Influence of abutment connections and plaque control on the initial healing of prematurely exposed implants: an experimental study in dogs

BACKGROUND: Spontaneous early implant exposure is believed to be harmful, resulting in early crestal bone loss around submerged implants. The purpose of this study was to examine the influence of abutment connections and plaque control on the initial healing of prematurely exposed implants in the canine mandible. METHODS: Bilateral, edentulated, flat alveolar ridges were created in the mandible of 10 mongrel dogs. After 3 months of healing, two implants were placed on each side of the mandible following a commonly used two-stage surgical protocol. Implants on each side were randomly assigned to one of two procedures: 1) connection of a cover screw to the implant and removal of the gingiva to expose the cover screw; and 2) connection of a healing abutment to the implant so that the coronal portion of the abutment remained exposed to the oral cavity. In five dogs (plaque control group), meticulous plaque control was performed. In the other five dogs (no plaque control group), plaque was allowed to accumulate. At 8 weeks post-implantation, microcomputed tomography was performed at the implantation site to measure bone height in the peri-implant bone. RESULTS: The plaque control group had greater vertical alveolar ridge height (9.7 +/- 0.5 mm) than the group without plaque control (7.4 +/- 0.7 mm; P <0.05). In the plaque control group, the average bone height was greater with the abutment-connected implant (10.1 +/- 0.5 mm) than with the partially exposed implant (9.3 +/- 0.5 mm; P <0.05). In the group without plaque control, the average bone height was greater with the partially exposed implant (8.2 +/- 0.6 mm) than with the abutment-connected implant (6.5 +/- 0.7 mm; P <0.05). CONCLUSION: These results suggest that the placement of healing abutments and meticulous plaque control may limit bone loss around submerged implants when implants are partially exposed.