ABSTRACT
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 NACP-rechargeable 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 (P>0.1). 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 (P>0.1). The ion re-release concentrations at 14 days versus various recharge treatments were as follows: 1 min 3 times>3 min 2 times>1 min 2 times>6 min 1 time>3 min 1 time>1 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.
Subject(s)
Benzoates/chemistry , Bisphenol A-Glycidyl Methacrylate/chemistry , Calcium Phosphates/chemistry , Dental Cements/chemistry , Methacrylates/chemistry , Nanoparticles , Tooth Remineralization/methods , Humans , In Vitro Techniques , Materials Testing , Orthodontic Brackets/adverse effects , Shear StrengthABSTRACT
OBJECTIVE: To investigate the maximum resistance strength of a new orthodontic anchorage system named bone-bonding screw. METHODS: Thirty-six self-designed two-section bone-bonding screws were bonded to the surface of tibia in 12 rabbits with N-2-butyl cyanoacrylate. The maximum resistance strength of the screws was tested immediately, 2 weeks, 4 weeks and 8 weeks after bonding, respectively. RESULTS: The average maximum resistance strengths of the bone-bonding screws immediately, 2 weeks, 4 weeks and 8 weeks after bonding were 11.55 (8.96, 12.73), 6.04 (1.88, 10.57), 2.30 (0, 3.24), and 49.85 (20.70, 66.01) N, respectively. The difference between each group was statistically significant (P < 0.05). The failure rate of the bone-bonding screws was 17% (6/36). CONCLUSIONS: The maximum resistance strength of the bone-bonding screw could suffice for orthodontics.
