Shear Bond Strength of a Novel Molar Retentive Base Design

As more clinicians opt to bond molars instead of banding them during orthodontic treatment, it becomes essential that the bonds of bonded molar attachments not fail and not cause the clinician extra chairtime and lost revenue.  Objectives:  This study evaluated the shear bond strength of a bonded molar attachment with a novel retentive base design to human molars using different adhesives.   Methods:  60 extracted human molars were divided into six groups of 10 (n=10).  Two base designs were tested: Ovation (GAC) and an experimental base design (Exp).  The GAC base was stainless steel, 120-80 gauge double mesh type.  The Exp retentive base was stainless steel and designed such that inverted tripods extended from a stem connected to the base.  The thickness of the base was comparable to the control GAC.  The brackets were bonded with Transbond XT (3M Unitek), Pad Lock (Reliance Orthodontic Products), and Light Bond (Reliance Orthodontic Products).  All teeth were etched with 37% phosphoric acid, and one primer, Assure (Reliance Orthodontic Products), was used for all specimens.  Bonded specimens were stored in water for 7 days.  The specimens were loaded in shear until failure on an Instron testing machine (model 5566) with a crosshead speed of 1 mm/minute. One-way and two-way ANOVA were performed with Tukey's HSD post-hoc comparisons of the mean to determine any statistical differences in shear bond strength (MPa).  The significance level was set at 5% (p=0.05).  Results:    There was no significant difference in shear bond strength between the Exp and GAC brackets (p>.05).

	Transbond	Pad Lock	Light Bond
Exp	18.3±5.3	15.0±6.5	15.0±2.9
GAC	15.6±5.6	17.5±4.9	19.8±2.7

Conclusion:   The novel base design tested in this study provided statistically similar shear bond strengths compared to the currently marketed GAC bracket.