Effect of smear layer on sealing ability of canal obturation: a systematic review and meta-analysis

By Shahravan A, Haghdoost A, Adl A, Rahimi H, Shadifar F.

Date: 01/2007
Journal: JOE


  • Purpose: To determine whether smear layer removal reduces leakage of obturated human teeth in vitro
  • Materials/Methods:

  • PubMed was searched for articles published between 1975 and 2005
  • Results were categorized based on the method of leakage test.
  • 26 eligible papers.
  • The records then were divided into five groups based on the type of leakage test and further analysis was performed within each group. These groups were:
  • (a) dye leakage test (44 comparisons); (b) fluid filtration test (7 comparisons); (c) electrochemical test (7 comparisons); (d) bacterial leakage test (6 comparisons); and (e) volumetric dye leakage test (1 comparison).
  • Most highlighted Results:

  • Among 26 eligible papers with 65 comparisons:
  • 53.8% of the comparisons reported no significant difference.
  • 41.5% reported a difference in favor of removing the smear layer.
  • 4.7% reported a difference in favor of keeping it.
  • Of the 65 comparisons, 44 used the dye leakage test for evaluation. The combined effect in this group showed

smear layer removal decreases dye leakage.

  • According to meta-regression, obturation type, test site and duration, sealer and dye, and publication year had no effect on the results.

Clinical significance:

Smear layer removal improves the fluid-tight seal of the root canal system whereas other factors such as the obturation technique or the sealer, did not produce significant effects.