Strength-limiting damage in lithium silicate glass-ceramics associated with CAD-CAM.

CAD-CAM processes are widely used in dental restoration fabrication. However, the impact of machining on material strength remains unclear. Prior research has shown that surface damage can reduce ceramic strength. It was already known that lithium silicate glass-ceramics are popular for dental restorations. No prior work had resolved how machining variables affect damage accumulation. This gap motivated the current study. The uncertainty around material-specific responses to machining led to the investigation. The need to compare commercial materials under controlled conditions arose from clinical relevance. Understanding how fabrication routes influence strength is essential for optimizing dental prosthesis performance.

The study aimed to assess how machining and material factors influence damage in lithium silicate glass-ceramics. The specific problem is strength reduction due to subtractive machining. The motivation stems from the need to improve dental restoration durability. The authors sought to evaluate clinically relevant variables. The objective was to compare CAD-CAM and laboratory processes. The goal was to quantify strength-limiting damage effects. The study focused on three commercial materials. The purpose was to identify how fabrication routes affect bi-axial flexure strength.

The researchers selected three lithium silicate glass-ceramics for testing. For each material, two groups of disk-shaped specimens were prepared. One group was fabricated using CAD-CAM processes. The other group used a controlled laboratory method. Specimens were tested for bi-axial flexure strength. Fractographic analyses were conducted to assess damage. Surface roughness was measured for each specimen. Statistical comparisons were made between fabrication routes.

Bi-axial flexure strength varied significantly by material and fabrication route. Polished specimens showed higher strength than CAD-CAM counterparts. IPS e.max CAD specimens had a 44% strength reduction. Celtra Duo showed a 46% decrease in mean BFS. Vita Suprinity had a 21% reduction but greater variance. Machining introduced median and radial cracks in CAD-CAM specimens. Heat treatments failed to eliminate these strength-limiting damages. Fractographic evidence confirmed machining-induced flaws.

The study found that CAD-CAM processes introduce strength-limiting damage in lithium silicate ceramics. The magnitude of this effect depends on both material and fabrication route. Polished specimens consistently showed higher BFS than CAD-CAM ones. The authors propose that machining-induced cracks are the primary cause of strength reduction. No prior work had resolved the variability in BFS among materials. The findings suggest that fabrication method significantly affects prosthesis performance. The authors suggest that current heat treatments are insufficient to mitigate machining damage. These results highlight the importance of fabrication route in dental restoration design.