## 3 Results  
Study characteristics: The preliminary search yielded 772 articles. Screening based on title and abstracts led to the exclusion of 698 articles that were either duplicates or irrelevant. Full texts of the remaining papers (n = 74) were retrieved. After applying the inclusion  
Figure 1: PRISMA flowchart summarizing the selection process employed in the review. criteria, 21 articles were included. Table 1 summarizes the data retrieved from the included studies. The sample size ranged from 32 to 538 (patients/teeth) in the included studies. Five studies justified the sample size used [18; 19; 20; 21; 22]. The studies showed variation in the RCT procedure: some used hand-driven files [23; 24; 25; 26; 27; 28; 29] while others used a combination of hand-driven and rotary instruments [7; 8; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34]. One study used normal saline [23] as an intracanal irrigation, whereas 17 used sodium hypochlorite [18; 19; 20; 21; 22; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34] and the rest did not specify. Twelve studies employed calcium hydroxide [8; 18; 19; 20; 22; 23; 24; 25; 27; 30; 33; 34] as an intracanal medicament, and the rest kept the cavity sterile (without intracanal medication) [7; 21; 26; 28; 29; 31; 35] until the obturation. Twelve trials included both vital and nonvital teeth [8; 19; 20; 22; 26; 28; 31; 32; 33; 35; 36] seven had nonvital teeth only [7; 23; 24; 25; 27; 30; 34] and two included vital teeth only [18; 29]. Outcome measures: Postoperative pain and/or flareup was the major outcome assessed in the present review. Pain was assessed by various means in the studies. studies used a four to five-point Likert scale (six studies), a 10-point scale (two studies), and either a Visual Analog Scale (VAS) or modified VAS (12 studies). One study only measured the swelling. The outcomes were measured over a period of 6 h to 2 years. Most studies measured post obturation pain at 24 or 48 h. A few studies considered increase in the intensity of pain as a flareup while others considered swelling, tenderness as a flareup. Risk of bias: The Joanna Briggs institute (JBI) critical appraisal checklist for randomised controlled trials showed that all the included studies had a moderate risk of bias. Table 2 summarizes the risk of bias assessment. All studies employed some degree of randomisation to assign patients to their respective groups. The patients in both the single and the multiple visit RCT were treated identically. One study had attrition but since nearly equal number of patients from the comparative groups were lost to follow up, it did not affect the outcome. There was no crossover between the treatment groups in any study. The same modalities were employed to assess both groups. The established protocol for the randomised controlled trials were followed and appropriate statistical analysis were done to arrive at a conclusion. There were five parameters--concealment of the treatment groups, the similarity of the patients assigned to the treatment groups, the blinding of the patients, doctors, and the investigators measuring the outcome--which were not followed in any of the studies. Meta-analysis: Of the 21 included studies, only 14 had quantitative data compatible to analyse the incidence of the postendodontic flareup. Quantitative analyses were performed to evaluate the differences in the incidence of the flareup and in the intensity of the flareup between single and multiple visit RCTs. According to the meta-analysis, there is no significant difference (\(p\) = 0.72) in the incidence of flareup in single visit RCT compared to multiple visit RCT (Figure 2). Figure 2: Meta-analysis summarizing the comparison of the incidence of a post endodontic pain and flareup between single and multiple visit root canal treatment (RCT).