Obeidi Ali, McCracken Michael S, Liu Perng-Ru, Litaker Mark S, Beck Preston, Rahemtulla Firoz
Department of Restorative Dentistry and Biomaterials, The University of Texas, Dental Branch at Houston, Houston, TX 77030, USA.
Lasers Surg Med. 2009 Aug;41(6):454-62. doi: 10.1002/lsm.20790.
Erbium lasers are potential tools to remove caries and dental hard tissue but bond strengths of composites to those preparations are reported to be lower than conventional methods. The purpose of this study was to evaluate the effect of mechanical excavation and/or chemical alteration on bond strength of composites to laser irradiated enamel and dentin.
Seventy-two premolars were ground to obtain flat enamel (E, n = 36) or dentin (D, n = 36) surfaces in both buccal and lingual cusps, divided into: LaserExcavation (LEx), LaserNo-excavation (LNex), and Bur (B) groups. The laser groups were irradiated for 10 seconds by Er,Cr:YSGG laser [4.5 W, 60% air, 80% water (enamel) 3 W, 60% air, 70% water (dentin)]. Irradiated surfaces in the excavation groups (Ex) were then mechanically smoothed with a dental excavator, prepared surfaces were then etched (37% H(3)PO(4)) for 20 or 40 seconds (enamel) and 15 or 30 seconds (dentin), washed (20 seconds), adhesive was applied(Single Bond Plus), and light cured (20 seconds). A composite cylinder (Filtek Supreme Plus) formed, placed and light cured (40 seconds). The specimens were stored (37 degrees C,48 hours), shear bond tested (1 mm/minute), and statistically analyzed (P < 0.05).
Mixed-model ANOVA showed significant differences between enamel (P = 0.0091) and between dentin groups (P = 0.0035). Tukey/Kramer showed mean shear bond strength (SBS+/-SE) of EB40 (27.01+/-2.38 MPa) was significantly higher than ELNoExc20 (14.39+/-2.5 MPa) and ELExc40 (14.90+/-2.28 MPa). Also DB30 (17.57+/- 1.67 MPa) and DLExc30 (18.6+/-1.74 MPa) were significantly higher than DLNoExc15 (9.56+/-1.86 MPa).
Increasing the etching time up to 40 seconds or excavation of the laser prepared surface (but not the combination) may increase the bond strength to the level of conventional methods in enamel but excavation has a greater influence in dentin. Also the combination of both methods [excavation+longer etching time (30 seconds)] exhibit significantly better results in dentin.Mode of failure study showed mechanical excavation in both enamel and dentin can significantly reduce the cohesive failure in tooth structure.
铒激光是去除龋齿和牙体硬组织的潜在工具，但据报道，复合材料与这些预备体的粘结强度低于传统方法。本研究的目的是评估机械挖掘和/或化学改变对复合材料与激光照射的釉质和牙本质粘结强度的影响。
72颗前磨牙被磨平以在颊尖和舌尖获得平坦的釉质（E，n = 36）或牙本质（D，n = 36）表面，分为：激光挖掘（LEx）、激光未挖掘（LNex）和车针（B）组。激光组用Er,Cr:YSGG激光照射10秒[4.5W，60%空气，80%水（釉质）；3W，60%空气，70%水（牙本质）]。然后用牙用挖匙对挖掘组（Ex）的照射表面进行机械打磨，预备表面接着用（37%H₃PO₄）蚀刻20或40秒（釉质）以及15或30秒（牙本质），冲洗（20秒），施加粘结剂（Single Bond Plus），并光固化（20秒）。形成一个复合圆柱体（Filtek Supreme Plus），放置并光固化（40秒）。将标本储存（37℃，48小时），进行剪切粘结测试（1毫米/分钟），并进行统计学分析（P < 0.05）。
混合模型方差分析显示釉质组之间（P = 0.0091）和牙本质组之间（P = 0.0035）存在显著差异。Tukey/Kramer检验显示EB40（27.01±2.38MPa）的平均剪切粘结强度（SBS±SE）显著高于ELNoExc20（14.39±2.5MPa）和ELExc40（14.90±2.28MPa）。同样，DB30（17.57±1.67MPa）和DLExc30（18.6±1.74MPa）显著高于DLNoExc15（9.56±1.86MPa）。
将蚀刻时间延长至40秒或对激光预备表面进行挖掘（但不是两者结合）可能会使釉质中的粘结强度提高到传统方法的水平，但挖掘对牙本质的影响更大。此外，两种方法的结合[挖掘+更长的蚀刻时间（30秒）]在牙本质中表现出明显更好的结果。失效模式研究表明，在釉质和牙本质中进行机械挖掘均可显著降低牙体结构中的内聚性失效。
