IADR Abstract Archives
Bioactive Glass-containing Orthodontic Bonding Agents: Changes in Microhardness Adjacent to Brackets
Objectives: Plaque accumulation and white spot lesions are common around orthodontic brackets, especially in teenage patients. The aim of this study was to investigate two new bioactive glass (BAG)-containing orthodontic resin bonding agents to assess whether they could prevent demineralized lesions from forming adjacent to brackets.
Methods: BAGs were synthesized in our laboratory and mixed with monomers and photoinitiators to create 60% filler-load BAG adhesives. BAG compositions used were (65mol% SiO2/31mol%CaO/4mol%P2O5)(65BAG) and (85mol%SiO2/11mol%CaO/4mol%P2O5)(85BAG). Caries-free human molars were randomly divided into three groups and Victory series brackets (3M Unitek, St Paul, MN) were bonded to each using one of the adhesives: 65BAG, 85BAG or conventional Transbond XT adhesive (3M Unitek, St Paul, MN). The external surfaces of the teeth were covered with nail varnish up to 4 mm from the brackets, followed by immersion into a BHI broth containing Streptococcus mutans, for up to 21 days. Teeth were embedded into epoxy resin and sectioned buccolingually, parallel to the long axis of the tooth, with a water-cooled diamond wafering blade on a low-speed rotary saw (Isomet-5000). Each section was wet polished through 4000-grit silicon carbide polishing paper. Knoop micro-hardness testing (Duramin-5, Struers, Cleveland, OH) was used creating columns of indentations directly beneath the bracket, as well as adjacent to the bracket. Data was calculated as the percent change in micro-hardness of enamel adjacent to the bracket versus under the bracket. Hardness values were compared with ANOVA and post-hoc Tukey with α = 0.05.
Results: The BAG-containing bonding agents did not completely prevent demineralization softening, but reduced the magnitude of the hardness reduction. It also appeared to promote remineralization to a depth of 400μm.
Conclusions: Compared to the conventional bracket adhesive, Transbond XT, the experimental bonding agents both promoted remineralization and reduced demineralization of the tooth adjacent to the brackets.
Methods: BAGs were synthesized in our laboratory and mixed with monomers and photoinitiators to create 60% filler-load BAG adhesives. BAG compositions used were (65mol% SiO2/31mol%CaO/4mol%P2O5)(65BAG) and (85mol%SiO2/11mol%CaO/4mol%P2O5)(85BAG). Caries-free human molars were randomly divided into three groups and Victory series brackets (3M Unitek, St Paul, MN) were bonded to each using one of the adhesives: 65BAG, 85BAG or conventional Transbond XT adhesive (3M Unitek, St Paul, MN). The external surfaces of the teeth were covered with nail varnish up to 4 mm from the brackets, followed by immersion into a BHI broth containing Streptococcus mutans, for up to 21 days. Teeth were embedded into epoxy resin and sectioned buccolingually, parallel to the long axis of the tooth, with a water-cooled diamond wafering blade on a low-speed rotary saw (Isomet-5000). Each section was wet polished through 4000-grit silicon carbide polishing paper. Knoop micro-hardness testing (Duramin-5, Struers, Cleveland, OH) was used creating columns of indentations directly beneath the bracket, as well as adjacent to the bracket. Data was calculated as the percent change in micro-hardness of enamel adjacent to the bracket versus under the bracket. Hardness values were compared with ANOVA and post-hoc Tukey with α = 0.05.
Results: The BAG-containing bonding agents did not completely prevent demineralization softening, but reduced the magnitude of the hardness reduction. It also appeared to promote remineralization to a depth of 400μm.
Conclusions: Compared to the conventional bracket adhesive, Transbond XT, the experimental bonding agents both promoted remineralization and reduced demineralization of the tooth adjacent to the brackets.