Effect of diode laser irradiation on the bond strength of polymerized non-simplified adhesive systems after 12 months of water storage

Abstract Objectives: The aim of this in vitro study was to evaluate the bonding strength of non-simplified dentin bonding systems (DBS) to dentin irradiated with a diode laser (970 nm) immediately and after 12 months of water storage following either primer or bond application. Material and methods: The experimental design included three different factors: DBS type [AdperTM Scotchbond Multipurpose (MP) and Clearfil™ SE Bond (CSE)], irradiation [without irradiation - control (C), irradiation after primer application (AP), and irradiation after bond application (AB)], and time [initial (I) and after 12 months of water storage (12 m)]. Sixty sound human third molars (n = 10) were obtained, and their flat occlusal dentin areas were prepared and standardized. Laser irradiation was performed in the contact mode perpendicular to the dental surface over an automatically selected scanning area at a pulse energy of 0.8 W, frequency of 10 Hz, and energy density of 66.67 J/cm2. After 7 days of treatment, the specimens were cut, and half of them were subjected to microtensile testing (500 N/0.05 mm/min), whereas the remaining sticks were examined after 12 months of water storage. The obtained data were analyzed by three-way analysis of variance (ANOVA) followed by a Tukey test (p<0.05). The observed fracture modes were investigated using a portable digital microscope with a magnification of 40x. Results: Among the utilized DBS, MP generally exhibited higher bond strengths, but did not always differ from CSE under similar conditions. The irradiation factor was statistically significant only for the MP/AB groups. After 12 months of storage, all groups demonstrated a significant reduction in the bond strength, whereas the results of fracture analysis showed a predominance of the adhesive type. Conclusions: The laser treatment of non-simplified DBS was not able to stabilize their bonding characteristics after 12 months.

摘要
研究目的：本体外研究旨在评估非简化式牙本质粘接系统（dentin bonding systems, DBS）与经970 nm二极管激光照射的牙本质的粘接强度，分别在底漆或粘接剂涂布后即刻，以及经12个月水储存后进行检测。
材料与方法：实验设计包含三个变量因素：牙本质粘接系统类型[Adper™ Scotchbond多功能粘接剂（MP）与Clearfil™ SE Bond粘接剂（CSE）]、激光照射处理[无照射-对照组（C）、底漆涂布后照射（AP）、粘接剂涂布后照射（AB）]以及时间点[即刻（I）与12个月水储存后（12 m）]。共收集60颗健康人类第三磨牙（每组n=10），制备并标准化其平坦的咬合面牙本质区域。采用接触模式垂直于牙面进行激光照射，自动选定扫描区域，脉冲能量0.8 W，频率10 Hz，能量密度66.67 J/cm²。标本处理7天后被切割，其中一半进行微拉伸测试（加载参数为500 N/0.05 mm/min），剩余微拉伸试条经12个月水储存后再行检测。所得数据采用三因素方差分析（ANOVA）进行统计学分析，随后辅以Tukey检验（p<0.05）。使用放大倍数为40倍的便携式数码显微镜观察并分析断裂模式。
结果：在所使用的两种牙本质粘接系统中，MP通常展现出更高的粘接强度，但在相似实验条件下，其粘接强度与CSE并非始终存在显著差异。激光照射因素仅在MP/AB组中具有统计学显著性。经12个月水储存后，所有组别均表现出粘接强度的显著下降，而断裂分析结果显示粘接界面断裂型占主导地位。
结论：针对非简化式牙本质粘接系统的激光处理，无法使其粘接特性在12个月后保持稳定。