On testing microbial presence in the root canal

Abstract

Microbiologic root canal sampling (MRS) has been available to the practising dentist for a full century. During this time its potential benefits and clinical use have almost constantly been argued and disputed. The controversies have not been settled. The overall aim of the present thesis was, therefore, to renew the discussion and to shed new light on the potential, shortcomings and future role of MRS. In the first part, the degree to which MRS was adopted by general practitioners and the reasons for their acceptance or rejection of the methodology were studied. From laboratory records obtained over a period of 25 years, it was calculated that the adoption level among dentists in the Gothenburg region was 3 to 5 percent. Even among adopters MRS was rarely used on a routine basis but in selected cases. Data from a questionnaire survey among the practitioners in that region confirmed these findings. The main reasons for non-adoption seemed to be a perceived low cost benefit ratio and lack of advantage relative to a more standardised treatment strategy. The potential role of MRS in retreatment cases was addressed in the second part of the thesis by studying (i) retrospectively and (ii) prospectively the composition of the microflora that resists treatment. (i) The microbiological status of 100 root-filled teeth with persistent periapical lesions was examined prior to retreatment. Microorganisms were recovered in 68 of these teeth. Facultative anaerobes predominated the isolates. E. faecalis was the most frequently isolated species, showing "heavy" or "very heavy" growth in 25 of 32 positive samples. The sampling of 20 teeth without lesions also showed a high frequency of microbial growth (50%) but the number of cultivable organisms was less. (ii) The potential of intracanal microorganisms to resist maximised intracanal medication was investigated on 50 non-treated teeth, with necrotic and infected pulps. The findings gave no support for an increased overall antimicrobial effect of this combination in comparison with CH alone. These studies have shown that if microorganisms do persist in teeth exposed to treatment in general practice, retreatment cases and teeth receiving intensive antimicrobial treatment they are of similar kinds. Frequent isolates are facultative streptococci, enterococci and lactobacilli. Based on the treatment of 50 infected teeth the diagnostic accuracy of MRS was assessed. Sensitivity and specificity of the test were found to reach 68% and 75%, respectively, when 5% iodine-potassium-iodide was used as a dressing. The data supported the hypotheses that intracanal chemical substances substantially influence test results, and that dressings vary in their potential to induce bias. In a search for alternative methodologies the potential of polymerase chain reaction technology (PCR) was investigated. PCR showed high specificity, and low detection levels (10 cells) for E. faecalis and E. faecium.