Akhoundi Mohammad Sadegh Ahmad, Etemadi Ardavan, Nasiri Maryam, Borujeni Elahe Soltanmohamadi
Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Orthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
Assistant Professor, Laser Research Center of Dentistry, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Periodontics, Dental Branch, Islamic Azad University, Tehran, Iran.
J Dent (Tehran). 2017 May;14(3):144-152.
Many studies have evaluated re-etched enamel by using scanning electron microscopy (SEM); however, there is no evidence regarding the use of Erbium-doped yttrium aluminium garnet (Er:YAG) laser at primary and secondary bonding instead of acid etching with regards to enamel surface changes. The purpose of the present study was to determine that whether or not the methods of primary and secondary enamel preparation affect enamel characteristics after rebonding, by using SEM analysis.
Twelve freshly extracted premolars were divided into 4 groups. The samples in each group were conditioned by acid etchant or Er:YAG laser at primary conditioning, according to the instructions. Afterwards, they were bonded with orthodontic brackets. After debonding, the samples were prepared for second conditioning. Also, two samples were conditioned only once with acid etchant or laser, to compare enamel morphology changes with those after re-etching. Finally, buccal enamel surfaces were evaluated using SEM.
Enamel etching patterns were observed in the samples which had been acid-conditioned at first or at both conditionings. The samples irradiated by Er:YAG laser showed amorphous and irregular surfaces, with no signs of typical etching patterns. A large deep gap was seen in one of the samples irradiated with laser at primary and secondary conditionings, which might have penetrated the underling layers of enamel and dentin.
Enamel surface preparation with Er:YAG laser produces irregular and indistinct morphologic changes, completely different from those produced after acid etching at both conditioning and reconditioning. Therefore, it is recommended to use this laser with caution to avoid permanent enamel damage.
许多研究已通过扫描电子显微镜（SEM）对再酸蚀的牙釉质进行了评估；然而，关于在初次和二次粘结时使用掺铒钇铝石榴石（Er:YAG）激光替代酸蚀对牙釉质表面变化的影响，尚无相关证据。本研究的目的是通过SEM分析确定初次和二次牙釉质处理方法在重新粘结后是否会影响牙釉质特性。
将12颗新鲜拔除的前磨牙分为4组。根据说明，每组样本在初次处理时用酸蚀剂或Er:YAG激光进行处理。之后，用正畸托槽进行粘结。脱粘结后，对样本进行二次处理准备。另外，有两个样本仅用酸蚀剂或激光处理一次，以将牙釉质形态变化与再酸蚀后的变化进行比较。最后，使用SEM对颊侧牙釉质表面进行评估。
在初次或两次均用酸处理的样本中观察到牙釉质酸蚀模式。用Er:YAG激光照射的样本显示出无定形和不规则的表面，没有典型酸蚀模式的迹象。在初次和二次处理时均用激光照射的一个样本中可见一个大的深间隙，这可能已穿透牙釉质和牙本质的底层。
用Er:YAG激光进行牙釉质表面处理会产生不规则且不清晰的形态学变化，与在初次处理和再处理时酸蚀后产生的变化完全不同。因此，建议谨慎使用这种激光以避免牙釉质永久性损伤。
