Solution Ca/P ratio affects calcium phosphate crystal phases

Summary Previous studies on brushite formation and dissolution concluded that brushite was stable only in acidic solutions with pH<6.5. Francis in 1965 predicted that, at pH range 3.5–6.5, brushite would be the preferred phase at low solution Ca/P ratio and hydroxyapatite at high Ca/P ratio. This work presents room-temperature experimental evidence that solution Ca/P ratio affects calcium phosphate crystal phases and that brushite can be the preferred phase in certain supersaturated aqueous solutions containing Ca⁺⁺ and Pi, with or without Mg⁺⁺, even at pH 7.0. Solution mixtures were prepared containing initial [CaCl₂]=0.1−10.0 mM, [Na₂HPO₄]=0.1−100.0 mM, [MgCl₂]=0 or 3 mM. By addition of NaCl, the ionic strengths in terms of osmolarity were also varied from 100 to 800 mosM. Precipitates were isolated from solutions on the 7th, 14th and 21st days and identified by x-ray diffraction. Results indicated that in the presence of 3 mM Mg⁺⁺ and relatively high initial apparent activity products (Ca⁺⁺)(Pi), brushite, whitlockite and hydroxyapatite were obtained as transformation products of initially formed amorphous calcium phosphate when solution Ca/P ratios had low, medium and high values, respectively. In the absence of Mg⁺⁺, whitlockite was not found. However, with or without Mg⁺⁺, when (Ca⁺⁺)(Pi) was relatively low, only brushite was formed by direct crystallization. We concluded that although solutions were mixed at 23°C, pH 7.0, the results were useful in explaining the in vivo calcium phosphate crystal phases observed in renal and dental calculi.     

Fluoride and dental caries: two different statistical approaches to the same data source

A recent analysis of data from earlier papers on the relationship between dental caries and drinking water fluoride concentration suggested that the commonly accepted inverse relationship did not exist. Our reanalysis of those data, however, confirms the well-known association between fluoride concentration and dental caries. It also shows that the contrary result arose misleadingly from three simultaneous methodological errors: use of a unifactorial instead of a multifactorial model; omission of or over-aggregation of some data, and analysis of homoscedastic probits instead of heteroscedastic counts.     

口腔修复材料表面粗糙度与血链球菌早期粘附的关系

口腔修复材料表面粗糙度影响微生物粘附的问题，因长期缺乏令人信服的客观实验依据，一直未能受到应有的重视。此研究采用表面轮廓仪量化测定了口腔义齿修复材料（湿热固化基托塑胶及ＣｏＣｒ合金）的表面粗糙度，通过将不同粗糙度级的试件与口腔血链球菌在体外厌氧孵育２４小时后，测定细菌粘附量，并用扫描电镜观察试件表面形态及细菌粘附情况。结果显示血链球菌的２４小时粘附量与修复材料表面粗糙度呈正相关关系，相关系数分别为ｒ塑胶＝０４６（Ｐ＜００１），ｒ合金＝０２５（Ｐ＜００１）。从而提示临床修复体的打磨抛光应尽可能获得光滑表面，以期能在最大程度上减小其表面的菌斑积聚量，达到保护其周围口腔组织健康并延长修复体使用寿命的目的     

Ophthalmologic Procedures in the Emergency Department— Part II: Routine Evaluation Procedures

The emergency physician (EP) must be familiar with performance of ophthalmologic procedures for evaluation and treatment of a multitude of eye complaints. This article is the second of three articles addressing ophthalmologic procedures potentially of use by the EP. This article reviews the indications and the techniques for the following routine procedures: visual acuity testing, pupil dilatation, topical anesthesia use, and tonometry. Criteria for consultation also are addressed.     

产科急症子宫切除手术指征分析

目的：探讨产科急症子宫切除术的发生率、手术指征、高危因素和并发症。方法：采用回顾性资料分析方法，对1987年6月到2003年12月间产科子宫切除术22例患者的临床资料进行分析。结果：22例均为经各种方法保守治疗无效的产科大出血患者，16年间住院分娩7008人，22例行急诊产科子宫切除术，发生率3．139％，其中胎盘粘连7例，胎盘早剥5例，前置胎盘3例，子宫收缩乏力5例，子宫破裂2例。结论：胎盘因素是产科急诊子宫切除术的主要指征，子宫次全切除术是治疗产科急性子宫出血，抢救产妇生命的一项重要措施和手段．     

口腔治疗师培养规划的初步研究

目的进行口腔治疗师医学技术岗位和教育现状分析,提出我国口腔治疗师培养的初步规划。方法通过现有资料收集和现场调查,了解口腔技术职业教育的现状和发展趋势。采用专家咨询法讨论口腔治疗技术专业的培养目标与方向。结果在基本口腔治疗技术专业方面,以高职教育为主要培养途径,培养高级应用型口腔治疗师,以培养通科口腔治疗师为主。教学内容应以实践技能为主,通过专业课程评价的学生可以获得口腔治疗师资历,同时对课程设置、教学模式和专业师资配备提出初步规划。结论与高等职业教育的目标相适应,口腔医学高职教育应致力于培养应用能力强的口腔治疗师。口腔治疗师标准从人文素质、理论知识、专业技能和其他相关能力四个方面对学生提出要求,通过准入标准的具有口腔治疗师资历的人可以在国内登记注册,作为口腔治疗师开业。     

An in vitro study of the role of dentine in moderating the cytotoxicity of zinc oxide eugenol cement

The protective role of different dentine fractions and of dentine slices in moderating the cytotoxicity of zinc oxide eugenol (ZOE) was investigated. The collagen fraction of dentine powder provided increased protection over intact powder. Slices of dentine offered greater protection probably by providing a physical barrier to the diffusion of eugenol which may also bind to the contents of the dentine tubules. With increasing thickness of the dentine slices this protection was increased. ZOE stimulated calcium release from dentine but in view of the low levels attained it is unlikely that this process has any significant effect on the protective role of dentine.     

种植义齿在外胚叶发育异常患者牙列重建中的应用

目的 探讨种植义齿在外胚叶发育异常（ectodermal dysplasia，ED）患者牙列缺损和（或）缺失重建中应用的可行性、功能及美观效果。方法 依据临床检查及X线检查结果，将种植体植入外胚叶发育异常的患者颌骨内，当种植体与骨发生骨性整合后行义齿修复，并选择适当的附着体以增强义齿的固位。结果 5例患者共植入12颗种植体，在为期6～48个月的临床观察中，除1颗种植体周有轻度软组织炎症外，其他种植体周软组织健康状况良好，全部种植体均形成良好的骨整合，所有患者均认为义齿对美学效果、咀嚼功能、发音等均有明显改善，自信心提高。结论 在外胚叶发育异常患者牙列重建中，种植义齿可达到良好的治疗效果。     

白榴石微晶化增强牙科玻璃陶瓷的热处理温度制度的研究

目的 探索白榴石微晶化的热处理温度制度。方法 根据白榴石的化学式和K20-Na2O-Al2O3-SiO2系统相图制定原材料配比，在预设的熔融、成核、析晶温度中选择最佳温度；利用偏振光显微镜和x射线衍射分析仪观察样品的形态及显微结构特性。结果 玻璃融熔温度为1600℃，成核温度为1200℃，晶化温度为1500℃；微晶化后的自榴石晶粒约0．8μm，在玻璃基质中分布均匀。结论 按照一定的热处理温度制度。白榴石可以在玻璃中微晶化。     

DETERMINATION OF TANGENTIAL AND NORMAL COMPONENTS OF ORAL FORCES

Oral forces applied to human teeth during biting and mastication are normally described in the literature only in terms of their axial components. The purpose of this study was to fully determine the spatial characteristics of the oral resultant force – its normal and tangential components - for a given individual. A load cell was especially manufactured to measure oral force and was temporarily implanted as a prosthetic device in the dental arch of a volunteer, replacing his missing upper first molar. The mastication and occlusion tests were carried out in such a way the cell should withstand the loads applied to the molar, and its state of strain was recorded by strain gauges attached to it. Based on the results of these tests and using balance equations, normal and tangential components of the resultant oral force were determined. For direct occlusion, without interposition any obstacle between cusps, a peak normal force of 135 N was recorded simultaneously to a tangential force of 44 N. For mastication of biscuits, a peak normal force of 133 N and a tangential force of 39 N were obtained.