Evaluation of a Reverse-Tapered Design on the Osseointegration of Narrow-Diameter Implants in Beagle Dogs: A Pilot...

The purpose of this study was to evaluate a reverse-tapered design on the osseointegration of narrow-diameter implants in comparison with a conventional tapered design in beagle dogs.

All mandibular premolars and first molars were extracted bilaterally in four beagle dogs. Three months later, three kinds of implants were placed in both quadrants of the mandible: tapered narrow-diameter implants processed by cold working (TNC; n = 8), reverse-tapered narrow-diameter implants (RTN; n = 8), and reverse-tapered narrow-diameter implants processed by cold working (RTNC; n = 8). The animals were sacrificed at 4 weeks. Implant stability quotient (ISQ) values were measured at the time of implant placement and sacrifice. Histomorphometric analysis was performed.

The baseline ISQ values were significantly lower in the RTN (56.0 ± 11.6) and RTNC (57.2 ± 9.8) than in the TNC (68.0 ± 5.4; P = .021). At 4 weeks, the TNC (69.9 ± 5.1) exhibited significantly higher ISQ values compared with the RTNC (61.6 ± 4.1; P = .024). Histologic analysis in the RTN and RTNC revealed osseointegration without any signs of inflammation; however, unresolved coronal gap or dehiscence was also observed. The total bone-to-implant contact ratios (BIC) in TNC, RTN, and RTNC were 55.1% ± 11.5%, 47.8% ± 19.1%, and 60.2% ± 15.3%, respectively, and no significant differences were shown among them. The BIC for the coronal part in each group was 51.1% ± 29.4%, 28.8% ± 33.8%, and 23.9% ± 23.3%, respectively, and the differences were not significant. In the threaded part, TNC, RTN, and RTNC showed a BIC of 56.3% ± 9.6%, 50.7% ± 18.3%, and 65.3% ± 15.6%, respectively. There was no significant difference among them.

The reverse-tapered design on narrow-diameter implants showed a lower initial stability than the conventional tapered design; however, there was equivalent osseointegration in an early healing phase.