新型无磨料牙膏对聚甲基丙烯酸甲酯树脂表面性能影响的研究

 目的　研制新型无磨料牙膏，并评估其对聚甲基丙烯酸甲酯（polymethyl methacrylat，PMMA）树脂表面性能的影响。方法　在新型牙膏中去除磨料并调整表面活性剂和湿润剂的比例，对10种新型牙膏的性状进行评估；选择较佳性状的2种新型牙膏（新型牙膏A组和新型牙膏B组）与市面牙膏（市面牙膏A组和市面牙膏B组）、市面泡腾片（市面泡腾片组）及蒸馏水（对照组）对PMMA树脂片进行清洁处理，比较各组清洁前后PMMA树脂片表面光密度（OD）值及粗糙度（Ra）值，评估各类清洁剂对PMMA树脂表面清洁效果及磨损水平。结果　10种新型牙膏中2号（新型牙膏A组）和6号（新型牙膏B组）具有较佳的性状，其pH值分别为7.18和7.22，并用于后续研究。（1）清洁效果：对照组清洁处理前后PMMA树脂片菌斑红染及OD值基本无明显变化，差异无统计学意义（P > 0.05），其余各组清洁处理后的PMMA树脂片菌斑红染程度较清洁处理前明显降低，OD值也显著下降，差异有统计学意义（均P < 0.05），尤其以市面泡腾片组、新型牙膏A组和新型牙膏B组清洁效果最为显著。（2）磨损水平：体视显微镜观察发现，清洁处理后，对照组PMMA树脂片表面光滑无划痕；市面牙膏A组和市面牙膏B组PMMA树脂片表面划痕较深且划痕数量较多，Ra值也明显增大，差异均有统计学意义（均P < 0.05）；市面泡腾片组、新型牙膏A组和新型牙膏B组PMMA树脂片表面仅出现轻微细小浅划痕，Ra值略微升高，但其差异均无统计学意义（均P > 0.05）。结论　新型无磨料牙膏在有效清除菌斑软垢的同时可减少PMMA树脂表面划痕，可成为临床义齿清洁牙膏。

The study of apical root resorption following extraction therapy in adults and adolescents before and after orthodontic treatment

The study of apical root resorption following extraction therapy in adults and adolescents before and after orthodontic treatment. GUO Xin-xing*，CHEN Jing，ZHANG Yong.* Department of Orthodontics，Jinan Stomatological Hospital，Jinan 250001，ChinaAbstract： Objective To study the relationship between tooth movement and apical root resorption，and examine the relationship between root resorption and aging factors. Methods Thirty-four ClassⅠadolescent patients and thirty-six ClassⅠadult patients in middle mandibular angle were selected in Jinan Stomatological Hospital from July of 2004 to September of 2007; each patient was treated with straight wire mechanics and extracted the first premolar.The amount of apical root resorption of the central incisors and other items were measured for each patient by cephalograms Analysis &; Database Winceph 8.0.Then the results were analyzed with Student's t-test. Result The apical root resorption happened in the lower central incisor of adolescents and the upper central incisor of the adults. There was a mean of 0.92 ± 1.19 mm of apical root shortening in adolescent patients， but in adult subjects the mean root resorption was 2.55 ± 1.60 mm. Conclusion The apical root resorption is prone to happen in the lower central incisor of adolescents and the upper central incisor of adults.Significant correlations are found between the amount of apical root resorption and tooth inclination， or the movement distance of the apical root.