A re-evaluation of the distribution of the elastic meshwork within the periodontal ligament of the mouse

The elastic properties of the periodontal ligament have been attributed, in part, to oxytalan fibers, as no other types of elastic fibers are described there. It has been difficult to study the periodontal elastic meshwork by standard microscopic techniques because it is partially obscured by the adjacent periodontal ligament collagen fibers. Our study employed methods which either completely or partially removed mandibular molar periodontal ligament collagen fibers, exposing a previously undescribed periodontal elastic meshwork. The periodontal elastic meshwork was composed of many elastin lamellae containing both peripheral microfibrils of regular arrangement and central microfibrils of irregular arrangement, which could only be demonstrated in oxidized tissues. Peripheral, regularly arranged bundles of microfibrils resembled oxytalan fibers, which were often adherent to the border of the elastin lamella. Elastin lamellae containing irregular microfibrils resembled elaunin fibers. These fibers probably enclosed either blood vessels, nerves or collagen fiber bundles. Peripheral microfibrils attached elaunin to cementum, alveolar bone, blood vessels, and principal periodontal collagen fibers. Thus, the periodontal elastic meshwork is composed of both oxytalan and elaunin fibers. Microfibrils attach elaunin fibers to the adjacent non-elastic tissue and also form bundles which traverse the periodontal ligament space and are probably the oxytalan fibers demonstrable by light microscopic techniques. This meshwork of oxytalan and elaunin fibers probably contributes to tooth support and maintenance of periodontal homeostasis by dissipating chewing forces and maintaining patency of periodontal blood vessels.     

螺圈对垂直曲力学行为的影响

目的 研究不同位置的螺圈及预成角度对垂直曲力学行为的影响。方法 利用大型有限元软件 ANSYS进行模拟计算。结果 螺圈的加入对垂直曲的M/F值的变化较明显。结论 对预成螺圈曲进行合理的形状设计,可以达到满意的效果。     

主观判听在腭咽闭合功能诊断中的应用价值

目的通过比较主观判听与客观检查诊断腭咽闭合功能的一致性,阐明主观判听在腭咽闭合诊断上的临床应用状况。方法对2000-2010年在四川大学华西口腔医院唇腭裂外科就诊的254例腭裂患者的语音资料进行回顾性分析。统计其主观判听结果和鼻咽纤维镜检查结果,计算二者的诊断一致率。应用Kappa检验和相关分析统计主客观评估的一致性和相关性。应用相关分析统计主观评估影响因素的相关系数。结果在254例腭裂患者中,主、客观评估一致的腭咽闭合完全（VPC）与腭咽闭合不全（VPI）病例数分别为58、167例,诊断一致率为88.58%,其中VPC诊断一致率为66.67%。Kappa值为0.721,R=0.751,P＜0.05,主、客观评估具有高度的一致性和相关性。高鼻音和鼻漏气与主观判听结果的相关系数R分别为0.697、0.590,P＜0.05,二者具有明显的相关性。结论主观判听诊断为VPC,以及主观判听为中重度高鼻音及鼻漏气的VPI患者可以免作客观检查;主观判听为轻度鼻漏气和高鼻音的患者需要结合客观检查,进一步明确腭咽闭合的诊断。     

秦始皇帝陵区出土人第三磨牙的萌出情况

目的：调查秦始皇帝陵区山任陶窑遗址中人体颌骨第三磨牙的萌出情况。方法：选用秦代人体颌骨98副，观察萌出特点，计算阻生率，分析阻生情况。结果：通过对98副标本的观察，发现秦代人同现代人类一样可发生第三磨牙的多种萌出状况，其中包括先天缺失、畸形牙、阻生、正常萌出等。结论：秦始皇帝陵区山任陶窑遗址中人体颌骨具有同现代人类一样的第三磨牙萌出特点。     

The variability of the curvature of the labial surface of the upper anterior teeth along the facial axis of the clinical crown

OBJECTIVE: To mathematically assess the curvature of upper anterior teeth along the facial axis of the clinical crown (FACC) line to provide information valuable for assessment of enamel growth. METHODS: Forty upper study models were chosen from the Orthodontic clinic at the Charles Clifford Dental Hospital, Sheffield, UK. The study model incisors and canines were sectioned longitudinally down the FACC line, using a Microslice II cutting machine. Images were captured that showed the proximal view of the tooth curvature from incisal edge/cusp tip to the gingival margin. The images were converted into silhouettes and saved as bitmap files. These were vectorised and converted to an outline of xy data points. The forty xy files were mathematically adjusted so the distance between incisal edge and gingival margin were of equal length. Non Rotational Principal Component Analysis (PCA) was then applied at 20 equal intervals along the curve of each xy file to describe the shape of the teeth. RESULTS: Intra class correlation coefficient for intra-operator repeatability ranged from 0.821-0.998 showing good or excellent levels of reliability. PCA showed variation between tooth types. CONCLUSIONS: The method proved reliable. All tooth types showed that the mid-point region had the greatest rise variable, indicating that the most-prominent point was central or incisal for central and lateral incisors. All were skewed towards the incisal end and had kurtosis at both ends. Central incisors showed least variability. Greater variability was seen within the incisal third than within the gingival third for all tooth types.     

Influence of the thyroid upon the glycosaminoglycans in the salivary glands in the rat

The glycosaminoglycans of the salivary glands were studied in male rats 2 months after radiothyroidectomy, and after the daily administration of 0.1 and 1.0 μg of sodium-1-triiodothyronine to radiothyroidectomized rats for 1 month. Total uronic acid concentration was determined in the salivary glands. Chromatographie separation of the uronic acid fractions was performed on cellulose microcolumns. Radiothyroidectomy increased and the administration of triiodothyronine decreased the uronic acid concentration in the submandibular glands. These changes occurred only in the hyaluronic acid and glycoprotein fractions. No changes in uronic acid concentration were detected in the retrolingual and parotid glands.     

托槽在数字化牙颌模型上位置与间接粘结转移后实际位置的一致性研究

目的 本研究比较托槽在数字化牙颌模型上的位置与转移至初始石膏模型上的位置的差异,以期为数字化托槽间接粘结位置的一致性提供实验依据.方法 选取在含牙根的数字化牙颌模型上进行托槽定位的15个数字化模型,通过间接粘结转移托盘将托槽转移至初始石膏模型上,用OrthoRx软件工具测量每个托槽在数字化牙颌模型上的位置与初始石膏模型上位置的线距差.结果 所有牙位托槽在数字化牙颌模型上的位置与初始石膏模型上位置的线距差值均小于检验值0.20 mm,与检验值差异有统计学意义(P<0.05).结论 托槽在数字化牙颌模型上的位置与初始石膏模型上位置具有一致性.     

Tooth Movement Activates the Central Amygdala and the Lateral Hypothalamus by the Magnitude of the Force Applied

Objective:To determine if the magnitude of the force used to induce incisor tooth movement promotes distinct activation in cells in the central amygdala (CEA) and lateral hypothalamus (LH) of rats. Also, the effect of morphine on Fos immunoreactivity (Fos-IR) was investigated in these nuclei.Materials and Methods:Adult male rats were anesthetized and divided into six groups: only anesthetized (control), without orthodontic appliance (OA), OA but without force, OA activated with 30g or 70g, OA with 70g in animals pretreated with morphine (2 mg/kg, intraperitoneal). Three hours after the onset of the experiment the rats were reanesthetized and perfused with 4% paraformaldehyde. The brains were removed and fixed, and sections containing CEA and LH were processed for Fos protein immunohistochemistry.Results:The results show that in the control group, the intramuscular injection of a ketamine/ xylazine mixture did not induce Fos-IR cells in the CEA or in the LH. Again, the without force group showed a little Fos-IR. However, in the 70g group the Fos-IR was the biggest observed (P < .05, Tukey) in the CEA and LH compared with the other groups. In the 30g group, the Fos-IR did not differ from the control group, the without OA group, and the without force group. Furthermore, pretreatment with morphine in the 70g group reduced Fos-IR in these regions.Conclusions:Tooth movement promotes Fos-IR in the CEA and LH according to the magnitude of the force applied.     

常用国产、进口正畸托槽的槽沟宽度精度及表面光洁度的比较

目的比较临床常用的国产金属直丝弓托槽和进口金属直丝弓托槽槽沟宽度及其精度、槽沟近远中截面光洁度和结扎翼光洁度。方法采用施奈德坐标测量仪对4种国产金属直丝弓托槽和4种进口金属直丝弓托槽放大30倍后进行测量。结果国产托槽和进口托槽槽沟的近、远中宽度均有良好的一致性,但国产托槽和进口托槽槽沟宽度普遍大于设计值;进口托槽槽沟近远中端截面的光洁度优于国产托槽,国产托槽结扎翼表面光洁度已达到进口托槽结扎翼表面光洁度水平。结论绝大部分国产和进口直丝弓金属托槽槽沟宽度较设计值大,个别品牌托槽槽沟宽度显著大于设计值。国产和进口金属托槽结扎翼表面均有较好的抛光度,但国产托槽槽沟内的抛光工艺尚待提高。     

咀嚼对无牙颌患者脑血流动力学影响的研究

目的 观察无牙颌患者咀嚼运动前后脑血流的改变,探讨咀嚼对脑血流动力学的影响.方法 应用经颅彩色多谱勒超声扫描仪,探测30名戴用全口义齿3个月内的无牙颌患者,在安静状态下及戴用全口义齿和不戴义齿咀嚼无糖口香糖10min后脑血流速的改变,对大脑中动脉收缩期峰流速、舒张期末峰流速、平均峰流速进行统计分析.结果 30名无牙...     

Location of implants in the interforaminal region of the mandible and the consequences for the design of the superstructure

The location and the number of implants to support an overdenture is of major importance for the superstructure design. Sometimes, jaw bone anatomy or posteriorly placed implants enforce the use of an angular bar to achieve a position above the alveolar ridge. Loads on such a bar may introduce a moment on the implants which can result in high bone stresses and eventually the loss of the implants.
This study on stress distribution in the bone around the implants in an edentulous mandible was performed using a three-dimensional finite element model. One model with two implants placed just anteriorly of the mental foramen and connected with an anteriorly placed bar, following the curvature of the alveolar ridge, was compared with two other designs. First with a similar model but now without a bar and secondly with a model with four implants connected with straight bars.
It is concluded that loading a bar, which is placed anteriorly of the interconnecting line between two implants, causes extremely large compressive and tensile stress concentrations in the bone around the implants. Therefore, in those cases, it is advised not to connect the implants or, in case a bar-clip attachment is preferred, to place additional implants in the frontal region.