[Evaluation of tooth color distribution in 20 to 30-year-old patients of Shahid Beheshti University related centers in 2010]

Tooth color assessing is very important in esthetic dentistry. The aim of this article was to study tooth color prevalence of 20-30-year-old patients and also presentation of a simple method for color assessment. One thousand fifty nonsmoker volunteers [501 men]. In a light, distance and angle constant condition the left maxillary incisors were photographed with a digital camera [Canon G9] using a retractor. The pictures were studied with Adobe Photoshop CS5 software. The color of the middle 1/9 of the tooth was measured in L[*]a[*]b[*] system. In the exact above condition vita pan classical shade guide was photographed in direction of neutral background. These pictures were studied with Adobe Photoshop CS5 and L[*]a[*]b[*] average was measured for the middle 1/9 of each sample. After measurement of delta E[*] for each person and vita pan classical shade guide, minimum delta E[*] was chosen for each tooth as the color of that tooth. Finally, the effect of colored liquid drinks was assessed. The most popular findings were A3.5 [16.85%] A3 [14.85%] and B1, B2 [9.8%]. The results of this study showed that the L[*] average in nonsmokers who drank colored liquids more than twice a day in comparison to noncolored liquid users was lower. The a[*] and b[*] average in this group was higher than noncolored liquid users. The most common findings were A3.5 [16.85%] A3 [14.85%] B1, B2 [9.8%]. Tooth color assessment with a digital camera and computerized study is simple and cheap but very sensitive

Marginal adaptation of the three indirect crowns

Good marginal adaptation is a prerequisite for a successful crown restoration while the incidence of microleakage, caries, damage to the base teeth and periodontal diseases is facilitated when this criteria is not achieved. Therefore, the present study determined the marginal gap in the porcelain crowns compared to indirect composite restorations of GC Gradia and Signum. In this invitro experimental study, 30 impressions were taken in the similar conditions and randomly assigned to receive porcelain crowns [Noritake super porcelain Ex-3] or indirect composite crowns of GC Gradia and Signum when no fluid and porosity were noted on them. The crowns were fitted on the master metal die and assessed by the stereomicroscope after complete sitting and finishing line preparation. The assessments were carried out on 8 points 1mm from the finishing line [buccal, lingual, mesial, distal, mesiobuccal, distobucaal, mesiolingual and distolingual]. Then, 8 jigs were fabricated and total 240 readings were made. The values were converted to micron and the statistical comparisons were made using nonparametric Kruskal-wallis and Mann-whitney U tests. Marginal gap of porcelain crowns was29/08 +/- 9/38microm and 84/53 +/- 15/47microm on the lingual and disto lingual points andtheGC gradia indirect composite, was 43.63 +/- 13.40microm and 74.53 +/- 28.03microm on the distal and distolingual points as well as 39.08 +/- 17.68microm and 95.44 +/- 30.66microm on the distal and mesiolingual aspects of the Signum indirect composites respectively .No significant differences were noted between the three crowns brands on the mesial, distal, mesiobuccal, distobuccal, and mesiolingual aspects.only 3 points [buccal, lingual and disto lingual] had significant differences. Regarding clinically acceptable values of marginal gaps mentioned in the literature,porcelain jacket crowns and indirect composite crowns possesses the necessary criteria of marginal gap and can be successfully used for crown restorations

Effect of [etch and rinse] and [self etch] bonding agents on the bond strengtl of composite resin to Iranian MTA

MTA is used frequently in dentistry. Root MTA is produced in Iran recently.This in vitro study assessed the shear bond strength of Root MTA using etch and rinse and self etch bonding systems. In this in vitro study, 20 acrylic blocks with a central hole [6X 2mm] were prepared and filled with the Root MTA. Bonding systems of Single Bond [etch and rinse] and Clearfil SE Bond Bond [self etch] were applied on the Root MTA. Z100 composite tubes [2X2mm] were bonded to prepared surfaces. The shear bond strength was estimated by Universal testing machine in MPa. The data were subjected to t-test for statistical analysis. Mean shear bond strength of Root MTA to composite were 4.71 +/- 1.77 and 4.79 +/- 1.88 MPa using Single Bond and Clearfil SE Bond systems respectively. The difference between tow materials was not statistically significant. As suggested by the result of this research, the shear bond strength of Z100 composite to Root MTA were comparable using etch and rinse and self etch bonding systems

Micro-shear bond strength of a nanofiller bonding with and without thermocyding in a newly invented device

Estimation of the survival of dental materials is especially important when manufacturing new materials. Thermocycling can greatly help in this respect. The purpose of this study was to evaluate micro-shear bond strength of a nanofiller bonding with and without thermocycling in a newly invented device. In this experimental study, human third molars were sectioned into 1.5 mm slices after extraction and disinfection. Clearfil Tri-S nanofiller bond was applied to the dentin part of sections according to the manufacturer's instructions. Clearfil AP-X composite resin was placed over the dentin using tubes with 0.75 mm internal diameter and one mm height and light cured. Specimens were randomly divided into three groups and subjected to thermocycling in a newly invented device for zero, 3000 and 5000 cyclesbetween 5 +/- 2°C and 55 +/- 2°C. Micro-shear bond strength was measured by microtensile tester with a cross-head speed of 0.5 mm/min. Obtained data were analyzed using one-way ANOVA. Tukey's test was used for multiple comparisons with a 95% confidence interval. The mean micro-shear bond strength after zero, 3000 and 5000 thermal cycles was found to be 19.27 +/- 4,56, 17.00 +/- 6.52 and 11.58 +/- 4.64 MPa, respectively. The reduction in bond strength between zero and 3000 thermal cycles was not statistically significant [P=0.3] but this reduction between zero and 5000, as well as 3000 and 5000 cycles was statistically significant [P0.002 and P0.03, respectively]. Increase in number of thermal cycles for more than 3000 reduces the micro-shear bond strength of Tri-S bonding agent

[ comparative study of acid and laser etching on micro shear bond strength of enamel]

With the increase of laser application in different fields of dentistry, further research is required to evaluate its efficiency in dental therapy. This study evaluated the effect of Er, Cr:YSGG laser conditioning of enamel on micro shear bond strength of composite resin of human enamel following two different tooth preparation methods [Diamond disk versus Er, Cr:YSGG laser]. In this invitro study, 125 human third molars were randomly assigned into 5 groups. Buccal and lingual enamel slices were prepared as below: A] laser-ablated without etching, B] laser-ablated and laser-etched, C] laser-ablated and acid-etched, D] cut by diamond disk and laser-etched and E] cut by diamond disk and acid-etched. Tubs of Z100 composite resin [3M, Dental Product/ USA] were bonded to conditioned enamel surfaces after applying two layers of Single Bond [3M ESPE, Dental product/ USA] Shear bond strength was measured by Micro-Tensile tester [Bisco Inc/USA] at a cross-head speed of 0.5 mm/min. Data were analyzed by one-way ANOVA, and Tukey tests. Mean shear bond strengths in groups were: A=23.14 +/- 6.53 MPa, B=23.77 +/- 5.56MPa, C=23.51 +/- 4.89MPa, D=19.30 +/- 5.56MPa and E=28.99 +/- 6.40 MPa respectively. The differences between [E, A], [E, B], [D, B], [C, D] and [D, E] were significant [P<0.05]. Micro shear bond strength of groups prepared by diamond disk and acid-etched were higher than groups prepared and etched by Er, Cr:YSGG laser. Therefore, re-etching with acid phosphoric is necessary if laser is used for tooth preparation or etching. Etching with acid phosphoric is recommended when laser is to used for tooth preparation or etching

Comparison of cytotoxic and inflammatory effect of four bonding agents on L929 mouse tlbroblasts

It is of interest in restorative dentistry to maintain the pulp vitality after pulp exposure in traumatized teeth or during cavity preparation. If the tooth is asymptomatic, the exposure site is taken place in a saliva-free environment, direct pulp capping is recommended. Pulp capping agents must be biocompatible. The aim of this study was to compare the cytotoxic and inflammatory effects of four bonding agents on L929 fibroblast. In this experimental study, after culturing and passaging these cells, samples of i Bond, Excite, One Step Plus and SE Bond, were prepared in capillary tubes and inserted in cultures. Cytotoxic effects were determined after 1, 24 hours and 7 days by MTT assay and for detecting the IL-6, fibroblast culture media were collected after 24 hours and assessed by ELISA. Statistical analyses were made using Kruskal-wallis and Mann -whitney U tests. There was a significant difference of cytotoxicity among the groups after 1 and 24 hours [P=0.001, P=0.029 respectively]. However, no significant difference was found. After 7 days, the amount of IL-6 production showed no significant difference among the groups. It was determined that i Bond had the least cytotoxic effects among the other groups. However, all the groups could induce the IL-6 secretion from fibroblasts

[Evaluation of microleakage in combined amalgam-composite resin restorations]

Combining the durability of amalgam and the esthetic appearance of composites can improve the quality and longevity of dental restorations. The aim of this study was to evaluate the effect of amalgam etching on microleakage at the cervical margins and the junction between amalgam and composite. In this experimental study 20 extracted sound maxillary premolars were used. Two class II cavities were prepared on the mesial [group A] and distal [group B] surfaces of each tooth. Group A cavities were restored with amalgam on the floor of the cavity and after etching the enamel walls, a self-cure bonding agent was applied followed by composite insertion. The same protocol was followed for group B cavities except that the etchant was placed on both amalgam and enamel walls. The teeth in each group were either stored for 1 week or 6 months in normal saline, then thermocycled for 1000 cycles [2 +/- 4°C and 54 +/- 4°C] and finally immersed in 2% fushin for 1 week. Marginal leakage was assessed by the degree of dye penetration on sections of the restored teeth, under a stereomicroscope [x 10]. Data were analyzed using Mann Whitney U-test [p<0.05]. None of the specimens showed microleakage in the amalgam-composite interface. No statistically significant difference was observed in microleakage between the two groups after 1 week and after 6 months. The study groups did not show a significant difference regarding storage time. Amalgam ethching had no significant effect on the microleakage of combined amalgam-composite restorations

effect of different surface treatments on the bond strength of composite resin core to carbon fiber posts

Carbon fiber posts are widely used in dentistry. The most problem is their low bond strength with composite resin utilized as core. The aim of this study was to evaluate the effect of different surface treatments on the tensile bond strength of composite resin core to carbon fiber posts. Thirty six posts free of defects, were selected and randomly divided into 4 groups and treated as follows: Group 1: No treatment [control]. Group2: Surface treatment with Single Bond Group3: Surface treatment with Sandblast + Single Bond Group4: Surface treatment with Sandblast + Silane + Single Bond. A cylindrical composite resin core [5x5x5 mm] was built around each post using Z100. Post-core assemblies were tested for tensile failure by Instron testing machine at a cross-head speed of 10 mm/min. The bond strength was assessed by Newton [N]. The tensile bond strength were respectively, Group 1: 262.33 +/- 23.37N, Group 2: 522.77 +/- 37.33N, Group 3: 613.50 +/- 39.93N, Group 4: 641.00 +/- 43.35N. ANOVA and Scheffe test showed that group I was the least retentive group of all [p<0.05], and group 3 and group 4 were significantly more retentive than group 2 [p<0.05].There was no significant difference between group 3 and group 4. The surface treatment of carbon fiber posts significantly improved their retention to composite resin