Risk factors for work-related musculoskeletal disorders of dentists in Kuwait and the impact on health and economic status

2.1 Nature of dentists’ work practices and postures

Marshal et al. [14] suggested that occupations requiring maintenance of static posture for prolonged intervals were most at risk for WMSD. Risk would be even greater when occupational activities required unnatural anatomic alignment. Work practices of dentists mandate high level skills including intense concentration and attention to detail, visual and depth perception, and fine and gross motor control [15] keen accuracy [6] in prolonged static postures [6, 16]. Valachi and Valachi [17, 18] described the unbalanced forward positioning of the head and neck that dentists must maintain while performing dental procedures. This awkward positioning places the spinal column in improper alignment inadequate for head support, which causes upper thoracic and cervical muscles to contract continuously to maintain head position. Over time, muscles adjust to inappropriate postures, thereby leading to structural changes and chronic musculoskeletal damage. This results in locoregional pain, headaches and fatigue.

2.2 Prevalence of WRMDs among dentists

A systematic review of 23 articles from 8 different countries reporting on musculoskeletal pain in dentists estimated a prevalence of 64–93% [3]. The back and neck were the anatomic areas most commonly affected. Leggat and Smith [19] surveyed dentists in the Queensland Branch of the Australian Dental Association and found that 87% of respondents reported having at least one WMSD symptom in previous 12 months, most often affecting the neck, shoulders, or low back. Similar prevalence of WMSD in dentists from Thailand, Serbia, Turkey, Australia, India and Iran have been reported [6, 20–23]. Headache was also reported as a common symptom as well [14, 23]. Leggat et al. [7] also performed an extensive literature review examining occupational health problems and WMSDs. They concluded that, despite technical advances in recent years, WMSD remains a major occupational health problem in modern dentistry.

2.3 Causes of WMSD among dentists

Performance of dental procedures requires prolonged maintenance of posture, resulting in prolonged contraction of multiple core stabilizer muscles [5, 18]. Most muscular stress is incurred during trunk flexion, which causes strain and overexertion of the lower back musculature. WMSD in dentists and similar occupations primarily results from the cumulative effects of prolonged work practices and repetitive motor activities performed while maintaining a static posture [3, 21]. Moreover, Valachi and Valachi [18] pointed out that WMSD developed in dentists whether they preferred working while standing or sitting- the only observed difference was the anatomic site affected by WMSD.

In reviewing studies of potential causative factors of WMSD in dental operators, Valachi and Valachi [18] found that causes of musculoskeletal pain are multifactorial and include prolonged static posture, imbalanced posture, hypomobile joints, and one-sided weight bearing. Valachi and Valachi [18] also found that weak postural muscles of the trunk and shoulder may lead to poor operator posture. In addition, they describe a relationship between prolonged, static muscle contractions and muscle ischemia and myonecrosis [18]. Ayatollahi et al. [12] reported that dentists tend to work in strained postures that promote musculoskeletal malalignment, Lindfors et al. [24] related strenuous work posture, meticulous motor activity, and muscle fatigue to musculoskeletal disorders of the upper extremities in dentists and Tirgar et al. [6] concluded that fatigue in the deep cervical flexor muscles associated with MSD in the cervical region.

2.4 After-effect of WRMDs

Hayes et al. [3] recognized that WMSD in dentistry contributes considerably to increased use of sick leave and reduced clinical productivity; it even forces some practitioners to leave the profession. Also, Leggat and Smith [19] found that nearly 10% of dentists reported taking leave from work due to WMSD. Those who took sick leave for WMSD reported that their daily activities were also restricted because of WMSDs primarily affecting the back, neck, or shoulder [19]. Almost 40% of dentists seek medical attention because of the severity of WMSD [19, 25]. Muralidharan et al. [21] described the impact of WMSD in dentists in terms of increased absenteeism or sick leaves, reduced clinical productivity, and the need for medical consultation and alteration of clinical duties.

2.5 WRMDs among dentists in Kuwait

In Kuwait, dentistry is a fast growing profession in the government and the private sectors. However, we were unable to find previous reports on the prevalence of WMSD and associated risk factors. In Kuwait, primary prevention is rarely implemented and, secondary prevention, in which change occurs after concerns are raised, is mainly utilized. We seek to bring awareness and knowledge about an alarming health issue among dentists in Kuwait and to help prompting prevention measures. Therefore, the aim of this study was to determine the prevalence of WMSD among Kuwait dentists, its associated risk factors, and to define the relationship between WMSD and dentist absenteeism and workplace productivity. We believed that the prevalence would be high because the dental occupation necessitates performance of recurring and repetitive physical tasks on a daily basis.

3.1 Participants

The questionnaire was distributed to 232 dentists working in government, private, or academic clinics. A convenient sampling method was used to identify participants. Inclusion criteria included dentists with at least one year of clinical experience and at least one month of continuous practice before data collection. Exclusion criteria included having prior musculoskeletal surgery. Auxiliary dental professionals (dental assistants, dental hygienists, dental technicians, or dental therapists) were also excluded.

3.2 Instrument

The questionnaire used was originally designed by Holder et al. [26] and later adapted by Alnaser [27], and is a self-reported survey with closed-ended questions. The original questionnaire established face and content validity and an average of 98% test-retest reliability. Additional modifications were made to the questionnaire to fit the population in this study. The original questionnaire was designed to examine musculoskeletal disorders in physical therapists. Modification made to replace the word “physical therapists” with “dentists” and to add areas of practice relating to dentistry. The questionnaire included two sections: Section I included 13 demographical items such as age, sex, area of practice, weight, height, hours in patient contact, and years of experience. Section II was self-reporting of any WMSD experienced during the past 12 months and the duration of sustained WMSD was not specified. It included 13 items such as types of injuries, affected anatomical areas, activities that provoked or exacerbated symptoms of WMSD, and dentist responses to injuries.

3.3 Procedure

The study had been conducted in full accordance with the World Medical association Declaration of Helsinki. Approvals from the Faculty of Allied Health Sciences Institutional Review Board at Kuwait University and Ministry of Health of Kuwait were obtained. Using a convenient sampling method, the questionnaires and consent forms were distributed in person to dentists in governmental, private, and academic dental clinics. Informed consent was obtained from all individual participants before handing the questionnaire. Some questionnaires were collected at the time of distribution and others were collected one week later in person.

3.4 Study design

A cross-sectional design was used for this study. All variables relating to WMSD were self-reported. The main variables of examination included symptoms of WMSD, anatomic region injured, performance of tasks and activities related to WMSD, and responses taken after an incurring an injury. Variables were measured on a nominal scale. Demographic data included both discrete and continuous variables.

3.5 Data analysis

The Statistical Package for the Social Sciences (SPSS) version 23 was used for analysis. Descriptive statistics were used to summarize the demographics and frequencies of WMSD among respondents. An independent sample Student’s t test was conducted to compare years of experience, age, and working hours between dentists with or without WMSD. The χ² test was conducted to determine the association between independent factors and occurrence of WMSD. Alpha was set at P≤0.05. Prevalence was calculated using the following formula: Prevalence = ( Number of dentists with injuries ÷ Number of dentists responding ) × 100 %

4.1 Participants

A total of 186 dentists (80% response rate) completed the questionnaire and qualified for analysis. Age ranged from 23 to 67 years with a mean of 34.3±9.9 years. Of the respondents, 106 (57%) were male and 78 (42%) were female (there were two missing responses for sex). Respondents mainly worked in government clinics (75%), with 19% in private clinics and 5% in academic clinics. Most reported being in general practice (48%), with fewer in endodontics (11%), dental public health (10%), pediatrics (6%), orthodontics and dentofacial (5.5%), prosthodontics (5.5%), or other subspecialties (16%). The number of years in practice among respondents ranged from 1 to 45 years with a mean of 9.7±9.5 years. Working hours ranged from 3 to 72 hours per week with a mean of 32.4±11.3 hours and the number of patients seen per day ranged from 2 to 28 with a mean of 10.7±5.7.

4.2 Prevalence of WMSD

Over the preceding 12-month period, 89 (48%) of responding dentists reported experiencing a WMSD. The dentists with injuries were asked to report all possible anatomic sites affected, and each was allowed to report one or more area with injury. They identified 8 different body sites in a total of 177 times. They reported the highest level of WMSD in the neck (27.7%, 49/177 reported), and they reported the lower back (27.1%, 48/177 reported) and the shoulder (22%, 39/177 reported) as their second and third most prevalent site of injury (Table 1). Also, the dentists with injuries identified 10 WMSDs and reported one or more type of injury 107 times. They reported muscle spasm (30.85%, 33 reported) as the most common injury, and followed by muscle strain (29.90%, 32 reported) and vertebral disk involvement (12.15%, 13 reported) (Table 1). Injuries were reported most commonly for general practice (50%), endodontics (22%), pediatric dentistry (8%), and dental public health, oral and maxillofacial, and prosthodontics (each 5%).

Dentists reporting injuries tended to be older (36.4±10.3 years vs. 32.6±9.3 years; P = 0.01) and in practice longer than dentists without injury (11.7±10.4 years vs. 8.2±8.4 years; P = 0.013). Although there was no difference in the number of patients treated per day, dentists reporting injuries worked more hours than those not reporting injury (34.9±10.6 hours vs. 30.4±11.5 hours; P = 0.08).

Dentists with injuries identified root canal treatment (35%), teeth extraction (26%), crown preparation (17%), and drilling and filling (12%) to be most strenuous activities. Also, they identified maintenance of a particular posture for a prolonged period of time and bending or twisting as the most common specific antecedent factors (Table 2). Over half of dentists reporting WMSD (55%) testified that continued clinical practice exacerbated their symptoms. Specific postures or motions that aggravated their symptoms included maintaining a position for a prolonged period of time (30%), bending and twisting (21%), working in an awkward position (13%), performing repetitive tasks (11%), and working when physically fatigued (10%).

Dentists with injuries rated their pain when experienced WMSD. On the pain scale (0–10), they reported a mean score of 4.8±2.2. However, only 23% (20 participants) of dentists with WMSD report lost days from work due to their injuries. Lost work days counted for 163 hours that spent away from work. A significant association was found between rating of pain and lost days (x² (10, n = 85) = 20.96, ρ = 0.021). Moreover, Most dentists reporting a WMSD in this survey did not report their injury (78%; 69 participants) to the appropriate occupational health personnel. Instead, they stated that they were “too busy to report” (36%), “becoming accustomed to injury” (30%), or reluctant to report the injury “to avoid being perceived as incompetent” (8%). Also, 59% of dentists with injuries attempted to self-treat at some point and 50% sought medical consultation.

4.5 Adaptation/coping with WMSDs

The results showed that 56% of dentists with injuries applied some adaptive or coping strategies to mitigate symptoms or avoid future recurrences. Such strategies included changing working positions frequently and taking more rest breaks or pauses (Table 3). Also, they indicated limiting patient contact time (14%), limiting their area of practice (13%), or considering changing jobs (7%) because of WMSD.

5.1 Postures and movements as risk factors

Neck, lower back, and shoulder regions were the most commonly injured anatomic sites in this study as well as several prior studies from different countries [3, 39]. This is likely directly related to dentist posture during procedures, in which neck and lower back flexion is prolonged. This is illustrated in Table 2 as dentists identified maintaining positions for prolonged periods as a common causative factor for their injuries. Similar findings were reported by other investigators [13, 39]. Other commonly affected anatomic sites included the wrist and hand [10, 39].

In this study, dentists with injuries identified some types of WMSDs not reported in prior studies. Muscle spasm, muscle strain, vertebral disk involvement, ligament sprain, and tendinitis were the most common types of WMSD in this study population. These disorders clearly point to awkward and prolonged posture, excessive repetitive motor activity, and high physical stresses and loads as occupational characteristics that place dentists at risk of WMSD. Again, we note that WMSD in dentists could not be related to industrialization and could not be limited to underdeveloped environments.

5.2 Personal and working characteristics as risk factors

Two previous studies found that more years of practice and advanced age were associated with WMSD [11, 37]. Conversely, other investigators have reported that dentists with fewer years of experience were more likely to develop WMSD [19, 38]. In this study, WMSD were reported more often by older dentists with many years of clinical practice and longer working hours. These three factors may suggest that WMSD in dentists are related to the cumulative effects of physical loads and vibration, maintenance of unnatural postures for prolonged intervals, and excessive repetitive movements and activities for several hours a day over many years. Similarly, Sakzewski and Naser-ud-Din [33], Aminian et al. [35], and Rafie et al. [36] independently concluded that high levels of physical work-related stress over several years was the main predictor of WMSD in dentists. In addition, dentists with injuries reported that continuing clinical practice, including maintenance of awkward postures and performance of repetitive tasks, exacerbated the symptoms of WMSD. They also report that root canal treatment, teeth extraction, crown preparation, and drilling and filling worsened their symptoms. This could be an indication that dentists with WMSD continued their clinical practice despite pain and discomfort. Continuing clinical practice with an injury may be indicative of denial of the injury or be motivated by avoidance of being perceived as incompetent or uncaring—particularly for foreign dentists with contracts or those under observation. Regardless, continuing clinical practice for whatever reason does not allow affected joints and muscle groups to rest and recuperate.

5.3 Culture and behaviors toward WMSDs

Despite experiencing moderate to severe levels of pain due to WMSD, the majority of dentists did not report their injuries to appropriate occupational health personnel. They often indicated that they were too busy to report their injuries, which could reflect the high level of their work demands. Another common reason was being accustomed to the injury, which may reflect an occupational culture among dentists to accept injuries as an expected occupational hazard. The “culture of selflessness” makes it difficult for dentists to admit suffering from work-related injury. Approximately half of dentists with WMSD sought medical attention in this and other previous studies [19, 25]. This behavior may indicate that dentists, as healthcare providers often do, perceive that seeking medical treatment is unfitting or embarrassing.

More than half of dentists reporting WMSD recognized their injuries and attempted various coping strategies to reduce pain and discomfort and to prevent future episodes. They seemed to recognize the effect of static and prolonged postures by changing work positions frequently and using improved body mechanics. Also, they seemed to be more conscious about preventative measures by taking more rest breaks, stopping work when feeling hurt, requesting assistance from other personnel, and increasing use of mechanical aids.

5.4 Effects of WMSDs on the individual and work practices

Nermin [5] explains that WMSD is a costly health problem to the individual, his/her family and the workplace. WMSD leads medical cost including medical and rehabilitation expenses and economical cost such as lost production, stopped wages, and finding and training replacement. Because of WMSD, approximately 25% of respondents lost days from work that significantly associated with a higher rating of pain. A previous study reported that 12% of dentists with pain took sick leave [30]. Often these leaves are quite extended. Muralidharan et al. [21] and Leggat and Smith [19] have both reported that sick leaves average around 2 weeks duration. Absenteeism, suboptimal efficiency, and lack of concentration during task performance due to injury all effect clinical productivity and quality of patient care [21]. As reported by the Bureau of Labor Statistics, millions of dollars are lost because of absenteeism caused by work-related injuries. Moreover, patient satisfaction and trust may suffer because of chronic absenteeism and delayed dental appointments.

The Bureau of Labor Statistics reported that injured workers older than 45 years of age tended to take more days away from work than younger workers, and injured workers older than 55 years of age had the highest incident rate [2]. In this study, older dentists experienced more WMSDs, which may in turn explain why they also were absent from work longer. Similar finding was also observed among dentists in India, Lithuania, and Poland [21, 41]. This could impose a high financial cost to dental clinics that rely on dentists to treat patients. Additional financial costs may also be incurred, such as supplying replacement staff, making overtime payments, loss of clinic productivity, and possibly paying compensation on injury claims.

Alnaser [4] explains that WMSD can have psychosocial consequences including fear, anger, and isolation, and limited performance of personal and family roles and restricted participation in social and leisure activities, in addition, Leggat et al. [42] found high prevalence of stress among dentists. Radanović et al. [23], Muralidharan et al. [21], Feng et. al. [34], and Taib et al. [43] showed that WMSD lead to a reduction in engaging in normal activity of daily living and leisure activity, as well as increased physician consultations, hospitalizations, and sick leaves. Muralidharan et al. [21] and Leggat and Smith [19] believe that WMSD do not solely affect the physical well-being of the dental practitioner but can affect psychological and social well-being as well. Muralidharan et al. [21] suggest that these non-physical effects may contribute to a decreased quality of life. This may explain why some dentists with WMSD in this study have since limited the number of patients they treat or fields in which they practice; some have even considered quitting dentistry. Likewise, Rafie et al. [36] and Pourabbas et al. [44] also found dentists with WMSD tend to reduce their work hours, utilize sick leave, or leave their practices.

In conclusion, dentists in Kuwait and other countries face a major problem with respect to WMSD. This occupational hazard is common in industrialized, industrially developing, and underdeveloped countries. The main cause of WMSD could be the difficult nature of dental practice requiring long hours of precise, meticulous, repetitive tasks and motor activities that subject the body to unnatural and awkward anatomic postures which impose increased force and load bearing on stressed muscles and joints of the neck, shoulders, low back, wrists, and hands. Moreover, WMSDs, in particular with a higher level of pain symptom, could result in increased absenteeism, reduced clinical productivity, and in turn, higher economical costs. Finally, dentistry education programs should include courses in ergonomics and biomechanics. Dentists should also consider participating in continuing education programs in ergonomics. New ergonomically designed dental instruments that allow for more natural body positioning are needed as well.