AIM:To evaluate the effect of the gap width around a restoration on the formation of artificial caries lesion.METHODS:Each of bovine enamel blocks was invested into a metal ring and then was cut longitudinal-ly into 2 equal portions.One portion was inserted into the ring again and the cut surface of the enamel block was ad-hered with a plastic space sheet,with a thickness(μm)of 25,50,100,190 and 270 respectively,followed by inser-tion of a restorative material (Charisma and Fuji Ⅶ respectively)into the residual space of the ring.All restoration specimens were immersed in water for 7 d and then in demineralization solution for 72 h,followed by filling each gap with a light curing sealant resin.Each specimen was cut vertically through the gap to obtain slices of 150 μm thick for the observation under a polarized light microscope and the depths of outer lesion and wall lesion of each specimen were measured using image analysis software.RESULTS:All specimens presented a deeper outer lesion than wall lesion (P<0.05)and Charisma group presented deeper outer lesion than FujiⅦgroup(P<0.05).The depth of wall lesion increased with the increase of the gap width within 100 μm and the Charisma group showed deeper wall lesion than FujiⅦ group(P<0.05 )when the gap width was within 50 ~100 μm.CONCLUSION:The artificial secondary caries model with controlled marginal gap can present obvious out lesion and wall lesion and present the difference of fluoride-releasing materials and non-fluoride-releasing materials in preventing wall lesion.%目的：评价充填物边缘缝隙宽度对人工继发龋形成的影响，确定继发龋模型合适的缝隙宽度。方法：把牛牙釉质块包埋到圆环状模具内，然后对半纵切包埋后的试样，将其中一半重新放入模具内，用充填修复材料（Charisma，FujiⅦ）充填剩余空间，在材料与釉质纵切面间放置缝隙型片（厚度25、50、100、190、270μm），制备釉质与材料间有可控宽度缝隙的修复试样，浸入水中7 d后取出，脱矿72 h后用光固化树脂充填缝隙，垂直于缝隙方向制备150μm厚的切片，在正交偏振光显微镜下测量材料边缘釉质的表面龋损深度和洞壁龋损深度。结果：所有试样的表面龋损深度显著大于洞壁龋损，FujiⅦ组表面龋损深度显著小于Charisma组（P＜0．05）；缝隙宽度＜100μm时，随着宽度的增加，洞壁龋损深度也增加；缝隙宽度在50～100μm，FujiⅦ组的洞壁龋损深度小于Charisma组（P＜0．05）。结论：充填物有缝隙的继发龋模型能形成明显的表面龋损和洞壁龋损，当缝隙宽度在50～100μm时，能够充分展现释氟材料与无释氟材料预防人工继发龋的差异。
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