Fracture resistance and stress distribution of simulated immature teeth after apexification with mineral trioxide aggregate

AimTo evaluate the effect of adhesive restorations on fracture resistance and stress distribution in teeth with simulated immature apices and apical plugs of mineral trioxide aggregate (MTA). MethodologySixty bovine incisors were sectioned 8mm above and 12mm below the cemento-enamel junction (CEJ). The root canal was enlarged using a diamond bur, resulting in remaining root canal walls with 0.1-0.2mm of thickness. A 5-mm apical plug of MTA was placed and the teeth were restored according to the following groups: GP - the root canal was filled with gutta-percha and endodontic sealer; CR - the root canal was filled with light-cured composite resin inserted incrementally; FP - a fibre post was cemented into the root canal; and RFP - the fibre post was relined with composite resin prior to the cementation into the root canal. A load was applied on the crown of all teeth at 135 degrees to their long axis until fracture. Data was analysed by one-way anova and SNK tests (=0.05), whilst the fracture pattern was evaluated according to the position of the fracture. Stress distributions in the restored teeth were verified by finite element analysis. ResultsTeeth restored with fibre posts and relined fibre posts were associated with the highest fracture resistance, whilst the GP group had the lowest values. GP and RC groups had similar fracture resistance values (P=0.109). All fractures types involved the cervical and middle thirds of roots. The GP model had high levels of stress concentration in the cervical and middle thirds of roots. No difference was found amongst the stress concentration in the RC, FP and RFP models. ConclusionRestorative protocols alter the fracture resistance and stress distribution of immature teeth after placement of MTA apical plugs.