Abstract
ABSTRACTOBJECTIVE: The aim of this study was to assess in vitro the influence of the CO2 laser and of the type of ceramic bracket on the shear bond strength (SBS) to enamel. METHODS: A total of 60 enamel test surfaces were obtained from bovine incisors and randomly assigned to two groups, according to the ceramic bracket used: Allure (A); Transcend (T). Each group was divided into 2 subgroups (n = 15): L, laser (10W, 3s); C, no laser, or control. Twenty-four hours after the bonding protocol using Transbond XT, SBS was tested at a crosshead speed of 0.5 mm/min in a universal testing machine. After debonding, the Adhesive Remnant Index (ARI) was evaluated at 10 x magnification and compared among the groups. Data were analyzed by one-way ANOVA, Tukey’s, Mann-Whitney’s and Kruskal-Wallis tests (α = 0.05).RESULTS: Mean SBS in MPa were: AL = 0.88 ± 0.84; AC = 12.22 ± 3.45; TL = 12.10 ± 5.11; TC = 17.71 ± 6.16. ARI analysis showed that 73% of the specimens presented the entire adhesive remaining on the tooth surfaces (score 3). TC group presented significantly higher SBS than the other groups. The lased specimens showed significantly lower bond strength than the non-lased groups for both tested brackets.CONCLUSION: CO2 laser irradiation decreased SBS values of the polycrystalline ceramic brackets, mainly Allure.
Highlights
The use of ceramic brackets has become widespread in orthodontic treatments due to the increased number of adult patients seeking care and esthetic appliances.[1]
The difficulties for debonding ceramic brackets can be attributed to the high bond strength and to the low fracture strength of ceramics,[5,6] which can lead to iatrogenic enamel damages, bracket fractures and longer clinical chairtime.[1,2,3,4,5,6]
The shear bond strength (SBS) values were statistically lower in the CO2 laser irradiated specimens for both Allure and Transcend tested ceramic brackets
Summary
The use of ceramic brackets has become widespread in orthodontic treatments due to the increased number of adult patients seeking care and esthetic appliances.[1] compared to conventional metallic brackets, ceramic brackets are more costly, with a questionable clinical performance, since their rigid properties may cause antagonist tooth contact wear. Conventional methods for debonding ceramic brackets (pliers and drills) can cause injuries and fractures to the enamel.[2,3,4,5] The difficulties for debonding ceramic brackets can be attributed to the high bond strength and to the low fracture strength of ceramics,[5,6] which can lead to iatrogenic enamel damages, bracket fractures and longer clinical chairtime.[1,2,3,4,5,6]. Several techniques were suggested for debonding of ceramic brackets, such as electrothermal devices,[7] ultrasound,[8] solvents[9] and recently the lasers.[5,10,11,12,13,14,15,16,17] The use of electrothermal devices has been an effective method in debonding ceramic brackets, due to irreversible heating damages to the pulp, this device lost popularity among the clinicians.[7]
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