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. 2025 Jun;17(3):158-168.
doi: 10.4047/jap.2025.17.3.158. Epub 2025 Jun 25.

Effect of thermomechanical aging on fracture strength of anterior crowns fabricated with different CAD-CAM materials

Mine Helvacıoğlu Özkardeş  1 , Hatice Banu Özel  1 , Erkut Kahramanoğlu  1
Affiliations

Effect of thermomechanical aging on fracture strength of anterior crowns fabricated with different CAD-CAM materials

Mine Helvacıoğlu Özkardeş et al. J Adv Prosthodont. 2025 Jun.

Abstract

Purpose: The purpose of this study was to assess the effect of thermomechanical aging on fracture strength of CAD/CAM (computer aided design and computer aided manufacturing) anterior crowns.

Materials and methods: A resin maxillary central incisor was prepared and 96 epoxy resin replicas were obtained. Anterior crowns were produced and divided into four groups: IPS (IPS e.max CAD, 1.5 mmthickness), CD (Celtra Duo, 1.5 mm thickness), GC (GC Initial UHT, 1.5 mm thickness) and GC1 (GC Initial UHT, 1 mm thickness). Twelve crowns of each group were subjected to a chewing simulator for 240,000 cycles, and the other 12 crowns were regarded as control. Fracture resistance of aged and non-aged crowns were tested using a universal testing machine (Shimadzu AGS-X). One-way ANOVA, Tukey post hoc and independent sample t-tests were used to analyze the data and a P value < .05 was considered significant.

Results: IPS crowns without aging had the highest (2094.3 ± 399.31 N), and the GC1 crowns after aging had the lowest (1216.99 ± 302.96 N) fracture strength values. The difference of fracture strength among the same thickness samples without aging was not statistically significant (P > .05). The fracture strength of the GC1 group was significantly lower than those of the other groups (P < .05). After aging; GC group showed significantly higher fracture strength than the IPS and GC1 groups. The CD group's fracture strength was significantly higher than the GC1 group (P < .05). Aging significantly decreased the fracture strength of the IPS group (P < .05).

Conclusion: All monolithic crowns employed in this research proved to be resistant to physiological chewing forces in the anterior region.

Keywords: Anterior crown; CAD-CAM; Chewing simulator; Fracture strength; Zirconia reinforced lithium silicate.

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Figures

Fig. 1
Fig. 1. Computer aided design of the restoration.
Fig. 2
Fig. 2. Position of the sample fixed on the universal testing machine.
Fig. 3
Fig. 3. Change in fracture strength of samples after thermomechanical aging.
IPS: IPS e.max CAD 1.5 mm, CD: Celtra Duo 1.5 mm, GC: Initial Zr 1.5 mm, GC1: GC Initial Zr 1 mm. Significance levels for materials; IPS: < 0.001, CD: 0.057, GC: 0.521, GC1: 0.714
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