Size or hierarchical dependence of the elastic modulus of three ceramic-composite CAD/CAM materials

Abstract

Objective: To measure the elastic modulus of three ceramic-composite CAD/CAM materials at three different microstructural dimensions: macro, micro, and nano.

Methods: Three novel ceramic-composite CAD/CAM materials (Enamic, Lava Ultimate, and Cerasmart) were investigated. Rectangular cross-sections 10 × 5.7 × 1 mm³ (n = 30) were cut from standard sized milling blocks of each material prior to polishing. Specimens were macro-tested using three-point bending and with a dynamic mechanical analyzer (DMA), micro-tested using a nano-indentation system, and finally at the nano-level with an atomic force microscope (AFM). Data were analyzed with 1-way ANOVA (α = 0.05).

Results: At the macro level Enamic showed the highest elastic modulus, followed by Lava Ultimate and Cerasmart respectively (p < 0.001). Measurements at the micro and nano level resulted in bimodal distributions of the elastic modulus values associated with the various phases present with values higher and lower than measured at the macro level. Only at the nano-level were the various phases of Cerasmart able to be distinguished.

Conclusions: The tested materials showed different elastic modulus at the different size or hierarchical levels that enabled comparison with the hierarchical values of enamel.

Significance: Studying the mechanical properties of these novel materials at different size or hierarchical scales can help to understand their potential clinical performance, such as structural durability and opposing tooth wear and lead to more biomimetic like dental restorative materials.

Keywords: Atomic force microscopy; CAD/CAM; Ceramic resin composites; Elastic modulus; Hierarchical structure; Nano-indentation.