Effects of implant morphology on rotational stability during immediate implant placement in the esthetic zone.

PURPOSE Primary implant stability is critical to achieving implant success, especially in a situation with immediate implant placement and provisionalization (IIPP) when bone quality and quantity are compromised. The purpose of this study was to examine the effects of implant morphology (tapered vs cylindric) and the final drill-implant diameter discrepancy (FD-IDD) of six implant systems on the incidence of rotational instability during IIPP in the esthetic zone. MATERIALS AND METHODS One hundred seventy-one implants in 112 patients were evaluated. Implants that exhibited inadequate resistance to the torque generated by the surgeon's hand during implant placement were classified as rotationally unstable. RESULTS The overall incidence of rotational instability for the tapered implants (1.1%) was significantly lower than that exhibited by the cylindric (nontapered) implants (20.5%). Among the cylindric implants, those with < 0.5 mm FD-IDD experienced a significantly higher incidence of rotational instability (36.6%) than groups with ≥ 0.5 mm FD-IDD. The incidence of rotational instability of cylindric implants with ≥ 0.5 mm FD-IDD was significantly greater than that of the tapered implants with a comparable FD-IDD. CONCLUSION Within the confines of this study, the use of a tapered implant with an FD-IDD of ≥ 0.5 mm minimized the incidence of rotational implant instability for the IIPP procedure.