A retrospective analysis of 44 implants with no rotational primary stability used for fixed prosthesis anchorage

The aim of this study was to determine the osseointegration potential of implants with apical primary stability but no resistance to rotation in variable clinical conditions.

Patient records of treatment performed between October 1993 and May 2004 were reviewed for primary implant stability. Patients who exhibited implants without rotational primary stability (RPS) were reviewed further to determine patient age, gender, implant type, implant surface, loading protocol, and prosthesis type.

Forty-four implants without RPS were reported in 12.8% of patients treated during the period reviewed. Statistical significant differences in cumulative survival rate (CSR) were seen with implant location and surface. No significant difference in CSR was observed in relation to loading protocol, despite a higher success rate (17.4% higher) for the immediate loading population. No difference in CSR was observed with respect to gender.

In the early years of machined implants, there was a higher failure rate of implants without RPS. The results for this implant population show that there are statistically significant differences in survival rate between the maxilla and mandible, and also between titanium oxide-surfaced implants and machined implants. The sample size of this study limited the statistical significance of the difference in CSR observed between loading protocols. Implants without RPS that are not removed at the time of surgery can become osseointegrated with a survival rate of 82%. Survival rates increase when testing sample is limited to titanium oxide-surfaced implants under an immediate loading protocol. Under the appropriate level of risk, implants that have apical primary stability but no resistance to rotation can become osseointegrated when incorporated in a rigid prosthesis under immediate loading circumstances.