## 4 Discussion  
Endodontic procedures can make patients apprehensive. The development of procedural complications and emergencies can further increase this apprehension [17]. Severe pain and flareup after root canal treatment reflect the clinical expression of complex physiological changes occurring at a cellular stage [37]. There are three possible outcomes once endodontic therapy begins--no symptoms, tolerable pain or pressure (rare) or development of severe pain and/or swelling leading to an unscheduled clinical visit [38]. The last outcome is detrimental to the patient's well-being and the clinician must consider the factors which contribute to it and minimize or eliminate them. Factors such as single/multiple visits, the involvement of vital/nonvital teeth, pre-/ postoperative pain, demographic status, chemo-mechanical cleaning, estimation of pain, etc., govern the occurrence of postobturation or interp appointment pain and flareups that cause discomfort after endodontic therapy/RCT. In this review, the occurrence of severe pain and/or swelling in relation to the number of visits for endodontic therapy was researched. Since endodontic treatment techniques are constantly evolving, the aim was to concentrate on the more common methods of the present day. The search was thus restricted to the past two decades. The search resulted in 21 clinical trials conducted in the last 20 years. The inclusion of studies was not restricted by specifying the technique of endodontic treatment used or the preoperative conditions of the tooth. The aim was to evaluate if the number of visits were a primary determinant of postoperative pain and flare up. The studies were evaluated qualitatively using the JBI tool for critical appraisal of randomised controlled trial. Those found to have a high risk of bias were to be excluded  
Figure 4: Meta-analysis summarizing the comparison of the intensity of postendodontic pain and flareup between single and multiple visit RCT as measured by the modified VAS with a pain scale of 1 to 170. Figure 3: Meta-analysis summarizing the comparison of the intensity of postendodontic pain and flareup between single and multiple visit RCT as measured by the standard visual analogue scale (VAS) with a pain scale of 1 to 10.  
from review. The JBI tool is a questionnaire used to assess the quality of trials by binary answers (yes/no). However, the tool is not a mere checklist to be ticked off. The JBI manual of evidence synthesis describes the method of using it in detail. We found a moderate risk of bias in the included studies. Most studies were inadequate in the blinding. The lack of blinding of patients and operating dentists is justified. Patients and doctors would be aware of receiving a single or a multiple visit. It was possible to blind the assessor, who could be ignorant of the treatment and solely measure outcomes. The studies lacked data on matching patients between treatment groups. Thus, it is possible that there were potential confounders which in turn could have affected the outcome and increased the overall risk of bias. Multivisit endodontics are usually performed to guarantee the root canal system's sterility before obturation to minimize the microbial loads present in the affected canals by the placement of a temporary seal and intracanal dressing until the next visit [39]. Single-visit therapy raises the concern that patients can develop postoperative pain post obturation but also offers the advantage of eliminating a temporary seal and interpapointment leakage [40]. It also reduces chairside time and visits and has increased patient acceptance [35; 41] Conversely, single-visit procedures eliminate certain controls present in multivisit treatment, such as culturing microbes to provide specific antimicrobials if necessary [42]. The evolution of materials, instruments and a better understanding of internal tooth anatomy have transformed the treatment of routine cases, reducing postoperative issues, particularly pain [43].