FLUORIDE PENETRATION INTO THE HYBRID LAYER FROM A DENTIN ADHESIVE

Purpose: To evaluate the in vitro microleakage of a new fluoride-conta ining dentin adhesive and to provide evidence for fluoride release fro m the adhesive and penetration into the dentin. Materials and Methods: Class V preparations with margins in enamel and dentin were made in t he buccal and lingual surfaces of six extracted human third molars. Si x preparations were restored with Scotchbond Multipurpose (SBMP)/Z100 composite and six with a new fluoride containing dentin adhesive (FB)/ Litefil composite. After aging for 30 days in water at 37 degrees C, t he teeth were stained with silver nitrate, sectioned and graded by two observers for leakage at the enamel and dentin margins. Selected FB s pecimens were examined in the scanning electron microprobe using WDS f or fluoride and EDS for calcium and phosphorous. Fluoride release into water from disks of FB adhesive was evaluated for up to 112 days usin g a specific ion electrode. Results: Fluoride leached from the adhesiv e at a decreasing rate with time. The final rate over 112 days was 0.0 2 ppm/day (0.2 mu g/cm(2)/day)e enamel and dentin margins was similar for both adhesives (Mann-Whitney U-test; P less than or equal to 0.05) . SEM evaluation showed the presence of a discontinuous hybrid layer o f 2-3 mu m. Fluoride was present within, but limited to, the hybrid la yer for the FB adhesive. The penetration of fluoride could only be con firmed in areas where leakage had occurred.