Prevalence of musculoskeletal disorders among dental healthcare providers: A systematic review and meta-analysis

Background: Work-related musculoskeletal disorders (MSD) are common in dentistry due to the prolonged static work involved during patient care, making dental health care personnel vulnerable to musculoskeletal complaints. We aimed to pool the prevalence estimates of MSD among various dental healthcare providers, including dentists, dental students, dental hygienists, and auxiliaries. Methods: A systematic search of five databases was performed (Scopus, Embase, CINAHL, Web of Science, Dentistry & Oral Sciences Source). The studies that reported the prevalence of MSD among dental healthcare workers and those written in English were selected. Screening and data extraction were performed by two review authors independently. Discrepencies were resolved by another review author. Risk of bias assessment was done using a nine-item questionnaire developed by Hoy et al. Pooled estimates were calculated using meta-analysis of proportions (random effects model). Results: Among the 3090 publications screened, 234 publications were included for full-text screening. Meta-analysis was performed for 89 estimates from 88 publications. Females showed significantly higher prevalence [OR = 1.42 (95% CI = 1.09–1.84); I 2 = 66.02; N = 32]. The analysis yielded a pooled estimate of 78.4% (95% CI = 74.8–82). The meta-regression showed similar prevalence over the years (Coefficient: 0.001; P-value: 0.762). Conclusions: A high prevalence of MSD was noted among dental healthcare providers, with about seven out of ten having experienced MSD in the past. This emphasizes the need for awareness and adoption of appropriate ergonomic postures by dental healthcare providers from early in their careers to minimize work-related MSD.


Introduction
"Musculoskeletal disorders (MSD) are injuries to the human support system of muscles, ligaments, tendons, nerves, blood vessels, bones, and joints" (https://www.cdc.gov/). MSDs are defined as musculoskeletal system and connective tissue diseases and disorders when the event or exposure leading to the case is bodily reaction (e.g., bending, climbing, crawling, reaching, twisting), overexertion, or repetitive motion. MSDs do not include disorders caused by slips, trips, falls, or similar incidents (Bureau of Labor Statistics of the Department of Labor. NIOSH workers health chartbook 2004. NIOSH Publication No. 2004-146. Washington, D.C). Such injuries resulting due to occupation or workrelated exposure are termed work-related MSD. Work-related MSD is common in dentistry due to the prolonged static work involved during patient care, making dental health care personnel vulnerable to musculoskeletal complaints. Moreover, the current lifestyle practices make the onset of such problems likely at an early stage of life. MSD includes pain, discomfort, or limitation in a range of activities in the head, neck, shoulders, arms, wrists, fingers, elbows, upper and lower back, buttocks, thighs, feet, ankle, etc.
MSD among dental healthcare personnel can potentially impact the individual and the community. Literature has shown a decrease in work efficiency, stress, poor sleep quality, multisite pain, frequent absenteeism, and/or early retirement resulting in loss of workforce. 1,2 The preventive strategies adopted to mitigate MSD are massage treatments, increased physical activity, adopting ergonomically designed equipment, maintaining correct postures, and using complementary and alternative medicine. 3,4 The studies on self-reported MSD have reported a high prevalence among dental healthcare personnel. [5][6][7][8][9][10] Studies have also evaluated the associated risk factors of MSD among dentists, 7,11-19 dental hygienists, 6,20,21 and dental students. 22,23 Increasing age, gender (female), comorbidities, prolonged working hours, increased patient load, lack of physical exercise, non-usage of loupes, stress, lack of breaks between patients, awkward postures, administrative work, vibration, and repetition were some of the reported risk factors of MSD. 4,24 A few literature reviews and meta-analysis on these conditions have reported a high prevalence among dental healthcare personnel. 25-31 However, there was no attempt to study the overall prevalence estimates of MSD burden among various dental healthcare providers, including dentists, dental students, dental assistants, and auxiliaries at a global level. Hence, we aimed to pool the estimates of the MSD burden among dental healthcare providers.

Inclusion and exclusion criteria
The studies that reported the overall prevalence of MSD among dental healthcare personnel (dentists, dental students, hygienists, or dental auxiliaries), and the studies written in English were included. Only cross-sectional studies and cohort studies, where prevalence data can be extracted or calculated were included. The studies reported as commentaries, letters, or conference abstracts were excluded. The protocol was registered with INPLASY (DOI: 10.37766/inplasy2021.5.0100). 32

Literature search
A systematic search in five databases (Scopus (RRID:SCR_022706), Embase (RRID:SCR_001650), CINAHL (RRID: SCR_022707), Web of Science (RRID:SCR_022706), Dentistry & Oral Sciences Source (RRID:SCR_022705)) from inception to 5 August 2021 was performed. The keywords used were "dentist OR dental hygienist OR dental personnel OR dental student" AND "musculoskeletal disease OR musculoskeletal disorder OR occupational disease OR workrelated musculoskeletal disorder." Suitable filters (reports on humans, research articles) for each database were applied.

Screening
The search was imported to Rayyan, a web-based application (RRID:SCR_017584). 33 The screening and data extraction were done by two review authors independently (MK and MM). Disagreements were arbitrated by another review author (PKC). Agreement between the reviewers for title and abstract screening and full text screening showed almost perfect agreement (Kappa: 0.94 and 0.98 respectively).

REVISED Amendments from Version 1
Minor edits like MSD definition, intra-examiner reliability, additional information on the number of publications sought from databases in PRISMA flow chart, few grammatical errors were included in the manuscript as per the recommendations of the reviewers.
Any further responses from the reviewers can be found at the end of the article

Risk of bias (RoB) assessment
All studies were assessed using the 10 item Quality Assessment Checklist for Prevalence Studies questionnaire 34 by two review authors independently (HS and PKC). Disagreements were arbitrated by another review author (CD). Each question has two levels, low risk (0) and high risk (1). The total of all nine questions was used to categorize the studies as "low (0-3), moderate (4-6), or high risk (7-9)".

Data extraction
The variables for data extraction included study details such as authors, year, country, continent, study design, sample size, type of participants (dentist or dental students, or dental auxiliaries), age distribution, sex distribution, the overall prevalence of MSD at maximum recall along with lifetime, annual, one-week prevalence, gender and site-specific estimates.

Statistical analysis
Due to variation in the reporting of the prevalence of MSD among the included studies, the prevalence estimates at the maximal follow-up were used to calculate the pooled estimates of MSD. Measures of heterogeneity (Q and I 2 ) were calculated. A random-effects model (restricted maximum likelihood estimation method) was used to calculate the prevalence estimates using the OpenMeta[Analyst] software for Windows 8 (Metafor Package 1.4, 1999) (RRID: SCR_022698). Time trends of MSD were evaluated using meta-regression. A sub-group analysis based on the continent, country, type of dental personnel, site of MSD, and sex was performed. A funnel plot was used to evaluate the publication bias. Complete data for the analysis can be accessed at Mendeley datasets. 35

Results
A comprehensive systematic search of five databases (Scopus (1080), Embase (592), CINAHL (728), Web of Science (514), Dentistry & Oral Sciences Source (750)) yielded a total of 3664 articles. Reviews, conference proceedings, case reports, clinical trials, studies on ergonomics, quality of life, burnout, etc. letters, magazine reports, work related hazards other than MSD, studies among health professionals other than dentists were excluded (n = 2856). A further 146 publications were excluded after screening the full-text. Meta-analysis was performed for 89 estimates (Table 1 and Figure 1).

Age
Most of the studies reported the age distribution of the participants (n = 61), while 14 studies reported only the age range of the participants. Prevalence estimates could not be calculated as there was substantial variation in age grouping.

Gender
Most of the studies reported the gender distribution of the participants (n = 80). Only one-third of the studies (n = 32) reported gender-specific estimates.  (Table 2). Females had significantly higher estimates of MSD than males (OR = 1.42) ( Figure 2).       (Table 2). Countries with more than three studies were included for the sub-group analysis. The highest pooled prevalence was seen in Malaysia, and the lowest pooled prevalence was seen in Greece.

Risk of bias (RoB)
Out of the 88 studies included, only four studies had a moderate RoB. 22,52,57,60 The pooled estimates for studies with low and moderate RoB were 79% and 74% (Table 2).

Site distribution
The commonly reported sites were the neck, back, lower back, shoulder, upper back, and wrists. The least affected sites were thighs, legs, arms, feet, and ankles (Table 3).

Meta-analysis
There was high heterogeneity among the included studies, as evidenced by Q and I 2 statistics. The model yielded a pooled estimate of 78.4% (Figure 3), and sensitivity analysis did not show any change in the overall estimate. The metaregression showed no change in the trend of MSD (Coefficient: 0.001; 95% CI: -0.004 to 0.006) (Figure 4). Asymmetry was noted in the funnel plot (p < 0.001) ( Figure 5).

Discussion
MSD's result in pain, discomfort, or limitation in the range of movement. They are preventable conditions often due to poor ergonomic postures adopted by dental health care providers. We aimed to pool the estimates of MSD among dental healthcare providers. Eighty-eight publications recorded a comprehensive assessment of all body areas and reported the overall prevalence of MSD. The estimates needed to be evaluated carefully due to the high heterogeneity. The overall estimate was 78%, which was much higher than Greek and Cezch surveys. 37,80 However, extensive surveys of dentists from India and Lithuania have reported similar or higher prevalence estimates. 3,9,101 Therefore, it is clear that dental professionals have quite a higher prevalence of MSD. Age-specific prevalence estimates could not be estimated due to a lack of standardized age groups or specific prevalence estimates. It was found that females showed higher prevalence estimates than males. Although the number of studies that reported gender distribution was high, only one-third of these studies reported gender-specific estimates of MSD. The prevalence estimates were similar across the continents. The highest number of studies were reported from the Asian continent. The highest number of studies were from India, 3,5,9, There was not much variation in the prevalence estimates among the dentists, dental auxiliaries, and dental students. These observations suggest that all types of dental healthcare providers globally suffer from MSDs due to prolonged static postures. Over three decades, there was no significant change in the trend of MSD, indicating a consistently higher prevalence, highlighting the need to incorporate ergonomics into the dental curriculum.
There was substantial inconsistency in the assessment of prevalence estimates among the studies. The Nordic/standardized Nordic questionnaire was the most commonly used tool to assess MSDs. A few studies used generic questionnaires and single-item questions without adequate validity and reliability. Moreover, the studies used various time recall periods (lifetime, one year, six months, one month, and one week) to assess the prevalence estimates. The studies that used lifetime or extended recall periods might have included pre-existing MSDs that may not be work-related, which could have diluted the estimates of MSD.
MSD can arise from various reasons, and there was a lack of clarity in most of the studies. Only one study explicitly recorded the estimates before and after joining the dental profession. 58 There was a general lack of clarity on the estimates reported for various body parts (shoulders, hands, elbow, wrists, legs, ankles, hips, fingers, toes). The studies reported right, left, and bilateral prevalence estimates of MSD without detailing the prevalence for each site. MSD in such areas could have been reported as unilateral and bilateral rather than right, left, and bilateral estimates. Furthermore, there was no uniformity in the evaluation of site-specific assessments among the studies included (e.g. lack of clarity on the terms hand and arms).  The strength of this review is the inclusion of studies that reported the overall estimates of MSD, including many databases, all types of dental healthcare personnel, overall, lifetime and annual estimates, sub-group analysis, gender, and site-specific prevalence estimates. A few limitations were observed in our study. They are the exclusion of studies published in other languages, lack of age-specific prevalence estimates, lack of differentiation between work-related and pre-existing MSDs, causes of MSDs due to inadequate reporting in primary studies, use of self-reported measures of MSD rather than objective measures, and exclusion of studies with no comprehensive assessment or overall estimates of MSD.
The additional confounding factors related to lifestyle (sedentary lifestyle, lack of regular physical exercise, and other extra-curricular activities) could significantly influence the onset and duration of MSD. Furthermore, the number of clinical working days/week, working hours/day, type and duration of procedures, specialization, number of patients/ days, remedial measures, and history of MSD in the past could also substantially impact the estimates of MSD. These inconsistencies in the included studies could have influenced the overall prevalence of MSD.

Conclusions
MSD among dental healthcare personnel is widespread and mostly chronic. Seven out of ten dental healthcare providers could have experienced MSD in the past. However, the severity and self-limiting nature of MSD cannot be underestimated. Awareness, adoption, and maintenance of appropriate ergonomic postures should be encouraged at dental schools and early in the career. Future studies should use the "Strengthening the Reporting of Observational Studies in Epidemiology (STROBE)" guidelines and use validated questionnaires for reporting MSD.

Open Peer Review
Yes

Are the conclusions drawn adequately supported by the results presented in the review? Yes
Question: What is the reason for the exclusion of 146 publications after the full screening of the full text? 4) Prevalence: There is a repeated word "than than".

5) Geographic distribution:
Question: The authors mentioned that Australia (4), Africa (1), and north and south America (7,4) why not Asia and Europe (N=?)? It may be better to revise this "One study from Africa (N=1)". 6) Figure 1: Question: Where is the N=89 in this chart? Question: What are the other sources used to identify additional records? 7) Are the rationale for, and objectives of, the Systematic Review clearly stated? Yes

Is the statistical analysis and its interpretation appropriate? Yes
Are the conclusions drawn adequately supported by the results presented in the review?