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Background and objectives: The aim of the study was to evaluate the shear bond strength of brackets bonded with three bonding systems under laboratory conditions and to compare resin tag penetration after debonding. Materials and methods: The study was done on 60 extracted human premolar teeth, divided into three groups of 20 teeth each. Each group was bonded with three different types of bonding systems namely, the single component bonding system-Biofix, conventional light cured bonding system-Transbond XT and conventional chemical cured bonding system-Unite. The shear bond strength of the bonding system in each group was tested using Instron testing machine. After debonding, the samples were sectioned and viewed under scanning electron microscope to evaluate the resin tag penetration. The depth of penetration was measured with the measuring tool in the scanning electron microscope and marked. Results: The study revealed that the group bonded with Biofix has got the enough bond strength as the conventional chemical cured bonding system, Unite. The resin tag penetration into enamel was seen to be highest for Transbond XT, and for Biofix and Unite it was comparable and less. Conclusion: The shear bond strength values for Biofix is above the needed value to sustain normal oral and orthodontic forces and the residual resin tag remained after debonding are also less. Hence, the single component bonding system Biofix can be considered as a good material of choice for normal clinical bonding procedures.

Aims: The purpose of the study is to determine whether the nickel released from the stainless steel brackets have any cytotoxic effects on gingival fibroblast. Materials and Methods: Brackets are an important component of fixed orthodontics. Orthodontists are mainly concerned about the brands and various systems incorporated into the brackets. The manufactures claim bracket superiority without valid research. Since we are dealing with a biologic system factors like biocompatibility, cytotoxic potential should be taken into consideration before selecting an appliance to the patient. The cytotoxic activity of the media was investigated with MTT and comet assay. Results: The results of the study show that the amount of nickel leached is capable of bringing damage to the fibroblast. Conclusion: Our study concludes that nickel solution at minimal concentration of 1.18 μg could damage human gingival fibroblast and the nickel released from the different brands of the brackets are not uniform.

Background and Objectives: The purpose of this study is to evaluate the frictional resistance generated by conventional stainless steel, radiance ceramic bracket, self-ligating and composite brackets using a 0.019 × 0.025 stainless steel straight length wires in a 022 slot and to select brackets based on their frictional characteristic. Methodology: In order to conduct this study, four different types of bracket system were selected of the mclaughlin-bennet-trevesi (MBT) discipline. They are Group 1 - stainless steel, Group 2 - composite bracket Group 3 - (American Orthodontics) radiance ceramic bracket Group 4 - self-ligating bracket (SLB) (Empower). In this study, five maxillary brackets of an arch of each type were used. All brackets are 0.022 × 0.028" in preadjusted edgewise appliance which simulates the dental arch. Five brackets were bonded to a stainless steel bar of dimension 150 mm × 25 mm × 3 mm. The bracket-arch wire units were submitted to mechanical test with an Instron universal testing machine 3365. A testing apparatus or holding jig was designed to hold the bracket during the mechanical test. Each sample was pulled at a speed of 6 mm for 1 min. Descriptive statistical information including mean and standard deviation of maximum friction force was calculated for each bracket wire combination. Interpretation and Conclusion: The SLB has the least friction among the four groups. The ceramic bracket showed the highest friction followed by stainless steel bracket, composite bracket, and SLB.