Effect of co-precipitation plus spray-drying of nano-CaF2 on mechanical and fluoride properties of nanocomposite

Dent Mater. 2021 Jun;37(6):1009-1019. doi: 10.1016/j.dental.2021.03.020. Epub 2021 Apr 18.

Abstract

Objective: Fluoride (F)-releasing restoratives typically are either weak mechanically or release only low levels of F ions. The objectives of this study were to: (1) develop a novel photo-cured nanocomposite with strong mechanical properties and high levels of sustained F ion release via a two-step "co-precipitation + spray-drying" technique to synthesize CaF2 nanoparticles (nCaF2); and (2) investigate the effect of spray-drying treatment after co-precipitation of nCaF2 on mechanical properties and F ion release of composite.

Methods: Two types of CaF2 particles were synthesized: A co-precipitation method yielded CaF2cp; "co-precipitation + spray-drying" yielded nCaF2cpsd. Composites were fabricated with fillers of: (1) 0% CaF2 + 70% glass; (2) 10% CaF2cp + 60% glass; (3) 15% CaF2cp + 55% glass; (4) 20% CaF2cp + 50% glass; (5) 10% nCaF2cpsd + 60% glass; (6) 15% nCaF2cpsd + 55% glass; and (7) 20% nCaF2cpsd + 50% glass. A commercial F-releasing nanocomposite served as control.

Results: The nCaF2cpsd had much smaller particle size (median = 32 nm) and narrower distribution (22-57 nm) than CaF2cp (median = 5.25 μm, 162 nm-67 μm). The composite containing nCaF2cpsd had greater flowability, flexural strength, elastic modulus and hardness than CaF2cp composite and commercial control composite. At 84-day immersion in water, the nanocomposites containing 20% nCaF2cpsd had 65 times higher cumulative F release, and 77 times greater long-term F-release rate, than commercial control.

Conclusions: A novel two-step "co-precipitation + spray-drying" technique of synthesizing nCaF2 was developed. The photo-cured nanocomposite containing 20% nCaF2cpsd possessed strong mechanical properties and excellent long-term F-release ability, and hence is promising for dental restoration applications to inhibit secondary caries.

Keywords: Co-precipitation; Dental composite; Fluoride release; Mechanical properties; Nano-CaF(2); Spray-drying.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Composite Resins
  • Dental Caries*
  • Fluorides
  • Glass Ionomer Cements
  • Humans
  • Materials Testing
  • Nanocomposites*

Substances

  • Composite Resins
  • Glass Ionomer Cements
  • Fluorides