J. Nowak

Mechanical Properties of Calcium Fluoride-Based Composite Materials

Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM) and one commercially available flowable light-curing composite material (FA) that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA), unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties.

Influence of infiltration technique and selected demineralization methods on the roughness of demineralized enamel: An in vitro study

BACKGROUND The decalcification of enamel leads to an increase in tissue roughness. The development of carious lesions may be halted or these lesions may heal, which results in a smoother surface. OBJECTIVES The objective of the study was to assess the impact of selected agents on the roughness of demineralized enamel on the smooth surfaces of teeth. MATERIAL AND METHODS A total of 25 samples with exposed enamel surfaces were examined in the study. The samples were randomized into groups and they were exposed to a demineralizing solution, after which the following agents were applied: Icon (Ic), Elmex gel (El), GC Tooth Mousse (TM), Colgate Total (K+) - a positive control group, and distilled water as a negative control group (K-). The impact of selected agents on the roughness of demineralized enamel was assessed with a profilometer. The parameters Ra, Rz and Rq were analyzed. RESULTS Following infiltration and demineralization, the Ra coefficient declined in groups Ic, TM, K+ and K-, Rz decreased in groups Ic, TM and Rq was lower in groups Ic, TM and Kafter using agents when compared with demineralization. The lowest Ra, Rz and Rq values, i.e. the highest degree of surface smoothness, were observed in group Ic. An increase in all coefficients (Ra, Rz and Rq) was noted in group El. CONCLUSIONS Demineralized enamel can be smoothed out through the one-time application of Icon resin or the long-term application of GC Tooth Mousse. The least effective agents turned out to be those with a high fluoride content.

Dental Composites Based on Dimethacrylate Resins Reinforced by Nanoparticulate Silica

This paper describes morphological differences and associated functional properties of dental composites based on dimethacrylate resins reinforced by nanoparticulate silica filler modified according to different silanization procedures. Surface morphology of the materials was evaluated by means of AFM, while nanohardness and elasticity modulus of the surface layer - by nanoindentation and abrasion - gravimetrically. The effects of silane treatment of nanoparticulate silica surface on possible filler loading, mechanical properties and abrasion resistance of the composites were discussed. The influence of the amount and kind of silane coupling agent on the example of 3 -methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane were presented. The modification of nanoparticulate silica with 3 -methacryloxypropyltrimethoxysilane enabled the introduction of 15% more filler than modification with vinyltrimethoxysilane. The abrasion resistance depended strongly on the composite morphology and the micromechanical parameters of the surface layer. The composite modified with vinyltrimethoxysilane, containing the highest percentage of filler particles smaller than 1 μm in diameter, exhibited the lowest abrasion (0.3 vol.%). Abrasive wear seemed to be a linear function of nanoindentation hardness with the correlation coefficient of R2 = 0.96. The highest hardness of the surface layer of commercial composite (130 MPa) resulted in the highest abrasive wear (7.7 vol.%). The type and the quantity of silane coupling agent used for silica modification strongly influence the morphology and mechanical and tribological properties of the dental composites. The application of more than the calculated, optimal amount of silane to nanosilica modification enables higher filler loading, but the composites exhibit inferior mechanical characteristics. Nanoindentation hardness of surface layer showed to be the most useful parameter in estimation of material susceptibility to abrasion.