The Effect of Five-year Storage Prior to Bonding on Enamel/Composite Bond Strength

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Abstract
The purpose of this study was to examine the effect of pre-bonding storage durations on the shear strength of light-cured composite bonded to enamel. Thirty whole extracted human molars - 12 with a storage time of five years, 12 with a storage time of three or fewer months, and six with a storage time of 24 hours or less - were mounted in improved dental stone in copper tubing. The molars were faced 90° to the horizontal with a milling device to produce 120 surfaces, 48 each for two groups, and 24 for one group. Composite buttons 2.3 mm in diameter were bonded to the enamel using the acid-etch light-curing system. The samples were tested in shear utilizing a cross-head speed of 0.5 cm/min with a 500-kg load cell. The results showed that: (1) there was no significant difference, at the 0.05 confidence level, in compositelenamel bond strength between teeth stored for 24 hours, three months, and five years prior to bonding; (2) the lingual surface developed the highest composite/enamel bond strength in all three groups; and (3) enamel fracture occurred 29% of the time on de-bonding.