Clinical and histologic evaluation of submerged and nonsubmerged hydroxyapatite-coated implants: A preliminary study in dogs

A clinical and histologic study was performed to evaluate the differences i n the healing of submerged and nonsubmerged hydroxyapatite-coated 2-piece i mplants. Three foxhounds were used for this evaluation. Mandibular premolar s 1, 2, 3, and 4 were extracted. Three months later, 2 submerged implants w ere placed on one side of the mandible, and 2 nonsubmerged implants were pl aced on the other side of the mandible. After 3 months of healing, the subm erged implants were exposed, and a third implant was placed on each side of the mandible in a nonsubmerged procedure. Clinical parameters were recorde d, the animals were sacrificed 6 months after placement of the first implan ts, and histologic and histometric analyses were performed. Results of the evaluation of the clinical parameters showed only minor differences among t he different treatment groups. Regarding the percentage of bone-to-implant contact of the different treatm ent groups, the submerged implants showed a bone-to-implant contact of 63.4 %, the nonsubmerged implants showed 70.3% contact, and the late nonsubmerge d implants demonstrated a bone-to-implant contact of 58.7%. The average dis tance from the implant neck to the first bone-to-implant contact (fBIC) for submerged implants was 0.58 mm, for nonsubmerged implants it was 1.09 mm, and it was 1.13 mm for late nonsubmerged implants. The vertical distance be tween the gingival margin and the apical extent of the junctional epitheliu m (aJE) varied from 1.14 mm to 1.28 mm in the different groups. The distanc e from the aJE to fBIC was 1.00 mm for the submerged group, 1.08 mm for the nonsubmerged group, and 1.00 mm for the late nonsubmerged group. Generally , it can be concluded that the clinical and the histologic behavior of subm erged or nonsubmerged 2-piece implants utilized in this experiment do not d iffer.