24-HOUR SHEAR BOND STRENGTH OF METAL ORTHODONTIC BRACKETS BONDED TO PORCELAIN USING VARIOUS ADHESION PROMOTERS

Clinically, orthodontists are often faced with the difficulties of bon ding to porcelain crowns, veneers, or bridges. Traditional methods of dealing with this are often time-consuming and generally esthetically unacceptable to patients. Current interest involves the use of organos ilane primers with or without NTG-GMA and BPDM resins to aid in chemic ally bonding porcelain with traditional orthodontic adhesives. This st udy compared the bond strength of three types of adhesion promoters: O rmco Porcelain Primer (OR) (Ormco Corp., Glendora, Calif,), All-Bond2 (AB2) (Bisco Dental Products, Inc., Itasca, III.), and Scotchprime Cer amic Primer (SP) (3M, St, Paul, Minn,) with two orthodontic adhesives: Phase II (Reliance, Inc., Itasca, III.) and Rely-a-bond (Reliance, In c., Itasca, III.). Eighty ceramometal samples were fabricated and hydr ated for 1 week in distilled water before bonding. Next, the samples w ere etched with 2.5% HF acid for 90 seconds, rinsed and upper central incisor metal orthodontic brackets were bonded with the various primer s and adhesives. After 24 hours they were sheared off with an MTS mach ine at a rate of 0.5 mm/min, and the bond strength was measured. The m ean shear bond strengths (MPa) with Phase II were as follows: Control 0.44 (sigma = 0.22), AB2 8.40 (sigma = 3.61), OR 13.31 (sigma = 5.79), SP 13.53 (sigma = 3.34). With Rely-a-bond, the shear bond stengths we re Control 0.41 (sigma = 0.67), AB2 4.34 (sigma = 1.88), OR 9.73 (sigm a = 4.58), and SP 12.40 (sigma = 3.05). An analysis of variance and St udent-Newman-Keuls tests were run on the data, and it was found that t here was a significant difference between the types of resin/primer co mbinations and the bond strength obtained. Overall, there were signifi cant differences between all the primer/adhesive combinations except f or Scotchprime and Ormco primers that were not statistically different . Scotchprime did tend to have more consistent results on the basis of standard deviations alone. Furthermore, Phase II resin resulted in hi gher bond strengths but consequently increased the incidence of porcel ain fracture on debonding.