title: Factors influencing marginal cavity adaptation of nanofiller containing resin composite restorations.
abstract: OBJECTIVE
  The aim of this study was to investigate the effects of polymerization contraction, shrinkage stress and Young's modulus of nanofiller containing resin composites on early marginal adaptation of restorations in cavities.
  
  
  METHODS
  Six nanofiller containing and two reference resin composites were studied. Marginal gap widths of restorations in cylindrical 4.2mm wide and 1.5mm deep dentin cavities, non-bonded or bonded with a self-etch adhesive, and in Teflon cavities of same dimensions were determined 15 min after irradiation (n=8). Polymerization shrinkage strains were measured using the bonded-disk (n=8) and a strain gage method (n=8). For determination of contraction stress the composites (n=10) were bonded to and cured in Araldit molds using a photoelastic method. Flexural moduli of the restoratives were studied according to ISO specification 4049 (n=5). Statistical analysis was performed with one- and two-way ANOVA, Kruskal-Wallis ANOVA test and post hoc tests (p<0.05).
  
  
  RESULTS
  Only two nanofiller composites (Kalore, GC, Japan) and Venus Diamond (Heraeus Kulzer, Germany) showed consistently gap-free margins in bonded dentin cavities. The mean gap widths in non-bonded and in Teflon cavities were 6.1-12.8 and 14.1-25.5 μm, and linearly correlated (r(2)<0.85). Significant linear relationships were observed between strain, stress and marginal gap widths in non-bonded and Teflon cavities (p<0.01). Flexural moduli (15 min) were between 1.66 and 8.63 GPa.
  
  
  CONCLUSIONS
  Marginal cavity adaptation of restorations in bonded dentin cavities reflects complex interactions between adhesive bonding on the one hand, and polymerization contraction strain, stress and elastic modulus, on the other.
authors.affiliation: Advanced Biomaterials, Department of Restorative Sciences, Division of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Takahashi
authors.forename: Werner J
authors.initials: WJ
authors.lastname: Finger
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wegner
authors.forename: Andreas
authors.initials: A
authors.lastname: Utterodt
authors.forename: Masashi
authors.initials: M
authors.lastname: Komatsu
authors.forename: Bernd
authors.initials: B
authors.lastname: Wöstmann
authors.forename: Markus
authors.initials: M
authors.lastname: Balkenhol
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects; D003737:Dental Cavity Preparation; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D053761:Nanocomposites / Q000528:radiation effects; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry / Q000528:radiation effects; D018709:Statistics, Nonparametric; D014783:Viscosity
chemical_list: D003188:Composite Resins; D019279:Resin Cements; C477386:iBond