Modeling colorant leakage techniques: application to endodontics.
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.
Romieu
Olivier J
OJ
Laboratory Bionano, Université Montpellier Sud de France, Montpellier, France. olivier@romieu.info
Zimányi
László
L
Warszyński
Piotr
P
Levallois
Bernard
B
Cuisinier
Frédéric J
FJ
de Périère
Dominique Deville
DD
Jacquot
Bruno
B
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
D004396:Coloring Agents; D012387:Root Canal Filling Materials; C028433:chinese ink; D002244:Carbon; D006171:Gutta-Percha; D008751:Methylene Blue