Effects of instrumentation, irrigation and dressing with calcium hydroxide on infection in pulpless teeth with periapical bone lesions

Aim The aim of this study was to evaluate the fate of microorganisms in root canals of teeth with infected pulps and periapical bone lesions with and without the use of calcium hydroxide medication. Methodology Endodontic samples were cultured and microorganisms were counted and identified in 4 3 teeth before (sample 1) and after (sample 2) treatment during the first visit and before (sample 3) and after (sample 4) treatment during the second visit. In the first visit teeth were instrumented and half of the teeth were filled with a thick slurry of calcium hydroxide in sterile saline, The other teeth were obturated with gutta-percha and AH-26 seater. After 4 weeks the teeth with calcium-hydroxide were accessed again and after microbiological sampling they were obturated with gutta-percha and AH-26 sealer. Results The mean total colony forming unit (CFU) counts of positive samples dropped significantly as a result or canal preparation during the first visit from 1.0 X 10(6) to 1.8 x 10(3) (between samples 1 and 2) but increased to 9.3 x 10(3) in the period between the two visits (sample 2 and 3). There was no difference in mean total CFU counts of positive samples between the end of the first (sample 21) and the end of the second visit (sample 4). The most frequently isolated species were Prevotella intermedia, Capnocytophaga spp.. Actinomyces odontolyticus, Propionibacterium acnes and Peptostreptococcus micros. Conclusions Although a calcium hydroxide paste was placed in the prepared canals. the number of positive canals had increased in the period between visits. However, the number of microorganisms had only increased to 0.93% of the original number of CFU (sample 1). It is concluded that a calcium hydroxide and sterile saline slurry limits but does not totally prevent regrowth of endodontic bacteria.