Effects of systemic fluoride and in vitro fluoride treatment on enamel crystals

Systemically administered fluoride at a concentration of 75 ppm increases the surface roughness of developing enamel crystals in rats, which may be significant in advancing our understanding of the biological mechanism of fluorosis. Thus, the aim of this study was to investigate whether the increased surface roughness may be a result of surface restructuring by the direct action of fluoride at the crystal surface. We examined the fluoride dose-dependent roughening of enamel crystal surfaces in vivo, in the rat, and whether this roughening could be mimicked by the in vitro treatment of rat enamel crystals with neutral pH fluoride solutions. Our results showed that enamel crystal surface roughness increased after treatment with increasing fluoride ion concentrations, whether applied in vitro or administered systemically. This suggests a mechanism, alongside others, for the increased surface roughness of crystals in fluorotic enamel.     

Effect of occlusal trauma on healing of periapical pathoses: report of two cases

AIM: To present two clinical cases and demonstrate that occlusal trauma may affect healing of periapical pathoses. SUMMARY: Two teeth with periradicular disease did not respond successfully to conventional root canal treatment or endodontic surgery. Occlusal adjustment was finally performed on both cases. After occlusal adjustment, uncomplicated healing and periapical repair occurred in both cases. The findings in these two cases suggest that occlusal trauma may play a role in the healing of periapical pathoses. KEY LEARNING POINTS: Occlusal trauma is positively correlated with changes in periodontal tissues. Although experiments in animals have shown that application of forces to teeth will not induce further periodontal destruction, we believe that some failures of root canal treatment may be due to the presence of occlusal trauma modulating the responses of inflamed periapical tissues or apical pathoses with persistent infection.     

应用牵张成骨术整复腭裂骨质缺损的组织学研究

目的 :观察牵张成骨术整复腭裂过程中 ,新骨组织形成与改建活动的特点 ,探讨新骨生成的规律。方法 :家猫 14只为实验对象。其中 12只建立人工腭裂实验模型。实验组 (动物 10只 ) :以 0 .4mm× 2次 /d的速度与频率牵张整复腭裂缺损。于术后固定期 2、4、6、8及 12周 ,观察期结束前 6d ,各对 2只动物肌注四环素标记 ( 30mg/kg)。 6d后取标本 ,切片行荧光显微镜及组织学观察 ,并与实验对照组及空白对照组 (动物各2只 )结果对比。结果 :实验组标本牵张区新骨组织均为膜内成骨 ,由中央向外分为胶原纤维区、新骨形成区及改建成熟区 ;随时间发展 ,新生骨逐渐取代纤维组织并改建成熟。软组织也得到相应伸展。对照组裂隙无自行修复。结论 :应用牵张成骨术矫治腭裂骨质缺损 ,以原位产生新骨 ,增加骨量的方式推移骨运送盘封闭腭裂裂隙。在良好固定条件下 ,新骨形成与改建活跃 ,最终整复腭裂骨质缺损并适应功能需要     

A randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part IV: Comparisons of dietary intake

STATEMENT OF PROBLEM: It is unclear whether the replacement of conventional mandibular dentures with implant-supported overdentures alters the diet and thus improves the nutritional intake of edentulous persons. PURPOSE: The purpose of this study was to compare the pretreatment and posttreatment diets of edentulous diabetic patients who received new dentures with either a conventional complete mandibular denture (CD) or a mandibular implant-supported overdenture (IOD). MATERIAL AND METHODS: New dentures were made for 89 edentulous diabetic patients with acceptable metabolic control without insulin (NIT) or with insulin (IT). A randomized approach was used to assign 37 patients a mandibular CD and 52 patients a mandibular IOD supported by 2 cylindrical implants. Of the 89 patients, 58 submitted a dietary log for 7 consecutive days before treatment (PT) and 6 months after treatment completion (PTC). An average daily intake of 28 essential nutrients was determined for each patient at each time interval. Separate 2 x 2 x 2 repeated analysis of variance (ANOVA) tests were performed for each nutrient to compare the means of the 2 denture groups (CD and IOD), 2 diabetic groups (NIT and IT), and 2 time intervals (PT and PTC). The intakes were also compared with the recommended daily allowance (RDA). RESULTS: ANOVAs for all 28 nutritional variables showed no main effect for either denture type or diabetic treatment. Time effects were seen for magnesium, potassium, copper, and monounsaturated fats. The PTC mean intake of the total sample (N = 58) decreased for all 3 minerals and increased for monounsaturated fats with study dentures. Post hoc tests showed the differences between PT and PTC means to be statistically significant for only magnesium (P=.043) and potassium (P=.015). The percentage of patients with PT intake 25% or more below the RDA ranged from 33% to 85% in the CD group and from 24% to 100% in the IOD group for the same 11 nutrients. PTC fiber intake deficiency was noted in almost all participants. Carbohydrate consumption was markedly lower than that recommended by the American Diabetic Association. CONCLUSION: As is often the case with elderly groups, this group of edentulous diabetic patients showed highly comprised nutritional intakes of fiber, vitamins, and minerals. The replacement of old dentures with new dentures that included either a mandibular CD or IOD did not alter patient diets such that the patients improved their nutritional intakes of essential micronutrients and macronutrients.     

Mechanical response to functional loading around the threads of retromolar endosseous implants utilized for orthodontic anchorage: coordinated histomorphometric and finite element analysis

A 3-dimensional bone-implant finite element model was created. The objective was to further investigate the mechanical environment of cortical bone adjacent to the threads of a retromolar endosseous implant used for orthodontic anchorage to mesially translate mandibular molars in response to normal functional loading. This study emphasizes the stress invariants around and between the threads of the implant for future comparison to histomorphometric data from an ongoing clinical study. A strong stress pattern change was found immediately around the implant, which was reflected by a moderate change of stresses between the threads and a significant increase in stress at the tips of the threads.     

Immunohistological localization of cell adhesion proteins and integrins in the periodontium.

The distribution of the cell adhesion proteins vitronectin, fibronectin, tenascin, and laminin as well as several integrin subunits, alpha 2, alpha 5, and alpha v, was studied in primate periodontal tissues. Full baboon mandibular sections were analyzed by immunohistochemical methods in order to localize the molecules studied in both soft and hard tissues. Vitronectin was associated with the connective tissue of the marginal gingiva, the periodontal ligament, as well as the endosteum and periosteum. A notable finding was the particularly high staining intensity of vitronectin in the periodontal ligament. Fibronectin was widely distributed in the periodontal connective tissue and was also localized to the pericellular matrix of osteocytes and blood vascular elements. Epithelial basement membranes stained positively for both fibronectin and tenascin. These proteins were also expressed in the periosteal and endosteal connective tissues and the periodontal ligament. The staining intensity for tenascin was higher in zones along the cementum and bone surfaces. Laminin was, characteristically, limited to basement membranes of epithelium and endothelium. The distribution of fibronectin, tenascin, and laminin is related to previous findings in other species. The localization of the several integrin alpha-subunits is also described in full baboon mandibular sections. The vitronectin receptor (alpha v) had a uniquely strong expression in osteoclasts of the alveolar bone and was found, at lesser intensity, on periodontal ligament fibroblasts. The fibronectin receptor alpha subunit, alpha 5, was also observed on osteoclasts, and, in addition, was widely distributed on fibroblasts, cementoblasts, and osteoblasts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Expression of CD44s, CD44v5, CD44v6 and CD44v7-8 in betel quid chewing-associated oral premalignant lesions and squamous cell carcinomas in Taiwan

Aberrant expression of the cell surface adhesion molecule CD44 and its variant forms has been shown to be associated with the invasive and metastatic potential of cancer cells, and with poor prognosis in several types of cancers. Expression of CD44 standard (CD44s) and variant (CD44v) forms in oral squamous cell carcinoma (SCC), epithelial dysplasia (ED), epithelial hyperkeratosis (EH) and normal buccal mucosa (NBM) have been examined using antibodies to CD44s, CD44v5, CD44v6 and CD44v7-8. Positive CD44s, CD44v5, CD44v6 and CD44v7-8 staining was detected in all the specimens from NBM, EH and ED. Positive staining of CD44s, CD44v5, CD44v6 or CD44v7-8 was detected in 55 (88.7%), 48 (77.4%), 59 (95.2%) and 22 (35.5%) of the 62 SCC specimens, respectively. The positive staining of CD44v7-8 in oral SCC was significantly less than that in NBM ( P <0.01). No significant correlation was found between CD44v7-8 expression and daily or total consumption of betel quids or cigarettes by the SCC patients. The 5-year survival rate for patients with CD44v7-8-positive tumours was significantly higher than that for the CD44v7-8-negative group ( P <0.03). These results indicate that loss of CD44v7-8 expression may be a valuable factor for determining prognosis in oral SCC patients.     

牵引弓联合前牵引矫治替牙期前牙反(牙合)的牙颌结构变化

目的探讨牵引弓联合前方牵引对矫治安氏Ⅲ类错     

Solubility study of phytochemical cross-linking agents on dentin stiffness

Objectives

The effects of interactions between cross-linking proanthocyanidins (PA) in polar solvents and type-I collagen of demineralized dentin were investigated.

Methods

Three PA-rich extracts, two from grape seed (GSEP and GSES) and one from cocoa (COE), were dissolved (water, ethanol:water and acetone:water) and analyzed for their ability to increase the modulus of elasticity of demineralized dentin. Sound dentin beams (0.5 mm × 1.7 mm × 7 mm) were fully demineralized and divided into 12 groups according to the type of cross-linking agent and solvents used. Specimens were immersed in the respective solutions and tested at baseline, 10, 30, 60, 120 and 240 min.

Results

The elastic modulus (EM) of dentin was significantly increased by the PA treatment regardless of time (p < 0.05 for all times). The extracts showed different solubility in different solvents. GSEP showed the highest increase in EM when diluted in distilled water and acetone at all exposure times. Both GSEs showed superior results when diluted in distilled water and after 4 h of treatment, while COE produced strongest enhancement when dissolved in ethanol:water.

Conclusions

The results indicates that herbal extraction process and other pharmacognostic parameters have an important influence on extract solubility as well as constitution and, consequently, on the PA–dentin matrix interaction.     

The distribution of nitric oxide synthetase in Vcx and its relation with the expression of FOS induced by teeth movement in rats]

It was studied the central role of nitric oxide(NO) during experimental teeth movement and the relation between nitric oxide synthetase (NOS) positive neurons and FOS like immunoreactivity (FLN) with the NADPH-diaphorase histochemistry and immunocytochemical reaction method. Results indicated that NOS positive neurons and FLN showed typical distribution in Vcx and there was some overlap between them. It suggests that NO is involved in the central modulation of the stimulating message of teeth movement, and which further explains the central modulation mechanism of experimental teeth movement in rats.