Fracture Load Of Fibre-Reinforced Composite Bridges After Chewing Simulation

Objectives : To investigate the effects of cyclic loading fatigue and fibres orientation within the pontic, on initial fracture (IF) and final fracture (FF) loads of directly-fabricated 3-unit inlay-retained fibre-reinforced composite fixed partial dentures (FRC-FPDs).

Methods : Twenty FRC-FPDs (n=20), replacing lower first molar by two inlay-retainers, were directly fabricated over duplicated acrylic teeth. Woven polyethylenene fibres (Construct/Kerr) were used to fabricate the main framework of all samples. Type-I specimens (n=10) had bidirectional E-glass fibre sheet (Everstick Net/Stick) perpendicularly-impeded within the pontics, while Type-II had small piece of woven unidirectional fibres (Construct/Kerr) instead. Group A (n=10) was the control, and Group B (n=10) specimens were cyclically-loaded in a chewing simulator (240,000cycles/5 kg). All samples were loaded in a universal testing machine with a compressive load (N) applied along the central fossa of each sample (1mm/min crosshead speed) until fracture. IF and FF values were recorded for each sample. Series of paired and independent t-test were used to detect any statistical difference within subgroups (α=0.05).

Results : Mean FF values were significantly higher in all subgroups compared to the IF (Table 1). Neither fibre orientation nor cyclic loading had a significant effect on IF values. However, fibre orientation had a significant effect on FF of all groups. Cyclic loading only had significance on FF of Type-II specimens.

Conclusions : Incorporating bidirectional fibres in pontics had a positive outcome by reducing the effect of cyclic loading and improving significantly the mechanical resistance of the FRC-FPDs.