Properties of dental resins submitted to pH catalysed hydrolysis
Available online 26 September 2012
Abstract
Objectives
This
study evaluated the surface microhardness (SM) and roughness (SR)
alterations of dental resins submitted to pH catalysed degradation
regimens.
Methods
Thirty
discs of each TPH Spectrum (Dentsply), Z100 (3M-ESPE), or an unfilled
experimental bis-GMA/TEGDMA resin were fabricated, totaling 90
specimens. Each specimen was polymerized for 40 s, finished, polished,
and individually stored in deionized water at 37 °C for 7 days.
Specimens were randomly assigned to the following pH solutions: 1.0, 6.9
or 13, and for SM or SR evaluations (n = 5). Baseline
Knoop-hardness of each specimen was obtained by the arithmetic mean of
five random micro-indentations. For SR, mean baseline values were
obtained by five random surface tracings (Ra).
Specimens were then soaked in one of the following storage media at
37 °C: (1) 0.1 M, pH 1.0 HCl, (2) 0.1 N, pH 13.0 NaOCl, and (3)
deionized water (pH 6.9). Solutions were replaced daily. Repeated SM and
SR measurements were performed at the 3-, 7- and 14-day storage time
intervals. For each test and resin, data were analysed by two-way ANOVA
followed by Tukey's test (α = 0.05).
Results
There
was significant decrease in SM and increase in SR values of composites
after storage in alkaline medium. TPH and Z100 presented similar
behaviour for SM and SR after immersion in the different media, whereas
unfilled resin values showed no significant change.
Conclusion
Hydrolytic
degradation of resin composites seems to begin with the silanized
inorganic particles and therefore depend on their composition.
Significance
To accelerate composite hydrolysis and produce quick in vitro
microstructural damage, alkaline medium appears to be more suitable
than acidic medium. Contemporary resin composite properties seem to
withstand neutral and acidic oral environments tolerably well.
Comments