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.     

Adhesion of composite resin to etched glass ionomer cement

A laboratory study was undertaken to determine the tensile bond strengths of three glass ionomer cements to dentine and the tensile bond strengths of composite to the three glass ionomers after etching. The tensile bond strength to untreated dentine was in the range of 4.47–5.52 MPa, being approximately twice that of a glass ionomer restorative material. After etching the glass ionomer, the bond strength to composite resin ranged from 1.83 MPa to 6.17 MPa, depending on the ionomer and on the time after mixing at which it was etched. In the majority of clinical situations, retention of a composite restoration via etched glass ionomer cement would probably need to be supplemented by additional mechanical retention.     

Resistance to fracture of restored endodontically treated teeth

Abstract Endodontically treated teeth were restored by 8 different methods. Copper rings were filled with commercial hard setting cement and the teeth were placed into the cement to the level of the cemento-enamel junction. The teeth were grouped according to restorative methods, mounted in an Instron T.T. machine and subjected to a slowly increasing compressive force until fracture occurred. The force of fracture for each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner, irrespective of restorative method used. Preparation of a post space in the roots significantly weakened the teeth. Cementation of a steel parapost with zinc oxyphosphate cement did not significantly strengthen the teeth. Filling the post space and the access cavity with a composite resin following acid etching of the root canal and cavity walls strengthened the teeth more than other methods used to restore them. This finding may be of clinical importance, for instance in the restoration of endodontically treated young teeth with incomplete root formation and wide root canals.     

Effects of trajectory wind direction on ion concentration of PM10

INTRODUCTION PM10 describes the mass of particles in the atmosphere with a size of less than 10 micrometers in diameter or has an aerodynamic diameter of 10 μm, and it is the commonly used international convention for measuring particles in ambient air[1…     

Inverted U-Shaped Associations between Glycemic Indices and Serum Uric Acid Levels in the General Chinese Population: Findings from the China Cardiometabolic Disease and Cancer Cohort (4C) Study

Objective The relationship between serum uric acid(SUA)levels and glycemic indices,including plasma glucose(FPG),2-hour postload glucose(2 h-PG),and glycated hemoglobin(HbA1 c),remains inconclusive.We aimed to explore the associations between glycemic indices and SUA levels in the general Chinese population.Methods The current study was a cross-sectional analysis using the first follow-up survey data from The China Cardiometabolic Disease and Cancer Cohort Study.A total of 105,922 community-dwelling adults aged≥40 years underwent the oral glucose tolerance test and uric acid assessment.The nonlinear relationships between glycemic indices and SUA levels were explored using generalized additive models.Results A total of 30,941 men and 62,361 women were eligible for the current analysis.Generalized additive models verified the inverted U-shaped association between glycemic indices and SUA levels,but with different inflection points in men and women.The thresholds for FPG,2 h-PG,and HbA1 c for men and women were 6.5/8.0 mmol/L,11.0/14.0 mmol/L,and 6.1/6.5,respectively(SUA levels increased with increasing glycemic indices before the inflection points and then eventually decreased with further increases in the glycemic indices).Conclusion An inverted U-shaped association was observed between major glycemic indices and uric acid levels in both sexes,while the inflection points were reached earlier in men than in women.