New method for the in vitro evaluation of dental alloy bonding systems

Statement of problem. Bonding systems are used in some fixed prosthetic dev ices with base alloys. However, different studies of the same dental alloy bonding agents, under similar circumstances, have yielded disparate results in bond strength testing. Purpose. This study compared directly 2 dental alloy bonding systems throug h a "duel" type of confrontation, which basically is a 2-way tensile force test. Material and methods. Ninety Wiron 88 base alloy cylinders (diameter of 8 m m length 15 mm) were sandblasted oil both sides with Al(2)0(3) powder (part icle size 50 mu m) during 10 seconds at an approximate distance of 5 mm, at an air pressure of 60 psi determined before sandblasting procedures, The s urface of each cylinder was cleaned from Al(2)0(3) powder with a strong bur st of oil-free air from a chairside air syringe. Thirty cylinders were rand omly assigned to 1 of 3 groups fur direct bond strength comparison: (1) Pan avia 21 to Panavia EX, (2) Panavia 21 to Metabond, or (3) Panavia 21 to a c ombination of a resin bonding agent plus Panavia. 21. Each group was compos ed of 10 specimens that used 3 cylinders for each specimen. Each side of th e sample cylinder received the same quantity of cement and 1 cylinder at a time was bonded to it. Cylinder alignment was verified with a Boley gauge d uring luting procedures. The bonded 3-piece block was held together fur 24 hours under a compressive force of 2 kg/cm(2) using a hydraulic press. Exce ss cement was removed with a brush, and the pertinent air sealant was appli ed to allow for autocuring of the cement. Specimens were later stored in wa ter at room temperature for 48 hours before thermocycling procedures. Each specimen was thermocycled for 100 cycles with a 5-minute dwelling time in w ater at 4 degrees C and 60 degrees C. Specimens were subject to tensile for ce testing until debonding in 1 of thr cylinders. Results. The opposing pull duel test (OPDT) showed that the Panavia ES fail ed (40.3 MPa) 10 of 10 duels against Panavia. 21, whereas Panavia 21 failed (49.7 MPa)9 of 10 duels against Metabond, and Panavia 21 failed (50.1 MPa) 10 of 10 duels against Photobond+Panavia 21. ANOVA revealed significant di fferences (P<.05) between PAN-EX group and MET and PHB+P21 groups. However, no significant differences were found between MET and PHB+P21 groups. Conclusion. The opposing pull duel test was a valid method to directly comp are bond strengths of 2 bonding systems to dental base alloys. There was a. small dispersion of the values er en though cement mixing and thickness va riables were difficult to control. Duel tensile testing provides meaningful information on the superiority of one bonding system over another in this controlled environment.