26 Jan The dark side of Rubber Dam. Part III.
We have analyzed, in the former article, the geometrical incompatibility among the rubber dam hole and the cervical contour of the tooth. The resulting open spaces have two effects:
- allow fluids passages under the pressure of muscles (tongue, cheek, lips) and under the gravity force
- can promote fluids passage by means of capillarity
The capillarity action is the ability of a liquid to rise up in narrow space without the assistance of an external force.
In the example below, you can see that the liquid climb up higher in narrower tubes without the assistance of any external forces and against the gravity force.
The geometrical incompatibility among rubber dam and tooth contour promotes the rising up of fluids because creates narrow spaces.
In the image below – shot under the microscope – you can see that the “fractal” geometry of the cervical contour of the tooth is promoting the rising of fluids. And that can be better appreciated on a high scale of magnification.
Lower incisors are a typical example of these issues… Owing to the complex interdental geometry of these teeth – full of concavities – and the resulting incompatibility among the rubber dam and the tooth contour we can assist during the restorative procedures under rubber dam to
- fluids coming through these geometrical incongruences under the pressure of the tongue
- fluids rising up thanks to these geometrical incongruences under capillarity action
The same happens where the prongs of the clamp contact the tooth structure. Wider is the prongs (as it happens with some clamps), higher will the capillarity: as it happens in class V for example.
Paradoxically, the use of rubber dam might increase the movements of fluids respect of not using a rubber dam.