THE EFFECT OF GLAZING AND THERMOCYCLING ON THE SURFACE ROUGHNESS OF DIFFERENT CAD/CAM MILLED CERAMIC LAMINATE VENEERS WITH SEM OBSERVATIONS
Authors:   PhD in Medical Sciences, Restorative Dentistry., R. Ahmedbeyli Ferid , M. Ahmedbeyli Ramiz ,   PhD in Medical Scienses, DMSc/Doctor of Medical Science, Full Professor of the Therapeutic Dentistry Department., Ersoy Mustafa ,   PhD in Conservative Dentistry, Assistant Professor in Restorative Dentistry.
Published: February 2025

CAD/CAM technologies are one of the rapidly developing fields in digital restorative dentistry. The objective of this in vitro study was to evaluate the influence of glazing and thermocycling on the surface roughness values of four different types of milled CAD/CAM ceramic materials.

Aim - to evaluate the effects of glazing and thermocycling on the surface roughness values of four different types of CAD/CAM ceramic veneers. This study hypothesized that there would be a statistically significant difference in surface roughness values between glazed and nonglazed CAD/CAM materials across the four tested ceramics.

Materials and Methods - As part of the investigation,80 CAD/CAM ceramic veneer samples were milled using CAD/CAM system (inLab MC XL CEREC, Dentsply Sirona, Germany). The processing occurred after scanning of the first right typodont incisor of the upper jaw model prepared with the palatal chamfer preparation design without approximal involvement (KaVo, Germany) via an Omnicam scanner (CEREC, Dentsply Sirona, Germany). Four different CAD/CAM ceramic materials were evaluated in this study: lithium disilicate (IPS E.max CAD, Ivoclar, Germany), leucite-reinforced ceramic (IPS Empress CAD, Ivoclar, Germany), feldspathic ceramic (Cerec, CEREC, Dentsply Sirona, Germany), and hybrid ceramic (Cerasmart, GC, Japan). The 80 samples were categorized into four groups (20 in each, n=20), further divided into glazed and nonglazed subgroups (10 samples, n=10). All specimens underwent 10,000 thermal cycles.The surface roughness values were evaluated at three stages: post-milling, post-glazing, and post-thermocycling. Scanning electron microscope images (magnification 100x, 250x, 500x, 1000x) were captured for each material before glazingand after thermocycling.

Results -Significant differences in surface roughness values were observed among materials after glazing and thermocycling. Surface roughness notably decreased following glazing. The Cerec group exhibited significantly higher surface roughness values after glazing compared to Cerasmart, Empress, and E.max groups (p < 0.05). Analysis of the glazed surfaces after thermocycling also revealed significant differences among the groups (p < 0.05). Tamhanes T2 post-hoc test showed that the Cerec groups average surface roughness values were significantly higher than those of Cerasmart, Empress, and E.max after thermocycling (p < 0.05). For non-glazed samples, thermocycling similarly led to higher surface roughness values in the Cerec group compared to the other three groups (p < 0.05). These findings highlight the effects of glazing and thermocycling on the surface roughness of CAD/CAM ceramic materials, reflecting their clinical behavior.

Conclusion - Statistically significant differences were found between the glazed and non-glazed samples in terms of surface roughness. Among the tested materials, the Cerec group consistently showed higher roughness values compared to Cerasmart, Empress, and E.max (p < 0.05). Glazing and thermocycling significantly influenced the surface roughness of all groups.