Development of novel self-healing and antibacterial dental composite containing calcium phosphate nanoparticles

Abstract

Objectives Fracture and secondary caries are the primary reasons for dental restoration failure. The objective of this study was to develop a self-healing composite to heal cracks, while containing dimethylaminohexadecyl methacrylate (DMAHDM) for antibacterial function and nanoparticles of amorphous calcium phosphate (NACP) for remineralization. Methods Microcapsules were synthesized with poly(urea-formaldehyde) (PUF) shells containing triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid. Composite contained 20 mass% of NACP and 35% glass fillers. In addition, composite contained 0%, 2.5%, 5%, 7.5%, or 10% of microcapsules. A single edge V-notched beam method measured fracture toughness (KIC) and self-healing efficiency. A dental plaque microcosm biofilm model was used to test the antibacterial properties. Results Incorporation of microcapsules up to 7.5% into the composite did not adversely affect the mechanical properties (p > 0.1). Successful self-healing was achieved, with KIC recovery of 65–81% (mean ± sd; n = 6) to regain the load-bearing capability after composite fracture. The self-healing DMAHDM-NACP composite displayed a strong antibacterial potency, inhibiting biofilm viability and lactic acid production, and reducing colony-forming units by 3–4 orders of magnitude, compared to control composite without DMAHDM. Conclusions A dental composite was developed with triple benefits of self-healing after fracture, antibacterial activity, and remineralization capability for the first time. Clinical significance The self-healing, antibacterial and remineralizing composite may be promising for tooth cavity restorations to combat bulk fracture and secondary caries. The method of using triple agents (self-healing microcapsules, DMAHDM, and NACP) may have wide applicability to other dental composites, adhesives, sealants and cements.

Design and development of self-healing dental composites

“…The super-large microcapsules become “weak spots” that compromise the mechanical performance of the SHDCs. [33, 42, 43] This is consistent with the healing material developed using the monomer-catalyst model, [21] where the increase of microcapsule loading was a tradeoff of mechanical performance for improved healing.…”

“…For calculating healing efficiency, a method used in the UIUC models was adopted. [21, 44] This method involves stressing the sample with a load that induces internal fracturing, allowing it to rest for several days, and then measuring the new peak load after healing. Specimens that were V-notched did not break into two pieces at the peak load because the crack growth was stopped to keep the two halves slightly connected.…”

“…If left untreated, this fatal deterioration leads to catastrophic failure of restorations, and hence significantly shortens the duration of their service lives. [8] Progress was made to repair cracks in dental resins with use of the monomer-catalyst self-healing model, [21–23] but concerns were raised regarding the potential toxicity of the monomers and the price of the Grubbs catalyst. Also, polyurethane microcapsules are easily fractured when being mixed with silica particles due to the big contrast in their physical strengths.…”

Biocompatibility and antibacterial activity of nitrogen-doped titanium dioxide nanoparticles for use in dental resin formulations

“…Recently, an antibacterial composite was developed that also had self-healing and remineralization properties using calcium phosphate nanoparticles. 16 Another self-healing composite material was developed using breakable capsules of unreacted monomers, which has shown promising healing characteristics. 17 Recent research has shown that the light absorption of TiO 2 can be shifted to the visible range by doping with a variety of atoms, including nitrogen, [18][19][20][21] fluorine, 22 copper, 23 and silver, 24 resulting in a new class of visible light active materials.…”

Biological evaluation of subgingivally placed direct resin composite materials

“…Recent studies have reported technological improvements in composite resin. Of particular interest are antibacterial additives that might reduce secondary caries and biofilms and enhance remineralization of teeth (29)(30)(31). Thus, material-induced reactions should be expected when margins beyond the CEJ are required.…”