Adhesion of Orthodontic Cements Formulated With Microencapsulated Remineralizing Agents

Objectives: The objective of this study was to determine the adhesion to enamel and mechanism of failure of orthodontic bracket and band cements formulated with microencapsulated remineralizing agents.
Methods: A heterogeneous polymerization technique was utilized to prepare microcapsules containing aqueous solutions of 0.8M NaF, 5M Ca(NO₃)₂ and 3M K₂HPO₄. These microcapsules were formulated into orthodontic cement that differed by the types of monomers used for the continuous phase, the glass loading level, and the fumed silica loading level. The monomers used in the formulations were bisGMA and TEGMA in different ratios. In these formulations, the microcapsules were loaded between 4-7w/w% (2-4w/w% of aqueous fluoride solution, 2w/w% of aqueous calcium solution and 1w/w% of aqueous phosphate solution). Shear bond strength (SBS) to intact bovine enamel was determined by preparing bonded assemblies using an Ultradent fixture and loading to failure (1.0 mm/min) after 7 days of water storage at 37⁰C. Microscopy was used to determine the mechanism of failure.
Results: A table highlighting some of the results from the shear bond strength measurements is shown below.
Conclusions: The shear bond strength to intact enamel for orthodontic bracket and band cements formulated with microencapsulated remineralizing agents was measured. The shear bond strength of these band and bracket cements can be controlled as a function of the glass loading, fumed silica loading and bisGMA:TEGMA ratio.