Dental journal gives plenty to chew on in retraction of resin paper

jprostoThe Journal of Prosthodontics has retracted a 2006 paper by a pair of Saudi researchers and given them a pass because of an alleged lack of grasp of English — and, we’d add, publishing ethics.

The article, titled “Effect of Chemical Disinfectants and Repair Materials on the Transverse Strength of Repaired Heat-Polymerized Acrylic Resin,” was written by Ayman Ellakwa and Ali El-Sheikh, from institutions in Dammam, Saudi Arabia.

The paper’s abstract stated: 

Purpose: The purpose of this study was to evaluate both the effects of immersion in different chemical disinfectant solutions and the type of repair material on the transverse strength of repaired heat-polymerized acrylic resin.

Materials and Methods: A total of 110 rectangular specimens (65 × 10 × 3 mm) of heat-polymerized acrylic resin (Triplex) were fabricated. After polymerization, the specimens were polished, then stored in distilled water at 37°C for 1 week. The specimens were divided into 11 groups (n = 10) coded A to K. Specimens of Group A remained intact (control). The specimens of Groups C to F and Groups H to K were immersed in the following chemical disinfectant solutions (1%, 2.5%, and 5.25% sodium hypochlorite and 2% glutaraldehyde, respectively) for 10 minutes. The specimens of all groups except those of Group A were sectioned in the middle to create 10 mm gaps and repaired with the same resin (Groups B to F) and autopolymerizing acrylic resin (Groups G to K). The specimens of Groups C to F and Groups H to K were again immersed in the disinfectant solutions in the same sequence. The transverse strength (N/mm2) was tested for failure in a universal testing machine, at a crosshead speed of 5 mm/min. Two-way analysis of variance (ANOVA) was performed to evaluate the effects of both the disinfectant solutions and repair materials on the transverse strength of repaired specimens. All data were statistically analyzed using one-way analysis of variance followed by Tukey’s test at 95% confidence level.

Results: The repaired specimens treated with/without disinfectant solutions showed similar (p > 0.05) transverse strength values. No differences (p > 0.05) were detected among the repaired specimens either with heat-polymerized or autopolymerizing acrylic resins. The intact specimens showed transverse strength values (86.9 ± 11.8) significantly higher (p < 0.05) than the values of the repaired specimens.

Conclusions: Among the repaired specimens, transverse strength was not affected after immersion in the disinfectants for the immersion period tested (10 min). The repair material, either heat-polymerized or autopolymerizing acrylic resin, had no effect on the transverse strength of the repaired acrylic resin specimens.

Here’s the notice:

The following article from Journal of Prosthodontics, “Effect of Chemical Disinfectants and Repair Materials on the Transverse Strength of Repaired Heat-Polymerized Acrylic Resin,”[4] by Ayman E. Ellakwa and Ali M. El-Sheikh, published online on September 4, 2006 in Wiley Online Library (, has been retracted by agreement between the authors, the journal Editor-in-Chief, Dr. David A. Felton and Wiley Periodicals, Inc. While the Editor feels confident that the results of the study are valid and the research itself was ethical, the retraction has been agreed to due to significant overlap with three previously published articles,[1-3] partly as a result of the authors’ unfamiliarity with the English language.

The three references are to the following papers:

  • Orsi IA, Andrade VG: Effect of chemical disinfectants on the transverse strength of heat-polymerized acrylic resins submitted to mechanical and chemical polishing. J Prosthet Dent 2004;92:382–388
  • Rached RN, Powers JM, Del Bel Curry AA: Repair strength of autopolymerizing, microwave, and conventional heat-polymerized acrylic resins. J Prosthet Dent 2004;92:79–82
  • Paravina AC, Machado AL, Giampaolo ET, et al: Effects of chemical disinfectants on the transverse strength of denture base acrylic resins. J Oral Rehabil 2003;30:1085–1089

Although we get why the authors might want to stress how valid and ethical their results were, we’re not sure why the editor felt it was so important to note that in the retraction notice. We’re guessing the authors of the plagiarized papers would believe such as statement buries the lead. But we’re not quite convinced by the lack of familiarity with English claim.

After all, the first author is on the faculty  at the University of Sydney — where, we’re pretty sure, they speak English fluently. As they do in England, we’re told. That’s where we see a listing for the second author, El-Sheikh, who evidently has spent time at University College London.

While we’re all for giving authors the benefit of the doubt, we doubt the benefit of letting them make a mockery of the retraction process.

0 thoughts on “Dental journal gives plenty to chew on in retraction of resin paper”

  1. This reminds me of the psychology lecturer (at a university in England) who was jailed for contempt of court for googling the defendant while the judge had made it clear to the jury that this was not allowed. She claimed that she hadn’t understood the judge’s instructions because her English wasn’t good enough.

  2. Very few of the researchers from abroad at our Dutch university speak Dutch. More relevantly, the level of English also varies considerably. Just because someone is employed at an English-speaking university does not mean their English is fluent. Of course the correct course is then to ask a native-speaker for help or to employ proper citation practices, not to just copy-past.

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