Abdolrahim Davari; Soghra Yassaei; Mahdjoube Goldani Moghadam; H. Zoghi
Abstract
Aim: The objective of this study was to determine the effect of thermocycling on shear bond strengths (SBSs) of a light cured compositeafterdifferent thermal cycles.Materials and methods: 80 Bovine incisors were randomly divided into 4 groups of 20 teeth. Each teeth were etched with 37% phosphoric acid ...
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Aim: The objective of this study was to determine the effect of thermocycling on shear bond strengths (SBSs) of a light cured compositeafterdifferent thermal cycles.Materials and methods: 80 Bovine incisors were randomly divided into 4 groups of 20 teeth. Each teeth were etched with 37% phosphoric acid and brackets were bonded using a light cured composite (Resilience). Thermocycling was done between 5° C and 55° C for 500, 3000 and 6000 cycles in group 2,3 and 4 respectively. Teeth in group1 (control group) were not being thermocycled. The SBS values were measured by means of Dartec testing machine.
Results: The results showed significantly higher SBS values for the control group compared to test groups (2-3 and 4). No significant different was observed between test groups.
Conclusion: Thermal changes during thermocycling significantly reduce the mean SBS of conventional etch and rinse adhesive system (Resilience), but SBS in 500, 300 and 6000 cycles had no significant difference. Clinical significance: Alteration in values of shear bond strengths under thermocycling would be representative of expected behavior of orthodontic brackets in clinical situations.
Masood Feizbakhsh; Mehrdad Barekatain; Ehsan Borhani; Fatemeh Teimoori
Abstract
Aim: The aim of this study was to compare the shear bond strength [SBS] of two different light sources, light-emitting diode and quartz-tungsten halogen, under thermal cycle frequencies. Method and materials: Sixty human premolar teeth were divided into two groups, on which composite (Transbond ...
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Aim: The aim of this study was to compare the shear bond strength [SBS] of two different light sources, light-emitting diode and quartz-tungsten halogen, under thermal cycle frequencies. Method and materials: Sixty human premolar teeth were divided into two groups, on which composite (Transbond XT™ adhesive paste) cured with light-emitting diode in group I, and with quartz-tungsten halogen in group II. Samples thermocycled 500 cycles, the exposure to each bath was 10 seconds and the transfer time between the two baths was 10 seconds. 500 cycles between 5°C and 55°C were performed. An Instron testing machine [Dartec Hc.10, England] was used for the shear bond test at a crosshead speed of 1mm/min. Force was applied directly to the bracket–tooth interface. The load at failure was recorded by a personal computer connected to the test machine. SBS values were expressed in mega Pascal [MPa]. T-test was used to compare the shear bond strength between two groups. Results: The comparison of both groups indicated that the quartz-tungsten halogen groups demonstrated higher mean shear bond strength [p=19.947Mpa] than light-emitting diode groups [19.878Mpa]. There was no statistical difference in the shear bond strength values between the two light sources. [P value =0.918] Conclusions: Both light sources showed favorable shear bond strength performance and there was no statistical difference in the shear bond strength values between these two light sources.
