title: The impact of montmorillonite clay addition on the in vitro wear resistance of a glass-ionomer restorative.
abstract: OBJECTIVE
  The in vitro wear resistance of a glass-ionomer (GI) restorative ChemFil Superior (Dentsply DeTrey, Kanstanz, Germany) reinforced with either a pristine calcium montmorillonite (Ca-MMT) or an organically modified 12-amino-dodecanoicacid treated montmorillonite (ADA-MMT) clay was evaluated to investigate the potential of MMT reinforced GI restoratives as posterior filling materials.
  
  
  METHODS
  The wear resistance of a GI restorative reinforced with 0.5-2.5 wt.% Ca-MMT and ADA-MMT was assessed for groups of four disc-shaped specimens using the OHSU oral wear simulator operating at 20 N abrasion and 90 N attrition forces for 50,000 cycles at a frequency of 1 Hz in the presence of a poppy seed and PMMA micro-sphere slurry. The wear facet of each specimen was quantified by measuring the mean wear depth and mean volumetric wear in the abrasion (40-60% of wear facet) and attrition (80-90%) regions in conjunction with the mean total wear depth and mean total volumetric wear.
  
  
  RESULTS
  The addition of Ca-MMT clay resulted in a significant increase in the mean total volumetric wear and mean total wear depth of the GI restorative as the concentration of clay was increased utilising the one-way ANOVA and Tukey's test comparisons at a 95% significance level. When ADA-MMT clay was added to the GI no significant differences in mean total volumetric wear and mean total wear depth were evident (P<0.05).
  
  
  CONCLUSIONS
  The addition of Ca-MMT clay to the GI restorative resulted in a significant decrease in the in vitro wear resistance. ADA-MMT clay additions to the powder element of the GI restorative did not significantly enhance the in vitro wear resistance.
authors.affiliation: Materials Science Unit, Division of Oral Biosciences, Dublin Dental School and Hospital, Trinity College Dublin, Dublin 2, Ireland. adam.dowling@dental.tcd.ie
authors.forename: Adam H
authors.initials: AH
authors.lastname: Dowling
authors.forename: Garry J P
authors.initials: GJ
authors.lastname: Fleming
mesh_terms: D000704:Analysis of Variance; D001546:Bentonite / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D019245:Compressive Strength; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D017276:Friction; D005899:Glass Ionomer Cements / Q000737:chemistry*; D007850:Lauric Acids / Q000737:chemistry; D008422:Materials Testing
chemical_list: C501420:Chemfil Superior; D005899:Glass Ionomer Cements; D007850:Lauric Acids; D001546:Bentonite; C046049:12-aminododecanoic acid; D002118:Calcium