Influence of cross-head speed in orthodontic bond strength testing

Objective: The aim of this study was to investigate the influence of cross-head speed on debonding force of orthodontic brackets. Methods: One hundred and twenty extracted permanent bovine mandibular incisors were randomly divided into 4 groups of 30 specimens each. Teeth were bonded with stainless steel orthodontic brackets. Enamel surfaces were etched with 37% phosphoric acid for 30 seconds and bonded with a composite adhesive. Debonding force measurements were performed with a universal testing machine Zwicki Z 2.5 (Zwick, Germany). Cross-head speeds of the four groups were: 0.1 mm s−1 (group A), 0.5 mm s−1 (group B), 1.0 mm s−1 (group C), 5.0 mm s−1 (group D). Results: Mean debonding force measurements were as follows: 215.35 (39.09) N (group A), 231.79 (48.62) N (group B), 236.64 (39.26) N (group C), 224.95 (34.67) N (group D). Analysis of variance indicated that there were no significant differences in debonding forces between the groups investigated. The adhesive remnant index showed a median value of 2.0 for all groups. Significance: Cross-head speed variation between 0.1 and 5 mm min−1 does not seem to influence debonding force measurements or failure mode of brackets bonded to enamel with a composite adhesive.