title: Effect of polymerisation and ageing on the incremental bond strength of ormocer-based dental materials.
abstract: OBJECTIVE
  The aim of this study was to investigate the effect of polymerisation and ageing on the incremental bond strength (IBS) and fracture mechanics of experimental and commercial, well established ormocer-based materials.
  
  
  METHODS
  An experimental dimethacrylate-diluent-free ormocer was compared with two commercial products (Admira (VOCO); Ceram X Duo (Dentsply)). For Ceram X Duo, the strength between dentin shades (DD) and between dentin and enamel shades (DE) was measured. In order to simulate clinical conditions, when a direct access to the composite surface is impeded, the curing unit was applied at different distances (1, 3 or 6 mm) from the sample's surface. IBS was measured after the samples were stored in distilled water (24 h/37 °C) and after ageing (5,000 cycles between 5 and 55 °C followed by storage (28 days/37 °C) in distilled water). Additionally, the degree of cure (DC) was measured in a thin film (~50 μm). A multivariate analysis, an additional one-way ANOVA with Tukey HSD post hoc test (α = 0.05), an independent t test (α = 0.05), and Weibull statistics were used to assess the results.
  
  
  RESULTS
  After 24 h, the values for IBS were statistically the same. Differences revealed after ageing, whereby the experimental material achieved the significant highest and Admira the lowest results. By evaluating after 24 h and after ageing, the experimental material obtained the smallest Weibull modulus "m". The predominant breaking mechanism is cohesive, even though the number decreases in favour for the mixture and adhesive fractures after ageing. Clear differences arose with regard to DC. The experimental material reached considerably lower values (31.9-33.2 %) unlike Ceram X Duo (45.6-48.3 %) and Admira (52.9-58.8 %).
  
  
  CONCLUSIONS
  The IBS and the DC are far more dependent on the parameter filler volume percent and material than on the polymerisation distance.
  
  
  CONCLUSIONS
  A dimethacrylate-diluent-free ormocer matrix offers a better stability opposite ageing but achieves a lower DC and reliability.
authors.affiliation: Department of Restorative Dentistry, Dental School, Ludwig-Maximilians University, Goethestrasse 70, Munich, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Awad
authors.forename: Nicoleta
authors.initials: N
authors.lastname: Ilie
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D055115:Light-Curing of Dental Adhesives; D016014:Linear Models; D008422:Materials Testing; D008689:Methacrylates; D063225:Organically Modified Ceramics / Q000737:chemistry; D058105:Polymerization; D033081:Shear Strength; D012833:Siloxanes; D017550:Spectroscopy, Fourier Transform Infrared; D018709:Statistics, Nonparametric; D016019:Survival Analysis; D013997:Time Factors
chemical_list: C520091:CeramX; D003188:Composite Resins; D008689:Methacrylates; D063225:Organically Modified Ceramics; D012833:Siloxanes; C479084:admira