根尖孔大小对牙髓组织再生及牙齿抗压强度的影响

Effect of Apical Foramen Sizes on Dental Pulp Tissue Regeneration and Teeth Compressive Strength

目的:探讨根尖孔大小对牙髓组织再生及牙齿抗压强度的影响。方法:收集因正畸拔除的牙根发育完成、无牙根折裂的单根下前磨牙,离体牙截冠后,保留12mm牙根,随机分为5组,每组25颗牙,根管预备至不同主锉号数,分别为30#、40#、60#、80#及100#主锉组,其中30#主锉组为对照组。体外培养人牙髓干细胞并接种于0.25%水凝胶支架中,将其分别注入不同主锉预备过的根管内,每组均取5颗牙,其牙根于Transwell小室分别培养14、21、28d,提取水凝胶中细胞的总RNA,进行实时定量聚合酶链反应(real-time polymerase chain reaction,Real-time PCR)检测;每组余下的10颗牙,其牙根冠部封闭后植入裸鼠皮下,28d后取出,5颗进行组织学观察,5颗进行静态载荷实验。结果:Real-time PCR检测牙本质涎磷蛋白(dentin sialophosphoprotein,dspp)、牙本质基质蛋白-1(dentin matrix protein-1,dmp-1)的表达,第28天时,各实验组均高于对照组(P<0.05),且40#主锉组高于其它实验组(P<0.05)。组织学分析表明,30#、40#、60#主锉组均未见连续的牙髓样组织形成,80#、100#主锉组可见组织形成,但未表现出典型牙髓样组织结构。静态载荷实验结果表明,40#主锉组的平均抗压载荷与对照组比较差异无统计学意义,其它实验组均低于对照组(P<0.05)。结论:根尖孔预备至100#(1mm)以内时,根尖孔大小对牙髓组织再生没有明显影响,但根尖孔预备大于40#时,抗压强度明显下降。

Objective： To investigate the effect of apical foramen sizes on pulp tissue regeneration and teeth compressive strength. Methods： Single root premolars with complete root development and without tooth root fracture were collected after orthodontic extraction. Twelve millimeter tooth roots were preserved after de-crowned, and randomly divided into 5 groups with 25 teeth in each group. The root canals were prepared to 30#, 40#, 60#, 80#, and 100# main files, respectively, in which 30# main file group was used as the control group. Human dental pulp stem cells were cultured in vitro and inoculated into 0.25% hydrogel scaffolds and then injected into the root canals of different groups. Five teeth were taken from each group and were cultured in Transwell chamber for 14 days, 21 days, and 28 days. Then, the total RNA of the cells was extracted, the expression of DSPP and DMP 1 were detected by real-time PCR. The remaining 10 teeth in each group were implanted subcutaneously into the nude mice. After 28 days, 5 teeth were used for histological examination and 5 samples were used for static load test. Results： After 28 days, the expression of DSPP and DMP1 in the experimental groups were higher than those in the control group （P〈0.05）, and the expression of 40 # main file group was higher than that in the experimental groups （P〈0.05）. Histological analysis showed that there was no continuous pulp like tissue formation in the 30#, 40#, and 60# main file groups. The tissue formation in the 80 # and 100 # main file group could be seen, but no typical pulp like tissue structure was found. The static load test showed that the average compressive load of 40 # main file group was not different from that of the control group, while the other experimental groups were lower than the control group （P〈0.05）. Conclusion： The size of apical foramen has no significant effect on pulp tissue regeneration within size of 100# （1 mm）, but the compressive strength of apical foramen is obviously decreased when the apical foramen is prepared more than 40#.