Objectives: This study aimed to remove occlusal veneers of varied thicknesses and compositions by Er:Yag laser in vitro and analyze the interfacial microstructure between veneers and tooth that irradiated by laser, by which experimental evidence could be provided to support the non-invasive removal of occlusal veneerby laser.
Methods: Fresh mandibular premolars extracted for orthodontic requirements were collected for tooth preparation. Three kinds of ceramic materials (Vita Suprinity, Vita Mark Ⅱ, and Upcera Hyramic) were selected to fabricate occlusal veneer with different thicknesses (1.0, 1.5, and 2.0 mm). One week later, Er:Yag laser (2.5 W and 3.5 W) was used to irradiate and remove the occlusal veneer and recorded the timespan. After the removal operation, the micro-morphologies of samples were examined by scanning electron microscope.
Results: Upcera Hyramic veneer failed to be removed (>20 min); the operation span at 2.5 W, Vita Suprinity (96.0 s±16.0 s) was longer than Vita MarkⅡ(84.5 s±19.5 s) in the 1.0 mm group (P<0.05), and Vita Suprinity (246.5 s±13.5 s) was longer than Vita MarkⅡ(170.0 s±14.0 s) in the 1.5 mm group (P<0.05). At 3.5 W, Vita Suprinity (381.0 s±24.0 s) was longer than Vita MarkⅡ(341.5 s±26.5 s) in the 2.0 mm group.
Conclusions: Increasing laser power could shorten the operation span and facilitate the removal of occlusal veneers with the same thickness and composition. The occlusal veneer was sustained when insufficient laser power was applied. With the same laser power and ceramic thickness, laser penetration could interfere with the integral of the ceramic structure when the laser interacted with the bonding layer. With the same ceramic composition and laser power, the operation span and laser power increased with the thickness of the occlusal veneer. However, the laser was incapable of removing occlusal resin veneer directly.
目的: 本实验采用Er: Yag激光对不同厚度、不同材质牙合贴面进行体外照射去粘接，通过分析比较Er:Yag激光对于牙合贴面、牙体组织微观结构的影响，为激光无创拆除牙合贴面提供理论依据。方法: 选取新鲜拔除正畸下颌前磨牙，标准化牙体预备后制作3种不同厚度（1.0、1.5、2.0 mm）和不同材质（Vita琥珀瓷、Vita MarkⅡ、润瓷）牙合贴面进行粘接，1周后使用Er: Yag激光（2.5、3.5 W）照射牙合贴面并记录时间。扫描电镜（SEM）观察去除后的微观形态。结果: 润瓷牙合贴面经2.5或3.5 W Er: Yag激光长时间（>20 min）照射后仍无法取下；2.5 W Er: Yag激光去除粘接时间：1.0 mm Vita琥珀瓷组（96.0 s±16.0 s）大于1.0 mm Vita MarkⅡ组（84.5 s±19.5 s）（P<0.05）；1.5 mm Vita琥珀瓷组（246.5 s±13.5 s）大于1.5 mm Vita MarkⅡ组（170.0 s±14.0 s）（P<0.05）；3.5 W Er: Yag激光去除粘接时间：2.0 mm Vita琥珀瓷组（381.0 s±24.0 s）大于2.0 mm Vita MarkⅡ组（341.5 s±26.5 s）。结论: 同种材质、相同厚度情况下：激光功率越大，拆除时间越短，当功率较小时，可能导致牙合贴面无法拆除。相同厚度、相同功率情况下：激光穿透瓷块到达粘接层可能对瓷块结构产生影响。同种材料、相同功率情况下：瓷块厚度越厚，拆除所需时间越长，所需功率越高。激光无法直接拆除树脂类牙合贴面。.
Keywords: Er: Yag laser; debonding; glass ceramics; occlusal veneer; resin-based ceramics; scanning electron microscope.