Novel rechargeable calcium phosphate nanoparticle- containing orthodontic cement

摘要

White spot lesions(WSLs), due to enamel demineralization, occur frequently in orthodontic treatment. We recently developed a novel rechargeable dental composite containing nanoparticles of amorphous calcium phosphate(NACP) with long-term calcium(Ca) and phosphate(P) ion release and caries-inhibiting capability. The objectives of this study were to develop the first NACPrechargeable orthodontic cement and investigate the effects of recharge duration and frequency on the efficacy of ion re-release.The rechargeable cement consisted of pyromellitic glycerol dimethacrylate(PMGDM) and ethoxylated bisphenol A dimethacrylate(EBPADMA). NACP was mixed into the resin at 40% by mass. Specimens were tested for orthodontic bracket shear bond strength(SBS) to enamel, Ca and P ion initial release, recharge and re-release. The new orthodontic cement exhibited an SBS similar to commercial orthodontic cement without CaP release(P40.1). Specimens after one recharge treatment(e.g., 1 min immersion in recharge solution repeating three times in one day, referred to as "1 min 3 times") exhibited a substantial and continuous re-release of Ca and P ions for 14 days without further recharge. The ion re-release did not decrease with increasing the number of recharge/re-release cycles(P40.1). The ion re-release concentrations at 14 days versus various recharge treatments were as follows: 1 min 3 times43 min 2 times41 min 2 times46 min 1 time43 min 1 time41 min 1 time. In conclusion, although previous studies have shown that NACP nanocomposite remineralized tooth lesions and inhibited caries, the present study developed the first orthodontic cement with Ca and P ion recharge and long-term release capability. This NACP-rechargeable orthodontic cement is a promising therapy to inhibit enamel demineralization and WSLs around orthodontic brackets.