OBJECTIVE To histopathologically evaluate the effect of etching sound dentin with 10% phosphoric acid, in cavities prepared just within the DEJ on young patients. METHODS Twenty-four orthodontic patients who required premolar extractions were selected for the study. Each of the patients had facial Class V resin composite restorations placed in two maxillary premolars selected for extraction. Each preparation was cut circular, 2 mm in circumference and 0.5 mm into dentin. The dentin of one maxillary premolar preparation, randomly selected, was etched with 10% phosphoric acid (Bisco) for 20 seconds. This was followed by the placement of a dentin bonding agent (All-Bond 2) and a microfilled composite restoration (Silux). The contralateral maxillary premolar, received a similar preparation, but the dentin surface was lined with a light-cured glass ionomer liner before etching of the enamel, followed by placement of a dentin bonding agent and a microfilled resin composite restoration. One of the mandibular premolars was randomly selected as a negative control, having no treatment. Fourteen days after the placement of the restorations, the teeth were extracted, and histologically examined for insult to the pulpal tissues. Injury to the pulp was evaluated by quantitative measures of histopathology, including necrosis, infiltration by inflammatory cells, and other indicators of tissue injury. RESULTS Using a Kruskal-Wallis analysis, there was no statistically significant difference in pulpal histopathology of the teeth with etched dentin versus teeth with dentin protected by a liner or the negative control teeth (P < 0.05).