DIGITAL IMAGE-PROCESSING .2. IN-VITRO QUANTITATIVE-EVALUATION OF SOFTAND HARD PERI-IMPLANT TISSUE CHANGES

The aim of this study was to evaluate the ability of computer-assisted densitometric image analysis (CADIA) to detect small changes in miner alized and nonmineralized tissues adjacent to dental implants and to c orrelate these changes with CADIA values. A section of a pig mandible including all soft tissues and in which a hollow cylinder ITI Bonefit( R) implant with an artificial mesial and a buccal infrabony defect was placed was used to obtain pairs of standardized radiographs. Series o f radiographs were obtained with exposure times of 0.13, 0.20, 0.44, a nd 0.53 s. Specimens of mineralized or nonmineralized tissues were pla ced arbitrarily in the defects before each radiographic exposure. The radiographs were captured through a video camera, digitized and stored in a personal computer. Every radiographic image was then subtracted from a baseline one without any change. The result of the subtraction was evaluated with CADIA. A linear correlation (r2=0.99) was found bet ween the bone chips (1-5 mg of dry weight) placed in the mesial defect and the CADIA values. Bone chips in the buccal defect (behind the imp lant), however, were not detected unless their weight reached 14 mg or more. For conventionally exposed radiographs, it was not possible to recognize soft tissue specimens (1-6 mg), either in the buccal or the mesial defect. However, when ''underexposed'' radiographs (exposure ti me: 0.13 s) were obtained, a linear correlation (r2 = 0.80) was calcul ated for soft tissue specimens in the mesial defect and CADIA values. In normally exposed radiographs, the CADIA system could detect even th e smallest change in bone density (bone chip of 1 mg of dry bone weigh t) and correlated almost linearly with these changes. Provided that th e radiographic images are obtained with standardized geometry and norm al exposure time, the tissue density changes detected by this system w ithin bone defects represent only mineralized tissue changes. By under exposing radiographs, CADIA may even reveal soft tissue changes around dental implants.