The effect of hybrid CAD/CAM materials in different thicknesses and the light mode used on the microhardness and color stability of resin cements

The aim of this study is to evaluate the effect of two hybrid CAD/CAM materials of different thicknesses and the light mode used on the microhardness and color stability of resin cements. In this study, two different hybrid CAD/CAM materials were evaluated: resin infiltrated ceramic (Enamic, Vita Zahnfabrik, Bad Sackingen, Germany) (RIS) and composite resin nanoceramic (GC Cerasmart, GC, Tokyo, Japan) (KN). Sections of 1mm, 2mm, 3mm, 4mm and 7mm thick were taken from each block. 400 specimens were prepared using dual cure conventional resin cement (G-Cem LinkForce, GC, Tokyo, Japan) (KRS) and dual cure self adhesive resin cement (G-Cem One, GC, Tokyo, Japan) (SARS) (n: 400). The cements were placed in a stainless steel mold (6 mm diameter 1 mm height). With the transparent tape placed on the cement, the cement was isolated from the blocks and its adhesion was prevented. Ceramic specimens were placed on the cement and polymerized with an LED light device (Valo Cordless, Ultradent, South Jordan, USA). The light device was applied as Standard mode (40 sec) and High Power mode (32 sec). Color and microhardness measurements were made 24 hours after the resin cement samples were prepared (T1) and after 10,000 cycles of thermal aging (T2). Vickers microhardness measurements were made three times for each surface by applying 0.49 N force on both the lower and upper surfaces of the resin cement for 15 seconds, and the measurements were averaged. Color measurement of the samples was performed on a spectrophotometer device (Vita Easyshade Advance 4.0, Vita Zahnfabrik, Bad Sackingen, Germany), using color parameters and CIE Lab color system, 24 hours after polymerization (T1) and after thermal aging (T2). Data were analyzed by ANOVA and Bonferroni test was used for pairwise comparisons (p<0.05). In the findings of this thesis research, in the comparisons made between composite nanoceramic and resin infiltrated ceramic, T1; KRS (1mm, 2mm, 3mm-Standard mode), ix KRS (1mm, 2mm-High Power mode), SARS (1mm, 2mm, 4mm-Standard mode), SARS (1mm, 2mm, 4mm- High Power mode), T2; KRS (2mm-Standard mode), KRS (2mmHigh Power Mod), SARS (1mm, 2mm, 3mm, 4mm-Standard mode), SARS (2mm,4mmHigh Power mode) groups observed statistically significant difference in lower microhardness values in (p0.05). In comparisons made between composite nanoceramic and resin infiltrated ceramic, no statistically significant difference was observed in the upper microhardness values, except for the high power mode SARS-2mm group (p0.05). In the comparisons made between composite nanoceramic and resin infiltrated ceramics, in KRS (7 mm-Standard Mode), KRS (2mm, 7 mm-High Power Mode), SARS (1mm7mm-Standard mode), SARS (3mm-High power mode) groups Statistically significant difference was observed in E values (p<0.05). In comparisons made between different material thicknesses, a statistically significant difference was observed in the microhardness values of the resin cements (p<0.05). When the ceramic thickness increased from 1 mm to 7 mm, the microhardness of the resin cement decreased on both the upper and lower surfaces in both ceramic types. In comparisons made between standard mode and high power mode, there was no statistically significant difference in terms of microhardness values of resin cements (p 0.05). In comparisons made between different material thicknesses, a statistically significant difference was observed in the E values of self-adhesive resin cements polymerized on resin-infiltrated ceramics (p<0.05). In comparisons made between standard mode and high power mode, the E value of selfadhesive resin cement polymerized over 7 mm resin infiltrated ceramic showed a statistically significant difference. SARS (7mm-RIS) group polymerized with high power mode showed lower E value (p<0.05). However, there was no statistically significant difference in E value between standard mode and high power mode in other groups (p0.05). There was no statistically significant difference in microhardness values in comparisons between conventional resin cement and self-adhesive resin cement (p0.05). In comparisons between conventional resin cement and self-adhesive resin cement, KN (1mm, 2mm, 4mm-Standard mode), KN (1mm, 3mm, 4mm, 7mm-High Power mode), RIS (1mm, 2mm,4mm- Standard mode), RIS (1mm, 2mm, 4mm, 7mm-High Power Mode) groups showed a statistically significant difference in E values (p<0.05). As a result of this thesis research, the microhardness values measured from the lower and upper surfaces of the resin cements showed a tendency to decrease with the increase of x the thickness of the ceramic material. After the thermal cycle application, the microhardness values of the upper surface did not change. There was no difference between the use of composite nanoceramic and resin infiltrated ceramics in terms of upper microhardness values of the cements. In comparisons made between standard mode and high power mode, no difference was found in terms of microhardness values of resin cements. Keywords: Hybrid ceramic, self adhesive resin cement, conventional resin cement, microhardness, color change