ABSTRACT
Nowadays, esthetic dentistry has become an important part of modern dentistry. Bleaching is considered as a conservative, safe and effective way for treatment of discolored teeth. Although bleaching is commonly used on anterior teeth, the bleaching gel may come into contact with patient's former amalgam restorations and result in corrosive effects, dissolution of amalgam phases and increasing release of mercury. Mercury released from dental amalgam during mouthguard bleaching can be absorbed and increase the total mercury body burden. The aim of this study was to determine the amount of mercury released from Iranian and foreign brands of amalgams with spherical and admixed particles, polished and unpolished, after 16% carbamide peroxide gel application. This experimental in vitro study was performed on 256 Iranian and foreign amalgam samples with spherical and admixed particles. The provided samples were put in distilled water and classified according to the type of amalgam, shape of particles and quality of surface polishing. The test samples were placed in Nite White 16% carbamide peroxide gel and control samples were put in phosphate buffer [Ph=6.5] for 14 and 28 hours. The amount of released mercury was calculated using AVA-440 Mercury Analysis System [Thermo Jarrell Ash model SH/229] with cold-vapor atomic absorption. Data were analyzed using t-test, four way and three way ANOVA tests with P<0.05 as the level of significance. 16% Nite White carbamide peroxide gel caused a significant increase in amount of mercury released from amalgams in all groups [P<0.05]. Mercury release from Iranian amalgam was higher than that from the foreign brands [P<0.05]. There was no significant difference in mercury released from spherical and admixed amalgams [P>0.05]. The amount of mercury released from Iranian and foreign amalgams was time dependent [P<0.05]. Furthermore, the amount of mercury released from unpolished amalgams was higher than polished ones [P<0.05]. the present study indicated that exposure of amalgam to 16% Nite White carbamide peroxide gel causes a significant increase in mercury release from the amalgam which is significantly influenced by the brand, exposure time and surface, polishing
Subject(s)
Peroxides/adverse effects , Dental Amalgam , MercuryABSTRACT
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