An-invitro comparison of Thermocycling Effect on Micro- hardness and Micro-tensil bond strength of Nano composite denture teeth

Abstract

Purpose: The purpose of this study was an evaluation of the effect of thermocycling on microhardness and microtensile bond strength (μTBS) of the cross-linked acrylic and nanocomposite teeth to the acrylic denture base. Materials and methods: twelve teeth of the upper denture teeth were selected. Six teeth of nano-hybrid composite resin denture teeth and six cross-linkedacrylic teeth. These teeth, together with theacrylic resin bases, have been fixed to a micro-sawing machine to form 120 microbeam samples. These samples were divided into two storage regimes (dry and thermocycler), forming eight groups, each group containing 15 beams. These 8 groups were divided in equal parts to test the micro-hardness and strength of the micro-tensile bond (4 groups for each test). Results: Paired t-test was used to analyze the effect of aging on micro-hardness and microtensile bond strength for both types of denture teeth. The tests were considered significant when p ≤ 0.05 and highly significant when p ≤ 0.001. Thermocycling procedure decrease the mean values in micro-tensile bond strength for both types of denture teeth brands but with statistical significant difference regarding the cross-linked acrylic one. it produces highly significant decrease in mean values for cross-linked acrylic but has nearly no effect on nanocomposit teeth regarding the microhardness test. Considering denture teeth brand Cross linked acrylic denture teeth showing higher mean values in micro-tensile bond strength before and after aging. Also, it was showing higher mean values in micro-hardness before thermocycling. This condition was totally reversed after aging as nano composite teeth showing higher mean values with significant difference in relation to acrylic one. Conclusion: The newly introduced nanohybrid composite denture teethwere less markedly affected by thermocycling specially in term of hardness,but practically and from financial point of view, the cross-linked acrylic resin teeth has a comparable result to nanocompsite one as it shows higher micro-tensile bond strength (μTBS) so, it appears more applicable for patients.

<p>Assessing Tensile Bond Strength Between Denture Teeth and Nano-Zirconia Impregnated PMMA Denture Base</p>

“…Studies have shown that bond strength between acrylic teeth and denture base resins could be affected by aging processes such as thermocycling procedure, which could decrease the overall bond strength. 40 , 41 Baia et al 42 concluded that prolonged bleaching either post- and pre-restoration using 4% hydrogen peroxide decreased tooth bonding. However, in another study, decreased bond strength was found in teeth bonded to CAD/CAM and 3D printed denture base resins, when compared to the heat cured acrylic resin, with no significant influence following aging.…”