Potential of High-Intensity Focused Ultrasound in Enamel Remineralization

Area of Science:

• Biomaterials Science
• Dental Research
• Nanotechnology

Background:

• Enamel white spot lesions (WSLs) require effective remineralization strategies beyond natural or fluoride treatments.
• Current methods for repairing WSLs have limitations in restoring ultrastructural integrity and function.
• Novel, minimally invasive approaches are needed for enamel remineralization.

Purpose of the Study:

• To investigate the use of high-intensity focused ultrasound (HIFU) for in vitro enamel WSL repair.
• To explore the synergy between HIFU and calcium phosphate ion clusters (CPICs) in hydroxyapatite (HAP) formation.
• To assess the ability of HIFU-CPIC treatment to restore enamel ultrastructure, mineral density, and nanomechanical properties.

Main Methods:

• Formulation and characterization of CPICs and amorphous calcium phosphate (ACP).
• Investigation of HIFU's effect on ACP-to-HAP transition using electron microscopy and diffraction techniques (TEM, HRTEM, SAED, XRD).
• Creation of artificial WSLs, treatment with CPICs and HIFU, followed by analysis using SEM, AFM, XRD, Raman spectroscopy, micro-CT, and nanoindentation.

Main Results:

• HIFU significantly accelerated the amorphous-to-crystalline HAP transition within 5-30 minutes, promoting c-axis growth.
• HIFU-CPIC treatment reduced WSL surface roughness and filled porous structures with oriented HAP crystallites, mimicking sound enamel after 5 minutes.
• Micro-CT and nanoindentation confirmed subsurface remineralization and restoration of mineral density and nanomechanical properties.
• HIFU demonstrated potent antibiofilm activity against Streptococcus mutans.

Conclusions:

• HIFU in synergy with CPICs provides an effective in vitro method for remineralizing enamel WSLs.
• The treatment restores enamel ultrastructure, mineral content, and mechanical properties with a preferred crystallite orientation.
• This HIFU-CPIC approach represents a promising, minimally invasive strategy for dental enamel repair with added antibiofilm benefits.