兔咬合创伤时咬肌损伤与线粒体Ca2+载的研究

目的研究咬合创伤导致咬肌损伤的作用和线粒体Ca2+超载在损伤机制中的作用.方法在兔一侧前磨牙粘固(牙合)板造成咬合创伤,皮下注射乙二胺四乙酸(ethylenediarninetetraacetic Acid,EDTA),同时建立对照组,10天后检测兔咬肌线粒体Ca2+含量,观察咬肌的组织学改变,并进行比较分析.结果戴(牙合)板而不注射EDTA兔的(牙合)板侧咬肌线粒体Ca2+含量明显升高,并有明显的超微结构改变;(牙合)板对侧及戴(牙合)板并注射EDTA兔的双侧咬肌线粒体Ca2+含量均与对照组无显著性差异,组织学改变亦不明显.结论咬合创伤是咬肌损伤的致病因素之一,而线粒体Ca2+超载则是咬肌损伤发生机制中的一个重要环节.     

Early endosseous integration enhanced by dual acid etching of titanium: a torque removal study in the rabbit

Textured implant surfaces are thought to enhance endosseous integration. Torque removal forces have been used as a biomechanical measure of anchorage, or endosseous integration, in which the greater forces required to remove implants may be interpreted as an increase in the strength of bony integration. The purpose of this study was to compare the torque resistance to removal of screw-shaped titanium implants having a dual acid-etched surface (Osseotite) with implants having either a machined surface, or a titanium plasma spray surface that exhibited a significantly more complex surface topography. Three custom screw-shaped implant types - machined, dual acid-etched (DAE), and titanium plasma sprayed (TPS) - were used in this study. Each implant surface was characterized by scanning electron microscopy and optical profilometry. One DAE implant was placed into each distal femur of eighteen adult New Zealand White rabbits along with one of the other implant types. Thus, each rabbit received two DAE implants and one each of the machined, or TPS, implants. All implants measured 3.25 mm in diameter x 4.00 mm in length without holes, grooves or slots to resist rotation. Eighteen rabbits were used for reverse torque measurements. Groups of six rabbits were sacrificed following one, two and three month healing periods. Implants were removed by reverse torque rotation with a digital torque-measuring device. Three implants with the machined surface preparation failed to achieve endosseous integration. All other implants were anchored by bone. Mean torque values for machined, DAE and TPS implants at one, two and three months were 6.00+/-0.64 N-cm, 9.07+/-0.67 N-cm and 6.73+/-0.95 N-cm; 21.86+/-1.37 N-cm, 27.63+/-3.41 N-cm and 27.40+/-3.89 N-cm; and 27.48+/-1.61 N-cm, 44.28+/-4.53 N-cm and 59.23+/-3.88 N-cm, respectively. Clearly, at the earliest time point the stability of DAE implants was comparable to that of TPS implants, while that of the machined implants was an order of magnitude lower. The TPS implants increased resistance to reverse torque removal over the three-month period. The results of this study confirm our previous results that demonstrated enhanced bony anchorage to dual acid-etched implants as compared to machined implants. Furthermore, the present results indicate that dual acid etching of titanium enhances early endosseous integration to a level which is comparable to that achieved by the topographically more complex TPS surfaces.     

Evaluation of the antimicrobial effectiveness of citric acid and sodium hypochlorite on the anaerobic flora of the infected root canal

This study was designed to evaluate the antimicrobial effectiveness of 25% citric acid, compared with 2.5% sodium hypochlorite, after time intervals of 5, 15, 30 and 60 min. Anaerobic bacterial species were isolated from infected root canals and categorized according to Gram stain as Gram-positive cocci, Gram-negative cocci, Gram-positive rods and Gram-negative rods. The experimental method used was similar to that proposed by the German society for Hygiene and Microbiology (DGHM) with slight modifications. Testing revealed that citric acid does demonstrate anti microbial properties against anaerobic bacteria, especially against cocci, but it is less effective than 2.5% sodium hypochlorite.     

聚乳酸-聚乙二醇的制备及骨修复实验研究

目的研究聚乳酸-聚乙二醇（PLA—PEG）共聚物作为细胞因子骨形态发生蛋白（BMP）、碱性成纤维细胞生长因子（bFGF）的载体修复下颌骨缺损的效果。方法制备多孔PLA—PEG共聚物并对其进行表征。将PLA—PEG／BMP（实验组1）、PLA—PEG／BMP／bFGF（实验组2）和PLA—PEG（对照组）分别植入27只雄性新西兰白兔的下颌体部骨缺损处。术后、2周、4周和8周，对实验标本的成骨状况进行大体、X线、组织学：扫描电子显微镜观察及计算机图像分析。结果实验期间各组成骨活跃。2周时实验组2成骨量最多，实验组1其次，对照组最少，差异在统计学上有显著性意义（P〈0．05）；4周时实验组2成骨量最多，其余两组成骨量差异不大（P〉0．05）；8周时各组的成骨量的差异在统计学上无显著性意义（P〉0．05）。结论新型的PLA—PEG共聚物呈现良好的生物相容性和骨引导性，是BMP和bFGF的良好载体。     

Effect of xylitol on mutans streptococci and lactic acid formation in saliva and plaque from adolescents and young adults with fixed orthodontic appliances

This study aimed to investigate two dose regimens of xylitol-containing tablets on the ecology of dental plaque and saliva during treatment with fixed orthodontic appliances. The study group comprised 56 healthy patients (mean age 15.8 yr) randomly assigned into the following groups: A, (n = 23) two xylitol tablets two times a day (1.7 g xylitol d(-1)) for 18 wk; B, (n = 23) two tablets four times per day (3.4 g xylitol d(-1)) for 18 wk; and C, (n = 10) no tablets. The levels of mutans streptococci (ms) were enumerated in plaque and saliva and the proportion of xylitol-sensitive (X(S)) strains in saliva was determined by autoradiography with [(14)C]-xylitol at baseline and at 6, 12, and 18 wk. The lactic acid formation rate was assessed enzymatically in sucrose-challenged plaque suspensions. A drop in salivary ms levels was found in Group A after 6 wk but not after 12 or 18 wk. The proportion of X(S) ms was decreased after 6 wk in groups A and B and remained so during the experimental period. The lactic acid formation rates decreased slightly ( approximately 10%) in the two xylitol groups compared with baseline. In conclusion, our results showed that although an alteration of ms strains was demonstrated following a regular daily low-dose intake of xylitol, the long-term total ms counts in plaque and saliva as well as plaque acidogenicity remained unchanged.     

The role of ascorbic acid in oral cancer and carcinogenesis

L-ascorbic acid is an essential dietary vitamin in humans, primates and certain mammals and is endogenously syn-thesised in some species. Epidemiological and ecological studies have shown that L-ascorbic acid has a protective effect against cancer, in particular non-hormone-dependent malignancies, such as oropharyngeal neoplasms. Experimental in vivo and in vitro studies, however, have yielded more controversial results, suggesting that the effects of L-ascorbic acid are dose- and perhaps, time-dependent with different effects depending on the species or organ studied. An update of the epidemiological and experimental evidence linking L-ascorbic acid to oral cancer and carcinogenesis is discussed together with a brief review of the possible mechanisms of action of L-ascorbic acid.     

Effect of desensitising toothpastes on dentinal tubule occlusion: A dentine permeability measurement and SEM in vitro study

Objectives

The purpose of this study was to evaluate the in vitro effectiveness of a new bioglass-containing and two commercial desensitising toothpastes on dentinal tubule occlusion after citric acid challenge or artificial saliva (AS) immersion.

Methods

One hundred dentin discs from human third molars were used. Specimens were randomly divided into five groups (n = 20), Group 1: EDTA-treated dentin; Group 2: brushing with distilled water; Group 3: brushing with Novamin; Group 4: brushing with Sensodyne Freshmint; Group 5: brushing with Colgate Sensitive. In each group, samples were then equally split into two subgroups (n = 10) to test two post-treatments: 6% citric acid challenge or 24 h immersion in artificial saliva. Dentine permeability of each specimen was measured before and after each treatment using a hydrostatic device working at 20 cm H₂O pressure. Data were analysed by two-way repeated measures ANOVA to determine if there were any significant differences within or between groups. Dentine morphology and surface deposits were observed by SEM.

Results

All three desensitising toothpastes significantly reduced dentine permeability and created precipitates on the treated dentine surfaces. Moreover, the reductions in dentine permeability showed partial recovery after a citric acid and artificial saliva immersion. Sensodyne showed significant resistant to acid attack and Novamin exhibited the lowest permeability after artificial saliva immersion for 24 h.

Conclusions

The application of the three toothpastes resulted in effective dentinal tubule occlusion. However, the new bioglass-containing toothpaste (Novamin) represented excellent occlusion effects after brushing treatment and AS immersion, while Sensodyne demonstrated more reduction in permeability when citric acid challenged.     

Expression of fatty acid synthase (FASN) in oral nevi and melanoma

Oral Diseases (2011) 17 , 808–812 Objective: The aim of this study was to determine the expression of fatty acid synthase (FASN) in oral nevi and melanomas, comparing the results with correspondent cutaneous lesions. Materials and Methods: Expression of FASN was evaluated by immunohistochemistry in 51 oral melanocytic lesions, including 38 intramucosal nevi and 13 primary oral melanomas, in 10 cutaneous nevi and in 14 melanomas. Results: Fatty acid synthase was strongly expressed only in melanomas, either of the oral mucosa or cutaneous. On the other hand, most oral and cutaneous nevi were negative, with a few oral cases showing focal and weak expression. Conclusion: Fatty acid synthase is expressed in malignant melanocytes, and it can be a helpful marker to distinguish oral melanomas from oral melanocytic nevi.     

Effect of cervical coating of ethyl cellulose polymer and metacrylic acid copolymer on the radicular penetration of hydrogen peroxide during bleaching

Abstract Extraradicular leakage of oxidizing agents during bleaching is an undesirable event and thus need to be prevented. The effect of external cervical coating of ethyl cellulose (EC) and metacrylic acid copolymer (MAC) on the radicular penetration of hydrogen peroxide during intracoronal bleaching was examined. Single rooted human premolars extracted for orthodontic reasons were used. The cementum covering the cemento-enamel junction was mechanically removed and the teeth treated endo-dontically and bleached with 30% hydrogen peroxide. Radicular hydrogen peroxide penetration was measured before coating the teeth and after applications of 1–3 layers of EC or 3 layers of MAC external cervical coatings. It was found that the radicular penetration of 30% hydrogen peroxide was related to the number of layers of cervical EC coatings. Application of one layer of EC did not reduce the hydrogen peroxide penetration. Two and three layers of EC reduced the hydrogen peroxide penetration by 38% and 85% respectively. Three layers of MAC reduced the radicular hydrogen peroxide penetration in 83%. Statistically, a highly significant difference was found between the teeth coated with three layers of either EC or MAC and the noncoated teeth (p< 0.001). It was concluded that application of ethyl cellulose or metacrylic acid copolymer to exposed cervical root surfaces may effectively prevent extraradicular leakage of bleaching agents.