University of California, San Francisco, San Francisco, California 94143-0758, USA.
J Biomed Opt. 2011 Jul;16(7):071410. doi: 10.1117/1.3603996.
CO(2) lasers can be operated at high laser pulse repetition rates for the rapid and precise removal of dental decay. Excessive heat accumulation and peripheral thermal damage is a concern when using high pulse repetition rates. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. The interpulpal temperature rise was recorded using microthermocouples situated at the roof of the pulp chamber on teeth that were occlusally ablated using a rapidly-scanned CO(2) laser operating at 9.3 μm with a pulse duration of 10 to 15 μs and repetition rate of 300 Hz over a 2 min time course. The adhesion strength of laser treated enamel and dentin surfaces was measured for various laser scanning parameters with and without post-ablation acid etching using the single-plane shear test. The mechanical strength of laser-ablated dentin surfaces were determined via the four-point bend test and compared to control samples prepared with 320 grit wet sand paper to simulate conventional preparations. Thermocouple measurements indicated that the temperature remained below ambient temperature if water-cooling was used. There was no discoloration of either dentin or enamel laser treated surfaces, the surfaces were uniformly ablated, and there were no cracks visible. Four-point bend tests yielded mean mechanical strengths of 18.2 N (s.d. = 4.6) for ablated dentin and 18.1 N (s.d. = 2.7) for control (p > 0.05). Shear tests yielded mean bond strengths approaching 30 MPa for both enamel and dentin under certain irradiation conditions. These values were slightly lower than nonirradiated acid-etched control samples. Additional studies are needed to determine if the slightly lower bond strength than the acid-etched control samples is clinically significant. These measurements demonstrate that enamel and dentin surfaces can be rapidly ablated by CO(2) lasers with minimal peripheral thermal and mechanical damage and without excessive heat accumulation.
二氧化碳（CO2）激光可以以高激光脉冲重复率运行，从而快速准确地去除牙体龋坏。当使用高脉冲重复率时，会出现过度的热量积累和周围热损伤的问题。周围热损伤会对被照射组织的机械强度产生不利影响，尤其是牙本质，并且会降低改性表面的黏附特性。通过在牙髓腔顶部放置微型热电偶来记录牙髓腔内的温度升高，这些牙齿使用以 9.3μm 波长、10-15μs 脉冲持续时间和 300Hz 脉冲重复率运行的快速扫描 CO2 激光进行牙合面消融，2 分钟内完成。使用单平面剪切试验，针对不同的激光扫描参数以及有无消融后酸蚀处理，测量激光处理牙釉质和牙本质表面的黏附强度。通过四点弯曲试验确定激光消融牙本质表面的机械强度，并与使用 320 目水砂纸制备的对照样本进行比较，以模拟常规制备。热电偶测量结果表明，如果使用水冷，则温度保持在环境温度以下。激光处理后的牙本质或牙釉质表面没有变色，表面均匀消融，没有可见的裂缝。四点弯曲试验的平均机械强度为 18.2N（s.d. = 4.6），用于消融牙本质，对照样本（p > 0.05）为 18.1N（s.d. = 2.7）。在某些辐照条件下，剪切试验得到的牙釉质和牙本质的平均结合强度接近 30MPa。这些值略低于未经辐照酸蚀的对照样本。需要进一步的研究来确定略低于酸蚀对照样本的结合强度是否具有临床意义。这些测量结果表明，牙釉质和牙本质表面可以通过 CO2 激光快速消融，周围热损伤和机械损伤最小，并且不会出现过度的热量积累。
