Evaluation of push-out bond strength at different root dentin levels

Objectives:  The purpose of this study was to evaluate push-out bond strengths of two different materials for build-up restoration and investigate the influence of different root dentin levels on bond strengths.

Methods:  Extracted single root human maxillary canines were used. The teeth were sectioned at the cement-enamel junction using diamond saw under water cooling.  After enlargement of up to 2mm diameter of root canal using Peeso reamers, two different adhesive system, group1:Brush&Bond^TM/Absolute-Dentin^TM (Parkell;USA) or group2:Bond-1^®/Build-It^® FR^TM (Pentron;USA) were applied to each root canal in accordance with manufactures' instructions.  After storage in water at 37˚C for 24hours, all specimens were sectioned perpendicular to long axis and ground to 0.7mm-thick slices located at 3-level (coronal, middle, apical segment).  The push-out bond strengths of each section (coronal, middle) was calculated as the force at failure divided by the bonded cross-sectional surface area, and this testing was measured at a cross-head speed of 1.0mm/min.  These data were statistically analyzed by ANOVA and Bonferroni's test (n=10).

Results:  Table showed the mean push-out strengths of two groups at different root dentin levels.  From these results, difference in root location did not affect bond strength of two materials to radicular dentin.  Furthermore, bond strengths of group1 were significantly higher than those of group2 at different root dentin levels, respectively. 

Conclusion:  It was suggested that adhesive system of group1 had high bond strength because this system was bondable to both radicular dentin and fiber-post. In particular, it was considered that difference in root location did not affect bond strength because Brush&Bond had high photo-sensitivity and characteristics of self-cure.  These results indicated that adhesive system of group1 could be useful for build-up restoration.

	Push-out bond strengths (MPa)
Group	Coronal	Middle
1	17.8±5.1a	22.8±3.1a
2	1.3±0.6b	3.8±1.8bb

Values with same letters are not significantly different (p>0.05).