Biomechanical contribution of fibre-glass posts in endodontically treated teeth

Objectives: Literature has widely demonstrated that root canal treatments weaken the tooth, especially in MOD cavity premolars. Aim of this study was to compare, by means of a non-destructive experimental procedure (Cerutti et al, Effects of Adhesive Restoration on Cuspal Deflection in Endodontically Treated Premolars, IADR 2003, Abstr.2597), the behaviour of composite resin restorations with or without fibre-glass posts in endodontically treated premolars.

Methods: Fifteen maxillary sound premolars were included in self-curing resin and placed in a custom loading cell, then loaded with known values of axial force (range 0-294N) on their occlusal surface. Cuspal displacement was measured by two laser sensors aimed at the buccal and oral sides of each sample. Teeth were prepared with MOD cavities and endodontically treated, then split into 3 groups and restored with: gr.A: Dispersalloy ; gr.C: Excite DSC+Tetric flow+ Artemis (Ivoclar-Vivadent); gr.P: Excite DSC+Variolink II+FRC PostecPlus+Tetric flow+Artemis (Ivoclar-Vivadent). Load tests were repeated, allowing a direct comparison of the two conditions on the same samples. ANOVA statistical analysis was performed between gr.C and P; gr.A was considered as a control group.

Results: Considered parameters were: Average Stiffness (the mean necessary load in order to cause a 1 µm cuspal displacement, in N/µm); Structural Recovery, assuming as 100% the sound tooth stiffness. In group P, restored with fibre-glass post, resulted a decrease in cuspal deflection (P=0.02).

Conclusion: The use of a fibre-glass post in MOD cavity premolars evidences a significant increase in structural recovery compared to the full composite restorations. This may be an important suggestion for the clinician, since in endodontically treated maxillary premolars this could reduce the risk of fracture and allow a better restoration/tooth longevity, as recently described by Literature (Ferrari et al, Post placement and residual coronal structure affect root-treated premolars' survival, IADR 2007, Abstr.1385).