Straight Versus Angulated Abutments on Tilted Implants in Immediate Fixed Rehabilitation of the Edentulous Mandible: A 3-Year Retrospective Comparative Study

Purpose: The aim of this study was to evaluate and compare the use of straight versus angulated abutments on tilted implants in the All-on-Four immediate function protocol. Materials and Methods: A total of 85 patients (36 men and 49 women; mean age 56.5 years) with edentulous mandibles were treated according to the All-on-Four concept using computer-guided implant placement. All patients received immediate interim prostheses screwed onto distal tilted implants by means of angulated (control group, n = 42) or straight abutments (test group, n = 43) and were followed for at least 3 years. Outcome considerations comprised implant and prosthetic survival and success rates, marginal bone level changes, patient satisfaction, and required clinical time. Student t test at a significance level of P .05 was used to correlate the influence of the prosthetic protocol on marginal bone levels around the implants. Results: Overall implant survival rate was 98.21% for the control group and 98.83% for the test group. None of the 85 fixed prostheses were lost during the observation period (prosthetic survival rate of 100%). Statistically significant differences (P = .0068) in marginal bone loss were found between control and test groups. All patients were functionally and esthetically satisfied with their restorations. Required clinical time averaged 50 minutes for the control group and 30 minutes for the test group. Conclusion: The described simplified and shortened surgical-prosthodontic protocol that avoids use of angulated abutments may be considered a reliable alternative to the traditional All-on-Four protocol.