Contaminazione dello smalto dentario e resistenza al distacco dei bracket

The aim of this study was to assess the effect of water and saliva contamination on shear bond strength of APC Plus orthodontic brackets bonded with 3 different adhesives (Transbond XT, Transbond Moisture Insensitive Primer, and Transbond Plus Self Etching Primer) 24h after bonding and after thermocycling. A total of 270 bovine permanent mandibular incisor were randomly divided into 18 groups (n=15). Each adhesive material was tested in 3 different enamel surface conditions: dry, water and saliva application after etching. As a result 9 groups were defined and debonded after 24h 9 other similarly partitioned groups debonded after thermocycling (1500 thermocycles: 5±2/50±5°C, bath 30", transfer 5"). The samples have been subjected to a shear bond test and data were statistically analyzed (ANOVA, Scheffè). The adhesive surfaces of enamel have been observed (16x) before bonding brackets and after the detachment to assess the quantity of adhesive left on the surface (ARI score; Kruskal-Wallis, Mann-Whitney tests). Conventional adhesive had the highest bond strength on dry enamel surfaces and the lowest on moisture contemned surfaces (p<0.001). Transbond Plus Self Etching Primer and Transbond Moisture Insensitive Primer were less influenced by water and saliva contamination (p<0.05) without significant differences. Thermocycling led more frequently to adhesive failure at the bracket interface in comparison with groups tested after 24h, even though it didn't affect shear strength significantly.