ABSTRACT
AIMS AND OBJECTIVES: Conventionally, composites are cured using halogen-based light-curing units (LCUs). However, recently, light-emitting diode (LED) LCUs have been introduced commercially, claiming many advantages, yet producing comparable bond strength even when cured with single LED LCUs. This present study was undertaken to compare the shear bond strength of orthodontic brackets bonded to teeth with conventional halogen LCU (3M ESPE Elipar 2500) and LED LCU (3M ESPE Elipar FreeLight 2) and to determine the site of bond failure. MATERIALS AND METHODS: Fifty extracted human bicuspid teeth were randomly divided into two groups of 25 each. All the teeth were etched and primed. Then, orthodontic brackets were bonded onto the teeth with the light-cured adhesive (Transbond XT, 3M Unitek), and the adhesive was cured with halogen LCU and LED LCU for Group I and Group II, respectively. The brackets were then subjected to shear stress using a Hounsfield universal testing machine at a crosshead speed of 1 mm/min. The force was recorded in Kgf and converted to MPa. The residual adhesive was scored based on the modified adhesive remnant index (ARI) using an optical stereomicroscope. The data were analyzed using the Student's t-test and the Mann-Whitney test at a significance level of 0.05. RESULTS: The results have shown that there is no significant difference between the shear bond strengths and the ARI scores of both the groups. CONCLUSION: From this study, it can be concluded that (1) LED LCUs containing even only a single LED can cure the composite as well as a halogen-based LCU; (2) there is no statistically significant difference in the shear bond strengths of the two groups; and (3) the ARI scores show no significant difference.
ABSTRACT
AIMS AND OBJECTIVES: The introduction of ceramic brackets was a much-heralded development in the field of orthodontics. However, the increased frictional resistance with these brackets led to the development of ceramic brackets with metal slots, which claimed to combine the esthetics of ceramic brackets with the low frictional resistance of metal brackets. Hence, this study was undertaken to evaluate the rate of canine retraction and the amount of anchor loss while using ceramic brackets and ceramic brackets with metal slots and with conventional preadjusted edgewise appliance (PEA) metal brackets. MATERIALS AND METHODS: The patient sample consists of 12 patients. Six patients received ceramic brackets on one canine and conventional PEA metal brackets on the opposite canine within the same arch. The other six patients received ceramic brackets with metal slot on one canine and conventional PEA metal brackets on the opposite canine within the same arch. Unpaired t-test was used to analyze the data using SPSS version 20 (3M Unitek, Bangalore, Karnataka, India). The rate of retraction was calculated for individual canine retraction after initial leveling and aligning. Anchor loss was also calculated using the pterygoid vertical to the mesiobuccal cusp of the upper first molar on the lateral cephalograms. RESULTS: The result of this study showed that the difference in the rate of retraction between ceramic brackets with metal slot and conventional PEA metal brackets and ceramic bracket while clinically significant was not statistically significant. The difference in the amount of loss of anchorage of both the groups was not statistically significant. CONCLUSIONS: Incorporation of the metal slot in ceramic brackets has reduced frictional resistance for more efficient and desired tooth movement. Ceramic brackets with metal slot generate lower frictional forces than ceramic brackets but higher than conventional PEA metal brackets.
ABSTRACT
BACKGROUND: There is necessary of dry operating field for bonding of orthodontic brackets. The presence of moisture can alter the bond strength. Hence, the aim of the present study was to evaluate the shear bond strength of orthodontic brackets with different adhesives. MATERIALS AND METHODS: In this in vitro study, a total of 100 orthodontically extracted premolars with sound crown structure were divided into 4 equal groups of different primers. Bonding on the buccal surface of all teeth was done after acid etching with upper premolar brackets using different primers followed by light curing. Shear bond strength was evaluated with or without salivary contamination with both adhesives. A shear force for deboning the bracket was done with universal testing machine. The debonded specimens were examined at ×10 magnification to check site of bond failure and remaining adhesive on tooth using adhesive remnant index (ARI). The obtained data were statistically evaluated using SPSS 20 for Windows (SPSS Inc., Chicago, IL, USA) using ANOVA, Kolmogorov-Smirnov, and Levene's test at the statistical significance of P < 0.05. RESULTS: Transbond Plus showed higher shear bond strength of 8.92 MPa under dry and 5.65 MPa with saliva contamination over Transbond XT of 7.24 MPa under dry and 2.43 MPa with saliva contamination, respectively. Higher ARI score was found without contamination in both adhesives. CONCLUSION: Transbond Plus hydrophilic resin had good shear bond strength under both dry and contamination condition compared to hydrophobic Transbond XT resin material.
