Abstract: BACKGROUND: At present, root canal sealants have the shortcomings of poor biocompatibility, mechanical properties, and degradation, and nano-β-tricalcium phosphate and nano-hydroxyapatite materials have good biocompatibility, degradability, and sealability, and have important research value in the field of root canal sealants.
OBJECTIVE: To construct new root canal sealing material with microscopic morphology and three-dimensional structure similar to the hard tissue structure of the tooth by controlling the nucleation, growth, and reconstruction of nano-β-tricalcium phosphate and nano-hydroxyapatite crystals by the dentin sheet hard template method
METHODS: Totally 30 discarded third molars extracted due to impacted wisdom teeth were collected and dentin slices were prepared. Different masses of nano-β-tricalcium phosphate (or nano-hydroxyapatite) were dissolved in distilled water, and the solution was poured into a culture dish containing a dentin slice and placed in a 37°C constant temperature incubator for 12 hours to obtain 10%, 20%, and 30% nano-β-tricalcium phosphate/dentin slices and 10%, 20%, and 30% nano-hydroxyapatite/dentin slices, with pure nano-β-tricalcium phosphate and nano-hydroxyapatite as controls. The eight groups of samples were characterized and analyzed by scanning electron microscopy, Raman spectroscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy.
RESULTS AND CONCLUSION: (1) Scanning electron microscopy: Under the regulation of dentin slices, the microstructure and morphology of nano-β-tricalcium phosphate and nano-hydroxyapatite changed. The morphology of nano-β-tricalcium phosphate particles changed from irregular polygons to short rods and spheres, arranged in three-dimensional clusters, and the morphology of nano-hydroxyapatite particles changed from rods and needles to short rods and other forms. Nano-β-tricalcium phosphate and nano-hydroxyapatite particles were orderly arranged between the dentin collagen fiber network, and with the increase of nano-β-tricalcium phosphate or nano-hydroxyapatite concentration, the adhesion and agglomeration phenomenon became more and more obvious, and the arrangement became more and more dense. (2) Raman spectroscopy: Under the regulation of dentin slices, the functional groups of nano-β-tricalcium phosphate and nano-hydroxyapatite did not change, but with the increase of nano-β-tricalcium phosphate or nano-hydroxyapatite concentration, the intensity of the functional group characteristic peak increased. (3) X-ray diffraction: Under the regulation of dentin slices, the crystallinity of nano-β-tricalcium phosphate and nano-hydroxyapatite increased, the crystal structure became more complete, and the grains became smaller. Among them, 30% nano-β-tricalcium phosphate/dentin slices and 30% nano-hydroxyapatite/dentin slices had the best crystallinity. (4) X-ray photoelectron spectroscopy: Under the regulation of dentin slices, the elemental composition of nano-β-tricalcium phosphate and nano-hydroxyapatite remained unchanged, but some chemical state changes and characteristic peak intensity enhancement characteristics appeared. (5) The results show that the characterization performance of nano-β-tricalcium phosphate or nano-hydroxyapatite composites constructed with dentin slices as hard templates is stable, and dentin slices have a certain regulatory function on nano-β-tricalcium phosphate and nano-hydroxyapatite. Among them, 30% nano-β-tricalcium phosphate/dentin slices and 30% nano-hydroxyapatite/dentin slices have better characterization performance.

Key words: nano β-tricalcium phosphate, nano-hydroxyapatite, hard template, dentin slice, characterization performance, crystal, microstructure, molecular structure