Objective: The objective of this study was to compare the tensile bond strength of metal brackets bonding to glazed ceramic surfaces using three various surface treatments.Materials and Methods: Forty two glazed ceramic disks were assigned to three groups. In the first and second groups the specimens were etched with 9.5% hydrofluoric acid (HFA). Subsequently in first group, ceramic primer and adhesive were applied, but in second group a bonding agent alone was used. In third group, specimens were treated with 35% phosphoric acid followed by ceramic primer and adhesive application. Brackets were bonded with light cure composites. The specimens were stored in distilled water in the room temperature for 24 hours and thermocycled 500 times between 5oC and 55oC. The universal testing machine was used to test the tensile bond strength and the adhesive remenant index scores between three groups was evaluated. The data were subjected to one-way ANOVA, Tukey and Kruskal-Wallis tests respectively.Results: The tensile bond strength was 3.69±0.52 MPa forfirst group, 2.69±0.91 MPa for second group and 3.60±0.41 MPa for third group. Group II specimens showed tensile strength values significantly different from other groups (P<0.01).Conclusion: In spite of limitations in laboratory studies it may be concluded that in application of Scotch bond multipurpose plus adhesive, phosphoric acid can be used instead of HFA for bonding brackets to the glazed ceramic restorations with enough tensile bond strength.

Background and Aim: Fluoride releasing adhesives are favorable for bracket bonding since they decrease the risk of demineralization around orthodontic brackets given that they provide acceptably high shear bond strength (SBS). The aim of this study was to evaluate the SBS of resin-modified glass ionomer cements (RMGIC) reinforced by nano-zinc oxide (NZnO) and nano-hydroxyapatite (NHA) particles in comparison with composite resins.Materials and Methods: In this experimental study, 80 extracted human premolars were used. The teeth were randomly divided into 4 groups as follows: Group I: Transbond XT as the control group, Group 2: RMGIC (Fuji II LC), Group 3: RMGIC with 5% NHA and Group 4: RMGIC with 2% NZnO. After enamel etching, brackets were bonded. The SBS was calculated for each group. The percentage of adhesive remained on the enamel was quantified by calculating the adhesive remnant index (ARI). The data were analyzed using one-way ANOV A and the Kruskal Wallis test.Results: According to the results of ANOV A, there were no significant differences in SBS of groups (P=0.075). The mean SBS in groups 1 to 4 was 15.43±4.61, 14.95±4.34, 17.97±3.65 and 17.08±3.59 MPa, respectively. According to the Kruskal-Wallis test, there were no significant differences in degree of ARI among groups (P=0.413).Conclusion: The SBS was similar among all groups and adding NZnO and NHA particles had no negative effect on SBS of RMGIC. In all groups, less than half the adhesive remained on the enamel after bond failure.

Background and aims: Diverse gauges have been used to measure and determine bracket height for correct bracket positioning. The aim of the present study was to determine and compare bracket positioning accuracy by using height bracket positioning gauge (HBPG) and Boone gauge (BG).Materials and methods: Nineteen sets of stone models were prepared from one patient. One set was employed to determine the ideal position of brackets, and the remaining nine pairs of sets for bracket placement by nine clinicians using HBPG and BG. Teeth were then sectioned from the stone models and placed inside acrylic molds, photographs were taken and imported to a computer. In two groups, the position of each bonded bracket was compared in three aspects of vertical, mesiodistal and angular with the ideal position of every bracket. Finally, bracket positioning errors were measured.Results: Mann-Whitney U test demonstrated significant differences in the means of vertical error between the HBPG group and BG groups (P<0.001), while there were no significant differences between mesiodistal and angular errors. Factorial ANOVA revealed that gauge and tooth type, and the position of tooth on the right and left side of the mouth play a ma-jor role in the rate of vertical error.Conclusion: Vertical accuracy of bracket positioning by the use of HBPG is more than that by BG. However, there is no difference between two gauges in relation to the mesiodistal and angular errors.

Background and Aims: The aim of this study was to evaluate the effect of application of two types of primers over bracket bases on the shear bond strength (SBS) and mode of bond failure.Materials and Methods: In this study, 75 human premolar teeth were divided into three equal groups. In group 1 (control), after surface preparation of enamel by conventional method (acid etching+primer) brackets were bonded with Transbond XT composite. In group 2 (TX), brackets were bonded to enamel same as the first group but Transbond XT primer were used on bracket bases before placement of composite. In group 3 (PL), Transbond plus primer was applied on bracket bases before placement of composite. After 24 h, the SBS test was performed by universal testing machine at crosshead speed of 0.5 mm/min. Then, adhesive remnant index (ARI) scores and percentage of cohesive fracture were determined using stereomicroscopy. SBS data were analyzed by one-way ANOVA and Duncan tests. Kruskal-Wallis and Mann-Whitney tests were used to analyze ARI and cohesive fracture results.Results: There was significant difference in SBS values among the groups (P<0.001). The highest SBS was shown in TX group and the lowest was seen in PL group. There was no significant difference between control and TX groups in ARI scores (P=0.199). No significant difference was found in cohesive fracture values between the groups (P=0.093). Both the control and TX groups showed significant difference in ARI scores and cohesive fracture compared with the PL group in all of the comparisons (P<0.001).Conclusion: Application of Transbond XT primer over bracket base affects the bond strength and failure mode. Transbond XT primer increased the bond strength but Transbond plus primer decreased it.

We define a new function-valued inner product on L2(G), called j-bracket product, where G is a locally compact abelian group and j is a topological isomorphism on G. We investigate the notion of j -orthogonality, Bessel's Inequality and j -orthonormal bases with respect to this inner product on L2(G).

Background and Aim: Recycling of brackets can significantly reduce the price of fixed orthodontic appliances but if the bond is more prone to failure during treatment, this potential benefit will disappear. The aim of this study was to investigate the effect of chemical recycling on bond strength of metal orthodontic brackets and failure pattern of recycled brackets. Material and Methods: In this experimental study Instron machine was used to measure shear bond strength (SBS) of brackets in two stages on 60 human maxillary first premolars using No-Mix composite. Shear bond strength and pattern of failure were compared between recycled and new brackets in two stages. Data were analyzed by ANOVA and Duncan tests. Adhesive Remnant Index was evaluated in different groups by Pearson Chi-square test. P<0.05 was considered as the limit of significance. Results: Statistical analysis showed that the mean values of SBS for new bracket group was 12.00 MPa and for recycled group and double recycled group, 9.94Mpa and 10.00 MPa respectively. A significant reduction (about 18%) in bond strengths of brackets was observed at the first time of recycling. Recycling at the second time had no significant influence on the bond strength. Pattern of bond failure of these brackets showed that a great amount of residual adhesive material was remained on the teeth surfaces after debonding of recycled brackets which indicates that cleaning the teeth surfaces after debonding of recycled brackets is more time consuming. Conclusion: Based on the results of this study, before using recycled brackets, several advantages and disadvantages must be considered.

Introduction: Providing reliable bonding of the bracket base and the zirconia surface is required to apply orthodontic force. The purpose of this scientific experiment was to evaluate the efficacy of three different methods of surface preparation for Zirconia, including surface roughening, sandblasting and the Nd: YAG laser, in the shear bond strength (SBS) of the orthodontic brackets. Methods: Fifty-four discs of zirconia were divided into three groups of 18: A) Hydrofluoric acid etching, B) sandblasting, and C) Nd: irradiation using the power of 1. 5 W for 10 seconds. After bonding the brackets, the samples were slowly thermo-cycled (1000 times) for 24 hours. The SBS test was performed by a universal testing machine at a head speed of 0. 5 mm/min. The adhesive remnant index (ARI) was scored at a magnification of 10 in the stereo microscope. All data were collected and analyzed using the variance, Kruskal-Wallis, Tukey, Don, and Weibull tests (α = 0. 05). Results: The HF acid etching group (6. 11± 0. 94 MPa) had the highest SBS, which was followed by the laser group (6 ± 0. 61 MPa) and the sandblast group (3. 1080 ± 0. 82 MPa). There was a significant statistical difference between the laser and HF groups and the sandblast group (P < 0. 05) and no significant difference between the HF group and the laser group (P = 0. 03). Conclusion: Based on the obtained bond strength, the Nd: YAG laser with a power of 1. 5 W could be a substitute treatment method for the HF acid-etching.