Influence of nanogel additive hydrophilicity on dental adhesive mechanical performance and dentin bonding

Abstract

Objective To assess the influence of hydrophilicity of reactive nanogels on the mechanical performance of dental adhesives and microtensile bond strength (μTBS) to dentin after 24 h or 3 months of aging. Methods A series of three nanogels were synthesized: NG1—IBMA/UDMA; NG2—HEMA/BisGMA; NG3—HEMA/TE-EGDMA. The nanogels were dispersed in solvent, HEMA or BisGMA/HEMA. The degree of conversion (DC) of the materials was measured and the flexural modulus of these polymers was evaluated in dry or wet conditions. For μTBS analysis, a model adhesive was used without nanogel (control) or with the incorporation of nanogels. μTBS was evaluated after storage in distilled water for 24h or 3 months. The analysis of the fracture was performed after μTBS testing. Data were analyzed using ANOVA and Tukey’s test (α = 0.05). Results Water significantly increased the modulus of NG1 and NG2 dispersed in solvent, while significantly decreased the stiffness of NG3. All polymers dispersed in HEMA and Bis-GMA/HEMA had significantly lower modulus when stored in water. NG2 showed the highest DC in solvent and BisGMA/HEMA. In HEMA, NG1 and NG3 produced the highest DC. After three months, NG2 showed the best μTBS. The μTBS of NG2-containing adhesive resin significantly increased after 3 months, while storage had no effect in the control group, NG1 and NG3. Significance The more hydrophobic IBMA/UDMA nanogel showed higher bulk material mechanical property results, but the best dentin bond strength values, and notably strength values that improved upon storage, were obtained with the amphiphilic nanogel based on BisGMA/HEMA.

Review of nano‐technology applications in resin‐based restorative materials

“…It also provides significantly higher bond strength to dentin and stable mechanical properties (flexural modulus and flexural strength) up to 7 days water‐storage 53 . However, the level of hydrophilicity of the nanogel affects not only its mechanical performance but also dentin bond strength and stability of the restorative material over time, but improved results have been reported when nanogels developed with an amphiphilic behavior were investigated 144 …”

Biomaterials for dental composite applications: A comprehensive review of physical, chemical, mechanical, thermal, tribological, and biological properties

“…Gotti et al 92 formulated the effect of hydrophobicity on the mechanical property of dental adhesive. Three different nanogel was employed in this study.…”

Sorption, solubility and cytotoxicity of novel antibacterial nanofilled dental adhesive resins

“…The clinical manifestation of these factors are materials with short service lives (5.7 years) 16 , higher incidences of secondary caries and higher oral health-care costs 17 . In addition, the utilization of hydrophilic monomers in dental adhesives has been shown to adversely affect the water sorption and solubility properties of these types of dental biomaterials 18 – 21 , and to result in the attainment of a semi-permeable hybrid layer susceptible to slow processes of hydrolytic degradation. Such high permeability facilitates the absorption of water (via diffusion 9 and capillarity 20 ), promotes the formation of water trees (a 3-dimensional network of interconnecting pores), and results in polymeric matrixes that are expanded and plasticized, and the leaching of unreacted hydrophilic monomers (such as TEGDMA, HEMA, bis-GMA, UDMA, etc.).…”

“…Previous studies have shown that titanium dioxide nanoparticles (n-TiO 2 ) may be successfully incorporated into commercially available polymer compositions as a promising strategy to improve the properties (antibacterial and bioactivity) of dental adhesive resins 18,27 . These metaloxide nanoparticles display excellent mechanical properties (high elastic modulus and hardness), are hydrolysis resistant, cost-effective and are capable of producing reactive oxygen species (ROS) when irradiated with UV.…”