A Retrospective Analysis of 125 Single Molar Crowns Supported by Two Implants: Long-Term Follow-up from 3 to 12 Years

Purpose: The purpose of this study was to analyze retrospectively the survival rate of implants used in pairs to support a single molar crown over a long-term follow-up period and to compare the efficacy of this technique to other existing methods of treatment. Materials and Methods: The charts and radiographs of 105 patients who each received two implants to support a screw-retained single molar were examined according to the following criteria: age, gender, location of implant, time of loading (delayed versus immediate), opposing dentition, and the existence of adjacent implants. Results: Patients with follow-up between 3 and 12 years were selected to illustrate the long-term outcomes of the two-implant replacement procedure. Two hundred fifty implants were placed in 125 molar sites in 105 patients. Five of the 250 implants failed, resulting in a cumulative survival rate of 98.0%. Seven of 125 restorations experienced porcelain fracture (5.6%), seven prosthetic screws loosened (5.6%), and one abutment screw loosened ( 1.0%). Discussion: The placement of two implants to support a screw-retained single molar successfully reduces rotational forces that create stress on the implant. A single regular-diameter or even a wide-diameter implant is susceptible to these forces, which may lead to fatigue over the long term. Conclusions: Two implants for the replacement of a single molar represent an effective method that provides a high survival rate over a long-term follow-up period. This approach produced a cumulative survival rate higher than that usually seen in studies of single implants used for molar replacement. The two implant-supported molar crown showed fewer complications than single implant-supported molar crowns. Keywords: dental implants, molar replacement, osseointegration, teeth in a day, two-implant molar