- 學位論文
二極體雷射在穿透牙本質後對於轉醣鏈球菌之殺菌效果
Bactericidal effects of Diode Laser on Streptococcus mutans after Irradiation through Dentin
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摘要
牙髓壞死 (pulp necrosis) 以及根尖組織發炎 (apical periodontitis)是臨床上常見的牙齒的疾病，雖然傳統的治療上，利用根管清創、使用沖洗液及根管內用藥來移除根管內的細菌具有某程度上之效果，但是由於根管系統的複雜性、細菌對牙本質小管的侵入，加上各種物理性或化學性的方法、抗生素的使用都有其限制，因此要使根管達到無菌狀態並不容易。轉醣鏈球菌 (Streptococcus mutans) 為口腔常見導致齲齒以及感染根管內之兼性厭氧細菌，二極體雷射 (diode laser) 於牙科亦曾應用於牙周囊袋及根管內之清創消毒，在傳統方式不可及之處，輕便且具高效能的雷射可能具有臨床輔助之效。因此本實驗欲使用二極體雷射來偵測其對牙本質內轉醣鏈球菌之影響。我們利用波長為 810 nm 的二極體雷射，透過定量厚度之牙本質對細菌進行移動式的照射，利用序列稀釋 (serial dilution) 及表面塗佈法 (surface spreading technique) 測定細菌存活量，並以掃瞄式電子顯微鏡 (SEM) 觀察菌體及牙本質的變化。研究結果顯示：(1) 在低於7.0W的各功率照射作用下，牙本質表面可見到牙本質屑以及部分牙本質小管開口阻塞，這種情形隨著能量提高而增加，但無裂痕或熔融情形產生，只有在功率9.0W的組別可見到坑洞和碳化的現象。 (2) 細菌的存活量方面，在牙本質厚度為500μm的組別，雷射功率0.5W至7.0W的殺菌效果介於19-97 %之間，5.0W時超過90%，7.0W時幾乎完全殺菌。 (3) 當牙本質厚度增加到1000μm及2000μm，以7.0W之功率照射時，殺菌效果分別為50% 與 20%，約為在500μm時的二分之一及五分之一，隨著牙本質厚度增加殺菌的效果隨之下降。(4) 電子顯微鏡下之細菌觀察，功率提高時，牙本質表面所見之完整菌體數減少，菌體也呈現分裂異常以及變形破裂之情形，形態的改變程度跟存活的菌數是互相關連的。由實驗的結果可知二極體雷射的能量傳導經過厚度500μm之牙本質後仍有殺菌能力，此時雷射的殺菌能力隨著能量提高而增加，當雷射功率在5.0W時對於侵入牙本質內的轉醣鏈球菌有明顯的殺菌效果，且對牙本質表面未造成傷害。因此此能量下之二極體雷射可具有輔助治療之效，但仍需要進一步的臨床研究。
並列摘要
Pulp necrosis and subsequent periradicular periodontitis are the common diseases in dentistry. It has been well established that bacteria play a definite role in the development of the diseases. Although canal shaping with irrigation and intracanal medication are used to eliminate the infection, the complexity of three dimensional canal system and the bacterial invasion of dentinal tubules are often out of approach. As chemical irrigants, mechanical debridement and antibiotics all have limitations, it is not easy to expect a thorough decontamination. Streptococcus mutans is a dominant facultative anaerobic bacterium, which causes the dental caries and is also present with other microorganisms within the infected root canal. Diode laser irradiation has been used in dentistry for disinfection of periodontal pocket and root canals for several years. Laser irradiation with high efficiency and portability may have auxiliary role to clinical treatments. The aim of this study was to evaluate the influence of the 810 nm diode laser on Streptococcus mutans in the dentinal tubules. Sterile dentin samples of standardized thickness (500, 1000, 2000 microns) were inoculated with Streptococcus mutans. They were irradiated on the bacterial -free side in a contact mode under constant scanning movement (30sec, continuous mode) by a diode laser (LaserSmileTM, BIOLASE®, California). The survival rate of bacteria was determined by serial dilution and colony counting on agar plate (surface spreading technique). In the same manner, some samples were subjected to SEM by which morphology of irradiated dentin surfaces and bacteria being investigated. The results indicated that：(1) On the lased side of dentin surface below the power setting of 7.0 watts, there was no crack or meltage, whereas some dentinal debris and obliteration of dentinal tubules were noted. It was only in the 9.0- watt groups that the crater and carbonization occurred. (2) The mean bacterial reductions, in the groups of 500-micron dentin thickness, occurred after application of laser at 0.5 watts to 7.0 watts, which led to 17% to 98% (0.1 to 1.9 log steps) of bacteria killed. As the power set was beyond 5.0 watts, more than 90% of bacteria were eliminated. The dentin was almost sterilized when the power of 7.0 watts was applied. (3) In the groups of 1000 microns- and 2000 microns-thick slices, 50% and 20% bacterial reductions were achieved under laser of 7.0 watts, respectively, which were one-half and one-fifth of those of 500 microns-thick slices. It is clear that the bactericidal effect decreased when the dentin thickness increased. (4) The SEM investigation revealed the decrease in integrated and normal bacterial colonies as well as damaged morphologic appearances and variant divisional patterns of bacteria when the power was increased. The morphologic changes were related to the vitality of the bacteria. In conclusions, the diode laser irradiation can significantly reduce the number of bacteria without damaging dentin, even after its energy transmission through 500 microns- thick dentin. It can be potentially used for additional cleaning of the root canal system as an adjunct following biochemical instrumentation, and further clinical investigation is needed.
參考文獻
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