Logistic Regression Analysis of the Factors Involved in the Failure of Osseointegration and Survival of Dental Implants with an Internal Connection and Machined Collar: A 6-Year Retrospective Cohort Study.

BACKGROUND: Although the long-term success rate of dental implants is currently close to 95%, it is necessary to provide more evidence on the factors related to the failure of osseointegration and survival. PURPOSE: To establish the risk factors associated with the failure of osseointegration and survival of dental implants with an internal connection and machined collar and to establish a predictive statistical model. MATERIALS AND METHODS: An analytical, retrospective, and observational clinical study of a sample of 297 implants with a follow-up of up to 76 months. Independent variables related to the implant, patient, and surgical and rehabilitative procedures were identified. The dependent variables were failure of osseointegration and failure of implant survival after prosthetic loading. A survival analysis was carried out by applying the Kaplan-Meier model (significance for p < 0.05). The log-rank test and the Cox regression analysis were applied to the factors that presented differences. Finally, the regression logit function was used to determine whether it is possible to predict the risk of implant failure according to the analyzed variables with the data obtained in this study. RESULTS: The percentages of osseointegration and survival were 97.6 and 97.2%, respectively. For osseointegration, there were significant differences according to gender (p = 0.048), and the risk of nonosseointegration was 85% lower in women. Regarding survival, the Cox analysis converged on only two factors, which were smoking and treatment with anticoagulant drugs. The risk of loss was multiplied by 18.3 for patients smoking more than 10 cigarettes per day and by 28.2 for patients treated with anticoagulants. CONCLUSIONS: The indicated risk factors should be considered, but the analysis of the results is not sufficient to create a predictive model.

Does the transversal screw design increase the risk of mechanical complications in dental implants? A finite elements analysis.

The transversal screw was introduced in order to overcome some disadvantages of the transocclusal screw. However, its mechanical risk has not been studied sufficiently. The main purpose of this research was to assess and compare stress distribution in the screws and abutment of a single-crown implant with transversal and transocclusal screw models. Two 3D models were assembled to analyse a single-implant-supported prosthesis with transversal and transocclusal screws embedded in the jawbone. The crown was subjected to a static load of value 300 N with different levels of inclination. The transversal screw model, with an axial load of 15°, was the one with lowest stress values in all its components. However, the stress was greater with more inclined loads when compared with the transocclusal model. The prosthetic transversal screw showed much less stress than the rest of the components for any load inclination. The transversal screw design is the option with the lowest risk of mechanical complications, both in the prosthetic screw and in the abutment screw, when applying forces of lower inclination. The more oblique forces favoured a better biomechanical environment in the abutment and its screw in the transocclusal screw model.