Physicomechanical Properties of Resin-Based Pit and Fissure Sealants Reinforced with Rice Husk Derived Nano Silica and Nanohydroxyapatite

@#Resin-based pit fissure sealants (RBS) are used to prevent occlusal caries in children. The success of RBS in preventing dental caries is largely influenced by its retention on the tooth surface, which is also affected by its physicomechanical properties. The physicomechanical properties of RBS can be enhanced through the addition of fillers. With the advent of nanofillers, the physicomechanical properties were improved without altering RBS flowability. The present study developed an RBS with a 70 wt% resin matrix and 30 wt% nanofillers. The resin matrix consisted of urethane dimethacrylate (55 wt%), triethylene glycol dimethacrylate (45 wt%), camphoroquinone (0.3 wt%), and 2-(dimethylamino) ethyl methacrylate (0.7 wt%). Silane-treated rice husk-derived nanosilica (20 wt%) and nanohydroxyapatite (10 wt%) were added as fillers. Clinpro, Fissurit FX, and an unfilled sealant were controls. All RBS were tested for surface roughness, Vickers hardness, flexural strength, and flowability. Statistical analysis with oneway ANOVA revealed significant differences between groups in surface roughness, hardness, flowability (p < 0.001), flexural strength, and flexural modulus (p < 0.05). Experimental sealants had higher flexural strength (78 MPa) and flow distance (29.05+1.16 mm) than commercial controls.However, the surface roughness of experimental sealants (0.25+0.08 μm) was higher than Clinpro (0.087+0.027 μm) but lesser than Fissurit FX (0.35+0.19 μm). The Vickers hardness of experimental sealants (23+1.63 VHN) was less than Fissurit FX (28.80+1.69 VHN) but higher than Clinpro (21.74+1.68 VHN). This novel RBS had physicomechanical properties comparable to commercial sealants. The use of nanosilica from rice husk makes this pit and fissure sealer sustainable and environmentally friendly in dentistry.

Association between Emotional Intelligence and Perceived Stress in Undergraduate Dental Students

Background: This study investigated the association of emotional intelligence (EI) and other factors with perceived stress (PS) in undergraduate dental students. Methods: A total of 234 undergraduate dental students at the School of Dental Sciences, Universiti Sains Malaysia (USM), in the academic year of 2009/2010, participated in this crosssectional study. Self-administered questionnaires, the Assessing Emotions Scale and the Perceived Stress Scale (PSS-10), were used to evaluate EI and PS, respectively. Results: The mean EI score was 121.2 (SD 11.85). The scores were significantly higher in females than males, and in students who chose dentistry based on their own interest rather than in those who were motivated by others to study dentistry. The mean PSS-10 score was 21.2 (SD 5.08). Pearson correlation analysis indicated a significant inverse relationship between EI and PSS-10 scores (r = -0.337). Multi-variable regression analysis also indicated a significant negative linear association between EI and PSS-10 scores (b = -0.156, 95% CI: -0.207, -0.104). PSS-10 scores were significantly higher for students who were in the clinical years rather than the preclinical years. Conclusions: This study of USM undergraduate dental students shows that a low EI, female sex, and being in the clinical years were significant predictors of PS.

A survey on light intensity outputs of QTH, cabled and cordless LED light curing units

Light intensity output is one of the determinants for adequate curing of visible light-cured materials. The aim of this survey was to evaluate the light intensity outputs (LIOs) of light curing units (LCUs) in dental clinics of Hospital Universiti Sains Malaysia (HUSM) and School of Dental Sciences, Universiti Sains Malaysia (USM). The respective LIOs of all functioning Quartz Tungsten Halogen (QTH) and Light Emitting Diode (LED) LCUs were tested using two light radiometers. For cordless LED LCUs, the testing procedure was done in situ and after being fully charged. Statistical analysis using Kruskal Wallis and Wilcoxon signed ranks tests were performed to compare the LIOs between groups and between the LIOs of in situ and post-charged cordless LED LCUs, respectively. The level of significance was set at 0.05 (p<0.05). The results revealed that 72.72%, 42.47% and 92% of QTH, cabled LED and cordless LED LCUs exhibited acceptable LIOs, respectively. Data analysis using Kruskal Wallis test showed a statistically significant difference between groups (p<0.05). The intergroup comparisons using multiple Mann Whitney test with Bonferroni correction revealed a significant difference between the LIOs of cordless LED and both QTH and cabled LED (p<0.017). The difference between the LIOs of in situ and post charged cordless LED LCUs was also significant (p<0.05). In conclusion, both QTH and cordless LED LCUs performed better in term of LIOs than cabled LED LCUs. Periodic testing of LCUs is essential to ensure optimal performance.

Effect of home bleaching agents on the hardness and surface roughness of resin composites

Ten percent carbamide peroxide is an effective, safe home bleaching agent. Higher concentrations are more effective, but there are mixed reports on their hardness and surface roughness effects on resin composites. To evaluate the effect of home bleaching agents; Opalescence Now 10% carbamide peroxide (Ultradent Products, USA) and Perfect Bleach 17% carbamide peroxide (Voco, Germany) on the surface hardness of microhybrid resin composites; Filtek Z250 (3M ESPE, USA) and Point 4 (Kerr, USA) and their surface roughness of selected treatment. Thirty specimens were prepared using acrylic moulds (4mm diameter x 2mm thick). N=5 controls placed in distilled water for 14 days. N=5 treated with Opalescence, and n=5 treated with Perfect Bleach for 2 hours every day for 14 days. Surface hardness was tested using Vickers hardness tester FV-7 (Future Tech Corp, Japan). Data analyzed with Mann-Whitney test with (P<0.05) considered significant. One specimen from 10% carbamide peroxide group was randomly selected for surface roughness, (Ra) evaluation using Atomic Force Microscopy (Ambios Technology, California, USA). All tested materials showed no significant changes in surface hardness after 14 days bleaching with 10% and 17% carbamide peroxide. However, AFM evaluation revealed an increase in Ra in both composites with 10% carbamide peroxide. Fourteen days bleaching using 10% and 17% carbamide peroxide did not have different effect on the surface hardness of Point 4 and Filtek Z250. The Ra increased after bleaching in both composites. The AFM surface roughness evaluation observed in 3D images shows to be a promising technique.

Genotoxicity assessment of locally produced dental nanocomposite using Comet assay

The aim of this study was to determine the genotoxicity of a locally produced nanocomposite by Universiti Sains Malaysia, Malaysia using Comet assay. Stem cells from human exfoliated deciduous teeth (SHED) were treated with the nanocomposite at five different concentrations (0.006, 0.0125, 0.025, 0.05, and 0.1 mg/ml) along with concurrent negative (medium alone) and positive control (zinc sulfate heptahydrate) and incubated at 37°C for 24 hours in an incubator at 5% CO2. The tail moment was used to assess the extent of DNA damage. The tail moment for the group of SHED treated with nanocomposite (for all the five different concentrations) was not statistically significant as compared to the negative control, suggesting that the locally produced dental nanocomposite did not induce any DNA damage. Hence, it can be concluded that the locally produced nanocomposite is non-genotoxic on stem cells from human exfoliated deciduous teeth.