Abstract
White spot lesions (WSL) due to enamel demineralization are major complications for orthodontic treatments. Calcium phosphate (CaP) dental resins with Ca and P ion releases are promising for remineralization. However, previous Ca and P releases lasted for only weeks. Experimental orthodontic cements were developed using pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA) at mass ratio of 1:1 (PE); and PE plus 10% of 2-hydroxyethyl methacrylate (HEMA) and 5% of bisphenol A glycidyl dimethacrylate (BisGMA) (PEHB). Particles of amorphous calcium phosphate (ACP) were incorporated into PE and PEHB at 40% filler level. Specimens were tested for bracket-enamel shear bond strength, water sorption, CaP release, and ion recharge and re-release. PEHB+40ACP had higher bracket-enamel bond strength and ion release and rechargeability than PE+40ACP. ACP incorporation into the novel orthodontic cement did not adversely affect the bracket-enamel bond strength. Ion release and re-release from the novel ACP orthodontic cement indicated favorable release and re-release patterns. The recharged orthodontic cement could release CaP ions continuously for four weeks without further recharge. Novel rechargeable orthodontic cement containing ACP was developed with a high bracket-enamel bond strength and the ability to be repeatedly recharged to maintain long-term high levels of CaP ion releases.
Highlights
Incorporated into methacrylate composites, gums, pastes and other dental products and achieved promising effects on caries prevention and enamel remineralization[14,15,16,17]
The following hypotheses were tested: (1) The new rechargeable CaP orthodontic cement would yield a bracket-enamel bond strength similar to commercial orthodontic cements without CaP ion release and recharge; (2) the enamel bond strength and the Ca and P ion recharge and re-release efficacy would depend on the cement resin composition; and (3) the new CaP orthodontic cement would exhibit continuous ion release, and the ion release would not decrease with increasing number of recharge and re-release cycles
There was a reduction in the shear bond strength of the 1 month aged specimens for the PEHB+40ACP group, there was no significant difference with the specimen group after 1 day in water
Summary
Incorporated into methacrylate composites, gums, pastes and other dental products and achieved promising effects on caries prevention and enamel remineralization[14,15,16,17]. ACP-containing bonding agents and composites produced high levels of Ca and P ion release[21,22]. The potential of ACP as an acid neutralizing agent by way of increased Ca and P ion release at pH of 4 levels, when caries is most prone to develop could be essential[23]. The new CaP composite and bonding agent demonstrated excellent Ca and P ion rechargeability, yielding sustained long-term Ca and P ion releases for the first time[29,30,31]. The objectives of this study were to develop a rechargeable CaP-containing dental cement and investigate the effects of ACP incorporation on orthodontic bracket-enamel bond strength, water sorption, as well as Ca and P ion recharge and re-release. The following hypotheses were tested: (1) The new rechargeable CaP orthodontic cement would yield a bracket-enamel bond strength similar to commercial orthodontic cements without CaP ion release and recharge; (2) the enamel bond strength and the Ca and P ion recharge and re-release efficacy would depend on the cement resin composition; and (3) the new CaP orthodontic cement would exhibit continuous ion release, and the ion release would not decrease with increasing number of recharge and re-release cycles
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