Dimensional accuracy of autopolymerized resin applied using the brush-on technique

Shigeru Hanatani, DMD, PhD, Naoyuki Shibuya, DMD, PhD, Ema Muraishi, DMD, Daigo Hayashi, DMD, Tomoko Osada, DMD, PhD, Yohei Sato, DMD, PhD, Chikahiro Ohkubo, DMD, PhD, and Toshio Hosoi, DDS, PhD

Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan

Purpose: The brush-on technique was developed to compensate for polymerization shrinkage. In this study, we assess the dimensional accuracy of autopolymerized resin applied using a brush-on technique.
Materials and Methods: Each of five autopolymerized resins, Unifast II (GC), Unifast Trad (GC), Provinice (Shofu), Metafast (Sun Medical), and Miky (Nissin), was applied three times inside a ceramic cylinder (10 mm internal diameter; 5 mm width) using a brush-on technique (horsehair resin brush, Seiundo). As controls, the five resins were applied inside cylinders after the polymer and monomer were mixed at 0.5 mL/g for 10 s. After polymerization, the cylinders were cut into 3-mm wide pieces using a precision cutting machine. The maximum gaps between the ceramics and resins were measured using a scanning electron microscope at a magnification of x500. The dimensional accuracy (n=5) was assessed as the shrinkage percentage (the gaps divided by the internal diameter of the tubes). The data were analyzed by ANOVA/Tukey’s test (α=0.05).
Results: : Excluding Metafast, the brush-on technique differed significantly from the controls (p<0.05). Using the brush-on technique, Metafast had the greatest shrinkage, and Unifast had the lowest shrinkage. However, there was no significant difference among all the resins tested (p>0.05).
Conclusion: The dimensional accuracy of the autopolymerized resin using the brush-on technique was better than that of the conventionally mixed polymer and monomer because the polymer and monomer ratio using the brush-on technique was lower and polymerization shrinkage was minimized due to the brush-on technique. (Int Chin J Dent 2009; 9: 9-13.)

Key Words: autopolymerized acrylic resin, brush-on technique, dimensional accuracy, polymerizationshrinkage.