Insights into and relative effect of chitosan-H, chitosan-H-propolis, chitosan-H-propolis-nystatin and chitosan-H-nystatin on dentine bond strength.

OBJECTIVE: The purpose of the study was to design and evaluate novel functional chitosan hydrogels (chitosan-H-propolis, chitosan-H-propolis-nystatin and chitosan-H-nystatin) by using the chitosan-H polymer as "dual function restorative materials". MATERIALS AND METHODS: The nystatin/antioxidant carrier gel was prepared by dispersion of the corresponding component in glycerol and 3% acetic acid with 5% chitosan gelling agent was then added to the dispersion with continuous mixing. The natural bio-adhesive functionalized chitosan hydrogels were combined with built in drug delivery system and bio-actives such as propolis in order to increase the dentin bond strength capacity and maintain therapeutic properties of the alternative drug delivery system. The surface morphology, release behaviors (physiological pH and also in acidic conditions), stability of nystatin:antioxidant:chitosan and the effect of the hydrogels on the shear bond strength of dentin were also evaluated. STATISTICAL ANALYSIS USED: Non-parametric ANOVA test was used to asses significance of higher shear bond values than dentine treated or not treated with phosphoric acid. RESULTS: The release of both nystatin and propolis confer the added benefit of dual action of a functional therapeutic delivery when comparing the newly designed chitosan-based hydrogel restorative materials to commercially available nystatin alone. Neither the release of nystatin nor the antioxidant stability was affected by storage. Chitosan-H, chitosan-propolis, chitosan-nystatin and chitosan-nystatin-propolis treated dentine gives significantly (P < 0.05) higher shear bond values (P < 0.05) than dentine treated or not treated with phosphoric acid. CONCLUSION: The added benefits of their unique functionality involve increased dentin adhesive bond strengths (after 24 h and after 6 months) and positive influence on the nystatin release. Nystatin was a model therapeutic agent, evaluating the concept of using functional materials as carriers for pro-drugs as well as displaying a certain degree of defence mechanism for free radical damage of the novel functional drug delivery. Overall, there was an insignificant relapse in the shear bond strength after 6 months.

Awareness of complications of oral piercing in a group of adolescents and young South African adults.

OBJECTIVES: Intraoral piercing as a body art has been gaining popularity amongst adolescents and young adults; however there is limited data on the awareness to complications associated with it. This study investigated the awareness of complications of oral piercing among a group of adolescents and young South African adults with intraoral piercings. STUDY DESIGN: A total of 250 patients with intraoral piercing were asked to complete a questionnaire on the awareness of complications of oral piercing and were then examined by two calibrated dentists to determine oral complications caused by the pierced ornament. RESULTS: Data revealed that 59.4% of the respondents were not aware of any complications in oral piercing. 24% of the respondents had intraoral piercing in the last 12 months, with a combined total of 17.2% having the procedure performed 5 to 7 years before. CONCLUSIONS: The general lack of awareness of complications related to oral piercing needs to be addressed by the dental community.

Microleakage and confocal laser studies of 2 single-step self-etching bonding agents/systems.

OBJECTIVES: This study investigated the microleakage, etching ability, and dentin-restorative interface of 2 different single-step self-etching bonding agents with compomers as restoratives. METHOD AND MATERIALS: Fifteen extracted noncarious human premolars were used for each dental material system. The bonding agent Xeno III was used with their compomer Dyract AP (Dentsply) and Adper Prompt L-Pop with their compomer Z2000 (3M Espe). Cylindrical cavities were prepared in enamel and dentin on the buccal surface at the cementoenamel junction and restored. The specimens were thermocycled and cut into slices, and the depth of dye penetration scored. The dentine-restorative interface was examined through a confocal scanning laser microscope. RESULTS: Microleakages between the enamel and dentin sides differed significantly for Xeno (Wilcoxon rank sum test; P = .0058) as well as for Prompt (P = .0106), while the microleakages between the dentin sides of Xeno and Prompt did not differ significantly. However, between the enamel sides, a significant difference was found (P = .000), with the highest value for Prompt. The confocal laser studies showed tag formation, penetration of the bonding agents deep into the tubules, and hybrid layer formation for both bonding agents. CONCLUSIONS: It can be concluded that both adhesives gave microleakage values for dentin that are on the lower side. However, careful inspection of the enamel side indicated that both cannot be recommended for enamel sealing.

Effect of LED curing on the microleakage, shear bond strength and surface hardness of a resin-based composite restoration.

To determine the effect of Light emitting diode (LED) curing on dental resins, microleakage, shear bond strength and surface hardness of a dental composite cured with different LEDs were determined and compared with conventional halogen curing. For microleakage, Class V cavities were restored with Esthet-X, divided into groups, and exposed to one of the curing protocols (Elipar Freelight in soft start and standard modes; Ultra-Lume 2; Spectrum 800). Standard dye penetration tests were performed and the data summarised in a 2-way contingency table of observed frequencies. The Chi-square test was used (p<0.05) to test for significant differences between the lights. For surface hardness, samples of Esthet-X were exposed to the light-curing units (LCUs). Vickers hardness was determined on the upper and the bottom surfaces. Data was subjected to statistical analysis using ANOVA (p<0.05). Shear bond strength was determined using a push out method. Comparisons (ANOVA, p<0.05) were made between the different curing protocols. No significant difference in microleakage could be demonstrated between the different LCUs at the enamel side (p=0.60). At the dentin side only the Elipar Freelight (soft start), could significantly reduce microleakage (p<0.01). The hardness score for the halogen light was significantly lower than for the LED lights (p<0.01). The Spectrum 800 and the Elipar Freelight (soft start) have significantly higher shear bond strengths than the others (p<0.01). It was concluded that the LED source is more efficient for a comparable overall power output.

Effect of LED curing on microleakage and microhardness of Class V resin-based composite restorations.

BACKGROUND: Polymerisation shrinkage is a critical limitation of dental composites and may contribute to microleakage, postoperative pain, tooth fracture, and secondary caries. It has been shown that curing methods play a significant role in polymerisation shrinkage of light-cured dental resins. The purpose of this study was to investigate the effect of a LED curing light on microleakage as well as microhardness of a dental composite. METHOD: For the microleakage test 32 Class V cavities were prepared in human premolars, conditioned with 35% phosphoric acid and treated with the bonding agent Prime & Bond NT. They were then incrementally filled with the composite Esthet-X and randomly divided into two groups of 16 each. The first group was cured by means of a Spectrum 800 set at 500 mW/cm2 for 40 seconds and the second group with the GC E-Light in standard mode. The specimens were thermo-cycled in a 0.5% basic fuchsin solution, sectioned and evaluated for dye penetration. For the microhardness test two groups of 6 specimens each were exposed using either the LED- or the Halogen curing unit. Vickers microhardness tests were performed immediately after curing as well as 24 hours later, on the top, and at the bottom surface. RESULTS: At the dentine/cementum interface, significantly less microleakage (p=0.004) was found when the restorations were cured with the LED-unit. At the enamel interface no significant difference (p=0.340) in microleakage was found between curing methods. Immediately after exposure significantly harder surfaces were found at the top (p<0.001) as well as at the bottom (p<0.001), using the halogen unit (p<0.05). CONCLUSION: Although a reduction in microleakage could be demonstrated exposing the composite restoration to an LED LCU, an effective microhardness ratio was not achieved.

Effect of power density on shrinkage of dental resin materials.

This study compares volumetric changes and rates of shrinkage during different stages of polymerization of dental resin composites and compomers exposed to the same total energy by using two different combinations of power density and exposure duration. A hybrid composite and its equivalent flowable and a compomer and its equivalent flowable were exposed using a halogen curing unit set at 400 mW/cm2 for 40 seconds and 800 mW/cm2 for 20 seconds: delivering 16 J/cm2 in both cases. Volumetric changes were recorded every 0.5 seconds using a mercury dilatometer. Ten replications per test condition were performed and the data were subjected to ANOVA. Statistically significant differences in shrinkage values and rates among different power densities were determined by means of paired t-tests at a 95% confidence level. Significantly more shrinkage (p<0.05) was found for the higher filled materials, Z250 and Dyract AP, when higher power density was used. However, no significant differences were found between their flowable counterparts when exposed to various power densities. Of the four materials, only Dyract AP exhibited no significant difference in shrinkage rate when various power densities were used. All the other materials exhibited significantly higher rates (p<0.05) at the higher power density.

The effects of light intensity and method of exposure on the hardness of four light-cured dental restorative materials.

AIM: To determine the microhardness of several light-curing dental restorative materials at the top surface as well as at a depth of 2mm. METHODS: Comparisons were made using different light sources. Four groups of five specimens each (3mm diameter, 2mm thick) of Z250 (composite), Filtek Flow (flowable composite), Dyract AP (compomer) and Dyract Flow (flowable compomer) were cured using different methods of exposure. The curing lights used were a Spectrum 800 halogen curing light at settings of 800 mW/cm2 and 400 mW/cm2 and an Optilux 501 ramping light. Vickers microhardness tests were performed at the top surface and at the bottom surface. RESULTS: Significant differences in microhardness between the top and bottom surfaces were demonstrated for all materials and with all light sources (p<0.05). The different exposures also produced significant differences (p<0.05). The light source used had less of an effect on the hardness of the compomers than the composites. CONCLUSIONS: Effective hardness ratios between the top and bottom surfaces were achieved with all three curing protocols. The effect of total energy application must be taken into account before assumptions can be made as to the effect on hardness using different exposure methods.

The effect of an additional flowable compomer layer on microleakage of Class V compomer restorations.

BACKGROUND: Polymerisation shrinkage and the associated stress on composite resins and surrounding structures have been regarded as a major cause of leakage and clinical failures in modern polymer restorations. The purpose of this study was to investigate the effect of an additional flowable compomer layer on the microleakage of Class V dental cavities, which were further filled with a compomer. METHOD: Cavities (32) were prepared in human premolars, conditioned with a non-rinsing agent (Prime & Bond NRC) and treated with the bonding agent (Prime & Bond NT). Sixteen of these cavities were then lined with a layer of flowable compomer (Dyract Flow, approximately 0.5 mm) and further filled with Dyract AP. The other 16 cavities were filled without the flowable compomer. The specimens were thermo-cycled in a 0.5% basic fuchsin solution, sectioned and evaluated for dye penetration using a scoring system of 0 to 4. RESULTS: Lower microleakage values were found at the enamel as well as at the dentine sides when a layer of Dyract Flow was used as a liner. Furthermore, significantly (p < 0.05) lower microleakage was found in enamel than in dentine for both layered and unlayered restorations. CONCLUSION: It can be concluded that a layer of flowable compomer (i.e. Dyract Flow) in a cavity under a compomer may be recommended to improve the marginal seal of a restoration.

The effect of different power densities and method of exposure on the marginal adaptation of four light-cured dental restorative materials.

PURPOSE: To determine whether marginal adhesion is sensitive to different irradiation parameters, we investigated the in vitro adhesion values of four dental resins on metal surfaces. METHODS: Four groups of eight specimens each of Z250, Filtek flow, Dyract AP and Dyract flow were placed in pre-treated stainless steel cavities and irradiated using different methods of exposure. The curing lights used were a Spectrum 800 halogen curing light at settings of 800 and 450 mW/cm(2) and an Optilux 501 ramping light. The maximum amount of push-out force required to displace the resin from the metal cavity was equated with adhesive value (shear bond strength). Comparisons (ANOVA, p<0.0001) were made within the same material and between the different materials when using different curing protocols. RESULTS: Significant lower bond strengths were recorded when curing was done by gradually increasing the intensity (ramping method) compared to curing with the fixed intensities (p>0.0001) Comparing the fixed intensities, significant lower bond strength values were obtained at 800 mW/cm(2) compared to 450 mW/cm(2) (p<0.0001). For all exposures, the two flowable materials demonstrated weaker values when compared to the higher filled materials. CLINICAL SIGNIFICANCE: The advantage of initial slow polymerization (more elasticity and less tension) obtained by the so-called "soft start" method, was offset by a rise in total polymerization shrinkage, when final curing was completed at 1130 mW/cm(2). These tests demonstrated that using halogen units, exposure for 40s with an intensity of 450 mW/cm(2) appeared to be the most promising for light-curing dental resin composites.