Hoteit Marwan, Nammour Samir, Zeinoun Toni
Lebanese University, Faculty of Dental Medicine, Department of Orthodontics, Hadath, Lebanon.
University of Liege, Faculty of Medicine, Department of Dental Science, 4020 Liege, Belgium.
Int Orthod. 2019 Dec;17(4):744-757. doi: 10.1016/j.ortho.2019.08.019. Epub 2019 Sep 19.
Enamel microcrack formation has a high incidence after mechanical debonding of ceramic brackets. This may be due to high delivered shear bond strength values when enamel is priorly etched by phosphoric acid. It is still not well elucidated in the literature if laser etching affects enamel the same way. The aim of the research was to analyze different Er,Cr:YSGG and Er:YAG laser etching settings as an alternative to phosphoric acid, in an attempt to prevent enamel microcrack formation during laser etching and mechanical debonding, while reducing the shear bond strength to the minimal clinical acceptable value.
One hundred and thirty-three teeth were randomly divided into 7 experimental groups according to their etching modalities. Settings used for enamel etching were in Er,Cr:YSGG groups: Er,Cr:YSGG (1.5Watt, W/20Hertz, Hz); Er,Cr:YSGG (1.5W/15Hz) and Er,Cr:YSGG (2W/20Hz) and settings used for enamel etching in Er:YAG groups were: Er:YAG (60 millijoules, mJ), Er:YAG (80mJ) and Er:YAG (100mJ). Group C etched with 37% phosphoric acid served as control. Microscopic analysis was performed to assess presence of enamel microcracks. Shear bond strength was evaluated after thermocycling using Weibull survival analysis.
All groups showed a reduction in additional microcracks after debonding when compared to control, but only group Er:YAG (60mJ) exhibited a statistically significant difference. Groups Er:YAG (80mJ), control and Er:YAG (100mJ) showed respectively the highest probability of survival at various stress levels followed by groups Er:YAG (60mJ); Er,Cr:YSGG (1.5W/15Hz); Er,Cr:YSGG (2W/20Hz) and Er,Cr:YSGG (1.5W/20Hz) that presented a relatively considerable risk of failure, even at low stress levels.
When considering reduction of enamel microcrack formation and clinical acceptable shear bond strength, none of the groups succeeded both. Etching by Er:YAG (60mJ) and Er,Cr:YSGG (1.5W/15Hz), showed the least overall microcrack incidence between groups, but Er:YAG (60mJ) displayed significant reduction compared to phosphoric acid. However, etching by Er:YAG (80mJ) had the most predictable results in term of shear bond strength.
陶瓷托槽机械脱粘后牙釉质微裂纹形成的发生率很高。这可能是由于在用磷酸预先蚀刻牙釉质时传递的剪切粘结强度值较高。激光蚀刻对牙釉质的影响是否与磷酸相同，在文献中仍未得到很好的阐明。该研究的目的是分析不同的铒铬：钇钪镓石榴石（Er,Cr:YSGG）和铒：钇铝石榴石（Er:YAG）激光蚀刻参数作为磷酸的替代方法，试图在激光蚀刻和机械脱粘过程中防止牙釉质微裂纹形成，同时将剪切粘结强度降低到临床可接受的最小值。
133颗牙齿根据蚀刻方式随机分为7个实验组。用于牙釉质蚀刻的参数在Er,Cr:YSGG组中为：Er,Cr:YSGG（1.5瓦，W/20赫兹，Hz）；Er,Cr:YSGG（1.5W/15Hz）和Er,Cr:YSGG（2W/20Hz），用于Er:YAG组牙釉质蚀刻的参数为：Er:YAG（60毫焦，mJ）、Er:YAG（80mJ）和Er:YAG（100mJ）。用37%磷酸蚀刻的C组作为对照组。进行显微镜分析以评估牙釉质微裂纹的存在。热循环后使用威布尔生存分析评估剪切粘结强度。
与对照组相比，所有组在脱粘后额外微裂纹均减少，但只有Er:YAG（60mJ）组表现出统计学上的显著差异。Er:YAG（80mJ）组、对照组和Er:YAG（100mJ）组在不同应力水平下分别显示出最高的生存概率，其次是Er:YAG（60mJ）组；Er,Cr:YSGG（1.5W/15Hz）组；Er,Cr:YSGG（2W/20Hz）组和Er,Cr:YSGG（1.5W/20Hz）组，即使在低应力水平下也存在相对较大的失败风险。
在考虑减少牙釉质微裂纹形成和临床可接受的剪切粘结强度时，没有一组能同时实现这两个目标。Er:YAG（60mJ）和Er,Cr:YSGG（1.5W/15Hz）蚀刻在各实验组中总体微裂纹发生率最低，但与磷酸相比，Er:YAG（60mJ）显示出显著降低。然而，就剪切粘结强度而言，Er:YAG（80mJ）蚀刻的结果最可预测。
