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Background: Although using light-cured composites for bonding orthodontic brackets has become increasingly popular, curing light cannot penetrate the metallic bulk of brackets and polymerization of composites is limited to the edges. Limited access and poor direct sight may be a problem in the posterior teeth. Meanwhile, effectiveness of the trans-illumination technique is questionable due to increased bucco-lingual thickness of the posterior teeth. Light-emitting diode (LED) light-curing units cause less temperature rise and lower risk to the pulpal tissue. The purpose of this study was to evaluate the clinical effectiveness of trans-illumination technique in bonding metallic brackets to premolars, using different light intensities and curing times of an LED light-curing unit., Methods: Sixty premolars were randomly divided into six groups. Bonding of brackets was done with 40- and 80-s light curing from the buccal or lingual aspect with different intensities. Shear bond strengths of brackets were measured using a universal testing machine. Data were analyzed by one-way analysis of variance test and Duncan's post hoc test., Results: The highest shear bond belonged to group 2 (high intensity, 40 s, buccal) and the lowest belonged to group 3 (low intensity, 40 s, lingual). Bond strength means in control groups were significantly higher than those in experimental groups., Conclusions: In all experimental groups except group 6 (80 s, high intensity, lingual), shear bond strength was below the clinically accepted values. In clinical limitations where light curing from the same side of the bracket is not possible, doubling the curing time and increasing the light intensity during trans-illumination are recommended for achieving acceptable bond strengths.

Background: Fibre reinforced composite bars (FRC) have applications as bonded retainers, space maintainers and anchorage/movement units. However, the bond strength of attachments to FRC anchorage bars is unknown., Aims: To compare the shear bond strengths of brackets bonded immediately to FRCs with different orthodontic adhesive systems and bonded with the same adhesives after a 48-hour delay, abraded with a diamond bur and etched with phosphoric acid., Method: One hundred and five recently extracted upper premolars were randomly assigned to seven groups (N = 15 teeth per group). FRCs were bonded to the buccal surfaces of the teeth and stainless steel orthodontic brackets were bonded to the FRCs with the following adhesive systems: Group 0 (Tetric Flow); Groups 1, 2 and 3 (Immediate bonding with chemically cured, no-mix and light cured composites, respectively, the bars covered with Tetric Flow); Groups 4, 5 and 6 (Bonding to FRCs delayed 48 hours, then bonded with chemically cured, no-mix and light cured composites, respectively, the bars covered with Tetric Flow). The FRC bars in Groups 4, 5 and 6 were abraded with a coarse-grit diamond bur before bonding the attachments to the bars. The shear bond strengths (SBS) were measured with a universal testing machine, and the adhesive remaining on the teeth after debonding was scored with the Adhesive Remnant Index (ARI). Data were analysed using analysis of variance (ANOVA), Duncan's post-hoc and Fisher's Exact test., Results: There were no statistically significant SBS differences between Groups 0 (Mean SBS: 9.56 MPa), 1 (Mean SBS: 9.74 MPa), 2 (Mean SBS: 10.72 MPa) or 3 (Mean SBS: 9.54 MPa). Groups 4, 5 and 6 (Bonding delayed by 48 hours) had SBSs of 11.79 MPa, 11.63 MPa and 13.11 MPa, respectively, and were significantly higher than the SBSs in Groups 1, 2 and 3 (Immediate bonding). There were no significant differences in ARI scores among the groups., Conclusions: The mean SBSs in all groups fell within the clinically acceptable range (> 7 MPa). The combination of a 48-hour delay between placement of an FRC bar and bonding an attachment, abrading the FRC with a diamond bur and etching with phosphoric acid resulted in higher bond strengths.

The aim of this study was to assess bonding of orthodontic metal brackets to porcelain surfaces using various surface treatment methods. Etching the porcelain with 9.6 percent HF followed by a bonding agent or silane application provided high and acceptable shear bond strengths.