RISK-FACTORS AND MULTIPLE FAILURES IN POSTERIOR RESIN-BONDED BRIDGES IN A 5-YEAR MULTIPRACTICE CLINICAL-TRIAL

Objectives: A randomized controlled clinical trial was undertaken, to study the influence of some patient- and operator-dependent variables on the survival of posterior resin-bonded bridges (PRBBs) and to asses s the survival of 'replacement' PRBBs. This report contains some of th e results of the 5-year analysis. Methods: Survival was defined at thr ee levels: (1)complete survival (without any debonding), (2) functiona l survival (i.e. survival after one loss of retention) and (3) replace ment survival (survival of 'replacement' PRBBs, inserted after rebonde d bridges suffered a second dislodgement). Potential risk factors were analysed with Cox's proportional hazards model and differences were t ested for significance with the Breslow test. Observed effects are exp ressed as conditional-relative-risk (CRR). Survival of 'replacement' P RBBs was assessed with the Kaplan-Meier method. Results. Factors showi ng significant influences on complete survival were: 'location' (highe st risk for mandibular PRBBs: CRR = 2.2), 'aetiology' (higher risk in treatment of aplasia: CRR = 2.9), and 'time of existence' (open spaces existing less than 2 years before insertion of PRBB: CRR: 2.0). The f actor 'large open spaces in the mandible' was a risk for both complete and functional survival (CCR values 3.1 and 3.5, respectively). The s urvival of mandibular and maxillary 'replacement' PRBBs after 5 years was 19 +/- 7% and 31 +/- 18%, respectively. Conclusions: Risk factors for PRBBs were: 'location', 'aetiology', 'time of existence', 'isolati on method' and 'large open spaces in the mandible'. Mandibular 'replac ement' PRBBs showed such an unacceptably low survival rate that fabric ation is not recommended. (C) 1998 Elsevier Science Ltd. All rights re served.