Healing of surgically created circumferential gap around non-submerged-type implants in dogs: A histomorphometric study

Objectives: This study was conducted to evaluate the healing of surgically created circumferential gaps around non-submerged-type implants according to varying size and healing periods in dogs. Material and methods: In four mongrel dogs, all mandible premolars were extracted and after an 8-week healing period, non-submerged-type implants were placed. Circumferential coronal defects around the implants were performed surgically with a customized tapered step drill. Groups were divided according to the width of the coronal gaps: 1, 1.5, or 2 mm. First the right side of the mandible was prepared, and after 8 weeks, the left side was prepared. The dogs were sacrificed following an 8-week healing period. Specimens were analyzed histologically and histomorphometrically. Results: As the size of the coronal gap increased, the unfilled area tended to be greater. In terms of bone-to-implant contact and bone density, both the 1 and 1.5 mm groups showed a larger percentage of coronal defect than the apical side, while the 2 mm group showed contrary results in the 8-week groups. The general histologic features in the 16-week groups were similar to the findings of 8-week groups but were more matured, with a higher percentage of lamellar bone. A certain amount of bone filling and osseointegration was observed in the defects of all the groups. Conclusion: It can be concluded that the remaining defect, small enough to be clinically neglected, irrespective of gap size within 2 mm, does not need any kind of regenerating procedures.