The influence of different storage media on Vickers hardness and surface roughness of CAD/CAM resin composites

Abstract

Introduction This study examined Vickers hardness as well as surface characteristics of different computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites prior to and after storage in various media. Materials and methods CAD/CAM resin composite blocks (Grandio Blocs (GB), Lava Ultimate (LU), Brilliant Crios (BC), Cerasmart (GC), Shofu Block HC (SB), Tetric CAD (TC), Luxacam Composite (LC); incl. different translucency variants) were prepared, polished and surface free energy was determined. The specimens were divided into four groups: dry conditions for 24 h (25 °C), demineralized water (37 °C), Pepsi Cola (37 °C) and 75% ethanol (37 °C). After seven and 28 days of storage, Vickers hardness was determined. Surface roughness was measured after the entire storage period. Results and discussion Vickers hardness was in the range of about 150 HV for GB, around 115 HV for LU, and 80–100 HV for BC, GC, SB, TC and LC. Only minor differences (total: 50.2 (6.4)–56.2 (3.2) mN/m) in surface free energy could be detected. No relationship was observed between surface free energy and filler content. However, a correlation between filler content and Vickers hardness was evident. Artificial aging caused a decrease of Vickers hardness (up to −40 HV or 35%) depending on storage media, duration and material. The changes in surface texture after immersion in different media were below a value of ΔSa = 0.015 µm. Conclusion Artificial aging of CAD/CAM resin composites leads to a significant decrease of Vickers hardness for most materials, while only small changes in surface roughness were identified. Graphical Abstract

Degradation effects of dietary solvents on microhardness and inorganic elements of computer-aided design/computer-aided manufacturing dental composites

“…Apart from FZ (direct composite), the indirect and CAD/CAM composites showed no statistically significant differences between acids and distilled water. The aforementioned finding on CAD/CAM composites is in accordance with a recent study that demonstrated similar effect on hardness value of CAD/CAM resin composites after aging 7-days in acidic drink and demineralized water [ 24 ]. FZ was the only material in our study that had Bis-GMA with TEGDMA as a diluting monomer that may cause it to be vulnerable to softening effect of acids.…”

“…Although VE had the highest filler content than all materials investigated, significant reduction in microhardness following postconditioning in 50% ethanol-water solution was observed. Interestingly, this was in contrast to recent research that reported little changes in hardness of CAD/CAM dental composites with high filler fractions following 7-day storage in 75% ethanol-water solution [ 24 ]. The filler composition (glass-ceramic sintered network) in VE that differed from the other composites investigated may have attributed to the findings of the current study.…”

“…Filler composition and filler treatment were responsible for the diversity in leaching of inorganic ions and the total amount of leachable ions corresponded to the DC of polymer network of dental composites [ 39 , 40 ]. Although recent research reported that when conditioned in solvents, minimal degradation was observed in CAD/CAM restorative materials with high filler fractions [ 23 , 24 ], the findings of this study showed that the filler composition and high filler fraction of CAD/CAM dental composites may synergistically influence their resistance to degradation effects of dietary solvents on microhardness.…”

“…Most research reported that the degradation of dental composites were mainly due to softening of resin matrix, changes in polymer network structure, and hydrolysis of silane couplers at the filler-matrix-interface [ 19 – 21 ]. Only a few studies investigated the degradation effects of dietary solvents on fillers of dental composites [ 22 – 24 ]. CAD/CAM restorative materials with high filler fractions had been reported to be minimally degraded in solvents [ 23 , 24 ] and only one study reported the baseline elemental analysis on CAD/CAM dental composites [ 23 ].…”

“…Only a few studies investigated the degradation effects of dietary solvents on fillers of dental composites [ 22 – 24 ]. CAD/CAM restorative materials with high filler fractions had been reported to be minimally degraded in solvents [ 23 , 24 ] and only one study reported the baseline elemental analysis on CAD/CAM dental composites [ 23 ].…”