"Biologic width"and crestal bone remodeling with sintered porous-surfaced dental implants: a study in dogs

The aim of this study was to obtain histometric measurements of bone and peri-implant mucosal tissue contact with implants of 2 sintered porous-surfaced designs. The "short-collar" design had a collar height (smooth coronal region) of 0.75 mm, while the "long-collar" model had a smooth coronal region of 1.8 mm.

Implants (2 per side) were placed in healed mandibular extraction sites of 4 beagle dogs using a submerged technique. After 4 weeks of healing, they were uncovered and used to support fixed partial dentures for a 9-month period. After sacrifice, specimens were retrieved and nondemineralized sections were examined histometrically to determine the most coronal bone-to-implant contact (first BIC) using the microgap as a reference and standard mucosal parameters of "biologic width."

Significant (P = .001) differences in first BIC were found between designs (1.97 mm for long-collar versus 1.16 mm for short-collar implants) for posteriorly located implants but not for anteriorly located ones (1.21 mm versus 1.38 mm; P = .40). If crestal bone loss involved sintered surface, fibrous connective tissue ingrowth was observed to replace lost bone. No significant differences in peri-implant mucosal measurements (total peri-implant mucosal thickness; length of the epithelial component of this mucosa, and thickness of the connective tissue component) were detected between implant designs.

Results suggest that "biologic width" accommodation drives initial crestal bone loss with sintered porous-surfaced implants. Histometric data obtained for bone contact showed no significant differences between the long- and short-collar implant designs.