光动力疗法对大鼠龋齿模型防龋效果及牙髓组织的影响及相关机制研究

Effect of photodynamic therapy on caries prevention and pulp tissue of rat dental caries model.

目的分析光动力疗法(PDT)对大鼠龋齿模型防龋效果及牙髓组织的影响及相关机制。方法通过接种变异链球菌和喂以致龋饲料建立大鼠龋齿模型。将建模成功的40只Wistar大鼠按随机数字表法分为5组,每组8只。0.9%氯化钠溶液组(A组)用浸有0.9%氯化钠溶液的小棉球反复涂搽大鼠磨牙各面5 min;氟化钠组(B组)用浸有2 g/L氟化钠溶液的小棉球反复涂搽大鼠磨牙各面5 min;单纯光敏剂组(C组)用浸有40 mg/L HMME的小棉球放于磨牙各面上,避光孵育5 min,不进行激光照射;单纯激光组(D组)用532 nm半导体激光垂直照射磨牙牙齿各面90 s,功率密度为140 Wm/cm 2,能量密度为12.6 J/cm 2;血卟啉单甲醚-PDT(HMME-PDT)组(E组)用浸有40 mg/L HMME的小棉球放于磨牙各面上,避光孵育5 min,然后用532 nm半导体激光垂直照射磨牙牙齿各面90 s,功率密度和能量密度同D组。5组大鼠每周处理1次,连续处理4周。实验过程中对大鼠的饮食、饮水情况、黏膜溃疡、糜烂,牙龈颜色、形态和质地等进行观察。每次处理后及时收集大鼠口腔变异链球菌进行培养,记录细菌抑制情况。连续处理4周后处死大鼠,记录大鼠磨牙平滑面及窝沟Keyes计分,观察牙齿表面形态及牙髓组织变化。结果5组大鼠的饮食、饮水、活动方式、口腔黏膜、牙龈均良好,无明显差异。处理4周后,与A组相比,B组和E组大鼠口腔中变异链球菌菌落数显著降低,差异均有统计学意义(P<0.05);与B组、C组和D组相比,E组大鼠口腔中变异链球菌菌落数显著降低,差异均有统计学意义(P<0.05)。B组和E组大鼠磨牙平滑面及窝沟E级、Ds级龋损明显低于A组、C组和D组,差异均有统计学意义(P<0.05),且E组Keyes计分最低。扫描电镜显示,5组大鼠磨牙表面龋损区均呈现出不同的脱矿现象,其中A组、C组和D组脱矿较为严重,大鼠牙釉质表面粗糙,明显凹凸不平。B组和E组大鼠磨牙牙釉质表面相对光滑,脱矿区较少。A组、B组和C组大鼠牙髓组织无毛细血管扩张、炎症或出血情况。D组和E组大鼠经激光照射后,牙髓组织出现不同程度毛细血管扩张、充血及炎症细胞浸润情况。与A组相比,D组和E组牙髓组织计分显著升高,差异有统计学意义(P<0.05)。与D组相比,E组大鼠牙髓组织计分显著升高,差异有统计学意义(P<0.05)。结论光动力疗法可通过抑制变异链球菌的增殖,改善牙齿表面结构等达到防龋效果,但其方法易引起大鼠牙髓组织损伤,故需控制光功率和时长。

Objective To analyze the effect of photodynamic therapy on caries prevention and pulp tissue of rat dental caries model.Methods The rat dental caries model was established by inoculating Streptococcus mutans and feeding caries feed.The 40 Wistar rats that were successfully modeled were divided into 5 groups according to the random number table method,with 8 rats in each group.The 0.9%sodium chloride solution group(group A)was repeatedly coated with small cotton balls soaked with 0.9%sodium chloride solution on each surface of the rat molars for 5 min,sodium fluoride group(group B)was repeatedly coated with small cotton balls soaked with 2 g/L sodium fluoride solution on each surface of rat molars for 5 min,photosensitizer group(group C)was repeatedly coated with small cotton balls soaked with 2 g/L sodium fluoride solution on each surface of rat molars for 5 min,laser group(group D)was repeatedly coated with 532 nm semiconductor laser to irradiate each surface of the molars vertically for 90 s,the power density was 140 Wm/cm 2,and the energy density was 12.6 J/cm 2)and hematoporphyrin monomethyl ether PDT(HMME-PDT)group(group E)was repeatedly coated with small cotton balls soaked with 40 mg/L HMME on each surface of the molars,incubated for 5 min in the dark,and then treated with 532 nm semiconductor laser irradiated vertically on each surface of the molars for 90 seconds,the power density and energy density were the same as those in group D).Rats in each group were treated once a week for 4 weeks.During the experiment,the diet,drinking water,mucosal ulcer,erosion,gingival color,morphology and texture were observed.After each treatment,the oral Streptococcus mutans of rats were collected for culture,and the bacterial inhibition was recorded.After 4 weeks of continuous treatment,the rats were killed,and the Keyes scores of the smooth surface and pit groove of the molars were recorded,and the changes of tooth surface morphology and pulp tissue were observed.Results There was no significant difference in diet,drinking water,activity mode,oral mucosa and gingiva of rats in each group.After 4 weeks of treatment,compared with group A,the number of Streptococcus mutans in the oral cavity of group B and group E were significantly decreased,the differences were statistically significant(P<0.05);compared with group B,group C and group D,the number of Streptococcus mutans colonies in group E were significantly decreased,the differences were statistically significant(P<0.05).In group B and group E,the level E and DS caries of molars were significantly lower than those in groups A,C and D,the differences were statistically significant(P<0.05),and the Keyes score of group E was the lowest.The results of scanning electron microscopy showed that there were different demineralization on the surface of molars in each group.The demineralization was more serious in group A,C and D.the enamel surface was rough and uneven obviously.The enamel surface of molars in group B and E was relatively smooth with less demineralization.In group A,group B and group C,there was no capillary dilation,inflammation or bleeding.After laser irradiation,the pulp tissue of rats in group D and E showed different degrees of capillary dilation,hyperemia and inflammatory cell infiltration.Compared with group A,the pulp tissue scores of group D and group E were significantly higher,and the differences were statistically significant(P<0.05).Compared with group D,the pulp tissue scores of rats in group E increased significantly,and the differences were statistically significant(P<0.05).Conclusion Photodynamic therapy can prevent dental caries by inhibiting the proliferation of Streptococcus mutans and improving the surface structure of teeth.However,it is easy to cause dental pulp tissue damage,so it is necessary to control the light power and duration.