Single sitting root canal treatment involves complete canal system preparation, irrigation, and obturation in one treatment session. It also involves removal of existing previous root filling material at the same sitting if carrying out a nonsurgical retreatment procedure. It is generally accepted that in teeth with a vital pulp, in which there is only superficial infection of the coronal pulp, immediate obturation following pulpectomy and canal instrumentation is the most appropriate treatment.
The long-running debate over whether to treat the tooth in one or more sittings involves cases in which there is a necrotic pulp and evidence of apical periodontitis, indicated by an area of radiolucency on a periapical radiograph. There are two schools of thought:
• The first assumes that all microbes and their byproducts are eliminated during the shaping and cleansing procedures, or that residual bacteria are entombed within the canal by a well-fitting root filling placed at the same sitting.
• The alternative view is that some bacteria almost always remain after instrumentation, and therefore an intracanal medicament should be placed between sittings to eliminate any residual flora. The canal system is reirrigated and then filled at the second sitting.
The principle for the latter approach is based on a study by Sjögren et al. (1991), wherein bacterial sampling and culturing were carried out following complete preparation of single-rooted teeth. Reduced numbers of bacteria were identified in more than half the samples – a finding that has been confirmed in numerous subsequent studies. Following placement of a calcium hydroxide dressing in the canal systems for 7 days, an additional bacterial assay was done, and no persisting viable bacteria could be detected. The authors concluded that a calcium hydroxide dressing for at least 7 days was necessary to eliminate all viable bacteria from the root canal.
The two criteria studied following both single and multiple sitting approaches have been the incidence and severity of postoperative pain and the longer-term outcome of the procedure.
There appears to be no significant difference in the amount of posttreatment pain, according to the many publications on the subject (Fox et al., 1970; Mulhearn, 1982; Roane et al., 1983; Oliet, 1983; Genet et al., 1986; Fava, 1989; Trope, 1991; DiRenzo et al., 2002; Yoldas et al., 2004). Similarly, no significant differences in healing rates were reported in a number of admittedly limited and relatively short-term studies until a landmark publication by Sjögren et al. (1997). Fifty-five single-rooted teeth with evidence of apical periodontitis were thoroughly cleansed and shaped before bacterial sampling, and bacteria were still detected in 22 cases. All teeth were nevertheless obturated and then reviewed 5 years later. Complete healing had occurred in 94% of cases that had yielded an initial negative culture, but in just 68% in which samples were positive before root filling. The difference was statistically significant. The authors’ conclusions emphasized the importance of eliminating bac/>