Influence of different photoinitiators on the resistance of union in bovine dentin: Experimental and microscopic study

Abstract

Background To evaluate in vitro the influence of photoinitiators on the microtensile strength of adhesive systems and composite resins in bovine dentin. Material and Methods Forty dentin obtained from bovine teeth were randomly distributed in four groups (n = 10) according to the different adhesive systems and composite resins used: G1 - AAPS + VAPS (Ambar APS + Vittra APS); G2- AAPS + O (Ambar APS + Opallis); G3 - A + VAPS (Ambar + Vittra APS) and G4 - A + O (Ambar + Opallis). After restoration with the composite, the samples were sectioned to obtain toothpicks that were subjected to the microtensile and nanofiltration test (1.0 mm/min). Results The Kruskal-Wallis test did not show significant differences between the groups ( p <0.05). The values in MPa were: AAPS + VAPS - 19.56 MPa; AAPS + O - 19.77 MPa; A + VAPS - 17.78 MPa; A + O - 22.44 MPa. The result of the Mann-Whitney test showed no significant differences depending on the adhesive (Ambar Universal- 19.11 MPa, Ambar APS Universal- 21.70 MPa) and the composite resin used (Vittra APS- 18.75 MPa, Opallis - 23.75 MPa). The AAPS + VAPS and AAPS + O groups showed intense silver nitrate infiltration. The A + APS group showed a moderate infiltration and the A + O group had a mild infiltration in the adhesive system/dentin interface. Conclusions The use of different photoinitiators in the composition of adhesive systems and restorative composites did not affect their bond strength values and the presence of water in the solvent of the APS photoinitiator system had a negative influence, increasing the degree of infiltration in the hybrid layer when compared to the camphorquinone photoinitiator. Key words: Dentin, adhesive systems, composite resin, photoinitiators, tensile strength, nano-infiltration.

Effect of Chemical Challenges on the Properties of Composite Resins

“…In acid environments, resin composites can suffer loss of important properties as decrease of microhardness and increase of surface roughness, becoming a weakness for the quality of restorations [ 17 , 21 ]. In this context, with the intention of improving the resistance of resin materials, new materials are being developed and disposable in the market [ 14 – 16 ]. The resin materials used in this study are widely used for restoration treatments nowadays, with nanoproperties technology, BisGMA-free, and new photoinitiators agents; furthermore, few studies have been conducted verifying materials' resistance performance [ 16 , 22 ].…”

“…In this context, with the intention of improving the resistance of resin materials, new materials are being developed and disposable in the market [ 14 – 16 ]. The resin materials used in this study are widely used for restoration treatments nowadays, with nanoproperties technology, BisGMA-free, and new photoinitiators agents; furthermore, few studies have been conducted verifying materials' resistance performance [ 16 , 22 ]. Like this, in this study, the resins analyzed showed changes in microhardness and roughness properties after degradation in water, alcohol, citric acid, and phosphoric acid solutions for 180 days of chemical challenge, and the hypothesis could be accepted as soon as composition of each resin determined the degradation.…”

“…Nevertheless, important results were found about VITTRA about chemical degradation resistance. The fact that VITTRA has an advantageous polymerization system with combination of different photoinitiators [ 16 ] could be interfered in high performance of polymeric matrix formation that contributed for good results after degradation. Another point that could be considered is about VITTRA composition, with high percentage of chemical elements than other tested resins, as carbon, silica, and aluminum that could be reinforced by the VITTRA performance [ 22 ].…”

“…In addition, with intension to make the nanoparticle composite resins closer to natural teeth tissue characteristics, health biocompatible new formulations of materials have been developed with free comonomers of BisGMA and nanofilling glass that provide similar characteristics of natural enamel, improving the restoration esthetic aspect and durability [ 14 , 15 ]. Another way to reach better performance of composite resin restorative materials is to work modifying the polymerization systems of materials as the resins with an advanced polymerization system (APS) [ 16 ]. This recent technology was developed to increase important characteristics of composite resins: to guarantee the high percentage of degree of conversion, increase bond strength, and provide high quality of esthetic profile [ 14 – 16 ].…”

“…Another way to reach better performance of composite resin restorative materials is to work modifying the polymerization systems of materials as the resins with an advanced polymerization system (APS) [ 16 ]. This recent technology was developed to increase important characteristics of composite resins: to guarantee the high percentage of degree of conversion, increase bond strength, and provide high quality of esthetic profile [ 14 – 16 ].…”