title: Marginal adaptation of mineral trioxide aggregate (MTA) compared with amalgam as a root-end filling material: a low-vacuum (LV) versus high-vacuum (HV) SEM study.
abstract: OBJECTIVE
  To compare the marginal adaptation of mineral trioxide aggregate (MTA) or amalgam root-end fillings in extracted teeth under low-vacuum (LV) versus high-vacuum (HV) scanning electron microscope (SEM) viewing conditions.
  
  
  METHODS
  Root-end fillings were placed in 20 extracted single-rooted maxillary teeth. Ten root ends were filled with MTA and the other 10 root ends were filled with amalgam. Two 1 mm thick transverse sections of each root-end filling were cut 0.50 mm (top) and 1.50 mm (bottom) from the apex. Gap size was recorded at eight fixed points along the dentine-filling material interface on each section when uncoated wet (LV wet (LVW)) and dry under LV (0.3 Torr) in a JEOL JSM-5800 SEM and backscatter emission (LV dry uncoated (LVDU)). The sections were then air-dried, gold-coated and gap size was recorded once again at the fixed points under HV (10(-6) Torr; HV dry coated (HVDC)). Specimen cracking, and the size and extent of the crack were noted.
  
  
  RESULTS
  Gap sizes at fixed points were smallest under LVW and largest under HVDC SEM conditions. Gaps were smallest in MTA root-end fillings. A General Linear Models Analysis, with gap size as the dependent variable, showed significant effects for extent of crack in dentine, material and viewing condition (P = 0.0001).
  
  
  CONCLUSIONS
  This study showed that MTA produced a superior marginal adaptation to amalgam, and that LVW conditions showed the lowest gap size. Gap size was influenced by the method of SEM viewing. If only HV SEM viewing conditions are used for MTA and amalgam root-end fillings, a correction factor of 3.5 and 2.2, respectively, may be used to enable relative comparisons of gap size to LVW conditions.
authors.affiliation: Dental Research Institute of the Medical Research Council, University of the Witwatersrand, Johannesburg, South Africa. shipperg@dentistry.unc.edu
authors.forename: G
authors.initials: G
authors.lastname: Shipper
authors.forename: E S
authors.initials: ES
authors.lastname: Grossman
authors.forename: A J
authors.initials: AJ
authors.lastname: Botha
authors.forename: P E
authors.initials: PE
authors.lastname: Cleaton-Jones
mesh_terms: D017607:Aluminum Compounds; D017610:Calcium Compounds; D003723:Dental Amalgam; D018772:Dental Marginal Adaptation; D004338:Drug Combinations; D006801:Humans; D016014:Linear Models; D008855:Microscopy, Electron, Scanning / Q000379:methods; D010087:Oxides; D012184:Retrograde Obturation / Q000379:methods*; D012387:Root Canal Filling Materials; D018915:Root Canal Preparation / Q000295:instrumentation; D017640:Silicates; D014618:Vacuum
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; C086631:mineral trioxide aggregate; D003723:Dental Amalgam