Aluminum Bonded to Dental Enamel with Ultrasonic Energy: Thermal Stability

¹ Waldemar Medical Research Foundation, Woodbury, New York

A reliable method of fastening appliances to dental enamel demands stability over the temperature ranges encountered in the oral cavity. Aluminum bonded directly to dental enamel, using ultrasonic energy, formed bonds of high shear tensile strength that did not require adhesive or mechanical retainers. The coefficient of expansion of aluminum (25.5° x 10^-6/ C.) was more than twice as great as that of dental enamel (11.4° x 10^-6/C.). The temperature shock stability of ultrasonic bonds must be greater than the temperature changes encountered in the oral cavity. Rapid temperature changes through a range of 16° to 45°C. occur during ingestion. Ultrasonic bonds were tested by temperature cycling, consisting of immersion in a water bath at 90°C. for 3 minutes, succeeded immediately by immersion in ice water at 40°C. for 3 minutes and a return to room temperature. Bonds were shear tested at room temperature. Despite stresses set up at the interface of the bond during temperature cycle, ultrasonic bonds survived ten cycles without degradation of performance. Ultrasonic bonds demonstrated thermal stability for these test conditions.