RESUMO
OBJECTIVE: The present study investigated the histobacteriological condition of human carious dentine, and the histological response of dental pulps after selective caries excavation to firm dentine and cavity restoration with adhesive procedures. METHODS: Twelve vital teeth with medium/deep occlusal caries from 12 patients were scheduled for extraction. The patients gave consent to have caries removed selectively and the cavity restored with adhesive procedures prior to extraction. Caries excavation was achieved using burs and sharp hand excavators until "leathery" or "firm" dentine was encountered. After extraction, the teeth were completely-demineralised, processed for light microscopy, serial-sectioned and stained with haematoxylin and eosin staining for histological examination of dentine characteristics and pulpal responses. Additional sections were stained with Taylor-modified Brown and Brenn technique for histobacteriological examination of bacteria infiltration of the dentinal tubules and dental pulp. RESULTS: The 12 teeth showed varying degrees of tertiary dentine formation. Chronic inflammatory cell infiltrates were identified in the pulp of all specimens and appeared as scattered inflammatory cells or exiguous localised accumulations. Capillaries were heavily congested with erythrocytes and polymorphonuclear leukocytes. A large amount of stainable bacteria was observed in the dentine subjacent to the cavity floor in all specimens. CONCLUSIONS: The present study demonstrated that "leathery" or "firm" carious dentine is infected. The remnant bacteria in the dentine provoked subclinical pulpal inflammation over the entire evaluation period. The presence of potentially-arrested caries does not necessarily mean that bacterial infection is absent or under control. CLINICAL SIGNIFICANCE: Knowledge on the pulpal response to active caries and the inflammatory responses associated with bacteria ingress into dentine is paramount in helping clinicians make an informed, rational choice based on biologically-robust principles.
