Presentation on theme: "Diagnostic Imaging and Techniques The objectives of diagnostic imaging depend on a number of factors, including the amount and type of information."— Presentation transcript:
Diagnostic Imaging and Techniques
The objectives of diagnostic imaging depend on a number of factors, including the amount and type of information required and the time period of the treatment rendered. Identify disease Determine bone quality Determine bone quantity Determine implant position Determine implant orientation Phase one is termed preprosthetetic implant imaging Phase two is termed surgical implant imaging 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 that abutment position and prosthesis fabrication are correct. Phase three is termed postprosthetic implant imaging. This phase 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.
IMAGING MODALITIES The imaging modality is used that yields the necessary diagnostic information related to the patient's clinical needs and results in the least radiologic risk. Cost-benefit Types of Imaging Modalities Periapical radiography (analog) Panoramic radiography (analog) Occlusal radiography (analog) Cephalometric radiography (analog) Tomographic radiography Computed tomography (three-dimensional) Magnetic resonance imaging (three-dimensional) Interactive computed tomography (three-dimensional)
PREPROSTH ETIC IMAGING Subdivided into planar two-dimensional, quasi three-dimensional, and three-dimensional imaging modalities. ALARA : as low as reasonably achievable 95% just panoramic, <15% conventional CT
Periapical Radiography Periapical radiography provides a high-resolution planar image of a limited region of the jaws.' No. 2 size dental film provides a 25 x 40-mm view of the jaw with each image. The long cone paralleling technique eliminates distortion and limits magnification to less than 10%. The opposing landmark of available bone in implant dentistry is beyond lingual muscle attachments in the mandible or beyond the palatal vault in the maxilla. (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 bone changes); and (4) of value in identifying critical structures but of little use in depicting the
For example, a ball bearing radiographic measurement of 8 mm relates to a 60% magnification. Therefore the image below the ball bearing may represent a 60% magnification of dimension Advantages Low radiation dose Minimal magnification with proper alignment and positioning High resolution Inexpensive Limitations Distortion and magnification Minimal site evaluation Difficulty in film placement Technique sensitive Lack of cross-sectional imaging Indications Evaluation of small edentulous spaces Alignment and orientation during surgery Recall/maintenance evaluation
A disadvantage of digital radiography is the size and thickness of the sensor and the position of the connecting cord. These features make the positioning of the sensor more difficult in some sites such as those adjacent to tori or a tapered arch form in the region of the canines
Occlusal Radiography Occlusal radiographs are planar radiographs produced by placing the film intraorally parallel to the occlusal plane with the central x-ray beam perpendicular to the film for the mandibular image and oblique (usually 45 degrees) to the film for the maxillary image. The mandibular occlusal radiograph shows the widest width of bone (i.e., the symphysis) The spatial relationship between critical structures, such as the mandibular canal and the mental foramen, and the proposed implant site is lost with this projection As a result, occlusal radiographs rarely are indicated for diagnostic preprosthetic phases in implant dentistry Advantages: Evaluation for pathology Limitations: Does not reveal true buccolingual width in mandible, Difficulty in positioning Indications: None
Cephalometric Radiography The geometry of cephalometric imaging devices results in a 10% magnification of the image A lateral cephalometric radiograph is produced with the patient's midsagittal plane oriented parallel to the image receptor Unlike panoramic or periapical images, the cross-sectional view of the alveolus demonstrates the spatial relationship between occlusion and esthetics with the length, width, angulation, and geometry of the alveolus and is more accurat for bone quantity determinations The width of bone in the symphysis region and the relationship between the buccal cortex and the roots of the anterior teeth also may be determined before harvesting this bone for ridge augmentation. cephalometric radiographs are a useful tool for the development of an implant treatment plan, especially for the completely edentulous patient This technique is not useful for demonstrating bone quality
Lateral Cephalometric Images Advantages Height/width in anterior region Low magnification Skeletal relationship Crown-implant ratio (anterior) Tooth position in prosthesis Evaluation of the quantity of bone in anterior region prior to symphysis grafting Limitations Availability Image information limited to midline Reduced resolution and sharpness Technique sensitive Indications Used in combination with other radiographic techniques for anterior implants Symphysis bone graft evaluation
Panoramic Radiography This technique used to depict the body of the mandible, maxilla, and the lower one half of the maxillary sinuses in a single image. This modality is probably the most used diagnostic modality in implant dentistry. For quantitative preprosthetic implant imaging, panoramic radiography is not the most diagnostic The x-ray source exposes the jaws from a negative angulation and produces a relatively constant vertical magnification of approximately 10%. The horizontal magnification is approximately 20% Structures of the jaws become magnified more as the object-film distance increases and the object x-ray source distance decreases. The posterior maxillary regions are generally the least distorted regions of a panoramic radiograph Diagnostic templates that have 5-mm ball bearings or wires incorporated around the curvature of the dental arch and worn by the patient during the panoramic x-ray examination enable the dentist to determine the amounts of magnification in the radiograph mandibular foramen cannot be identified 30% of the time on the x-ray film and when visible may not be identified correctly.The maxillary anterior edentulous region is generally oblique to the film and is often the most difficult area of a panoramic radiograph to evaluate
Objects in front of and behind the focal trough are blurred, magnified, reduced in size, or distorted to the extent of being unrecognizable when the canal runs lingual within the body, the position displayed on the film is more crestal compared with a nerve that is positioned more buccal, Zonography : The tomographic layer is approximately 5 mm. Advantages Easy identification of opposing landmarks Initial assessment of vertical height of bone Convenience, ease, and speed in performance in most dental offices Evaluation of gross anatomy of the jaws and any related pathologic findings' Limitations Distortions inherent in the panoramic system Errors in patient positioning Does not demonstrate bone quality Misleading quantitate because of magnification and no third dimension
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. The diagnostic quality of the resulting tomographic image is determined by the type of tomographic motion, the section thickness, and the degree of magnification. The type of tomographic motion is probably the most important factor in tomographic quality. Magnification varies from 10% to 30%, with higher magnification generally producing higher-quality images Ideally, tomographic sections spaced every 1 or 2 mm enable evaluation of the implant site Complex tomography is not particularly useful in determining bone quality or identifying dental and bone disease.
Computed Tomography CT enables differentiation and quantification of soft and hard tissues. CT produces axial images of a patient's anatomy. images are produced perpendicular to the long axis of the body Hounsfield units, that describes the density of the CT image at that point. Is quantitative and meaningful in identifying and differentiating structures and tissues. CT enables identification of disease, determination of bone quantity, determination of bone quality, 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 preprosthetic implant imaging Advantages: Negligible magnification, Relatively high-contrast image, Various views, Three-dimensional bone models, Interactive treatment planning, Cross-referencing Limitations: Cost, Technique sensitive Indications Interactive treatment planning Determination of bone density Vital structure location Subperiosteal implant fabrication Determination of pathology Preplanning for bone augmentation
Quality Density Hounsfield unit D D D D D5 <150 Tissue Characterization Tissue Hounsfield unit Air Water 0 Muscle Fibrous tissue Cartilage Trabecular bone Cortical bone Dentin Enamel
Interactive Computed Tomography ICT is a technique that was developed to bridge the gap in information transfer between the radiologist and the practitioner. This technique enables the radiologist to transfer the imaging study to the practitioner as a computer file and enables the practitioner to view and interact with the imaging study on a personal computer An important feature of ICT is that the dentist and radiologist can perform electronic surgery by selecting and placing arbitrary-size cylinders that simulate root-form implants in the images Diagnostic template
Cone Beam Volumetric Tomography new type of CT specific for dental applications The average absorbed radiation dose from a CBVT scanner (newTom 3G) is approximately 12.0 mSv (micro sieverts). This dose is equivalent to five D-speed dental x-rays or 25% of the radiation from a typical panoramic radiograph. medical scanner acquire images that use radiation doses of 40 to 60 times that of CBVT doses x-ray tube on these scanners rotates 360 degrees and will capture images of the maxilla and mandible in36 seconds, in which only 5.6 seconds is needed for exposure magnification being almost 0% with no superimposition or overlapping of images and minimal distortion
Magnetic Resonance Imaging Magnetic resonance imaging is a CT imaging technique that uses a combination of magnetic fields that generate images of tissues in the body without the use of ionizing radiation. Metal restorations will not produce scattering and thus will appear as black images. Therefore MRI has been shown to be less prone to artifacts from dental restorations, prostheses, and dental implants than CT MRI is used in implant imaging as a secondary imaging technique when primary imaging techniques such as complex tomography, CT, or ICT fail. MRI visualizes the fat in trabecular bone and differentiates the inferior alveolar canal and neurovascular bundle from the adjacent trabecular bone. MRI is not useful in characterizing bone mineralization or as a high-yield technique for identifying bone or dental disease
Magnetic Resonance Imaging Advantages No radiation Vital structures are easily seen (inferior alveolar canal, maxillary sinus) Limitations Cost Technique sensitive No reformatting software Availability Non signal for cortical bone Uses Evaluation of vital structures when computed tomography is not conclusive Evaluation of infection (osteomyelitis)
RADIOGRAPHIC IMAGING OF VITAL STRUCTURES IN ORAL IMPLANTOLOGY Mental Foramen and Mandibular Canal 50% of periapical radiographs, the mental foramen is not visible. the mental foramen is absent in approximately 12% of panoramic the most accurate means of identification is with conventional and computerized tomography tilting the patient's head approximately 5 degrees downward in reference to the Frankfort horizontal plane allows these anatomical structures to be seen in 91% of radiographs Mandibular Lingual Concavities 2.4% prevalence of concavities with average depths of 6 mm (±2.6 mm). Within these concavities or submandibular gland fossa, branches of the facial artery may be present. Mandibular Ramus very popular donor site for autogenous onlay bone grafting. Standard radiographs for preassessment include panoramic Mandibular Symphysis The mandibular symphysis area is a very critical anatomical area for oral implantology. Lateral cephalometric and conventional CT, may be used Maxillary Sinus CT
INTRAOPERATIVE IMAGING Advantages of Digital Radiography for Implant Surgery Fast Low radiation Calibration Magnification Excellent quality Measures depth, density, and neighboring structures Patient stays in surgical setting Keeps aseptic setting
Immediate Postsurgical Imaging A plain film radiograph (periapical or panoramic) should be taken postsurgically so that a baseline image may be used to evaluate against future films Abutment and Prosthetic Component Imaging Radiographs should be taken to verify secure adaptation. When positioning is difficult for periapical radiographs, bitewing or panoramic radiographs may be used Postprosthetic Imaging a panoramic radiograph is the most ideal imaging technique for multiple implants If single implants or if more detailed information concerning an implant viewed on a Panorex is needed, periapical radiographs Recall and Maintenance Imaging For the evaluation of implant success, immobility and radiographic evidence of bone adjacent to the implant. Follow-up or recall radiographs should be taken after 1 year of functional loading and yearly for the first 3 years
Evaluation of Alveolar Bone Changes Radiographically, lack or loss of integration is usually indicated as a radiolucent line around the implant. "Mach band effect" Mach band effect is significantly reduced with digital image processing. Periapical Radiographs Filmholding devices If the threads are not clearly seen in the radiographs, modification of the beam angle needs tobe made. If diffuse threads are present on the right side of the implant. then the beam angle was positioned too much in the superior direction. If the thread are diffuse on the left side, then the beam angle was from an inferior angulation Bitewing Radiograph.