Comparison of Bond Strength of Metal and Ceramic Brackets
Appropriate bond strength between bracket and tooth surface is one of the most important aspects of orthodontic treatments [1,2]. Bonding of MIM monoblock metal bracket to enamel started in the mid 1960s [3,4]. Only auto-polymerizing materials were available at the time. Bonding of orthodontic brackets with visible light-cure adhesives was first reported by Tavas and Watts .
MIM bondable metal bracket with a nominal base area of 15.1mm 2 were bonded to the etched enamel and other steps were performed similar to group A. The adhesive was high-power light-cured for three seconds (1.5 seconds from mesial and 1.5 seconds from distal).
The mean, standard deviation, minimum and maximum values of SBS of metal and ceramic brackets to tooth surfaces using two models of light-curing units were computed and reported. The SBS data were analyzed using one-way ANOVA, followed by Tukey’s post hoc test. Failure mode data were subjected to Kruskal-Wallis nonparametric test, followed by LSD post hoc test. Statistical significance was set at alpha=0.05.
Objective. Clinical comparison of the survival rates between stainless steel and ceramic brackets over a 12-month period. Materials and Methods. The study involved 20 consecutive patients with diagnosed malocclusion that required two-arch fixed appliance treatment. The participants were randomly divided into two 10-member groups. Group 1 was treated with Abzil Agile (3M Unitek) stainless steel brackets; group 2 was treated with Radiance (American Orthodontics) monocrystalline ceramic brackets. All the sapphire brackets were bonded by the same operator.
On the basis of their in vitro study, Reynolds and von Fraunhofer  stated that the minimum bond strength of 6–8 MPa is considered appropriate, whereas Bishara  suggested that the bonding strength ought to exceed 13.5 MPa. Recently Gauge  assumed that the ideal orthodontic adhesive should withstand forces over 20 MPa. The majority of the studies that evaluated the bond strength of zirconia brackets were carried out as in vitro experiments under ideal laboratory conditions that may not reflect all clinical conditions. In vitro experiments provide information about initial bond strength to the enamel but cannot serve as predictors of bracket survivability [12–14]. Therefore, more accurate guidance on the clinical relevance of adhesion protocols is provided by in vivo tests, which assess the failure rate of the enamel-boding agent-bracket interface during treatment.