Effects of simulated gastric juice on color stability, surface roughness and microhardness of laboratory-processed composites

Medical problems such as gastroesophageal reflux disease can cause considerable damage to restorations in the oral environment. This study evaluated the effects of gastric juice on the surface characteristics of different types of laboratory-processed indirect composites with different filler particles and polymerization modes. Specimens were prepared from Tescera (TES; Bisco), Sinfony (SIN; 3M ESPE), Solidex (SOL; Shofu), and Adoro (AD; Ivoclar Vivadent). Before exposing the specimens to simulated gastric juice for 24 h, color, surface roughness, and microhardness were measured on one half of the polished flat surface of each specimen. After exposure to the simulated gastric juice, the same tests were repeated on the other half of specimen surface. Results indicated that gastric juice had a significant impact on color change (p<0.001). AD showed the largest surface roughness change among the resins (p<0.001). Gastric juice also significantly affected the microhardness of the materials, and AD and TES showed statistically similar change in microhardness (p>0.05).

The effect of a leucite-containing ceramic filler on the abrasive wear of dental composites

OBJECTIVES

The aim of this study was to evaluate abrasive wear of a dental composite based on a leucite-containing (KAlSi2O2 ceramic filler, and to compare it with the wear of a composite based on commonly used aluminum barium silicate glass filler.

METHODS

IPS Empress (Ivoclar-Vivadent) ingots were ball milled, passed through an 800 mesh (ASTM) sieve, and used as the leucite ceramic filler. Experimental composites were prepared by mixing the silane-treated fillers with the resin monomers. The resin consisted of 70 wt% Bis-GMA and 30 wt% TEGDMA containing camphorquinone and DMAEMA as the photoinitiator system. Glass-based composites were also prepared using silane-treated aluminum barium silicate glass fillers and the same resin system. TetricCeram, a commercially available dental composite, was used as control. Spherical specimens of the composites were then prepared and kept in water for 2 weeks to reach equilibrium with water. An abrasive wear test was performed using a device designed in our laboratory and weight loss of the specimens was measured as an abrasion parameter after each 50 h. SEMs were taken from worn and fractured surfaces. Degree-of-conversion of the composites was measured using FTIR spectroscopy. Vickers surface microhardness, flexural strength, and flexural modulus of the composites were also measured. The data were analyzed and compared using ANOVA and Tukey HSD tests (significance level=0.05).

RESULTS

The results showed that there were significant differences among the abrasive wear of the composites (p<0.05). The ranking from least to most was as: leucite-based composite<TetricCeram<glass-based composite. The higher wear resistance of leucite-based composite could be related to its higher surface hardness.

SIGNIFICANCE

Using leucite-containing glass as an alternative for aluminum barium silicate glass fillers in dental composites generated a significant increase in the wear resistance of the resin composites which should be beneficial in the development of dental materials.