[Confocal laser scanning microscopy (CLSM): histotomography of altered dental hard tissue in pathological mouth cavity ecology].

There is no consensus regarding the aetiology of radiation-induced caries. Lesion formation is assumed to originate either from direct radiogenic damage of the hard tissue or from the indirect effects correlated with radioxerostomia. A comparative study is presented of sound teeth (group 1), teeth with documented radiation caries (group 2), teeth after in situ radiation (group 3): 60 Gy, fractionated) and teeth after in vitro radiation (group 4: 500-2500 Gy). Radiations were carried out with a 60Co source. The dentoenamel junction was studied with confocal laser scanning microscopy (CLSM). Axial sections of the teeth were used either fresh or embedded in Technovit (sawing-grinding technique). Under these conditions subsurface areas of the sections can be visualized non-destructively. Characteristic modifications could be observed only after in vivo radiotherapy (group 2): (1) the ramifications near the junction are rare, (2) the dentine tubuli end before the limits of the hard tissue and (3) the remittance of light in reduced in a 10-microns-wide zone along the dentoenamel junction. The obliteration of the dentine tubuli following degeneration of the odontoblast processes obviously is the result of the direct radiogenic cell damage, with reduced metabolism particularly in the area of the ends of the odontoblasts. The metabolism deficit mediates parenchymal damage (zone of reduced light remittance), explaining the functional symptom of undermining caries. The micromorphological manifestation of this direct radiation damage obviously requires the vital tooth and therefore cannot be observed after in vitro and in situ irradiation.