title: Effects of coronal substrates and water storage on the microhardness of a resin cement used for luting ceramic crowns.
abstract: Composite resin and metallic posts are the materials most employed for reconstruction of teeth presenting partial or total destruction of crowns. Resin-based cements have been widely used for cementation of ceramic crowns. The success of cementation depends on the achievement of adequate cement curing.
  
  
  OBJECTIVE
  To evaluate the microhardness of Variolink® II (Ivoclar Vivadent, Schaan, Liechtenstein), used for cementing ceramic crowns onto three different coronal substrate preparations (dentin, metal, and composite resin), after 7 days and 3 months of water storage. The evaluation was performed along the cement line in the cervical, medium and occlusal thirds on the buccal and lingual aspects, and on the occlusal surface.
  
  
  METHODS
  Thirty molars were distributed in three groups (N=10) according to the type of coronal substrate: Group D- the prepared surfaces were kept in dentin; Groups M (metal) and R (resin)- the crowns were sectioned at the level of the cementoenamel junction and restored with metallic cast posts or resin build-up cores, respectively. The crowns were fabricated in ceramic IPS e.max® Press (Ivoclar Vivadent, Schaan, Liechtenstein) and luted with Variolink II. After 7 days of water storage, 5 specimens of each group were sectioned in buccolingual direction for microhardness measurements. The other specimens (N=5) were kept stored in deionized water at 37ºC for three months, followed by sectioning and microhardness measurements.
  
  
  RESULTS
  Data were first analyzed by three-way ANOVA that did not reveal significant differences between thirds and occlusal surface (p=0.231). Two-way ANOVA showed significant effect of substrates (p<0.001) and the Tukey test revealed that microhardness was significantly lower when crowns were cemented on resin cores and tested after 7 days of water storage (p=0.007).
  
  
  CONCLUSIONS
  The type of material employed for coronal reconstruction of preparations for prosthetic purposes may influence the cement properties.
authors.affiliation: Department of Prosthodontics, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
authors.forename: Luana Menezes de
authors.initials: LM
authors.lastname: Mendonça
authors.affiliation: Department of Prosthodontics, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
authors.forename: Luiz Fernando
authors.initials: LF
authors.lastname: Pegoraro
authors.affiliation: Department of Prosthodontics, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
authors.forename: Marcos Daniel Septímio
authors.initials: MD
authors.lastname: Lanza
authors.affiliation: Department of Prosthodontics, Sagrado Coração University, Bauru, SP, Brazil.
authors.forename: Thiago Amadei
authors.initials: TA
authors.lastname: Pegoraro
authors.affiliation: Department of Oral Biological and Medical Sciences Division of Biomaterials, Frontier Clinical Research Centre, Faculty of Dentistry, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Ricardo Marins de
authors.initials: RM
authors.lastname: Carvalho
mesh_terms: D000704:Analysis of Variance; D002484:Cementation / Q000379:methods*; D002516:Ceramics / Q000737:chemistry*; D003442:Crowns; D006245:Hardness Tests; D006801:Humans; D008422:Materials Testing; D008488:Medical Illustration; D012016:Reference Values; D015203:Reproducibility of Results; D019279:Resin Cements / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D019279:Resin Cements; D014867:Water; C103502:Variolink