Caries prevention and Restoration by Ceramics Coating on Enamel Surface Using a CO_2 Laser

为研究新的修复体，提高牙齿的抗酸性，用二氧化碳气体激光器在牙釉质表面涂上几种陶瓷材料。将陶瓷粉末悬浮液施加到用37%磷酸（K-蚀刻剂，Kuraray Co.）处理的釉质表面上，然后用脉冲CO_2激光（Opelaser/03 S，Yoshida Co.）照射强度为1.0瓦，在焦点处的光束尺寸为0.49mm，持续30秒。除照射后牙釉质表面直径为3 mm的圆外，其余表面均涂指甲油。将涂漆的釉质样品浸入10 ml pH 4.0的0.1M-乙酸/乙酸钠缓冲溶液中30分钟。火焰分析法测定牙釉质在缓冲液中释放的钙离子，磷酸钙玻璃（PGC）处理的牙釉质的耐酸性有极大提高，二氧化硅-氧化锆处理的牙釉质的耐酸性略有提高，金属陶瓷瓷处理的牙釉质的耐酸性没有提高。用PGC处理的牙釉质的抗酸性增加可能是由于激光照射熔化的PGC对牙釉质表面的良好润湿，因为PGC的组成类似于硬牙齿组织，即磷酸钙。因此，用1%氟化钠水溶液处理用磷酸蚀刻的釉质，然后用1%氯化镧水溶液处理，然后用激光照射。然而，辐照牙釉质的耐酸性没有得到改善。

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 ceramic powder suspension were applied on the enamel surface treated with 37% phosphoric acid (K-etchant, Kuraray Co.), and then the enamel was irradiated by a pulsed CO_2 laser (Opelaser/03S, Yoshida Co.) at irradiation intensities of 1.0 watt for 30 seconds with a beam size of 0.49mm at the focal point. And all surface except for the circle of 3mm 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.The acid resistance of the enamel treated with the phosphate calcium glass (PGC) was extremely improved, that of the enamel treated with silica-zirconium oxide was slightly improved, and that treated with the porcelain for metal-ceramics 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.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.