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radiological evaluation in oral implantology


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Maximizing the ratio of benefit to risk for imaging examinations is a fundamental tenet of radiology.:

Maximizing the ratio of benefit to risk for imaging examinations is a fundamental tenet of radiology. -Carl. E. Misch

Radiological evaluation helps develop and implement a cohesive and comprehensive treatment plan for the implant procedure. :

Radiological evaluation helps develop and implement a cohesive and comprehensive treatment plan for the implant procedure.

Slide 4:

Radiological evaluation & Imaging PHASE I Pre-surgical implant imaging. PHASE II Surgical & Intra-operative implant imaging. PHASEIII Post-prosthetic implant imaging.

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PHASE I Involves all past & new radiologic examinations to determine Quantity , quality & angulations of bone. The relationship of different structures to the perspective implant site. Pathological consideration of the implant site.

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PHASE II Provides assistance in surgical & prosthetic intervention of patient by focusing on Evaluation of surgical sites during & immediately after surgery Assistance in the optimal position & orientation o f implants Evaluation of healing & integration phase of implant surgery Ensuring correct abutment position & prosthetic fabrication.

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PHASE III Commences after prosthesis placement as long as implants remain in jaws. Objectives are to Evaluate the long-term maintenance of implant rigid fixation & crestal bone levels Evaluate the implant complex.

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TYPES OF IMAGING MODALITIES Periapical radiography Panoramic radiography Occlusal radiography Analog Cephalometric radiography Tomographic radiography Computed tomography Magnetic resonance imaging Interactive computed Digital tomography.

Slide 9:

DIGITAL RADIOGRAPHY It is an imaging process wherein a film is placed by sensor that collects data. The analog image received is then interpreted by software & image is formulated on computer monitor. DIGITAL RADIOGRAPHIC SYSTEM

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FILM DIGITAL Analog image High radiation Viewing delayed 14-18Ln/mm 16 shades in gray-scale Unchangeable enhancement Storage in charts Analog-digital 50-90% less Immediate 12-20Ln/mm 256 shades in gray-scale Wide range Storage in computer.

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SELECTION OF RADIOGRAPHIC MODALITY ALARA Principle As low as reasonably achievable Dental implant cases are inherently three-dimensional problems relating to final prosthetics, occlusion & function of patient’s three-dimensional anatomy.

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PERAPICAL RADIOGRAPHS Periapical radiographs are produced by placing film intraorally parallel to the alveolus , central ray perpendicular to alveolus thus producing its lateral view & no cross-sectional information.

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Long cone paralleling technique eliminates distortion & limits magnification to less than 10%. The film is placed parallel to the long axis of the implant or tooth.

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When the x-ray beam is kept perpendicular to the film but the object isn’t parallel to the film, foreshortening will occur.

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If x-ray beam is oriented perpendicular to the object but not the film, elongation will occur.

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Image magnification can be assessed by placing a known-dimension marker like a 5mm ball bearing at crestal region. Burnout effects are common with standard kilovolt & milliampere settings while assessing bone density & crestal bone loss. Due to presence of dense cortical plates in lateral mandible & palatal side of maxilla, bone quality is difficult to assess.

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INDICATIONS Evaluation of small edentulous spaces. Alignment & orientation during surgery. Recall / maintenance evaluation.

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ADVANTAGES Low radiation dose Minimal magnification with proper alignment & positioning High resolution Inexpensive.

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DISADVANTAGES Distortion & magnification Minimal site evaluation Difficulty in film placement Technique sensitive Lack of cross-sectional imaging.

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OCCLUSAL RADIOGRAPHY Planar radiographs taken by placing film intraorally parallel to the occlusal plane with central ray perpendicular to film for mandible & about 45* oblique for maxilla.

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Maxillary radiographs are inherently oblique & distorted so don’t work well in implantological evaluation. Also, critical structures like maxillary sinus, nasal cavity & naso-palantine canal are demonstrated but spatial relation to implant site is generally lost during projection.

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Mandibular occlusal radiographs show the widest width of bone ( symphysis ) versus crestal width. Also degree of mineralization of trabecular bone isn’t determined.

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Rarely indicated for implant evaluation. ADVANTAGES Evaluation for pathology. DISADVANTAGES Does not reveal true bucco -lingual width in mandible. Difficulty in positioning.

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CEPHALOMETRIC RADIOGRAPHY Cephalometric radiograph is an oriented planar image of skull. The geometry of these devices results in 10% magnification of image with 60” focal object & 6” object to film distance.

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It is produced with patient’s mid-sagittal plane oriented parallel to image receptor. It demonstrates a cross-sectional image of alveolus . This image demonstrates spatial relationship between occlusion & esthetics with length, width, angulation, geometry of alveolus & relationship of lingual plate to patient’s skeletal anatomy. Implants often must be placed adjacent to lingual plate in anterior regions.

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It also helps to evaluate a loss of vertical dimension, skeletal arch interrelationship, anterior crown/ implant ratio, soft tissue profile, anterior tooth position in prosthesis. However, it is not useful for demonstrating bone quality & only demonstrates a cross-sectional image of alveolus.

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INDICATIONS Used in combination with other techniques for anterior implants. Symphysis bone graft evaluation.

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ADVANTAGES Height/width in anterior region Low magnification Skeletal relationship Crown-implant ratio (anterior) Tooth evaluation in prosthesis Evaluation of quantity of bone in anterior region prior to symphysis grafting.

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DISADVANTAGES Availability Image information limited to mid-line Reduced resolution & sharpness Technique sensitive.

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PANORAMIC RADIOGRAPHY It is a curved plane tomographic radiographic technique. It is probably the most used diagnostic modality. It is not the most diagnostic for presurgical imaging.

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It is characterized by a single image of jaws that demonstrates vertical & horizontal magnification, along with a tomographic section thickness that varies with anatomical position.

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It produces a constant vertical magnification of approx 10% and a horizontal magnification of approx 20% & variable depending upon the anatomical location. Structures of jaws become magnified more as the object-film distance increases & object-x-ray source distance decreases.

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Uniform magnification of structures produces images with distortion that cannot be compensated for treatment planning. The posterior maxillary region is generally the least distorted region of a panoramic radiograph. Diagnostic templates like a 5mm ball bearing incorporated around the dental arch & worn by the patient enables to determine the amounts of magnification.

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Studies demonstrate that mandibular foramen cannot be identified 30% of the times & when visible may be identified incorrectly. The maxillary anterior edentulous region is oblique to the film & most difficult to evaluate.

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ADVANTAGES Easy identification of opposing landmarks. Initial assessment of vertical height of bone Convenience, ease & speed in performance Evaluation of gross anatomy of the jaws & any associated pathologies.

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DISADVANTAGES Distortions inherent in panoramic system Error in patient positioning Does not demonstrate bone quality Misleading quantitatively because of magnification & no third dimension No spatial relationship between structures.

Slide 37:

A modification of panoramic image has been developed for making cross-sectional images of jaws. These devices use limited-angle linear tomography ( zonography ). This enables appreciation of spatial relationship between critical structures & implant site & quantification of geometry of implant site.

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TOMOGRAPHIC RADIOGRAPHY Here the x-ray tube & film are connected by a rigid bar called Fulcrum bar. When system is energized, the x-ray tube moves in one direction & the film in the opposite & system pivoting around the fulcrum. Different tomographic sections are produced by adjusting position of fulcrum or the patient.

Slide 39:

For dental implant patients high-quality tomography demonstrates alveolus & enables quantification of its geometry. It also enables determination of spatial relationship. Ideally, tomographic sections spaced every 1 to 2mm enable evaluation of implant site & three- dimensional appearance of alveolus.

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INDICATIONS Single-site evaluation Vital structure evaluation ADVANTAGES Cross-sectional imaging Constant magnification.

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LIMITATIONS Availability Cost Multiple images needed Technique sensitive B lurred images High radiation dose

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COMPUTED TOMOGRAPHY It is a digital & mathematical imaging technique that creates tomographic sections without adjacent blurring of sections. It enables quantification & differentiation of hard & soft tissues.

Slide 43:

CT was invented by Hounsfield & was announced to the imaging world in 1972. The x-ray source is attached rigidly to a fan-beam geometry detector array, which rotates 360* around patient & produces axial images of patient’s anatomy.

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CT images are inherently three-dimensional digital images, typically 512x512 pixels with a thickness described by slice spacing. The individual element of CT image is called a voxel , which has a value referred in Hounsfield units, that describes density of image . Each voxel contains 12 bits of data & ranges from -1000 to +3000 hounsfield units.

Slide 45:

BONE DENSITY HOUNSFIELD UNITS D1 1250 D2 850-1250 D3 350-850 D4 150-350 D5 <150

Slide 46:

The utility of CT in implant dentistry became evident after the development of DENTASCAN IMAGING technique. DentaScan imaging provides programmed reformation, organization & display of imaging study. The radiologist simply indicates the curvature of the mandibular or maxillary arch & computer is programmed to generate referenced cross-sectional & panoramic images of the alveolus with three-dimensional image of the arch.



Slide 48:

This technique provides a wealth of diagnostic information which is accurate, detailed & specific. Usually a diagnostic template may be used to take full advantage of this technique as it enables to incorporate the three-dimensional treatment plan of final prosthetic result into imaging examination.

Slide 49:

INDICATIONS Interactive treatment planning Determination of bone density Vital structure location Subperiosteal implant fabrication Determining pathologies Preplanning for bone augmentation.

Slide 50:

ADVANTAGES Negligible magnification Relatively high-contrast image Various views Three-dimensional bone models Interactive treatment planning Cross-referencing . LIMITATIONS Cost Technique sensitive

Slide 51:

INTERACTIVE COMPUTED TOMOGRAPHY It is a technique that was developed to enable the radiologist to transfer the imaging study to practitioner as a computer file. The dentist can measure the length & width of alveolus, bone density, can appreciate axial, cross-sectional, panoramic & three-dimensional images in his computer.

Slide 52:

ICT is the most accurate imaging Technique for implant imaging & Surgery.

Slide 53:

An important feature of ICT is ELECTRONIC SURGERY wherein patient’s treatment plan can be developed electronically in three-dimension by selecting & placing arbitrary-sized cylinders that simulate root-form implants in images.

Slide 54:

MAGNETIC RESONANCE IMAGING It is a CT imaging technique that produces images of thin slices of tissue with excellent resolution. It was developed by Lauterbur in 1972 using a combination of magnetic fields to generate images without using ionizing radiation. The images created are a result of signals generated by hydrogen-protons in water or fat.

Slide 55:

Cortical bone will appear black (radiolucent) having no signal. Cancellous bone will generate signal & appear white because it contains fatty marrow. MRI can be used in implant imaging as secondary technique when CT , ICT fail. For example- Differentiating Inferior alveolar canal. MRI visualizes fat in trabecular bone & differentiates canal from bone & neurovascular bundle.

Slide 57:

INDICATIONS Evaluation of vital structures when CT is not conclusive Evaluation of infection ADVANTAGES No radiation Vital structures are easily seen (maxillary sinus)

Slide 58:

LIMITATIONS Cost Technique sensitive No reformatting software Availability Nonsignal for cortical bone

Slide 59:

RADIOGRAPHIC IMAGING OF VITAL STRUCTURES IN IMPLANTOLOGY MENTAL FORAMEN & MANDIBULAR CANAL Position of mental foramen & mandibular canal must be evaluated for implants in posterior mandible to avoid trauma to the Inferior alveolar nerve. Periapical & panoramic images are still used as sole determinate.

Slide 60:

In periapical radiographs usually lack of identification occurs due to lack of cortical bone around the mandibular canal. In edentulous mandibles, the risk of error increases where there is resorption of alveolar crest. CT is the most accurate & recommended imaging modality for exact location of Inferior alveolar canal & mental foramen.

The Inferior alveolar nerve & mental foramen can be marked in CT image & transferred to various views.:

The Inferior alveolar nerve & mental foramen can be marked in CT image & transferred to various views.

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MANDIBULAR LINGUAL CONCAVITIES In case with advanced atrophy in posterior mandible, lingual concavities may be present & must be evaluated. Within these , facial artery may be present & overestimation of bone during drilling may lead to perforation of lingual plate.

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Cross-sectional tomography is recommended.

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MANDIBULAR RAMUS (DONOR SITE FOR AUTOGENOUS GRAFTING) This area of mandible is extremely variable in amount of bone present. During pre-assessment, location of external oblique ridge & mandibular canal should be noted.


COMPUED TOMOGRAPHY GIVES ACCURATE REPRESENTATION. The more p rominent the e xternal oblique r idge, the better c andidate for the Ramus as donor s ite.

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MANDIBULAR SYMPHYSIS It is a very critical area for implant placement & donor for autogenous grafting. An imaging technique that depicts true bucco -lingual amount of bone is recommended. Lateral cephalometric & conventional CT may be used.

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Accurate assessment of bucco -lingual w idth of bone is required.

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MAXILLARY SINUS During pre-assessment it is very important to have a detailed information regarding prevalence & position of septa, maxillary sinus anatomy , detection of sinus pathology. No radiographic modality gives more information of paranasal sinuses than CT.

Slide 69:

RADIOGRAPHIC SEQUENCE FOR DENTAL IMPLANTS Pretreatment Immediate post-surgical (baseline) Healing period Second-stage surgery Post-prosthetic (baseline) 1 year postoperatively After 1 st year, every 2 yearly



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