title: The impact of resin-coating on sub-critical crack extension in a porcelain laminate veneer material.
abstract: Characterisation of the interaction between crack extension, crack stabilisation and stress/strain relaxation in the polymeric matrix, the interplay between stress corrosion cracking and the mechanical response of a resin-based luting adhesive within a surface defect population could extend PLV restoration longevity by optimising cementation protocols. The aim was to investigate the influence of stress corrosion cracking and the viscoelastic behaviour of a resin-based luting adhesive independently by controlling the environmental conditions operative during test specimen fabrication.
  
  
  
  The effects of stress corrosion at ceramic crack tips and potential viscoelastic responses to loading of the resin-coated impregnating cracks were isolated. Resin-coated feldspathic ceramic test specimens were fabricated in ambient humidity or following moisture exclusion. Bi-axial flexure strengths of groups (n = 20) were determined at constant loading rates of 2.5, 10, 40, 160 or 640 N/min and data was compared with uncoated controls. Fractographic analyses were performed on all fractured test specimens.
  
  
  
  Resin-cement coating resulted in significant ceramic strengthening in all conditions tested (p < 0.01). A two-way ANOVA demonstrated that the exclusion of moisture during resin- coating significantly increased mean BFS (p<0.01) but post-hoc Tukey tests identified that moisture exclusion resulted in significant increases in BFS values only at intermediate loading rates with no significant differences observed at either the fastest or slowest loading rates (640 and 2.5 N/min, respectively).
  
  
  
  Mechanical reinforcement of PLV materials by resin-cement systems is yet to be optimized. The viscoelastic behavior of the resin-cement itself can influence the magnitude of reinforcement observed and sub-critical crack growth.
authors.affiliation: Biomaterials Unit, University of Birmingham, School of Dentistry, 5 Mill Pool Way, Birmingham B5 7EG, UK.
authors.forename: Xu
authors.initials: X
authors.lastname: Cao
authors.affiliation: Materials Science Unit, Dublin Dental University Hospital, Lincoln Place, Dublin 2, Ireland.
authors.forename: Garry J P
authors.initials: GJP
authors.lastname: Fleming
authors.affiliation: Biomaterials Unit, University of Birmingham, School of Dentistry, 5 Mill Pool Way, Birmingham B5 7EG, UK; University of Alberta, School of Dentistry, Edmonton, AB, T6G 1C9, Canada. Electronic address: o.addison@bham.ac.uk.
authors.forename: Owen
authors.initials: O
authors.lastname: Addison
mesh_terms: D001840:Dental Bonding; D003764:Dental Materials; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D008422:Materials Testing; D018583:Pliability; D019279:Resin Cements; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D003764:Dental Materials; D019279:Resin Cements; D003776:Dental Porcelain
keywords: Cement; Ceramic; Strength; Stress-corrosion; Veneer