Title Smear Layer Removal Improves Treatment Outcome in Pulpectomy of Primary Teeth and Seondary RCT (Retreatment) of Permanent Teeth
Clinical Question In patients in need of root canal treatment, does removing smear layer compared to not removing it improve the clinical outcome?
Clinical Bottom Line In pulpectomy of primary teeth and retreatment of permanent teeth, removing the smear layer improves the clinical outcome. However, removing smear layer in primary root canal treatment of permanent teeth is not associated with an improvement in clinical outcome.
Best Evidence  
PubMed ID Author / Year Patient Group Study type
(level of evidence)
21366626Ng/2011 Primary RCT (1170 roots, 702 teeth, 534 patients); secondary RCT (1314 roots, 750 teeth, 559 patients)Prospective Cohort Study
Key resultsIn the evaluation of periapical health as an important success indicator of root canal treatment, use of EDTA to remove the smear layer was not associated with a significant improvement in periapical healing in primary endodontic treatment (odds ratio: 1.26, P = 0.4), but the use of EDTA in secondary treatment (retreatment) was associated with a significant, twofold improvement in clinical outcome (odds ratio: 2.28, P= 0.002).
26696099Pintor/20162 articles reporting on 118 teethSystematic review of randomized trials
Key resultsThe review concluded that there was an improvement in the clinical outcome when smear layer was removed in root canal treatment of primary teeth with clinical signs and symptoms of a necrotic pulp. No meta-analysis was performed.
Evidence Search ("smear layer"[MeSH Terms] OR ("smear"[All Fields] AND "layer"[All Fields]) OR "smear layer"[All Fields]) AND removal[All Fields] AND ("treatment outcome"[MeSH Terms] OR ("treatment"[All Fields] AND "outcome"[All Fields]) OR "treatment outcome"[All Fields])
Comments on
The Evidence
Ng/2011 included a large sample size with an appropriate follow-up time of 2-4 years. In this study, prognostic factors were defined as factors affecting the success at 5% significance level or having a large effect on it at 10% significance level. The intra- and interobserver agreement in radiographic assessment was assessed (intraobserver agreement, K = 0.80; interobserver, K = 0.83), and the authors also took into consideration potentially confounding factors during the statistical analysis. The outcome was assessed based on the clinical and radiographic absence of periodontitis and healing by each root, which is an appropriate way to evaluate endodontic treatment. Pintor/2016 is a systematic review in which the authors, after reviewing hundreds of articles, included only two randomized controlled trials in their qualitative review. One of these two studies was identified as having a high risk of bias according to the criteria. Although the number of initially identified articles was high (1,983), two articles reporting on 118 teeth is a very low number to support a solid outcome in a systematic review. Both of these studies were conducted on primary teeth, so this systematic review does not provide any clinical evidence on removing the smear layer in RCT of permanent teeth. Although there is considerable research about changes in intra-canal bacterial load, amount of leakage after removing smear layer, and better adaptation of obturation material, there is not enough data supporting the positive clinical outcome of smear layer removal. More clinical studies followed by a systematic review are needed to shed light on its true clinical impact.
Applicability Considering the chelating effect of EDTA and its potential to weaken the dentinal structure and its widespread use, it is essential to know whether smear layer removal improves clinical outcome in endodontic treatments or not.
Specialty (Endodontics)
Keywords Smear layer removal, EDTA, ethylenediaminetetraacetic acid, treatment outcome, root canal treatment, RCT, periapical health
ID# 3316
Date of submission 04/25/2018
E-mail hossein.zarezadeh@ucdenver.edu
Author Hossein Zarezadeh
Co-author(s) Pegah Memar Ardestani
Co-author(s) e-mail Pegah.memarardestani@ucdenver.edu
Faculty mentor Dr. Manpreet Sarao
Faculty mentor e-mail Manpreet.sarao@ucdenver.edu
Basic Science Rationale
(Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?)
None available
Comments and Evidence-Based Updates on the CAT
None available