A CLINICAL AND MICROBIOLOGICAL STUDY OF DEEP CARIOUS LESIONS DURING STEPWISE EXCAVATION USING LONG TREATMENT INTERVALS

Concern about the survival of microorganisms in deep carious lesions m ay often lead to unnecessary exposure of the pulp during final excavat ion. There are reasons, therefore, to initiate systematic studies on t he alternative procedure known as stepwise excavation. Clinical evalua tion of stepwise excavation was performed on 31 deep carious lesions c onsidered to result in pulp perforation by traditional excavation. Thi s study examines the clinical and microbiological alterations during t he final excavation performed during long intervals (6-12 months) afte r the initial treatment that included peripheral dentine excavation an d removal of the central cariogenic biomass and the superficial necrot ic 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 befo re and after final excavation, Microbiological dentine samples were ob tained in 19 randomly selected lesions by a sterile bur, transferred t o and diluted in reduced transport fluid, and plated on tryptic soy ag ar. After anaerobic incubation at 37 degrees C for 7 days, total colon y-forming units per millilitre were counted from (1) peripheral excava ted and hard dentine (control), (2) central demineralized dentine befo re the final excavation, and (3) central dentine after the final excav ation. Six samples of central demineralized dentine were without any c ultivable flora increasing to 9 samples after the final excavation, Th e clinical dentine changes occurring during stepwise excavation were c haracterized 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 th e carious lesions resulted in pulp perforation, suggesting that the in itial removal of the cariogenic biomass appears to be essential for co ntrol of caries progression. Stepwise excavation is not only an approp riate treatment of deep carious lesions but is also considered a suita ble model for microbiological studies to determine the bacteria persis ting in clinically excavated lesions.