In-Vitro Investigation of the Fracture Strength of Pulpotomized Primary Molars Restored with Glass Ionomer, Amalgam and Composite Resin with and without Cusp Reduction

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.Conclusion: 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

Evaluation of Er,Cr:YSGG Laser Effect on Microshear Bond Strength of a Self-Adhesive Flowable Composite in the Dentin of Permanent Molar: An In Vitro Study

Aim and Background. Recently, new restorative materials such as self-adhesive flowable composites, because of their simple use and no need to bonding and etching, are considered important, particularly in pediatric dentistry. The aim of this study is to evaluate the effect of Er,Cr:YSGG laser on microshear bond strength of self-adhesive flowable composite on permanent teeth dentin in vitro. Material and Methods. In this experimental study, 40 dentin sections were prepared from healthy third molars and divided into two groups according to their surface preparation by Er,Cr:YSGG laser or without laser, only with silicon carbide paper. In each group, two groups of 10 teeth were treated with self-adhesive flowable composite (Dyad) and conventional flowable composite (acid etch and bonding). Samples were stored in normal saline and after 48 hours their bond strength was measured. The failure mode of samples was observed on stereomicroscope. In order to analyse the results, the one way ANOVA and Tukey’s test for multiple comparisons were used. Result. The maximum bond strength was related to conventional flowable composite with laser preparation group (24/21 Mpa). The lowest one was seen in Dyad composite without laser emitting (9/89 Mpa). The statistical difference between this two groups was significant (P value = 0/0038). The microshear bond strength differences between Dyad composite groups with laser preparation (mean = 16/427±1/79) and without laser preparation (mean = 12/85±1/90) were statistically significant too (P value = 0/01). Conclusion. Self-adhesive flowable composite has lower microshear bond strength than conventional flowable composite. Moreover, the laser irradiation as a surface treatment can improve this bond strength