The platform switching concept revisited. An experimental study in dogs.

OBJECTIVE: To evaluate the influence of the configuration of the marginal aspect of implants placed immediately into extraction sockets on peri-implant hard tissue adaptation. MATERIAL AND METHODS: In 6 Labrador dogs, endodontic treatments of the mesial roots of 1 M1 were performed and the distal roots were removed. 2 P2 was extracted as well. Implants were immediately placed in the center of the distal alveoli. Cylindrical straight implants were installed in the right side of the mandible (Control), while, in the left side, implants with a reduced diameter in the coronal portion, yielding an indentation in the surface continuity (Test), were installed. Cover screws were affixed, and the flaps were sutured to allow non-submerged healing. After 4 months of healing, histological slides were obtained for assessments. RESULTS: A buccal resorption of 1.58 \ub1 1.28 and 1.90 \ub1 1.93 mm at the control and of 0.26 \ub1 0.90 and 0.14 \ub1 0.66 mm at the test sites was observed at the premolar and molar regions, respectively. The buccal coronal level of osseointegration was located apically to the margin of the smooth/rough surface border by 2.40 \ub1 0.90 and 3.70 \ub1 0.87 mm at the control sites and 1.19 \ub1 0.45 and 2.16 \ub1 0.96 mm at the test sites at the premolar and molar sites, respectively. All differences yielded statistical significance. CONCLUSIONS: The use of implants with a reduced diameter in their coronal aspect may contribute to preservation of the buccal bony crest in a more coronal level compared with conventional implants. Thus, the study confirmed the efficacy of the "platform switching" concept