Hygroscopic dimensional changes of self-adhering and new resin-matrix composites during water sorption/desorption cycles.
OBJECTIVE
To study hygroscopic dimensional changes in new resin-matrix composites during water sorption/desorption cycles.


METHODS
Five materials were examined: a self-adhering flowable composite: Vertise® Flow (VF), a universal composite: GC Kalore (GCK), two micro-fine hybrid composites: GC Gradia Direct Anterior (GDA) and GC Gradia Direct Posterior (GDP), and a posterior restorative composite: Filtek® Silorane (FS). Five disk-shaped specimens of each material were prepared (15 mm diameter × 2 mm thickness) according to ISO 4049. The mean diameter of each specimen was measured by a custom-built laser micrometer (to a resolution of 200 nm) periodically over 150d water immersion and 40d recondition periods at (37 ± 1)°C. Perspex controls were used. Data analysis was performed by repeated measures ANOVA, one-way ANOVA and Tukey's post hoc test (p<0.05).


RESULTS
Differences in hygroscopic expansion were found for all test materials during sorption, ranging from 0.74% (± 0.05) for FS to 4.82% (± 0.13) for VF. The differences were significant for all materials (p<0.001), except between GCK and GDA. The mathematical relationship between diametral expansion and square root of time was non-linear. VF exhibited significant dehydration shrinkage.


CONCLUSIONS
The silorane composite FS had the lowest hygroscopic expansion. The extent of compensation of polymerization shrinkage by hygroscopic expansion depends on materials, specimen dimensions and time-scale. So the clinical situation must be taken into consideration in the application of these findings.
Department of Prosthodontics, School of Stomatology, Capital Medical University, Tiantan Xili No. 4, Chongwen District, Beijing 100050, PR China.
Yong-jie
YJ
Wei
Nick
N
Silikas
Zhen-ting
ZT
Zhang
David C
DC
Watts
D000042:Absorption; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D058105:Polymerization; D012833:Siloxanes / Q000737:chemistry; D018709:Statistics, Nonparametric; D014867:Water; D017155:Wettability
D003188:Composite Resins; D008689:Methacrylates; D012833:Siloxanes; D014867:Water