Review Reports - Prevalence of Musculoskeletal Disorders in Germany—A Comparison between Dentists and Dental Assistants

Round 1

Reviewer 1 Report

This paper presents an interesting study of MSD prevelance among dentists and dental assistants in Germany.

This paper is weel written and easy to read and understand. The abstract summarize clearly the key fact of the study.

Just few comments:

I would include "In Germany" in the title to better localize the study.
P1-L38: the word "immense" don't sound adequatly
P7-179: "the neck" is used twice.
In the discussion, i think a paragraph about study limits lack. I think you have to explain that dental assistants suffering from MSD could have answer more frequantly than others, ...

Author Response

I would include "In Germany" in the title to better localize the study.

We included the term in the title: Prevalence of musculoskeletal disorders in Germany – a comparison between dentists and dental assistants

P1-L38: the word "immense" don't sound adequately

We changed the term into “tremendous”.

P7-179: "the neck" is used twice.

We deleted the term.

In the discussion, i think a paragraph about study limits lack. I think you have to explain that dental assistants suffering from MSD could have answer more frequantly than others, ...

Thank you for mentioning. We added a section on the limitations in Line 255ff: “A control group would have been helpful to better interpret the prevalences, but such a group was not included in this study. Another limitation is the imbalance in the gender distribution in the occupational groups. However, matching between the genders is impossible in Germany, since 99% of the dental assistants in Germany are female [11]. Since the population in our study matches very well the real world contribution of sexes in this occupational group, we believe this can also be seen as a strength of the study. Unfortunately, it was not possible to collect an exact response rate of the questionnaires. Due to data protection regulations in Germany, it was not possible to obtain the email addresses of the practices via the state medical association and to contact them ourselves. Instead, an open distribution strategy had to be chosen, at trade fairs and via magazine articles. It would also be possible that a majority of people with pain decided to participate in the study.”
We added further explanations to the discussion. Line (244ff): “Further reasons could be that dental treatment units are predominantly dentist-oriented. In addition, patients are oriented in such a way that the dentists have an optimal view in-to the patient's mouth, regardless of ergonomic disadvantages on the part of the assistants. This effect could be additionally reinforced by differences in size between dentists and dental assistants.”

Reviewer 2 Report

This is very interesting and well-prepared study.

Author Response

Thank you very much for revising the manuscript.

Reviewer 3 Report

1.move please the number of partecipants (those who responded to the questionnaire) from materials and methods to the results section

2.in the results section please provide data on the respondents characteristics with a gender differentiated approach: age BMI etc for females and males in both the study groups.

3.in material and methods section provide please with sample size calculation

4.in the results section provide data of the overall response rate.

5.in the results section provide please data on MSD prevalence with a gender-based approach, both for males and for females and provide a graphical representation of these results too (graphs)

6.in the discussion section provide please a comparison of the results of the present study with those of general population, possibly matched for the study % in gender and age range.

7. In the discussion section please provide a possible explanation for the higher prevalence of MDS among the dental assistants group.

8.please state clearly the limitations of this study in the final part ofthe Discussion section:i) to achieve a consistent scientifi soundness the study groups should be matched between females and males; ii) lack of a control group.

Author Response

1.move please the number of partecipants (those who responded to the questionnaire) from materials and methods to the results section

Thank you for the advice. We moved this term to the results section.

Line (135f): “In total 2548 participants took part in this survey of which 711 participants were eligible for further analysis.”

2.in the results section please provide data on the respondents characteristics with a gender differentiated approach: age BMI etc for females and males in both the study groups.

We added subjects characteristics of both females and males and correspondent test for differences to the general characteristics. Since there are only 2 males in the dental assistants group, no statistical tests were conducted between both professions in males.

3.in material and methods section provide please with sample size calculation.

We added the sample size calculation to the methods section. Line (121ff): “With respect to the main objective of the survey questionnaire regarding the prevalence of MSD, it can be assumed with a two-sided 95% confidence interval that with a prevalence of approximately 87% (Meyer and Micheelis 2001), the current prevalence can be accurately calculated with an accuracy of +/- 2%. A survey of 1085 individuals is necessary to obtain this information.”

4.in the results section provide data of the overall response rate.

Originally, the Federal Dental Association was to send the questionnaire directly to practices throughout Germany. Unfortunately, this was not possible for data protection reasons. Data protection regulations are generally very strict in Germany. In order to be able to generate as large a sample as possible, we chose appropriate recruitment methods (as described in Methodology - Recruitment).

5.in the results section provide please data on MSD prevalence with a gender-based approach, both for males and for females and provide a graphical representation of these results too (graphs)

Since only 2 males participated in this survey in the dental assistants group, neither a statistical nor graphical evaluation was possible and reasonable. In the current study the proportion of female dental assistants was 99.4%. As cited in the introduction & discussion, this proportion is representative for the distribution of gender in dental assistants (99.1% in Germany). Thus, we decided that the role of Gender on MSD could only determined with analyses of females in both groups.

6.in the discussion section provide please a comparison of the results of the present study with those of general population, possibly matched for the study % in gender and age range.

We added a comparison to the general population in Germany. Line (210-212): “In total, the comparison of the current findings show, that dental professionals have higher 7-day, 12-month as well as lifetime prevalences in MSD than the general population in Germany [27].”

In the discussion section please provide a possible explanation for the higher prevalence of MDS among the dental assistants group.

We added further explanations to the discussion. Line (244ff): “Further reasons could be that dental treatment units are predominantly dentist-oriented. In addition, the treatment chair is adjusted in such a way that the dentists have an optimal view in-to the patient's mouth, regardless of ergonomic disadvantages on the part of the assistants. This effect could be additionally reinforced by differences in size between dentists and dental assistants.”

We thank you for hinting, that the last version of the manuscript lacked a limitations section. We added the following in Line 255ff: “A control group would have been helpful to better interpret the prevalences, but such a group was not included in this study. Another limitation is the imbalance in the gender distribution in the occupational groups. However, matching between the genders is impossible in Germany, since 99% of the dental assistants in Germany are female [11]. Since the population in our study matches very well the real world contribution of sexes in this occupational group, we believe this can also be seen as a strength of the study. Unfortunately, it was not possible to collect an exact response rate of the questionnaires. Due to data protection regulations in Germany, it was not possible to obtain the email addresses of the practices via the state medical association and to contact them ourselves. Instead, an open distribution strategy had to be chosen, at trade fairs and via magazine articles. It would also be possible that a majority of people with pain decided to participate in the study.”