REPAIRABILITY OF A POLYACID-MODIFIED COMPOSITE RESIN

The purpose of this study was to evaluate the effect of time and surfa ce treatment resulting shear bond strength polyacid-modified composite resin restorative material (VariGlass VLC), Seventy-two specimens of VariGlass were prepared in cavities (2 mm at 7 mm) cut into acrylic re sin cylinders. The specimens were then divided into three groups of 24 . For each of the three groups, 12 of the specimens were repaired 5 mi nutes after the cavities were initially filled, while 12 specimens wer e repaired 1 week after the initial fill. The VariGlass surfaces were treated in one of the following ways: no treatment; primer (30 seconds ) and adhesive (light activated for 10 seconds); or 37% phosphoric aci d etchant (30 seconds), primer (30 seconds), and adhesive (light activ ated for 10 seconds). Repairs were made using a split polytetrafluoroe thylene mold (3 mm x 5 mm) mounted over the exposed VariGlass surface. After bonding a cylinder of VariGlass to the treated surfaces, the sp ecimens were thermocycled 500 times (5 degrees C and 55 degrees C wate r baths), stored in distilled water for 1 week, and loaded to failure in shear at 0.5 mm/min. Data were analyzed using two-way ANOVA and a S tudent-Newman-Keuls multiple comparison test. Results indicated that t he bond strength of specimens repaired at 5 minutes was significantly higher when no surface treatment was used prior to repair. Bond streng th of specimens repaired at 1 week was unaffected by surface treatment . Time of repair significantly affected the no-treatment and the prime r-adhesive groups.