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Effect of Green Tea Extract Antioxidant on Dentin Shear Bond Strength and Resin-Tag Penetration Depth after Non-vital Bleaching This study aimed to evaluate the effect of 10% and 35% green tea (10% and 35% GT) extract as an antioxidant after 2 minutes of application on dentin shear bond strength and resin tags penetration depth after non-vital bleaching. This research was conducted at the Chemistry Laboratory, Faculty of Medicine, University of Indonesia, and the Dental Materials Research and Development Laboratory, Faculty of Dentistry, University of Indonesia, in March-April 2022. This study was approved by the Ethics Committee (10/Ethical Approval/FKGUI/III/2022; 09/Ethical Exempted/FKGUI/IV/2022) and conducted in accordance with the Declaration of Helsinki. Thirty extracted maxilla premolars for orthodontics reasons, free of caries, fractures, and defects included in this study. The teeth were soaked in a thymol solution (0.1%; pH 7.0) for 1-week post extraction. Then, after 1 week the teeth were placed in 4oC distilled water, and had to be used within 1 month post extraction. The root portion of each tooth was removed 2 mm below the cement-enamel junction with a double-side disc diamond bur (Buehler, Lake Bluff, IL, USA). The coronal portion was sectioned mesiodistally, and the buccal and palatal portions were used, and it is considered as one specimen each portion. The dentin surfaces of specimen were flattened using 600- and 1200-grit sandpaper and polished with felt discs (Arotec, Cotia, SP, Brazil) impregnated with alumina paste (0.5 μm). The specimens were washed ultrasonically in distilled water for 5 minutes to eliminate any residues. For shear bond strength test, the specimens were fixed in a self-cure acrylic 20 mm and for resin tag penetration test the specimens were fix in plasticine 1x1 mm. A mold with a diameter of 2 mm is glued over the specimen in the pulp chamber using plasticine. The specimens were randomly divided into 5 groups (For resin tag penetration test n=6, for shear bond strength test n=5). Group 1: Non-bleached without green tea extract (normal dentin/negative control group), Group 2: Bleached without green tea extract (post bleaching dentin/positive control group), Group 3: Bleached without green tea extract and delay for 2 weeks before being restored (delay 2 weeks). Group 4: Bleached+10% Green tea extract for 2 min (10% GT), Group 5: Bleached+35% Green tea extract for 2 min (35% GT). The shear bond strength assessment was done using a Universal Testing Machine with a 0.5 mm/minute cross-head speed. Confocal Laser Scanning Microscopy (CLSM) with a wavelength of 560 nm and a lens magnification of 40x was used to analyze the resin tag penetration by the fluorescence glow of rhodamine B.绿茶提取物抗氧化剂对无活力牙漂白后牙本质剪切粘结强度及树脂突渗透深度的影响 本研究旨在评估10%与35%绿茶（10% GT、35% GT）提取物作为抗氧化剂，涂布2分钟后，对无活力牙漂白后牙本质剪切粘结强度及树脂突渗透深度的影响。本研究于2022年3—4月在印度尼西亚大学医学院化学实验室及牙科学院牙科材料研究与开发实验室开展。本研究经伦理委员会批准（审批编号：10/Ethical Approval/FKGUI/III/2022；09/Ethical Exempted/FKGUI/IV/2022），并符合《赫尔辛基宣言》相关准则。 本研究纳入30颗因正畸需求拔除的上颌前磨牙，所有样本均无龋坏、折裂及缺损。样本拔除后于0.1%、pH值7.0的麝香草酚溶液中浸泡1周，随后置于4℃蒸馏水中保存，且需在拔除后1个月内完成实验。使用双面金刚石切割盘（Buehler，莱克布拉夫，伊利诺伊州，美国）于釉牙骨质界（cement-enamel junction）下2mm处截除每颗牙齿的牙根部分，将牙冠近远中向切开，取颊侧与腭侧部分作为单份样本。采用600目、1200目砂纸打磨平整样本的牙本质表面，再用浸渍有0.5μm氧化铝抛光膏的毛毡盘（Arotec，科蒂亚，圣保罗州，巴西）进行抛光。随后将样本置于蒸馏水中超声清洗5分钟以去除残留杂质。 剪切粘结强度测试样本需用自凝丙烯酸树脂固定于20mm模具中；树脂突渗透深度测试样本则用橡皮泥（plasticine）固定于1×1mm载体上。使用橡皮泥将直径2mm的模具黏附于样本的髓腔区域。将样本随机分为5组（树脂突渗透测试组n=6，剪切粘结强度测试组n=5）： 1组：未漂白且未使用绿茶提取物（正常牙本质/阴性对照组）； 2组：漂白但未使用绿茶提取物（漂白后牙本质/阳性对照组）； 3组：漂白后未使用绿茶提取物，且于修复前延迟2周（延迟2周组）； 4组：漂白+10%绿茶提取物涂布2分钟（10% GT组）； 5组：漂白+35%绿茶提取物涂布2分钟（35% GT组）。 剪切粘结强度评估采用万能试验机（Universal Testing Machine），以0.5mm/min的十字头速度进行测试。树脂突渗透深度分析采用共聚焦激光扫描显微镜（Confocal Laser Scanning Microscopy, CLSM），设置波长560nm、镜头放大倍数40×，通过罗丹明B的荧光信号观测树脂突渗透情况。