Why Some Root Canal Treatments Take More Than One Visit: Study Identifies Key Factors

Single-Visit vs. Multi-Visit Root Canal Treatment

Nonsurgical root canal treatment involves cleaning, shaping, and sealing the infected or damaged inner pulp space of a tooth. Depending on the clinical situation, a dentist may complete this procedure in a single appointment or stage it across multiple visits. Understanding which clinical and patient factors lead to multi-visit procedures can help clarify why treatment timelines vary from person to person.

A study from the National Dental Practice-Based Research Network investigated patient-, tooth-, and dentist-level characteristics to determine what factors are independently associated with completing root canal treatment over more than one visit.

How the Study Was Conducted

The researchers analyzed records from 1,723 patients who received nonsurgical root canal treatment across participating dental practices in the network. The main outcome evaluated was whether the treatment was completed in a single appointment or required multiple visits.

To identify relevant factors, the authors examined patient demographics, preoperative symptoms, clinical and tooth characteristics, procedural difficulty, and dentist-related variables. They used multivariable generalized estimating equation models, a statistical method that accounted for the clustering of multiple patients treated by the same dentists.

Tooth and Patient Factors Linked to Multiple Visits

Across the entire group, 316 patients (18%) received their root canal treatment over more than one visit. The remaining 82% completed their care in a single visit.

Several specific tooth characteristics were significantly associated with needing more than one appointment:

• Molar teeth: Molars, which are located at the back of the mouth and typically have more complex root anatomy, had more than double the odds of multi-visit treatment compared to other tooth types (odds ratio of 2.08).
• Lower jaw location: Teeth in the mandible (the lower jaw) were more likely to involve multiple visits (odds ratio of 1.37).
• Visible swelling: The presence of swelling prior to the procedure increased the likelihood of a multi-visit approach (odds ratio of 1.60).
• Tooth mobility: Teeth exhibiting abnormal movement were also linked to multiple visits (odds ratio of 1.59).

Patient-level factors also played a role. Patients reporting severe preoperative tooth pain had higher odds of multi-visit care (odds ratio of 1.66). In addition, patients identifying as Asian or Hispanic had higher odds of multi-visit treatment (odds ratio of 1.68).

Practice Settings and Inverse Associations

The study also found differences based on the clinical environment and location. Treatment delivered in academic or public dental practices was significantly associated with multi-visit completion (odds ratio of 2.98), as was receiving treatment in the Northeast region of the network (odds ratio of 2.59).

Conversely, two clinical features were inversely associated with multi-visit care, meaning they were more frequently completed in a single visit:

• Vital teeth: Teeth that still had living pulp tissue at the start of treatment had significantly lower odds of requiring multiple visits (odds ratio of 0.48).
• Tenderness to biting pressure: Teeth that were tender to biting pressure were also less likely to be treated in multiple visits (odds ratio of 0.73).

Study Limitations

While the study evaluated a large group of 1,723 patients across diverse practice environments, it has inherent limitations. The findings reflect statistical associations within the National Dental Practice-Based Research Network and do not directly prove that any single factor causes a dentist to schedule multiple appointments. Additionally, regional and institutional variations in treatment protocols may reflect differences in training, scheduling availability, or institutional guidelines rather than purely anatomical needs.

What This Means for Patients

These findings show that root canal scheduling is generally guided by clinical complexity, symptom severity, and specific tooth characteristics rather than a one-size-fits-all routine. Back teeth with multiple roots, active swelling, loose teeth, and severe pain are more frequently managed across multiple appointments to ensure thorough disinfection and care. Conversely, teeth with vital pulp tissue are often suitable for single-visit treatment. Patients can discuss their specific tooth anatomy and symptoms with their dental provider to understand the planned timeline for their care.