Microflora of Root Filled Teeth with Apical Periodontitis and Its Sensitivity to Antibacterial Substances. Summary of the Doctoral Thesis

Abstract

This doctoral thesis “Microflora of root filled teeth with apical periodontitis and its sensitivity to antibacterial substances” focuses on a study of root canal infection which is a primary aetiological factor of apical periodontitis. Apical periodontitis (AP) is a periodontal inflammation caused by infection in the root canal system and may pass as a chronic asymptomatic process that can be detected during dental radiographic investigation. Epidemiological studies reveal relationship between endodontically treated teeth and chronic AP in 25-40 % cases, thus indicating a potentially high need for endodontic retreatment in different populations. In a study carried out in Latvia, it was discovered that chronic AP is present in more than 30% of teeth which have undergone root canal treatment. Microbial flora of filled root canals is different from infection of primary root canal and is more resistant to antibacterial agents. The microbial flora of endodontically treated root canals has not been studied in Latvia. The aim of the study was to investigate the microbial flora of endodontically retreated root canals with chronic apical periodontitis and to determine the sensitivity to antibacterial substances used in root canals, as well as to determine the prevalence of β-lactamase producing bacterial strains in Latvian patients. 35 patients were involved in the study who received root canal retreatment Endodontic Department at the Institute of Stomatology of Riga Stradins University or an extensive private dental clinic in Riga, Latvia. During the retreatment, microbiological samples were taken and transported to the laboratory of Microbial Strain Collection of Latvia. Identification of isolated bacterial strains, determination of β-lactamase producing strains and evaluation of sensitivity of bacterial strains to 2.0% sodium hypochlorite solution, 0.2 % chlorhexidine digluconate solution and calcium hydroxide paste using the agar diffusion test were carried out. The obtained data was entered in the Microsoft Office Excel database. Statistical analysis of the data was performed by SPSS Statistics 17.0 and Microsoft Office Excel softwares. Standard descriptive statistical methods and Chi square statistical test were used to characterize microflora isolated from endodontically treated root canals. Sensitivity of strains of the isolated microorganisms to antibacterial substances used in root canals was evaluated using analysis of dispersion (ANOVA). The analysis of research findings showed that: Gram-positive microorganisms prevail in the microbial flora of endodontically treated root canals with chronic apical periodontitis in Latvian patients; 1 to 6 species of microorganisms can be isolated and identified with a method of cultivation from endodontically treated root canal with chronic apical periodontitis; Bacterial species more frequently isolated from endodontically treated teeth with chronic apical periodontitis belong to the genera of Actinomyces, Streptococcus, Staphylococcus, Lactobacillus and Entero-coccus; β-lactamase producing microorganisms add up to almost one-fifth of bacterial strains isolated from retreated root canals; The most frequently found β-lactamase producing bacterial species belong to the genera of Actinomyces and Staphylococcus; β-lactamase producing bacterial strains are found in about one-third of patients involved in the study; Bacterial strains isolated from the retreated root canals are sensitive to sodium hypochlorite and chlorhexidine gluconate solutions and are weakly sensitive to calcium hydroxide paste when tested in vitro; Different strains of the same microbial species may have different sensitivity to antibacterial substances used in root canals. Based on the research results and scientific literature, practical recommendations are elaborated for irrigation and temporary dressing of retreated root canals with chronic apical periodontitis.