title: Modeling colorant leakage techniques: application to endodontics.
abstract: OBJECTIVE
  Our aim was to improve the comprehension of in vitro tracer leakage studies and to determine in which conditions such studies can be reliable. We aimed to develop different theoretical models to describe either an initially dry or a wet interface (slit) between sealer and dentin.
  
  
  METHODS
  Equations based on physical laws were derived to model theoretically in vitro tracer penetration. For the dry interfaces, atmospheric, hydrostatic, tracer gravimetric, capillary and internal air pressures were considered as the underlying forces that control tracer penetration. For wet interfaces, the laws of diffusion were used to model colorant penetration.
  
  
  RESULTS
  In both cases penetration is influenced by the width of the interface and by the size of the colorant. Calculations for dry conditions have shown that penetration is quick, mainly driven by the capillary pressure, and the penetration increases as the width of the interface diminishes. Dentinal tubules and the extent of their interconnection modify the penetration depth. For wet conditions, tracer size is the main factor controlling the penetration length and speed (the bigger the tracer, the slower the penetration).
  
  
  CONCLUSIONS
  Our model calculations demonstrate that tracer penetration studies have to be performed under strict experimental conditions. Dry and wet interfaces are two extreme cases with very different tracer penetration modes. In vitro colorant penetration tests should be performed in both of these conditions avoiding cases where the slit contains both air and water. Theses models can be adapted to other dental situations as well.
authors.affiliation: Laboratory Bionano, Université Montpellier Sud de France, Montpellier, France. olivier@romieu.info
authors.forename: Olivier J
authors.initials: OJ
authors.lastname: Romieu
authors.forename: László
authors.initials: L
authors.lastname: Zimányi
authors.forename: Piotr
authors.initials: P
authors.lastname: Warszyński
authors.forename: Bernard
authors.initials: B
authors.lastname: Levallois
authors.forename: Frédéric J
authors.initials: FJ
authors.lastname: Cuisinier
authors.forename: Dominique Deville
authors.initials: DD
authors.lastname: de Périère
authors.forename: Bruno
authors.initials: B
authors.lastname: Jacquot
mesh_terms: D000399:Air Pressure; D002244:Carbon; D004396:Coloring Agents; D003763:Dental Leakage / Q000175:diagnosis*; D003786:Dental Pulp Cavity; D003804:Dentin / Q000648:ultrastructure; D003806:Dentin Permeability; D004058:Diffusion; D006112:Gravitation; D006171:Gutta-Percha; D006874:Hydrostatic Pressure; D008751:Methylene Blue; D008954:Models, Biological; D012387:Root Canal Filling Materials
chemical_list: D004396:Coloring Agents; D012387:Root Canal Filling Materials; C028433:chinese ink; D002244:Carbon; D006171:Gutta-Percha; D008751:Methylene Blue