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L. LASSILA,
and P. VALLITTU, Univ. of Turku, Finland
Objectives: During the last few years fiber reinforced
composite (FRC) root canal post has been introduced to market.
However, there still remains question of possible problem with the
adhesion between highly crosslinked polymer matrix of FRC-posts
and filler-composite. An alternative to resolve this problem FRC
post simultaneously with the surrounding filler composite. The aim
of this study was to determine the degree of conversion (DC) of
resin matrix of FRC post polymerzed by light initiation in a
simulated root canal.
Methods: Four different lengths (7,12,18,24 mm) of
cylinders were used as a model of root canal. Two groups of
cylinders where used: cylinders in Groups 1 were filled only with
dimethacrylate resin (StickResin, StickTech, Finland) only.
Cylinders in Groups 2 were filled with continuous unidirectional
E-glass fibers (StickClassics) that have been further impregnated
with resin. Specimens were light-cured (Elipar, ESPE, Germany) for
40 sec from the top of the cylinders. The bottom of the cylinder
was fixed on FTIR/ATR (Fourier Transform Infrared
spectroscopy/Attenuated Total Reflectance) (Spectrum One, Perkin
Elmer) sample accessory and polymerisation process was analysed.
Degree of conversion (DC%) was calculated from the aliphatic C=C
peak at 1638 cm-1, normalised against the aromatic C=C
peak at 1582 cm-1: DC% = (1-C/U)x100%, where
C=absorption peak of the cured specimen, where U=absorption peak
of the uncured specimen. Spectra of the sample was recorded every
2.5 min up to 5 min. Each IR-spectra was recorded with 8
scans using a resolution of 4 cm-1.
Results:
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DC%/Length of cylinder(mm)
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Group
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7
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12
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18
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24
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1. Resin
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69.2
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67.3
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63.9
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57.0
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2. Resin+glass fibers
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66.8
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66.0
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59.0
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56.1
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Regression line was fitted into both models with regression
coefficients of 0.946 (resin, p=0.027) and 0.938 (fibers+resin,
p=0.031).
Conclusions:
This
in vitro study showed that sufficient degree of conversion could
be achieved by exposing light from other end of glass fiber post.
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