Is Single-Visit Endo as Successful as Multi-Visit?

Picture the scenario, because you've lived it. You've just finished shaping the MB2 on a maxillary first molar. Isolation is good, the canals are clean, you dry them down, and instead of reaching for sealer, you stop. Calcium hydroxide goes in, a temporary goes on top, and the patient hears "see you in two weeks."

I've done that exact sequence more times than I can count, and so has almost everyone reading this, on the strength of a professor's warning that a hot, necrotic tooth with a periapical radiolucency needs time to heal before you can safely close it, and that finishing in one visit is asking for a weekend flare-up call. That belief wasn't baseless: the irrigants and files of that era genuinely weren't good enough to knock bacterial load down far enough in one sitting, and the interim calcium hydroxide dressing was doing real antimicrobial work while it sat.

The question worth asking now isn't whether that reasoning was ever sound. It's whether the tools that made it necessary are still the tools you're using. Here's what the current endodontic literature says.

The question#

In adults undergoing nonsurgical root canal treatment of a permanent tooth (vital or necrotic, with or without a periapical lesion) does completing obturation in a single visit produce worse outcomes than completing it over two or more visits with an interappointment medication, measured by radiographic healing, tooth loss, post-operative pain, flare-up, or need for further treatment? A meaningful difference is a gap in one of those hard outcomes large enough to change which technique you default to, not a same-week pain report that resolves with an ordinary analgesic regimen.

The mechanism#

Apical periodontitis is a bacterial disease (biofilm inside the root canal system driving an immune response at the apex), and the point of treatment is knocking that bacterial load below the threshold where the patient's own immune system can finish the job. The two-visit tradition rested on a reasonable belief: hand files and passive syringe irrigation couldn't get bioburden down far enough in one sitting, so an interappointment calcium hydroxide dressing sat in the canal a week or two, hydroxyl ions slowly diffusing through the dentinal tubules to finish what instrumentation missed.

That belief was built for a toolkit most of us no longer use. Flexible nickel-titanium rotary systems shape a canal more predictably and create a better reservoir for irrigant than a stiff hand file ever did, and active irrigation (ultrasonic or sonic agitation, driving acoustic streaming and cavitation through the fluid) pushes sodium hypochlorite into fins and isthmuses passive irrigation never reached. The goal didn't change. The single-visit ceiling on how much of it you can achieve did.

That same "the old objection was real, but the tools that created it moved on" pattern shows up elsewhere in endo. See the research on warm vertical versus single-cone obturation, where better sealer chemistry closed a gap that used to require a slower technique.

What the evidence says#

Mergoni, Ganim, Lodi, Figini, Gagliani & Manfredi, 2022: Cochrane systematic review and meta-analysis#

What they did. Cochrane's current update on this exact question, searching through April 2022 and including 47 randomized and quasi-randomized trials (5,805 participants, 5,693 teeth) comparing single-visit to multiple-visit root canal treatment in people over 10. Five prior-version studies were dropped for not meeting current standard of care (rubber dam, sodium hypochlorite irrigation).

What they found. No evidence of a difference in radiological failure at one year or more (risk ratio 0.93, 95% CI 0.81–1.07; 13 studies, 1,505 teeth; moderate-certainty evidence), tooth extraction (very low certainty), swelling or flare-up, analgesic use, or sinus tract presence. The one outcome that did separate the groups: a higher proportion of participants reporting pain within one week after single-visit treatment (risk ratio 1.55, 95% CI 1.14–2.09; moderate-certainty evidence), most pronounced in vital teeth (risk ratio 2.16) 1.

Why it matters. This is 5,805 participants across 47 trials, the largest, most current evidence this question has, and it's precise about what "no difference" means: moderate-certainty evidence for the headline healing outcome, not a footnote finding. It's also precise about what is different: pain in the first week, not pain intensity, not flare-up, not the need for further treatment.

Sathorn, Parashos & Messer, 2005: systematic review and meta-analysis#

What they did. A review isolating the calcium hydroxide question specifically: does single-visit treatment without a calcium hydroxide dressing, versus multiple-visit treatment with one for a week or more, produce a lower healing rate? Three randomized trials, 146 cases total, met inclusion.

What they found. None of the three studies found a statistically significant difference. Pooling them, single-visit trended 6.3 percentage points higher on healing rate, not lower (95% CI −20.3 to 7.8; p=0.38) 2.

Why it matters. This is the paper that actually isolates the calcium hydroxide dressing as the variable, and it found no sign that leaving it out costs you healing. The confidence interval is wide (146 cases is a small base), but if the two-week dressing were doing decisive antimicrobial work the way the old teaching assumed, this is where you'd expect to see it, and it isn't there.

Predictors of success: Ng, Mann, Rahbaran, Lewsey & Gulabivala, 2007–2008: two-part systematic review#

What they did. A hand-searched review of the primary root canal treatment outcome literature through 2002–63 studies in Part 1, with Part 2 pooling data on 24 patient and operative factors to see which ones actually move the success rate.

What they found. Four factors significantly improved outcome: absence of a preoperative periapical radiolucency, a root filling with no voids, a fill extending to within 2mm of the radiographic apex, and a satisfactory coronal restoration 4. Part 1 notes that of the many variables studied, the influence of treatment technique itself, including number of visits, was among the least frequently and least rigorously investigated 3.

Why it matters. This isn't a head-to-head trial of single- versus multi-visit; it's the bigger question of what, across the literature, actually predicts success. Number of visits doesn't make the list of four. Obturation quality and a good coronal seal do: the exact thing a leaking temporary between appointments puts at risk.

Penesis, Fitzgerald, Fayad, Wenckus, BeGole & Johnson, 2008: randomized controlled trial#

What they did. Ninety-seven patients with necrotic teeth and apical periodontitis were randomized to one-visit or two-visit root canal treatment, the two-visit group receiving an interim calcium hydroxide/chlorhexidine paste dressing. Sixty-three patients (33 one-visit, 30 two-visit) were evaluated at 12 months using the periapical index.

What they found. Both groups showed equally favorable periapical healing at 12 months, with no statistically significant difference between them 5.

Why it matters. A direct clinical trial on exactly the population the old teaching worried about most (necrotic teeth with periapical lesions) followed a full year, long enough for late failures to declare themselves. It didn't find the gap the two-visit tradition predicts.

Evidence at a glance#

Study	Design	Sample	Follow-up	Finding	Weight
Mergoni et al., 2022 1	Cochrane systematic review & meta-analysis	47 trials, 5,805 participants	≥1 year	No difference in radiological failure; more 1-week pain, single-visit	High
Sathorn et al., 2005 2	Systematic review & meta-analysis	3 RCTs, 146 cases	Varied	Single-visit trended 6.3pp higher healing, not significant	Moderate
Ng et al., 2007–2008 34	Two-part systematic review	63 studies	Varied	4 significant predictors; visit count not among them	Moderate
Penesis et al., 2008 5	RCT	63 teeth, 97 enrolled	1 year	Equally favorable healing, no significant difference	Moderate

Risk ratio, single-visit versus multi-visit root canal treatment. A ratio crossing 1.0 means the trial found no reliable difference. Data from Mergoni et al., 2022 1.

Where the evidence is thin#

• Cochrane's own risk-of-bias grading on the underlying 47 trials is mixed: 10 low risk, 17 high, 20 unclear, which is exactly why the headline finding is graded moderate, not high, certainty.
• Secondary outcomes are unstable across review updates. The prior version of this same Cochrane review found a difference in analgesic use between groups; the current, larger update does not.
• No trial isolates the calcium hydroxide dressing from the second débridement pass that comes with it. A multi-visit protocol gets both; Sathorn's meta-analysis comes closest to isolating the dressing alone, on only 146 cases.
• Ng's predictor data doesn't test single- versus multi-visit directly, and it predates modern rotary systems and bioceramic sealers entirely (search cutoff 2002).
• Tooth extraction (arguably the outcome patients care most about) has the thinnest data of all: two studies, very low certainty. Nobody has run the large, modern trial that would settle it specifically.

What this means Monday morning#

1. Build a protocol that maximizes single-visit disinfection, and default to it. Good anesthesia, rubber dam, straight-line access, patency to the apex, full-strength sodium hypochlorite replenished throughout, active irrigation to drive it into isthmuses, a final EDTA rinse followed by a NaOCl flush, and dry paper points with no persistent exudate before you obturate.
2. Manage the real finding (first-week pain) rather than avoiding the technique over it. A long-acting local anesthetic like bupivacaine before the patient leaves, plus a scheduled (not PRN) ibuprofen-and-acetaminophen regimen, covers the actual, verified risk without giving up the efficiency.
3. Seal the coronal access immediately, same visit. A satisfactory coronal restoration is one of Ng's four significant predictors: place a bonded core buildup while the dam is still isolating the field, rather than leaving a temporary that can leak and reinfect a canal system you just disinfected. What that tooth needs next is its own decision. See the research on posts after root canal treatment.
4. Reserve two visits for real exceptions: an acute apical abscess with active, unstoppable drainage, or a complex retreatment where you genuinely can't get canals clean and dry in one sitting.
5. Run your own numbers before assuming the time savings are trivial. Ryan's own arithmetic, illustrative rather than a research finding: a $1,200 molar root canal done in one 75-minute visit clears more per hour than the same fee split across a 60-minute access appointment and a 45-minute obturation appointment, once you count the second room turnover and the slot that could have gone to a new patient. Run your own fee and time against the daily break-even calculator.

The bottom line#

Single-visit and multi-visit root canal treatment heal about the same, on the biggest evidence endodontics has produced on the question: 47 trials, nearly 5,800 participants, no meaningful gap in healing. The number of visits was not a factor. What multi-visit buys you is a slightly lower chance of first-week pain; what it costs you is a second appointment, a temporary sitting in a system you just disinfected, and chair time you could spend elsewhere. For the routine case, finish it.

References#

1. Mergoni G, Ganim M, Lodi G, Figini L, Gagliani M, Manfredi M. Single versus multiple visits for endodontic treatment of permanent teeth. Cochrane Database of Systematic Reviews. 2022;12(12):CD005296. DOIPubMed
2. Sathorn C, Parashos P, Messer HH. Effectiveness of single- versus multiple-visit endodontic treatment of teeth with apical periodontitis: a systematic review and meta-analysis. International Endodontic Journal. 2005;38(6):347-355. DOIPubMed
3. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature - part 1. Effects of study characteristics on probability of success. International Endodontic Journal. 2007;40(12):921-939. DOIPubMed
4. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature -- Part 2. Influence of clinical factors. International Endodontic Journal. 2008;41(1):6-31. DOIPubMed
5. Penesis VA, Fitzgerald PI, Fayad MI, Wenckus CS, BeGole EA, Johnson BR. Outcome of one-visit and two-visit endodontic treatment of necrotic teeth with apical periodontitis: a randomized controlled trial with one-year evaluation. Journal of Endodontics. 2008;34(3):251-257. DOIPubMed

This article summarises published research for clinicians. It is not a substitute for your own reading of the studies or your clinical judgment.