title: [Influence of long-term water storage on the physical and chemical properties of four different dental cements].
abstract: OBJECTIVE
  To evaluate and compare the physical and chemical properties of four different dental cements under long-term water storage.
  
  
  METHODS
  A glass-ionomer cement (A:Fuji I), a resin reinforced glass-ionomer (B: Fuji Plus), a self-adhesive resin cement (C:G-Cem), and an etch & rinse resin cement (D: Duolink) were taken as samples. According to ISO 4049, water sorption and solubility of four resin cements under different storage times (1 week, 1, 3, 6 and 12 months) were calculated (n = 5), meanwhile their surface Knoop micro hardness values were measured.
  
  
  RESULTS
  Surface cracks were detected on sample B and C after 12 months. Sample A was fragmentized after 6 months. Sample B showed significantly lower surface hardness after 12 months than it did after the first 24 hours of water storage (P < 0.05). Sample D showed significantly lower water sorption than other cements did at all exam time point. The highest water sorption values were observed in Sample D after 1 month [(40.8±2.5) µg/mm(3)], in Sample B after 3 months [(551.3±22.5) µg/mm(3)], in Sample C after 12 months [(147.5±8.3) µg/mm(3)]. The highest solubility values were detected in Sample B after 3 months [(105.3±10.5) µg/mm(3)], in Sample C after 12 months [(79.3 ± 6.2) µg/mm(3)], and in Sample D after 12 months [(23.9 ± 6.9) µg/mm(3)].
  
  
  CONCLUSIONS
  Among the four types of cements, the etch & rinse resin cement showed the best stability of physical and chemical properties under long-term water storage.
authors.affiliation: Department of Prosthodontics, Institute and Hospital of Stomatology, Nanjing University Medical School, Nanjing 210008, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Prosthodontics, Institute and Hospital of Stomatology, Nanjing University Medical School, Nanjing 210008, China. Email: mengsoar@nju.edu.cn.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Meng
mesh_terms: D000269:Adhesives; D003738:Dental Cements; D005899:Glass Ionomer Cements; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D019279:Resin Cements; D014867:Water
chemical_list: D000269:Adhesives; D003738:Dental Cements; D005899:Glass Ionomer Cements; D019279:Resin Cements; D014867:Water; C084541:Fuji glass-ionomer lining cement; C095998:Adhesive cement