Diagnostic imaging and techniques in implant dentistry
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
www.indiandentalacademy.com
Introduction Diagnostic imaging and techniques help to develop and implement a cohesive and comprehensive treatment plan for the implant team and the patient. The decision of when to image along with which imaging modality to use depends on the integration of these factors and can be organized into three phases
www.indiandentalacademy.com
Phase one is termed pre-prosthetic implant imaging and involves all past radiologic examinations along with new radiologic examinations chosen to assist the implant team in determining the patient’s final and comprehensive treatment plan. The objectives of this phase of imaging include all necessary surgical and prosthetic information to determine the quantity, quality, and angulation of bone; the relationship of critical structures to the prospective implant sites; and the presence or absence of disease at the proposed surgery sites. www.indiandentalacademy.com
Phase two is termed surgical and interventional implant imaging and is focused on assisting in the surgical and prosthetic intervention of the patient. The objectives of this phase of imaging are to evaluate the surgery sites during and immediately after surgery, assist in the optimal position and orientation of dental implants, evaluate the healing and integration phase of implant surgery, and ensure abutment position and prosthesis fabrication are correct.
www.indiandentalacademy.com
Phase three is termed post-prosthetic implant imaging. It commences just after the prosthesis placement and continues as long as the implants remain in the jaws. The objectives of this phase of imaging are to evaluate the long-term maintenance of implant rigid fixation and function, including the crestal bone levels around each implant, and to evaluate the implant complex.
www.indiandentalacademy.com
Imaging modalities Once a decision to image the patient has been made, the imaging modality is employed that yields the necessary diagnostic information related to the patient’s clinical needs and results in the least radiologic risk. Some of the imaging modalities that have been reported as useful for dental implant imaging include,
www.indiandentalacademy.com
•
Periapical radiography
•
Panoramic radiography
•
Occlusal radiography
•
Cephalometric radiography
•
Tomography
•
Computed tomography
•
Magnetic resonance imaging
•
Interactive computed tomography www.indiandentalacademy.com
The imaging modalities listed above can be sub divided into planar two dimensional, quasi three dimensional, and three-dimensional imaging modalities. Planar imaging modalities include periapical bite wings, occlusal and cephalometric imaging and are simply two dimensional projections of the patient’s anatomy. Thus, it is not possible for the clinician to develop a three-dimensional perspective of the patient’s anatomy with a single image.
www.indiandentalacademy.com
Quasi three-dimensional imaging modalities include x-ray tomography and some cross sectional panoramic imaging techniques. With these techniques, a number of closely spaced tomographic images are produced and the three dimensional perspective of the patient’s anatomy is developed by viewing each image and mentally filling in the gaps. Three-dimensional imaging techniques include computed tomography and magnetic resonance imaging and enable the clinician to view a volume of the patient’s anatomy. These techniques are quantitatively accurate and three-dimensional www.indiandentalacademy.com models of the patient’s anatomy can be derived from
Most dentists are more familiar with analog, twodimensional imaging. Analog imaging modalities are two-dimensional systems that employ x-ray film and/or intensifying screens as the image receptors Digital images can also be produced with each imaging modality listed before. A digital twodimensional image is described by an image matrix that has individual picture elements called pixels. A digital image is described by its width and height and pixels (i.e., 512 by 512). For larger digital image (i.e., 1.2M by 1.2M [M= megapixel]), the image is alternatively described as a 1.5 megapixel image. Each picture element or “pixel� has a discrete digital value that describes the image intensity at that particular point. www.indiandentalacademy.com The value of a pixel element is described by a scale,
which may be as low as 8 bits (256 values) or as high as 12 bits (4096 values) for black and white imaging systems, or 36 bits (65 billion values) for color imaging systems. Black and white digital images are optimally displayed on a dedicated black and white monitor. Generally, 8 bits or 256 levels can be effectively displayed on a monitor A digital three-dimensional image is described by an image matrix that has individual image/picture elements called voxels. A digital three-dimensional image is described not only by its width and height and pixels (i.e., 512 by 512), but additionally, by its depth/thickness. An imaging volume or threedimensional characterization of the patient is produced www.indiandentalacademy.com by contiguous images, which produces a three
dimensional structure of volume elements (i.e., computed tomography, magnetic resonance imaging and interactive computed tomography). Each volume element has a value that describes its intensity level. Typically, three-dimensional modalities have an intensity scale of 12 bits or 4096 values. The threedimensional imaging modalities are as follows, •
Computed tomography
•
Magnetic resonance imaging
•
Interactive computed tomography
www.indiandentalacademy.com
Preprosthetic imaging This phase of implant imaging is intended to evaluate the current status of the patient’s teeth and jaws and to develop and refine the patient’s treatment plan. The specific objectives of preprosthetic imaging are to, 1. Identify disease 2. Determine bone quantity 3. Determine bone density 4. Identify critical structures at the proposed implant regions 5. Determine the optimum position of implant www.indiandentalacademy.com placement relative to occlusal loads.
Periapical radiography Periapical radiographs are images of a limited region of the mandibular or maxillary alveolus. Periapical radiographs are produced by placing the film intraorally parallel to the body of the alveolus with the central ray of the x-ray device perpendicular to the alveolus at the region of interest, producing a lateral view of the alveolus. Periapical radiographs provide a lateral view of the jaws and no cross sectional information. Periapical radiographs may suffer from both distortion and magnification. The long cone paralleling technique will eliminate distortion and limit magnification to lesswww.indiandentalacademy.com than 10%.
Burn out effects are common when standard kV and mA are used, making crestal bone loss with digital intraoral systems of benefit in these situations. In terms of the objectives of pre-prosthetic imaging, periapical radiography is 1. A useful high yield modality for ruling out local bone or dental disease. 2. Of limited value in determining quantity because the image is magnified, may be distorted, and does not depict the third dimension of bone width, 3. Of limited value in determining bone density or mineralization (the lateral cortical plates prevent accurate interpretation and cannot differentiate subtle trabecular www.indiandentalacademy.com
bone changes) . 4. Of value in identifying critical structures, but of little use in depicting the spatial relationship between the structures and the proposed implant site. In the pre-prosthetic phase, these films are most often used for single tooth implants in regions of abundant bone width.
www.indiandentalacademy.com
Occlusal radiography Occlusal radiographs are planar radiographs produced by placing the film intraorally parallel to the occlusal plane with the central x-ray perpendicular to the film for the mandibular image and oblique (usually 45 degrees) to the film for the maxillary image. Occlusal radiography produces high-resolution planar images of the body of the mandible or the maxilla. Maxillary occlusal radiographs are inherently oblique and so distorted they are of no quantitative use for implant dentistry, for either determining the geometry or the degree of mineralization of the implant site. Additionally, critical structures such as the maxillary sinus, nasal cavity and nasal palatine canal are demonstrated but thewww.indiandentalacademy.com cavity, and nasal palatine canal
are demonstrated, but the spatial relationship to the implant site is generally lost with this projection. Because the mandibular occlusal radiograph is an orthogonal projection, it is less distorted projection than the maxillary occlusal radiograph. However, the mandibular alveolus generally flares anteriorly and demonstrates a lingual inclination posteriorly. It produces an oblique and distorted image of the mandibular alveolus, which is of little use in implant dentistry. As a result, occlusal radiographs are rarely indicated for diagnostic pre-prosthetic phases in implant dentistry. www.indiandentalacademy.com
Cephalometric radiographs Cephalometric radiographs are oriented planar radiographs of the skull. A cross sectional image of the alveolus of both the mandible and the maxilla in the midsagittal plane is demonstrated by this radiograph. 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. The lateral cephalometric radiograph is useful because it demonstrates the geometry of the alveolus in the anterior region and the relationship of the lingual plate to the patient’s skeletal anatomy. The width of bone in the symphysis region and the relationship betweenwww.indiandentalacademy.com the buccal cortex and the roots of
the anterior teeth may also be determined before harvesting this bone for ridge augmentation. Together with regional periapical radiographs, quantitative spatial information is available to demonstrate the geometry of the implant site and spatial relationship between the implant site and the spatial relationship between the implant site and critical structures such as the floor of the nasal palatine canal. Additionally the lateral cephalometric view can help evaluate a loss of vertical dimension, skeletal arch interrelationship, anterior crown implant ratio, anterior tooth position in the prosthesis and resultant moment of forces. www.indiandentalacademy.com
If desired foil can be placed over the anterior teeth in a set of dentures, which if worn during exposure of the lateral cephalogram, can demonstrate clearly the relationship of the teeth to the ridge and the ridge relationship. This provides insight as to angulation of the implants to place them in ideal locations for the implant supported or tissue supported prosthesis. However, this technique is not useful for demonstrating bone quality.
www.indiandentalacademy.com
Panoramic radiography Panoramic radiography 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. Panoramic images offer the following advantages, 1.
Opposing landmarks are easily identified.
2. The vertical height of bone initially can be assessed 3. The procedure is performed with convenience, ease, and speed in most dental offices. 4.
www.indiandentalacademy.com Gross anatomy of the jaws and any related
Panoramic Magnification: Panoramic radiography is characterized by an image of the jaws that demonstrates both vertical and horizontal magnification, along with a tomographic section, thickness that varies according to the anatomic position. Nonuniform magnification of structures produces images with distortion that cannot be compensated for in treatment planning. The posterior maxillary regions are generally the least distorted regions of a panoramic radiograph. www.indiandentalacademy.com
Panoramic radiography 1. Does not mineralization
demonstrate
bone
quality/
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 quantitation of the implant site.
www.indiandentalacademy.com
Because panoramic radiography is such a popular and widely available technique in dentistry, clinicians have developed means to compensate for panoramic radiography’s shortcomings. It has been demonstrated recently that the use of templates with incorporated metal spheres of known diameter in situ when the radiograph is taken can effectively eliminate the distortion problems. The metal spheres appear radiopaque in the final film. Because their diameter is known, it is easy to calculate the true bone height. www.indiandentalacademy.com
Here is an example of the calculation for the posterior region: The true diameter of the sphere (D-real) is 5 mm, but its diameter on the radiograph (D-PR) is measured at 6 mm. The distance between the alveolar crest and the mandibular canal is measured on the film as 18mm (A-PR). To determine the real distance between the alveolar crest and the mandibular canal (A-real), simply solve the following equation. A-real / A-PR = D-real / D-PR A-real = 18 Ă— 5 / 6 A-real = 15 mm www.indiandentalacademy.com
However, studies have demonstrated the mandibular foramen cannot be identified 30% of the time on the x-ray and when visible may not identified correctly. Dimensions of inclined structures cannot be relied upon in panoramic radiographs. Recently a modification of the panoramic x-ray machine has been developed that has the capability of making a cross sectional image of the jaws. These devices employ limited angle linear tomography (zonography) and a means for positioning the patient. The tomographic layer is approximately 5 mm. 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. This technique is not useful www.indiandentalacademy.com
for determining the differences in most bone densities or identifying disease at the implant site. Tomography Tomography is a generic term, formed from the Greek words tomo (slice) and graph (picture). Body section radiography is a special x-ray technique that enables visualization of a section of the patient’s anatomy by blurring regions of the patient’s anatomy above and below the section of interest. There have been many ingenious tomographic methods and devices. However, the basic principle of tomography is that the x-ray tube and film are connected by a rigid www.indiandentalacademy.com bar called the fulcrum bar, which
pivots on a point called the fulcrum. When the system is energized, the x-ray tube moves in one direction with the film plane moving in the opposite direction and system pivoting about the fulcrum. The fulcrum remains stationary and defines the section of interest, or the tomographic layer. Factors that affect tomographic quality are the amplitude and direction of tube travel. The greater the amplitude of tube travel, the thinner the tomographic section. Linear tomography is the simplest form of tomography where the x-ray tube and film move in a straight line. Circular, spiral, and hypocycloidal are tube motions employed in complex tomography. Magnification varies from approximately 10% to 30% with higher www.indiandentalacademy.com
magnification generally producing higher quality images. For dental implant patients high quality complex motion tomography demonstrates the alveolus, and taking magnification into consideration, enables quantification of the geometry of the alveolus. This technique also enables determination of the spatial relationship between the critical structures and the implant site. Ideally, tomographic section spaced every 1 or 2 mm enable evaluation of the implant site region, and with mental integration, enable appreciation of the quasi three dimensional appearance of the alveolus. The quantity of alveolar bone available for implant placement can be determined by compensation for www.indiandentalacademy.com magnification. Post imaging digitization of tomographic
implant images enables use of a digital ruler to aid in the determination of alveolar bone for implant placement. Image enhancement can aid in identifying critical structures such as the inferior alveolar canal.
www.indiandentalacademy.com
Computed tomography 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. Additionally, and probably most important, computed tomography enables differentiation and quantification of both soft and hard tissues. CT was invented by sir Hounsfield and announced to the imaging world in 1972. CT images are inherently three dimensional digital images typically 512 by 512 pixels with a thickness described by the slice spacing www.indiandentalacademy.com of the imaging technique.
www.indiandentalacademy.com
www.indiandentalacademy.com
The individual element of the CT image is called a voxel, which has a value, referred to in Hounsfield units, that describes the density of the CT image at that point. Each voxel contains 12 bits of data and ranges from –1000 (air) to +3000 (enamel/dental materials) Hounsfield units. 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 density of structures within the image is absolute and quantitative and can be used to differentiate tissues and the region and characterize www.indiandentalacademy.com bone quality.
CT enables identification of disease, determination of bone quantity, identification of critical structures at the proposed regions, and determination of the position and orientation of the dental implants. Thus CT is capable of determining all five of the radiologic objectives of pre-prosthetic implant imaging
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
Interactive computed tomography This technique enables the radiologist to transfer the imaging study to the clinician as a computer file and enable the clinician to view and interact with the imaging study on their own computer. The clinician’s computer becomes a diagnostic radiologic workstation with tools to measure the length and the width of the alveolus, measure bone quality and change the window and level of the gray scale of the study to enhance the perception of critical structures. An important feature of ICT is that the clinician and radiologist can perform “electronic surgery� (ES) by selecting and placing arbitrary size www.indiandentalacademy.com
cylinders that stimulate root form implants in the images. With an appropriately designed diagnostic template, ES can be performed to electronically develop the patient’s treatment plan in three dimensions. With the number and size of implants accurately determined along with the density bone at the proposed implant sites, characteristics of implants can be accurately determined before surgery. At this time, ICT is the most accurate imaging technique for implant imaging and surgery but suffers some limitations. ES enables placement of electronic implants in the imaging study but refinement and exact relative orientation of the implant positions is www.indiandentalacademy.com
difficult and cumbersome. Transfer of the plan to the patient at the time of surgery can be accomplished by simple visualization and comprehension by a skilled and experienced surgeon, using positions and orientations obtained from ICT and ES to convert the diagnostic template into a surgical template. It can also be accomplished by the production of the computer generated, three-dimensional stereotactic surgical templates from the digital ICT and ES data.
www.indiandentalacademy.com
Magnetic resonance imaging Magnetic resonance (MR) imaging is a technique developed in medical imaging that is probably the most innovative and revolutionary other than computed tomography. MR is an imaging technique used to image the protons of the body by employing magnetic field, radio frequencies, electromagnetic detectors, and computers. The technique was first announced by Lauterbur in 1972. Digital MR images are characterized by voxels with an in-plane resolution measured pixels (512 by 512) and millimeters and section thickness measured in millimeters (2 to 3 mm) for high resolution imaging www.indiandentalacademy.com acquisitions.
MR is used in implant imaging as a secondary imaging technique when primary imaging techniques such as complex tomography, CT, or ICT fail. Complex tomography fails to differentiate the inferior alveolar canal in 60% of implant cases and CT fails to differentiate the inferior alveolar canal in approximately 2% of implant cases. Failure to differentiate the inferior alveolar canal may be caused by osteoporotic trabecular bone and poorly corticated inferior alveolar canal. MR visualizes the fat in trabecular bone and differentiates the inferior alveolar canal and neurovascular bundle from the adjacent trabecular bone. MR is not useful in characterizing bone mineralization www.indiandentalacademy.com or for identifying bone or dental disease.
Diagnostic templates The purpose of diagnostic radiographic templates is to incorporate the patient’s proposed treatment plan into the radiographic examination. This requires that a treatment plan be developed prior to the imaging procedure. The pre-prosthetic imaging procedure enables evaluation of the proposed implant site at the ideal position and orientation identified by radiographic markers incorporated into the template.
www.indiandentalacademy.com
Computed tomography The precision of CT enables use of complex and precise diagnostic template. The exact position and orientation of the implant, which many times determines the actual length and diameter of the implant, is often dictated by the prosthesis. As such, a diagnostic template used during imaging is most beneficial. The surfaces of the proposed restorations and the exact position and orientation of each dental implant should be incorporated into the diagnostic CT template.
www.indiandentalacademy.com
There are two diagnostic templates, one produced from the vacuform reproduction, and one produced from a processed acrylic reproduction of the diagnostic wax-up. The processed acrylic template is modified by coating the proposed restoration with a thin film of barium sulfate and filling a hole drilled through the occlusal surface of the restoration with gutta percha. The surfaces of the proposed restoration then become radiopaque in the CT examination and the position and orientation of the proposed implant is identified by the radiopaque plug of gutta percha within the proposed restoration. www.indiandentalacademy.com
The vacuform template has a number of variations. One design involves coating the proposed restorations with a thin film of barium sulfate. Another design involves filling the proposed restoration sites in the vacuform of the diagnostic wax up with a blend of 10% barium sulfate and 90% cold cure acrylic. This results in a radiopaque tooth appearance of the proposed restorations in the CT examination. The last design modifies the previous design by drilling a 2 mm hole through the occlusal surface of the proposed restoration at the ideal position and orientation of the proposed restoration at the ideal position and orientation of the proposed implant site with a twist drill. This results in a natural tooth like appearance to the proposed restoration in the CT examination where www.indiandentalacademy.com all the surfaces for the restoration are evident along
with a 2-mm. radiolucent channel through the restoration, which precisely identifies the position and orientation of the proposed implant.
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
The circumference guide only traces the outline of the planned prosthesis; it does not provide necessary transposition of prosthetic and/ or bone angulation information. The vertical lead strip and gutta-percha guides serve primarily as imaging indicators and allow for some surgical latitude in preparation of osteotomy sites. The metal sleeve guide used in conjunction with a set up disk appears to be the most accurate imaging and surgical guide. It serves as an imaging and a precision surgical osteotomy guide, ensuring consistency between the planned prosthetic angulation (confirmed by diagnostic imaging) and the trajectory of osteotomy during the surgical phase. www.indiandentalacademy.com
Although intracoronal cylinders and barium sulfate allowed one to evaluate the relationship of the final restoration to available bone, problems still existed. First, the adjacent cross-sections in the CT study appeared similar, and identifying a specific area posed problems. Second, because intracoronal markers were removed before or during surgery, the ability to maintain the proper orientation determined from the CT scan was lost. Maintaining proper orientation can be achieved by use of a diagnostic/surgical template with an external guide wire and precision milled cylinders, used initially during the radiographic imaging phase and then subsequently duringwww.indiandentalacademy.com the surgical phase. The location
and inclination of theintended implant placement can be transferred accurately to the diagnostic/surgical template by use of precision milled cylinders. These cylinders are placed in the template at the proper angulation and linear dimensions are extrapolated from the CT. Incorporation of wires placed on the buccal surface of the template allows identification of the preferred implant site. Once the cylinder is removed, the externally placed buccal wire remains a constant and consistent reference point to be used throughout the surgery. Kevin. C. Kopp etal in their article illustrated a technique to allow precise implant placement with customized barium-coated diagnostic/surgical templates, internal precision www.indiandentalacademy.com
milled cylinders, external guide wires with a CT scan, and interactive software to facilitate improved presurgical implant diagnostics and prosthetically directed implant placement.
Fig. 1. Acrylic resin teeth luted in place and occlusion verified www.indiandentalacademy.com
Fig. 2. Buccal wire luted in place.
www.indiandentalacademy.com
Fig. 3. Cross-sections in SIM/Plant of desired sections. Frame 37 demonstrates buccal wire (arrow). www.indiandentalacademy.com
Fig. 4. Implant replica placed at ideal angulation. www.indiandentalacademy.com
Fig. 5. A, Angulation to buccal wire is calculated. B, Linear relationship to buccal wire is calculated. www.indiandentalacademy.com
Fig. 6. A, Modified surveyor table is adjusted to correct buccal-lingual and mesiodistal angulation as determined from SIM/Plant. Protractor is used to determine angle on surveyor table. B, Finalized position of surveyor table spatially. www.indiandentalacademy.com
Fig. 7. A, Cylinders fixed in proper position with guide pins to verify alignment. B, Final implant placement. www.indiandentalacademy.com
Fig. 8. A, Prepared abutments. B, Provisional restoration. www.indiandentalacademy.com
Tomography Diagnostic templates for tomography examinations are generally less precise than those required in CT examinations. The diagnostic information available from tomography examinations is not as detailed or as a precise as that available from CT examinations. The simplest tomography template is produced by obtaining a vacuform of the patient’s diagnostic cast with 3-mm. ball bearing placed at the proposed implant positions. A number of tomograms of the implant region are produced with the implant site identified by the one in which the ball bearing is in sharp focus. The ball bearing can additionally serve as www.indiandentalacademy.com a measure of the magnification of the imaging system.
Templates that incorporate metal cylinder or tubes at the proposed implant sites also enable evaluation of tomograms for the orientation along with the position of the proposed implant. Surgical templates Diagnostic templates can be modified and used as surgical templates. If metamorphosis from diagnostic template to surgical template is the objective of the surgeon, the diagnostic template should be selected and fabricated with that in mind.
www.indiandentalacademy.com
CAD CAM stereotactic surgical templates Anatomically accurate three-dimensional models of the patient’s alveolar anatomy can be produced by a number of cadcam and rapid prototyping procedures. Cadcam surgical stereotactic templates can be produced from CT examinations that have used interactive CT to develop a three-dimensional treatment plan for the patient of the position and orientation of dental implants. A stereotactic surgical template is derived from the model by aligning guide cylinders at the implant sites, which just accommodate a pilot drill, and producing a vacuform using surgical template material of the model www.indiandentalacademy.com and guide cylinders. This results in a plastic surgical
template that fits and conforms to patient’s bony anatomy and supports the position and orientation of the guide cylinders, which precisely reproduce the position and orientation of the proposed implants.
www.indiandentalacademy.com
Surgical and Interventional imaging Surgical and interventional imaging involves imaging the patient during and immediately after surgery, and during the placement of the prosthesis. The purpose of surgical imaging is to evaluate the depth of implant placement, the position and orientation of implants/osteotomies, and to evaluate donor or graft sites. The patient can be generally imaged at chair side with periapical radiography to determine implant osteotomy depth position, and orientation. Corrections for magnification, similar to those employed in endodontics, are necessary to quantify the www.indiandentalacademy.com depth of the osteotomy. The disadvantage of
periapical radiography is that a darkroom and approximately 5 minutes per radiograph for film processing is generally required. Digital periapical image receptors enable virtually instantaneous image acquisition, produce image quality similar to that of dental film, and enable the surgical procedure to proceed without undue delay. For extensive implant procedures that may involve the entire jaw, both jaws, large donor graft sites, or sinus graft augmentation panoramic radiography will provide a more global view of the patient’s anatomy. Periapical or digital periapical radiography are useful modalities to determine if the implant components and prosthesis are seatedwww.indiandentalacademy.com or fitted appropriately.
The anti-rotation devices of the implant body may prevent the abutment form seating in the correct position. This may be difficult to ascertain because the implant crest module is often at the bone crest and the tissue is several millimeters thick. An x-ray examination is also performed to determine if the metal framework and or final restoration is completely seated, and the margins are acceptable around the implants and/or teeth. The important portion to image is the crestal aspect of the implant not the apex.
www.indiandentalacademy.com
Post-prosthetic imaging The purpose of post prosthetic implant imaging is to evaluate the status and prognosis of the dental implant. The bone adjacent to the dental implant should be evaluated on a routine basis for changes in mineralization or bone volume. Loss of cylindrical bone volume adjacent to the implant surface may indicate excessive axial or shear loading, bone damage during implant placement, integration failure with an epithelial bone implant interface, inflammation, and/or infection. www.indiandentalacademy.com
Periapical radiography The implant bone interface is depicted only at the mesial, or distal, inferior, and crestal aspects or, where the central ray the x-ray source is tangent to the implant surface. Other regions of the implant interface are simply not depicted well by this modality. Bite-wing radiographs The short and long-term evaluation of crestal bone loss around implants is best evaluated with intraoral radiographs. Threaded implants make qualification of marginal bone loss easier to read. Most threaded implants have a smooth crestal region that measures 0.8 towww.indiandentalacademy.com 2 mm, depending on the
manufacturer, before the threads begin. Once the threads begin, there is a consistent pitch (distance between the threads). As a result, the amount of crestal bone loss can be determined when compared to the original implant insertion and initial radiograph of the prosthesis. The image is optimal when the implant body threads can be seen clearly on both sides.
www.indiandentalacademy.com
Temporal digital subtraction radiography Temporal digital subtraction radiography (SR) is a radiographic technique that enable 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. The resulting substraction image depicts changes in the patient’s anatomy such as alveolar mineralization or volume changes during the time between which the two radiographs were made. In addition to identifying mesial and distal changes in the alveolar bone, SR can also depict buccal and lingual changes in alveolar bone. SR has had limited utilization in clinical practice because of the difficulty in www.indiandentalacademy.com obtaining reproducible periapical radiographs.
Computed tomography Although CT cannot match the resolution of SR or periapical radiography, the quantitative gray scale and three-dimensional characteristics of CT enable evaluation of the bone implant interface in all orientations. Failing implants characterized by trabecular and crestal demineralization; resorption of the bone implant interface; cortical plate fenestration; and perforation of the inferior alveolar canal cortical plates, and nasal cavity or maxillary sinus floor can be identified with CT. The three dimensional imaging capabilities of CT enable precise evaluation of the position of dental implants relative to www.indiandentalacademy.com critical structures such as the
inferior alveolar canal, the mental foramen, maxillary sinus, nasal cavity incisive foramen, anterior loop, adjacent teeth, buccal or lingual cortical plates, and so on.
www.indiandentalacademy.com
Review of Literature 1. Siu AS, Li TK, Chu FC, Comfort MB, Chow TW ( 2003) A new contrast medium, Lipiodol ethiodized oil (Laboratoire Guerbet, Paris, France), can easily be mixed with the monomer of autopolymerizing acrylic resin. The resultant acrylic template has several advantages. the radiopaque template is optically transparent (with a slight yellow tint), which facilitates good visibility of surgical sites when the template is modified to become the surgical guide for implant placement. Implant Dent. 2003;12(1):35-40. www.indiandentalacademy.com
2.
Kopp
KC,
Koslow
AH,
Abdo
OS.(
2003)
The technique described facilitates precise dental implant placement. A barium-coated template with external guide wires used in conjunction with a computed tomography scan and interactive software may provide superior presurgical diagnostics, treatment planning, and prosthetically directed implant placement. Measurements predetermined on the computed tomography scan can be transferred accurately to the diagnostic/surgical template by use of a precision milled cylinder placed into the template at the proper angulation and linear dimensions. The diagnostic/surgical template shows the surgeon the www.indiandentalacademy.com optimal position for implant placement, thus
establishing greater clinical confidence when placing implants. (Predictable implant placement with a diagnostic/surgical template and advanced radiographic imaging.) J Prosthet Dent. 2003 Jun;89(6):611-5.
www.indiandentalacademy.com
3. Dov Along et al (2001) described fabrication of imaging and surgical guides for dental implants. They concluded that the circumference guide only traces the outline of the planned prosthesis; it does not provide necessary transposition of prosthetic and/ or bone angulation information. The vertical lead strip and gutta-percha guides serve primarily as imaging indicators and allow for some surgical latitude in preparation of osteotomy sites. The metal sleeve guide used in conjunction with a set up disk appears to be the most accurate imaging and surgical guide. It serves as an imaging and a precision surgical osteotomy guide, ensuring consistency between the www.indiandentalacademy.com
planned prosthetic angulation (confirmed by diagnostic imaging) and the trajectory of osteotomy during the surgical phase. JPD 2001:85:504-508. 4. Aryatawong S, Aryatawong K. (2000). The aim of their study was to evaluate the possibility of locating the inferior alveolar canal (IAC) before mandibular posterior osteotomy or implant surgery using a computer-controlled hypocycloidal tomographic system. The visibility of the IAC was graded as excellent or good in 74% and fair in 11.7% of the sites. In 14.3% of cases, the canal was graded as invisible. Conventional hypocycloidal tomography has been shown to be a useful radiographic technique www.indiandentalacademy.com for preoperative assessment of the IAC in the
posterior mandible. (Evaluation of the inferior alveolar canal by cross-sectional hypocycloidal tomography.). Implant Dent. 2000;9(4):339-45. 5. Cehreli MC, Aslan Y, Sahin S. (2000). In this article, the fabrication of a bilaminar dual-purpose stent that facilitates ease in implant placement with improved verification of implant positioning is described. The outer lamina is designed for use in the computed tomography evaluation, using radiopaque markers. The verification of implant alignment and positioning, according to the determined prosthesis, is also performed with this template after modifying it for surgery. The inner lamina is designed www.indiandentalacademy.com to accept 2 removable surgical
acrylic resin stents with different guide channels that avoids the risk of surgical malpractice. J Prosthet Dent. 2000 Jul;84(1):55-8. 6. Dov M. Almog, Rodolfo Sanchez. (1999) evaluated correlation between planned prosthetic and residual bone trajectories in dental implants. They used tomographic survey in conjunction with imaging guides. They found that the discrepancies between the planned prosthetic and the residual bone trajectories were greater in the mandibular molar area. J Prosthet Dent 1999: 81:5: 562.
www.indiandentalacademy.com
7. Cem Devge et al (1997). Studied magnetic resonance imaging in patients with dental implants. They concluded that a patient with intra oral or extra oral Branemark implants may be exposed to an MRI examination without any risk. The resulting artifacts are minor. If the patient has any fixation magnets or magnet keepers attached to the implants or the prosthesis for its retention, these should be temporarily removed not only to avoid major artifacts, but also to eliminate the risk of implant loss. IJOMI 1997: 12:3:354-359
www.indiandentalacademy.com
8. Gray CF, Redpath TW, Smith FW (1996). Unlike computerized tomography (CT) and other xradiographic techniques, MRI uses no ionizing radiation, and is capable of angulating and offsetting its scan plane at will. Good bone detail is available because cancellous bone yields a strong signal from the marrow fat, while cortical bone and dental enamel are dark. The excellent anatomic detail provided by thin-slice highresolution MRI allows for assessment of the suitability of sites to receive an implant in terms of bone quality and thickness, and the relative position of the site to important structures such as the inferior dental nerve and nasal sinuses. J Oral Implantol. 1996;22(2):147-53. www.indiandentalacademy.com
9. Takeshita F, Suetsugu T (1996). This article describes a method of fabricating a template with a stainless steel tube sprue for accurate radiographic evaluation and implant placement. Stainless steel tube sprues are inexpensive, indicate the eventual implant inclination, and facilitate precise placement, from the CT scan without any interference from scattered radiation. J Prosthet Dent. 1996 Dec;76(6):590-1.
www.indiandentalacademy.com
10. Lam E.W Reprecht and Yang (1995). Panoramic radiography and 2-D orthoradially reformatted CT images were used to measure bone height in the mandible and maxillae of patients undergoing preoperative assessments for dental implant placement. The greatest differences between the two techniques occurred in instances in which the use of dental implants would be particularly advantageous, that is in regions with less than 15 mm of remaining bone. JPD 1995:74:42-46.
www.indiandentalacademy.com
11. Basten CH. ( 1995) The computer tomogram prepared with the aid of the radiopaque template allows the evaluation of the implant sites in relation to the outline of the planned restoration. The radiographic template is converted into the surgical template, which contains information regarding the optimal position and angulation of implants. Because the surgical template is a modification of the radiographic template, which rests rigidly on the teeth during all procedures, implant placement is more predictable. Quintessence Int. 1995 Sep;26(9):609-12. www.indiandentalacademy.com
12.TanKB.(1995). Besides the basic clinical examination and the use of mounted study models, radiographic imaging is an essential adjunctive aid in treatment planning. The latest imaging modality, multiplanar reformatted CT (MPR-CT) is the most comprehensive and accurate presently available. It allows precise assessment of the three-dimensional architecture and internal anatomy of the jaws. This enables accurate preoperative evaluation for planning implant fixture placement with maximal use of bone. The use of radiographic stents (with radiographic markers incorporated) derived from diagnostic wax-ups or setups is essential. This provides reference points to determine the available bone at the exact spatial www.indiandentalacademy.com location and orientation of the planned implant fixture
at all primary and alternate sites. The same radiographic stent is then converted to a surgical guide stent for precise location of surgical implant sites. Ann Acad Med Singapore. 1995 Jan;24(1):68-75. 13. Ludlow JB, Nason RH Jr, Hutchens LH Jr, Moriarty J. (1995). This study evaluated the diagnostic accuracy of periapical, tomographic, and crosssectional occlusal radiographic techniques in the assessment of facial and lingual bone loss at implant obscured sites. Cross-sectional occlusal views provided significantly greater mean observer confidence scores than either periapical images or tomograms (P < .01). However, tomograms may provide greater utility in actual clinicalpractice. Implant Dent. 1995 www.indiandentalacademy.com Spring;4(1):13-8.
14. Siddiqui AA, Caudill R, Beatty K. (1995) A technique for the measurement of bone loss around endosseous implants using an optical comparator was investigated. The bone loss around the implant was calculated by taking the average of the mesial and distal measurements. Statistical analysis at the 95 percent confidence level demonstrated that there was no significant difference among the measurements. Although the initial results are encouraging, additional research is necessary with a larger sample size to validate theaccuracy of optical comparator readings and compare the efficacy of this technique with other currently used methods for determining bone loss around root form implants. Implant Dent. 1995 Summer;4(2):85-8. www.indiandentalacademy.com
15. Lawrence A Weinberg (1993). In his article, â&#x20AC;&#x153;CT scan as a radiologic data base for optimum implant orientationâ&#x20AC;? concluded that optimum orientation is aided by the three-dimensional radiologic database provided by a CT scan. JPD 1993: 69: 381-385 16. Modica, et al (1991) described an original prosthetic planning involving CT scan. They summarized that the use of the CT scan as a diagnostic aid provides a three dimensional study of the bone and a specially developed positioner device estimates the position, angulation and depth of the fixtures to be implanted. J Prosthet dent. 1991:65:541-546 www.indiandentalacademy.com
17. Michael J. Engelman et al (1988). The average surface dose of a tomographic exposure is 1 to 6 m rad or 50 m rads per tomographic examination. This is less than the exposure of a normal full mouth radiographic survey. A CT scan has a radiation exposure of two rads per slice or many times the dose of a conventional tomographic examination. The tomogram provides a more accurate image of the quantity and quality of the osseous structures. Through careful planning and systematic control, the predictable placement of osseointegrated implants can be achieved. J Prosthet dent 1988:59:4:467-473. www.indiandentalacademy.com
18. Ramuald J. Fernadez et al (1987) evaluated a cephalometric tomographic technique to visualize the buccolingual and vertical dimensions of the mandible. The results of this study demonstrate the following, a. A uniquely designed cephalostat in conjunction with an intra oral section indicating jig may be used to visualize and measure true buccolingual and vertical dimensions of an edentulous mandible. b. Images of similar bone regions or sections were proved to be reproducible with accuracy not obtainable by other radiographic techniques. JPD 1987:58:466-470 www.indiandentalacademy.com
19.
Harold P. Truitt et al (1986). Studied the feasibility of the use of computerized tomographic scanner data in solid modeling of a specimen of dry human skull. They concluded that it is highly accurate and usable three-dimensional database for use in solid modeling. J. Prosthet Dent. 1986:44:494-7.
www.indiandentalacademy.com
References 1. Contemporary implant dentistry. Carl E Misch. Second edition. 2. Atlas of dental and maxillofacial radiology and imaging. Roger M Brown, Hugh D Edmondson, P G John Rout. 1995. 3. Current oral and maxillofacial imaging. Razmus, Williamson. 1996. 4. Essentials of dental radiography and radiology. Eric Whaites. Third edition. 2002. Michael J. Engelman et al. Optimum placement of osseointegrated implants. J Prosthet dent 1988:59:4:467-473. www.indiandentalacademy.com
5. Harold P. Truitt et al. Non invasive technique for mandibular subperiosteal implant. A preliminary report. J Prosthet Dent. 1986:44:494-7. 6. Ramuald J. Fernadez et al. A cephalometric tomographic technique to visualize the buccolingual and vertical dimensions of the mandible. J Prosthet Dent 1987:58:466-470 7. Cem Devge et al. Magnetic resonance imaging in patients with dental implants. A clinical report. IJOMI 1997: 12:3:354-359
www.indiandentalacademy.com
8. Lam E.W Reprecht and Yang. Comparison of two dimensional orthoradially reformatted computed tomography and panoramic radiography for dental implant treatment planning. J Prosthet Dent 1995:74:42-46. 9. Lawrence A Weinberg. CT scan as a radiologic data base for optimum implant orientation. J Prosthet Dent 1993: 69: 381-385 Dov M 10. Almog, Rodolfo Sanchez. Correlation between planned prosthetic andresidual bone trajectories in dental implants. J Prosthet Dent 1999: 81:5: 562.
www.indiandentalacademy.com
11. Modica, et al. Radiologic prosthetic planning of the surgical phase of the treatment of edentulism by osseointegrated implants. An invitro study. J Prosthet Dent 1991:65:541-546 12. Dov Along et al. Fabrication of imaging and surgical guides for dental implants. J Prosthet Dent 2001:85:504-508. 13. Kopp KC, Koslow AH, Abdo OS. Predictable implant placement with a diagnostic/surgical template and advanced radiographic imaging.) J Prosthet Dent. 2003 Jun;89(6):611-5. www.indiandentalacademy.com
14. Siu AS, Li TK, Chu FC, Comfort MB, Chow TW. The use of lipiodol in spiral tomography for dental implant imaging. Implant Dent. 2003;12(1):35-40. 15. Basten CH. The use of radiopaque templates for predictable implant placement. Quintessence Int. 1995 Sep;26(9):609-12 16. Aryatawong S, Aryatawong K. Evaluation of the inferior alveolar canal by cross-sectional hypocycloidal tomography. Implant Dent. 2000;9(4):339-45. 17. Tan KB. The use of multiplanar reformatted computerised tomography in the surgicalprosthodontic planning of implant placement.) Ann Acad Med Singapore. 1995 Jan;24(1):68-75. www.indiandentalacademy.com
18.
Siddiqui AA, Caudill R, Beatty K. Use of an optical comparator for radiographic measurement of bone loss around endosseous implants: a pilot study. Implant Dent. 1995 Summer;4(2):85-8.
19. Ludlow JB, Nason RH Jr, Hutchens LH Jr, Moriarty J. Radiographic evaluation of alveolar crest obscured by dental implants. Implant Dent. 1995 Spring;4(1):13-8. 20. Gray CF, Redpath TW, Smith FW. Pre-surgical dental implant assessment by magnetic resonance imaging. J Oral Implantol. 1996;22(2):147-53. www.indiandentalacademy.com
21. Takeshita F, Suetsugu T. Accurate presurgical determination for implant placement by using computerized tomography scan. J Prosthet Dent. 1996 Dec;76(6):590-1. 22. Cehreli MC, Aslan Y, Sahin S. Bilaminar dualpurpose stent for placement of dental implants. J Prosthet Dent. 2000 Jul;84(1):55-8.
www.indiandentalacademy.com
www.indiandentalacademy.com Leader in continuing dental education
www.indiandentalacademy.com