Durability of Bond Strength to Dentin Using Two Universal Adhesives in Two Different Modes and Different Degradation Conditions: An In Vitro Study

Abstract

This study aimed to evaluate the microshear bond strength of resin composite to dentin when using two universal adhesives in both etch-and-rinse and self-etch modes after being subjected to twenty four hours water storage, one year water storage and thermocycling equivalent to one year with subsequent failure mode assessment using stereomicroscope and scanning electron microscopic evaluation of the adhesive interface. A total of 144 specimens were used in this study; 120 specimens (prepared from 30 teeth) for microshear bond strength testing and failure mode assessment, and 24 specimens for scanning electron microscopic evaluation (prepared from 24 teeth). Specimens were prepared from 54 recently extracted caries free third molars and randomly divided into 12 groups, according to the adhesive treatment (All Bond or Single Bond Universal), etching mode (etch-and-rinse or self-etch) and aging method (thermocycling or water storage). Regarding the water storage groups, specimens were stored in distilled water at 37 ˚C for 1 year. In thermocycling groups, specimens were stored in distilled water at 37 ˚C for 24 hours then subjected to 10,000 thermal cycles (TCs) between 5 and 55 ˚C with a dwell time of 15 s in each bath and a transfer time of 5 s. Microshear bond strength to dentin was then measured using a Universal Testing Machine at a cross head speed of 1.0 mm/min until failure. After debonding of each specimen, the fractured interface was assessed using a stereomicroscope at magnification of 40X to determine the mode of failure.