[Effict of 2% Chlorhexidine on Sheur Bond Strength of Composite Resins to Dentin]

Background and Aim: Intracanal medicaments can affect the bond strength of composite to dentine. The aim of this study was to evaluate the effect of 2o/o chlorhexidine [CHX] gel as an intracanal medicament on shear bond strength of three different composite resins to dentin.

Materials and Methods: In this in-vitro study, 60 intact extracted human premolars were utilized. Each tooth was sectioned vertically and dentin of the buccal surface was exposed. Then, specimens were divided into six groups of l0 teeth. In groups l-3, dentin was exposed to CIIX and in groups 4-6, dentin was exposed to saline. All prepared surfaces were rinsed with distilled water and dentin bonding agent specific for each composite was applied on the dentin surfaces.2100, 2350 and P90 composites were applied to the treated swfaces and cured. The shear bond strength was recorded in Newtons and converted to MPa. Data were analyzed using the Kruskal-Wallis and Mann- Whitney U tests.

Results: The lowest mean shear bond strength was reported for normal saline and 2100 composite group [18.47 MPa] and the highest for CHX and 2350 grotry [42.26 MPa]. No statistically significant difference in bond strength values was found between normal saline and CHX groups [p>0.05]. There was a significant difference in bond strength values of different composite resins in normal saline [p<0.05] and also in CIIX groups b<0.05].

Conclusion: chlorhexidine gel 2o/o slightly but not significantly increases the mean shear bond strength of composite to dentin. The type of composite influences the shear bond strength to dentin

[Effect of triple antibiotic paste on bond strength of composite to dentin:an in vitro study]

Considering the increasing use of antibiotics in root canal therapy and the possible effects of intracanal medicaments on the bond strength of composite restorations, the aim of this study was to evaluate the effect of triple antibiotic paste on shear bond strength of three types of composite resins to dentin.In this in-vitro, experimental study, the enamel of 60 extracted premolars was ground parallel to the longitudinal axis of the teeth in order to produce flat dentin surfaces [5 mm[2] minimum surface area]. The samples were divided into six groups. In the control group, dentin surfaces were stored in saline solution and in the experimental groups, dentin surfaces were exposed to triple antibiotic paste for 10 days. After washing and drying, Single Bond was applied for dentin bond to Z100 and Z350 composites. Adhesive resin was used for bond to to P90 composite. Composites were applied on the dentin surfaces in six groups and cured in four directions. The shear bond strength was measured by Instron machine. The data were analyzed by t-test, one-way ANOVA and Tukey's test. The highest mean shear bond strength was found in Z350 composite group following the use of triple antibiotic paste [38.75 MPa] and the lowest mean strength was found in Z100 composite group following the use of triple antibiotic paste [14.64 MPa]. The mean shear bond strength of P90 and Z100 composites [in contrast to Z350 composite] was higher in the saline compared to the triple antibiotic paste groups [P=0.1]. The differences between saline and antibiotic groups were not significant [P=0.959] but the difference in this regard among the three types of composites was significant.The results of this study showed that use of triple antibiotic paste has no effect on the shear bond strength of composite to dentin but the type of composite significantly affects the shear bond strength

Shear bond strength between aged hybrid and new flowable composite resins using different bonding agents

Flowable composite is an appropriate choice for repairing old composite restorations because of its conservative nature, easy application and various colors available on the market, The aim of this study was to evaluate the shear bond strength between old hybrid and new flowable composite resins using Adhes, Single bond, Prompt L Pop and no dentin bonding agents. Eighty acrylic cylinders were fabricated with a standard cavity in the center. Tetric Ceram hybrid composite was placed in the cavities and cured. The cylinders were divided into two groups; one group was kept in water for one month and was then randomly divided into four subgroups. Dentin bonding agents were not used in the first subgroup but the selected bonding agents were applied to the cylinders in the other subgroups. Tetric Flow composite was placed on the primary composite. The same procedure was used for the second group except that the samples were not stored in water for one month. The shear bond strength was measured using a universal testing machine. The data were subjected to LSD variance and independent t-analysis. Shear bond strength values ranged from 33.27 to 16.62 MPa in the first group [in decreasing order: Adhes, Single-bond, control and Prompt L pop subgroups] and from 32.73 to 18.15 MPa in the second group [in decreasing order: Adhes, Single-bond, Prompt L pop and control subgroups]. In the first group, a significant difference was observed between the control versus Adhes and control versus Single bond subgroups and also between the Adhes and Prompt L pop and finally between the single bond and Prompt L pop subgroups. There was no significant difference between the control versus Prompt L pop and Adhes versus Single-bond subgroups. The results obtained in the 2nd group were similar to the first group. The shear bond strength between aged hybrid and new flowable composite resin may increase after application of dentin bonding agents

Effect of different adhesive systems on microleakage at the amalgam/composite interface

Ditching and marginal defects of amalgam restorations can cause microleakage, recurrent carries, pulp hypersensitivity and finally loss of the tooth. The complete replacement of large restoration is time consuming, difficult and may potentially damage the pulp. Therefore in cases were there is no sings of recurrent caries, composite repair can be chosen as an alternative. The purpose of this study was to compare the effect of different bonding agent application on microleakage between flowable composite and amalgam. Standard calss V amalgam preparations were prepared on 60 carries free premolars and the cavities were filled using amalgam. After 24 hours, a 1 mm cavity on the occlusal margin of the class V restorations was prepared and specimens were divided randomly into four treatment groups: First group was filled with flowable composite and Single bond. Second group was filled with flowable composite and SE bond. Third group was filled with flowable composite and Prompt-L-pop. Fourth group Was filled with flowable composite without denting bonding agent. Specimens were thermocycled and sealed with fingernail polish except the composite-amlagam interface, then immersed in basic fuchsine for 24 hours. Specimens were sectioned and microleakage was assessed. The data were analyzed using Kruskal-Wallis test and Mann-Whitney U test. The results indicated that dentin bonding agent is effective in decreasing the degree of microleakage in amalgam-flowable composite interface and also the clearfil SE bond was more effective than Prompt-L-pop. But there was no significant statistical difference in microleakage between SE bond and Single bond. The application of dentin bonding agents in repair of amalgam retoration using flowable composite decreases microleakage but more researches should be performed