Dental Implants have been proved to be successful prosthetic modality in edentulous patients for 10 years. However, there are few reports on the survival of implant according to location in molar regions. The purpose of this study was to evaluate the 4~5 years' cumulative survival rate and the cause of failure of dental implants in different locations for maxillary and mandibular molars.

Among the implants placed in molar regions in Gwangju Mir Dental Hospital from Jan. 2001 to Jun. 2002, 473 implants from 166 patients(age range; 26~75) were followed and evaluated retrospectively for the causes of failure. We included 417 implants in 126 periodontally compromised patients, 56 implants in 40 periodontal healthy patients, and 205 maxillary and 268 mandibular molar implants. Implant survival rates by various subject factors, surgical factors, fixture factors, and prosthetic factors at each location were compared using Chi-square test and Kaplan-Meier cumulative survival analysis was done for follow-up(FU) periods.

The overall failure rate at 5 years was 10.2%(subject level) and 5.5%(implant level). The overall survival rates of implants during the FU periods were 94.5% with 91.3% in maxillary first molar, 91.1% in maxillary second molar, 99.2% in mandibular first molar and 94.8% in mandibular second molar regions. The survival rates differed significantly between both jaws and among different implant locations(p<0.05), whereas the survival rates of functionally loaded implants were similar in different locations. The survival rates were not different according to gender, age, previous periodontal status, surgery stage, bone graft type, or the prosthetic type. The overall survival rate was low in dental implant of too wide diameter(≥5.75 mm) and the survival rate was significantly lower for wider implant diameter(p<0.01) in mandibular second molar region. Among 5 surface types(acid etched, SLA, TPS, RBM, and HA), the survival rate of SLA type implant was the highest during the FU periods and the failure rates of HA type implants was significantly high following functional loading. Among 26 failed implants, 20 resulted in early failure of osseointegration or infection prior to functional loading, and 6 were removed because of progressive bone loss or implant fracture.

In conclusion, implant survival rates were different in different locations on the posterior jaws, and the fixture diameter and surface type were the significant factor for implant survival in mandibular 2nd molar region. This observation suggests that implant treatment planning might require region-specific manner.