Purpose: to analyze the in vivo microbial status of the middle and apical segments of the root canal system of mesial roots of human mandibular molars with primary apical periodontitis after 1- or 2-visit endodontic treatment.
n: 13 teeth (cases). Inclusion: mesial canals of mandibular molars with necrotic pulps and radiographic evidence of apical periodontitis that were extracted for reasons not related to this study.
•The teeth were assigned randomly into 2 groups: one visit and 2 visits groups
•Two visits group (7 molars): the MB canals were instrumented up to K3 #40,06 and then #up to #60 lightspeed, the ML canals were instrumented with Protaper up to F2. irrigation done with 5% NaOCl, 17% EDTA and 2% CHX. CaOH placed for one week, obturation with continuous wave of compaction tech.
•One visit group (6 molars): the same procedure as in the 2 visits group done except that teeth were obturated in the same appointment with no CaOH medicament.
•the teeth were extracted carefully 1 week after 1st visit, sectioned and examined histologically.
Most highlighted Results:
•In the 1-visit group, no case was completely free of bacteria; residual bacteria occurred in the main root canal (5 of 6 cases), isthmus (5 of 6), apical ramifications (4 of 6), and dentinal tubules (5 of 6).
•In the 2-visit group, 2 cases were rendered bacteria-free; residual bacteria were found in the main canal only in 2 cases (none of them with persistent dentinal tubule infection), in the isthmus (4 of 7 cases), and in ramifications (2 of 7).
•When filling material was observed in ramifications, it was usually intermixed with necrotic tissue, debris, and bacteria.
The 2-visit protocol by using an interappointment medication with calcium hydroxide resulted in improved microbiological status of the root canal system when compared with the 1- visit protocol.
One-visit group. (A) Severely broken-down mandibular right first molar in 30-year-old woman. Caries has involved the furcation, and apical periodontitis lesions are present on both roots. (B) Postobturation RG. (C) RG of mesial root after extraction. (D) Specimen immersed in clearing agent before embedding in paraffin. (E) Cross-cut section taken from the middle third at the level of line 1 in(D). Both canals appear well-prepared, with dentin removed circumferentially and a round shape of similar diameter at this level. Note the wide isthmus harboring obturation material connecting the 2 canals and the lingual extension of the lingual canal (arrow) (Taylor modified Brown & Brenn stain) (F) Detail of lingual canal. A large mass of necrotic debris colonized by bacteria occupies the central part of the canal lumen, embedded in the obturation material. High-power view from center of this mass shows amorphous material (likely food remnants) surrounded by heavy concentration of bacterial profiles. (G) Detail of isthmus in (E). (H) Magnification of area indicated by upper arrow in (G). Bacterial biofilm covers the irregularity in dentin wall of the isthmus. (I) Magnification of area on opposite isthmus wall indicated by lower arrow in (G). In addition to biofilm present on dentin wall, bacteria are also colonizing dentinal tubules.