Remineralization of eroded enamel for improved orthodontic bracket bonding: An in vitro study

Effects of contemporary remineralization agents on the repair and regeneration of eroded enamel, specifically examining Vickers hardness (VH), shear bond strength (SBS), the calcium/phosphorus (Ca/P) ratio, and bracket-enamel interface.

Extracted maxillary premolars with intact enamel were selected. Sixteen samples with sound uneroded enamel (Group 1, control) and eighty artificially eroded samples were used. The eroded samples (n = 80) were etched with phosphoric acid and divided into five remineralization treatment groups (Groups 2, 3, 4, 5, and 6) based on the type of remineralization applied. VH and Ca/P ratios were assessed using energy dispersive X-ray spectroscopy. All samples were primed and bonded with orthodontic brackets. Two samples from each group were assessed under a scanning electron microscope to analyze the bracket-enamel interface. The remaining samples underwent SBS testing. The debonded surfaces were evaluated using the adhesive remnant index. Statistical analysis was conducted using ANOVA and post hoc multiple comparison tests (P < 0.05).

The lowest SBS was recorded in Group 2, where brackets were bonded to eroded enamel. In contrast, the highest SBS was observed in sound enamel. Group 2 also exhibited the lowest Ca/P ratio, while sound enamel demonstrated the highest mean VH. Notably, eroded enamel treated with hydroxyapatite nanoparticles (HAnp), NR-5^TM, and Curodont^TM Repair exhibited VH comparable to sound enamel.

Eroded enamel remineralized with HAnp, NR-5^TM, and Curodont^TM Repair demonstrated improved VH and SBS when metallic brackets were bonded to the enamel surface, suggesting potential effectiveness in orthodontic applications.