design software allows the technician to send a 3D PDF or file that can be zoomed in on, parts hidden or made translucent to allow a complete and unrestricted view of the framework. All aspects can be checked from the file from blockout depth to main frame design. If small adjustments are needed these can be done quickly and easily so the risk of a poorly designed framework is eliminated. Advances in the in-lab and chair side 3D printers take the communication opportunities even further by allowing clinicians and labs to print a cost effective framework try in, in a resin based material. This ‘chrome frame dummy’ resin try in can be used to assess retentive aspects, position of the clasps for aesthetics and of course, the general fit of the partial denture. A lot of issues in complicated designs can be eliminated at this stage before the expense of manufacturing the chrome frame.

Design softwares are constantly improving. Nearly all types of partial denture can now be designed in CAD software (Figures 1-6). As the images show, the scan or cast can be digitally blocked out to whatever angle, thickness or dimensions are chosen. By rotating the mouth on the screen, we can easily try different options for blocking out combined with paths of insertion. The normal process of waxing this stage can take a good technician a large portion of time, this stage digitally can be done in less than a minute saving lots of precious technician resource. These virtually blocked out casts can then be 3D printed, but in most cases that is not needed as

19

Figure 1.

Figure 2.

Figure 3.

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Figure 4.

Figure 5.

Figure 6.

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the block out is purely for the design stage. From this block out the software can calculate the clasp and how deep we want the clasp to engage. The flexibility of this function is incredibly powerful because we have complete and unique control over the resistance and retention of the partial denture. Once the clasps have been positioned and all the primary and secondary connectors linked, we can then look at meshes and designs to ensure we get a great bond to the acrylic.

Once the design is approved and the clinician, patient and lab are happy, then we can look at how we turn this partial denture design into an actual restoration.

As mentioned before, it is simply not cost effective to mill a framework in metal, nor is it accurate enough, or a true digital workflow to wax onto a 3D model and then conventionally add clasps. It does work but not particularly well. The main area of CoCr partial denture construction now lies with 3D printing of the metals, also called selective laser melting (SLM). This relatively new form of additive manufacturing involves a machine that deposits a tiny layer of metal dust before a laser melts it.

Another layer of dust is then rolled on top and the process is repeated. Each layer fuses to the next and over time a solid metal shape is manufactured. This technology now allows us to accurately produce a whole partial denture to the same standard as conventional casting, but with the advantage of it being digital and not designed from a model, just a scan. The ‘printed’ chromes can then be trimmed and polished in machines to produce stunning frames. These are then placed on a 3D printed model and processed conventionally. A set up is made manually and then the wax is boiled off and the acrylic injection molded.

This technology is also allowing us to embrace new materials based around polymer science. These semi rigid frames are metal free and offer a uniquely different approach for partial denture design which was never possible before. Whilst this material has its limitations, it is great to see new materials now being tried and tested in removable denture dental technology.

The last main advantage of this digital work flow is the reproducibility. As the partial denture was made from an .stl file, if the denture is broken, lost or chewed by the dog, we can print a new chrome and model, and remake a near perfect replica both quickly and cost effectively. In an age where dementia and late life memory loss is increasingly common, for families managing illness or for care homes, it is of great interest that we can manufacture spare devices at almost the click of a button.

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The technology is still not perfect but it is not far off. The future of this area of the industry offers us many great opportunities. In an industry that is growing whilst lab numbers are dropping, time saving and communication has never been more important. This article shows the advantages of using this technique and how it can benefit patient, clinician and technician. The improvement in designs and materials is now also offering patients a far better selection of treatment options but also improving the standard of those restorative options. As the materials and technology improves, it will only be a matter of time before we are also milling or printing the teeth set up which would allow a near perfectly RPD digital work flow.

The future certainly looks very exciting for the world of removable partial dentures and prosthetics as a whole.

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Chapter 3

How digital dental software aids the practitioner

By David Westgarth

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Charles Darwin’s Theory of Evolution, when first published, was considered truly ground-breaking. It drew criticism and scepticism in equal measure, yet it prompted a clear and definitive structure for future discussions about how man evolved.

Visually, it remains one of the most striking images. You will struggle to find someone who cannot explain what it is and where it originates. And that is the very thing about evolution – it’s always easy to look back on where you’ve come from and recognise the significant changes. Dental practitioners can relate to that. Patients can relate from a product perspective, but there is one area both can relate to; the vast development in digital dental software.

Take Google, for example. A quick search of ‘digital developments in dentistry’ reveals how influential the topic has become. On my particular search, six of the top suggestions relate to digital dentistry at conferences. It’s a huge focus, but how exactly does digital dentistry aid the dental practitioner? My own hypothesis is that there is every chance that the profession could be becoming too reliant upon technology. Yes, it could be creating better dentists, yet alternatively it could simply be creating better operators of technology.1 The facts – and the figures that make the difference for practice owners and practitioners – run against that particular train of thought. There is no getting away from the fact costs are higher and errors more frequent when a human element is incorporated into the workflow. Dentists, after all are only human. That’s not to say pre-digital dental software dentists were extracting the wrong teeth left, right and centre, far from it. What it did do – and this comment is only available with the benefit of hindsight – is to force practitioners into safe decisions. There were far fewer risky treatments carried out, simply because practitioners did not have software capable of helping them successfully complete. What software does achieve is taking the human element of emotion out of the case.

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As technology has become more sophisticated and less costly, areas where it was thought that only humans could fill are now being replaced by machinery.

Technology has improved everything from the laboratory to chairside milling, enabling the concept of ‘single day dentistry’ and enabling the dentist’s workflow to be more accurate and more efficient. No longer do patients have to wait weeks or months to have their dental work completed. As the name suggests, it can now be done in a single day.

But is it a new concept, or a bandwagon practitioners have to join to be able to satisfy patient demand? Digital technology was introduced and available within the profession 30 years ago, so it’s probably not a new concept. Early adopters embraced the advanced technology and introduced it to their patients. Computer Aided Design/Computer Aided Manufacturing – better known as CAD/CAM – has since advanced making it easier to implement in an established dental clinic. And time is something precious to this profession.

Besides the time and cost savings to your practice and to your patient, CAD/ CAM enables one single appointment from diagnosis to placing the restoration. It’s probably only in the last five or six years there have been more clinicians embracing the single day dentistry idea. If, as a practitioner, you want to offer the best and most efficient service available to patients, maximise your own time and still be able to deliver a quality offering to patients, embracing digital software is a necessity.

The problem with any new concept – particularly in a challenging economic environment – is having the confidence that it will be a success. After all, investment in the machines isn’t a decision to be made on a whim. It is those who can identify any equipment is an investment rather than an outlay that are the ‘forward thinkers’.

Any progressive forward-thinking practice is one able to offer patients the latest technology while at the same time increasing efficiency and profitability in order to increase patient numbers. Advanced technology – particularly equipment competing practices do not have – has the potential to spark interest from prospective patients. It stops becoming an expenditure and starts becoming an investment.

A wider picture This shift in attitude was brought into focus in the Association of Dental Dealers in Europe’s 2017 Survey on the European Dental Trade.2 The report shows in principle, Germany remains the market leader in the use and development of dental technology and software. Between 2011 and 2016, they led the way in:

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-

The number of new dental units installed

-

The number of new digital intra-oral scanners installed

-

The number of new surgery CAD/CAM milling units installed

-

The number of new CAD/CAM Systems installed.

In the UK, the same period of time revealed a slow but steady growth in those areas.

CAD/CAM related software and digital intra-oral scanners have seen increases post-economic crash – Britain sits third on the percentage list of dental practices using intra-oral scanners in Europe – a clear sign practitioners have started to see the investment value in high-ticket items to assist a primary reason behind the growth – the increasing complexity of the needs of the patient.

Often restorations can be quite complex, and technology reduces the lottery of whether the patient will need to return or not. Patients are living longer and keeping their natural teeth for longer, and the complexities of treating cases pre-digital era with digital workflows is a challenging prospect for any practitioner.

For this cohort, digital impressions prove more comfortable and efficient treatment than the analogue equivalent whilst giving the technician the opportunity to assess the preparation. Throughout all of this the patient is still seated and changes can be made. It can also aid those who aren’t massively comfortable with visits to the dentist. And that is the strength of the ‘digital era’. Every patient is different and you need to find unique solutions for each of them. You can’t use standard methods of measuring success as the parameters have changed exponentially. If you have an error margin of say 5mm, that doesn’t leave you a lot of room for manoeuvre. If you can see what you’re doing on a large monitor that is zoomed in, the threshold of accuracy becomes far greater than it ever has been.

Ten years ago if you lost a tooth a bridge would be the only fixed prosthodontic option on the table. Now that isn’t the case. Whereas previously it was necessary to partially destroy two neighbouring teeth to construct a bridge now, with the option of implants tooth tissue can be conserved. No-one wants to lose good teeth or tooth hard tissue. Levels of oral health have improved dramatically and people are keeping their natural teeth for longer and they’re living longer, so it’s no real surprise.

However as we know that the patients are living for longer, we’re still doing the same number of crowns and bridges. It’s just moving the pattern of treatment back a generation. In the future it’s entirely possible – with the aid and continuing development of software – treatments like crowns and bridges may become a thing of the past.

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Future proof?

Older people have more complex dentitions, and patients don’t like to be kept waiting. They don’t even like attending in many cases. It is a perfect storm that means speed is of the essence. But is the future workforce ready to cope with the demand?

There are two parts to this. Millennials have been brought up on the very best technology, and certainly aren’t afraid to use it. House phones and landlines are all but obsolete – the advent of mobile phones was the stage in evolution that killed them off in no small part due to millennials. So, from a usage perspective, the students of today are theoretically best-placed to take advantage of the boom in digital software. The second strand is the clinical aspect. Are they truly ready to perform some of the complex cases practitioners in five or 10 years’ time will encounter? There is a theory that the students of today aren’t fully equipped to deal with the needs of tomorrow. The Advancing Dentistry project mooted by HEE is only likely to result in a further de-skilling of the workforce. And with no new contract in sight, practitioners will be expected to do more with less. Given how much technology is changing, it’s going to be interesting to see how – or if – students can keep up.

Today, the digital revolution is changing the workflow and consequently changing operating procedures. In modern digital dentistry, the four ‘basic’ phases of treatment planning – image acquisition, data preparation/processing, the production, and the clinical application on patients – remains the biggest beneficiary of digital software. 3D printing is going to be absolutely huge – provided the financials make sense. Imagine if Google Glasses made their way into dentistry.

Imagine making a video of how to prepare a patient with visual instructions. If you can see in your glasses how to perform a procedure as you’re working on it, it could revolutionise dentistry. Video instruction through YouTube and webcasts are becoming a large source of clinical learning, and there is every chance that to keep with the times this will become embedded in how dentistry is taught at dental schools, how CPD will evolve and how we will learn. Like the move to online media for our news, traditional print media may be susceptible to the demand for what I want when I want it.

Over the next ten years as digital technologies become mainstay in the process of delivering cosmetic treatment, there is every chance that digital design software will grow to become central in the delivery and planning of every day dental procedures. It has the capacity to enhance diagnostic ability, improve multidisciplinary communication, provide medico-legal coverage for clinicians, and

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deliver information in a way that advances patient education. Ultimately, every patient is an individual so every smile is distinctly different. As dental professionals anything that can be done to embrace and recognise this development is a welcome one. Even if you don’t believe in the Theory of Evolution.

References 1.

Westgarth D. Technology: Friend or Foe? BDJ In Practice 2017; 30: 12-16.

2.

Association of Dental Dealers in Europe. 2017 Survey on the European Dental

Trade. 2017.

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Chapter 4

Digitally guided implant design and treatment

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Digital technology in dentistry although originally focussed on CAD/CAM procedures in restorative dentistry has broadened into many branches of oral care, none more so than in implants where it is represented in diagnosis, treatment planning, design and follow-up care. Here we survey the findings of recent research in implant dentistry with respect to digital technology.

Digital versus analogue for single implants Research to date suggests that the smaller the number of units scanned (upto four to five units/teeth) using intra-oral scanning for image generation and subsequent treatment, the more accurate the results. In a study by Mangano and Veronesi1 they compared single implants completed by either digital or conventional (analogue) procedures to assess outcomes one year after treatment.

All patients who were being treated in a dental centre over a two-year period (20142016) with a single implant were randomly assigned to receive either a monolithic zirconia crown, fabricated buy a digital workflow (test group), or a metal-ceramic crown, fabricated with an analogue workflow (control group). All patients were followed for 1 year after the fitting of the final crown. The outcomes were success, complications, peri-implant marginal bone loss (PIMBL), patient satisfaction, and time and cost of the treatment.

Fifty patients (22 males, 28 females; mean age 52.6¹13.4 years) were randomly assigned to one of the groups (25 per group). The digital group had intra-oral scans and computer assisted design (CAD) and computer assisted manufacturing (CAM) for the provisional and final restorations. Those in the analogue group followed a more conventional procedure with impression taking and occlusal registration and had their restorations created through plaster models, wax-ups and manual preparation of the temporaries and copings.

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Both workflows showed high success (92%) and low complication rate (8%). No significant differences were found in the mean peri-implant marginal bone loss between test (0.39±0.29mm) and control (0.54±0.32mm) groups. Patients preferred digital impressions which took half the time in the test group (20±5min) than in the control (50±7min) group. When calculating active working time, workflow in the test group was more time-efficient than in the control group, for provisional (70±15min versus 340±37min) and final crowns (29±9min versus 260±26min). The digital procedure presented lower costs than the analogue (€277.3 versus €392.2).

The authors therefore concluded that no significant clinical or radiographic differences were found between digital and analogue procedures; however, the digital workflow was preferred by patients and reduced active treatment time and costs.

Digital workflow scrutinised With the increasing move towards digital workflows has come various studies to measure their efficiency and advantages compared to conventional procedures.

The aim of a review of the literature on this topic undertaken by Joda and co workers2 was to compare fully digitalised workflows to conventional and/or mixed analogue-digital workflows for the treatment with tooth-borne or implant-supported fixed reconstructions. They carried out electronic and manual searches of databases up to September 2016 focusing on randomised controlled trials (RCT) investigating complete digital workflows in fixed prosthodontics. Results were focussed with regard to economics, aesthetics and patient-centred outcomes with or without follow-up or survival/success rate analysis as well as complication assessment of at least one year under function.

The systematic search identified 67 titles, 32 abstracts thereof were screened, and subsequently only three full-texts were included for data extraction, emphasising how young this field of research is. One study demonstrated that fully digitally produced dental crowns mandated the feasibility of the process itself; however, the marginal precision was lower for lithium disilicate restorations compared to conventional metal-ceramic and zirconium dioxide crowns. Another study showed that leucitereinforced glass ceramic crowns were aesthetically favoured by the patients (8/2 crowns) and clinicians (7/3 crowns). The third study investigated implant crowns. The complete digital workflow was more than twofold faster (75.3 min) in comparison to the mixed analogue-digital workflow (156.6 min). No RCTs could be found investigating multi-unit fixed dental prostheses (FDP).

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With such a low number of studies to date, scientifically proven recommendations for clinical routine cannot yet be given. Research with high-quality trials seems to be slower than the industrial progress of available digital applications. Future research with well-designed RCTs including follow-up observation is compellingly necessary in the field of complete digital processing.

Time-efficiency However, to further emphasise the growing positive attitude towards digital design for implants, another study by one of the same authors looked specifically at the time saving aspects of digital workflow.3 This prospective clinical study used a crossover design that included 20 study participants receiving single-tooth replacements in posterior sites. Each patient received a customised titanium abutment plus a CAD/ CAM zirconia suprastructure (for those in the test group, using digital workflow) and a standardised titanium abutment plus a porcelain-fused-to-metal crown (for those in the control group, using a conventional pathway). The start of the implant prosthetic treatment was established as the baseline. Time-efficiency analysis was defined as the primary outcome, and was measured for every single clinical and laboratory work step in minutes.

All crowns were provided within two clinical appointments, independent of the manufacturing process. The mean total production time, as the sum of clinical plus laboratory work steps, was significantly different. The mean ± standard deviation (SD) time was 185.4 ± 17.9 minutes for the digital workflow process and 223.0 ± 26.2 minutes for the conventional pathway. Therefore, digital processing for overall treatment was 16% faster. Detailed analysis for the clinical treatment revealed a significantly reduced mean ± SD chair time of 27.3 ± 3.4 minutes for the test group compared with 33.2 ± 4.9 minutes for the control group. Similar results were found for the mean laboratory work time, with a significant decrease of 158.1 ± 17.2 minutes for the test group vs 189.8 ± 25.3 minutes for the control group.

Digital frameworks tested Another experimental study compared the retention of implant-supported frameworks cast from wax patterns fabricated by three different methods.4 Thirty-six implant analogues connected to one-piece abutments were divided randomly into three groups according to the wax pattern fabrication method (n = 12).

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Computer-aided design/computer-aided manufacturing (CAD/CAM) milling machine, three-dimensional printer, and conventional technique were used for fabrication of waxing patterns. All laboratory procedures were performed by an expert-reliable technician to eliminate intra-operator bias. The wax patterns were cast, finished, and seated on related abutment analogues. The number of adjustment times was recorded and analysed, frameworks were cemented on the corresponding analogues with zinc phosphate cement and tensile resistance test was used to measure retention value.

The mean retentive values of 680.36 ± 21.93 N, 440.48 ± 85.98 N, and 407.23 ± 67.48 N were recorded for the CAD/CAM, rapid prototyping, and conventional groups, respectively. Statistical analysis revealed significant differences among the three groups with higher retention for the CAD/CAM group although no significant difference between the two other groups. However, the CAD/CAM group required significantly more adjustments. The conclusions was that CAD/CAM-fabricated wax patterns showed significantly higher retention for implant-supported cement-retained frameworks and that this could be a valuable help when there are limitations in the retention of single-unit implant restorations.

Scanning accuracy In order for the digital workflow to be accepted the initial stage of intra oral scanning (IOS) accuracy has to be good. In a systematic review the authors searched the literature for evidence on the accuracy of IOS compared with conventional techniques.5 Additionally, they aimed to identify the main factors influencing the accuracy outcomes. Electronic databases were searched in November 2016 using key words, inclusion and exclusion criteria. Publications in English language evaluating the accuracy outcomes of digital implant impressions were identified.

In total, 16 studies fulfilled the inclusion criteria: one in vivo and 15 in vitro studies.

The clinical study concluded that angular and distance errors were too large to be acceptable clinically. Less accurate findings were reported by several in vitro studies as well. However, all in vitro studies investigating the accuracy of newer generation IOS indicated equal or even better results compared with the conventional techniques. Data related to the influence of distance and angulation between implants, depth of placement, type of scanner, scanning strategy, characteristics of scanbody and reference scanner, operator experience, etc. were analysed and summarised. Linear deviations (means) of IOS used in in vitro studies ranged from 6 to 337 µm. Recent studies indicated small angle deviations (0.07-0.3°) with

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digital impressions. Some studies reported that digital implant impression accuracy was influenced by implant angulation, distance between the implants, implant placement depth and operator experience.

According to the results digital implant impressions offer a valid alternative to conventional impressions for single- and multi-unit implant-supported restorations.

Further in vivo studies are needed to substantiate the use of currently available IOS, identify factors potentially affecting accuracy and define clinical indications for specific type of IOS. Data on accuracy of digital records, as well as accuracy of printed or milled models for implant-supported restorations, are of high relevance and are still lacking.

Placement is key Good design, scanning accuracy and restoration manufacture are all essential elements of the digitally designed implant process but so too is the placement of the implants.

Research by Beretta et al.6 evaluated the in vivo accuracy of flapless, computeraided implant placement by comparing the three-dimensional (3D) position of planned and placed implants through an analysis of linear and angular deviations.

Implant position was virtually planned using 3D planning software based on the functional and aesthetic requirements of the final restorations. CAD/CAM technology was used to transfer the virtual plan to the surgical environment. The 3D position of the planned and placed implants, in terms of the linear deviations of the implant head and apex and the angular deviations of the implant axis, was compared by overlapping the pre- and postoperative computed tomography scans using dedicated software. The comparison of 14 implants showed a mean linear deviation of the implant head of 0.56 mm (standard deviation [SD], 0.23), a mean linear deviation of the implant apex of 0.64 mm (SD, 0.29), and a mean angular deviation of the long axis of 2.42° (SD, 1.02).

Discussing their results, the authors concluded that computer-aided flapless implant surgery seemed to provide several advantages to the clinicians as compared to the standard procedure; however, linear and angular deviations are to be expected.

Therefore, accurate presurgical planning taking into account anatomical limitations and prosthetic demands is mandatory to ensure a predictable treatment, without incurring possible intra- and postoperative complications.

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As ever, research into the application of new techniques, equipment and materials fall somewhere behind the day-to-day use of them. However, to date, the published research seems to back the reported experience from clinicians that digital technology and its implementation in dental implantology is safe, effective, efficient and will doubtless increase and be refined into the future.

References 1.

Mangano F, Veronesi G. Digital versus analogue procedures for the prosthetic

restoration of single implants: a randomized controlled trial with 1 year of

follow-up. Biomed Res Int 2018; 2018: 5325032.

2.

Joda T, Zarone F, Ferrari M. The complete digital workflow in fixed

prosthodontics: a systematic review. BMC Oral Health 2017; 17: 124.

3.

Joda T, Brägger U. Time-efficiency analysis comparing digital and

conventional workflows for implant crowns: a prospective clinical crossover

trial. Int J Oral Maxillofac Implants 2015; 30: 1047-53.

4.

Alikhasi M et al. Digital versus conventional techniques for pattern fabrication

of implant-supported frameworks. Eur J Dent 2018; 12: 71-76.

5.

Rutkunas V et al. Accuracy of digital implant impressions with intraoral

scanners. A systematic review. Eur J Oral Implantol 2017; 10 Suppl 1: 101-120.

6.

Beretta M, Paolo Poli P, Maiorana C. Accuracy of computer-aided template-

guided oral implant placement: a prospective clinical study. J Periodontal

Implant Sci 2014; 44: 184-193.

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Chapter 5

Digital impressions – the ultimate overview?

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Taking impressions of teeth and the oral cavity has been a fundamental activity in dentistry for centuries and little has changed … until now. Digital impressions potentially sweep away generations of techniques and materials. We investigate their progress and future prospects.

Digital impressions, essentially electronically captured images, are created using intraoral scanners (IOS). These are similar to other three-dimensional (3D) scanners in that they project a light source which is usually a laser, but more recently structured light onto the object to be scanned with the resultant image captured by sensors which then process it by scanning software to generate what are called point clouds. These point clouds are then triangulated by the same software, creating a 3D surface model (mesh).

In the case of dentistry the light source is projected onto the dental arches, including prepared teeth and implant scanbodies (i.e. cylinders screwed on the implants, used for transferring the 3D implant position) and dentogingival tissues. The surface images that are created can then be used as ‘virtual’ alternatives to traditional plaster or stone cast models to craft restorations and prostheses. So what are the advantages of this new technology and are there any disadvantages?

Advantages As one might expect with any new technology the pluses are based around convenience and ease of use, the negatives around costs, reliability and training.

The advantages can be listed under the following broad headings: •

Greater patient comfort and convenience

•

Practice efficiency

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•

Simplified clinical procedures

•

Efficiencies around the absence of plaster casts

•

Better communication with the dental technician and with patients.

Greater patient comfort and convenience Patients have never been very enthusiastic about having impressions taken with conventional trays and materials. Trays, even when custom made as special trays, are often bulky and uncomfortable and the principle of any physical impression material is that it is inserted in a fluid state and then left in situ to set. Some patients have problems with gagging, especially for upper impressions, and the inevitable risk of messy materials as well as taste mean that it has never been a particularly favoured experience.

Digital scanning eliminates almost all these unpleasant experiences and patients report a much greater preference for the technique as even the scanning handpiece is far from bulky or intrusive.

Practice efficiency It is claimed that there is time saving with optical scanning with a full arch being captured in about three minutes. There is probably not a great time saving compared to physical impression taking but there are certainly efficiencies in not having to wrap and prepare impressions for transportation to the laboratory, and not having to pour models in plaster or stone subsequently. For practices with equipment to design and manufacture chairside restorations, the files captured during optical impressions can be imported into computer-assisted design (CAD) software; once the restoration design is completed, the files can be transferred to computer-assisted manufacturing (CAM) software and put into the milling machine. The restorations formed, which can be in a variety of materials, can then be individualised and made ready for clinical application.

Simplified clinical procedures The clinician has the advantage of being able to repeat some or all of the scan according to judgement if unsatisfied about any part of it, without the need to re-mix impression material and put the patient through further potential discomfort. Digital software can also identify possible undercuts or other problem areas before the restoration is manufactured or an attempted fit.

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Efficiencies around the absence of plaster casts Not only are there direct time and cost savings on consumables, there is no longer the need to provide costly storage of models, particularly in orthodontics or the problem of appropriate disposal, which can be a specific requirement for some local authorities due to the gypsum component. An added benefit is also that digital impressions can be sent by email and stored in computer files and systems with ease, and safe from the danger of dropping and damage during transit.

Better communication Digital impressions allow the clinician and dental technician to assess the quality of the impression in real-time so that immediately after the scan has been performed the dentist can email it to the laboratory, and the technician can check it for accuracy. In the event that there is any question about its quality the dentist can immediately make another one without any loss of time and without having to recall the patient for a second appointment. This certainly simplifies and strengthens the relationship and the communication between the dentist and technician.

There are advantages for patient communication too, as they are often intrigued by the ‘new’ technology which allows them to see more clearly what is being planned and undertaken. This can have benefits in terms of greater motivation for better oral health and improved understanding of procedures leading to less likelihood of complains or legal claims. Such technology is also very good for promoting the practice in terms of patients’ word of mouth recommendations and for marketing purposes.

Disadvantages As indicted above, there are some disadvantages, such as training, cost of equipment and, as yet, some doubts about accuracy. The expectation is that dentists with an interest in and ability with technology (perhaps younger dentists) will take to digital modes more willingly, quickly and easily than less enthusiastic colleagues, or perhaps more mature ones. Either way there is a learning process in both technique in the mouth and familiarity with the software and this has to be considered in terms of cost and initial learning time.

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The cost of the equipment is also a major consideration, although the efficiencies and convenience of the systems have to be taken into account balancing capital outlay with long-term savings as well as patient satisfaction and team efficiency.

Two of the most frequent problems currently encountered with IOS are the difficulty in detecting deep marginal lines on prepared teeth and the presence of bleeding.

Unlike conventional impression materials, light cannot physically detach the gum tissue from the tooth surface and therefore cannot register ‘non-visible’ areas. Similar problems can also occur in the event of bleeding, as blood may obscure margins.

Despite this, with the proper attention and speed (the gingival sulcus tends to close immediately after the retraction cord is removed) and the appropriate strategies for highlighting the preparation line (insertion of a single or double retraction cord), and avoiding bleeding (excellent oral hygiene and provisionals with correct emergency profile), it is possible for the clinician to detect a good optical impression even in difficult contexts.1

The question of accuracy To date the literature seems to suggest that the accuracy of optical impressions is clinically satisfactory and similar to that of conventional impressions in the case of single-tooth restoration and fixed partial prostheses of up to 4–5 elements. However, optical impressions do not appear to have the same accuracy as conventional impressions in the case of long-span restorations such as partial fixed prostheses with more than 5 elements or full-arch prostheses on natural teeth or implants. So far, the errors generated during intraoral scanning of the entire dental arch mean that it does not appear compatible with the fabrication of long-span restorations, for which conventional impressions are still indicated.

However, the latest-generation scanners are characterised by very low errors in full-arch impressions,2 and in this sense the data in the literature must be interpreted critically, as preparing and publishing a scientific article generally takes time, whereas manufacturers release new powerful software frequently.

Clinical uses to date Intra oral scanners are of great use and are being applied in various fields of dentistry, for diagnosis and for fabricating restorations or custom devices in prostheses, surgery and orthodontics. In restorative dentistry IOS are used to make impressions of preparations of natural teeth for fabricating a wide range of prosthetic

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restorations: resin inlays/onlays, zirconia copings, single crowns in lithium disilicate, zirconia, metal-ceramic and all-ceramic as well as frameworks and fixed partial dentures. Several studies and literature reviews have shown that the marginal gap of ceramic single crowns made from intraoral scans is clinically acceptable and similar to that in crowns produced from conventional impressions. The same considerations can be extended to short-span restorations such as fixed partial dentures of up to five elements, as noted above.

In prosthodontics, IOS can be successfully used to capture the 3D position of dental implants and to fabricate implant-supported restorations. The 3D position of the implants captured with the IOS is sent to the CAD software, where the scanbodies are coupled with an implant library, and the desired prosthetic restorations can be drawn within minutes; this restoration then can be physically realised by milling through a powerful CAM machine using ceramic materials. At present, implantsupported single crowns, bridges and bars can be successfully fabricated from optical impressions. Similar to the situation with natural teeth, the only apparent limitation to the use of IOS in implant prosthodontics is that of long-span restorations on multiple implants, such as long-span bridges and fixed full arches supported by more than four implants. To date, only a few studies have addressed the use of IOS for fabricating partial and complete removable dentures. In the latter case the main issue is the lack of reference points and the impossibility of registering soft tissue dynamics. However, IOS can be successfully used for digital smile design applications, post and core fabrication and for fabricating obturators, in complex cases.

Digital impression taking is also a very useful tool in orthodontics for diagnosis and treatment planning and can be used as a starting point for the realisation of a whole series of customised orthodontic devices including aligners. In the future it is likely that almost all orthodontic appliances will be designed from an intraoral scan to make them entirely ‘custom’ and adapted to the patient’s specific clinical needs.

Combining digital technologies Dentogingival model scanning can be superimposed onto files from cone beam computed tomography (CBCT) using specific software to create a virtual model of the patient. This is then used for planning the positioning of implants and to draw one or more surgical stents useful for placing the fixtures in a guided manner. The use of IOS in this context has superseded the previous technique of double scanning with

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CBCT only, which was based on radiologic scans of the patient and of the patients’ plaster models. In fact, the scanning resolution of CBCT is lower than that of IOS; the use of IOS therefore allows the detection of all details of the occlusal surfaces with greater accuracy. This can make the difference in, for example, the preparation of tooth-supported surgical templates. However, care should be taken, as the use of IOS in guided surgery is only in its infancy.

References 1.

Mangano F et al. Intraoral scanners in dentistry: a review of the current

literature. BMC Oral Health 2017; 17: 149.

2.

Imburgia M et al. Accuracy of four intraoral scanners in oral implantology: a

comparative in vitro study. BMC Oral Health 2017; 17: 92.

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Chapter 6

3D printing and digital dentistry

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3D printing has a certain science fiction sense of being rather mystical, possibly outside the normal run of our daily existence and something of a puzzle as to how it works. However, it is making steady and gradual progress in dentistry and is likely to become an increasing part of the dental landscape.

3D printing is an additive manufacturing process which uses laying of materials to gradually build and create in the finished form an object generated from data held by a computer. It was first demonstrated in 1983 by Charles Hull who printed a three-dimensional object using the technique of stereolithography, as well as the first program for virtualisation. The technology received increased attention in fields such as architecture due to the increased potential in the direct construction of parts, aeronautics because of the ease of making various small parts used in spacecraft construction, and technical subassemblies used in telecommunications domain. Their ability to incorporate immense precision drew the attention of specialists in medicine who started to apply it the 1990s. 3D modelling technologies and techniques are developing due to the increased popularity of 3D printers. Among additive manufacturing techniques, dimensional printing is a relatively new technique that offers the possibility to produce a variety of geometrical pieces using various materials in the form of powder and binder.

In prosthetic treatments, computerised scanning systems and 3D printing systems are gradually finding applications that are replacing traditional techniques for producing prostheses. The applications used in the development of 3D printed parts outside dentistry use mostly technology for manufacturing various mechanical components and employ special computer programs that contain libraries of standardised objects needed to achieve design pieces. Dental work patterns however, where every patient has an individual need can be imported by scanning various prosthetic fields with intra-oral scanners or using computerised imaging results such as cone beam computed tomography.

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Dentistry is familiar with the CAD/CAM technique and the move toward these and away from traditional dental laboratories has been afoot since the 1990s at various speeds.

These are subtractive manufacturing, more usually described as ‘milling’ which involves the removal of material to form an object. CAD CAM for the milling of crown copings and bridge frameworks is now synonymous with modern dental technology. Modern dentistry has a familiarity with materials designed to work with CAD CAM and to substitute for the more traditional precious metal casting alloys, which have been subject to exponential price increases in recent years. This use of technology facilitates the utilisation of materials which would otherwise be hard to work with, and eliminates labour intensive artisanal production techniques, allowing dental technicians to focus their manual skills on more creative aspects of the manufacturing process, for example the aesthetic layering of porcelain.

While the advent of multi-axis CAD CAM milling processes has allowed the individualisation of restorations to an extent, the process is slow and wasteful as the material is milled from an intact block, and accuracy is limited by the complexity of the object, the size of the tooling, and the properties of the material. 3D printing, however, comes into its own for the accurate one-off fabrication of complex structures in a variety of materials with properties that are highly desirable in dentistry and in surgery.

3D printing technologies used in dentistry 3D printing technologies used in dentistry include the following: Selective laser melting Making metallic frameworks by selective laser melting technology is one of the most promising directions for solving various problems encountered during casting alloys, a process central to creating restorations incorporating metallic components. Selective laser melting is a technique of layer by layer addition that generates 3D pieces by strengthening selective and successive layers of powder material, one above the other, using heat generated by a computer-controlled laser radiation.

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Stereolithography The most popular rapid prototyping technology is stereolithography, the device invented by Charles Hull and was the first commercially available printer for rapid prototyping. The principle is based on a photosensitive monomer resin, which forms a polymer and solidifies when exposed to ultraviolet (UV) light. The reaction created by UV light takes place only on the surface of the material.

Fuse deposition modelling The 3D printer uses a computer-aided model or scan information, for example from an intra-oral scan or scan of a conventional stone or plaster model, which it extrudes and deposits as melted thermoplastic polycarbonate. This it does in a layered fashion to build objects from bottom to top. The layers of melted plastic instantly combine with each other, thus making very complex parts that are easy to produce.

The resulting aspect of the finished object can be used in combination with several materials such as acrylic or wax.

Digital light processing In this technique, a projector light source cures liquid resin layer by layer. The object is constructed on an elevated platform and the layers are created upside down. The polymer is layered pending the object is constructed, and the residual liquid polymer is drained off.

Photopolymer jetting (PPJ) This technology uses light cured resin materials and print heads rather like those found in an inkjet printer (but considerably more costly), to lay down layers of photopolymer which are light cured with each pass of the print head. The technology may use a stationary platform and dynamic print head or a stationary print head and dynamic platform. A support structure is laid down in a friable support material. A variety of materials may be printed including resins and waxes for casting, as well as some silicone-like rubber materials. Complex geometry and very fine detail is possible as little as 16 microns resolution.

The drawback is that the equipment, and materials are costly to purchase and run, and the support materials can be tenacious and rather unpleasant to remove. They are useful for printing dental or anatomical study models, but these are expensive

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when produced in this way. Implant drill guides may be quickly and cheaply produced with this technology as they are less bulky. A particular advantage of this technology is that the use of multiple print heads allows simultaneous printing with different materials, and graduated mixtures of materials, makes it possible to vary the properties of the printed object, which may for example have flexible and rigid parts, e.g. for the production of indirect orthodontic bracket splints.

Powder binder printers (PBP) This apparatus uses a modified inkjet head to print using, what is essentially, liquid droplets to infiltrate a layer of powder, layer by layer. Typically a pigmented liquid, which is mostly water, is used to print onto the powder, which is mostly plaster of Paris.

Again, a model is built up in layers as the powder bed drops incrementally, and a new fine layer of powder is swept over the surface. The model is supported by uninfiltrated powder, and so no support material is required. Post-processing to infiltrate the delicate printed model with a cyanoacrylate or epoxy resin will improve strength and surface hardness.

The resulting models are useful as study models or visual prototypes, but accuracy is limited and the models are rather fragile despite the post-processing. A particular excitement of this technology lies in its ability to print models in full colour; from a surgical perspective the drawback is that the models may not be sterilised or directly manipulated at operation.

Accuracy is inadequate for prosthodontic applications. The machines and materials are lower cost, but still not inexpensive. As the material is mostly plaster of Paris, there is some compatibility with having the apparatus situated in a dental laboratory plaster room.

3D printing uses in dentistry Oral surgery The rapid prototyping method can be used to create anatomical models which can be used for surgical planning and simulation. Such methods allow the replication of anatomical sites including three-dimensional physical models of the skull or other structures that allow the surgeon to obtain an overview of complex structures prior to surgery. Further, through software, the migration from a visual environment to one that allows both visual and touch interactions has introduced a new experience

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called ‘touch to comprehend’. 3D printing techniques can be used to make surgical guides and creating various shapes to augment bone defects. These also have an important role as learning modules by creating mandibles and jaws and bones that can be easily used by students.

Implantology The value and widespread use of dental implants has rapidly evolved in recent decades. Studies in the field of oral implantology have led to predictable restorative options both for patients that are partially or totally edentulous. In correct positioning of implants has the effect of decreasing predictability of the implant-supported prosthesis and so the use of 3D printing technology has gained popularity through the introduction of guidelines for the surgical procedure of inserting implants. 3D printers can print bone tissue tailored to the requirements of the patient, and can act as biomimetic scaffolds for bone cell enhancement and tissue growth and differentiation. In bone regeneration procedures, novel 3D printed alginate-peptide hybrid scaffolds can also be used. Studies indicate that the alginate-based scaffolds provide a stable environment for the growth of stem cells. Composite powders that can be printed into scaffolds such as calcium phosphate (CaP) can be mixed with a 3D printing (3DP) powder based on calcium sulphate (CaSO4), and the scaffolds can also be used as bone augmentation material.

3D printing may be harnessed for the fabrication of metal structures either indirectly by printing in burn-out resins or waxes for a lost-wax process, or directly in metals or metal alloys. The advantage of printing in resin/wax and then using a traditional casting approach is that there is much less post-processing involved than in the direct 3D printing of metals; casting alloys and facilities are also familiar and widely available. Printing directly in metals requires the use of more costly technologies which have their own very specific health and safety requirements, and demand a great deal of post-processing before components may be ready for use.

Maxillofacial prosthesis Obturators and prostheses required to replace maxillofacial defects caused by trauma or cancer surgery can also be produced by 3D printing. When trying to restore these missing tissues with prosthetic materials, the prosthesis can be customised for a unique role in the complex process of restoration and rehabilitation.

When defects are unilateral, the contralateral side can be scanned and the image suitably modified to restore the affected side by duplication. In this way ears, cartilage and blood cells have been created to date.

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Prosthodontics In the event that new and traditional techniques are to be combined, custom trays can be manufactured from computerised scans of impressions/models and printed, or can be created with readily available materials. There are two methods that are used for the development of study models for working in a virtual setting. The initial method includes scanning of the impression and transferring it into a program. The second method consists in taking the impression with a stock or semi-custom tray and pouring the model in stone. The stone prototype can be scanned or used directly in the manufacturing protocol. If needed, the study prototype can be replicated with duplicating hydrocolloid or printed, provided that a good quality scan is present.

Advantages and disadvantages of 3D printing 3D printing provides the possibility of high quality restorations with quick and easy fabrication by additive means as distinct from the subtractive means used by CAD/ CAM technology. The quality of these restorations has been demonstrated by several studies, although cost is still a major issue. The disadvantage of stereolithography and digital light processing is that they are available only with light curable liquid polymers and the support materials must be removed. Also, resin is messy and can cause skin irritation, and it could also cause inflammation by contact and inhalation.

In addition they present a limited shelf life and cannot be heat-sterilised, while being a high-cost technology. The disadvantage of selective laser melting is that it is an extremely costly technology and a slow process.

It seems highly likely that further research and technological advances will enable rapid prototyping to become a widely used method for 3D reconstructions in the dental laboratory. The extent to which such technological developments will act as substitutes or complementary processes to conventional treatment procedures is not yet clear but the disruption has begun in earnest.

Further reading Dawood A et al. 3D printing in dentistry. Br Dent J 2015; 219: 251-259.

Zahara C et al. Digital dentistry – 3D printing applications. J Interdisciplinary Med 2017; 2: 50-53.

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