An in vitro evaluation of bond strength of three glass ionomer cements Valerie Bowser Fajen, DDS, MS," Manville G. Duncanson, Jr., DDS, PhD, b Ram S. Nanda, DDS, MS, PhD, c G. Frans Currier, DDS, MSD, MEd, ~ and Padmaraj V. Angolkar, BDS, MDS. ° Oklahoma City, Okla. The purpose of this study was to determine the bond strength of three commercially available glass ionomer cements when used to bond mesh-backed medium twin (0.130 inch) brackets to enamel surface. Three different enamel surface conditions, which included use of pumice, pumice and polyacrylic acid, and pumice followed by acidulated phosphate fluoride, were also tested to determine their effect on the bond strength. In addition, bond strength of one composite resin was compared with those of glass ionomer cements. The teeth were bonded with all the materials according to manufacturers' instructions. Each specimen was embedded in Super-Die with the bonded facial surface exposed. A surveyor was used to align the teeth in the stone uniformly for all specimens. A special bracket holder was used to hold the brackets precisely under the wings during debonding. An Instron universal testing machine was used to measure the force required for bond failure. To simulate oral conditions, the direction of pull was so designed that it included an element of torsional stress along with tensile force. The findings indicate that a large variation existed between the bond strengths of all materials tested. The bond strength of glass ionomer cements was significantly less than that composite resin. However, the bond strength of at least one glass ionomer cement appears to be adequate for clinical use. The different surface preparation before bonding did not significantly affect the bond strengths of glass ionomer cements. Further investigation is required to test the bond strengths of glass ionomer cements clinically. (AM J ORTHODOENTOFAC ORTHOP1990;97:316-22.) Bonding of brackets has become a routine orthodontic procedure in fixed appliance therapy. Var- ious bonding agents were developed after the introduc- tion of the acid-etch technique by Buonocore.' These included primarily the acrylic (methylmethacrylic) and the diacrylic (bis-GMA) systems, 2 and the literature is replete with many investigations describing the prop- erties of these materials, as reviewed by Zachrisson. 3 The glass ionomer cements were introduced in 1972, 4 primarily as luting agents and as direct restor- ative material with their unique property of being able to chemically bond with both enamel and dentin. These cements are also recognized for their ability to bond From the University of Oklahoma College of Dentistry. This report is based on a thesis submitted to the faculty of Graduate Studies, University of Oklahoma College of Dentistry, in partial fulfillment of the requirements for the degree of master of science. 'Former Graduate Resident, Department of Orthodontics. ~Professor and Chairman, Department of Dental Materials. 'Professor and Chairman, Department of Orthodontics. dAsscciate Professor, Department of Orthodontics. 'Visiting Assistant Professor, Department of Orthodontics. 8/1/12521 316 with some metals, and they have another unique prop- erty of being able to release fluoride ions. 5'6 These qual- ities prompted some investigators to evaluate their use in orthodontics. TM The retention of bands cemented with glass ionomer cements is reported to be superior to those cemented with zinc phosphate cements. ~3"t4 Similarly, decalcification under these bands cemented with glass ionomer cements is reported to be consid- erably less. t2 White ~° evaluated the glass ionomer ce- ments for bonding of brackets and concluded that the main advantages were prevention of decalcification due to fluoride ion release and easier debonding. Similarly, Cook and Youngson tt studied the bond strength of one glass ionomer cement and concluded that the bond strength of the cement tested was significantly less than that of a composite resin. Although the present bonding systems with the acid- etch technique may be adequate for routine clinical use, the clinicians are becoming increasingly aware of a few drawbacks of these materials. These include loss of enamel during etching and debonding, ~'~7 difficulty in debonding, ~8 and decalcification around the brack- ets. 19"2° In these regards, the glass ionomer cements are