Correlation between placement torque and survival of single-tooth implants

Abstract

Purpose: This study evaluated the survival parameters of single-tooth implants through clinical and radiographic analysis.

Materials and methods: Implants were restored within a 24-hour period with a provisional crown designed to receive an occlusal masticatory load. This approach was compared to implants restored after a healing period (the control group). Forty-six implants were placed in 23 patients who were each treated with 2 Frialit-2 implants placed in sites between the second premolar in the maxilla or mandible. The manufacturer's recommended formal surgical procedure was followed, and primary stability was standardized with a minimum insertion torque of 20 Ncm. The sites were randomly selected, and the clinical and radiographic parameters were standardized with individual templates.

Results: Data were collected at 24 h, and at 1, 3, 6, 12, 18, and 24 months. The experimental group included 10 failed implants; 9 of the failed implants had been placed with an insertion torque of 20 Ncm. One implant from the control group failed during the 24-month follow-up period. The survival rate was independent of implant length, site position, and bone quality and quantity. Relative risk for implant failure was associated with insertion torque (relative risk 0.79 [CI: 0.66-0.930]; Cox regression) (P < or = .007), in the experimental group but was not significant for those in the control group (ie, implants placed after a healing period; relative risk 0.78 [CI: 0.34-1.78]; Cox regression) (P < or = .057). To achieve osseointegration, it was found that an insertion torque above 32 Ncm was necessary (chi2= 15.68; P < or = .004).

Discussion: A careful evaluation is necessary for a better understanding of the survival rates of immediately loaded implants. In this study, insertion torque was associated with the potential for risk, which can be decreased by 20% per 9.8 Ncm added.

Conclusion: Given these results, and considering the number of patients treated, immediate provisional crowns should only be proposed with early loading if an appropriate initial insertion torque has been applied.