Background and Objective: The aim of this study was to measure the shear bond strength of composite resin to human dentin surface bonded with three different bonding systems.Subjects and Methods: The crown surface of 66 extracted human third molar teeth were abraded with trimer in a wet environment until the dentin surface was exposed, and they were polished with silicon carbide paper 400 and 600 grit. Then, all the smooth smear layer samples were randomly classified into three equal groups. We used bonding according to the instruction of the manufacturer (the first group Single Bond, the second group BC Plus and third group Charm Bond).Then, the composite resin was bonded to the tooth surface by plastic tube (diameter: 1.8 mm, height: 5mm).Finally, shear bond strength was determined by universal testing machine (LMT 100).Results: The variance analysis (ANOYA) P value=0.000 revealed the mean of shear bond strength is different between three groups. The mean shear bond far first, second and third groups are 15.25 MP, 6.84 MP, 8.59 MP, respectively. The multiple comparison with THKEY test showed that there is different significance between group one and the other two groups which did not differ significantly.Conclusion: All in all, we found out that greatest shear bond strength to dentin is the American Single Bond, which is better than Korean product (BC Plus and charm Bond).

Many studies have shown that microorganisms are the main cause of pulpal diseases and the main purpose of root canal therapy is their elimination from the root canal system. Antiseptic agents are used to reduce bacteria but their antibacterial activities differ from in vivo to in vitro studies and might be inactivated by dentin and its components in root canal space. This study was designed to investigate the effect of dentin on antibacterial activity of different antimicrobial agents.Materials and Methods: In this experimental study, two antibacterial agents (sodium hypochlorite and chlorhexidine) with different concentrations were used in four experimental groups: Group 1: dentin, Group 2: demineralized dentin with EDTA, Group 3: dentin matrix and Group 4: dentin mineral component. The species used in this study was Entrococcus faecalis. Different concentration of agents was added to mixture of each experimental group and bacteria. At the baseline and after one and 24 hours, samples were collected and cultured. After incubation period, colonies were counted. Data were analyzed by Tukey test with p<0.05 as the limit of significance.Results: 2% and 0.2% chlorhexidine, and 5% sodium hypochlorite solutions at the three studied times eliminated Entrococcus faecalis completely. 1% sodium hypochlorite eliminated all bacteria in 1h and 24 hs. Statistical analysis showed significant differences between experimental and control groups (P<0.05). Sodium 1% hypochlorite at time 0, could reduce bacteria significantly (P<0.05) but didn’t eliminate them completely.Conclusion: Inactivation of intracanal antiseptics was not observed in this study. As elimination of bacteria occurred, application of these antibacterial agents is recommended in endodontic treatment. Further investigations on other antibacterial agents, other concentrations and shorter time intervals are recommended.

Introduction: Many clinical studies have evaluated different dentin bonding agents in treatment of dentin hypersensitivity (DH). But the use of acid is controversial and the effect of self-etch bonding agents isn't clearly defined. Objective: The aim of this study was to compare two dentin bonding systems, prompt (self-etch bonding system) and excite(with and without acid) in treatment of DH.Materials and Methods: This clinical study had a double-blind, randomized, subject design and was performed on 41 sensitive teeth with DH. We had 3 groups e1 (we used excite without acid), e2 (excite with acid) and p (prompt). Two stimuli (cold water 20‎ْc and compressed air) and two methods for evaluation ((VAS (Visual Analogue Scale) and response time)) in 3 times (before treatment, immediately after treatment and two weeks after it) were used.Results: All treatments showed significant reductions in DH. In the VAS scores, no significant difference was found. But in the response time, the groups e1, P significantly showed better results than group e2.(P<0.05)Conclusion: Treatment effects were improved in all groups with time. Use of acid before the bonding agent had a negative effect but there was no significant difference between prompt and excite (without acid etching). It's worth nothing that the measurement of response time to stimulus compared to the VAS method is more accurate in evaluation studies of pain rate.

Background and Aim: To evaluate the bond strengths of FRC posts (Glassix "Nordin dental/Swiss" and Matchpost "RTD/ France") to root dentin after silanization. The null hypothesis tested was that silanization would produce greater bond strength.Materials and Methods: Roots of 40 human freshly extracted maxillary central incisors were endodontically treated and were divided into 4 group of each 10 (n=10.) They received the following treatments. Group 1: Glassix post + silane primer; Group 2: Glassix posts without silane primer; Group 3: Matchpost + silane primer;  Group 4: Matchpost without silane primer. The posts were cemented with panavia F2.0 dual cure resin cement. Each root was cut into 3 slices (2mm height) representing 1/3 coronal, middle, and apical portions respectively. After push-out  bond strength testing (at the cross head speed of  0.5 mm/min), the type of failure at the interface was determined. Results: Silanization of fiber posts had no effect on shear bond strengh (p>0.05). Without consideration of silanization, type of post had also no effect. (p>0.05). The apical third of the specimen had the greatest bond strength (p=0.001).Conclusion: Neither silanization of fiber post surfaces, nor the type of fiber post seem to have any statistically significant difference on shear bond strength of FRC posts to root canal dentin. Most of tested specimen had an adhesive failure mode at the interface of cement-dentin.

Introduction: Today, much of the researches and innovations in dental materials are focused on simplification of the bonding procedures. The aim of this study was to assess shear bond strength (SBS) of three auto-adhesive dual-cured resin cements to dentin.Materials & Methods: In this in vitro experimental study, 40 intact human Third molars were selected and randomly divided into 4 groups of 10 teeth. Group I (Control group): After 15 seconds of etching and application of Excite DSC Bond (Ex), Varilink II (Var II) composite was injected into the plastic ring and light cured. Group II: RelyX Unicem (RX) was injected into the plastic ring and light cured after 30 seconds (according to manufacturer's instruction). Group III: Maxcem (Mc) was injected into the plastic ring and light cured after 30 seconds (according to manufacturer's instruction). Group IV: Multilink Sprint (MS) was injected into the plastic ring and light cured after 30 seconds (according to manufacturer's instruction). After thermal cycling (1000 cycle, 5-55oC), SBS were measured for each groups with a Zwick/Roell Universal Testing Machine. The data were analyzed by ANOVA and Scheffe tests.Results: The mean SBS and Standard deviations for groups I, II, III and IV were 12.95±2.64, 6.73±0.79, 3.01±0.90 and 4.60±0.75 MPa respectively. Statistical analysis revealed that: 1. The mean SBS of Var II was significantly higher than the other groups (P<0.05). 2. The mean SBS of Mc and MS were significantly lower than RX (P<0.05).3. The mean SBS of Mc and MS were not significantly different (P>0.05).Conclusion: Bond strength of the auto-adhesive dual-cured resin cements (RX, Mc, MS) to dentin was lower than Var II composite combined with Ex bond. Bond strength of RX was higher than Mc and MS.

With the increase in lifespan there are many concerns related to ability of the hard tissues such as teeth to meet the physical demands over an extended period of function. The dentin has a special microstructural feature that governs its mechanical behavior, e. g., fracture mechanics: cylindrical tubules that are called dentin tubules. These tubules are gradually occluded in the elderly. The present study is aimed to investigate the effects of microstructure and its aging-related changes of the considered fiber-reinforced composite dentin on the fracture behavior and crack propagation trajectory, utilizing linear elastic fracture mechanics and finite element method. Obtained results indicate that the crack propagation path depends on geometrical microstructure of the dentin as well as respective mechanical properties and arrangement of dentin tubules. Also our results delineate that occlusion of dentinal tubule due to the aging plays a significant role at crack propagation trajectory and behaves as a barrier to crack growth.

Introduction: Determining working length is regarded as an important step in root canal treatment, for which electronic apex locator can be applied. New apex locators are preferred, since they work via applying alternating current. Furthermore, the two factors of dentin specific resistance and capacitance seem to be effective principles in their operating. Therefore, this study aimed to determine and compare the dentin capacitance in young and old teeth.Methods: In order to glean the study data, 60 human permanent teeth were collected consisting of 30 permanent teeth under twenty-five years and 30 permanent teeth over sixty year. The sixty samples of same dimensions were prepared from mid levels of the teeth roots. The capacitance circuit rates created in three frequencies of 100 HZ, 1KHZ and 10KHZ were measured. Moreover, in order to analyze the study data, ANOVA and Mann-Whitney tests were utilized.Results: The mean value of capacitance circuit teeth under twenty five years and over sixty years respectively involved 60 and 137 in 100HZ, 2.5 and 9.5 in 1KHZ and 0.05 and 0.3 in 10KHZ, which this difference was proved to be statistically significant (P Value =0.000) Conclusion: The study findings revealed a different capacitance between young and old teeth. Regarding the influence of this factor in the operating principle of apex locators, calibrate the device may be necessitated while applying it in young and old teeth.

Introduction: The present study aimed to compare the shear bond strength (SBS) of the resin-modified glass ionomer (RMGI) to primary dentin using different dentin conditioners. Materials and Methods: The dentin surfaces of 80 primary molars were conditioned using four different methods: etching with 37% phosphoric acid, 10% polyacrylic acid, 5% NaOCl, and no surface treatment. Dentin surfaces were restored with RMGI Fuji Π,LC cylinders. After 24 h, the shear bond strength tests were performed using Universal Testing Machine. Statistical analysis was performed using One-Way ANOVA followed by Tamhane Post hoc Test. A p-value less than 0. 05 was considered statistically significant. Results: Phosphoric acid produced the highest shear bond strengths, compared to all tested groups, which showed statistically significant differences with groups 3 and 4 (P=0. 043, P<0. 001). Subsequently, Polyacrylic acid showed a significantly higher SBS than group 4 (P=0. 046). Conditioning with NaOCl significantly increased the bonding strength of RMGI compared to the untreated group (P=0. 001). Untreated dentin had the lowest SBS compared to other tested groups. Conclusion: The conditioning step effectively improved the SBS of RMGI to primary dentin. Dentin conditioning with 37% Phosphoric acid for 5 sec showed the highest shear bond strength of RMGI.