Faculty of Dentistry, Department of Prosthodontics, University of Gaziantep, Gaziantep, Turkey.
Lasers Med Sci. 2013 Jan;28(1):167-70. doi: 10.1007/s10103-012-1108-1. Epub 2012 May 5.
The neodymium/yttrium-aluminum-garnet (Nd/YAG) laser has been suggested to repair broken prostheses in the mouth. This study investigated the effects of different dentin thicknesses and air cooling on pulpal temperature rise during laser welding. Three intact human maxillary molars were prepared for full-veneer crown. For each tooth, dentin thicknesses in mesiobuccal cusp was 2, 3, or 4 mm. Twenty dies were duplicated from each of the prepared teeth. For metal copings with 0.5-mm thickness, wax patterns were prepared with dip wax technique directly onto each of dies. All patterns were sprued and invested. The castings were made using a nickel-chromium alloy (Nicromed Premium, Neodontics). A hole with 0.5-mm diameter was prepared on the mesiobuccal cusp of each crown. The Nd/YAG laser (9.85 W; 1 Hz repetition rate; fluence, 1.230 J/cm(2); Fidelis Plus 3, Fotona) was used for welding with or without air cooling (n = 10). The temperature rise was measured in pulpal chamber with a J-type thermocouple wire that was connected to a data logger. Differences between start and highest temperature reading were taken, and temperature rise values were compared using two-way analysis of variance and Tukey's honestly significant difference tests (α = .05). Pulpal temperature rise varied significantly depending on the dentin thickness and air cooling (p < 0.05). The non-air cooling group induced significantly the highest temperature increases. There were no significant differences between 2- and 3-mm dentin thicknesses groups (p > 0.05); however, pulpal temperature rise was the lowest for 4-mm dentin thickness group (p < 0.05). The highest values of thermal increase were found in the pulp chamber (6.8°C) when no air cooling was used in 2-mm dentin thickness group. Laser welding on base metal castings with Nd/YAG laser can be applied with air cooling to avoid temperature rises known to adversely affect pulpal health when dentin thickness is 2 or 3 mm.
钕/钇铝石榴石（Nd/YAG）激光已被建议用于修复口腔内的破损修复体。本研究调查了不同牙本质厚度和空气冷却对激光焊接过程中牙髓温升的影响。三个完整的上颌磨牙被制备成全贴面冠。对于每个牙齿，近中颊尖的牙本质厚度为 2、3 或 4 毫米。从每个预备好的牙齿上复制了 20 个模具。对于厚度为 0.5 毫米的金属冠，使用浸蜡技术直接在每个模具上制备蜡型。所有的蜡型都包埋和铸造。铸件采用镍铬合金（Nicromed Premium，Neodontics）制成。在每个牙冠的近中颊尖上制备一个直径为 0.5 毫米的孔。使用 Nd/YAG 激光（9.85 W；1 Hz 重复率；能量密度，1.230 J/cm²；Fidelis Plus 3，Fotona）进行焊接，有或没有空气冷却（n = 10）。使用连接到数据记录器的 J 型热电偶丝测量牙髓腔内的温升。取起始温度和最高温度读数之间的差异，并使用双向方差分析和 Tukey 的诚实显著差异检验（α=0.05）比较温升值。牙髓温升取决于牙本质厚度和空气冷却（p<0.05）。非空气冷却组引起的温升最高。2-和 3 毫米牙本质厚度组之间没有显著差异（p>0.05）；然而，4 毫米牙本质厚度组的牙髓温升最低（p<0.05）。当 2 毫米牙本质厚度组不使用空气冷却时，在牙髓腔内发现最高的热增量值（6.8°C）。当牙本质厚度为 2 或 3 毫米时，Nd/YAG 激光可用于基底金属铸件的激光焊接，并可使用空气冷却以避免已知对牙髓健康不利的温升。
