# Long-term ion release, fluoride recharge, pH modulation, and mechanical aging of an experimental ACP-based composite compared with contemporary bioactive restorative materials

## TL;DR

This study compares the long-term performance of an experimental ACP-based dental material with other bioactive restoratives in terms of ion release, fluoride recharge, pH changes, and mechanical strength.

## Contribution

The study provides a comprehensive 12-month evaluation of an ACP composite's performance compared to existing bioactive dental materials.

## Key findings

- The ACP composite showed high early calcium and phosphate release but poor long-term mechanical durability.
- Surefil one™ demonstrated the best fluoride release and recharge while maintaining mechanical reliability.
- Cention N provided sustained ion release and the greatest alkalizing capacity with stable mechanical properties.

## Abstract

This study evaluated the 12-month ion release, fluoride recharge capacity, pH modulation, mechanical aging, and structural reliability of an experimental amorphous calcium phosphate (ACP)-based composite compared to contemporary bioactive restorative materials.

An experimental ACP composite was compared with Activa™ BioACTIVE-Restorative, Cention N, and Surefil one ™. Calcium (Ca2+), phosphate (PO43−), and fluoride (F−) release, along with pH changes, were assessed over 365 days in artificial saliva. Fluoride recharge was performed at six months using a single application of 5000 ppm sodium fluoride gel, followed by cumulative fluoride re-release measurement for 30 days. The flexural strength and modulus were evaluated at baseline, 6 months, and 12 months. Statistical analysis was conducted using mixed-model ANOVA with post-hoc tests, and flexural strength reliability was assessed using Weibull analysis (α = 0.05).

All materials exhibited an initial burst of ion release, followed by a progressive decline (p = 0.001). The ACP composite demonstrated the highest early calcium and phosphate release but negligible fluoride release and significant reductions in mechanical properties and reliability after aging. Cention N showed sustained multi-ion release, the greatest alkalizing capacity, and stable mechanical performance. Surefil one™ achieved the highest fluoride release and recharge capacity while maintaining a near-neutral pH and superior mechanical reliability. The Activa™ BioACTIVE-Restorative exhibited moderate ion release and intermediate mechanical performance.

Bioactive restorative materials exhibit distinct material-dependent behaviors. Alkasite-based systems showed balanced ion release and mechanical stability, fluoride-focused systems demonstrated superior recharge and reliability, and the ACP composite provided primarily short-term calcium–phosphate release with limited long-term durability.