On 2014 Sep 13, Vahid Rakhshan commented:

A detailed version of this review and the author's response can be found from this address (LINK).

Results

(1) In the methods, it was stated that ANOVA and Duncan post hoc test had been used to analyze the data. However, in the results, it was Tamhane post hoc test. These two completely differ.

(2) There was not even any mention of the name ANOVA or its P values.

(3) There were numerous pairwise comparisons in this study. However, most of them had not been reported and even many of comparisons that had been reported, lacked P values.

(4) Finally, it is stated that “For further elucidation of the reasons for ion release in the different solutions, the pH values of the 3 mouthwashes and distilled deionized water were measured.”… (A) The pH of mouthwashes should have been reported in the Methods section, not at the end of the Results. (B) A statistical test was needed for this purpose.

Discussion

(5) It is stated (p 732) that “all release is completed within 4 weeks”. The level of ion release reduces after sometime, but does not finish in the said period or even longer.^1,2

(6) This sentence (p 732) should have been stated very cautiously: “Chlorhexidine … caused not significantly higher release of copper than did Persica” A non-significant result is not of internal validity to be stated like something valuable.

(7) I could not understand the next sentence: “Since the pH values for mouthwashes had no significant difference in the acidity of the 3 mouthwashes, this could be attributed to the corrosiveness of chlorhexidine compared with the other 2 mouthwashes”… How did the authors find out that the pH values were not significantly different? This sentence was quite incorrect. Also the rest of the sentence was vague.

(8) I simply did not understand this sentence (after carefully reading the whole paper for some times): “We measured the means of ions released from every bracket in separate vials, but, on the basis of about 20 brackets in a patient’s mouth in clinical use, the results might become clinically significant.” What result might become significant? What are the authors talking about? There was no clue in the previous or later paragraphs.

Conclusion

Overall, conclusions were few and unsubstantiated. (9) The comparisons reported do not substantiate the first sentence of conclusions.

(10) The second sentence is not at all relevant to this study. It was not at all based on the findings or even the scope of this article.

Abstract

(11) Many of comparisons were done at a level of significance adjusted to 0.008. However, in the abstract “P < 0.05” or “P > 0.05” are introduced as indicators of statistical significance or lack of it.

References

1. Amini F, Rakhshan V, Mesgarzadeh N. Effects of long-term fixed orthodontic treatment on salivary nickel and chromium levels: a 1-year prospective cohort study. Biol Trace Elem Res 2012;150:15-20.

2. Amini F, Rakhshan V, Sadeghi P. Effect of fixed orthodontic therapy on urinary nickel levels: a long-term retrospective cohort study. Biol Trace Elem Res 2012;150:31-6.

On 2014 Sep 13, Vahid Rakhshan commented:

A detailed version of this review and the author's response can be found from this address (LINK).

Results

(1) In the methods, it was stated that ANOVA and Duncan post hoc test had been used to analyze the data. However, in the results, it was Tamhane post hoc test. These two completely differ.

(2) There was not even any mention of the name ANOVA or its P values.

(3) There were numerous pairwise comparisons in this study. However, most of them had not been reported and even many of comparisons that had been reported, lacked P values.

(4) Finally, it is stated that “For further elucidation of the reasons for ion release in the different solutions, the pH values of the 3 mouthwashes and distilled deionized water were measured.”… (A) The pH of mouthwashes should have been reported in the Methods section, not at the end of the Results. (B) A statistical test was needed for this purpose.

Discussion

(5) It is stated (p 732) that “all release is completed within 4 weeks”. The level of ion release reduces after sometime, but does not finish in the said period or even longer.^1,2

(6) This sentence (p 732) should have been stated very cautiously: “Chlorhexidine … caused not significantly higher release of copper than did Persica” A non-significant result is not of internal validity to be stated like something valuable.

(7) I could not understand the next sentence: “Since the pH values for mouthwashes had no significant difference in the acidity of the 3 mouthwashes, this could be attributed to the corrosiveness of chlorhexidine compared with the other 2 mouthwashes”… How did the authors find out that the pH values were not significantly different? This sentence was quite incorrect. Also the rest of the sentence was vague.

(8) I simply did not understand this sentence (after carefully reading the whole paper for some times): “We measured the means of ions released from every bracket in separate vials, but, on the basis of about 20 brackets in a patient’s mouth in clinical use, the results might become clinically significant.” What result might become significant? What are the authors talking about? There was no clue in the previous or later paragraphs.

Conclusion

Overall, conclusions were few and unsubstantiated. (9) The comparisons reported do not substantiate the first sentence of conclusions.

(10) The second sentence is not at all relevant to this study. It was not at all based on the findings or even the scope of this article.

Abstract

(11) Many of comparisons were done at a level of significance adjusted to 0.008. However, in the abstract “P < 0.05” or “P > 0.05” are introduced as indicators of statistical significance or lack of it.

References

1. Amini F, Rakhshan V, Mesgarzadeh N. Effects of long-term fixed orthodontic treatment on salivary nickel and chromium levels: a 1-year prospective cohort study. Biol Trace Elem Res 2012;150:15-20.

2. Amini F, Rakhshan V, Sadeghi P. Effect of fixed orthodontic therapy on urinary nickel levels: a long-term retrospective cohort study. Biol Trace Elem Res 2012;150:31-6.