Establishment of prognostic evaluation of dental implants by standardized digital radiography

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The purpose of this study was to determine the optimal radiation dose and image processing conditions for radiography using a digital radiographic system, develop auxiliary instruments allowing safe, simple, and geometrically reproducible radiography for the assessment of implant outcomes using this digital radiographic system and evaluate the possibility of digital subtraction. Implant fixtures were inserted into molar defects of cadaver mandibular bone, and bone defects (1-3 mm) were produced around the fixture and examined by radiography using a digital radiographic system (Digora) and dental X-ray films (Ektaspeed Plus). The Digora allowed detection of bone defects of 2 mm or more with a radiation time of 0.5 seconds and was superior to the Ektaspeed Plus in terms of sensitivity, specificity, and accuracy. Even after a reduction of the radiation dose to 1/5, the detection ability did not markedly decrease, suggesting that a reduction in dose is possible. As auxiliary instruments for standard radiography, the face-bow transfer used for occlusal registration was improved, and reproducible radiography became possible. For radiography, a direct digital system (CDR) was used, and some types of bone chips were placed in the molar area of dry skulls so as to add bone changes. On each image, subtraction was performed using software for digital subtraction (Emago) with automatic superposition function. Evaluation of images showed a higher accuracy of the CDR than conventional dental films. This method using software for digital subtraction (Emago ) and our new auxiliary instrument may be useful for serial observation of implant outcomes.