Objectives: To assess the impact of intra-coronal preparation depth and restorative material on the fracture resistance of molar restored by endo-crown restoration.
Materials and Methods: Forty root canal treated maxillary first molars were prepared for endo-crown restorations. Specimens were divided according to the pulpal extension depth and material type into four groups (n=10): teeth prepared with 3 mm pulpal extension and restored by PEEK (TP); teeth prepared with 3 mm pulpal extension and restored by zirconia (TZ); teeth prepared with 5 mm pulpal extension and restored by PEEK (FP); and teeth prepared with 5 mm pulpal extension and restored by zirconia (FZ). After fabrication of the restorations, each endo-crown was cemented to its corresponding tooth. All specimens were thermo-cycled (5,000 cycles - 5°C and 55°C). Each specimen was loaded till failure using universal testing machine, then the mode of failure was recorded. Two-way ANOVA and Tukey's post-hoc tests were employed for data analysis (P< .05).
Results: The highest fracture load was recorded with FP group (2578.3± 337 N) and the lowest value was recorded with TZ group (1511.42± 168 N). Two-way ANOVA test showed a significant difference among studied groups. Post hoc test showed significant differences between each pair of groups, except a non-significant difference (P = .787) between TZ and FZ groups.
Conclusions: The fracture strength of molars restored with endo-crowns can enhanced by increasing the extension depth into pulp chamber. Moreover, PEEK is considered a promising material for endo-crowns.