Correa-Afonso Alessandra M, Pécora Jesus Djalma, Palma-Dibb Regina G
Department of Restorative Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
Photomed Laser Surg. 2008 Jun;26(3):221-5. doi: 10.1089/pho.2007.2120.
The purpose of this study was to assess the efficacy of Er:YAG laser energy for composite resin removal and the influence of pulse repetition rate on the thermal alterations occurring during laser ablation.
Composite resin filling was placed in cavities (1.0 mm deep) prepared in bovine teeth and the specimens were randomly assigned to five groups according to the technique used for composite filling removal. In group I (controls), the restorations were removed using a high-speed diamond bur. In the other groups, the composite fillings were removed using an Er:YAG laser with different pulse repetition rates: group 2-2 Hz; group 3-4 Hz; group 4-6 Hz; and group 5-10 Hz. The time required for complete removal of the restorative material and the temperature changes were recorded.
Temperature rise during composite resin removal with the Er:YAG laser occurred in the substrate underneath the restoration and was directly proportional to the increase in pulse repetition rate. None of the groups had a temperature increase during composite filling removal of more than 5.6 degrees C, which is considered the critical point above which irreversible thermal damage to the pulp may result. Regarding the time for composite filling removal, all the laser-ablated groups (except for group 5 [10 Hz]) required more time than the control group for complete elimination of the material from the cavity walls.
Under the tested conditions, Er:YAG laser irradiation was efficient for composite resin ablation and did not cause a temperature increase above the limit considered safe for the pulp. Among the tested pulse repetition rates, 6 Hz produced minimal temperature change compared to the control group (high-speed bur), and allowed composite filling removal within a time period that is acceptable for clinical conditions.
本研究旨在评估铒钇铝石榴石（Er:YAG）激光能量去除复合树脂的效果以及脉冲重复率对激光消融过程中发生的热变化的影响。
将复合树脂填充物置于牛牙制备的洞形（深1.0毫米）中，根据去除复合树脂填充物所采用的技术，将标本随机分为五组。第一组（对照组）使用高速金刚石车针去除修复体。在其他组中，使用不同脉冲重复率的Er:YAG激光去除复合树脂填充物：第二组-2赫兹；第三组-4赫兹；第四组-6赫兹；第五组-10赫兹。记录完全去除修复材料所需的时间和温度变化。
用Er:YAG激光去除复合树脂时，修复体下方的基质中出现温度升高，且与脉冲重复率的增加成正比。在复合树脂填充物去除过程中，所有组的温度升高均未超过5.6摄氏度，这被认为是可能导致牙髓发生不可逆热损伤的临界点。关于复合树脂填充物的去除时间，所有激光消融组（除第五组[10赫兹]外）从洞壁完全清除材料所需的时间均比对照组长。
在测试条件下，Er:YAG激光照射对复合树脂消融有效，且不会使温度升高至对牙髓而言被认为安全的限度以上。在测试的脉冲重复率中，与对照组（高速车针）相比，6赫兹产生的温度变化最小，并且能在临床条件可接受的时间段内去除复合树脂填充物。
