Impact of amino acid-regulated beta tricalcium phosphate hydroxyapatite on enamel: An updated perspective on hydroxyapatite crystal growth for adhesive bonding?

AIMS AND OBJECTIVES

To analyse development of hydroxyapatite (HAp) crystals doped with glutamic acid and phosphorine residue (Ser-OPO) having self-remineralization, biocompatible and optimum bonding properties MATERIALS AND METHODS: β-tri calcium phosphate, ammonium phosphate dibasic HAp was dissolved with strontium Flouride Glu or Ser-OPO components and utilised in two Ca(PO) and Ca(PO) groups. HAp formulation was evaluated for particle-size analysis, crystal size and indices using FTIR. Demineralized enamel specimens were treated and characterized using transmission electron microscopy (TEM), Xray diffraction (XRD), solid state NMR, and mechanical properties. MC3T3 mouse fibroblastic cells were evaluated for alkaline-phosphate activity (ALP). Human gingival fibroblasts (PGF) were evaluated for morphology. After modifying Universal adhesives, tensile force was assessed at 24 hr and 3 months.

RESULT

Increasing concentrations of experimental solution exposure significantly affect mean diameter of HAp. The increasing FTIR intensity, were displayed; Ca(PO) > Ca(PO)> control. Ca(PO) revealed existence of distinct crystals, with planes orientated perpendicular to longer axis of tooth. XRD pattern indicated crystal growth with a rise in peak intensities in Ca(PO) group. The NMR spectra for Glu and Ser-OPO elucidated interactions between carbon atoms in amino acid and hydrogen atoms on HAp surfaces. Surface microhardness of Ca(PO) specimens showed significantly higher values on day 28 (p< 0.05). ALP density value of cells was significantly higher for Ca(PO) group on day 7 and 14. Ca(PO) and Ca(PO) enhanced migration of PGF cells in comparison to the control group (p<0.05). Ca(PO) and Ca(PO) groups showed significant differences in bond strength at different time points CONCLUSION: Ca(PO) and Ca(PO) were structurally integrated into the lattice demonstrating changes within the crystallite size and became conducive for adhesive bonding.

CLINICAL SIGNIFICANCE

The new amino acid-based hydroxyapatite formulation is chemically stable due to the substitution of OH- with F and is crucial in the rehardening of caries and adhesive bonding.