Wheeler Cameron R, Fried Daniel, Featherstone John D B, Watanabe Larry G, Le Charles Q
Department of Growth and Development, University of California, San Francisco, California 94143, USA.
Lasers Surg Med. 2003;32(4):310-7. doi: 10.1002/lsm.10162.
Lasers can be used to modify the chemical composition of dental enamel to increase the bond strength to restorative materials and to render the mineral phase more resistant to acid dissolution. Previous studies have suggested a synergistic relationship between CO(2) laser irradiation and fluoride treatment on increased resistance to acid dissolution. In this study a near-UV laser operating with lambda = 355-nm laser pulses of 3-5 nanoseconds duration was used to modify the surface morphology of dental enamel to increase the bond strength to restorative materials and increase the uptake of topical fluoride to render the surface more resistant to acid dissolution. We hypothesize that the short UV laser pulses are primarily absorbed by protein and lipid localized between the enamel prisms resulting in removal of intact mineral effectively etching the surface without thermal modification of the mineral phase. Such modification is likely to increase the permeability of the enamel surface and the subsequent absorption of fluoride. In addition, there is an increase in surface roughness without the formation of a layer of loosely adherent, thermally modified enamel that increases the bond strength to composite restorative materials.
STUDY DESIGN/MATERIALS AND METHODS: The surfaces of blocks of bovine enamel, 5 x 5 mm(2), were uniformly irradiated by 355-nm laser pulses and subsequently bonded to composite. The shear bond test was used to assess the bond strength of non-irradiated blocks (negative control), acid etched blocks (positive control), and laser irradiated blocks. The resistance to acid dissolution was evaluated using controlled surface dissolution experiments on irradiated samples, irradiated samples exposed to topical fluoride, and non-irradiated control samples with and without fluoride.
The laser surface treatments significantly increased the shear-bond strength of enamel to composite, to a level exceeding 20 MPa which was significantly more than the non-irradiated control samples and significantly less than the acid etch. Laser irradiation alone and topical fluoride application alone did not significantly increase the resistance to acid dissolution. The laser treatment followed by topical application of fluoride significantly increased the resistance to acid dissolution to a level of over 50% versus the control samples.
We present a novel method for increasing bond strength to restorative materials and enhancing fluoride delivery to enamel surfaces and shed some light on the underlying mechanisms of caries inhibition via laser treatment and topical application of fluoride.
激光可用于改变牙釉质的化学成分，以提高其与修复材料的粘结强度，并使矿物相更耐酸溶解。先前的研究表明，二氧化碳激光照射与氟化物处理在提高耐酸溶解能力方面存在协同关系。在本研究中，使用波长为355nm、脉宽为3 - 5纳秒的近紫外激光来改变牙釉质的表面形态，以提高其与修复材料的粘结强度，并增加局部氟化物的摄取，使表面更耐酸溶解。我们假设短紫外激光脉冲主要被位于釉柱之间的蛋白质和脂质吸收，从而有效去除完整的矿物质，蚀刻表面而不热改性矿物相。这种改性可能会增加牙釉质表面的渗透性以及随后氟化物的吸收。此外，表面粗糙度增加，且不会形成一层松散附着、热改性的牙釉质层，这增加了与复合修复材料的粘结强度。
研究设计/材料与方法：对尺寸为5×5mm²的牛牙釉质块表面用355nm激光脉冲进行均匀照射，随后与复合材料粘结。采用剪切粘结试验评估未照射块（阴性对照）、酸蚀块（阳性对照）和激光照射块的粘结强度。通过对照射样品、暴露于局部氟化物的照射样品以及有氟和无氟的未照射对照样品进行可控表面溶解实验，评估耐酸溶解能力。
激光表面处理显著提高了牙釉质与复合材料的剪切粘结强度，达到超过20MPa的水平，显著高于未照射对照样品，且显著低于酸蚀处理。单独的激光照射和单独的局部氟化物应用均未显著提高耐酸溶解能力。激光处理后局部应用氟化物显著提高了耐酸溶解能力，与对照样品相比提高了50%以上。
我们提出了一种增加与修复材料粘结强度以及增强氟化物向牙釉质表面输送的新方法，并对通过激光处理和局部应用氟化物抑制龋齿的潜在机制提供了一些见解。
