Occluding Efficiency of Different Desensitizing Agents and Er,Cr:YSGG Laser on Dentin Tubules.

PURPOSE: This study aimed to evaluate the effects of two desensitizers and the Er,Cr:YSGG laser on human dentin tubules, applied alone or in combination. METHODS: Ninety-six dentin specimens were obtained from extracted third molars and divided into six groups: Group 1: no-treatment (Control); Group 2: nano-hydroxyapatite desensitizer (NhapD); Group 3: NhapD+Er,Cr:YSGG laser (L); Group 4: Er,Cr:YSGG laser (L); Group 5: glutaraldehyde desensitizer (GD); and Group 6: GD+L, respectively. All specimens were evaluated using scanning electron microscopy. The diameter and the number of open dentin tubules, the tubules' occluding ratio, and the mineral coverage area were measured via the Image J software at 2000× magnification. Atomic force microscopy was used to determine the blocking mechanism of desensitizing treatments and the surface morphology of dentin specimens. One-way ANOVA and Tukey tests were used for statistical analysis. RESULTS: The number of open tubules and the mean diameter of tubules for all treatment groups showed statistically significant differences from the control group The NhapD+L group had a significantly lower number of open tubules than the L and GD groups. The NhapD+L and L groups significantly had higher occluding ratios than the other groups. CONCLUSIONS: The present study showed that the Er,Cr:YSGG laser alone was effective in terms of tubule occlusion and also contributed to increasing the occluding ratio of nano-hydroxyapatite. It may be recommended to use the Er,Cr:YSGG laser with nano-hydroxyapatite desensitizers to achieve effective tubule occlusion.

The effect of enamel bleaching on the shear bond strengths of metal and ceramic brackets.

The aim of this study was to evaluate the effects of bleaching and delayed bonding on the shear bond strengths of metal and ceramic brackets bonded with light and chemically cure composite resin to human enamel. One hundred and twenty extracted human premolar teeth were randomly divided into three groups of 40 each. The first two groups were bleached with 20 per cent carbamide peroxide (CP) at-home bleaching agent. No bleaching procedures were applied to the third group and served as control. The first two and control groups were divided into equal subgroups according to different adhesive-bracket combinations. Specimens in group 1 (n = 40) were bonded 24 hours after bleaching process was completed while the specimens in group 2 (n = 40) were bonded 14 days after. The specimens in all groups were debonded with a Universal testing machine while the modified adhesive remnant index was used to evaluate fracture properties. No statistically significant differences were found between the shear bond strengths of metal and ceramic brackets bonded to bleached enamel after 24 hours, 14 days, and unbleached enamel with light or chemical cure adhesives (P > 0.05). The mode of failure was mostly at the bracket/adhesive interface and cohesive failures within the resin were also observed. Our findings indicated that at-home bleaching agents that contain 20 per cent CP did not significantly affect the shear bond strength of metal and ceramic orthodontic brackets to enamel when bonding is performed 24 hours or 14 days after bleaching.

The relation between 6-n-propylthiouracil sensitivity and caries activity in schoolchildren.

Caries activity tests are being used to assess caries risk in children. In recent years the purpose of most studies has been to develop practical, quick, reliable and economic tests. Clinical studies showed that the difference in sensitivity to the bitter taste of 6-n-propylthiouracil (PROP) is a heritable trait and may influence children's nutritional habits and caries development. The aim of this study was to investigate the relation between PROP sensitivity and caries activity in schoolchildren, in comparison with different caries activity tests. One hundred and twenty children aged between 7 and 12 years (mean age 9.97 ± 1.59) were investigated to determine socioeconomic status and oral hygiene habits, fluoride consumption, DMFT, DMFS, df, dfs, plaque indexes, and nutritional habits. Children were divided into three groups according to their caries risk status based on the Cariogram. The solution test and the PROP-impregnated filter paper test were used together to determine PROP sensitivity. After all associated factors had been controlled, stepwise regression analyses revealed that DMFT and dfs scores were important determinants of PROP. According to dfs, the sensitivity of the Cariogram and of PROP tests was 0.85 and 0.70, respectively, and specificity was 0.32 and 0.33, respectively. There was an inverse significant relationship between PROP sensitivity and DMFT, DMFS, and dfs results (p < 0.01). In conclusion, PROP nontasters were significantly more likely to have high caries risk than PROP tasters (p < 0.01).

In vitro plaque formation on some dental filling materials.

The purpose of this study was to investigate the effects of filling and lining materials in various compositions on Streptococcus mutans. Five glass-ionomer cements (Vitrebond, XR Ionomer, Ketac-Bond, Shofu Base Cement, Shofu Lining Cement) and two composite materials (Heliomolar-RO, Concise) were used in this study. Samples from these materials were prepared in sterilized conditions and hung in tryptic soy broth medium containing 5% sucrose. The media were inoculated with Streptococcus mutans ATCC 13419. After 5 days, the plaque that had accumulated on the surfaces was scraped off and weighted in wet and dry conditions. Then the colonies were counted and evaluated in comparison with each other. The least amount of plaque and colony numbers were found on Vitrebond material disks. In conclusion, there were no differences among XR Ionomer, Heliomolar-RO and Ketac Bond. Concise gave better results than some materials containing fluoride; whereas the most abundant amounts of plaque were found on Shofu Lining Cement and Shofu Base Cement.

Monitoring the caries risk of orthodontic patients.

Several caries activity tests were used to investigate the caries risk of patients with fixed orthodontic appliances. Twenty young individuals, with a mean age of 11 years, participated in this study. Ten subjects were free of any orthodontic appliances and formed the control group. The other 10 individuals had been wearing fixed orthodontic appliances for at least 4 months. Stimulated saliva samples were obtained from all patients. Saliva samples were used to investigate the salivary flow rate, the salivary buffer capacity, and mutans streptococci and lactobacilli counts. The orthodontic patients exhibited a significant increase in salivary flow rate. Results of statistical analyses were nonsignificant in all other tests, suggesting that fixed orthodontic appliances are not the sole factor increasing the patient's caries risk during orthodontic treatment.

Fluoride concentration and profile in different cementum surfaces.

This study was performed to determine the fluoride concentration of the various cementum surfaces in different tooth groups to find out the most proper teeth and tooth surfaces for different cementum studies. For this purpose, direct measurements of phosphorus and fluoride were carried out in an acid etch biopsy solution. The findings indicate that incisors with exposed cementum are the most inappropriate teeth in comparison with the other groups. According to the results obtained it may be recommended that the studies related to fluoride uptake for cementum should be performed on teeth with no gingival recession or on the unerupted teeth.

Determination of fluoride release from light-cured glass-ionomers and a fluoridated composite resin from the viewpoint of curing time.

The purpose of this study was to investigate the fluoride releasing pattern of several visible light-curing glass-ionomers and one fluoride-containing filling material, from the viewpoint of curing time. Standardized blocks of Time Line (Caulk-USA), XR-Ionomer (Kerr-USA), Vitrebond (3M-USA) and Heliomolar-Ro (Vivadent-Lichtenstein) were light cured for 20, 40 and 60 s, and then stored in deionized distilled water at 37 degrees C for 24, 48, 72 h and 7 days. The water was changed every day and measurements of the fluoride released from the materials were made daily. The results were compared statistically with the results obtained from Ketac-Bond (Espe-Germany) prepared in the same manner. The levels were highest for the first 24 h; in the following days they decreased rapidly. The fluoride-releasing patterns of all these materials were similar to each other. The fluoride release was the highest from XR-Ionomer, and the lowest from Heliomolar-RO. For Time Line glass-ionomer, the fluoride release from 20 s cured blocks was significantly higher than the fluoride release from 40 and 60 s cured blocks at the end of 1 week. It was observed that the fluoride release from Ketac-Bond was significantly lower than XR-Ionomer and Vitre-Bond and higher than Time Line and Heliomolar-Ro.