Penetration of the pulp chamber by carbamide peroxide bleaching agents on teeth restored with a composite resin

This in vitro study was performed to evaluate the effect of various concentrations of carbamide peroxide bleaching agents on the pulp chambers of teeth restored by a composite resin. Forty-nine human extracted anterior teeth were used. All the teeth were sectioned 3 mm apical of the cemento-enamel junction and the intracoronal tissue removed. The teeth were separated into the seven groups each containing seven teeth. Twenty-eight teeth were used as controls (groups I-IV), standardized cavities were prepared with the remaining 21 teeth (groups V, VI, VII), and restored with a hybrid composite resin (XR Herculite). Acetate buffer was placed in the pulp chamber to absorb and stabilize any peroxide that might penetrate. Group I was exposed only to distilled water. Groups II and V were applied with 10% CP (Contrast PM), groups III and VI were applied with 15% CP (Contrast PM), groups IV and VII were applied with 35% CP (Quik Start) and left for 30 min at 37 degrees C. Then, the acetate buffer solution in the pulp chamber of each tooth was removed and the chamber was then rinsed twice with 100 ml of distilled water. The contents then had leucocryctal violet and enzyme horseradish peroxidase added. The optical density of the resulting blue solution was determined spectrophotometrically, and was converted into microgram equivalents of hydrogen peroxide. A higher level of bleaching agent penetrated into the pulp chamber in the restored teeth than in the sound teeth.