Caries excavation should happen like this: As much as necessary, as little as possible. In this first part of his lecture Prof. Dr. Wolfgang Buchalla, University of Regensburg/Germany, outlines why it is so difficult to identify the excavation edge and how to approach this issue. Caries originates from the destruction of low-molecular carbohydrates by bacteria like lactobacilli and actinomycetes. The organic acids set free that way are neutralized by the tooth substance and lead to their demineralisation - a carious lesion.
It is moist because of saliva inclusions, usually discoloured, colonized by microorganisms and therefore containing bacterial endotoxins. In their daily routine dentist create an access cavity using diamonds to reach this lesions. An undermining excavation of the soft dentin follows using a carbide rose-head bur. Whether the remaining tooth substance is free of infection or not the dentist decides visual-tactually. He examines the colour of the dentin area near the pulp and the clank of the probe to determine whether the excavation has been sufficient already.
During the last two decades means have been developed like the caries detector, the Carisolv-system and the polymer rose-head bur, which are to enable a sufficient excavation while inhibiting an over-excavation. None of those has established completely in daily practice. FACE is based on the identification of bacterially infected areas of the tooth substance. Carious dentin presents a red fluorenscence when exposed to purple light of the wavelength of 405 nm. This is caused by the presence of fluorescent porphyrins. Non-carious areas show a green fluorescence.
Ideally the light source is integrated in the contra-angle handpiece, to combine diagnostic detection and therapy. Up to now only tools are on the market wich can be used preoperatively as diagnostic means to enable a sufficient and coincidently sparing excavation.