Quantitative Assessment of the Efficacy of Amorphous Calcium Phosphate/Methacrylate Composites in Remineralizing Caries-like Lesions Artificially Produced in Bovine Enamel

Abstract

Recent studies show that methacrylate-based composites with amorphous calcium phosphate (ACP) as a filler can release supersaturating levels of calcium and phosphate ions in proportions favorable for apatite formation. These findings suggest that such composites could be effectively used as coatings for remineralizing teeth damaged by tooth decay. To examine this hypothesis, we tested composites in vitro for their efficacy to remineralize artificially formed caries-like lesions in extracted bovine incisors. Single 120-microns-thick sagittal tooth sections were placed in holders that exposed only the carious enamel surface. The exposed surfaces were coated with a 1-mm- to 1.5-mm-thick layer of the composite containing, by mass, 40% apatite, silica, or P2O7(-4)-stabilized ACP and 60% photoactivated resin comprised of Bis-GMA, TEGDMA, HEMA, and ZrM. The photocured composite-coated sections were immersed either in a remineralizing solution for 4 weeks at 37 degrees C (static model) or cyclically immersed in demineralizing (0.5 h) and remineralizing solutions (11.5 h) for 2 weeks (dynamic model). Quantitative digital image analysis of matched 102 microns x 220 microns areas from contact microradiographs taken of the sections before and after immersion showed that lesions coated with ACP-filled composites fractionally recovered 71% +/- 33% of their lost mineral compared with 14% +/- 13% for apatite controls in the static model and 38% +/- 16% compared with -6% +/- 24% in the dynamic model. The results suggest that sealants based on ACP-filled methacrylate composites have the potential to remineralize carious enamel lesions.

Nanocomposites with Ca and PO4 release: Effects of reinforcement, dicalcium phosphate particle size and silanization☆

“…Therefore, for stress-bearing restorations, it would be desirable to use a composite with a DCPA:whisker ratio near 1:1 using unsilanized DCPA nano-particles, which produced a Ca concentration of 0.35 mmol/L and PO 4 of 0.99 mmol/L (at 56 d). These concentrations matched or exceeded the reported Ca and PO 4 concentrations measured using a similar method for previous calcium phosphate composites known to remineralize enamel and dentin lesions in vitro [18][19][20][21]. For example, amorphous calcium phosphate (ACP) composites yielded a Ca concentration of 0.3 mmol/L to 1.0 mmol/L, and a PO 4 concentration of 0.2 mmol/L to 0.7 mmol/L (Figs.…”

“…Previous studies [18][19][20][21] showed that when the Ca and PO 4 ions were released from the composite restoration, they reprecipitated to form hydroxyapatite outside the composite and inside the tooth lesions, significantly increasing the mineral content of the lesion. The fact that the Ca and PO 4 concentrations from the DCPA-whisker composite matched or exceeded those of the previous calcium phosphate composites suggests that the DCPA-whisker composite may also be an effective remineralizer.…”

“…Hence there is a wide range of solution conditions when the precipitation of hydroxyapatite occurs spontaneously. Indeed, several bioactive composites have been developed that release calcium and phosphate ions in the presence of an aqueous solution, which then precipitate to form hydroxyapatite [18][19][20][21]. The calcium ions are conveniently referred to as Ca, and the phosphate ions as PO 4 , following previous studies [20,21].…”

Effect of resin infiltration on enamel surface properties and <i>Streptococcus mutans</i> adhesion to artificial enamel lesions

“…ACP-containing bioactive materials stimulate mineral growth by increasing calcium and phosphate concentrations within the lesion, especially in the acidic oral environment, to levels that exceed those existing in ambient oral fluids. This shifts the thermodynamic driving force toward apatite formation 11,12) . ACP can also sustain these supersaturation conditions, which are favorable for apatite formation, over extended periods of time 11,12) .…”

Bond Strength of an Amorphous Calcium Phosphate–Containing Orthodontic Adhesive

“…ACP-filled composite resins have been shown to recover 71% of the lost mineral content of decalcified teeth. 4 One ACP-containing adhesive, Aegis Ortho (The Bosworth Co, Skokie, Ill), has been marketed for use as a lightcured orthodontic adhesive with similar properties to previously used resins. The premise behind this product is that during a carious attack around orthodontic brackets, at or below pH 5.8, hydroxyapatite (HAP) is leached from the enamel surface.…”