電解水對表層牙本質物性的影響

研究目的: 電解水在牙科臨床不僅可應用於印模材、假牙基底、器械、治療椅管線等方面的消毒，也可應用於根管沖洗液或漱口水之用途。有研究指出，酸性電解水對琺瑯質會產生表面溶解現象，但對牙本質的影響性如何至今仍未知。本研究對牙本質經電解水浸泡後的硬度、元素成分及粗糙度進行測量，並觀察表面形態的變化，以便了解電解水對牙本質物性的影響。材料與方法: 採取人的大臼齒64顆，隨機將之分為四組，分別為強酸性電解水組(strong acidic electrolyzed water，簡稱AW)、中性電解水組(neutral electrolyzed water，簡稱NW)、5%次氯酸鈉水溶液組(5%NaOCl，簡稱NL)、去離子水組(deionized water，簡稱DW)。將牙齒以切割機擷取牙冠部表層牙本質，然後將此牙齒樣本以縱切方式切為兩半，一半用於觀察牙本質表面(牙本質表面試片)，另一半用於觀察牙本質縱面(牙本質側面試片，測量表層下25μm及50μm部位)。牙本質表面試片除了表面部分以外，其餘部分以樹脂包埋。牙本質側面試片則是在牙本質表面及縱切部分的側面部分呈現露出，其餘部分以樹脂包埋，但於側面部分塗上保護膠覆蓋之。將牙齒試片分別置入AW、NW、NL、DW四種溶液中，每隔5分鐘測試其表面及側面的微硬度，測定至浸泡時間計60分鐘為止。並在浸泡各組溶液5分鐘及60分鐘後，使用X光能量散射光譜分析表面組成元素、掃描式電子顯微鏡觀察表面形態變化和進行表面粗糙度測試。統計採用重複測量檢定方式(MANOVA)及ANOVA分析四種溶液對牙本質微硬度的影響，以ANOVA分析四種溶液對牙本質鈣磷比及粗糙度的影響。結果: AW組顯示牙本質有明顯的粗糙度增大與硬度減少及塗抹層消失，在15分鐘後軟化達25μm深度，而且鈣磷比明顯下跌。NW組的粗糙度與硬度無明顯變化以及部分塗抹層消失。NL組與NW組的結果相似。DW組的粗糙度與硬度變化最少，仍呈現塗抹層的存在。AW組受到浸泡時間增長，其鈣及磷顯著減少，造成鈣磷比呈現明顯下降，而其餘三組的鈣磷比沒有受到浸泡時間影響。結論: 在短時間的浸泡下，強酸性電解水會對牙本質造成軟化的現象，隨著時間增長，牙本質礦化程度、硬度、粗糙度都會逐步受到影響。在長時間的浸泡下，中性電解水與5%NaOCl水溶液會使牙本質硬度緩慢的降低，在本實驗時間設計內，對牙本質的礦化程度、硬度、粗糙度和對照組無顯著差異。由本實驗結果得知，pH值不同的電解水對牙本質的物性分別具有不同的影響力，使用時應考慮其特性慎重選用。

關鍵字

牙本質；電解水；維克氏微硬度； X光能量散射光譜分析；掃描式電子顯微鏡；表面粗糙度

並列摘要

Objective: Electrolyzed water has been used in the clinical dentistry for disinfectant of impression material, denture bases, instruments and dental unit water lines. It has been reported that surface erosion phenomenon on the enamel occurs when exposing to acidic electrolyzed water. However, it is still unknown whether this phenomenon occurs on the dentin. The purpose of this study was to evaluate the effect of electrolyzed water on the microhardness, surface morphology, elemental components and roughness of the superficial dentin of teeth crown. Maerial and methods: 64 human molar teeth were divided into 4 groups: (1) AW group: immersed in strong acidic electrolyzed water; (2) NW group: immersed in neutral electrolyzed water; (3) NL group: immersed in 5%NaOCl solution and (4) DW group: immersed in deionized water. Specimens of the superficial dentin were sectioned horizontally with a low speed diamond disc. The specimens were further sectioned longitudinally and then divided into two subgroups: group1a were used for observing the microhardness of the superficial surface of dentin; group 1b were used for observing the microhardness of the longitudinal surface of the dentin (25μm and 50μm beneath the surfaces of the specimens). Group 1a were embedded in acrylic resin exposing the superficial surfaces of the dentin. Group 1b were embedded in acrylic resin exposing the superficial and longitudinal surfaces of the dentin. The longitudinal surfaces of group 1b were covered with protective varnish. The specimens were immersed into four solutions: AW, NW, NL, or DW, respectively and were tested with the Vicker’s microharness machine every five-minute immersion. The total testing time is 60 minutes. Scanning electronic micrograph observation, surface roughness and elemental analysis performed by EDX were also performed after immersed in each solution for 5 and 60 minutes. The results were then statistically analyzed by repeated measurement statistical methods (MONAVA), ANOVA and Tukey’s HSD test. Result: In AW group, the smear layer was effectively removed with increasing roughness and markedly decreasing microhardness. After immersing for 15 minutes, the softening of the dentin approached 25μm depth. In NW group, the smear layer was partially removed with no significantly change at roughness and microhardness. In NL group, the smear layer was partially removed but the cleaning degree was less than NW group. The roughness and microhardness were not changed significantly. In DW group, the smear layer was not removed, and the change of roughness and microhardness were the least among the four groups. Overall, except AW group, the microhardness, roughness and elemental components were not significantly changed among NW, NL and DW groups after immersing for 60 minutes. Conclusion: After immersing in the strong acidic electrolyzed water for a short time, the microhardness of the superficial dentin decreased. As time went by, the microhardness, roughness and elemental components were changed. After immersing in the neutral electrolyzed water or 5%NaOCl solution for a period of time, the microhardness of the superficial dentin decreased gradually. In the observation period of this study, the microhardness, roughness and elemental components of the superficial dentin were not significantly different than the control group. According to the results, the effects of strong acidic or neutral electrolyzed water on physical properties of the superficial dentin were quite different. The application of different type electrolyzed water in dental clinic should be used carefully.