Single- Vs Multiple-Visit Root Canal Therapy

Assessment of preoperative pain is a critical factor in the selection of either single- or multiple-visit RCT. For patients who are experiencing severe pain, with or without swelling, it may be necessary to avoid lengthy appointments, particularly because preoperative pain is significantly associated with postoperative pain.⁵ Therefore, in such cases, treatment should be aimed at pain alleviation and limited to access and instrumentation during the first visit, while deferring obturation to a subsequent appointment. Understanding the length of time that a patient can comfortably tolerate during a visit is central to this decision. Furthermore, providing multiple-visit therapy to patients in significant pain allows clinicians to assess symptom resolution during the second appointment. Ensuring symptom resolution demonstrates the practitioner's concern for his or her patients-a "soft skill" that goes beyond the evidence-based reasoning for providing multiple-visit care. A systematic review revealed that although the radiologic success rates of single- and multiple-visit RCT were similar, analgesic use was significantly less common among patients who underwent the latter approach.⁶

When selecting between single- and multiple-visit therapy, consideration must be given to any clinical findings related to infection, including swelling and the presence of purulent drainage from the root canal spaces or sinus tracts. Multiple-appointment RCT allows providers to assess the effect of treatment on infected tissues and ensure symptom resolution prior to obturation of the root canal space.⁷

Pulpal and periapical diagnoses can be challenging to incorporate into the decision-making process. Consensus is currently lacking regarding the impact of these diagnoses on clinical outcomes. However, establishing pulpal and periapical diagnoses can significantly assist a clinician in deciding between single- and multiple-visit endodontics. For vital teeth, including teeth diagnosed with pulpitis with or without apical periodontitis, a single-visit approach may be appropriate.^3,8 Investigators postulate that vital teeth often have a superficially infected pulp and a relatively uncontaminated canal system; thus, a single-visit approach can allow for greater efficiency in care.⁸ For teeth diagnosed with pulp necrosis, some investigators suggest that the use of an intracanal medication between appointments leads to greater disinfection of the canals, whereas others have found no significant difference in the success rates between the two treatment approaches.^7,9 However, for symptomatic non-vital teeth and asymptomatic non-vital teeth (with apical periodontitis), multiple-appointment treatment is often recommended (Figure 2 through Figure 4).^3,4 In previously treated teeth, a two-visit approach with calcium hydroxide as the intracanal medicament has been shown to be significantly more effective at reducing postoperative pain and flare-ups.¹⁰

The complexity of the presenting case may dictate the choice of a single- or multiple-visit approach to therapy. The American Association of Endodontists' "Endodontic Case Difficulty Assessment Form" can help practitioners determine a case's complexity.¹¹ Complicating factors are not only limited to canal calcifications and root curvatures, but also include the medical history, the patient's disposition and level of compliance, local anesthesia history, emergency conditions, radiographic difficulties, tooth location in the arch, isolation concerns, and a history of trauma.¹¹ Examples of complicating factors that can be found in the medical history include the use of immunosuppressive medications, poorly controlled diabetes, recent myocardial infarction, or an American Society of Anesthesiology physical status classification of class III or above.¹²

A history of complications related to local anesthesia can render cases more challenging and may necessitate multiple-visit therapy. In particular, providing effective pulpal anesthesia for a tooth diagnosed with symptomatic irreversible pulpitis (ie, a "hot" tooth) can be especially difficult and may require supplemental anesthesia, such as a periodontal ligament, intrapulpal, or intraosseous injection.¹³ Although effective, the duration of pulpal anesthesia in such clinical scenarios can be reduced to approximately 30 to 45 minutes.¹³ In addition to a potentially shortened duration of anesthesia, the amount of time required to sufficiently anesthetize a tooth with symptomatic irreversible pulpitis can significantly increase chairtime during treatment. Thus, in cases with such concerns, consideration should be given to performing multiple-visit RCT.

Similar to concerns regarding the medical history and a history of anesthesia complications, the presence and degree of clinical symptoms indicating an endodontic emergency are complicating factors that should also be evaluated when selecting between single- or multiple-appointment therapy. In cases with moderate or severe swelling or pain, a multiple-visit approach allows for the evaluation of symptom resolution at the second visit.⁶ Challenges to obtaining and interpreting radiographs can also hinder the delivery of therapy in a single session. In these cases, anatomical variations, such as the presence of an elevated floor of mouth, tori, narrow or low palatal vault, or superimposed anatomical structures, should be taken into consideration when selecting the treatment modality.¹¹

Beyond radiologic challenges, the location of a tooth in the arch can significantly impact case complexity. Although anterior and bicuspid teeth, as well as teeth with a slight inclination or rotation (ie, < 10°), may allow for single-visit therapy, molars and teeth presenting with a more extensive inclination or rotation (ie, > 30°) offer unique challenges to access preparation that can slow comprehensive treatment and require two or more sessions. Finally, a history of trauma can be a critical factor in deciding the appropriate number of visits for a patient. Cases presenting with minimal difficulty, such as uncomplicated crown fractures, may be addressed in a single-visit session, given that there are no other complications. However, challenging cases, such as those involving avulsion, alveolar fracture, or luxation, may be best addressed through a multiple-appointment approach that allows for a thorough follow-up of symptoms, tooth prognosis, and response to therapy.¹¹ All things considered, when compared with more complex cases, less complicated cases may be more readily treated in a single visit.

Restorative concerns, such as anterior esthetics, issues related to isolation and sealing, and pre-prosthetic factors, can also impact the selection of either single- or multiple-visit therapy. Complicated crown fractures of anterior and bicuspid teeth and horizontal crown fractures at the gum line of anterior teeth commonly involve esthetic considerations. In cases with such concerns, barring other complicating factors, consideration must be given to single-visit RCT to facilitate the rapid placement of a temporary crown in order to restore form, function, and esthetics.¹⁴

Achieving effective isolation and then subsequently sealing the canal system to prevent reinfection are essential components of successful RCT. In most cases, both can be achieved. However, for teeth with subgingival breakdown, missing coronal walls, or full coverage restorations with decay below the margins, adequate isolation and sealing can be particularly challenging. When teeth present with these findings, consideration should be given to single-visit therapy in order to reduce the chances of interappointment contamination and flare-up.¹⁴

The purview of pre-prosthetic concerns includes teeth that require RCT for restorative purposes, rather than for the debridement of pathologic pulp tissue or pulp exposures. Several cases fall within this category, including teeth needed for overdenture abutments, teeth that cannot retain a restoration due to severe coronal breakdown, mandibular anterior teeth that are reduced for full jacket crowns, and teeth that require preparation that would result in pulp exposure for a specifically designed restoration. In such cases, a single-visit approach is encouraged to accelerate the process of restoring form, function, and esthetics of the involved teeth.¹⁴ A summary of the indications for which single- or multiple-visit therapy may be appropriate is presented in Figure 5.

Time and time again, the endodontic literature demonstrates that the outcomes for single-visit treatment and multiple-visit treatment are equivalent. Given these findings, decisions to pursue either approach to treatment must be informed by factors that go beyond prognosis alone. By considering preoperative pain, infection status, pulpal and periapical diagnoses, case complexity, and restorative concerns, clinicians can select the treatment modality that is most appropriate to treat their patients' endodontic needs.

Shraya Sharma
DMD Candidate, Class of 2020
Harvard School of Dental Medicine
Boston, Massachusetts

Rebekah Lucier Pryles, DMD
Upper Valley Endodontics
White River Junction, Vermont
Assistant Clinical Professor
Department of Endodontics
Tufts University
School of Dental Medicine
Boston, Massachusetts

Brooke Blicher, DMD
Upper Valley Endodontics
White River Junction, Vermont
Assistant Clinical Professor
Department of Endodontics
Tufts University
School of Dental Medicine
Boston, Massachusetts
Clinical Instructor
Department of Restorative Dentistry and Biomaterials Science
Harvard School of Dental Medicine
Boston, Massachusetts

Jarshen Lin, DDS
Director of Predoctoral Endodontics
Department of Restorative Dentistry and Biomaterials Science
Harvard School of Dental Medicine
Boston, Massachusetts
Clinical Associate
Department of Oral and
Maxillofacial Surgery
Massachusetts General Hospital
Boston, Massachusetts