Lipidhistochemical and microradiographic study of distribution of lipids in relation to mineral content in dentin...

Fifteen human molars were investigated using lipidhistochemical and microradiographic methods. A peripheral necrotic and totally decalcified part of the carious lesion revealed a markedly positive staining reaction for sphingomyelin, sulfatides, cholesterol- and/or triglyceride-esters. The reaction was probably conditioned by the presence of debris and plaque within this area. Pulpally and immediately below the necrotic zone, an area of demineralization was found which on the microradiographs appeared as a radiolucent zone. The zone showed a mineral gradient with an increasing mineral content towards the pulp. In the zone of demineralization a positive reaction occurred for sphingomyelin decreasing in a pulpal direction with increasing mineral content. A weakly positive reaction for cholesterol- and/or triglyceride-esters was also detected but only in the most pulpal part of the zone of demineralization; the intensity of the staining reaction was comparable to that found in normal dentin. In those areas which were represented by a sclerotized, radiopaque zone, only a very weak reaction for sphingomyelin, cholesterol-and/or triglyceride-esters could be observed of the same staining intensity as in normal dentin. The region between the lesion and the pulp showed the same staining intensity as normal dentin.