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Potential systematic error in laboratory experiments on microbial leakage through filled root canals: review of
D-K Rechenberg1, G De-Deus, M Zehnder
1Department of Preventive Dentistry, Periodontology and Cariology, University of Zürich Center of Dental Medicine, Zürich.
Aim:
To systematically evaluate whether published studies on microbial leakage through filled root canals in human teeth embedded in a two-chamber system were properly controlled. Specifically, the control for the assumption that leakage should occur through the root canal rather than other routes was investigated.
Methodology:
A systematic search was conducted using Medline, Biosis, Cochrane, Embase, and Web of Science databases. In addition, the reference lists of review articles pertaining to the topic were searched. No language restriction was applied. Two independent reviewers screened titles and abstracts. All articles deemed appropriate by either reviewer were included in the full-text evaluation. In case of disagreement, a referee arbitrated between the reviewers.
Results:
With 93.8% agreement prior to discussion and arbitration, 67 articles were included. On average, the size of the negative control group was 30% (mean) of the n in the experimental groups (minimum=0.0%, maximum=100%, SD=27%). The majority of studies (57 of 67) used inadequate negative controls. The whole root was covered with the sealing material in these specimens, whilst the root tip was left uncovered in the experimental groups. Consequently, leakage between outer root surface and sealing material was not controlled for. The authors of the remaining 10 communications did not state clearly how negative control assessments were performed.
Conclusions:
Experimental investigations should be performed to assess the routes of microbial leakage in two-chamber models.
Insights
Most studies on microbial leakage in filled root canals used inadequate controls, failing to isolate leakage through the canal itself. Further research is needed to properly assess microbial leakage routes in two-chamber models.
Area of Science:
- Endodontics
- Microbiology
- Dental Materials Science
Background:
- Microbial leakage through filled root canals is a significant concern in endodontic treatment.
- Two-chamber systems are commonly used to study this leakage.
- Proper experimental controls are crucial for valid results.
Purpose of the Study:
- To systematically evaluate the adequacy of controls in published studies on microbial leakage through filled root canals.
- To specifically investigate how studies controlled for leakage occurring through routes other than the root canal.
Main Methods:
- A systematic literature search was performed across major scientific databases (Medline, Biosis, Cochrane, Embase, Web of Science).
- Reference lists of relevant review articles were also searched.
- Two independent reviewers screened titles and abstracts, with a third reviewer arbitrating disagreements. Full-text articles were evaluated.
Main Results:
- 67 articles were included in the review.
- The majority of studies (57/67) employed inadequate negative controls.
- Inadequate controls often involved leaving the root tip uncovered in experimental groups while sealing the entire root, thus not controlling for leakage along the outer root surface.
Conclusions:
- Published studies on microbial leakage in two-chamber models frequently lack proper controls.
- The common methodology does not adequately isolate leakage through the root canal.
- Experimental investigations are recommended to accurately assess microbial leakage routes in these models.
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