Statement of Problem: Evaluation of new adhesives efficacy in bonding orthodontic brackets to enamel has led to different results. The new measuring method, micro-shear bond strength, is preferred as an accurate method due to its ability to reduce confounding factors.Purpose: The purpose of this study was to evaluate and compare the micro-shear bond strength of three different adhesive systems for enamel surface preparation before bracket bonding.Materials and Method: In this experimental study, 90 extracted premolars were randomly divided into three groups of 30. Transbond XT was bonded to enamel after enamel surface preparation with acid etch in the first (control) group, Transbond plus self-etch primer in second group, and Adper prompt L-pop self-etch adhesive in third group. Then each group was randomly divided into two subgroups of 15. Micro-shear bond test was performed after 24 hours (T1) and 3-months (T2). Bond failure mode was also evaluated according to Adhesive Remnant Index (ARI). Two way ANOVA and Tukey tests were used for bond strength evaluation in groups, and mode of bond failure was analyzed with Kruskall Wallis and Mann Whitney tests.Results: The highest bond strength was found in acid etch group (29.17 MPa). Difference of bond strength at two intervals was statistically significant in all groups ( p <0.001). Bond strength difference between T1 and T2 was also significant in three groups ( p <0.001). However changes over time in three groups did not reveal any significant differences ( p = 0.091). Bond failure analysis demonstrated significant differences in ARI between groups.Conclusion: Bond strength of acid etch group was the highest and self etch primer showed higher bond strength than self etch adhesive group. Less adhesive remnant was found in self etch group.

Background & Aim: More than 30 years has passed since introduction of glass-ionomer cement as a dental restorative material, luting cement and liner. Although they are sensitive to moisture and desiccation during the initial setting stages, relative poor physical properties because of chemical bonding to tooth substrate, and long-term esthetic quality, they are recommended for restoring anterior and posterior primary teeth, cervical lesions and root caries of permanent teeth. In this study, shear bond strength of Fuji II was compared with of ariadent glass-ionomer cements. Materials & Methods: Thirty intact extracted primary molars were prepared for this study. Selected teeth were divided in two groups of 5. Sample were free of caries, fracture, crack, discoloration or any structural abnormality. The dentin of buccal surface of teeth were exposed by microtome apparatus. The surface was conditioned by polyacrylic acid (10%) for 20 seconds. Glass ionomer cements (Fuji II, and Ariadent) were prepared in a plastic cylinders (15 of each) and attached to the dentin of teeth horizontally. Shear bond stength of materials was measured by instron (Model 1159).Results: Mean shear bond strength of Ariadent cement was 4.2±1.9 Mpa while 7.4±1.5 Mpa was of Fuji II cement (P=0.000).Failure mode was similar between two cements (P=ns). The most prevalent type of failure mode was cohesive failure leaving a firmly attached thin and homogenous layer of cement to dentin, in both groups.Conclusion: It appears that shear bond strenght of Ariadent cement to primary tooth is much lower than of Fuji II.

Aim: The aim of this study was to compare the etching effect of porcelain with Hydrofluoric acid (HF) one shear bond strength using one coat bond and self cure composite.Methods & Materials: The study was conducted experimentally using observation as its technique. 40 porcelain cubes were prepared and assigned into 4 groups. Group I specimens were treated with 35% phosphoric acid.Subsequently one coat bond was applied to bond the bracket, group II specimens were made fresh with fine diamond bur, treated with a 35% phosphoric acid and one coat bond was applied to bond the bracket, group III specimens were treated with a 20% hydroflouric acid (HF) and Nomix composite bond was applied to bond the bracket, group IV specimens were treated with a 40% HF acid and the same procedure in the group III was followed. The Instron machine was used at a crosshead speed of 0.5 mm/min to test the shear bond strength.Result: The shear strength was 2.47±1.8Mpa for group I, 5.64±2.6Mpa for group II, 3.28±1.8Mpa for group III and 3.03±2.6 for group IV. The overall difference between the four groups was statistically significant (P<0.05). Conclusion: The use of fine diamond bur and 35% phosphoric acid for Etching and use of one coat bond can achieve a successful bond between either use only phosphoric acid or 20% HF acid-Etched with No mix composite and 40% HF acid etched with No mix composite.

Aim: The aim of this study wasto investigatethe effectofHEMA as a primingagentonshearbondstrengthof composite resin to dentin before the application of an enamelbonding agent. Occlusal dentin of thirty six intact extracted premolars were exposed, etched and blot dried. Teeth were divided in four groups each consisted at a specimens. In group one, a mixture of 35% HEMA and acetonewas used to prime the dentine before enamel bond. In group two, a mixture of35% HEMA and water was used as priming agent. In group threy only enamel bonding agent was applied on dentin. In group four, scothbond multipurposesystem was employed as bonding agent. Shear bond strength test was carried out one week after preparation using an instron testing machine at a ckossheasspeed of 15 mm/min. Results: The results indicated that group four exhibited significantlyless shear bond strength than the orthers ans orther differences were not statisficaly significant. Conclusion: It was concluded that utilizing HEMA as a primingagent preceding the appliceation of enamel bond significantly increased the shear bond streugth of compositeresin to dentin.

Introduction: Porcelain fracture is a relatively common problem in clinical dental practice. Various methods have been proposed for repairing porcelain fractures including direct composite resin repair or construction of a porcelain laminate veneer and its cementation with a resin cement. Evaluation of shear bond strength of porcelain repair methods was the purpose of this study.Methods: Twenty feldspathic porcelain discs (10 mm in diameter) were fabricated. The samples underwent air-born abrasion with an aluminum oxide and etching with HF, and were then ultrasonically cleaned and randomized into two groups: 1-repair with porcelain disc (7 mm in diameter) with light cure cement (Choice 2); and 2-repair with resin composite (Clearfil AP-X). We measured the shear bond strength of the samples by Zwick Roll at 0.5 mm/min crosshead speed.Results: The resin composite group had the highest shear bond strength (12.91 MPa). We found no significant differences between the choice and composite groups (p=0.970).Conclusions: Our findings indicate that resin composite yields acceptable shear bond strength to be used in porcelain repair.