Microhardness Investigation of Dental Composite Resins Exposed to Corrosive Environment

Abstract

The aim of this study was to evaluate the microhardness Rockwell and Young s modulus of a new nano-hybrid and nano-fill composite resins exposed to corrosive media. The study was performed on two composite resins, one nano-hybrid and one nano-fill, enamel, dentine, translucent, respectively body shade, of which were made 20 samples (25.0 � 0.1 mm lengths, 10.0 � 0.1 mm widths and 3.0 � 0.1 mm thicknesses), which were immersed in mouthwash for 1 minute per day for 10 days, the rest of the time being stored in artificial saliva. Measurements of Rockwell microhardness and Young�s modulus on samples were made between on the first day, after 6 days and 10 days of immersion in mouthwash comparative with 0 day. The results showed that after immersion in the corrosive environment, both materials had the hardness values changed, but medium values of Rockwell microhardness to nano-fill composite resin were higher than nano-hybride. At the nano-hybride composite resin, it was observed that the enamel and clear translucent groups had the mean values increased after the first day of exposure to mouthwash, compared to the dentine group, which showed a higher mean value after 6 days. At the nano-fill composite resin, for the enamel and body groups were obtained the higher values of HRC after 10 days. For the dentine group, after 6 days, Filtek Ultimate showed the same variation as Harmonize dentine shade. Harmonize composite resin showed higher values of Rockwell microhardness and Young�s modulus for all study groups compared to Filtek Ultimate.

In Vitro Evaluation of Gastric Acid and Toothbrushing Effect on the Surface State of Different Types of Composite Resins

“…In our study nanohybrid composite resins (Filtek Z550 and Herculite XRV Ultra) recorded lower surface roughness when comparing to the tested microhybrid composites Filtek Z250 and Herculite XRV after one year of toothbrushing and one year of hydrochloric acid action. Composite resins with small filler particles have a higher wear resistance [34,35]. For microhybrid composites, large fillers are lost due to wear, creating larger surface defects when comparing to nanohybrid ones [25,26,29].…”

“…Although the gastric acid pH varies between 1.4 and 1.6, in our study we have chosen the diluted acid considering that in the oral environment the acidity is slightly buffered by saliva [29,31,[38][39][40]. In addition, the literature mentions that saliva neutralizes acids on dental surfaces in about 3 min [33,34]. For maintaining the H + ions values as constant as possible, the acid solution was changed every hour.…”

Comparative Study Regarding the Compressive Strength of Different Composite Resins Used for Direct Restorations

“…Stress applied to the surface of the material in a dry environment is transmitted inside the structure through the silane layer and causes deformation both inside and outside the nanoclusters. The presence of water in the resin matrix could diminish the internal concentration of the wiping and would allow the cracks to spread [25][26][27][28]. Moreover, when wet materials are tested, hydrolysis and polymerization of the silane phase inside the nanoclusters causes changes in stress transmission both inside and outside the nanoclusters.…”

Effect of Dietary Challenges on the Flexural Properties of Resin-based Composites

“…Aura Easy contains ultra-high density glass fillers whose unique morphology can improve the mechanical properties of the composite. Adaptive Response Technology (ART), adopted by Harmonize, involves the fusion of zirconia and silica nanoparticles forming a stabilised filler network for enhanced mechanical strength [18]. Sonic Fill 2 is an upgraded version of Sonic Fill 1, which presents better mechanical properties due to the employment of new filler system composed of zirconium oxide and silica oxides nanoparticles, while preserving the sonic-activation technology [19].…”