Bond strength with various etching times on young permanent teeth

Abstract

Tensile bond strengths of an orthodontic resin cement were compared for 15-, 30-, 60-, 90-, or 120-second etching times, with a 37% phosphoric acid solution on the enamel surfaces of young permanent teeth. Fifty extracted premolars from 9- to 16-year-old children were used for testing. An orthodontic composite resin was used to bond the bracket directly onto the buccal surface of the enamel. The tensile bond strengths were tested with an Instron machine. Bond failure interfaces between bracket bases and teeth surfaces were examined with a scanning electron microscope and calculated with mapping of energy-dispersive x-ray spectrometry. The results of tensile bond strength for 15-, 30-, 60-, or 90-second etching times were not statistically different. For the 120-second etching time, the decrease was significant. Of the bond failures, 43%-49% occurred between bracket and resin interface, 12% to 24% within the resin itself, 32%-40% between resin and tooth interface, and 0% to 4% contained enamel fragments. There was no statistical difference in percentage of bond failure interface distribution between bracket base and resin, resin and enamel, or the enamel detachment. Cohesive failure within the resin itself at the 120-second etching time was less than at other etching times, with a statistical significance. To achieve good retention, to decrease enamel loss, and to reduce moisture contamination in the clinic, as well as to save chairside time, a 15-second etching time is suggested for teenage orthodontic patients. In the etching time over 30 seconds, some enamel fragments were found, and the amount of enamel fragments was proportional to the length of etching time. (A M J O RTHOD D ENTOFAC O RTHOP 1991;100:72-9.)