Impact of adhesive surface and volume of luting resin on fracture resistance of root filled teeth

P>Aim To investigate the correlation between geometric parameters of severely compromised root filled (RCT) pre-molar teeth with irregular root canals and their fracture resistance. The null hypothesis tested was that the fracture resistance of root filled teeth is not influenced by: (i) the adhesive surface of the post-space preparation (A(PS)), (ii) the coronal tooth surface (A(A)), (iii) the amount of resin cement (V-C) and (iv) the Young's modulus of the specimens. Methodology A total of 48 noncarious human pre-molar teeth with irregular root canals were decoronated, root filled and adhesively restored with post-retained direct composite crowns. After thermomechanical loading (1 200 000x, 5-50 degrees C), static load was applied until failure. The geometric parameters of the tooth were evaluated by microcomputed tomography (mu CT) using impressions taken after post-space preparation. Linear regression analyses were performed to correlate the geometric parameters of the specimens with their fracture resistance. Results The amount of resin cement (V-C) comprised up to 88% of the entire post-space (mean 67%) and had no impact on the maximal load (P = 0.88). The latter was significantly influenced by post-space preparation (P = 0.003). Conclusions Amongst the geometric parameters tested, the surface area in the root canal had the greatest impact on fracture resistance of root filled pre-molars restored with posts and composite crowns, whilst the fit of the post was less important.