Are Lower Insertional Torque Values Associated with Increased Early Dental Implant Failures?

Abstract

Statement of the problemThe purpose of this retrospective cohort study was to determine whether low insertional torque vales < 30-Ncm were associated with increased early dental implant failures. Materials and methodsA retrospective cohort study was conducted to evaluate dental implants placed in 2015 at the VA North Texas Health Care System in Dallas. The following inclusion criteria were defined: 1) patients who were not lost to follow-up within the first 6 months of implant placement; 2) cases with sufficient medical records, including pre-surgical and post-surgical evaluation. Patients were excluded as study subjects if: 1) they had inadequate medical records; 2) they were a current tobacco smoker or were undergoing treatment for systemic conditions such as bisphosphonate use, head and neck radiation, and chemotherapy. The primary predictor variable was dental implant insertional torque, measured at the time of implant placement as: < 30-Ncm, 30-39-Ncm, 40-49-Ncm, 50-59-Ncm, 60-69-Ncm, and > 60-Ncm. The primary outcome variable was early implant failure, defined chronologically as implant failure necessitating explantation within 6 months of placement.1 Secondary predictor variables were age ≥ 65 years and sex, defined as male or female. Descriptive, bivariate, and multiple logistic regression analyses were performed with P < .05 used to determine statistical significance. Results and outcomesThirty-three subjects and 69 implants met the defined inclusion and exclusion criteria. The average age of the cohort was 65 years. Sixty-two implants were placed in males, and 7 were placed in females. There was a total of 5 early failures (7%). Four occurred in males, and 1 occurred in a female. Four occurred in subjects ≥ 65, and 1 occurred in a subject < 65. Two early failures occurred with an insertional torque < 30-Ncm, 1 occurred with an insertional torque of 30-39-Ncm, and 2 occurred with an insertional torque of 50-59-Ncm. Analysis of the predictor variable and primary outcome variable revealed that decreased insertional torque values resulted in an increase in early dental implant failures and was statistically significant (P = .034). Specifically, insertional torque values below the threshold of 30-Ncm resulted in a 14-fold increase in early failures (OR 14.66; 95% CL 1.74-123.51). Analysis of the secondary predictor variables, age and sex, revealed no statistically significant differences with P = 1.00 and P = .4242, respectively. Discussion and conclusionThe results of this retrospective cohort study suggest that decreased insertional torque values of dental implants below 30-Ncm increase early failure rates within 6 months of dental implant placement. A systematic review by Oliveira et al found that there was not strong enough evidence to conclude that insertional torque < 30-Ncm established enough primary stability between the implant and surrounding bone. They concluded that this decreased primary stability decreased overall implant survival.2 The results of this present study suggest that a low insertional torque value < 30-Ncm decreases the primary stability of the implant in the surrounding bone, thereby increasing the rate of early dental implant failure. Future prospective studies by this group will be performed to further elucidate the association between insertional torque and early dental implant failure.