Prevalence of dentin hypersensitivity among the residents of Xi’an city,China

Objective: To investigate the prevalence and intra-oral distribution of dentine hypersensitivity (DH) and to evaluate the related risk factors.

Material and methods: A total of 1320 subjects, aged between 20 and 69 years old, were selected from six communities in the urban areas of Xi’an, China. The data were collected by conducting individual interviews using a standard questionnaire; then, the clinical examination was performed for patients who reported about the discomforts they felt in their teeth when subjected to chemical, mechanical and thermal stimuli. Dentine hypersensitivity (DH) was diagnosed by a subject short, sharp pain in response to a blast of cold air from a triple syringe.

Results: While replying to the questionnaire, 445 subjects reported about signs of discomfort in the teeth. DH was diagnosed in 336 persons by clinic examination. Thus, the overall prevalence of DH was 33.7% in the questionnaire and 25.5% in the intraoral test. The prevalence of DH was higher in females (33.8%) than in males (22.2%). Furthermore, we found that the prevalence of DH was highest in the age group of 50–59 years (39.3%). The most common initiation factors were acid (37.7%) followed by cold stimuli (35.8%). In general, most subjects with sensitive teeth had a higher educational background.

Conclusions: The prevalence of DH was 25.5% in the population of Xi’an City in China. More emphasis should give to middle-aged and old females while planning oral health intervention campaigns. In addition, premolars and cervical surfaces should be examined for the prevention of DH.     

Trueness analysis of zirconia crowns fabricated with 3-dimensional printing

Statement of problem

The primary manufacturing method of zirconia ceramic crowns is computer-aided design and computer-aided manufacture (CAD-CAM), but a disadvantage of this technique is material waste. Three-dimensional (3D) printing, which has been recently introduced into dentistry, has improved the processing of polymers and metals, but not yet of ceramic crowns.

Is modified Carnoy’s solution as effective as Carnoy’s solution in terms of amount of bone necrosis and depth of penetration?

Carnoy’s solution, a chemical cauterisation agent, has been indicated as one of the adjuvant treatment modalities for odontogenic keratocyst. In 2000, after the ban of chloroform many surgeons adopted the use of Modified Carnoy’s solution. The purpose of this study is to compare the depth of penetration and amount of bone necrosis of Carnoy’s versus Modified Carnoy’s solution on the mandible of Wistar rats at different time intervals. Twenty-six male Wistar rats of six to eight weeks old, weighing approximately 150–200 grams, were allocated for this study. The predictor variables were type of solution and application time. The outcome variable was depth of penetration and amount of bone necrosis. Carnoy’s solution was applied on the defect on the right side of the mandible and Modified Carnoy’s solution on the left side for five minutes on eight rats, eight minutes on eight rats, and 10 minutes on eight rats. All specimens were subjected to histomorphometric analysis done using Mia image AR software. Univariate ANOVA test, and paired sample t test was done to compare the results. The depth of penetration for Carnoy’s solution was more than Modified Carnoy’s solution in the three different exposure times. Statistically significant results were observed at five minutes and eight minutes. The amount of bone necrosis was more in Modified Carnoy’s solution. The results were not statistically significant at the three different exposure times. To conclude, when one wants to use Modified Carnoy’s solution, the minimum exposure time should be 10 minutes to achieve similar results as those of Carnoy’s solution.     

西帕依固龈液和没食子体外抗白色念珠菌的活性测定

目的：体外观察西帕依固龈液和没食子对白色念珠菌的作用,并对二者的抑菌和杀菌效果进行评价。方法：采用常量肉汤稀释法,检测西帕依固龈液和没食子的抑菌和杀菌效果。结果：西帕依固龈液对白色念珠菌的最低抑菌浓度（MIC）为5mg/ml,最低杀菌浓度（MBC）为10mg/ml;没食子提取液对白色念珠菌的最低抑菌浓度（MIC）为25mg/ml,杀菌浓度（MBC）为50mg/ml。结论：没食子提取液和西帕依固龈液在体外均具有一定的抗白色念珠菌活性。     

口腔矫形颌位研究进展与临床应用

提要：口腔矫形颌位通常是用来描述髁突位于舒适的、可重复的、重建牙尖交错牙合时必须依赖的颌位,是患者义齿修复或正畸等口腔治疗后,下颌的生理功能运动颌位。本文从临床操作的角度,及垂直向的关系和髁突位置确定,总结目前争论的几种口腔矫形颌位观点,并认为口腔矫形颌位不是某个单独的点,而是一个可接受的范围,只要能够形成和谐的颌位与牙尖交错牙合关系,牙合能在生理位行使功能,就可以认为矫形颌位的定位是正确的。     

应用电子散斑法对金沉积薄片弹性模量和泊松比的测量

目的：测量金沉积薄片的弹性模量和泊松比,为金沉积修复体的生物力学分析提供准确的材料物理参数。材料与方法：制作一定长度和宽度的金沉积薄片试件2条,采用电子散斑法测量其弹性模量和泊松比。结果：实验测得金沉积薄片的弹性模量为50.5GPa,泊松比为0.44。结论：运用电子散斑法可以间接准确地测量金沉积薄片的弹性模量和泊松比。     

Marginal opening of single and twin platinum foil-bonded aluminous porcelain crowns

The marginal openings of single and twin foil-bonded aluminous porcelain crowns were compared in crowns fabricated indirectly for extracted teeth and directly on typodont teeth. The crowns were cemented with zinc phosphate, embedded in plastic, and sectioned. Marginal opening was measured directly with a traveling microscope. There was no significant difference between the marginal openings of twin- and single-foil crowns fabricated indirectly for extracted teeth. When the crowns were constructed directly on typodont teeth to eliminate the variables of impression-making and die fabrication, the single-foil crowns possessed a significantly smaller marginal opening than the twin-foil crowns. Both the twin- and single-foil complete porcelain crowns resulted in clinically acceptable margins. The single-foil crowns were easier to make.     

Evaluation of ceramic margins for metal-ceramic restorations

This study evaluated various techniques for forming ceramic margins on metal-ceramic restorations. Marginal openings were measured using a scanning electron microscope on replicas derived from elastomeric impressions. Ceramic margins formed with a platinum foil backing showed significantly better fit than those formed with direct-lift techniques. With the platinum foil method these ceramic margins displayed a marginal fit comparable to that obtained with cast metal margins.     

Laminagraphic study of mandibular condyle position when recording centric relation.

Laminagraphs were made of each temporomandibular joint of 20 subjects (1) with the mandible forcefully retruded to centric relation and (2) with the mandible positioned by a closing force while an anterior guidance prosthesis was being used. The radiographs were compared by measurements of condylar position; results indicated the condyles to be significantly more superior in the glenoid fossa when anterior guidance was used. The difference in anterior-posterior positioning of the condyles appeared to occur randomly. Measurements of the joint spaces with the mandible in centric relation using anterior guidance indicated that mandibular condyles were not centered in the fossae. There seemed to be a range in the size of the space that could be considered normal.