Staninec Michal, Darling Cynthia L, Goodis Harold E, Pierre Daniel, Cox Darren P, Fan Kenneth, Larson Michael, Parisi Renaldo, Hsu Dennis, Manesh Saman K, Ho Chi, Hosseini Mehran, Fried Daniel
Department of Preventive and Restorative Dental Sciences, UCSF School of Dentistry, 707 Parnassus Ave, San Francisco, California 94143-0758, USA.
Lasers Surg Med. 2009 Apr;41(4):256-63. doi: 10.1002/lsm.20748.
In vitro studies have shown that CO2 lasers operating at the highly absorbed 9.3 and 9.6-microm wavelengths with a pulse duration in the range of 10-20-microsecond are well suited for the efficient ablation of enamel and dentin with minimal peripheral thermal damage. Even though these CO2 lasers are highly promising, they have yet to receive FDA approval. Clinical studies are necessary to determine if excessive heat deposition in the tooth may have any detrimental pulpal effects, particularly at higher ablative fluencies. The purpose of this study was to evaluate the pulpal safety of laser irradiation of tooth occlusal surfaces under the conditions required for small conservative preparations confined to enamel.
STUDY DESIGN/MATERIALS AND METHODS: Test subjects requiring removal of third molar teeth were recruited and teeth scheduled for extraction were irradiated using a pulsed CO2 laser at a wavelength of 9.3 microm operating at 25 or 50 Hz using a incident fluence of 20 J/cm(2) for a total of 3,000 laser pulses (36 J) for both rates with water cooling. Two control groups were used, one with no treatment and one with a small cut made with a conventional high-speed hand-piece. No anesthetic was used for any of the procedures and tooth vitality was evaluated prior to treatment by heat, cold and electrical testing. Short term effects were observed on teeth extracted within 72 hours after treatment and long term effects were observed on teeth extracted 90 days after treatment. The pulps of the teeth were fixed with formalin immediately after extraction and subjected to histological examination. Additionally, micro-thermocouple measurements were used to estimate the potential temperature rise in the pulp chamber of extracted teeth employing the same irradiation conditions used in vivo.
Pulpal thermocouple measurements showed the internal temperature rise in the tooth was within safe limits, 3.3+/-1.4 degrees C without water cooling versus 1.7+/-1.6 degrees C with water-cooling, n = 25, P<0.05. None of the control or treatment groups showed any deleterious effects on pulpal tissues and none of the 29 test-subjects felt pain or discomfort after the procedure. Only two test-subjects felt discomfort from "cold sensitivity" during the procedure caused by the water-spray.
It appears that this CO2 laser can ablate enamel safely without harming the pulp under the rate of energy deposition employed in this study.
体外研究表明，工作在高吸收的9.3和9.6微米波长、脉冲持续时间在10 - 20微秒范围内的二氧化碳激光非常适合高效消融牙釉质和牙本质，且周边热损伤最小。尽管这些二氧化碳激光前景广阔，但尚未获得美国食品药品监督管理局（FDA）的批准。有必要进行临床研究以确定牙齿中过多的热量沉积是否会对牙髓产生任何有害影响，特别是在较高的消融能量密度下。本研究的目的是评估在仅限于牙釉质的小型保守性制备所需条件下，激光照射牙齿咬合面的牙髓安全性。
研究设计/材料与方法：招募需要拔除第三磨牙的受试者，对于计划拔除的牙齿，使用波长为9.3微米的脉冲二氧化碳激光，以25或50赫兹的频率运行，入射能量密度为20 J/cm²，两种频率均进行总共3000次激光脉冲（36 J）照射，并采用水冷。使用两个对照组，一组不进行处理，另一组用传统高速手机进行小切口。所有操作均未使用麻醉剂，在治疗前通过热、冷和电测试评估牙齿活力。在治疗后72小时内拔除的牙齿上观察短期效应，在治疗后90天拔除的牙齿上观察长期效应。牙齿拔除后立即用福尔马林固定牙髓并进行组织学检查。此外，使用微型热电偶测量来估计在与体内相同照射条件下拔除牙齿的牙髓腔内的潜在温度升高。
牙髓热电偶测量显示，牙齿内部温度升高在安全范围内，无水冷时为3.3±1.4℃，有水冷时为1.7±1.6℃，n = 25，P<0.05。对照组或治疗组均未对牙髓组织显示出任何有害影响，29名受试对象在操作后均未感到疼痛或不适。只有两名受试对象在操作过程中因喷水而感到“冷敏感”不适。
在本研究采用的能量沉积速率下，这种二氧化碳激光似乎可以安全地消融牙釉质而不损害牙髓。
