Analysis of positive cultures from endodontically treated teeth: a retrospective study.

A study of 12,150 endodontically treated teeth from 11,797 patients in a private patient setup revealed an incidence of 10.2% positive cultures obtained just before obturation of the root canal. Streptococcal predominance was reflected by a presence of nearly 60% in the pure culture and nearly 98% in the mixed cultures. No significant changes in microbial predominance or bacterial sensitivities were detected over the 7-year period of study. Ampicillin, cephalothin, erythromycin, and penicillin were the most effective antibiotics against the viridans streptococci, the most prevalent organism in the infected teeth.