Abstract
The aim of this study was to investigate whether experimental and commercial dental restorative materials with functional fillers can exert a protective anti-demineralizing effect on enamel that is not immediately adjacent to the restoration. Four experimental resin composites with bioactive glass and three commercial restorative materials were investigated. Enamel blocks were incubated in a lactic acid solution (pH = 4.0) at a standardized distance (5 mm) from cured specimens of restorative materials. The lactic acid solution was replenished every 4 days up to a total of 32 days. Surfaces of enamel blocks were periodically evaluated by Knoop microhardness measurements and scanning electron microscopy. The protective effect of restorative materials against acid was identified as enamel microhardness remaining unchanged for a certain number of 4-day acid addition cycles. Additionally, the pH of the immersion medium was measured. While enamel microhardness in the control group was maintained for 1 acid addition cycle (4 days), restorative materials postponed enamel softening for 2–5 cycles (8–20 days). The materials capable of exerting a stronger alkalizing effect provided longer-lasting enamel protection. The protective and alkalizing effects of experimental composites improved with higher amounts of bioactive glass and were better for conventional bioactive glass 45S5 compared to a fluoride-containing bioactive glass. Scanning electron micrographs evidenced the protective effect of restorative materials by showing a delayed appearance of an etching pattern on the enamel surface. A remotely-acting anti-demineralizing protective effect on enamel was identified in experimental composites functionalized with two types of bioactive glass, as well as in three commercial ion-releasing restorative materials.
Highlights
The aim of this study was to investigate whether experimental and commercial dental restorative materials with functional fillers can exert a protective anti-demineralizing effect on enamel that is not immediately adjacent to the restoration
To investigate whether the protective effect of bioactive glasses (BGs)-functionalized composites can extend beyond the dental hard tissues immediately adjacent to the m aterial[22], the present in vitro study used enamel blocks incubated in a lactic acid solution at a standardized distance from cured specimens of restorative materials
This study showed that restorative materials with functional fillers exert an anti-demineralizing effect when incubated with enamel blocks in an acid solution
Summary
The aim of this study was to investigate whether experimental and commercial dental restorative materials with functional fillers can exert a protective anti-demineralizing effect on enamel that is not immediately adjacent to the restoration. The release of remineralizing ions and the increase of the solution pH can be employed to protect dental hard tissues against demineralization caused by bacterial acids Such a protective effect has been demonstrated in experimental BGfunctionalized composites intended for use as orthodontic adhesives; these materials showed the potential for protecting enamel adjacent to bonded brackets against the formation of white s pots[17,18,19,20,21]. To investigate whether the protective effect of BG-functionalized composites can extend beyond the dental hard tissues immediately adjacent to the m aterial[22], the present in vitro study used enamel blocks incubated in a lactic acid solution at a standardized distance from cured specimens of restorative materials. The null hypotheses were that the evaluated parameters (enamel MH, enamel surface morphology, and pH of the immersion solution) would: (1) remain unchanged during the simulated acid attack; and (2) not differ among the investigated restorative materials
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