This study was conducted to evaluate both the effect of different cavity designs and different ceramic, composite CAD/CAM blocks and regular direct resin composite on the fracture resistance of endodontically treated teeth.
Materials and methods: A total of 80, non-carious, crack-free freshly extracted human maxillary premolars were used in this study. The teeth received a standardized endodontic treatment and then were divided in to two groups (40 each) according to the cavity design Design1 (MOD cavities) and Design2 (MOD with buccal and lingual cusp reduction), the two groups were further subdivided into sub groups (10 each) according to the type of restorative material used, either IPS e max CAD, Lava Ultimate, Vita Enamic, or Filtek Z 350 XT. Teeth were mounted in a universal testing machine, compressed with crosshead speed of 1mm/min, for testing their fracture resistance.
Results: One-way ANOVA was used to test each main effect separately. One-way ANOVA for the effect of cavity design showed statistical significant difference between both designs (P= 0.003). The post-hoc test revealed that Design 2 has the significantly higher mean fracture resistance (P= 0.001) than did Design 1. Meanwhile, One-way ANOVA for the effect of type of restorative material used showed statistical significance for types of restorative material used
(P= 0.001). The post-hoc test revealed that IPS e max CAD has significantly the highest mean fracture resistance (P= 0.001). Moreover, Lava Ultimate and Vita Enamic had significantly higher mean fracture resistance than that of Filtek Z 350 XT (P= 0.001).
Conclusions: Within the limitations of the study, it can be concluded that
Endodontically treated maxillary premolars prepared with an extensive loss of tooth structure and restored with chair-side indirect esthetic restorations had a resistance to fracture under simulated occlusal load significantly higher than that of direct resin composite restorations.
Chair-side CAD/CAM ceramic restorations are superior over hybrid ceramics.
Allowing a cusp coverage of approximately 2.5 mm in bulk would enhanced fracture resistance of dentin-bonded onlays over inlay preparations with no cusp coverage in vitro.