Corona Silmara Aparecida Milori, Souza-Gabriel Aline Evangelista, Chinelatti Michelle Alexandra, Pécora Jesus Djalma, Borsatto Maria Cristina, Palma-Dibb Regina Guenka
Department of Restorative Dentistry, Ribeirão Preto School of Dentistry, University of São Paulo (USP), Av. do Café, S/N Monte Alegre, Ribeirão Preto, CEP 14040-904, São Paulo, Brazil.
J Biomed Mater Res A. 2008 Mar 1;84(3):569-75. doi: 10.1002/jbm.a.31335.
To assess the influence of energy and pulse repetition rate of Er:YAG laser on the enamel ablation ability and substrate morphology.
Fifteen crowns of molars were sectioned in four fragments, providing 60 samples, which were ground to flatten the enamel surface. The initial mass was obtained by weighing the fragments. The specimens were hydrated for 1 h, fixed, and a 3-mm-diameter area was delimited. Twelve groups were randomly formed according to the combination of laser energies (200, 250, 300, or 350 mJ) and pulse repetition rates (2, 3, or 4 Hz). The final mass was obtained and mass loss was calculated by the difference between the initial and final mass. The specimens were prepared for SEM. Data were submitted to ANOVA and Scheffé test.
The 4 Hz frequency resulted in higher mass loss and was statistically different from 2 and 3 Hz (p < 0.05). The increase of frequency produced more melted areas, cracks, and unselective and deeper ablation. The 350 mJ energy promoted greater mass loss, similar to 300 mJ.
The pulse repetition rate influenced more intensively the mass loss and morphological alteration. Among the tested parameters, 350 mJ/3 Hz improved the ability of enamel ablation with less surface morphological alterations.
评估铒钇铝石榴石（Er:YAG）激光的能量和脉冲重复率对牙釉质消融能力及基底形态的影响。
将15颗磨牙牙冠切成四个碎片，得到60个样本，将其研磨以使牙釉质表面平整。通过称量碎片获得初始质量。将样本水化1小时，固定后，划定一个直径3毫米的区域。根据激光能量（200、250、300或350毫焦）和脉冲重复率（2、3或4赫兹）的组合随机形成12组。获得最终质量，并通过初始质量与最终质量之差计算质量损失。对样本进行扫描电子显微镜（SEM）制备。数据进行方差分析和谢费检验。
4赫兹频率导致更高的质量损失，且与2赫兹和3赫兹在统计学上有差异（p < 0.05）。频率增加产生更多的熔化区域、裂纹以及非选择性和更深的消融。350毫焦能量促进了更大的质量损失，与300毫焦相似。
脉冲重复率对质量损失和形态改变的影响更为强烈。在测试参数中，350毫焦/3赫兹提高了牙釉质消融能力，且表面形态改变较小。
