Amelogenin-assisted ex vivo remineralization of human enamel: Effects of supersaturation degree and fluoride concentration

Abstract

The formation of organized nanocrystals that resemble enamel is crucial for successful enamel remineralization. Calcium, phosphate and fluoride ions and amelogenin are important ingredients for the formation of organized hydroxyapatite (HAP) crystals in vitro. However, the effects of these remineralization agents on the enamel crystal morphology have not been thoroughly studied. The objective of this study was to investigate the effects of fluoride ions, supersaturation degree and amelogenin on the crystal morphology and organization of ex vivo remineralized human enamel. Extracted third molars were sliced thin and acid-etched to provide the enamel surface for immersion in different remineralization solutions. The crystal morphology and mineral phase of the remineralized enamel surface were analyzed by FE-SEM, ATR-FTIR and XRD. The concentration of fluoride and supersaturation degree of hydroxyapatite had significant effects on the crystal morphology and crystal organization, which varied from plate-like loose crystals to rod-like densely packed nanocrystal arrays. Densely packed arrays of fluoridated hydroxyapatite nanorods were observed under the following conditions: σ(HAP) = 10.2±2.0 with fluoride 1.5±0.5 mg/L and amelogenin 40±10 µg/mL, pH 6.8±0.4. A phase diagram summarized the conditions that form dense or loose hydroxyapatite nanocrystal structures. This study provides the basis for the development of novel dental materials for caries management.

Effects of gallic acid on the morphology and growth of hydroxyapatite crystals

“…At the same time, GA decreased the local Ca 2+ concentration and supersaturation by connecting with Ca 2+ , which are important to control the nucleation sites and rates of mineralization. 23 GA enhanced the formation of amorphous calcium-phosphate and inhibited the conversion rate to apatite like fluoride. 24 Additionally, the GA-HAP crystals were tested and directly observed using ATR-FTIR and fluorescence microscopy.…”

Control of hydroxyapatite crystal growth by gallic acid

“…In the proposed model, the size of the domains and the crystals alignment are governed by GA-HAP complex formed by the interactions between -carbonyl groups and -OH 22) , which restrict the growth of the crystals and enhanced aggregation. GA might interact with Ca 2+ ions to decrease the local Ca 2+ concentration and supersaturation of the reaction, which regulates the nucleation sites and rates of mineralization 23) , to avoid the fast reaction and form relatively small domain size crystals. At the same time, these GA-HAP units may connect with each other via the negatively charged GA and the intermolecular force between its aryl rings.…”

Effect of caries infiltration technique and fluoride therapy on the bond strength of the demineralized enamel

“…When appropriate methods are employed, the caries lesion may be stopped at its initial phase or it may even be reversed [15].…”