[Evaluation of the effect of 16% carbamide peroxide gel [Nite White] on mercury release from Iranian and foreign spherical and admixed amalgams by cold vapor atomic absorption method]

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

[Comparison of the microleakage and shear bond strength of four current one component dentin bonding systems]

The success of tooth-colored restorations depends on bonding them to hard tooth tissue that will retain the restoration to the cavity preparation and prevent microleakage. Different adhesive systems have been introduced that provide bonding between tooth-colored filling materials and tooth structure [dentin] that will withstand the contraction forces generated by polymerization shrinkage while maintaining a marginal seal during functioning of the restored tooth. The purpose of this investigation was to study the microleakage of class V resin restorations and the shear bond strength of composite resin to dentin using four different types of current bond adhesive systems. This experimental study has been done on 96 intact human premolar teeth extracted for orthodontic purposes within a 3-month period. The teeth were randomly divided into two parts as A and B. In part A, Standardized classic class V cavity dimensions of 3.0 mm [occlusal-gingival], 2,0 mm [mesial-distal], and 2.0 mm [depth] prepared in buccal and lingual surfaces of teeth at the cemento-enamel junction with the cervical margin in dentin or cementum and the occlusal margin in enamel. Enamel Cavosurface margin of cavities were beveled. The cavities were etched with 36% phosphoric acid for 15 second then were rinsed. The cavities were restored with a composite resin [Z100 3M ESPE] using four different dentin adhesive systems [Single Bond [3M-ESPE], Excite [vivadent], One-Step [Bisco], Prime and Bond NT [Dentsply-Detry]], The specimens' thermocycled for 3000 cycles [5-55°C] and were then immersed in a 10% solution of methylene blue dye for 72 hours. After rinsing, the restorations were sectioned buccolingualy and the microleakages were scored by an optical stereomicroscope with x40 magnification. In part B, the teeth mounted in a 2.5 cm diameter acrylic cylinder mold and buccal surfaces of teeth were ground to expose dentin. After etching and rinsing, the four adhesive systems mentioned before were applied to dentin surface with the wet bonding technique. A cylinder of Z100 dental composite with a 3 mm diameter and 2 mm height was placed on the adhesive covered dentin surface of all groups and light-cured. The specimens were kept in distilled water at room temperature for one week and then thermocycled for 3000 times [5-55oc].Shear bond strength of specimens was measured using an instron universal mechanical testing machine with the cross-head speed of 0.5 mm/minute. Data were analyzed with one way ANOVA, Kruskal-Wallis, Tukey HSD and Mann-Whitney U tests. The mean and standard deviation of shear bond strengths [Mpa] of groups were as follows: One-Step:19.60 +/- 1.83, Single Bond: 21.44 +/- 3, Prime and Bond NT: 26.51 +/- 5.02, Excite: 29.78 +/- 3.85. Analysis of the results revealed that One-step had lowest and Excite had highest shear bond strength [P<0.05]. Prime and Bond system had the least and One-Step system had the most microleakage in dentin margins of restorations [P<0.05]. Single Bond and Excite bonding systems statistically had no difference in dentin marginal microleakage [P>0.05]. Different types of one bottle dentin bonding agents had different micro leakage scores and different shear bond strengths

[Comparison of serum interleukin-8 levels in patients with recurrent aphthous stomatitis and healthy individuals]

Recurrent aphthous stomatitis [RAS] is one of the most common inflammatory diseases affecting the oral mucosa; therefore an increase in pro-inflammatory cytokines like IL-8 may be expected. The aim of this study was to compare serum IL-8 levels in patients with RAS and healthy individuals. Eighty patients without a history of systemic disease were selected from those referred to the Department of Oral Medicine, School of Dentistry, Hamadan University of Medical Sciences, during May 2005 to Feb 2006. The study and control groups consisted of 40 patients [19 males and 21 females; mean age, 25.08 years] with RAS and 40 healthy cases [23 males and 17 females; mean age, 25.5 years], respectively. Whole blood [10/ml] was obtained from all participants and the serum was separated and stored at -70°C, until used. Serum IL-8 levels were measured by ELISA. Statistical analysis was performed using t-test [p<0.01]. The mean serum IL-8 level was 52.24 pg/ml in the RAS group and 5.01 pg/ml in the control group which showed a 10-fold increase in RAS patients [P<0.01]. These levels were greater than the upper limit of normal serum concentration in 35 [87.5%] of the RAS subjects [16 males, 19 females] and was within normal range in 5 [12.5%] cases [3 males, 2 females]. Thirty-seven [92.5%] of the healthy individuals demonstrated normal levels while 3 [7.5%] showed increased amounts. In this study, a significant increase in the mean serum IL-8 level was observed in the RAS group

[ vitro comparison of two tray bleaching agent: Kimia 16% and Opalescence PF 15%]

Esthetic dentistry and tooth esthetics are important parts of dental treatments today. Among these, Tooth bleaching treatment is a simple, safe and effective way to accommodate many patients' needs. Regarding to production of dental materials in Iran, this in-vitro study was conducted to compare the whitening effect and the speed of efficiency of bleaching agents [kimia 16% and Opalescence F 15%] using a tray. This experimental study was performed on forty extracted caries free maxillary central incisors which did not have any fluorosis and tetracycline discoloration. Roots of the teeth were covered with 2 layers of nail polish and they were divided into two groups then embedded in red wax. After preparing the bleaching tray for two groups, photographs of teeth were taken and the values of the teeth were determined visually using a vita shade guide. Afterwards the teeth were treated by carbamide peroxide gels [Kimia 16% and opalescence PF 15%] for an hour a day for two weeks. The lightness of the teeth were evaluated every day before treatment and also one month after the treatment period and the data was recorded. The data were analyzed by Signed T test, ANOVA and Mann-Withney U tests. The findings of this study showed that whitening effects of the two agents were statistically significant [P<0.01]. At the end of the study according to the recorded value, the lightness change in groups treated with Kimia was 6 degrees and in the other group [Opalescence PF], it was 6.3 degrees. There was no statistically significant difference between the two bleaching gels [P>0/05]. Using the tray bleaching method, both gels [16% Kimia and 15% Opalescence PF] had equivalent effects on whitening of the teeth

effect of collagen removal on shear bond strength of four single bottle adhesive systems

Achieving adhesion between restorative materials and dentin as a wet and dynamic surface is an important topic in restorative and especially in conservative dentistry. Adhesion of new dentin bonding systems depends on the formation of hybrid layer and micromechanical retention. Nevertheless, an ideal adhesive system has not yet been introduced .Recent studies reveal an increase in bonding stability when the collagen is removed from demineralized dentin surfaces. This study investigates the effect of collagen removal on the shear bond strength of four single bottle dentin bonding systems regarding their structural differences. This experimental study was performed on 56 intact human premolar teeth. Smooth surfaces of dentin were prepared on buccal and lingual aspects of teeth, providing 112 dentin surfaces. The dentin surfaces were etched with 37% phosphoric acid for 15 seconds and then rinsed. The specimens were divided into 8 groups. Single bottle adhesive systems [Single Bond [3M], One-Step [Bisco], Prime and Bond NT [Dentsply], and Excite [Vivadent]] were then applied on the dentin surfaces of 4 groups using the wet bonding technique. In the other 4 groups, the demineralized dentin surfaces were treated with a 5.25% solution of sodium hypochlorite for one minute in order to remove the surface organic components. The adhesive systems mentioned before were applied to these 4 groups with the same wet bonding technique. A cylinder of Z100 [3M] dental composite with a 3 mm diameter and 2 mm height was placed on the adhesive covered dentin surface of all groups and light-cured [400 mW/cm2 ,40 sec on each side]. The specimens were kept in distilled water at room temperature for one week and then thermocycled for 3000 times [5-55 °c]. Shear bond strength of specimens was measured using an Instron [1495] universal mechanical testing machine with cross-head speed of 0.5 mm/minute and chisel form shearing blade. Data were analyzed by Two Way ANOVA and Tukey HSD tests with p<0.05 as the limit of significance