Determination of Leached Monomers from Dental Resin-Matrix in Aqueous Environment

Objective: To determine leached monomers from dental resin matrix quantitatively and qualitatively according to different extract treatments using various analysis methods

Methods: Blended resin matrix with 49wt%-bisphenol A glycerolate dimethacylate(BisGMA), 30wt%-diurethane dimethacrylate(UDMA), 20wt%-triethyleneglycol dimethacrylate(TEGDMA), 0.75wt%-camphorquinone(CQ), and 0.25wt%-2-(dimethyl amino) ethyl methacrylate(DMAEMA). All chemicals were purchased from Sigma-Aldrich Chemical Co.(St.Louis, MO, USA). Fabricated 120 specimens(15±0.1 mm in diameter and 1.5±0.1 mm in thickness) were light-cured(20 s) on each side. Put each specimen into each container, poured distilled water with the ratio of 6 cm²/mL, and stored them in each extract treatment.

Table. Twelve extract treatments according to time and temperature

Conditions
Temperature	Time
(37±2)°C (50±2)°C (70±2)°C (121±2)°C	(1±0.2) hr (24±2) hrs (72±2) hrs

To measure degree of conversion(DC%), scanned each specimen(32 times,4 cm^-1 resolution) at three conditions(before and after curing and after extract treatment) using Fourier transform infrared spectroscopy(FT-IR), integrated intensities of 1638 and 1720 cm^-1, and calculated DC%. Quantitative and qualitative analysis of leached monomers in solutions after extract treatments was carried out by HPLC(UV-detector:205 nm). To perform Knoop hardness, applied an indenter(50 g load,20 s dwell time) onto the specimen before and after each extract treatment. All data were statistically analyzed(two-way ANOVA, Tukey’s test, p<0.05, n=10).

Results: DC% was significantly increased as time increased except interaction of 1-hr and 24-hr groups(p<0.05). BisGMA in solution was significantly decreased as temperature increased except interaction of 70℃-group and 121℃-group, and increased as time increased except interaction of 1-hr and 24-hr groups, but UDMA, TEGDMA and methacrylic acid(MA) in solution were significantly increased as temperature and time increased(p<0.05). Surface hardness was significantly increased in order of 72-hr, 1-hr and 24-hr groups(p<0.05).

Conclusion: According to increasing temperature and time, DC% and leached monomers except bisGMA in solution were increased in that uncured monomers were gradually extracted.

Acknowledgement: This work was supported by the Korea Science and Engineering Foundation(KOSEF) grant funded by the Korea government(MOST)(No. R13-2003-013-02001-0).