ABSTRACT
INTRODUCTION: The objective of this study was to evaluate the physical properties, cytotoxicity and sealing ability of HealApex _a new premixed calcium-silicate-phosphate-based biosealer_ in comparison with AH-26. METHODS AND MATERIALS: Setting time, working time, film thickness, flow and radiopacity evaluation were performed according to ISO 6876 specification. L929 fibroblasts were incubated with the extracts of sealers and cytotoxicity was then evaluated using MTT assay. Thirty intact extracted human premolars were instrumented using step-back technique. The specimens were obturated with gutta-percha and experimental sealers employing lateral condensation technique. Sealing ability of sealers was investigated for up to one month using fluid filtration method. Data were statistically analyzed by t-test and ANOVA. RESULTS: Physical properties of both sealers conformed to ISO specification. AH-26 exhibited significantly higher flow, higher radiopacity and lower film thickness; whereas HealApex showed lower setting time (P<0.05). HealApex represented high cell viability (P<0.05); however, AH-26 demonstrated significantly lower cell viability compared with the negative control group (P<0.05). There was no significant difference in microleakage between the sealers after 1 and 7 days; however, after 30 days, HealApex displayed better sealing ability (P<0.05). CONCLUSIONS: In this in vitro study, HealApex revealed acceptable physical properties, biocompatibility and good sealing ability as an endodontic sealer. Obtained results showed the new sealer had acceptable physical properties and good biocompatibility. In short term, the sealing ability of HealApex was comparable with AH-26 whilst in long term, HealApex's sealing ability was better than the epoxy resin-based sealer.
ABSTRACT
BACKGROUND: The aim of this study was to assess the effect of cusp coverage and water storage on compressive strength of composite restorations. MATERIAL AND METHODS: This in vitro experimental study was conducted on 40 extracted human maxillary premolar teeth, which were randomly divided into four groups of 10. Mesio-occluso-distal (MOD) cavities were prepared in all teeth. The thickness of composite for cusp coverage was 1.5 mm in groups 1 and 3 and 2.5 mm in groups 2 and 4. Compressive strength (CS) was measured after 24 hours in groups 1 and 2 and after six months of water storage in groups 3 and 4. Two-way ANOVA was used to statistically analyze the data. RESULTS: The mean and standard error (SE) of compressive strength was 795.23 ± 35.18N in Group 1, 1232.52 ± 78.01N in Group 2, 617.18 ± 40.19N in Group 3 and 963.22 ± 50.05N in Group 4. CONCLUSIONS: Statistical analysis showed a significant difference in compressive strength measured after 24 hours (groups 1 and 3) and after six months of water storage (groups 2 and 4). The compressive strength of groups with 2.5 mm cusp coverage was significantly greater than that of groups with 1.5 mm cusp coverage. Key words:Fracture strength, cusp coverage, water absorption, composite resin, compressive strength.
ABSTRACT
AIM: The aim was to evaluate the effect of sugar-free chewing gum containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and xylitol on salivary Streptococcus mutans. MATERIALS AND METHODS: A total of 60 dental students of 20-25 years old, who volunteered after checking their health condition and signing an informed consent, were randomly allocated to receive one of the following interventions: (A) Chewing gum containing CPP-ACP; (B) containing xylitol. Subjects within the experimental groups were taken the gums 3 times daily, after each meal for a period of 3 weeks. Pre- and post-intervention unstimulated saliva samples were quantified for S. mutans counts. RESULTS: A statistically significant reduction of salivary S. mutans was displayed in both groups A and B after the intervention when compared with baseline (P < 0.001), and group A shows more statistically significant reduction of salivary S. mutans than group B (P = 0.011). CONCLUSION: Daily consumption of chewing gum containing CPP-ACP and xylitol significantly reduces the level of salivary S. mutans, but chewing gum containing CPP-ACP can reduce the level of salivary S. mutans in more than xylitol chewing gum.
ABSTRACT
The level of natural radiation in some regions of Ramsar, a northern coastal city of Iran, is known to be among the highest levels of natural radiation in the world. 226Ra existing in high concentrations in the soil of this region is washed by underground water and transferred to the surface. In this way, 226Ra enters the food chain of residents and substitutes within the hard body tissues of humans. 226Ra is one of the so-called bone seekers as its metabolic processes in the human body are similar to calcium and remains in hard tissues of body because of its long half-life, and being an alpha emitter causes dangerous effects on human health. The purpose of this study is to determine the concentration of 226Ra in the teeth of residents of these high-level natural radiation areas, compared with a control group. Thirteen teeth in five groups were studied as the case group and thirteen teeth in five corresponding control groups were inspected. The mean values of the activity of 226Ra in the case group and in the control group were 0.32 and 0.18mBqg(-1), respectively.
