title: Effects of surface finish on indentation modulus and hardness of dental composite restoratives.
abstract: OBJECTIVE
  The depth-sensing micro-indentation testing was recently introduced for the characterization of dental composites. One of the critical issues raised was the possible influence of surface finish on material properties. The aim of this study was to investigate the effects of surface finish on the indentation modulus and micro-hardness of resin-based dental composite materials.
  
  
  METHODS
  The materials used included minifill (Z100, 3M ESPE), microfill (A110, 3M ESPE) and poly-acid modified (F2000, 3M ESPE) composites. The specimens were polished successively using SiC grinding papers of different grit size and diamond suspensions to achieve varying surface roughness. The arithmetic mean of the roughness (R(a)) was measured using profilometry. In the depth-sensing micro-indentation test, specimens (n=7) were indented to 10N with Vickers indenter and the load-displacement (P-h) data was obtained using a universal testing system. The indentation modulus (E(in)) and hardness (H) were then computed using the developed analytical solutions. Data was analyzed using ANOVA/post-hoc Scheffe's test at significance level 0.05.
  
  
  RESULTS
  The polished specimens had surface roughness ranging from 0.02 to 0.81 microm. The roughness of F2000 was significantly higher than A110 and Z100. The E(in) and H for Z100 ranged from 14.02 to 14.83GPa and 1.18 to 1.27 GPa, respectively. E(in) for F2000 and A110 ranged from 12.25 to 13.82 GPa and 5.26 to 5.52 GPa and hardness ranged from 0.89 to 0.98 GPa and 0.52 to 0.55 GPa, respectively.
  
  
  CONCLUSIONS
  The indentation modulus and hardness of dental composite restoratives were independent of the surface finish provided indenter penetration is sufficiently deep (h(max)/R(a)>30).
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, National University of Singapore, 5 Lower Kent Ridge Road, Singapore 119074, Singapore. rsdcsm@nus.edu.sg
authors.forename: S M
authors.initials: SM
authors.lastname: Chung
authors.forename: A U J
authors.initials: AU
authors.lastname: Yap
mesh_terms: D020770:Compomers; D003188:Composite Resins / Q000737:chemistry; D003775:Dental Polishing; D003793:Dental Restoration, Permanent; D004548:Elasticity; D005899:Glass Ionomer Cements; D006244:Hardness; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D012822:Silicon Dioxide; D013499:Surface Properties; D015040:Zirconium
chemical_list: D020770:Compomers; D003188:Composite Resins; C118368:F2000 cement; C452225:Filtek A110 composite resin; D005899:Glass Ionomer Cements; C083568:Z100 composite resin; D012822:Silicon Dioxide; D015040:Zirconium