The Function and Structure of the Marsupial Enamel

The aims of this study are to clarify the structure of tubular enamel and the function of enamel tubules on the marsupial of opossum (Monodelphis domestica). Almost all enamel prisms, surrounded by interprismatic enamel, ran obliquely from the dentinoenamel junction (DEJ), and bent near the enamel surface. The enamel tubules are distributed in both enamel prisms and the interprismatic enamel near the DEJ. From the middle to the surface of the enamel, one enamel tubule ran within a single enamel prism. Most of enamel tubules continued from the DEJ to near the enamel surface. It is suggested that each enamel tubule developed in relation to one ameloblast. The fibers of odontoblastic process penetrated the DEJ from the dentinal tubules into the enamel tubules, and some branched across the enamel prisms. The odontoblastic process may be actively cross into the ameloblastic layer and may be involved in the formation of enamel tubules. After in vivo injection of tetracycline, tetracycline labeling showed that the odontoblastic tubules continued to enamel tubules. And strontium was detected in enamel tubules from the DEJ to the enamel surface, as was the dentinal tubules. In conclusion, there was active transport by the odontoblast and it's process through the enamel tubules.     

An evaluation of wear of human enamel opposed by ceramics of different surface finishes

Statement of Problem:

Surface of porcelain restoration is a matter of clinical concern because of its abrasive action on the opposing enamel.

Purpose:

This study comparatively evaluated wear of enamel when opposed by three different surface finishes of ceramic.

Materials and Methods:

A total of 60 metal-ceramic discs (10 mm × 2 mm) with different surface finishes were fabricated. They were divided into four groups of autoglazed ceramic surface, over glazed ceramic surface, ceramic surface polished with Shofu polishing kit and ceramic surface polished with DFS polishing wheels and paste. Each group comprised of 15 discs. Sixty human teeth samples were prepared from freshly extracted, unrestored, caries free, nonattrited maxillary first premolars. Each tooth sample was weighed before wear testing using AT200 Mettler Toledo electronic analytical balance of 0.0001 g accuracy. Occlusal surfaces of these teeth were then abraded against the substrates in a wear machine for a total of 10,000 cycles. Each tooth sample was weighed after 5000 cycles and after the total of 10,000 cycles, respectively, using the same balance. Differences in weight of tooth samples before and after wear testing were evaluated statistically using one-way analysis of variance and Bonferroni''s correction for multiple group comparisons.

Results:

The values obtained for percentage weight loss after 10,000 cycles for over glazed ceramic surface were marginally higher than values obtained for autoglazed surface. It was observed that values obtained for percentage weight loss by polished ceramic after 10,000 cycles were statistically less as compared to the values obtained with autoglazed and over glazed ceramic surface (P < 0.001). There was no statistically significant difference between the values obtained by polished ceramic surfaces of two different groups.

Conclusion:

Enamel wear produced by polished porcelain is substantially less than autoglazed and over glazed porcelain. No significant difference was found in enamel wear when opposed by ceramic surfaces polished by two different methods. This study indicates the potential damage porcelain can inflict upon enamel and suggests that porcelain should be polished instead of over glazed.     

人牙釉质酸蚀过程中三维形貌的原子力显微镜观察

目的 比较不同酸蚀时间处理后牙釉质表面的三维形貌并分析粗糙度的改变,探讨酸蚀对牙釉质微观形貌的影响.方法 将15颗新鲜前磨牙包埋、切割、打磨后得到光滑牙釉质切片,按单纯随机法分为5组,用37％磷酸凝胶分别酸蚀0(对照组)、5、10、20和30s,原子力显微镜观察釉质表面形貌,分析轮廓改变,计算图像的算术平均粗糙度(Ra)、均方根粗糙度(Rq)、十点高度平均差(Rz)值及表面积、容积并对5组的结果数据进行单因素方差分析,用Turkey's法进行组间两两比较,以P＜0.05为差异有统计学意义.结果 镜下形貌观察显示,0～20 s内釉质的釉柱结构逐渐明显,釉质表面由较光滑逐渐变为典型鱼鳞状;20 s后表面形态变化不明显.表面轮廓观察显示,随着酸蚀时间由0s增加至30 s,釉柱间隙首先被溶解,酸蚀深度逐渐增加到2.8μm,30 s后釉柱顶部宽度减小至1.8μm,且高度略降低.从0s到30 s,Ra值由(19.69±3.42) nm增加到(359.51±75.79)nm,Rq值由(22.02±5.57) nm增加到(431.02±83.09) nm,Rz值由(0.24±0.08) μm增加到(2.38±0.26) μm;组间比较显示,Ra和Rq值的20s组与30 s组和Rz值的10、20和30 s组差异无统计学意义(P＞0.05),其余各组间差异均有统计学意义(P＜0.05).同时釉质表面积由(406.77±3.88) μm2 (0 s)增大到(546.69±84.02) μm2 (30 s),容积由(65.73±14.46) μm3 (0 s)增大到(474.63±52.50)μm3(30 s).结论 随着酸蚀时间的增加,釉质表面酸蚀深度不断增大,表面粗糙度增加,表面积及容积增大,酸蚀会造成釉质微观形貌的明显改变.     

釉基质蛋白对人牙周膜细胞群骨钙素的影响

目的研究人牙周膜细胞群(human periodontal ligament cell populations,hPDLPs)在釉基质蛋白(em-dogain,EMD)诱导下骨钙素(osteocalcin,OCN)表达的改变。方法组织块法分离培养人牙周膜细胞,实验组用含100 mg/L EMD的培养液诱导6 d,对照组不经EMD诱导培养。免疫细胞化学和实时定量聚合酶链反应(polymer-ase chain reaction,PCR)检测成牙骨质细胞矿化相关蛋白OCN的表达。结果免疫细胞化学结果显示,实验组和对照组hPDLPs细胞胞浆均可见黄色或棕黄色颗粒,OCN表达呈阳性;实验组hPDLPs的OCN检测平均光密度值为0.172 43±0.014 85,对照组为0.167 01±0.017 03,组间差异无统计学意义(t=0.757,P=0.459);实时定量PCR检测结果显示,实验组骨钙素相对表达量是对照组的1.13倍。结论 EMD对hPDLPs的OCN表达无明显影响。     

锌与龋病关系的研究进展

锌作为一种人体必需的金属微量元素,广泛分布于牙菌斑、唾液以及釉质表面,同时,也常被加入口腔清洁类产品中以达到控制菌斑,减少口气,防止牙石形成的目的。尽管有研究显示,锌可以有效地保护牙体硬组织,抑制口腔致龋菌的生长及产酸,在理论上有着良好的抗龋特性,但在实际的临床应用中,锌却没有展现出其在预防及治疗龋病方面的优势。可能是因为锌离子无法大量牢固地粘附于牙体表面,而已附着部分又常会因为各种环境因素的刺激而轻易脱落,从而无法有效发挥防龋效能。本文就锌与牙体硬组织间的相互作用、锌的抗微生物效应及其与龋病发生率的关联等作一综述。     

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目的探讨偏振数码照相结合计算机辅助图像分析法评价邻面去釉后釉质脱矿程度的准确性。方法于2010年3月选取青岛大学医学院附属医院口腔外科门诊因正畸需要拔除的上颌第一前磨牙40颗,沿牙冠颊舌向磨切得到80个标本,随机分为A（空白对照,未进行任何去釉处理）、B（邻面去釉）、C（邻面去釉后使用氟化泡沫）、D（邻面去釉后使用护牙素）4组。体外pH循环60d后,用偏振数码照相结合计算机辅助图像分析法定量测量各组标本邻面去釉及再矿化后的灰度值,以此来评价其釉质脱矿程度。同时用显微硬度仪定量测量各组标本的硬度值作为对照。结果（1）灰度值：A组灰度值最低,B组灰度值最高,C组和D组经过再矿化处理后灰度值较B组降低,差异有统计学意义（P〈0．05）。c组和A、D组之间灰度值差异无统计学意义（P〉0．05）。（2）硬度值：A组硬度值最高,B组硬度值最低,c组和D组经过再矿化处理后硬度值升高,但均较A组低。B组硬度值和其他3组之间比较,差异均有统计学意义（P〈0．05）,而A组与c组、c组与D组之间硬度值比较,差异均无统计学意义（P〉0．05）。结论偏振数码照相结合计算机辅助图像分析法得出的结果与显微硬度仪的定量检测结果相符合,表明了其是一种有效的定量评价釉质脱矿及再矿化效果的方法,值得临床推广。