Improvement of Acid Resistance of Oral Hard Tissue Coated with Ceramic Materials by Using a Carbon Dioxide Laser

PGC对釉质的耐酸性能有极大的改善，氧化硅锆对釉质的耐酸性能有轻微的改善，而NORI对釉质的耐酸性能没有改善。PGC处理后的牙釉质耐酸性能的提高可能是由于激光照射后熔化的PGC对牙釉质表面有很好的润湿作用，因为PGC的成分类似于硬牙组织，即磷酸钙。为了研究新的修复方法和提高牙齿的耐酸能力，采用二氧化碳气体激光在牙釉质表面涂覆几种陶瓷材料。使用的二氧化碳气体激光器为Opelaser/03S (Yoshida Co.)，激光器的照射芯片保持在牙釉质表面20mm的高度。这些陶瓷是磷酸钙玻璃（PGC，旭硝子玻璃公司），金属陶瓷瓷器（NORI， Noritake公司），商用二氧化硅氧化锆。将陶瓷研磨后用400目筛过筛，所得粉体用蒸馏水悬浮至50 mg/ml。采用37%磷酸（K-etchant, Kuratay Co.）处理后的牙釉质表面涂覆陶瓷粉末悬悬液，然后用脉冲CO_2激光照射牙釉质，辐照强度为1.0瓦，辐照时间为30秒，焦点处光束尺寸为0.49 mm。除辐照牙釉质表面直径3mm的圆形外，其余表面均涂指甲油。将涂好的搪瓷样品浸入10 ml 0.1 m醋酸/醋酸钠缓冲液中，pH为4.0，浸泡30分钟。用火焰分析法测定了缓冲液中钙离子的释放量。经氟离子+镧离子处理后的牙釉质具有良好的耐酸性能。因此，先用1%氟化钠水溶液，再用1%氯化镧水溶液对磷酸刻蚀后的牙釉质进行处理，然后用激光照射。然而，辐照后的牙釉质的耐酸性能并没有提高。另一方面，为了改进激光照射的操作，减少激光照射对牙釉质的损伤，研究了宽焦点激光。结果表明，宽焦点激光处理后的牙釉质具有良好的耐酸性能，且对牙釉质无损伤。少

The acid resistance of the enamel treated with PGC was extremely improved, that of the enamel treated with silica-zirconium oxide was slightly improved, and that treated with NORI was not improved. The increase of the acid resistance of the enamel treated with PGC may be due to good wetting of PGC melted by laser irradiation to the enamel surface, as the composition of PGC was analogous to hard tooth tissue that was calcium phosphate.To study new restoration and to improve the acid resistance of teeth, the enamel surface was coated with several ceramic materials by a carbon dioxide gas laser. The carbon dioxide gas laser used was Opelaser/03S (Yoshida Co.), the irradiation chip of the laser was hold at 20 mm high on the enamel surface. Those ceramics were the phosphate calcium glass (PGC, Asahi glass Co.), the porcelain for metal-ceramics (NORI, Noritake Co.), commercial silica-zirconium oxide. The ceramics were grinded followed by sieved with 400 mesh sieve, and the obtained powders w … More ere suspended with distilled water to 50 mg/ml. The ceramic powder suspension were applied on the enamel surface treated with 37% phosphoric acid (K-etchant, Kuratay Co.), and then the enamel was irradiated by a pulsed CO_2 laser at irradiation intensities of 1.0 watt for 30 seconds with a beam size of 0.49 mm at the focal point. And all surface except for the circle of 3 mm diameter on the irradiated enamel surface was painted with nail varnish. The painted enamel sample was immersed in 10 ml of 0.1M-acetic acid/sodium acetate buffer solution at pH 4.0 for 30 minutes. The calcium ions released in the buffer solution from the enamel were measured by flame analysis.It is well known that the enamel treated with fluoride anion followed by lanthanum cation showed good acid resistance. Therefore, the enamel etched with the phosphoric acid was treated with 1% sodium fluoride aqueous solution followed by 1% lanthanum chloride aqueous solution, and then was irradiated by the laser. However, the acid resistance of the irradiated enamel was not improved.On the other hand, to improve the operations of radiation and to reduce the damage of the enamel by laser irradiation, the laser with a wide focal point was studied. It was found that the enamel treated with PGC by using the laser with the wide focal point showed good acid resistance without the damage of the enamel. Less