Journal of Dental School

Objective: 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.

Methods: 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.

Results: 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.

Objective: 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.

Methods: 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.

Results: 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).

Conclusion: 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.

Objective: 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.

Methods: 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.

Results: 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).