title: An investigation of a potential confounder in ex vivo microbiological studies--the bulk flow of fluid through apical foramina during tooth extraction.
abstract: OBJECTIVE
  To investigate the factors affecting bulk flow of dye and bacterial suspensions into and out of apical foramina during simulated tooth extraction, using an ex vivo model.
  
  
  METHODS
  Sixty extracted, single-rooted, human teeth were accessed, root canals located and in 50 the pulps dissolved; 10 teeth with attached periapical lesions were preserved. The size of apical foramina was determined digitally. The teeth were mounted in vials with polyvinylsiloxane impression material. Part 1: different dyes were inoculated in the coronal half of root canals or cervical 'gingival' margin, respectively, in separate experiments using the same teeth. Tooth extraction movements were simulated and apical penetration of the dye solutions with and without coronal restorations were examined in each case (20 teeth re-used 4 × ). Part 2: the same procedures were repeated on 30 more teeth but using a standard inoculum of Acidovorax sp. Part 3: 10 teeth with attached periapical lesions were inoculated with Acidovorax sp. in the absence of coronal restorations. Bacterial leakage into the periapical lesions was assessed.
  
  
  RESULTS
  Coronal restorations significantly reduced the flow of dyes (P=0.002) or bacterial suspension (P=0.001) out of the canals and bacterial suspension into (P=0.02) the canals during simulated tooth extraction. The 'size of apical foramina' were positively correlated with passage of bacterial suspension out of the canal (P=0.04) and from the gingival trough into the canal (P=0.008), in the presence of a coronal restoration.
  
  
  CONCLUSIONS
  The presence of coronal restorations, the size of apical foramina and presence of native canal contents with attached periapical lesions, all influenced fluid flow into and out of canals during simulated tooth extraction movements.
authors.affiliation: Department of Restorative Dentistry, UCL Eastman Dental Institute, University College London, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Kapalas
authors.forename: D A
authors.initials: DA
authors.lastname: Spratt
authors.forename: Y-L
authors.initials: YL
authors.lastname: Ng
authors.forename: K
authors.initials: K
authors.lastname: Gulabivala
mesh_terms: D003763:Dental Leakage; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000382:microbiology*; D006801:Humans; D057446:Hydrodynamics; D010486:Periapical Tissue / Q000382:microbiology*; D012212:Rheology; D019227:Tooth Apex / Q000382:microbiology*; D014081:Tooth Extraction