# Evaluation of the effects of different remineralizing agents on the microhardness and mineral content of bleached enamel along different storage times

## TL;DR

This study tests how different agents help repair tooth enamel weakened by bleaching, finding that some agents restore hardness and mineral content over time.

## Contribution

The study introduces a systematic evaluation of multiple remineralizing agents on bleached enamel's microhardness and mineral content over 30 days.

## Key findings

- PAMAM showed the highest microhardness restoration at 7, 15, and 30 days.
- Fluoride content decreased after bleaching but was effectively restored by remineralizing agents.
- Calcium levels remained unaffected by agents or storage time, while phosphorus and fluoride levels were significantly influenced.

## Abstract

This study evaluated the effects of various remineralizing agents on Vickers microhardness (HV) and mineral weight percentages (wt%) of bleached enamel during 30 days of storage in artificial saliva.

For HV testing, a total of 154 human specimens were used, including 14 specimens that were assigned to two control groups: a positive (sound unbleached enamel, n = 7) and a negative control (bleached using a 32% hydrogen peroxide, n = 7). The remaining 140 specimens were bleached and randomly divided into 20 experimental groups (n = 7), based on two factors: remineralizing agents; four agents (potassium nitrate with fluoride, casein-phosphopeptide-amorphous calcium phosphate with fluoride, hydroxyapatite with fluoride, and PAMAM), and storage times; five times (24 h, 3 days, 7 days, 15 days, and 30 days). For mineral wt%, 110 human enamel specimens were used, including 10 specimens for positive (n = 5) and negative control (n = 5), and 100 bleached enamel specimens divided into 20 experimental groups (n = 5/group), based on two factors, same as for HV testing. Data were analyzed using two-way ANOVA followed by Tukey’s HSD post hoc tests (α = 0.05).

Remineralizing agents and storage time significantly affected HV of bleached enamel (p < 0.001). PAMAM showed the highest HV at 7, 15, and 30 days (p < 0.05). Calcium (Ca) wt% was unaffected by either remineralizing agents (p = 0.848) or storage time (p = 0.141). Phosphorus (P) wt% was significantly influenced by both factors (p < 0.001 and p = 0.023, respectively). Fluoride (F) wt% was significantly affected only by the remineralizing agents (p = 0.001).

Bleaching significantly decreased enamel HV and F wt%, whereas remineralizing agents effectively restored both.

The use of different remineralizing agents may help counteract the detrimental effects of bleaching on enamel.