3 d facial imaging/ dental implant courses by Indian dental academy

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INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacdemy.com www.indiandentalacademy.com

3 D FACIAL IMAGING THE CUTTING EDGE

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• Principles of 3d imaging • Over view of different techniques Stereophotogrammetry 3d laser scanning 3d cephalometry 3D facial morphometry Moire topography 3d cone beam ct scanning • Applications of 3d imaging www.indiandentalacademy.com

3D FACIAL IMAGING

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3 D DENTAL IMAGING

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PROCESS OF ACQUIRING 3 D IMAGE • In 3D medical imaging set of anatomical data is collected using diagnostic imaging equipment.

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PROCESS OF ACQUIRING 3 D IMAGE • Then processed by a computer and then displayed on a 2D monitor to give an illusion of depth.

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PROCESS OF ACQUIRING 3 D IMAGE • Depth perception causes the image to appear in 3D.

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Applications of 3D imaging • Pre post orthodontic assessment of dento-skeletal and facial relationships.

• Auditing orthodontic outcomes in regard to soft and hard tissue.

• 3D treatment planning • 3D soft and hard tissue simulation • 3D customized arch wires • Archiving 3D facial,skeletal and dental planning for in treatment records.

• Research and medico legal purpose are also benefits of 3D imaging. www.indiandentalacademy.com

Historical background • Singh and Savara ( angle orthodontist 1966) 3D analysis of maxillary growth changes in girls. • Thalmann and degan ( 1944) reported the use of stereophotogrammetry.

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PRINCIPLES

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STEPS IN 3D IMAGING

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MODELLING

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TEXTURE MAPPING

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Shading and lighting

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RENDERING

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APPROACHES TO 3D IMAGING • Udupa and Herman ( 3d imaging in medicine 1991).

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SLICE IMAGING

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VOLUME IMAGING

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PROJECTIVE IMAGING

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MEASURING SCANNED OBJECTS • Orthogonal measurement

• Measurement by triangulation

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ORTHOGONAL MEASUREMENT Y

Z X

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MEASUREMENT BY TRIANGULATION

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VARIOUS TECHNIQUES • • • • • •

3D Cephalometry 3D CT scanning 3D laser scanning Moire topography Structured light technique Stereophotogrammetry

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3D CEPHALOMETRY • Drawbacks – Time consuming – Exposes the patients to radiation – Does not define soft tissue and there are difficulty in relating accurately the same landmarks in two radiographs ,especially in biplanar technique.

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3D LASER SCANNING Advantages – Less invasive technique for capturing face for planning or for evaluation outcomes of treatment.

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Disadvantages – - slowness of method, making distortion of scanned image likely.

- safety issues of exposing eyes to laser beam, especially in growing children.

- inability to capture soft tissue texture, which results in difficulties in identification of landmarks that are dependant of surface color. www.indiandentalacademy.com

Moire topography • Defines 3D information based on the contour fringes and fringe intervals.

• Difficulties are encountered if the surface has sharp features.

• Care to be taken about positioning of the head.

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• Motoyoshi et al ( AJO 1992) described the system and concluded that it does not capture facial texture and subsequent landmark identification is difficult.

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STRUCTURED LIGHT TECHNIQUE • Light is used to illuminate the scene and only one image is required. • The position of the illuminated points in the captured image compared to their position on the light projection plane provides the information to extract the 3D co-ordinates of the imaged object.

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DRAWBACKS • To obtain high density image the face needs to be illuminated several times with light.this is time consuming and may alter the position of the head. • Also the camera does not provide a 1800 ear to ear facial model.

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• Techaletpaisarn and Kuroda (Int J Adult Orthod Orthog surg 1998) Used two Lcd projectors and Ccd ,and computer to produce a 3D image.

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• Curry et al ( seminar in orthodontics 2001) their system consists of 2 cameras and a projector. • Texture mapping

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STEREOPHOTOGRAMMETRY • Two cameras configured as a stereo pair are used to recover 3D distances of features on the surface of face by triangulation.

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• Uses a portable stereometric camera along with a plotting instrument . • Recent advances have enabled conversion of simple photographs into 3D images.

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• Ras et al ( journal of dentistry 1996 ) demonstrated a stereophotogrametric system that gives 3D co ordinates of any chosen facial landmarks that can be measured • Consists of 2 synchronized semi metric cameras mounted on a frame with a difference of 50 cm and a position convergently with an angle of 15 degrees. www.indiandentalacademy.com

C3D IMAGING SYSTEM • This is based on use of special digital cameras and with a special textured illumination ,with a capture time of 50 milli seconds and is sufficiently cost effective to be used in daily practice.

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• It captures the natural surface appearance of patients skin and drapes this texture on the captured 3D model of the face. • It offers a life like3D model that can be rotated tilted and angulated like a patients head.

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3D FACIAL MORPHOMETRY • Uses 2 CCD cameras that capture the subject • real time hardware for recognition of markers • software for 3D reconstruction of landmarks.

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• Landmarks are located with a 2mm hemisphere reflective markers.

• An infra red streptoscope is used to light up the reflective markers.

• Two side acquisiton is required to capture the whole face.

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DRAWBACKS • Placement of landmarks on the face is time and labour consuming • Reproducibility of landmark is questionable.

• No life like models are produced to show natural soft tissue appearance of the face.

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APPLICATIONS OF 3D FACIAL IMAGING • Assessment of facial deformity and outcome of surgical and/or orthodontic correction.

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APPLICATIONS OF 3D FACIAL IMAGING • Subjective outcome of deformities, 3D models are a valuable media for locating the source of deformity and its magnitude.

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APPLICATIONS OF 3D FACIAL IMAGING • Assessment of outcome can also be performed easily by visual comparison of pre and post treatment models placed side by side.

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LAND MARK BASED SUPERIMPOSITION

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3D CT SCANNING • Surgical outcome and soft to hard tissue ratio following orthognathic surgery (Mccance et al BJO 1992)

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OPTICAL LASER SCANNING • Used to assess soft tissue changes following functional treatment (Morris et al EJO 1998) • Following extraction and non extraction treatment (MORRIS et al AJO DO 2002) • Following orthognathic surgery (Moss et al AJO DO 1994) • Cleft lip and palate (Mccance et al Cleft Craniofac J 1997) www.indiandentalacademy.com

STEREOPHOTOGRAMMETRY • Assess the outcome of twin block treatment (Bourne et al Clin Orthod 2001) • Combined orthodontic surgical treatment of class II or class III (Hajeer et al Int J Adult Orthod Orthognath 2002)

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3D FACIAL MORPHOMETRY • Application in orthodontics and allied fields (Ferrario et al Plast Reconstr Surg 1999)

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RESULTS OF FACIAL CHANGES • • • •

Landmark identification Inter landmark distance and angles Color millimetric maps Volumetric changes

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3D Dental Imaging

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3D LASER SCANNING • Difficult procedure

• Safety issues

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3D LASER SCANNING OF STUDY CASTS

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APPLICATIONS OF 3D IMAGING OF THE TEETH

Archiving study models (Orthocad)

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VIRTUAL ORTHODONTIC PATIENT

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• Combining 3D skeletal ct scan with vision or laser scanning techniques.

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XIA TECHNIQUE (IJO 2000) • Reconstructing 3D soft and hard tissue models for sequential CT slices using a surface rendering technique • Three colouerd potraits (different colours) were texture mapped onto the 3D mesh • Validity of construction was not evaluated nor was the importance of head postioning www.indiandentalacademy.com

3D CT SKELETAL MAPS AND 3D LASER MODELS • Nishi et al and Terraai et al (JOMS 1997)

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3D SKELETAL DATA WITH 3D LASER SCANNING • Okumura et al (AJO DO 1999) • This cannot be used for prediction of soft tissue changes following treatment.

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3D CEPH DATA WITH 3D LASER SCANNING • Chen and chen (Int J Adult Orthod Orthognat Surg 1999) • 3D computer aided simulation system to plan surgical procedures an to predict post operative changes in orthognathic surgery patients www.indiandentalacademy.com

3D SPIRAL CT SCAN AND STEREOPHPTOGRAMMETRY • Khanay et al (Int J Adult Orthod Orthognat Surg 2002)

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CRANIOFACIAL RESEARCH • Tie points( landmarks placed on speific areas of the face prior to imgaing).

• Anatomic areas marked on the x ray act as refrence points.

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Teleradiology • Teleradiology is the electronic transmission of radiological images from one location to another for the purposes of interpretation and/or consultation

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• When a teleradiology system is used to produce the official authenticated written interpretation,- there should not be a significant loss of spatial or contrast resolution from image acquisition through transmission to final image display.

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3 D FACIAL IMAGING THE CUTTING EDGE

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RECENT ADVANCES IN DIAGNOSTIC AIDS

Dr. Sathwik. B. S.

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3D cone beam c t scan

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Conventional c t scan • Developed by Godfrey hounsfeld (1967)

• Different generations based on organization of the individual parts of the device and physical motion of the beam of capturing the data.

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First generation • Single radiation source and a single detector.

The information obtained by slice and slice.

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Second generation • Multiple detectors within the plane of scan. • These were not continuous nor did they scan the diameter of the object.

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Third generation • Advancement in data acquisition and detector • Fan beam ct.

• Ring artifacts were seen on the image often distorting the 3D image and obscuring certain landmarks.

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Fourth generation • A moving radiation dose and a fixed detector ring were introduced. • More scattered radiation were seen.

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Fifth generation • To reduce motion or scatter artifacts.

• The detector is stationary and electron beam is swept along a semi circular tungsten strip anode.

• The radiation is produced where the electron beam hits the anode and this results In an x ray that rotates about the patient without any translation or scatter.

• 4D motion picture www.indiandentalacademy.com

limitations • Considerable physical space.

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limitations • Much more expensive.

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limitations • Stacking procedure (time consuming and expensive). • Radiation exposure was primarily responsible for limiting its usage.

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CBCT (cone beam CT scan)

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• Developed to overcome some of the limitations of conventional ct scanning.

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Procedure • Object is captured by a 2 d detector so that a single rotation can capture the area of interest • Cone beam also produces less scattering of radiation.

• Radiation exposure is 20% of conventional c t ( equal to full mouth IOPA) www.indiandentalacademy.com

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Advantages of CBCT • Reduction in the cost

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Advantages of CBCT • Smaller in size • Exposure chamber (head) is custom built and reduces the amount of radiation

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Advantages of CBCT • Images are comparable to conventional c t and are displayed as full head view or regional components.

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• CBCT machines are available for different size,possible settings,area of image capture and field of view.

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Acquisition systems • • • •

New tom 3 g (quantitative radiology Italy) I cat ( imaging sciences international USA ) C b mercury ( Hitachi medical corp., japan) 3 d acuitomo ( J morita mfg corp. ).

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New tom 3 g • Image capture is done in 36 sec.

• Voxel resolution of .125mm.

• They can be incorporated into dicom 3 d software for analysis.

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I cat • 20 – 40 sec image capture time • Field view of 20 x 25 cms can be obtained .

• Amorphous silicon flat panel detector produces no distortion.

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Cb mercury ray • Image intensifier and a solid state ccd. • Gives 288 views in 10 sec .

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3 d accuitomo • Field of view 30x40 mm focuses on regional and anatomical investigations • Small size ( 1.6 times an OPG unit ).

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Clinical applications

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Impacted teeth

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Airway analysis • Aboudara et al (orthod craniofac 2003) • Showed variability in the upper airway space compared with lateral ceph.

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Assessment of alveolar bone height and volume • Hatcher et al ( 2003) site for implant placement.

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Lateral and frontal cephalometric views

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Advantages over other cephalograms • True 1:1 representation of the structure being imaged. • Avoiding superimposition of irrelevant structures.

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3 d skeletal views

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3 d facial analysis

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Alveolar ridge shape and volume

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3 d review of dentition

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TMJ analysis

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Radiation exposure • Depends on the kvp and ma.

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Alara principle • Radiographs on the patient needs • Using the fastest film compatible with the diagnostic task • Collimating the size of the beam to as close o film size.

• Using lead aprons and thyroid shields.

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Drawbacks • Map out the muscle structures and their attachments • True colour texture of the skin cannot be captured • Long capture time of the full view of a subject ( 30 –40 sec).

• High costs

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Resorption of incisors after ectopic eruption of maxillary canines: a CT study • Angle orthodontist 2000 (Sune Ericson and Kurol)

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Superimposition of 3D cone beam CT models of orthognathic surgery patients • British journal of radiology 2005 (Bailey et al)

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MRI scan

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• Formerly called as NMR ( nuclear magnetic resonance ) • Primarily used to demonstrate the physiological or pathological alterations in living tissues.

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History of MRI • Developed by Dr. Raymond Damadian and a group of graduate students at downtown medical centre.

• First performed in July 1997.

• Paul Lauterbur and sir Peter Mansfield were awarded the Nobel prize in 2003.

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• • • • • • •

What is an MRI scan How does a MRI scanner work What does a MRI scan show When are MRI scans done How is an MRI scan done Difference between an MRI and CT scan Risks and safety issues concerning an MRI scan www.indiandentalacademy.com

What is a MRI scan? • Is a radiological technique that uses magnetism, radio waves and a computer to produce images of body waves.

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How does a MRI scanner work • Radio waves 10,000 – 30,000 times stronger than the magnetic field of earth are sent through the body.

• Body produces radio waves of its own.

• Scanner picks up these signals and a computer turns them into an image.

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What does an MRI scanner show • It is possible to make pictures of all body structures.

• Less hydrogen atoms (darker).

• More hydrogen atoms (brighter). www.indiandentalacademy.com

• It is possible to get clear pictures of body that are surrounded by bone tissue (brain and spinal cord).

• Best technique to find out tumors especially of the brain .

• MULTIPLE SCLEROSIS (BLEEDING) and lack of oxygen or stroke.

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When are MRI scans used • • • •

Brain tumors Integrity of spinal cord after trauma.

Structure of the heart and aorta.

Accurate information of the joints, soft joints and bones inside the body.

• Surgeries can be accurately directed after MRI.

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Dental applications • Relation of orthodontics and TMD (Temperomandibular disorders).

• Post treatment • Results of orthognathic surgeries.

• Effects of mandibular advancements in obstructive sleep apnea.

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How is an MRI scan performed?

• Out patient procedure • Patient needs to relax.

• All metallic objects need to be removed before the scan • Remove all hearing aids or pace makers.

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• Loud clicking noises are heard which may be uncomfortable for the patient. • Iv injections are necessary to enhance the images

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• Water • Paramagnetic contrast compound (gandolium compound) • Super-magnetic contrast agents (iron oxide nano particles) • Diamagnetic agents (barium sulphate)

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Safety procedure • Implants and foreign objects

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Ferromagnetic foreign bodies • Shell fragments • Metallic implants

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Reactions • Trauma due to movement of objects in magnetic field • Thermal injury • Failure of an implanted device

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Projectiles • Missile effect accidents ( attractions of ferromagnetic objects towards Center of magnet)

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Radiofrequency energy • Hyperthermia in children.

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Acoustic noise • 130 db ( jet engine take off) • Appropriate use of ear protection

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Cryogens • Emergency shut down of superconducting magnet leads to an operation called quenching.

• Release of helium and risk of asphyxiation.

• Recommissioning of magnet is extremely expensive

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Is MRI scan dangerous • There are no known side effects.

• Within first 12 weeks of pregnancy.

• Because of large cylinder the procedure may be claustrophobic.

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Specialized MRI scans • Diffusion MRI scanning - diffusion tensor imaging - diffusion weighted imaging • Magnetic resonance angiography • Magnetic resonance spectroscopy • Interventional MRI • Radiation therapy stimulation • Current density imaging www.indiandentalacademy.com

Applications of MRI scanning

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MRI of pharynx and treatment efficiency of mandibular advancement in OSPS • Eur resp j 2002 (Sanner et al )

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Orthodontics and TMD • AJO DO 2002 (Grabber et al )

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Frankel appliance therapy and TMD • AJO DO 2002 (Franco et al )

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Rigid versus wire fixation for mandibular advancement • AJO DO 2002 (Dolce et al )

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Changes in condylar disc position and tm after disc repositioning therapy • Angle orthodontist feb 2000 (Hatice and Turkharmann)

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