Perception of risk factors at work associated with musculoskeletal symptoms in dental students of Melaka,Malaysia: A cross-sectional study

Abstract

BACKGROUND:

Dental professionals have been reported to be constantly exposed to work-related musculoskeletal disorders with symptoms often started as early as the student phase. Risk perception may play an important role in modifying risk at work.

OBJECTIVE:

To assess the influence of gender, academic level, and the presence of painful symptoms on the perception of risk factors at work contributing to musculoskeletal symptoms among dental students of Melaka, Malaysia.

METHODS:

A cross-sectional survey of 183 clinical year dental students based on a convenience sample. The data were collected using the Nordic Musculoskeletal Questionnaire and Job Factor Questionnaire for assessment of musculoskeletal symptoms and risk factors at work respectively. Study data were evaluated using percentage, median, Cochran’s Q test, Bonferroni correction, multiple linear regression analysis and Mann-Whitney U Test. The analysis was interpreted considering a 95 % confidence interval and significant level at P < 0.05.

RESULTS:

Dental students reported a high prevalence (86.9 %) of musculoskeletal symptoms mostly affected the neck, shoulder, lower and upper back body regions. No significant difference in perception was found with the gender. A significant (P < 0.05) higher perception was observed in fourth-year students. The presence of painful symptoms was significantly (P < 0.05) associated with working in the same position, prolonged duration of work and use of tools.

CONCLUSIONS:

Priority in implementing ergonomic education throughout the training in the dental schools should be considered to improve perception and reduce musculoskeletal disorders associated with the dental profession.

Keywords

Dental education ergonomics musculoskeletal discomfort risk factors awareness

1 Introduction

Musculoskeletal disorders (MSD) are injuries or disorders of the muscles, nerves, tendons, joints, cartilage, and spinal discs [1]. Musculoskeletal disorders due to the occupation are called work-related musculoskeletal disorders (WMSD) and are common among dentists than other professionals [2]. This is attributed to the nature and complexity of dental procedures, use of vibrating instruments, perform repetitive tasks, often in static awkward and non-ergonomic position for a long period, and short rest during their practice [3 –6]. A recent systematic review reported the prevalence of non-specific WMSD among dental professionals is estimated to be between 49% and 92% [7]. High prevalence of MSD has consequently reduced their productivity and account for the most common reason for early retirement age in dentists worldwide [8 –10].

Musculoskeletal symptoms can start at early training years in dental schools when ideal ergonomic postures are not followed by dental students in their practice [9 , 11–15]. A study reported that 89% of dental students had poor to medium level of postural awareness, which was reflected in the high prevalence of MSD [16]. A study in the United States, reported body pain in 46% to 71% of dental students, with an increasing percentage by training year in dental school [14], furthermore, a Malaysian study stated that 93% of dental students in clinical training years developed WMSD [15]. During early training years, students may acquire habits that are harmful to their occupational health and continue throughout their practice if preventive and corrective measures are not implemented [17, 18]. Therefore, it is important to evaluate if dental students can recognize the presence of pain or discomfort in their body parts as well as perception about risk factors at work that can contribute to musculoskeletal disorders for self-health awareness. Studies reported the perception of risk factors at work contributing musculoskeletal symptoms among Brazilian and the United States dental students [5 , 19]. However, to the best of our knowledge, no published report is available to evaluate the perception of risk factors at work associated with MSD in multiethnic Malaysian dental students, who are culturally different from previously studied population. Therefore, this study has been undertaken to assess the influence of gender, academic level, and the presence of painful symptoms on the perception of risk factors at work contributing to musculoskeletal symptoms among dental students of Melaka, Malaysia.

2 Materials and methods

2.1 Study design and population

This cross-sectional study protocol was approved by the Institutional Research and Ethics Committee (approval no. MMMC/FOD/AR/B6/E C-2018 (21)), and data were collected using convenient non-probability sampling method, from July to August 2018. Yamane’s formula was used to calculate the study sample size (n = 166) by taking the known source population (eligible subjects, N = 218) of clinical year undergraduate dental students and margin of error (e-0.05) [20]. The study population was undergraduate dental students in clinical training year from the Faculty of Dentistry, Manipal University College Malaysia.

2.2 Inclusion and exclusion criteria

The study included the undergraduate dental students who were in third to fifth year of academic level (clinical training year) during the 2018-19 academic session, agreed to participate voluntarily and sign the informed consent. The students with the congenital musculoskeletal disorder, spinal trauma (congenital/non-work related) and scoliosis, recent history of sports injury as well as incomplete questionnaire were excluded from the study sample.

2.3 Data collection tools

Data collection tools including the personal information sheet, consent form, Nordic Musculoskeletal Questionnaire and Job Factor Questionnaire. All forms used to collect the study data were in the English language as this was the common language for all teaching-learning activities throughout the undergraduate dental course for these participants.

The information related to socio-demographic characteristics (age, gender, ethnicity, academic year), and health of participant were obtained in the personal information sheet.

2.3.1 Nordic musculoskeletal questionnaire

This questionnaire [21] was used to evaluate work-related musculoskeletal disorders, consists of a posterior view of a human figure, subdivided into 9 anatomical regions: neck, shoulders, upper and lower back, elbows, wrists/hands, hips/thighs, knees and ankles/feet, and questions about the presence of musculoskeletal pain in any of these areas, inability to perform normal activities and necessity to consult a health professional. The respondents have to mark with an ‘X’ as affirmative or negative response (yes or no). The part of the questionnaire to identify the presence of pain/discomfort in the previous twelve months preceding the research was considered.

2.3.2 Job factor questionnaire

This tool was originally developed in the United States and used in ergonomic research [22] and later validated and used for collecting the data among dental students [13, 23]. The Cronbach’s alpha coefficient (α)≥0.70 indicating the appropriate reliability for internal consistency of this instrument [5]. Previous studies used this tool to evaluate the perception regarding risk factors at work among dental students [5 , 19] and dental hygienists [24]. Job Factor Questionnaire comprises 15 items that evaluate an individual’s awareness of job environment factors (risk factors at work) and their potential contribution to musculoskeletal disorders. The individuals were asked to indicate on a scale from 0 to 10 (with 0 = not much and 10 = very problematic) depends on how much each variable contributed to the development of pain and lesions related to their current work tasks. The total score obtained from the response of 15 items were calculated for each respondent and categories based on the severity of symptoms in crescent order: the first, from 0–1, indicates the absence of symptoms; the second, from 2–7, indicates minimal to moderate symptoms; and the last, from 8–10, indicates severe symptoms. These responses were further categorized as present (minimal to severe symptoms) and absent (absence of symptoms) for multiple linear regression analysis.

2.4 Data collection procedure

A total of 218 students (third to fifth year) from the Faculty of Dentistry, Manipal University College Malaysia, were invited to participate in the study. Each agreed participant answered two validated, self-administered questionnaires in the English language, distributed at the end of the lecture class. Two of the research team members (unrelated to the participant) were present to briefly explain and clarify any doubts related to study. Students are free to return the completed questionnaire any time within a week. The questionnaires took the students approximately ten minutes to complete. A total of 198 students returned the filled questionnaire, out of them, 15 incomplete questionnaires were removed, thereby 183 included for the analysis after applying the inclusion and exclusion criteria. The response rate for the survey was 90.8 percent.

2.5 Statistical analysis

SPSS version 22.0 (SPSS Inc., Chicago, IL, USA) was used for data analysis. Descriptive statistics such as frequency and percentage were described for categorical data and mean, standard deviation, median (first and third quartiles) were described for quantitative data. Cochran’s Q test was run to determine the difference in the percentage of painful symptoms at different body parts [25]. The sample size was adequate to use the χ²-distribution approximation. Pairwise comparisons were also performed using Dunn’s procedure with a Bonferroni correction for multiple comparisons [25]. Adjusted P-values are presented. Multiple linear regression analysis was used to find out the association between gender, academic year, presence of painful symptoms and perception of risk factors. Model assumptions were checked. Residuals were independent, as assessed by a Durbin-Watson statistics of 2.162. There was linearity and homoscedasticity, as assessed by visual inspection of a plot of studentized residuals versus unstandardized predicted values. There was no evidence of multicollinearity, as assessed by tolerance values greater than 0.1. There were no studentized deleted residuals greater than or less than 3 standard deviations, no leverage values greater than 0.2, and values for Cook’s distance above 1. The assumption of normality was met, as assessed by Q-Q plot [Fig. 1]. Regression coefficient (b) and its 95% confidence interval were also calculated [26]. Mann-Whitney U test was used to analyze for each item of the perception of risk factor instrument between the students with present and absence of painful symptoms [25]. P-value < 0.05 was considered statistically significant.

Fig. 1

Q-Q plot of perception of risk factors.

3 Results

The socio-demographic characteristics are depicted in Table 1. A total of 183 dental students’ data was included for analysis in the study. The mean age of the participant was 23.49 years (SD 1.12), among them 67.8% were female and 32.2% were male. In different clinical training years, the proportion of participants were 32.2%, 33.3% and 34.4% from third, fourth and fifth year respectively. Overall, 86.9 % of the respondents reported musculoskeletal symptoms in the last 12 months. [Table 1]

Table 1
Demographic profile of clinical year dental students (N = 183)

Variable n (%)

Age 23.49 (1.12)^a

Academic level Year-3 59 (32.3)

Year-4 61 (33.3)

Year-5 63 (34.4)

Gender Females 124 (67.8)

Males 59 (32.2)

Ethnicity Malay 97 (53.0)

Chinese 41 (22.4)

Indian 35 (19.1)

Others 10 (5.5)

Musculoskeletal symptoms (last 12 months) Absent 24 (13.1)

Present 159 (86.9)

Perception of risk factors Absent 34 (18.6)

Minimal to moderate 145 (79.2)

Severe 4 (2.2)

Variable		n (%)
	Age	23.49 (1.12)^a
Academic level	Year-3	59 (32.3)
	Year-4	61 (33.3)
	Year-5	63 (34.4)
Gender	Females	124 (67.8)
	Males	59 (32.2)
Ethnicity	Malay	97 (53.0)
	Chinese	41 (22.4)
	Indian	35 (19.1)
	Others	10 (5.5)
Musculoskeletal symptoms (last 12 months)	Absent	24 (13.1)
	Present	159 (86.9)
Perception of risk factors	Absent	34 (18.6)
	Minimal to moderate	145 (79.2)
	Severe	4 (2.2)

^aMean(SD).

The frequency of musculoskeletal pain at different body regions in the previous 12 months among clinical year dental students are presented in Table 2. The higher risk for presence of painful symptoms in different body parts of dental students was neck, shoulder, lower back, upper back, wrist/hand, knee, hips/thigh, ankle/feet and elbow in decreasing order. The percentage of painful symptoms was significantly different in the different body parts, χ²(8) = 438.808, P < 0.001 (Table 2). Pairwise comparisons of different body regions showing the significant difference of musculoskeletal pain in the previous 12 months are presented in Table 3.

Table 2

Musculoskeletal pain at different body regions in previous 12 months (N = 183)

Body regions	Painful symptoms present n (%)	χ²(df)	P-value^b
Neck	129 (70.5)	438.808 (8)	<0.001
Shoulder	116 (63.4)
Lower back	102 (55.7)
Upper back	84 (45.9)
Wrist/hand	52 (28.4)
Knees	28 (15.3)
Hips/Thigh	25 (13.7)
Ankle/feet	24 (13.1)
Elbows	6 (3.3)

^bCochran’s Q test.

Table 3

Pairwise comparisons of musculoskeletal pain at different body regions in previous 12 months (N = 183)

Body part	Painful symptoms present n (%)	Difference^c
Neck	129 (70.5)	Shoulder (P = 0.999)
		Upper back (P < 0.001)
		Elbows (P < 0.001)
		Wrist/hand (P < 0.001)
		Lower back (P = 0.071)
		Hips/Thigh (P < 0.001)
		Knees (P < 0.001)
		Ankle/feet (P < 0.001)
Shoulder	116 (63.4)	Upper back (P = 0.009)
		Elbows (P < 0.001)
		Wrist/hand (P < 0.001)
		Lower back (P = 0.999)
		Hips/thigh (P < 0.001)
		Knees (P < 0.001)
		Ankle/feet (P < 0.001)
Lower back	102 (55.7)	Upper back (P = 0.999)
		Elbows (P < 0.001)
		Wrist/hand (P < 0.001)
		Hips/thigh (P < 0.001)
		Knees (P < 0.001)
		Ankle/feet (P < 0.001)
Upper back	84 (45.9)	Elbows (P < 0.001)
		Wrist/hand (P = 0.009)
		Hips/thigh (P < 0.001)
		Knees (P < 0.001)
		Ankle/feet (P < 0.001)
Wrist/hand	52 (28.4)	Elbows (P < 0.001)
		Hips/thigh (P = 0.071)
		Knees (P = 0.213)
		Ankle/feet (P = 0.048)
Knees	28 (15.3)	Elbows (P = 0.419)
		Hips/thigh (P = 0.999)
		Ankle/feet (P = 0.999)
Hips/thigh	25 (13.7)	Elbows (P = 0.999)
		Ankle/feet (P = 0.999)
Ankle/feet	24 (13.1)	Elbows (P = 0.999)
Elbows	6 (3.3)	–

^cBonferroni correction, significant at the 0.05 level.

The multiple linear regression model was statistically significant, F(4,178) = 2.194, P = 0.010. R² for the overall model was 4.7% with an adjusted R² of 2.6%, the effect size was small. Regression coefficients and standard errors are showing in Table 4. There was no significant association between gender (b = 0.29; 95% CI –0.35 to 0.93, P = 0.373), painful symptoms (b = 0.57; 95% CI –0.31 to 1.46, P = 0.201) and perception of risk factors [Table 4]. Regarding the academic level, fourth-year students had significantly (P = 0.025) higher perception, however, it was not significant (P = 0.186) in fifth-year students in reference to third-year students [Table 4].

Table 4

Multiple linear regression analysis for the association between gender, academic year, musculoskeletal pain and perception of risk factors

Variable	Perception of risk factors
	Regression coefficient		Standard coefficients (β)	P-value
	b (95% CI)	SE
Gender
Male	Reference
Female	0.29 (–0.35, 0.93)	0.325	0.068	0.373
Academic Year
Year 3	Reference
Year 4	0.85 (0.11, 1.59)	0.376	0.201	0.025
Year 5	0.48 (–0.23, 1.19)	0.360	0.114	0.186
Painful symptoms
Absent	Reference
Present	0.57 (–0.31, 1.46)	0.447	0.097	0.201

b: regression coefficient; SE: standard error; 95% CI: 95% confidence interval.

Analysis of each item for the perception of risk factors, showing a significant difference regarding work in the same position for long periods (P < 0.001), work duration (P = 0.030) and use tools (P = 0.025) between the students with presence and absence of painful symptoms [Table 5].

Table 5

Perception of risk factors (Job Factor Questionnaire) analysis that can contribute to musculoskeletal pain

Items	Painful symptoms		P-value^d
	Present median (Q1, Q3)	Absent median (Q1, Q3)
1. Perform the same task repeatedly	4.0 (1.0, 6.0)	3.0 (0.0, 5.0)	0.082
2. Work quickly for short periods (get up, hold, pull, etc.)	2.0 (0.0, 5.0)	4.0 (0.0, 5.0)	0.818
3. Have to handle or hold small objects	2.0 (0.0, 5.0)	1.5 (0.0, 4.0)	0.441
4. Insufficient intervals or pauses during the workday	4.0 (1.0, 6.0)	3.0 (0.25, 5.75)	0.102
5. Work in uncomfortable positions	5.0 (2.0, 7.0)	2.5 (0.0, 6.5)	0.057
6. Work in the same position for long periods (standing, inclined, seated, kneeling, etc.)	6.0 (4.0, 8.0)	3.5 (0.0, 6.0)	<0.001
7. Bend or twist my back in an uncomfortable manner	5.0 (3.0, 8.0)	4.5 (0.5, 8.0)	0.306
8. Work close to or at my physical limit	4.0 (2.0, 6.0)	3.0 (0.0, 7.0)	0.549
9. Reach at a level above my head or away from my body	4.0 (1.0, 6.0)	2.0 (0.25, 6.0)	0.451
10. Work in a hot, cold, humid, or damp environment	2.0 (1.0, 5.0)	3.0 (1.0, 5.0)	0.922
11. Continue working when I have some pain or some lesion	4.0 (2.0, 7.0)	3.5 (0.25, 6.75)	0.269
12. Carry, lift, or move heavy materials or items of equipment	3.0 (1.0, 6.0)	3.0 (0.0, 5.5)	0.351
13. Work duration (duration of work, overtime)	4.0 (2.0, 7.0)	2.0 (0.0, 5.0)	0.030
14. Use tools (shape, weight, vibrations etc.)	2.0 (1.0, 5.0)	1.0 (0.0, 3.75)	0.025
15. Work without receiving training	4.0 (1.0, 6.0)	3.0 (0.0, 5.0)	0.476

^dMann-Whitney U Test.

4 Discussion

The present study aimed to access the influence of gender, academic year, and the presence of painful symptoms on the perception of risk factors at work contributing to musculoskeletal symptoms among dental students of Melaka, Malaysia. Dental professionals have been reported to be constantly exposed to work-related musculoskeletal disorders with symptoms often started as early as the student phase [11 –15]. Our study found, a high prevalence of musculoskeletal symptoms among dental students in the previous twelve months, commonly in the neck, shoulder, upper back and lower back body region consistent with several studies [7 , 27–30]. The common posture assumes at work by the dental personnel with the neck bent and twisted, arms abducted, repetitive and precise movements of the hands, static position without break is the frequently reported cause of the neck syndrome and pain within the shoulder and upper extremity [12 , 31]. These unusual static postures adopted by dentists required 50% of muscles contraction to keep the body motionless and eventually lead to the accumulation of lactic acid, compresses the blood vessels, reducing oxygen levels, causing fatigue and pain [12, 32]. Degenerative changes in the lumbar spine due to inadequate lumber support for the long working period or non-ergonomic operator stool and high pressure exerted on the intervertebral disc as well as prolonged spinal hypo-mobility can lead to subsequent lower back pain [5, 33].

The results of the current study demonstrated that the dental students’ perception of risk factors were not affected by gender which was in agreement with the previous report [5], indicating similar awareness towards the risk factors at work related to MSD among the gender. This might be because both the gender acquires knowledge and training to perform clinical procedures in the same work environment as all study participant recruited from the same institute. Although, other studies have reported women having higher perception and painful symptoms [10 , 34]. Hoffman et al. stated that the higher perception reported by the female gender might be due to their tendency to express their feelings easily or lower threshold for detecting pain or symptoms as well as the biological difference (body size, muscular capacity and hormonal difference) or psychological differences (coping strategies) may have an effect on gender disparity for a similar exposure to the same risk factors [35, 36].

Regarding the academic level, perception of risk factors was significant for fourth-year students but not significant for fifth-year students in reference to third-year students. This might be explained that in the third-year students are beginning to perform the dental procedure on real patients, they acquire knowledge and follow the instructions given for work posture, to hold the instrument properly under the continuous observation by the clinical faculty. This was also continued to a certain extent when students were promoted to the fourth year with a variety of new clinical exposure, paying more attention to risk factors. However, over time students engage more with clinical activities, longer clinical hours to complete the clinical requirements, focusing on providing outstanding treatment to their patients, ignoring the adequate attention of risk factors present in the work environment might be the cause of insignificant perception among fifth-year students in reference to the third-year students. These explanation were in agreement to a study by Bota et al, who stated that over the years in a higher academic level, students focusing on providing clinical treatment to their patients, instead of giving appropriate attention to the risk factors present in their work environment [5]. Whereas Garcia et al reported lower perception in first-year dental students and explained based on different workload characteristics and clinical experience [13]. However, these studies include both preclinical and clinical year dental students compared to only clinical year students in the present study [5, 13].

In the present study, 79.2 % of students reported minimal to moderate perception of risk factors and overall have not been associated with the presence of painful symptoms, which is consistent with results of Bota et al among United States’ dental students [5], indicating the inadequate ergonomic knowledge contributing the finding in the sampled population. In contrast, studies have reported higher perception scores with the presence of painful symptoms in Brazilian dental students highlighting the importance of improving awareness for work-related risk factors [13, 19]. Furthermore, analyzing each component of perception of risk factor instrument, a significant difference in students’ perception with the presence of painful symptoms for working in the same position for a long period, prolonged duration of work (overtime) and use tools (shape, weight, vibrations etc.) was found. While working on patients in clinics, students commonly use the vibrating dental tool (scaler, high-speed motor etc.) for a variety of procedures, take the same position for a longer period along with repeated tasks in limited space to complete the procedure.

Although, the cross-sectional design of this study has certain limitations, such as a non-probabilistic sample and its limited external validity due to the inclusion of dental students from one Malaysian institute. However, the results of this study should be used to review and implementation of regular ergonomic education to enhance students^′ knowledge of risk factors at work as well as workshops to practice ergonomic skills in daily work and tasks in the dental school curriculum throughout the training of undergraduate students.

5 Conclusions

Dental students working in clinics are at high risk of developing musculoskeletal symptoms. The neck, shoulders, upper and lower back are the most affected sites with musculoskeletal symptoms. The perception of risk factors was significantly associated only with fourth-year dental students. Working in the same position for a long period, prolonged duration of work and use of vibrating tools were the significant perceived risk factors. Priority in implementing ergonomic education throughout the training in the dental schools should be considered to improve perception and minimizing the musculoskeletal disorder associated with the dental profession.

Footnotes

Acknowledgments

The authors thank Prof. Dr. Abdul Rashid Hj Ismail, Dean Faculty of Dentistry, Manipal University College Malaysia, for constant support and encouragement throughout the conduct of this study. The authors are also grateful for the valuable comments and suggestions of the esteemed reviewers, which enhanced the strength and significance of the paper.

Conflict of interest

The authors declare that there is no conflict of interest regarding the publication of this article.

Funding

No external financial support was obtained to conduct this study.

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