Novel self-healing dental resin with microcapsules of polymerizable triethylene glycol dimethacrylate and N,N-dihydroxyethyl-p-toluidine

Abstract

Objectives Bulk fracture is one of the primary reasons for resin-based dental restoration failures. To date, there has been no report on the use of polymerizable dental monomers with acceptable biocompatibility to develop a resin with substantial self-healing capability. The objectives of this study were to: (1) develop a self-healing resin containing microcapsules with triethylene glycol dimethacrylate (TEGDMA)-N,N-dihydroxyethyl-p-toluidine (DHEPT) healing liquid in poly(urea-formaldehyde) (PUF) shells for the first time, and (2) determine the physical and mechanical properties, self-healing efficiency, and fibroblast cytotoxicity. Methods Microcapsules of polymerizable TEGDMA-DHEPT in PUF were prepared via an in situ polymerization method. Microcapsules were added into a BisGMA-TEGDMA resin at microcapsule mass fractions of 0%, 5%, 10%, 15% and 20%. A flexural test was used to measure composite strength and elastic modulus. A single edge V-notched beam method was used to measure fracture toughness KIC and self-healing efficiency. Results Flexural strength and elastic modulus (mean ± sd; n = 6) of resin containing 5% to 15% microcapsules were similar to control without microcapsules (p > 0.1). Adding microcapsules into the resin increased the virgin KIC, which was about 40% higher at 15% microcapsules than that with 0% microcapsules (p < 0.05). Specimens were fractured and healed, then fractured again to measure the healed KIC. A self-healing efficiency of about 65% in KIC recovery was obtained with 10–20% microcapsules. All specimens with 0–20% microcapsules had fibroblast viability similar to control without resin eluents (p > 0.1). Significance Self-healing dental resin containing microcapsules with polymerizable TEGDMA-DHEPT healing liquid in PUF shells were prepared for the first time with excellent self-healing capability. These microcapsules and self-healing resins containing them may be promising for dental restorations to heal cracks/damage and increase durability.

Effects of water-aging on self-healing dental composite containing microcapsules

“…34,35 Briefly, DHEPT (Sigma-Aldrich, St. Louis, MO) at 1% (all mass fractions) was added to TEGDMA monomer (Esstech, Essington, PA). At room temperature, 50 mL of distilled water and 13 mL of a 2.5% aqueous solution of ethylene-maleic anhydride (EMA) copolymer (Sigma-Aldrich) were mixed in a 250 mL round-bottom glass flask.…”

“…34 The self-healing resin containing microcapsules had human fibroblast viability similar to control cells in culture medium without resin, indicating little cytotoxicity in vitro . 34 The composite containing these microcapsules achieved good self-healing efficacy. 35 However, in these pilot studies, the cured specimens were immersed in water for only 1 day before testing.…”

Using feedback control to actively regulate the healing rate of a self-healing process subjected to low cycle dynamic stress

“…The control law (27) assumes that 1/m is unavailable butφ is the estimate of φ [1/m] andφ =φ − φ. Also, ∆I(t) is bounded by ∆I(t) ≤ ρ and k * ≥ ρ/m min .…”

“…Other examples of healing agents enclosed in microcapsules are dicyclopentadiene [23], rapeseed oil [24] and fluorescent fluid [25]. Also, microcapsules containing a mixture of strontium fluoroaluminosilicate and polyacrylic acids [26] and another containing Triethylene glycol dimethacrylate-N and N-dihydroxyethyl-ptoluidine [27] were recorded in dental application. While toxic concerns have been raised with some microcapsule contents [28,29], the later is deemed safe for dental application [27].…”

“…Also, microcapsules containing a mixture of strontium fluoroaluminosilicate and polyacrylic acids [26] and another containing Triethylene glycol dimethacrylate-N and N-dihydroxyethyl-ptoluidine [27] were recorded in dental application. While toxic concerns have been raised with some microcapsule contents [28,29], the later is deemed safe for dental application [27]. It is expected that more functional applications will emerge particularly with the success in embedding microcapsules in a polyelectrolyte multilayer [30].…”