A Novel Orthodontic Adhesive Made From Bioactive Glass To Prevent Demineralisation.

Objectives: To design a novel orthodontic adhesive from bioactive glass and resin capable of preventing demineralisation around orthodontic brackets by releasing Ca²⁺, PO₄^3- and F^- ions.
Methods: Three bioactive glasses of high fluoride and low sodium content were synthesized via the melt-quench route. The refractive index was calculated to match that of the resin, and a light curable paste was made from the glass powder and a resin made from BisGMA and TEGMA. 20 Human teeth imbedded in acrylic discs were bonded with incisor brackets and tested for shear bond strength in comparison with (Transbond XT). The glass powders, and the adhesive in the form of discs, were characterized for their bioactivity through FTIR and XRD studies both before and after immersion in tris buffer solution which were then analysed for fluoride and calcium release and pH change by ion selective electrode and pH meter respectively. Adhesive discs were examined by scanning electron microscopy (SEM) for confirmation of apatite formation.
Results: FTIR and XRD data clearly revealed the formation of apatite. SEM images showed an apatite layer around glass particles. Around 30 ppm F^- ions were released after 24 hours which then reduces to 20ppm after 1 week while Ca²⁺ ions released within 24 hours were 127 ppm. pH values of the tris were elevated to 8.8 from the original 7.34 after immersion. Comparable values of shear bond strength were found for the new adhesive and Transbond XT (8 and 10 MPa respectively).
Conclusions: This formula of bioactive glass with the resin is successful in producing an applicable orthodontic adhesive that release a considerable amount of F^- and Ca²⁺ ions with apatite formation which are important elements for prevention of decalcification.