title: The relationship between cyclic hygroscopic dimensional changes and water sorption/desorption of self-adhering and new resin-matrix composites.
abstract: OBJECTIVE
  This study evaluated the relationship between mass changes and hygroscopic dimensional changes during water sorption/desorption cycles in new resin composites.
  
  
  METHODS
  A silorane posterior composite (Filtek(®) Silorane, FS), two micro-fine hybrid composites (GC Gradia Direct Anterior, GDA; GC Gradia Direct Posterior, GDP), a universal composite (GC Kalore, GCK), and a self-adhering flowable composite (Vertise(®) Flow, VF) were evaluated. 25 (n=5) disk specimens (15mm×2mm) were prepared according to ISO 4049. Water sorption was measured gravimetrically. Hygroscopic expansions were measured by a laser micrometer regularly during 150 d water storage and 40 d recondition periods, all at 37°C. Data were analyzed by repeated measures ANOVA, one-way ANOVA and Tukey's post hoc test (p<0.05).
  
  
  RESULTS
  Mass changes after 150 d water immersion ranged from 0.68% (±0.02) for FS to 2.83% (±0.11) for VF and the corresponding hygroscopic expansions were from 0.74% (±0.05) for FS to 4.79% (±0.18) for VF. The differences were significant for all materials (p<0.001), except mass changes between GCK and GDP, as well as hygroscopic changes between GCK and GDA. The relationship between hygroscopic expansions and mass changes was initially non-linear and then tended toward linear behavior. But at the late stage of water sorption the hygroscopic expansion of GCK and VF was slightly sigmoidal with respect to their mass changes.
  
  
  CONCLUSIONS
  Relationships between hygroscopic expansion and mass change were determined for some diverse resin-matrix composites. The initial non-linearity for all materials suggests a lower expansion rate due to occupancy of internal free volume by water ingress. The silorane composite FS showed statistically the lowest mass change and hygroscopic dimensional change.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Capital Medical University, Beijing, PR China. weiyongjiegg@163.com
authors.forename: Yong-Jie
authors.initials: YJ
authors.lastname: Wei
authors.forename: Nick
authors.initials: N
authors.lastname: Silikas
authors.forename: Zhen-Ting
authors.initials: ZT
authors.lastname: Zhang
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D065966:Absorption, Physicochemical; D000327:Adsorption; D000465:Algorithms; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007834:Lasers; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D062047:Silorane Resins / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C470230:Gradia; D008689:Methacrylates; D011140:Polyurethanes; D062047:Silorane Resins; C555513:silorane composite resin; C581746:vertise flow; D014867:Water; C029824:urethane dimethacrylate luting resin
keywords: DX-511; Desorption; GPDM; Hygroscopic expansion; Resin composite; Silorane; UDMA; Water sorption