Journal of Dental School
Volume:31 Issue: 2, 2013

Resistance to fracture is a critical issue when it comes to tooth restoration. The purpose of this study was to evaluate the fracture resistance of pulpotomized primary molars restored with glass ionomer (GI), amalgam and composite resin with and without cusp reduction. In this in-vitro experimental study, 60 extracted primary teeth were randomly divided into 6 groups of 10. In all groups except for the control group, conventional pulpotomy and MOD cavity preparation were performed in a way that the cavity isthmus width was equal to two-third of the inter cuspal distance. Group 1 teeth were restored with Kerr amalgam and underwent 1.5 mm cusp reduction, group 2 received Z250 composite resin onlay with 1.5 mm cuspal coverage, group 3 was restored similar to group 2 but without cusp reduction, group 4 was restored as group 3 but with Quixfil composite and group 5 was restored just like the former two groups but with GI. The restored teeth underwent thermocycling and were subjected to Universal Testing Machine with a crosshead speed of 0.5 mm/min. The recorded fracture resistance of specimens was compared. One-way ANOVA was used for statistical analysis. The mean fracture resistance was 2001.929 in the control group, 904.749 in the amalgam group, 1101.736 in Z250 composite with no cusp reduction group, 1036.185 in the Quixfil composite with no cusp reduction, 945.096 in the Z250 composite with cusp reduction and 850.313 in the GI group. The difference between the control group and other understudy groups was statistically significant (P<0.0001) but other differences were not statistically meaningful. Although in none of the groups the fracture strength was equal to that of intact primary teeth, the obtained values were within the normal range of masticatory forces.

Oral iron drops are recommended for children aged 6-24 months to prevent iron-deficiency anemia. However, their use is associated with the potential risk of erosion and microhardness reduction of primary teeth enamel due to their high acidity. It seems that the combination of silicone oil, nano-hydroxyapatite and chitosan powder may be able to improve the microhardness and surface structure of primary teeth enamel. This study sought to assess the effect of silicone oil plus nano-hydroxyapatite/chitosan on the changed microhardness and surface structure of primary teeth enamel after exposure to iron drop. In this in-vitro study, 30 anterior deciduous teeth were collected and randomly divided into 3 groups. In the first group, samples were exposed to iron drop for 5min and then treated with nano-hydroxyapatite/chitosan and silicone oil for 10min. In the second group, specimens were first treated with the mentioned compound and then exposed to iron drop. Microhardness changes were compared in each group using Wilcoxon one sample or Sign test and between the two groups using Mann Whitney U test. The third group specimens were observed with a scanning electron microscope (SEM) to assess their surface texture and quality. In the first group, iron drop exposure decreased enamel microhardness by 44% of the baseline value (P<0.001). Application of the understudy compound after iron drop exposure significantly increased enamel microhardness by 3% of the baseline value (P=0.006). Use of the mentioned compound before iron drop exposure significantly increased enamel microhardness by 2% of the baseline value (P=0.023). No statistically significant difference was found between the two groups (P=0.74). Iron drop exposure significantly decreased enamel microhardness. Use of silicone oil and nano-hydroxyapatite/chitosan powder caused 3% and 2% increase in enamel microhardness in the first and 2nd group, respectively. These values, compared to the effect of iron drop exposure are clinically significant.

Root canal obturation is an important step in endodontic therapy aiming at achieving a complete three-dimensional seal of the canal and preventing microleakage, reentry or growth of microorganisms in the root canal system. Several techniques and materials are available for root canal filling. Achieving an apical seal is among the most important characteristics of filling materials. This study aimed to compare apical microleakage of three different canal obturation techniques of Thermafil/Adseal, lateral condensation with gutta percha/Adseal and lateral condensation with Resilon/Epiphany using dye penetration method. This experimental study was conducted on 51 anterior single-rooted human teeth. The teeth were sterilized, the crowns were cut and canals were prepared using the crown-down technique. The teeth were randomly divided into 3 groups of 15 each for the three techniques and 6 teeth were assigned to positive and negative control groups. The first group roots were filled with Thermafil/Adseal, the second group received gutta percha/Adseal with lateral condensation technique and group 3 teeth roots were filled with Resilon/Epiphany using lateral condensation technique. Microleakage was measured using dye penetration technique. Data were statistically analyzed using ANOVA. Gutta percha/Adseal had the lowest (6.46±4.27 mm) and Resilon/Epiphany had the highest (13.47±3.03 mm) apical microleakage. Thermafil/Adseal showed higher mean apical microleakage than gutta percha/Adseal (8.43±4.49 mm). Statistical analysis revealed significant differences in apical microleakage among the three groups (P=0.0001). The results showed that gutta percha/Adseal had the lowest and Resilon/Epiphany had the highest mean apical microleakage. The microleakage of Thermafil/Adseal ranked second.

Pain control in dentistry especially endodontics is particularly important. Endodontic pain following root canal therapy (RCT) of vital teeth is closely correlated with inflammatory reactions. Increased level of prostaglandins has been reported in acute inflammatory reactions. Thus, cyclooxygenase-inhibiting drugs have a significant effect on reducing pain and inflammation. COX enzyme has two isoforms of COX-1 and COX-2. The conventional anti-inflammatory drugs inhibit both isoforms. In the recent years, COX-2 specific inhibitors have been the subject of extensive investigations. These inhibitors block the pain-inducing inflammatory mediators that are mostly derived from COX-2. The aim of this study was to compare the efficacy of prophylactic Celecoxib and a placebo in reducing post-endodontic pain using Visual Analog Scale (VAS). This double blind clinical trial was conducted on 30 patients with a mean age of 18 to 57 yrs. complaining of severe pain based on VAS. The subjects were randomly assigned to two groups of 400mg Celecoxib and the placebo. Drugs were administered 30 min prior to root canal therapy. Patients were asked to keep a pain diary and mark their degree of pain on a VAS chart before the initiation of treatment, immediately after treatment and at 4, 8, 12, 24 and 48 hours post-treatment. No significant difference was found between the analgesic effects of prophylactic Celecoxib and the placebo in any of the understudy time points (P>0.05). Considering the absence of a significant difference between the two groups, prophylactic Celecoxib is not recommended for post-endodontic pain reduction especially in cases with gastrointestinal (GI) problems.

Previous studies have demonstrated that dental stone casts can be disinfected by replacing 10v% of required water with 5.25% sodium hypochlorite solution. This comparative study evaluated physical properties of dental stone models produced by replacing distilled water with sodium hypochlorite. In this in-vitro experimental study, a total of 45 dental stone models were produced in the following 3 groups. Group A included stone models fabricated by mixing 300g gypsum powder and 94 mm3 distilled water. Group B comprised of stone models produced by mixing 300 g gypsum powder and 94 mm3 diluted 0.5% sodium hypochlorite solution. The third group (C) included specimens produced by mixing 300 g gypsum powder and 90 mm3 distilled water. Setting time, setting expansion and compressive strength of specimens were measured and compared. All tests were carried out according to ADA Specification No.25. Obtained results were entered SPSS software. ANOVA was applied for the comparison of 3 groups and Tukey’s test was used for pair wise comparison. Replacing distilled water with sodium hypochlorite caused a statistically significant reduction in setting time (mean reduction of 515 s) and increased the compressive strength of samples (mean increase of 4.06 MPa). Setting time in group 2 specimens was shorter than that in group 3 samples but no statistically significant difference was noted in setting expansion of samples in the 3 groups. Replacement of distilled water with sodium hypochlorite had no adverse effect on setting time, setting expansion or compressive strength of dental stone casts and thus can be used as a suitable method for disinfection of casts in dental laboratories.

Surface coating of dental mirrors using nanotechnology has been done to render them self-cleaning properties. Nano-scaled titanium dioxide particles (TiO2)show antimicrobial properties when exposed to ultra-violet (UV) light. The aim of this study was to evaluate the effect of surface coating of dental mirrors with nano titanium dioxide on their self-cleaning (from dentists’ perspective) and antibacterial properties against Streptococcus mutans and Staphylococcus aureus. In this laboratory study, nanostructured titanium dioxide films were used for surface coating of half the understudy dental mirrors using sol-gel dip coating technique. To assess the self-cleaning property, 45 conventional and 45 nano TiO2 coated mirrors were coded. The two types of dental mirrors were compared by dentists during cavity preparation with a high speed hand piece and the related questionnaire was filled out. The opinions of 9 clinicians each comparing the dental mirrors on 5 patients were collected. For antimicrobial testing, a 0.5 McFarland standard of microbial suspension and 100 times dilution of the solution were prepared of the two understudy microorganisms; 50 μldrop of each dilute was transferred to the center of each dental mirror in the two groups. Dental mirrors were exposed to UV light for 30, 60, 90 and 120 min (3 mirrors in each group for each time period) and then immersed in 5ml of distilled water. Next, 50μl of the mentioned solution was cultured on blood agar culture medium. Number of colonies was counted after 24h. T-test with a significance level of 0.01 was used for microbial evaluation. Normal distribution tests (NPAR tests) were used for the assessment of improved vision and Friedman test was applied for comparison of the two groups. No statistically significant difference was found between the two groups in terms of antibacterial properties against S. mutans and S. aureus (P>0.05). No significant difference existed between the two types of mirrors in terms of clinical vision improvement from the dentists’ perspectives (P>0.05). Nano TiO2 coated mirrors did not have any superiority over the conventional types in terms of self-cleaning or antimicrobial properties.