Bond strength of denture base resin to castable Fe-Pt magnets

Takayuki Aoki, DMD, PhD,(a) Chikahiro Ohkubo, DMD, PhD,(a) Hiroyuki Kouno, DMD,(a) Toshio Hosoi DDS, PhD,(a) Yasuhiro Tanaka, PhD,(b) and Ikuya Watanabe, DDS, PhD(c)

(a)Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan, (b)Department of Developmental and Reconstructive Medicine, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan, and (c)Department of Biomaterials Science, Baylor College of Dentistry, Texas A&M University System Health Science Center, Dallas, TX, USA

Purpose: The purpose of this study was to evaluate the bond strengths of denture base resin to a magnetic Fe-Pt alloy using four adhesive metal primers.
Materials and Methods: Disk patterns (7.5 mm diameter, 2.0 mm thick) were cast from a custom-made Fe-Pt ingot (Fe-69.4wt%Pt-0.6wt%Nb) in a high-frequency centrifugal casting machine. Aging at 600℃ was performed for five hours to obtain hard magnetic properties. After the adhesive surfaces were sandblasted with 50μm Al2O3, they were primed with Metal Primer II (MP), Meta Fast Bonding Liner (BL), New Meta Color INFIS Opaque Primer (IN), or Epricord Opaque Primer (EP). Denture base resin (Palapress Vario) was then polymerized according to the manufacturerユs instructions. After the specimens were immersed in 37℃ water for 24 hours (Baseline, TC0), the shear bond strengths (n=7) were measured at a crosshead speed of 0.5 mm/minute after 10,000 thermal cycles (TC 10,000 at 4℃ to 60℃). The data were statistically analyzed by ANOVA/ Scheffé’s test (_=0.05).
Results: MP and EP had significantly higher bond strengths (p<0.05) than BL and IN at TC0. Thermal cycling significantly (p<0.05) reduced the bond strengths using all the primers tested. However, the bond strength of EP was slightly less after thermal cycling than for the other three primers (MP, BL, IN).
Conclusion: The results of this in vitro study indicate that EP provides superior long-term bond strength when a cast Fe-Pt magnet is embedded in denture base resin. (Int Chin J Dent 2005; 5: 39-42.)
Clinical Significance: The use of Epricord Opaque Primer is recommended to obtain long-term clinical reliability when the denture base resin is bonded to cast Fe-Pt magnet.
Key Words: cast Fe-Pt magnet, denture base resin, metal primer, bond strength.