Purpose: The aim of this study was to investigate the shear bond strength of Core Max II® to bovine dentine. Materials and Method: For this purpose 60 sound permanent bovine incisors were gathered and divided into 4 groups of 15.After measuring the buccal enamel by means of radiography, the teeth were embedded in self-cure acrylic blocks. Then the depth gauges were prepared in the buccal side of teeth with straight diamond burs by high-speed hand piece. Next, the buccal enamel was grinded with a model trimmer to reach the specified depth into dentine. Dentine surfaces were polished with voco® composite polishing discs by low speed hand pieces and copious water to obtain a smooth surface free of irregularities. Group 1: In this group Core Max II® was directly bonded to bovine dentine.Group 2: Core Max II® was bonded to bovine dentine etched with 35 % phosphoric acid.Group 3: Core Max II® was bonded to etched bovine dentine by means of a self-cure dentine bonding agent.Group 4: (control group): Para Core was bonded to bovine dentin, which was etched and bonded as. After storing the specimens mentioned before in tap water, they were thermo Scientific-Research Journal I cycled for 500 times between55° & 5°c and were placed under universal testing machine INSTRON 1195 for shear bond testing.Results: The results were as follows: 1. The Shear bond Strength of Core Max II® to bovine dentine was zero and none of the specimens bonded to dentine. 2. Etching bovine dentine slightly increased the shear bond strength (1.27 Map) that although it was significantly higher than the first group, it could not be relied on for proper bonding.1. Application of bonding on etched dentine provided the highest bond strength (10.12 Mpa). 2. The bond strength of Para Core® to etched and bonded dentine was significantly lower than the third group (5.95 Mpa).Conclusion: Thus, in the light of the above - mentioned evidences and results, It can be concluded that Core Max II® cannot bond itself to unprepared dentine and it is imperative to use etching and bonding in order to obtain a good bond strength. Moreover, the other finding of this study was the mean thickness of bovine enamel, which was 1.2 mm in mid-buccal and 1.07 in gingival third and 1.05 in incisor third.

Hypothesis: Acrylic adhesives based on methyl methacrylate are thermoplastic polymers due to their linear polymerization. By adding two or more functional acrylate or methacrylate monomers it is expected that cross-linking may occur partially in leading to their chemical and thermal resistance improvements. It is also possible to increase their adhesion strength by adding acidic acrylate or acidic methacrylate additives. Methods: Compounds containing different percentages of methyl methacrylate monomer and polymethyl methacrylate were prepared. By measuring viscosity and contact angle, a suitable formulation based on surface wetting property was selected. Gel time measurement was used to find optimum amount of the second component of these two-component adhesives. For improving the properties, some modifying monomers including acidic monomer for increasing the adhesion property and a twofunctional monomer for crosslinking were added. Crosslink density was assessed by dynamic mechanical analysis. Thermal gravimetry analysis, chemical resistance and lap shear test were used to evaluate other properties. Findings: Results show that the lap shear strength of acrylic adhesive on aluminum substrate increased from 1. 1 MPa to 2. 7 MPa by adding acidic monomer as adhesion promoter. The strength increased to 3. 5 MPa by using 4% of ethylene glycol dimethacrylate as a two-functional crosslinking agent. The decomposition temperature at 5% weight loss increased from 194 to 248 ᵒ, C. The chemical resistance of cured adhesives in water, ethanol, acetone and toluene was also studied. The results show that the specimen without crosslinking was dissolved in acetone while the crosslinked specimen showed 14. 9% weight loss after 24 h immersion. Both the thermoplastic and thermoset adhesives showed good water resistance.

Background: Application of hemostatic agents can negatively affect the bond strength of adhesive systems to dental substrate. This study aimed to assess the effect of ferric sulfate on microshear bond strength of four total‑ and self‑ etch adhesives to dentin after water storage. Materials and Methods: In this in vitro study, 192 dentin slices with 2 mm thickness were made of 64 extracted sound human third molars. The samples were divided into 8 groups (n = 24) as follows: G1: Scotchbond Multi‑ Purpose, G2: hemostatic agent + Scotchbond, G3: Adper Single Bond, G4: hemostatic agent + Adper, G5: Clearfil SE Bond, G6: hemostatic agent + Clearfil, G7: Single Bond Universal, and G8: hemostatic agent + Single Bond Universal. Composite cylinders with 0. 7 mm diameter and 1 mm height were bonded to the surfaces. Each group was then divided into two subgroups (n = 12) for water storage for 24 h and 3 months. The microshear bond strength was then measured. Data were analyzed using the Shapiro– Wilk test, three‑ way ANOVA, one‑ way ANOVA, and Tukey’ s test (P < 0. 05). Results: Application of ferric sulfate decreased the bond strength of all bonding agents after both 24 h and 3 months of storage; but, this reduction was not statistically significant (P > 0. 05). Single Bond Universal at 24 h showed the highest and Adper Single Bond at 3 months showed the lowest bond strength (P < 0. 001). Conclusion: Dentin contamination with hemostatic agents negatively affects the bond strength of total‑ and self‑ etch adhesives.

Introduction: The purpose of this study was to compare marginal leakage of class II amalgam restorations lined with a resin- based desensitizing agent and a self-etching adhesive system with copal varnish. Materials & Methods: Fifty six freshly extracted human premolar teeth were divided into four groups. Class II box only cavity preparation was prepared on mesial and distal surfaces of each tooth While the cavities in two groups were lined with desensitizing agent; Viva Sens (A) and adhesive system; Clear Fil S3 Bond (B),one group was treated with copal varnish; Copalite (C), and last group was used as control, without any lining (D). Spherical high copper amalgam (Oralloy) was hand-condensed into each preparation, specimens were thermocycled, stained and sectioned. Microleakage was graded using a stereomicroscope. Microleakage scores were calculated and analyzed. Kruskal-Wallis and Mann-Witheny tests were used for analysis of data (a=0.05). Results: For the leakage values of groups A and B, T-test revealed less microleakage with Viva Sens (P<0.05). Kruskal-wallis test showed significant difference in four groups (P<0.05). Clear Fil S3 Bond showed less microleakage than control group, but leakage in copal varnish and Clear Fil S3 Bond was similar. Less microleakage was revealed with Viva Sens when compared with the other groups (P<0.05).Conclusion: Viva Sens reduced microleakage of Class II high copper amalgam restorations significantly more than the Clear Fil S3 Bond and copal varnish.

Statement of Problem: A few studies have been conducted about bioglass posts.Aim: The aim of this study was to compare bioglass posts with prefabricated metallic posts in clinical performance of extensive composite restorations for anterior endodontically treated teeth.Materials and Methods: Sixty endodontocally maxillary anterior teeth, with horizontally or vertically destruction were selected. Teeth were divided into two groups based on the kind of post: Metallic prefabricated parapost and bioglass post. Each group was divided into three subgroups based on anterior bite: normal, deep bite and edge to edge. Gutta-percha was removed from 2/3 of canal length for parapost and 1/3 for bioglass post. After etching with phosphoric-acid (37%) and applying dentine bonding Syntac, Duo cement was used for the adhesion of bioglass post and a self cured composite (Degufil) for parapost. Restoration was done with a hybrid composite (Heliomolar). Follow up studies, radiographically and clinically, were done every three months for a 1.5-year period. Exact Fisher and Pearson tests were used for data analysis.Results: Apical lesion was not observed in any of the radiographs. Post seal was increased by resin cement and dentin bonding agent. Post type did not significantly affect on the clinical success rate of the restorations. The retention of restoration, for both posts, was the same. Crown destruction had no significant effect on success rate. The type of anterior bite had a significant effect on success rate, as the total 6.6% failure rate was related to the patients with anterior deep bite.Conclusion: It is suggested to use metallic paraposts and bioglass posts, in extensive composite restorations for patients with deep-bite, more conservatively.

Statement of the Problem: Hemostatic agents may influence the bond strength of different bonding agents. Also, chlorhexidine has shown positive effects on bond strength values and their combination effect has not been reported yet.Purpose: The aim of this study was to evaluate the effect of contamination with a hemostatic agent on shear bond strength (SBS) of total- and self-etching adhesive systems and the effect of chlorhexidine application after removal of the hemostatic agent.Materials and Method: In this experimental study, the occlusal enamel of each sixty caries-free mandibular molars was removed and their midcoronal dentin was exposed. The specimens were then mounted in auto-polymerizing resin 1mm apical to CEJ. Then, the specimens were divided into 6 groups (n=10) based on contamination with a hemostatic agent (H), application of chlorhexidine (CHX) and the adhesive system used; and then were classified as Group 1: Adper Single Bond (ASB); Group 2: H+ASB; Group 3: H+0.2% CHX+ASB; Group 4: Clearfil SE Bond (CSB); Group 5: H+CSB; Group 6: H+0.2% CHX+CSB. Then, composite resin rods (4×2 mm) were built up on the dentin surfaces and after thermocycling, the SBS (MPa) was evaluated. Statistical analysis was performed using two-way ANOVA and post hoc Tukey tests (p< 0.05).Results: There were statistically significant differences between bond strength values of group 1 (ASB) and group 2 (H+ASB) (p< 0.001) and group 1 (ASB) and group 3 (H+CHX+ASB) (p<0.001). Similarly, significant differences were seen between group 4 (CSB) and group 5 (H+CSB) (p<0.001) and between group 4 (CSB) and group 6 (H+CHX+CSB) (p<0.001).Conclusion: Contamination with hemostatic agent reduced the SBS of both total- and self-etching adhesive systems. In addition, application of chlorhexidine after the removal of hemostatic agent had a negative effect on SBS of total- and self-etching adhesive systems.