Effect of surface preparations on the repair strength of denture base resin

Hiroshi Shimizu, DDS, PhD,(a) Kenneth S. Kurtz, DDS,(b) Masaharu Yoshinaga, DDS,(a) Yutaka Takahashi, DDS, PhD,(a) and Tetsuya Habu, DDS, PhD(a)

(a)Division of Removable Prosthodontics, Department of Oral Rehabilitation, Fukuoka Dental College, Fukuoka, Japan, and (b)Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, NY, USA

Purpose: The objective of this study was to evaluate the effect of surface preparations on the repair bond strength of an acrylic denture base resin material.
Materials and Methods: Rectangular specimens (n = 80) were prepared with a heat processed denture base resin (Lucitone 199) and divided into five groups. Four sets of 16 specimens were cut in half, and the remaining one set was not cut and served as the reference group. The surface preparations for the cut specimens were; 1) without preparation, 2) application of dichloromethane, 3) air-abrasion with 50 μm alumina, and 4) alumina air-abrasion followed by application of dichloromethane. These four groups were repaired with an autopolymerizing acrylic repair resin (Repair Material). The specimens were immersed in 37°C water for either one-day or 30 days. Transverse strengths were determined with a three-point bending test.
Results: Repair bond strengths in MPa of the denture base material after one-day and 30 days were; 73.0 and 52.0 for group 1, 74.8 and 57.3 for group 2, 76.7 and 54.7 for group 3, and 76.3 and 64.9 for group 4, whereas transverse strengths of uncut group were 85.5 and 85.0. Of the four surface preparations assessed, group 4 showed the greatest 30-day bond strength, although reduction in bond strength after aging was remarkable and the value was inferior to that of uncut group (p<0.05).
Conclusion: Within the limitation of the current in vitro study, air-abrasion with 50 μm alumina followed by the application of dichloromethane was the most effective surface preparation for the denture base resin.
(Int Chin J Dent 2002; 2: 126-133.)

Clinical Significance
: Alumina air-abrasion combined with application of dichloromethane facilitates bond strength to a heat processed denture base resin material when the fracture site is repaired with an autopolymerizing acrylic repair resin.
Key Words: acrylic resin, alumina, denture base, dichloromethane, repair.