Studies of dental root surface caries. 1: Comparison of natural and artificial root caries lesions

Qualitative polarized light microscopy and cross-sectional microhardness te sting profiles were used to compare artificial root caries lesions with tho se naturally present in extracted human teeth. The artificial lesions were produced by immersion of roots with exposed windows in chemical buffers of acetate and lactate with no added enzymes or bacteria. The three buffer sys tems used produced lesions with the range of histological characteristics o f natural lesions. These included a 'body' or 'surface' zone of the lesion when viewed in water, and a 'frontal' zone of reverse birefringence when vi ewed in quinoline. The 'frontal' zone was noted to first develop after thre e days of immersion in acetate buffer. Advanced natural lesions exhibited a wide, diffuse, advancing front, which was similar to that produced by 28-6 0 day lesions in acetate. Microhardness profiles of natural lesions could a ll be matched by one or more of the artificial lesions. The demineralizing process was seen to reduce mineral content across the lesion from 45 per ce nt in normal dentine to between 15 and 25 per cent.