Bacterial Flora and Extraradicular Biofilm Associated with the Apical Segment of Teeth with Post-Treatment Apical Periodontitis

Many investigators (Nair, Sequeira) have demonstrated that most root canal failures are caused by viable bacteria and their by-products, which survive following endodontic treatment. Recent studies (Yang, Yu) have indicated that bacteria can migrate from an infected canal and colonize micro-resorptive areas in the external aspect of the root in proximity to the apical foramina. These bacteria form complex, multi-bacterial aggregations called biofilms. Micro-organisms in these biofilms possess pathogenic characteris- tics that differ from their planktonic or monoculture forms. Biofilms are synergistic complexes which cloak themselves in an extracellular material which fools the host immune response and prevents phagocytic cells from removing the invaders. Further, the avascular nature of the lesion of endodontic origin prevents systemic antibiotic treatment from effectively contacting and eradicating the bacteria. Consequently, extraradicular biofilms may remain undis- turbed and functional even when the internal root canal system has been meticulously cleansed and hermetically sealed from crown to root apex resulting in failure of lesions to heal.

Wang et al, JOE 38:7 pp 954-959, undertook a study to characterize the location, construction, and primary bacterial flora of extraradicularbiofilms. 23 teeth with lesions of endodontic origin >1 cm which persisted, unchanged, for one year following conven- tional root canal therapy were chosen for this study. The teeth were surgerized in an aseptic manner and the apical 3 mm of the root resected and removed for evaluation with scanning electron micros- copy (SEM), Brown and Brenn staining for the presence of bacterial colonies, and DNA evaluation to characterize the bacteria. A group of 10 teeth with normal, vital pulps, extracted for orthodontic reasons were used as controls for comparison. As expected, no bacteria or biofilms on the apical root surface were observed in the controls.

The authors found all 23 teeth with persistent lesions had complex biofilms with extensive extracellular masks extending along the root surface as much as 3 mm from the apical foramina. The biofilms were made up of cocci, bacilli, and filamentous bacteria by shape, much of which was hidden by the extracellular material. The DNA characterization showed 26 species of bacteria predominated by Actinomyces, Propionibacterium, Prevotella, Streptococcus, and Porphomonas endodontalis. These bacteria fall into the categories of obligate and facultative anaerobes.

biofilm-x5000

Biofilm x5000

SEM-Apical-Foramen-x300

SEM Apical Foramen x300

Biofilm-X100

Biofilm X100

The traditional view of lesions of endodo

ntic origin has been that the bacterial source has been within the confines of the root canal system and that the lesions were sterile due to host immune system removing all the extraradicular bacteria. The old paradigm has died with these recent findings. If the root canal system has been adequately cleaned, shaped, disinfected and sealed from apex to coronal orifice then we can expect a good rate of healing. The Toronto endodontic healing studies of Friedman et al put that at about 85%. The question is always has the tooth been adequately cleaned and sealed. Cone Beam CT and microscope enhanced vision has given us an improved perspective by allowing us to visualise the complex anatomy present. But we also have to address the fact that in the presence of persistent infection, surgery to remove the apical 3 mm of the root surface may be necessary and is indeed the most appropriate treatment to facilitate healing. The Toronto study shows in surgical cases following closely on recent retreatment, that overall successful healing can be expected in the 98% range.

As our understanding of the pathogenic vectors deepens and our ability to master the complex root canal system with micro- scope and CBCT increases we can, with confidence, predict a high survival rate for the vast majority of our patients with persistent apical pathology.

 

ABOUT DR. HOWARD BITTNER

Dr. Bittner was born and raised in the Surrey/Langley area. Following his pre-dental training at Simon Fraser University, he received his Doctor of Dental Medicine from the University of British Columbia in 1982 and his Certificate in Advanced Graduate Studies in Endodontics from Boston University’s Goldman School of Dental Medicine in 1995.

Dr. Bittner was in private practice in general dentistry for 11 years in Langley prior to his endodontic specialty training. He has a wide background in all facets of general dentistry, with advanced dental training in prosthetic dentistry from respected educational facilities such as Creating Restorative Excellence in Tacoma, Washington, and The Pankey Institute in Miami, Florida. He has been practicing the dental specialty of Endodontics since 1995.

He is a past president of the British Columbia Society of Endodontists, the Dental Specialists Society of British Columbia, and the Concentric Endodontic Study Club. Dr. Bittner is also a guest lecturer in the Faculty of Dentistry at the University of British Columbia.

On October 30, 2012, posted in: News for Doctors by