Nanocomposite containing CaF2 nanoparticles: Thermal cycling, wear and long-term water-aging

Abstract

Objectives Fluoride (F) releasing dental restoratives are promising to promote remineralization and combat caries. The objectives of this study were to develop nanocomposite containing calcium fluoride nanoparticles (nCaF2), and to investigate the long-term mechanical durability including wear, thermal-cycling and long-term water-aging behavior. Methods Two types of fillers were used: nCaF2 with a diameter of 53 nm, and glass particles of 1.4 μm. Four composites were fabricated with fillers of: (1) 0% nCaF2 + 65% glass; (2) 10% nCaF2 + 55% glass; (3) 20% nCaF2 + 45% glass; (4) 30% nCaF2 + 35% glass. Three commercial materials were also tested. Specimens were subjected to thermal-cycling between 5 °C and 60 °C for 105 cycles, three-body wear for 4×105 cycles, and water-aging for 2 years. Results After thermal-cycling, the nCaF2 nanocomposites had flexural strengths in the range of 100-150 MPa, five times higher than the 20-30 MPa for resin-modified glass ionomer (RMGI). The wear scar depth showed an increasing trend with increasing nCaF2 filler level. Wear of nCaF2 nanocomposites was within the range of wear for commercial controls. Water-aging decreased the strength of all materials. At 2 years, flexural strength was 94 MPa for nanocomposite with 10% nCaF2, 60 MPa with 20% nCaF2, and 48 MPa with 30% nCaF2. They are 3-6 fold higher than the 15 MPa for RMGI (p < 0.05). SEM revealed air bubbles and cracks in a RMGI, while composite control and nCaF2 nanocomposites appeared dense and solid. Significance Combining nCaF2 with glass particles yielded nanocomposites with long-term mechanical properties that were comparable to those of a commercial composite with little F release, and much better than those of RMGI controls. These strong long-term properties, together with their F release being comparable to RMGI as previously reported, indicate that the nCaF2 nanocomposites are promising for load-bearing and caries-inhibiting restorations.

A systematic approach to standardize artificial aging of resin composite cements

“…For that reason, thermal cycling is usually performed between 5 and 55 • C with cycle times of 1 min [19][20][21]. The suggested duration of thermal cycling differs from 3000 to 100,000 cycles [22][23][24][25][26]. It is proposed that 10,000 cycles might represent 1 year of service [27,28].…”

Abrasive wear and surface roughness of contemporary dental composite resin

“…For example, new silorane monomers 1) and modified urethane (meth) acrylates such as TCD-urethane 2) that decrease polymerization shrinkage have been developed; filler refinement 3,4) using nanotechnology has been widely applied not only to reduce particle size, but also to increase filler volume to enhance polishing and wear resistance. Also special fillers that release fluoride have been introduced 5) . In addition, bulk fill composite restorations have been made possible with the development of new photoinitiators 6) (such as Tetric-N-Ceram Bulk Fill, Ivoclar Vivadent), and flowable composite resins that can be directly inserted through a cannula to easily line the base of cavities with complicated shapes have been introduced.…”

Nanotechnology in Dentistry

“…Comparing the fluoride release from a conventional glass ionomer cement and from a fluoride nanoparticle, Neelakantan et al 25 observed a higher release for the conventional ionomer on the first three days, but a maximum release. Since fluoridereleasing dental restoratives are promising to promote remineralisation and to combat caries, Weir et al 26 developed nanocomposites containing calcium fluoride nanoparticles (nCaF 2 ) and investigated their long-term mechanical durability including wear, thermal-cycling and long-term water-aging behavior. Combining nCaF 2 with glass particles yielded nanocomposites with long-term mechanical properties and with little fluoride release, indicating that the nCaF 2 nanocomposites are promising for load-bearing and caries-inhibiting restorations.…”