Evaluation of mechanical properties and bond strength to chitosan cross linked dentin : (in vitro) /

Abstract

The survivability of the tooth after the root canal treatment is also important to keep its functionality without breakage and remains intact. The root canal treatment may alter the physical and mechanical properties of the dentin which make the dentin more susceptible to fracture. The complete disinfection for the canals, the gutta-percha cone fitting to the apical constriction, the type of sealer used and the pretreatment of dentin prior for sealer bonding affects the quality of the apical sealing. The goal for the dentin pretreatment is the removal of the smear layer which blocks the dentinal tubules and affects the sealer infiltration and flow and sealer bond strength The various irrigants in root canal treatment affects the radicular dentin, thus compromises the sealing ability and mechanical properties. smear layer removal greatly enhances the irrigant flow, sealer infiltration and bond strength. Chitosan nanoparticles have the same chelation effect as EDTA when used as final rinse. Also, the increase in the chitosan application time improves the apical seal and bond strength. In contrary to EDTA which causes dentin erosion upon the prolonged application time Chitosan nanoparticles are a semi-synthetic molecule derived from amino-polysaccharide and produced by the partial acetylation of chitin. It‟s a biodegradable, biocompatible, bio-adhesive, strong antibacterial and non-toxic and it was believed that it improves the microhardness and sealer bond strength. Vickers test is a test used for assessment of the mechanical properties as it‟s a pyramidal diamond intender with angle 136° that form a square intender on a microhardness testing machine producing indentations on the dentin away from the pulp space and re-evaluated on an analogue image of the specimen of the pyramidal indentation as an impression on the root canal surface. The evaluation of the bond strength between the chitosan nanoparticles and cross-linked dentin can be addressed through the push out test. The push out test is performed using universal testing machine with 0.9 mm diameter with cold stainless-steel plunger facing the obturating material with crosshead speed with compressive load of 0.5 mm/min until bond failure occur. The bond strength is also evaluated through the interfacial permeability as it performed at the resin-dentin permeability with water pressure of 20-cm with usage of yellow fluorescent dye and checked in sectioned slices 36 Teeth were selected for this study. The Sample classification was divided into 2 groups, Group 1 of 18 tooth to evaluate microhardness while group 2 of 18 tooth to evaluate sealer bond strength. Group 1 contain 2 sub groups 9 tooth each, Group 1A where tooth was subjected to root canal treatment with sodium hypochlorite irrigation while group 1B was subjected to root canal treatment irrigated with sodium hypochlorite following by chitosan crosslinking then subjected to Vickers test . Group 2 contain 2 sub groups, group 2A was subjected to root canal treatment with sodium hypochlorite irrigation then obturated while group 2B was subjected to root canal treatment irrigated with sodium hypochlorite following by chitosan crosslinking then obturated and subjected to the push out test. The results of Vickers test was showed a significant effect on mean hardness, NaOCl 5.25% + 0.2% Chitosan showed the lowest hardness vales compared to NaOCl 5.25% at p=0.02. Different root sections showed insignificant effect on mean hardness on mean hardness (p=0.172). The interaction between both groups and root section was insignificant at p=0.735. For NaOCl 5.25% group, insignificant difference between root section at p=0.221. For NaOCl 5.25% + 0.2% Chitosan group, insignificant difference between root sections at p=0.557. For coronal root section, insignificant difference between tested groups at p=0.408. For middle root section, insignificant difference between tested groups at p=0.063. For apical root section, insignificant difference between tested groups at p=0.138. The results of the push out test showed insignificant effect on mean push out at p=0.960. Different root sections showed insignificant effect on mean push out on mean push out (p=0.664). The interaction between both groups and root section was insignificant at p=0.190. For NaOCl 5.25% group, insignificant difference between root section at p=0.640. For NaOCl 5.25% + 0.2% Chitosan group, insignificant difference between root sections at p=0.197. For coronal root section, insignificant difference between tested groups at p=0.162. For middle root section, insignificant difference between tested groups at p=0.882. For apical root section, insignificant difference between tested groups at p=0.239. It was concluded that using 0.2% chitosan nanoparticles on dentin didn‟t improve the microhardness but caused a significant microhardness reduction in comparison to other irrigants with chelation properties. 0.2% chitosan nanoparticles didn't improve the bond strength in comparison to 5.25% NaOCl. Chitosan nanoparticles is a promising chelation agent but needs a further research concerning concentration, time of application.