INTRODUCTION: During apicoectomy and retrograde cavity preparation, a smear layer, which contains microorganisms and necrotic pulpal tissues, is formed on the dentinal surfaces cut by the instruments. Bacteria can survive and proliferate inside or below the smear layer. The purpose of this study was to evaluate in vitro two different procedures for the removal of the smear layer in retrocavities prepared with ultrasonic retrotips. METHODS: Twenty-eight single-rooted teeth were cleaned, shaped, and obturated with gutta-percha and sealer. The apical 3 mm of each root were cut with a carbide bur, and retrograde cavities were prepared with ProUltra ultrasonic retrotips (Maillefer Dentsply, Baillagues, Switzerland) at a depth of 3 mm. Teeth in group A were treated with a gel of 35% orthophosphoric acid for 15 seconds, and teeth in group B were treated with a gel of 24% EDTA at a neutral pH for 2 minutes. The samples were prepared for scanning electron microscopic observation and scored for the presence of the smear layer on the retrocavity walls. RESULTS: Eighty percent of the teeth in group A showed an optimal degree of cleanliness of the walls, with dentinal tubules completely open. The majority of analyzed samples coming from group B showed dentinal tubules covered with the smear layer. CONCLUSIONS: The analysis of the samples showed that orthophosphoric acid is more effective than EDTA in removing surgical smear layer even with less time of action.
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