General hospital residency for dental undergraduates

A one-week full-time general hospital residency for a final year of 81 dental undergraduates has been greeted by the majority of students as being an invaluable experience. Such a residency programme could be structured to provide dental students with an even broader medical perspective during their training and thus allow for a greater clinical maturity on graduation. The present programme is outlined and discussed.     

An ectopic maxillary second molar

A bstract — A rarely encountered ectopic and dilacerate maxillary second molar is described. The tooth was found to be attached to the medial wall of the maxillary sinus. Its location is thought to be due to ankylosis consequent to injury sustained during infancy.     

Progesterone metabolism by rat oral mucosa II. The effect of pregnancy

In order to examine the effect of pregnancy on the gingiva, the metabolism of progesterone in pregnant and non-pregnant rats was studied. Homogenates and mitochondrial, microsomal, and soluble fractions were obtained with differential centrifugation. The subcellular preparations were supplemented with NADPH and incubated with ¹⁴C-progesterone for 30 min at pH 7.4 and 37°C. The metabolites were identified by column and multiple thin-layer chromatography and radioautography and quantified with liquid scintillation counting. The metabolism was significantly reduced in homogenate, mitochondrial, and microsomal incubations of oral mucosae of pregnant rats when compared to those of non-pregnant ones. The decrease of the metabolism in the soluble fraction incubations was not statistically significant. In all subcellular preparations the activities of 20et-and 20 β -hydroxysteroid dehydrogenases, if present, remained rather constant, but the activities of steroid hydrogenases and 3α- and 3 β -hydroxysteroid dehydrogenases decreased markedly. The value of these findings as a contributing factor in pregnancy gingivitis is discussed.     

The rationale for the indication and design off the MOD inlay

Modern preventive measures enable an occlusion based approach in the design of an MOD inlay. Treatment planning should require control of the caries problem and institution of sound oral hygiene before any permanent cast restoration is provided. Because of stress developing from occlusal forces being translated into a wedge action fracture of the crown weakened by cavity preparation is enhanced. When inlay restorations are indicated preference should be given to partial coverage of the crown.     

羟基磷灰石涂层热处理晶化工艺研究

目的：通过热处理方法提高羟基磷灰石（HA）涂层的结晶度、使脱落的羟基得到恢复。方法：通过等离子喷涂和热处理试验，利用X射线衍射（XRD）和红外吸收光普分析等手段研究了热处理对羟基磷石涂层相组成的影响。结果：热处理可使涂层中的非晶相发生晶化，并使羟基得到恢复；随着热处理温度的提高，涂层的结晶度提高，α－TCP等热分解相逐步转变为羟基磷灰石。保温时间达到2小时后，延长保温时间并不能提高涂层的结晶工。结论：在大气环境下，涂层的最佳热处理工艺是在700℃下保温2小时。     

CDIC柱状种植体周龈下菌群变化的2年观察

目的：了解种植体周龈下菌群构成变化与种植体周围组织炎的关系，方法：观察64枚CDIC种植体植入术后2年内种植体周龈下细菌构成变化以及相关临床指标。结果：种植体植入术后1月、3月、6月的龈下球菌比值降低。螺旋体，梭形菌比值增高，杆菌，弯曲菌比值差异无显著性意义。术后12月，24月这五类菌的比值接近术前水平，临床菌斑指数，龈沟出血指数高者，种植体周龈下细菌中球菌的比值较低，梭形菌，螺旋体的比值较高。结论：早期进行口腔卫生指导和定期细菌学检测，对提高种植义齿成功很有必要。     

玻璃离子水门汀与银汞粘接的剪切力测试

探讨了玻璃离子水门汀增强银汞充填体与牙体之间的粘结作用。取新鲜离体人磨牙制成3mm厚的牙块,在其中央制备直径3mm的圆柱形洞,分别以玻璃离子、银汞粘结剂涂于洞壁,再充填银汞合金,另设空白对照组。两周后测各组的剪切力并作统计学分析。结果表明:玻璃离子与银汞粘结剂组的剪切力比空白对照组大,并有显著差异;说明玻璃离子与银汞粘结剂均有相似的增强银汞修复体与牙体之间粘结力的作用。