Comparison of materials and methods used in acid etch restorative procedures.

The retentive strengths of restorations made of various composite materials were tested with variations in preparations and phosphoric acid concentrations. The interrelationship of tooth preparation, concentration of acid conditioner, and retention of restorative materials used in the acid etch technique was investigated. Seventy-two extracted maxillary central incisors were separated into groups. Variables used in the comparison included scalloped or flat preparations and 25%, 50%, and 75% concentrations of phosphoric acid. Acrylic and composite resins, one of which was polymerized with ultraviolet light, were used for the restorations. The retentive strength of the restorations was tested and analyzed statistically. The ultraviolet-light-polymerized material tested was shown to have the strongest bonds, and scalloping of the preparation generally enhanced bonding. Retention of the restorations was affected by the concentration of phosphoric acid used.