Heravi Farzin, Bayani Shahin
Department of Orthodontics and the Dental Research Center, School of Dentistry, Mashad, Iran.
Aust Orthod J. 2009 Nov;25(2):153-7.
Selection of the appropriate curing time and light direction may enable the appropriate shear bond strength to be obtained and avoid enamel fracture during debonding.
To determine the effects of different curing times and light directions on the shear bond strengths of ceramic and stainless steel brackets.
Ninety-two recently extracted, upper premolars were randomly assigned to six groups. Either stainless steel or ceramic brackets were bonded to the buccal surfaces of the teeth. Group I, stainless steel brackets cured for 40 seconds from buccal surface; Group II, stainless steel brackets cured for 40 seconds from palatal surface; Group III, stainless steel brackets cured for 80 seconds from palatal surface; Group IV, ceramic brackets cured for 40 seconds from the buccal surface; Group V, ceramic brackets cured for 40 seconds from the palatal surface; Group VI, ceramic brackets cured for 80 seconds from the palatal surface. The shear bond strength was measured with a universal testing machine and the resin remaining after debonding scored with the Adhesive Remnant Index (ARI). The data were analysed with the oneway ANOVA, Tukey's HSD test and the Kruskal-Wallis test. Associations between the ARI and shear bond strength were determined with Pearson's correlation coefficient.
Group IV (ceramic brackets cured for 40 seconds from buccal surface) had the highest shear bond strength (21.26 MPa) and Group II (metal brackets cured for 40 seconds from palatal surface) had the lowest shear bond strength (6.95 MPa).There was no significant difference in ARI scores among the groups. The association between the ARI scores and bond strength values was not statistically significant.
Curing from the buccal surface for 40 seconds gave unacceptably high shear bond strength values for both stainless steel and ceramic brackets. Lower shear bond strengths occurred when the light was directed from the palatal surface, but a shorter curing time is more likely to be preferred by clinicians. Future studies should investigate the possibility of reducing the curing time for both brackets.
选择合适的固化时间和光照方向可以获得合适的剪切粘结强度，并避免在脱粘过程中牙釉质断裂。
确定不同固化时间和光照方向对陶瓷和不锈钢托槽剪切粘结强度的影响。
将92颗近期拔除的上颌前磨牙随机分为六组。将不锈钢或陶瓷托槽粘结到牙齿的颊面。第一组，不锈钢托槽从颊面固化40秒；第二组，不锈钢托槽从腭面固化40秒；第三组，不锈钢托槽从腭面固化80秒；第四组，陶瓷托槽从颊面固化40秒；第五组，陶瓷托槽从腭面固化40秒；第六组，陶瓷托槽从腭面固化80秒。用万能试验机测量剪切粘结强度，并用粘结剂残留指数（ARI）对脱粘后残留的树脂进行评分。数据采用单因素方差分析、Tukey's HSD检验和Kruskal-Wallis检验进行分析。用Pearson相关系数确定ARI与剪切粘结强度之间的关联。
第四组（陶瓷托槽从颊面固化40秒）的剪切粘结强度最高（21.26MPa），第二组（金属托槽从腭面固化40秒）的剪切粘结强度最低（6.95MPa）。各组间ARI评分无显著差异。ARI评分与粘结强度值之间的关联无统计学意义。
对于不锈钢和陶瓷托槽，从颊面固化40秒会产生过高的剪切粘结强度值，这是不可接受的。当光照从腭面照射时，剪切粘结强度较低，但较短的固化时间可能更受临床医生青睐。未来的研究应探讨缩短两种托槽固化时间的可能性。
