RUXANDRA SAVA ROSIANU, COSMIN SINESCU, MEDA LAVINIA NEGRUTIU, TIBERIU HOSSZU, ANCA TUDOR, ANGELA CODRUTA PODARIU MICROSCOPIC ASSESSMENT OF THE ENAMEL ETCHING PATTERN ACCORDING TO DIFFERENT ETCHING TIMES USING ORTHOPHOSPHORIC ACID GELS The aim of our study was to compare micro-morphological changes in enamel surfaces after etching for 60 or 120 s by 37% phosphoric acid gels. Eighteen extracted, not carious human teeth with sound buccal surfaces were obtained, thoroughly cleaned with a water slurry of pumice powder, with a soft rubber prophylaxis cup rotating at low speed and stored in saline at room temperature. After the teeth were sectioned longitudinally in mesio-distal direction using a low-speed bur, the enamel was etched with 37% phosphoric acid (Lucstar, Romania) for 60s and 120s with applicator sponges, rinsed with water and sprayed with air for 15 s, and dried for another 15 s. Each section was evaluated under the microscope and photomicrographs were taken of representative areas that were most often observed using statistical analysis. The enamel surface etched with 37% phosphoric acid gels for 60 and 120 s showed similar etching patterns. No evident morphological differences were observed in the type of enamel etching patterns when treated with 37% phosphoric acid gels for 60 and 120 s. However, etching with 37% phosphoric acid gel for 60 s resulted in a partial removal of the prism core and the micro-morphological characteristics of the enamel surface approached those produced by 37% phosphoric acid gels used for 120 s. Phosphoric acid gel used at concentrations of 37% produced similar micro-morphological etching patterns on enamel surfaces after 60 or 120 s of application.