Immediate implant placement in molar regions: risk factors for early failure.

OBJECTIVES To identify risk factors for early failure of immediately placed implants in molar regions associated with three bone regenerative techniques. METHODS Ninety-two patients (44 women and 48 men; mean age 50 years, 35 smokers and 57 non-smokers) in need of a single implant crown to replace a molar were included. After placing the implant, patients were randomized to one of three treatment groups for bone reconstruction of remaining periimplant defects: Autologous bone (AB) chips, Ossix membrane (OM) or a combination of AB chips and OM. The implant was submerged, and after 4 months of healing a re-entry surgery was made to connect a healing abutment. Implants with a dehiscence on ≥2 sites (mesial/distal/oral/buccal) together with ≥50% visible threads, were judged as failures. A series of simple logistic regression analyses were performed to identify risk factors for failure among the following independent variables: sex, jaw, smoking status, plaque, bleeding on probing, fistula, extraction reason, mean initial periimplant defect size, treatment group, implant length, buccal bone dehiscence (BBD), soft-tissue dehiscence and infection. The identified risk factors entered a multiple logistic regression analysis. RESULTS Fifteen implants failed before abutment operation (13 explantations/two non-osseointegrated). Treatment group had no impact on failure. Risk factors for failure were: Smoking >10 cigarettes/day (odds ratio [OR]=9.29, confidence interval [CI]=1.21-71.16), BBD (OR=11.43, CI=1.34-97.74) and infection (OR=36.7, CI=2.75-489.31). CONCLUSIONS Implants placed immediately after extraction of a molar were associated with a high risk for failure at abutment operation. There was no difference in failure rate between three bone reconstructive techniques.