Effect of thermal cycling on the flexural properties of resin composite and PEEK CAD-CAM blocks for molar crowns.

PURPOSE: This study evaluates and compares the flexural properties of computer-aided design-computer-aided manufacturing (CAD-CAM) resin composite and polyetheretherketone (PEEK) blocks used for molar crowns under three storage conditions. Furthermore, the relationship between the inorganic filler content (>70 wt. %) and the flexural properties of the resin composite blocks was clarified.

METHODS

Five commercially available resin composite blocks and one PEEK block were subjected to three storage conditions: dry storage, water immersion for 7 d at 37 °C, and 10,000 thermal cycles between 5 and 55 °C. The flexural strength and flexural modulus were analyzed using two-way ANOVA, followed by Tukey's post-hoc comparisons. The inorganic filler content and water sorption were analyzed via one-way ANOVA and the Tukey-Kramer post-hoc test, with the level of significance set at 5%.

RESULTS

The resin composite blocks exhibited a significantly higher flexural strength and flexural modulus than the PEEK block. A positive correlation was observed between the inorganic filler content and the flexural properties of the CAD-CAM blocks, specifically for the flexural strength (r = 0.49) and flexural modulus (r = 0.63). However, the PEEK block exhibited the lowest water sorption and minimal flexural properties changes across all conditions, as compared to the resin composite blocks.

CONCLUSIONS

Both the inorganic filler content and matrix resin composition influenced the flexural properties of the CAD-CAM crown materials. PEEK demonstrated superior durability under thermal and humid conditions, indicating its potential as a long-term restorative material for posterior crowns.