Apical Periodontitis – Is treatment with modern root canal instrumentation more effective?


Apical Periodontitis (AP) is a periapical diagnosis term defined by the American Association of Endodontists (AAE terminology consensus, 2009) as the inflammation and destruction of the apical periodontium that is of pulpal origin. It can appear as an apical radiolucency depending upon the stage of disease. If symptomatic, painful response to biting and/or percussion or palpation is indicative of AP. Half of the adult population worldwide have at least one tooth with apical periodontitis according to Tibúrcio-Machado et al. (Tibúrcio-Machado et al, 2021)

Endodontic treatment is globally recognised as the treatment of choice in the management of AP to maintain the affected tooth on the arch as a functional unit and restore a healthy periodontium. (Nair, 2004) Before introducing nickel-titanium (NiTi) files, instrumentation of root canals was completed using hand instrumentation with stainless steel files. Although instrumentation is not defined as the sole factor for successful endodontic treatment, it does contribute to the chemo-mechanical disinfection of the root canal system hence why an effective instrumentation is crucial.

The aim of this systematic review and meta-analysis is to answer two questions:

  • In patients with apical periodontitis, what is the effectiveness of root canal instrumentation performed with contemporary techniques in comparison with ‘traditional’ (conventional stainless-steel instruments) technique in terms of clinical and patient-related outcomes?
  • In patients with apical periodontitis what is the effectiveness of root canal instrumentation performed with contemporary engine-driven NiTi instruments compared with other types of contemporary engine-driven NiTi instruments (with different design and/or technology) in terms of clinical and patient-related outcomes?


A protocol was registered with PROSPERO and was developed, conducted, and reported using PRISMA guidelines. Searches were conducted using Clarivate Analytics’ Web of Science, Scopus, PubMed, and Cochrane Central Register of Controlled Trials along with a grey literature and major journal contents search. Studies reporting outcomes of the treatment of AP in the general population with engine driven NiTi instruments and stainless-steel conventional instruments published in English language only before December 2021 were considered. Two calibrated reviewers independently screened, selected studies, and extracted data with quality assessment and risk of bias being assessed using Cochrane risk-of-bias (RoB) for randomized control trials and the Newcastle-Ottawa Scale for retrospective studies. The main outcomes measured were tooth survival, pain, tenderness, swelling, need for medication, radiographic evidence of reduction of apical lesion size and radiographic evidence of normal periodontal ligament space. A qualitative and quantitative analysis was performed for a selected studies and a meta-analysis conducted for the outcome ‘radiographic evidence of normal periodontal ligament space or reduction of apical lesion size’ using the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) approach for qualitative analysis.


  • 9 studies (6 RCTs and 3 retrospective clinical studies) involving a total of 2029 patients were included.
  • Tooth survival: Only 1 study matched the inclusion criteria therefore no meta-analysis could be performed. There were no significant differences in tooth survival between NiTi instrumentation compared to conventional instrumentation.
  • Healing of AP: 2 retrospective studies and 1 RCT matched inclusion criteria. Meta-analysis indicated a favourable outcome using contemporary instrumentation in comparison with conventional instrumentation OR = 2.07 (95%CI; 1.25 to 3.44). The authors suggest a cautious interpretation of these results due to high methodological variability.
  • Oral health-related quality of life: Only 1 study matched the inclusion criteria and no clear conclusion could be drawn due to bias according to the authors.
  • Postoperative pain (PP): 7 studies matched inclusion criteria. No meta-analysis could be performed due to high methodological variability. No significant differences were detected between conventional and contemporary groups and no pain was present at 7 days post operatively except for significantly higher PP when retreatment procedures were performed with reciprocation instead of rotation even up to day 7.


The authors concluded:-

Both the classic technique using stainless steel hand instruments and the contemporary approaches with nickel-titanium instruments regardless of their design and technique are similar in the incidence of postoperative pain and associated OHRQoL and lead to comparable results in terms of treatment outcome, except for the following conclusions obtained from individual studies

  • higher incidence of procedural errors and associated lower success rate for primary root canal treatment of teeth prepared with stainless steel files compared with the use of NiTi instruments.
  • higher intensity of PP when retreatment procedures were performed with reciprocation instead of rotation even up to day 7.
  • using contemporary endodontic techniques in general for initial root canal treatments reduces the need of further nonsurgical or surgical retreatments.

In terms of healing, the results of the meta-analysis—based on a low quality of evidence (GRADE)—determined the higher effectiveness of root canal instrumentation performed with contemporary techniques in comparison with ‘traditional’ (conventional stainless-steel instruments) in patients with AP followed for a minimum of 1 year.


The authors registered a protocol for the trial on PROSPERO and searched a number of major databases limiting themselves to English language.  They did note that the grey literature sources did not provide any additional material. Their research protocol was strong and enhanced by standard tools for critical evaluation. 9 studies were identified including 2029 patients to address their two questions. High variability in methodology and design were noted by the authors who stated that the current available studies were not sufficiently standardised to draw reliable conclusions. This translated in the meta-analysis which could only be conducted for one outcome and was considered of low quality according to the GRADE tool. The authors highlight that even though NiTi seems to be superior to conventional instruments, instrumentation cannot be considered as the sole parameter to investigate outcomes such as PP or OHRQoL.

Despite not directly addressing their initial questions, the findings described below by the authors could be valuable to clinicians in their daily practice:

  • Apical preparation sizes exceeding three sizes larger than the first apical binding instrument/file seem not to have any advantage in terms of Periapical Index outcome
  • Regardless of the instrument and technique used, foraminal enlargement seems to be associated with an increased risk of PP in teeth with AP
  • Special techniques associated with an instrumentation through the apical constriction into the centre of large APs in certain indications may have favourable outcomes regarding postoperative pain
  • A favourable outcome in terms of apical healing and tooth survival is reported when achieving patency at the apical foramen (Ng et al., 2011). Thus, the patency concept is still an important aspect in attaining favourable endodontic treatment outcome.

The authors highlight that this systematic review is part of a series of high-quality systematic review designed to inform guidelines for the European Society of Endodontics. They acknowledge the lack of standardized studies with reproducible outcomes required to establish statements based on evidence. Therefore, further high-quality studies with standardized outcomes are required (El Karim & al, 2022).


Primary paper

Bürklein, S. & Arias, A. (2022) Effectiveness of root canal instrumentation for the treatment of apical periodontitis: A systematic review and meta-analysis. International Endodontic Journal, 00, 1– 27. Available from: https://doi.org/10.1111/iej.13782

Review protocol on PROSPERO

Other references

El Karim, I, Duncan, HF, Cushley, S, Nagendrababu, V, Kirkevang, L-L, Kruse, C, Chong, BS, Shah, PK, Lappin, MJ, McLister, C, Lundy, FT, Clarke, M. (2022) Establishing a Core Outcome Set for Endodontic Treatment modalities. International Endodontic Journal, 55, 696– 699. Available from: https://doi.org/10.1111/iej.13749

Glickman GN. AAE consensus conference on diagnostic terminology: background and perspectives. J Endod 2009;35:1619

Nair, P.N. (2004) Pathogenesis of apical periodontitis and the causes of endodontic failures. Critical Reviews in Oral Biology and Medicine, 15, 348–381.

Tibúrcio-Machado CS, Michelon C, Zanatta FB, Gomes MS, Marin JA, Bier CA. The global prevalence of apical periodontitis: a systematic review and meta-analysis. Int Endod J. 2021 May;54(5):712-735. doi: 10.1111/iej.13467. Epub 2021 Jan 22. PMID: 33378579.

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