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This study describes cellular and microradiographic findings in thin undemineralized enamel-dentine sections from 36 enamel caries lesions from freshly extracted third molars. Lesions activity was determined by clinical examination and the estimated age of the lesion at extraction time. The cellular reactions to the enamel/dentine lesion complex were measured using computerized histomorphometry under the following conditions: (a) the cytoplasm:nucleus ratio of the odontoblast cell; (b) the odontoblast cell:dentinal tubule ratio, and (c) the adjacent predentine area (microm2). The first cellular reactions were observed beneath superficial enamel lesions before visible alterations in dentine mineralization. The cytoplasm:nucleus ratio of the odontoblast cells was markedly reduced, and only active lesions showed evidence of cellular proliferation into the cell-free zone. In more advanced active lesions the affected odontoblast cells had a significantly lower cytoplasm:nucleus ratio compared with the controls. Similar changes were not seen in arrested or slow-progressing lesions. Before onset of tertiary dentine formation there was a positive correlation between odontoblast cell size and predentine formation. Primary odontoblast cells were involved in early tertiary or reactionary dentine formation without odontoblast cell replacement. Reactionary dentine was only seen in active lesions, suggesting that reactions in the dentine/pulp complex are closely associated with the external environment.

Concern about the survival of microorganisms in deep carious lesions may often lead to unnecessary exposure of the pulp during final excavation. There are reasons, therefore, to initiate systematic studies on the alternative procedure known as stepwise excavation. Clinical evaluation of stepwise excavation was performed on 31 deep carious lesions considered to result in pulp perforation by traditional excavation. This study examines the clinical and microbiological alterations during the final excavation performed during long intervals (6-12 months) after the initial treatment that included peripheral dentine excavation and removal of the central cariogenic biomass and the superficial necrotic dentine. The dentine colour and consistency were assessed by means of standardized scales before application of a Ca(OH)2 compound and a temporary sealing for 6-12 months. Reassessments were performed before the after final excavation. Microbiological dentine samples were obtained in 19 randomly selected lesions by a sterile bur, transferred to and diluted in reduced transport fluid, and plated on tryptic soy agar. After anaerobic incubation at 37 degrees C for 7 days, total colony-forming units per millilitre were counted from (1) peripheral excavated and hard dentine (control), (2) central demineralized dentine before and final excavation, and (3) central dentine after the final excavation. Six samples of central demineralized dentine were without any cultivable flora increasing to 9 samples after the final excavation. The clinical dentine changes occurring during stepwise excavation were characterized by enhanced hardness of the dentine which was associated with a marked reduction in bacterial growth after the final excavation. Despite the presence of bacteria in the excavated dentine none of the carious lesions resulted in pulp perforation, suggesting that the initial removal of the cariogenic biomass appears to be essential for control of caries progression. Stepwise excavation is not only an appropriate treatment of deep carious lesions but is also considered a suitable model for microbiological studies to determine the bacteria persisting in clinically excavated lesions.

The material comprised 140 extracted maxillary third molars. The central fossa area was examined with a stereomicroscope (SM) (x16) and macroscopically (M) under standardized conditions after cleaning and air-drying. Signs of caries were classified using a detailed scoring system involving 12 (SM) and 8 (M) classification criteria, ranging from 'sound' to 'cavitation with dentine involvement'. Six radiographic scores were used in the classification. Sections 250 microns in thickness were cut in buccolingual direction through the central fossa, and the fossa section with the most extensive stereomicroscopic changes was selected for histologic examination (x16). The histologic enamel and dentine changes were classified independently using 9 and 7 scores, respectively. The correlation between SM and the histologic enamel changes (HE scores) in terms of progressive demineralization and destruction were highly correlated (rs = 0.90). Dentinal changes were also highly correlated with enamel changes (rs = 0.85). The histologic classifications in conjunction with the macroscopical observations made it possible to demonstrate a clear relationship between the external degree of caries progression and the internal enamel and dentine reactions. The data did not support routine usage of radiographic examination for occlusal caries diagnosis.

This study aims to describe the histological and ultrastructural enamel reactions to regular disturbance/removal of dental plaque, using an in vivo caries model. Fourteen young volunteers undergoing orthodontic treatment participated in the study. To create local protected areas, orthodontic bands with a buccal space were placed in homologous pairs of premolars. One tooth in each pair served as control and had the band cemented for the entire test period of 5 weeks. The other band was removed weekly and the buccal surface cleaned, either by careful pumicing with a nonfluoride toothpaste, or by simple cleaning with a cotton pellet. Results indicated that 5 weeks with completely undisturbed plaque accumulation resulted in visible enamel demineralization in all 14 individuals, whilst a weekly performed professional plaque removal was able to prevent lesion progress independent of the cleaning procedure. It is therefore concluded that regular mechanical disturbance of dental plaque is able to suppress bacterial activity and hence caries development.