Method: Thirty human caries-free third molars were then sectioned in the central region, in a vestibular-lingual direction, parallel to the long axis with a diamond double-faced disc. Following this, adhesive systems were applied on mesial and distal surfaces according to the experimental group – by doubling the time of application of the recommended primer-acid or by applying 37% phosphoric acid, prior to the application of the adhesive system and according to manufacturer’s instructions (control). Blocks of composed resin measuring 6 mm in height were made, in order to obtain specimen for the microtensile test. Specimens were stored in distilled water for 24 hours and 180 days. The test was performed with a speed of 0.5 mm/min. Data obtained were submitted to ANOVA and Tukey Kramer tests (α=5%).
Result: It was observed the time of primer application did not significantly influence the adhesive strength for both one and two steps self-etching adhesive systems. Prior application of phosphoric acid significantly increased the adhesive strength for both self-conditioning adhesives. Only One Up Bond F showed significantly better adhesive strength after 180 days of storage in water, independently on the surface treatment used.
Conclusion: It is concluded that the treatment with phosphoric acid prior to the use of self-conditioning adhesive systems was effective in increasing adhesive strength to enamel even after long term storage.