DIAGNOSTIC IMAGING IN IMPLANTS
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
ď ŹHISTORY ď ŹCLINCAL
Mounted study casts. Joint assessment Surgeon/restortive dentist.
Treatment plan Informed consent www.indiandentalacademy.com
Imaging modalities. 1. 2. 3. 4. 5. 6. 7. 8.
•Can also be classified as Periapical radiography Analog and digital Panoramic radiogrphy 2- dimensional and 3Occlusal radiography dimensional. Cephalometric radiography Tomography Computed tomography Magnetic resonance imaging. Interactive computed tomography. www.indiandentalacademy.com
• Imaging modlities can be divided into – planar two dimensional – Quasi three dimensional – Three dimensional
Planar two dimensional. • It includes – – – –
Periapical bite wing occlusal cephalometric imaging
• These are simple two dimensional projection of the patients anatomy. • It is not possible for the clinician to develop a three dimensional perspective of the patients anatomy with a single image. • With a number of cleverly oriented projections it is possible to develop some useful three dimensional information www.indiandentalacademy.com
Quasi three dimensional • It includes – X –ray tomography – Cross sectional panoramic imaging techniques.
• With these techniques, a number of loosely spaced tomographic images are produced. • 3-dimensional perspective of the patient anatomy is developed by viewing each image and mentally filling in the gaps. www.indiandentalacademy.com
3 dimensional imaging. • It includes – Computed tomography. – Magnetic resonance imaging.
• It enables the clinician to view a volume of the patients anatomy. • These techniques are quantitatively accurate and 3-D models of the patients anatomy can be derived from the image date and used to produce stereotactic surgical guides and prosthetic frameworks. www.indiandentalacademy.com
Implant imaging can be divided into 3 phases. • Phase I : Preprosthetic implant imaging. • Phase II : Surgical and interventional implant imaging. • Phase III : Postprosthetic implant
Preprosthetic Implant Imaging. â€˘ It involves a. All past radiologic examinations. b. New radiologic examinations to assist in final and comprehensive treatment plan. www.indiandentalacademy.com
Objectives 1. To rule out presence of disease at the proposed surgery site. 2. to determine the bone quantity, 3. to determine the bone density 4. To evaluate the relationship of critical structures to the prospective implant sites. 5. Determine the optimum position of implant placement relative to occlusal loads. www.indiandentalacademy.com
Periapical radiography. • Periapical radiographs provide a high resolution planar image of a limited region of the jaws. • No 2 size dental film provides a 25 by 40 mm view of the jaw with each image. • Periapical radiographs provide a lateral view of the jaws and no cross sectional information. • Adjacent periapical radiographs made with limited oblique orientations , third dimensional information is of little use for the implant imaging. www.indiandentalacademy.com
• Periapical radiographs suffer from both distortion and magnification. • Millimeter radio opaque grids like those used in Endodontics can be used – but usually provide misleading information.
How good are periapical in terms of objectives of preprosthetic imaging? • It is a useful high –yield modality for ruling out local bone or dental disease. • Is of limited value in determining quantity because the image is magnified, may be distorted and does not depict the third dimension of bone width. • Of limited value in determining bone density or mineralization (lateral cortical plates prevent accurate interpretation and cannot differentiate subtle trabecular bone changes).
• Of value in identifying critical structures. But poor in depicting spatial relationship between the structures and www.indiandentalacademy.com the proposed implant site.
â€˘ in preprosthetic phase periapical radiographs are often used for single tooth implants in regions of abundant bone width.
Occlusal Radiography. • Occlusal radiographs produce high resolution planar images of the body of the mandible or the maxilla. • Placement of film parallel to the occlusal plane • central X-ray – Mandible: perpendicular to the film – Maxilla: oblique (usually 45 degrees) to the film. www.indiandentalacademy.com
Maxillary occlusal radiographs are inherently oblique and so distorted they are of no quantitative use for implant dentistry. â€˘ Mandibular occlusal radiograph is less distorted 1. BUT Mandibular alveolus generally flares anteriorly and demonstrates a lingual inclination posteriorly, producing an oblique and distorted image of the mandibular alveolus, which is of little use in implant dentistry. www.indiandentalacademy.com
2. Shows widest width of the bone whereas the width at the crest is of more diagnostic value. 3. Degree of mineralization of trabecular bone is not determined from this projection. 4. Spatial relationship between critical structures such as mandibular canal and mental foramen and the proposed implant site is lost. â€˘ Occlusal radiographs are rarely indicated for diagnostic preprosthetic phases in implant dentistry www.indiandentalacademy.com
Cephalometric radiographs • Cephalometric radiographs are oriented planar radiographs of the skull. • The skull is oriented with respect to the x-ray device and the image receptor using a Cephalometer. • The geometry of cephalometric imaging devices results in a 10% magnification of the image with a 60 inch focal object and a 6 inch object to film distance. www.indiandentalacademy.com
â€˘ Lateral cephalometric radiograph: â€“ is produced with the patients mid sagittal plane oriented parallel to the image receptor. â€˘ With a slight rotation of the Cephalometer, a cross sectional image of the mandible or maxilla can be demonstrated in the lateral incisor or in the canine regions as well.
1. It demonstrates the geometry of the alveolus in the anterior region and the relationship of the lingual plate to the patients skeletal anatomy. Useful in placing mandibular anterior implants. 2. Width of the bone in symphysis region- for harvesting this bone for ridge augmentation. 3. Together with regional periapical radiographs spatial relationships can be visualized. 4. Evaluating loss of vertical dimension 5. Skeletal arch interrelationship 6. Anterior implant crown ratio 7. Anterior tooth position in prosthesis 8. Resultant moment of force. www.indiandentalacademy.com
â€˘ This technique is not useful for demonstrating bone quality. â€˘ It is useful tool for the development of an implant treatment plan especially for the completely edentulous patient.
Panoramic radiography. • It is a curved plane tomographic radiographic technique used to depict the body of the mandible, maxilla, and the lower one half of the maxillary sinuses in a single image. • It is probably the most utilized diagnostic modality in implant dentistry Though it is not the most diagnostic. • It produces an image of a section of the jaws of variable thickness and magnification. www.indiandentalacademy.com
â€˘ Tomographic section thickness is approximately 20mm in the posterior region and 6 mm in anterior region. â€˘ Image receptor has traditionally been an Xray film but may be a digital storage phosphor plate or a digital CCD receptor.
• Non uniform magnification of structures produces images with distortion that cannot be compensated for in treatment planning • Vertical magnification is approximately 10%. • Horizontal magnification is 20% and varies according to • • • •
anatomic location. Position of the patient Focus object distance. Location of the rotation center www.indiandentalacademy.com
Disadvantages 1. Does not demonstrate bone quality/mineralization. 2. Is misleading quantitatively because of magnification and because the third dimension, cross sectional view is not demonstrated. 3. Is of some use in demonstrating critical structures but of little use in depicting the spatial relationship between the structures and dimensional quantification of the implant site. 4. Dimensions of inclined structures cannot be relied upon in panoramic radiographs. www.indiandentalacademy.com
â€˘ Advantages. 1.Opposing landmarks are easily identified 2.The vertical height of bone initially can be assessed. 3.Te procedure is performed with convenience, ease ,and speed inmost dental offices. 4.Gross anatomy of the jaws and any related pathologic findings can be evaluated.
â€˘ Posterior maxillary regions are generally the least distorted regions of the panoramic radiographs. â€˘ Maxillary edentulous anterior region is often the most difficult area of a panoramic radiograph to evaluate because of the curvature of the alveolus and the inclination of the bone. www.indiandentalacademy.com
Zonography â€˘ This is a modification of the panoramic xray machine with the capability of making a cross sectional image of the jaws. â€˘ This technique enables the appreciation of spatial relationship between the critical structures and the implant site and quantification of the geometry of the implant site. www.indiandentalacademy.com
tomography â€˘ It is a generic term,formed from the reek words tome(slice ) and graph(picture). â€˘ It was adopted in 1962 by the international commission on radiologic units and measurements(ICRU) to describe all forms of body section radiography.
Components. • Fulcrum bar • Fulcrum : it remains stationary and defines the section of interest or the tomographic layer. • Different tomographic sections are produced by adjusting the position of the fulcrum or the position of the patient relative to the fulcrum in fixed geometry systems.
• Linear tomography is the simplest form of tomography where the X-ray tube and film move in a straight line.
• Complex motion, high quality tomography is described by two dimensional motion of the tube and film. – It results in relatively uniform blurring of the regions of the patients anatomy adjacent to the tomographic section. – Hypocycloidal motion is generally accepted as the most effective blurring motion. www.indiandentalacademy.com
• Large amplitude tube travel and 1 mm sections are preferred for high contrast anatomic objects whose geometry changes in a relatively short distance,such as the alveolus of the jaws • Complex motion tomography helps in – Quantification of the geometry of the alveolus. – Determining spatial relationship between critical structures. – Quantity of alveolar bone available.
• Complex tomography is not particularly useful in determining bone quality or identifying dental and bone www.indiandentalacademy.com diseases
Computed tomography. â€˘ Computed tomography(CT) is a digital and mathematical imaging technique that creates tomographic sections where the tomographic layer is not contaminated by blurred structures from adjacent anatomy.
• It enables differentiation and quantification of both soft and hard tissue. • CT was invented by sir Hounsfield and announced to the imaging world in1972. • Ct produces axial images of a patients anatomy . • Axial images are produced perpendicular to the long axis of the body. www.indiandentalacademy.com
• The X-ray source is attached rigidly to a fan-beam geometry detector array,which rotates 360 degrees around the patient and collects data. • The image detector is either a a gaseous or solid state producing electronic signals that serve as input data for a dedicated computer. • The computer processes the data using back projection Fourier algorithm techniques. • The individual element of the CT image is called a voxel,which has a value,referred to in hounsfield units, that describe the density of the CT image at that point www.indiandentalacademy.com
• Ct scanners are standardized at a hounsfield value of 0 for water. • The CT density scale is quantitative and meaningful in identifying and differentiating structures and tissues. • The original imaging computer can create secondary images from almost any perspective by reprojecting or reformatting the original three dimensional voxel data. www.indiandentalacademy.com
• The utility of CT for dental implant treatment planning was obvious from the beginning • But the access to these imaging techniques was limited. • This led to development of specific techniques generally referred to as Dentascan imaging. www.indiandentalacademy.com
Tissue Air Water Muscle Fibrous tissue Cartilage Trabecular bone Corticalbone Dentine Enamel.
Hounsfield units -1000 0 35-70 60-90 80-130 150-900 900-1800 1600-2400 2500-3000 www.indiandentalacademy.com
Dentascan â€˘ The radiologist simply indicates the curvature of the mandibular or maxillary arch. â€˘ the computer is programmed to generate referenced cross sectional and tangential/panoramic images of the alveolus along with 3-D images of the arch. â€˘ The cross sectional and panoramic images are spaced 1mm apart and enable accurate preprosthetic treatment planning. www.indiandentalacademy.com
Limitations of dentascan. 1. Images may not be of true size and require compensation for magnification. 2. Determination of bone quality requires use of the imaging computer or workstation. 3. Hard copy dentascan images only include a limited range of the diagnostic gray scale of the study. 4. Tilt of the patients head during the examination is critical because all the cross sectional images are perpendicular to the axial imaging plane www.indiandentalacademy.com
• CT enables – – – –
Identification of disease Determination of bone quality Identification of critical structures Determines orientation and position of implants
• Thus CT is capable of determining all five of the radiologic objectives of the preprosthetic implant imaging. • Usually a diagnostic template is necessary to take full advantage of the technique. www.indiandentalacademy.com
Interactive computed tomography(ICT) • It address many of the limitations of CT. • ICT is a technique that was developed to bridge the gap in information transfer between the radiologist and the clinician. • The radiologist transfers the imaging study to the clinician as a computer file for clinician to view and interact with the image in their own computer. www.indiandentalacademy.com
• Clinicians computer becomes a diagnostic radiologic workstation with tools to measure the length and width of the alveolus,measure bone quality ,and change the window and level of gray scale of the study to enhance the perception of critical structures. • An important feature of the ICT is that the clinician and radiologist can perform “electronic surgery “ (ES) by selecting and placing arbitrary size cylinders that simulate root form implants in the images. www.indiandentalacademy.com
Limitations of ICT. â€˘ Refinement and exact orientation of the implant positions is difficult and cumbersome. â€˘ Executing the plan maybe difficult for the surgical team.
Magnetic resonance imaging. â€˘ MR is a imaging technique used to image the protons of the body by employing magnetic fields, radio frequencies,electro magnetic detectors,and computers. â€˘ The technique was first announced by lauterbur in 1972. â€˘ It is a 3 dimensional imaging technique with an electronic image acquisition process and a resulting digital image. www.indiandentalacademy.com
• The image sequence employed to obtain MR images can be varied to obtain fat,water, or balanced imaging of the patients anatomy. • MR images are the antithesis of CT images with cortical bone appearing dark or black and fat or water appearing bright or white. • Like CT,MR is a quantitatively accurate technique with exact tomographic sections and no distortions.
• Complex tomography fails to differentiate the inferior alveolar canal in 60% of the implant cases • CT fails to differentiate the inferior alveolar canal in approximately 2% of implant cases. • MR visualizes the fat in trabecular bone and differentiates the inferior alveolar canal and neurovascular bundle from the adjacent trabecular bone.
â€˘ MR is used in implant imaging as a secondary imaging technique when primary imaging techniques such as complex tomography,CT or ICT fail. â€˘ MR is not useful in characterizing bone mineralization or a high yield technique for identifying bone of dental disease.
Surgical and interventional implant imaging â€˘ â€˘
It assists in the surgical and prosthetic intervention of the patient. Objectives 1) Evaluate the surgery sites during and immediately after surgery. 2) Assist in the optimal position and orientation of the dental implants 3) Evaluate the healing and integration phase of implant surgery. 4) Ensure abutment position and prosthesis fabrication are correct. www.indiandentalacademy.com
â€˘ As most implant surgeries are performed in the doctors office rather than in hospital ,the modalities are usually limited to periapical and panoramic radiography. â€˘ The patient can be generally imaged at chair side with periapical radiography to determine implant/osteotomy depth,position and orientation. â€˘ Disadv : approximately 5 minutes are required in dark room procedure. www.indiandentalacademy.com
â€˘ An x â€“ray examination is also performed to determine if the metal framework or final restoration is completely seated,and the margins are acceptable around the implant or teeth.
Postprosthetic implant imaging. â€˘
It commences just after the prosthesis placement and continues as long as the implants remain in the jaws. Objectives 1. Evaluate the long term maintenance of implant rigid fixation and function. 2. Evaluate crestal bone levels 3. Evaluate the implant complex www.indiandentalacademy.com
Bite wing radiographs â€˘ The short and long term evaluation of crestal bone loss around implants is best evaluated with Intraoral radiographs. â€˘ In these images ,the superior one third of the implant is the region of interest.threaded implants make quantification of marginal bone loss easier to read. www.indiandentalacademy.com
Temporal digital subtraction radiography(SR). â€˘ It is a radiographic technique that enables two radiographs made at different points of time of the same anatomic region to be subtracted resulting in an image of the difference between the two original radiographs. â€˘ The resulting image shows changes inpatients anatomy,such as alveolar mineralization or volume changes. www.indiandentalacademy.com
â€˘ SR has been shown to be considerable more accurate at depicting changes in bone mineralization and bone volume than simply viewing the original periapical radiographs. â€˘ SR has limited utilization in clinical practice because of the difficulty in obtaining reproducible periapical radiographs.
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Published on May 8, 2014
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