Abstract
Dental ceramic restorations are widely used in restorative dentistry. However, these restorations can be affected once cemented in the oral cavity by several factors. How can conventional surface treatments, such as glazing and mechanical polishing, diminish the effects of aging? The purpose of this in vitro study was to evaluate the effect of thermocycling and conventional surface treatments on the surface roughness and microhardness of three types of glass-ceramics by using a profilometer, scanning electron microscopy (SEM), atomic force microscopy (AFM), and a microhardness tester. Three types of ceramic systems (zirconia reinforced lithium silicate glass-ceramic, lithium disilicate glass-ceramic, and feldspathic glass-ceramic) (n = 48) were prepared. The samples were subjected to thermocycling for 10,000 cycles. Surface roughness was evaluated numerically using a profilometer and visually by using SEM and AFM. Microhardness was performed using a microhardness tester. The data were interpreted using the ANOVA test, and the results were correlated using Pearson’s correlation formula (r). Significant differences were found before and after thermocycling for the Ra (p < 0.01) and Rz (p < 0.05) parameters. As well, differences between glazed and polished surfaces were significant before and after thermocycling for surface roughness and microhardness (p < 0.05). A correlation was made between average surface roughness and microhardness (r = −460) and for the maximum surface roughness and microhardness (r = −606). Aging increases the roughness and decreases in time the microhardness. The tested ceramic systems behaved differently to the aging and surface treatments. Surface treatments had a significant impact on the microhardness and surface characteristics. The glazed groups were reported with higher surface roughness and lower microhardness when compared to the polished groups before and after thermocycling. The measuring roughness techniques determine the scale-dependent values for the Ra (Sa) and Rz (Sq) parameters. Thermocycling almost doubled the surface roughness for all the tested samples. Microhardness decreased only for the Celtra glazed samples. Nano-roughness increased the values for Vita and slightly for Emax. Thermocycling had little effect on Emax ceramic and a more significant impact on Celtra Press ceramic.
Highlights
The long-term clinical success of dental ceramics is influenced directly by several factors
This study investigated the effect of thermocycling and different surface treatments on the microstructure, surface roughness, and microhardness of three types of heat-pressed glass-ceramic
The correlation was statistically analyzed. Were observed because they depend on the method of fabrication, surface treatments applied, and measurement methods [45]
Summary
The long-term clinical success of dental ceramics is influenced directly by several factors Some of these factors include the crystal-based microstructure of the ceramic material, the fabrication process of the materials, technologies, and the clinical environment. All these steps can have a negative impact on the ceramic materials related to their brittle behavior [1]. The final ceramic restorations do not need more adjustments from the clinician, but sometimes additional occlusion modifications are necessary. These additional adjustments need polishing afterward, in order to prevent bacterial accumulation and later discoloration and excessive wear for the opposing teeth [4,5,6]. Ceramic glazes are made of a mixture between a powder and a liquid fired on the ceramic surfaces, resulting in a glossy surface [7]
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