Novel ex vivo biofilm model : a comparative study of root canal disinfection

• Main Author: Lin, Jimmy Su-Yee
• Language: English
• Published: University of British Columbia 2012
• Online Access: http://hdl.handle.net/2429/42846

Bacteria, organized as biofilms within the root canal, can cause apical periodontitis (AP). It has been shown that microorganisms harbouring in the anatomical irregularities of the root canal system such as fins, grooves, or isthmuses after treatment, decrease the outcome prognosis of endodontic therapy. Therefore, adequate removal of these microorganisms is essential for the prevention and treatment of AP. While difficulties in disinfection have been recognized, limited data are available to directly assess the effectiveness of bacteria removal by treatment. Thus, the aim of this study is to develop a standardized ex vivo biofilm model, closely resembling the in vivo clinical situation, to quantify and compare the efficacy of hand, rotary nickel-titanium (NiTi) and self-adjusting file (SAF) instrumentation in the removal of biofilm bacteria. Thirty-six extracted single-rooted human teeth with an ovoid cross-section canal were selected. Each tooth was split longitudinally and a 0.2 mm wide by 0.3 mm deep groove was placed in the apical 2 to 5 mm of the canal. After growing mixed bacteria biofilm inside the canal under anaerobic condition, the split halves were reassembled in a custom block, creating apical vapour lock. Teeth were randomly divided into 3 treatment groups (n = 10 per group) using: (1) hand stainless steel (SS) K-file; (2) ProFile NiTi rotary instrumentation; and (3) SAF. Irrigation consisted of 10 ml 3% sodium hypochlorite and 4 ml 17% ethylenediaminetetraacetic acid. Six teeth received no treatment. Areas of the canal inside and outside the groove were examined using a scanning electron microscope. Within the groove, a smaller area remained occupied by bacteria after the use of SAF than ProFile and SS K-file (3.25%; 19.25%; 26.98%) (P < .05). For all groups, significantly more bacteria were removed outside the groove than inside (P < .05). No statistical differences were found outside the groove (P > .05). Although all techniques equally removed bacteria outside the groove, SAF significantly reduced more bacteria from within the apical groove. No technique was able to completely remove the bacteria. The biofilm model represents a potentially useful tool for future study of root canal disinfection. === Dentistry, Faculty of === Graduate