Spectrophotometric analysis of dental bleaching after bonding and debonding of orthodontic brackets

IntroductionThe aim of this study was to evaluate the bleaching effect after aging simulation in teeth submitted to bonding and debonding of orthodontic brackets.Materials and methodsFor this study, 90 human premolars were selected, and randomly divided into 6 groups: control, bleaching, and other 4 groups submitted to bleaching after bonding and debonding brackets using different methods. Color measurement of sample through the CIE L*a*b* system was performed in three moments: T1 – after brackets debonding, T2 – after staining cycling, and T3 – after bleaching. For evaluation of results among the components L*, a* and b*, the two criteria analysis of variance and the multiple comparison Tukey test (p < 0.05) were used.ResultsStatistically significant difference was observed among the groups submitted to brackets bonding and debonding through self-conditioning adhesive system and tungsten drill, also the control and bleaching groups between the moments T1 e T2.ConclusionBonding and debonding brackets methods tested in this study showed influence on the sample color change, and after the tooth bleaching process, only the group without brackets previous bonding achieved the color value presented before the staining and aging of samples in the brackets absence.     

Calbindin D28k‐like immunoreactivity during the formation of the enamel‐free area in the rat molar teeth

Previous studies have demonstrated the presence of calbindin D28k in the ameloblasts derived from the inner enamel epithelium. The occlusal surfaces of the rodent molars partly lack the enamel covering, which is referred to as enamel‐free area (EFA). In the present study, we compared the immunohistochemical localization of calbindin D28k‐like immunoreactivity (CB‐LI) in the cells at the EFA (EFA cells) and ameloblasts of the rat molar teeth at the light microscopic level. CB‐LI was strong in the ameloblasts of the presecretory through the protective stages, while it was faint at the late secretory to transitional stages. However, some mature ameloblasts lacked the immunoreactivity. On the other hand, the majority of EFA cells showed distinct polarization and elongation that were absent in few cells at the early stage of EFA formation. At all stages, the EFA cells adjacent to the ameloblasts showed CB‐LI, however, some cells adjacent to the mature ameloblasts lacked the reaction. Intensive CB‐LI was demonstrated in EFA cells at the reduced enamel epithelium. These immunohistochemical findings suggest EFA cells have cytochemical properties similar to those of ameloblasts. Anat Rec 258:384–390, 2000. © 2000 Wiley‐Liss, Inc.     

两种釉质粘接剂粘接效果比较及粘接操作中的护理配合

目的探讨3M自凝釉质粘接剂与京津釉质粘接剂的临床操作及粘接效果的异同。方法挑选12～14岁正畸患者40例,男19例,女21例,按就诊先后顺序随机分成两组:3M组和京津组,在同一护士配合下由同一位医师完成所有患者上半口托槽的粘接,分别记录各患者的粘接时间及1个月后的托槽脱落情况并进行统计学分析。结果3M组临床操作时间为(10.42±1.24)min,明显短于京津组的(12.05±0.89)min,统计学分析有显著性差异;但两组的托槽脱落率分别为3.8%和3.4%,差异无统计学意义。结论在充分注意牙面清洁和隔湿、获得患者和家长配合的前提下,3M自凝釉质粘接剂与京津釉质粘接剂的短期粘接效果无明显差异。良好的护理配合是获得良好粘接效果的关键因素之一。     

正畸治疗后脱矿牙釉质的纵向激光测定

目的应用龋齿诊断仪DIAGNOdent,对正畸治疗后牙釉质早期龋损的纵向量化测定,为牙釉质脱矿的早期预防提供有效指导。方法筛选30例表现牙釉质脱矿的正畸治疗后患者,分别在拆除矫治器后1h,2周,1、3、6、9个月,应用DIAGNOdent仪器对白垩斑部位进行监测。比较各期白垩斑部位面积变化和DIAGN-Odent读数变化。结果9个月观察期内白垩斑仍可发现。轻度釉质表面脱矿2周内无明显变化,1个月时脱矿区的面积有所减小,DIAGNOdent读数减小,3个月后再矿化进程较为缓慢,DIAGNOdent读数趋于稳定。牙釉质脱矿严重者观察期内未见明显再矿化,甚至部分脱矿加重,DIAGNOdent读数增大。结论DIAGNOdent仪器能有效监测临床脱矿牙釉质的再矿化,有助于指导和评价正畸患者牙釉质脱矿的防治措施。     

The Measurement of Contact Angle,pH, and Conductivity of Artificial Saliva and Mouthwashes on Enamel,Glass-Ionomer,and Composite Dental Materials

The aim of this study was to tackle the topic of appropriate recommendations for artificial-saliva and mouthwash usage. The contact angle, pH, and conductivity of two artificial saliva solutions, four mouthwashes, and their mixtures on enamel, glass-ionomer, and composite dental materials were measured. The measurements were conducted with a MATLAB algorithm to minimize human error. The obtained values for the contact angle were in the range from 7.98° to 52.6°, and they showed completely nonlinear and nonuniform behavior for all investigated liquids and on all investigated substrates. Results reveal statistically significant differences among all tested liquids on all investigated substrates (p < 0.05). pH values ranged from 1.54 to 7.01. A wide range of conductivity values were observed, from 1205µS/cm in the saliva-stimulating solution to 6679 mS/cm in the artificial saliva. Spearman’s test showed a moderate positive correlation between the pH and conductivity of the tested fluids (R = 0.7108). A comparison of the data obtained using Image J software and the MATLAB algorithm showed consistency, not exceeding 5% error. When an experiment uses human material and bioactive materials THAT are used in biomedicine as substrates, an additional definition of protocols is highly recommended for future research on this topic.     

Interactions of regenerative, inflammatory and biomechanical signals on bone morphogenetic protein-2 in periodontal ligament cells

Nokhbehsaim M, Deschner B, Winter J, Bourauel C, Rath B, Jäger A, Jepsen S, Deschner J. Interactions of regenerative, inflammatory and biomechanical signals on bone morphogenetic protein‐2 in periodontal ligament cells. J Periodont Res 2011; 46: 374–381.© 2011 John Wiley & Sons A/S Background and Objective: Regeneration of periodontal tissues by EMD remains a major challenge because a number of modifying factors are as yet unknown. The effects of EMD seem to be mediated, at least in part, by bone morphogenetic protein‐2 (BMP‐2). This in vitro study was performed to examine whether the effects of EMD on BMP‐2 activity are modulated by inflammatory and/or biomechanical signals. Material and Methods: Periodontal ligament cells were seeded on BioFlex^® plates and exposed to EMD under normal, inflammatory or biomechanical loading conditions for 1 and 6 d. In order to mimic proinflammatory or biomechanical loading conditions in vitro, cells were stimulated with interleukin‐1β (IL‐1β), which is increased at inflamed periodontal sites, and cyclic tensile strain of various magnitudes, respectively. The synthesis of BMP‐2, its receptors (BMPR‐1A, BMPR‐1B and BMPR‐2) and its inhibitors (follistatin, matrix gla protein and noggin) were analyzed using real‐time RT‐PCR and ELISA. Results: In EMD‐treated cells, BMP‐2 synthesis was increased significantly at 1 d. EMD also induced the expression of all BMP receptors, and of the BMP inhibitors follistatin and noggin. In general, IL‐1β and biomechanical loading neither down‐regulated BMP‐2 nor up‐regulated BMP inhibitors in EMD‐stimulated cells. However, IL‐1β and biomechanical loading, when applied for a longer time period, caused a down‐regulation of EMD‐induced BMP receptors. Conclusion: EMD induces not only BMP‐2, but also its receptors and inhibitors, in PDL cells. IL‐1β and biomechanical forces may counteract the beneficial effects of EMD on BMP‐2 activity via the down‐regulation of BMP receptors.     

冷光美白对人恒牙表层釉质的影响

目的探讨冷光美白对人恒牙表层釉质晶体和显微结构的影响。方法人离体恒牙经冷光美白处理后,使用微区X线衍射仪、傅里叶转换红外光谱仪和扫描电镜观察,分析美白前后表层釉质在晶体和显微结构上发生的改变。结果经冷光美白处理后,人恒牙表层釉质晶体尺寸变小,结晶度降低,表面孔隙变得不规则,并出现浅碟状凹坑。结论冷光美白技术可能导致人恒牙表层釉质晶体和显微结构发生类似于脱矿的改变。     

用牙釉电子自旋共振方法估算慢性辐射损伤人员的受照剂量

目的 用于牙釉电子自旋共振对慢性辐射损伤人员的受照剂量进行估算的方法。方法 用电子自旋共振仪测定慢性辐射损伤人员牙釉电子自旋共振信号强度，用剂量－效应曲线法和附加剂量法来重建辐射损伤人员的受照剂量，探讨牙釉电子自旋共振法估算受照剂量的可行性；并比较了不同能量的射线（1.25MeV的γ射线和6MeV的X射线）对牙釉电子自旋共振信号强度的影响。结果 用两种方法估算的辐射损伤人员受照剂量基本一致；对能量1.25MeV的γ射线和6MeV的X射线进行比较，无论从剂量－效应曲线的直线系数，还是用混合照射后的剂量估算，两者差别不大。结论 慢性辐射损伤人员的受照剂量可以用于牙釉电子自旋共振方法进行估算，射线能量在1.25MeV-6MeV范围内对牙釉电子自旋共振信号强度影响不大。     

选择性釉质酸蚀结合自酸蚀粘结对釉质粘接剪切强度的影响

目的 评估选择性釉质酸蚀结合自酸蚀粘接、全酸蚀和自酸蚀粘接3种不同粘结系统对釉质粘接树脂的剪切强度影响.方法 在30颗无龋坏离体人磨牙分别制备60个牙釉质粘接界面试件,随机分为3组,每组10颗牙,第1组用35％磷酸预处理牙釉质结合可乐丽菲露SEbond粘接;第2组用35％磷酸和3M Singlebond2粘接;第3组用可乐丽菲露SEbond粘接.各试件在37℃生理盐水进行浸泡24 h,分别进行牙釉质抗剪切强度的测试.结果 3组剪切强度两两比较,P＜0.05,有统计学意义;第1组粘接强度明显好于第3组(P＜0.05),提示磷酸预酸蚀釉质处理后再联合使用自酸蚀粘接系统可大大提高粘接强度.结论 选择性釉质酸蚀结合自酸蚀可以显著提高树脂与牙釉质的粘接强度.