[ effect of collagen removal on the microleakage of four single-component adhesive system in class V composite restorations]

The role of collagen fibers in dentin adhesion and hybrid layer has not clearly been established. This study evaluated the effect of collagen removal on the microleakage of four single bottle adhesive systems at resin-dentin interfaces by dye penetration technique. This experimental study was performed on 144 class V cavities prepared in buccal and lingual surfaces of human premolar teeth at the cemento-enamel junction with the cervical margin in dentin or cementum and the occlusal margin in enamel. The cavities were etched with 36% phosphoric acid for 15 seconds, rinsed and divided into 8 groups. In 4 groups the cavities were filled with a composite resin using four different dentin adhesive systems [Single Bond, Excite, One-Step, Prime and Bond NT]. In the other 4 groups the acid etched cavities were treated with a 5.25% NaOC1 solution to remove the collagen and restored using the same adhesive system and composite resin. The specimens were thermocycled and stored in distilled water at 24 °C for three months and were immersed in a 10% solution of methylene blue dye for 72 hours. After rinsing, the restorations were sectioned buccolingually and assessed under an optical stereomicroscope. Microleakage was scored by two independent observers. The data were analyzed by Kruskal Wallis and Dunn multiple comparison tests. Collagen removal resulted in a significant decrease of microleakage for One-Step and an increase or Excite at cervical margin [P<0.001] but did not reduce the microleakage at cervical margins for Prime and bond NT and Single Bond group. Except collagen removal, microleakage of class V composite restoration depends on the type of bonding system which can be related to fillers, functional monomers or solvent of adhesive systems

in vitro study of wet-bonding fissure sealant micro-leakage [Embrace]

It has been shown that bonding agents reduce the sealant micro-leakage especially after salivary contamination. This study attempts to evaluate the effect of a bonding agent [ingle-Bond] and salivary contamination on a sealant micro-leakage [Embrace]. In this study a wet-bonding sealant [Embrace] was used in 64 sound human premolars after being etched with 35% phosphoric acid. The sealant micro-leakage was investigated under four different conditions: 1] Saliva + Bonding, 2] with bonding alone, 3] with saliva and 4] sealant alone. After thermocycling process, the teeth were covered with wax and nail polish except for 1-1.5 mm around the sealant. The samples were rinsed after immersed in 0.5% basic - fushin solution for 24 hours. Two buccolingual sections were prepared from central and proximal areas of the crowns. The micro-leakage was assessed according to the degree of dye penetration around the sealants. Dye penetration occurred in 5 cases of group 3 which was more than other groups. In the first group, 8 cases had a score more than 1, one less than the other groups. The Kruskal-Wallis test did not show any significant statistical differences between the groups. The use of a bonding agent, prior to application of a Wet-bonding fissure sealant, does not have a significant effect on the micro-leakage of Embrace Sealant in isolated or saliva contaminated conditions