Ergonomic risk and preventive measures of musculoskeletal disorders in the dentistry environment: an umbrella review

Introduction

It is well known that dental practitioners are predisposed to a number of different occupational perils during the course of their professional work (Leggat, Kedjarune & Smith, 2007; Ayatollahi, Ayatollahi & Ardekani, 2012; Gopinadh et al., 2013).

These risks can be classified as: physical, chemical, biological, ergonomic and work-related stress.

Physical threats are due to the use of vibrating tools (Mehta, Gupta & Upadhyaya, 2013), vibration (Rytkönen et al., 2006), non-ionizing (UV) and ionizing (X-rays) radiation.

The chemical risks are the exposure to inorganic agents such as mercury, organic agents such as solvents, resins and anaesthetic gases; caustic agents (formaldehyde and hydrogen peroxide) and allergens (latex) which are also handled (Mehta, Gupta & Upadhyaya, 2013).

The biological hazards may be caused by airborne microorganisms as well as via body-fluid transmission; the most common pathogens are bacteria, viruses (HIV, HBV, HCV) and fungi (Bravo, Correnti & Escalona, 2006; Yonai, 2010).

The work-related stress is due to excessive workloads and can lead to psychological disorders, such as tension, depression, emotional exhaustion and demotivation, all with medico-legal consequences (Ayatollahi, Ayatollahi & Ardekani, 2012).

The ergonomic hazards caused by strained posture and prolonged repetitive movements can induce musculoskeletal disorders (MSDs) (Custodio, Silva & Brandão, 2012; Khalekar et al., 2016).

The most recent study, published in 2005 by Sartorio et al. (2005) reported that these disorders occur in 54–93% of dentists, with a higher incidence in older individuals and women. The areas of the body mainly affected by repetitive strain are the shoulders and wrists, which often display symptoms of carpal tunnel syndrome (Abichandani, Shaikh & Nadiger, 2013; Jodalli et al., 2015).

The most frequently reported disorders among dental practitioners involve the spine, shoulders and hand-wrist tract which can result in lower back pain, neck pain, cervical brachial pain, shoulder tendinitis, De Quervain syndrome, carpal tunnel syndrome and Guyon syndrome (Morse, Bruneau & Dussetschleger, 2010; Biswas et al., 2012; Gupta, Ankola & Hebbal, 2013; Gupta et al., 2014; Tirgar et al., 2015).

Some studies show that MSDs develop over time as a result of incorrect posture at work, and that being aware of these disorders and preventive practices early in professional life can minimize the risk of onset of MSDs. Being vigilant from the early working years can have a lasting impact on the practitioner’s future professional life (Sakzewski & Naser-ud-Din, 2014).

Incorrect posture will lead to MSDs which result in a reduction in productivity and a potential loss of earnings for the dental practice; it is therefore essential that appropriate ergonomic office furniture and equipment should be installed together with appropriate lighting and magnifying instruments that improve visibility (Valachi, 2009; Dable et al., 2014).

The aim of this study was to perform a systematic review of international literature and analysis of specific ergonomic risk factors and preventive measures of MSDs in professional dental activity.

Materials and Methods

The presentation of this systematic review is in accordance with the PRISMA statement (Moher et al., 2009).

Results

Online research indicated 4188 references: Pubmed (2919), Scopus (1257) and Cochrane Library (12). Of these, 3012 were excluded because they were unrelated to dentistry and occupational hazards of dental practitioners. Of the remaining 1176, 187 items were excluded due to duplication.

The full text of 989 studies were assessed, 960 papers that did not meet inclusion criteria were excluded.

Ultimately, 29 studies were included in this review (Fig. 1). They were 16 narrative reviews and 13 original articles. Among the original articles, 10 were cross-sectional studies, two were clinical trials and one was a case study (Table 1).

Discussion

The rationale for conducting this review was twofold: firstly, the most recent study regarding this matter was published in 2005; secondly, the aim was to conduct a more comprehensive review utilizing innovative methodological tools developed since the last review.

Our review showed that certain risk factors present in the dentistry field deserve proper consideration, particularly for the prevention of MSDs.

Prolonged static posture is considered one of the main causes of MSDs and should be the focus of risk assessment by occupational physicians to facilitate the development of effective preventive strategies (Peros et al., 2011; Roberts, Gallardo & Brown, 2014).

The most frequently observed incorrect postures (Kanteswari et al., 2011) in dental practitioners are:

• Extreme forward head tilt and overstretched neck;

• trunk inclination and rotation towards one side;

• the raising of one or both shoulders;

• increased curvature of the thoracic vertebral column;

• incorrect positioning of the lower limbs with thigh-leg angle of less than 90°.

The forward-head tilt and rounded-shoulder postures increase loads on the upper neck muscles (upper trapezius and levator scapulae) and spinal vertebral discs (Haddad et al., 2012).

Frequent trunk inclining and twisting to one side, is very often caused by incorrect positioning of the workstation, tools and materials. When dental equipment is not at an appropriate working height, distance and position, the dental professional is forced to sustain an unbalanced position (Gupta, 2011). By receiving/handing tools to the dentist, dental assistants can play an important role in reducing repetitive movements and poor posture that can cause MSDs (Finkbeiner & Muscari, 2011; Gosavi, Gosavi & Jawade, 2012).

According to Custodio, due to limited workspaces, the positions recommended by ISO and FDI for both the patient and the professional (respectively supine and at 9 o’clock) are rarely respected (Custodio, Silva & Brandão, 2012).

Furthermore, some authors indicate the importance of both the position of the patient’s chair which should be a elevated in accordance to the dental worker’s height, and the use of a suitable lighting source (Gosavi, Gosavi & Jawade, 2012).

If the dental professional’s seat does not permit a 90°  angle with the knees and does not provide proper lumbar support, the spinal curvature is reduced leading to posterior rotation of the lower limbs. For this reason a workstation with appropriate ergonomic supports is fundamental (Pirvu et al., 2014; Porter, 0000).

Recently, some studies have highlighted risk factors such as obesity and physical inactivity in the development of chronic MSDs in medical practitioners; often due to exhaustion and fatigue caused by a heavy workload and long working hours (Harutunian et al., 2011; Thakar et al., 2015).

The published literature documents the important role played by physical activity, aerobics and stretching as preventive ergonomic measures. Aerobic exercises, as the name suggests, improves the oxygen flow to the tissues, thus increasing efficiency. Stretching exercises are effective in relaxing and reducing muscle tension caused by incorrect posture (Kumar et al., 2014). It is well known that a prolonged static posture needs contraction of 50% of the total body muscles, and this requires stretching the tensed muscles. In order to reduce the tension in the muscles, it is recommended, as suggested some authors (Kendall, McCreary & Provance, 1993; Milerad et al., 1991) a slow, gentle and pain free stretch maintained for 15–30 s, performed 2–3 times a day.

Maintaining a neutral, balanced posture or alternating between different positions during examinations was a major factor in preventing MSDs in dentists which emerged during this literary review (Todd, Bennett & Christie, 2007; Anghel et al., 2007; Gosavi, Gosavi & Jawade, 2012). These results are consistent with a study that shows how dentists working exclusively in a sitting position are more likely to be affected by lumbar pain than those who alternate between sitting and standing (Pirvu et al., 2014).

The correct working posture in dental practice is neutral and symmetrical; the clinician is seated with the pelvis and shoulders parallel, the legs are slightly apart, the trunk perpendicular to the floor, the arms are close to the body, the forearms are horizontal and the head is flexed by 20–25°  (Anghel et al., 2007).

All work related risks and their respective preventive strategies should be explained at the undergraduate training stages, so that students can prevent the onset of MSDs by adopting an ergonomic approach in their dental practice (Garcia, Presoto & Campos, 2013).

The limits of this review are linked to the mediocre methodological quality score and an inadequate statistical analysis of included studies, which were mainly conducted in Asian countries (55%). In addition, the limited number of clinical trials published greatly reduced the evidence base of the results. Therefore, to be able to fully assess risks and preventive factors associated with the MSDs in dentists, further randomized clinical trials are imperative.

In conclusion, to prevent MSDs a targeted healthcare protocol is required following the advice of physiatrists so that the occupational physician, including professional figures such as dentists could benefit. The goal of the protocol should be to prevent the incidence of posture related disorders by indicating clinical and instrumental tests aimed at establishing if workers are exposed to specific risk factors. Furthermore, the protocol should indicate preventive strategies such as the correct posture for dental practitioners and exercises that improve aerobic and physical activity.

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