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International Arab Journal of Dentistry

Abstract

Objectives: This in-vitro study aimed to evaluate the impact of different CAD/CAM materials (IPS e.max® CAD and Cerasmart®) and thicknesses (0.7 mm, 1 mm, and 1.5 mm) on the fracture resistance of indirect overlay restorations.

Methods: Sixty-three human third molars were divided into 7 groups (n=9) based on material and thickness, including a control group of 9 sound teeth. Only 54 specimens were prepared using a thin-section cutting machine, scanned, and their scans were used to fabricate overlays from different materials and thicknesses. After adhesive cementation, the overlays underwent thermal cyclic loading (5,000 cycles between 5°C and 55°C). A universal testing machine assessed fracture resistance, revealing that 1 mm (2737 N) and 1.5 mm (2879 N) thicknesses exhibited significantly higher resistance than 0.7 mm (1974 N) (p0.05).

Results: A statistically significant correlation was identified between the thickness of CAD/CAM ceramic materials and the fracture resistance of monolithic ceramic overlays. Thicknesses of 1 mm (2737 N) and 1.5 mm (2879 N) exhibited significantly higher fracture resistances than the 0.7 mm thickness (1974 N) (p < 0.05). Additionally, the choice of ceramic material significantly impacted fracture resistance, with Cerasmart® (2867 N) outperforming IPS e.max® CAD (2191 N) (p = 0.003). No significant interaction was found between ceramic thickness and material type (p = 0.101). A subsequent one-way ANOVA indicated that the fracture resistance of the experimental groups was comparable to that of the sound teeth (2401 N) (p > 0.05).

Conclusions: This study found a significant correlation between CAD/CAM ceramic thickness and fracture resistance, with 1 mm and 1.5 mm thicknesses showing superior performance compared to 0.7 mm. The material choice also influenced resistance, with Cerasmart® being more effective than IPS e.max® CAD. Notably, all thicknesses demonstrated fracture resistances comparable to sound teeth, indicating that even thinner overlays can maintain adequate strength.

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