|Year : 2015 | Volume
| Issue : 1 | Page : 138-144
Dental ergonomics: Basic steps to enhance work efficiency
Abdul Rahim Shaik
Department of Physical Therapy and Health Rehabilitation, College of Applied Medical Sciences, Majmaah University, Al Majmaah, Riyadh, Kingdom of Saudi Arabia
|Date of Web Publication||13-Apr-2015|
Dr. Abdul Rahim Shaik
Assistant Professor, Department of Physical Therapy and Health Rehabilitation, College of Applied Medical Sciences, Majmaah University, Al Majmaah, Riyadh
Kingdom of Saudi Arabia
Source of Support: None, Conflict of Interest: None
The nature of the dental profession and the postures assumed by the dental surgeons during their professional work has a huge impact on the dental surgeon's body and carries with it a high risk of musculoskeletal disorders (MSDs). To perform efficiently and effectively, they shall always like to attain a position that allows them to achieve optimum access, visibility, comfort, and control at all times. Good ergonomic design of the workplace is a basic requirement for facilitating the balanced musculoskeletal health that will enable longer, healthier career, enhance productivity, and minimize MSDs among dental surgeons. While treating the patients, they are concerned about patients' comfort and pay little attention to their own health till they begin to experience discomfort in their body. With a little attention and creativity, dental surgeons can improve their comfort on the job during the course of their career.
Keywords: Dental surgeon, dentistry, ergonomics, musculoskeletal disorders, neutral position, risk factors, static postures, work efficiency, workplace
|How to cite this article:|
Shaik AR. Dental ergonomics: Basic steps to enhance work efficiency. Arch Med Health Sci 2015;3:138-44
| Introduction|| |
Musculoskeletal disorders (MSDs) are among the most common causes of long-term disability. Due to spiraling incidences of MSDs over a period of time and their subsequent impact on industrial profits and quality of individual lives, the MSDs have received considerable attention since 1990s from ergonomists, researchers and other healthcare professionals. MSDs were first described in 1700 A.D. and were only documented in the 19 th and 20 th centuries as many countries worldwide reported a so-called epidemic of MSDs. These epidemics served as the catalyst to investigate the causative factors of MSDs and the extent to which technological or societal changes may have impacted the occurrences of MSDs. 
Musculoskeletal disorders are a wide range of inflammatory and degenerative disorders of muscles, tendons, and nerves. These disorders can result in pain and functional impairment affecting the neck, upper back, lower back, shoulders, elbows, wrists, and hands.  Examples are carpal tunnel syndrome, tendonitis, thoracic outlet syndrome, and tension neck syndrome. Epidemiologic literature has grouped these disorders as clinically well-defined (such as tendonitis and carpal tunnel syndrome), less clinically well-defined (such as tension neck syndrome) and nonspecific (such as repetitive strain injury, cumulative trauma disorder, and overuse syndrome).  Nonspecific disorders are not considered a diagnosis, but rather an umbrella term for a disorder developing from various risk factors.  Work activities which are frequent and repetitive or activities with awkward postures cause these disorders which may be painful during work or at rest. Almost all work requires the use of the arms and hands. Therefore, most MSDs affect the hands, wrists, elbows, neck, and shoulders. Work using the legs can lead to MSDs of the legs, hips, ankles, and feet. Some back problems also result from repetitive activities. ,
Musculoskeletal disorders were a leading cause of worker impairment, disability, compensation costs, and loss of productivity in industrialized countries. The aging of the workforce and presence of physically demanding jobs contribute to the widespread occurrence of MSDs. Tasks that require forceful exertions place higher loads on the muscles, tendons, ligaments, and joints. Increasing force means increasing body demands such as greater muscle exertion along with other physiological changes necessary to sustain an increased effort. Prolonged or recurrent experiences of this type can give rise to not only feelings of fatigue but may also lead to musculoskeletal problems when there is inadequate time for rest or recovery. Force requirements may increase with: 
Most of the dental surgeons today perform their work in the sitting position while treating the patients in the supine position. Invariably the dental surgeons often have to perform their professional work in prolonged static postures.  Even in optimal seated postures more than one-half of the muscles of the body are contracted statically, and there is little movement of the vertebral joints. These result in physiological changes that can lead to back, neck or shoulder pain or MSDs. If regularly occurring pain or discomfort is ignored, the cumulative physiological damage can lead to an injury (macro change) or a career-ending disability.  In dentistry, bad working environment, repetitive tasks-such as scaling, root planning, and uncomfortable physical postures contribute greatly to MSDs, stress and loss of productivity. To perform efficiently and effectively, the dental surgeons shall always like to attain a position that allows them to achieve optimum access, visibility, comfort, and control at all times. 
- Use of an awkward posture,
- The speeding up of movements,
- Increased slipperiness of the objects handled (requiring increased grip force),
- Use of the index finger and thumb to forcefully grip an object (i.e., a pinch grip compared with gripping the object with the whole hand) and
- Use of small or narrow tool handles that lessen grip capacity.
Basic operating posture is considered to be an important occupational health issue for dental surgeons. It is generally agreed that the physical posture of the dental surgeon should be such that all the muscles are in a relaxed, well - balanced, and neutral position. Postures other than this neutral position are likely to cause musculoskeletal discomfort. Fostering and implementing good musculoskeletal health in dentistry is a real challenge for the physiotherapists and other allied health care professionals. Dental surgeons are prone to unique muscle imbalances and require special exercises and ergonomic interventions to maintain optimal health during the course of their career. 
Ergonomics, as a discipline, has its formal beginnings immediately after the Second World War. During this time, the focus of concern expanded to include worker safety, as well as productivity. The studies of efficiency carried out by psychologists on Pilots, Radar, and Sonar operators in Great Britain during the war and immediately after it, showed the importance of designing technologies that should adapt sizably, statically, and dynamically to the human body and that should stimulate the physical and mental status of the human beings. 
International Ergonomic Association defines Ergonomics (or human factors) as "the scientific discipline concerned with the understanding of the interactions among humans and other elements of a system, and the profession that applies theoretical principles, data and methods to design, in order to optimize human well-being and overall system." Ergonomics is the science of matching working conditions and human capabilities. The goal is to allow people to perform work and other activities safely and efficiently. The basic principle in ergonomics is to match tools, equipment, and work methods to the needs of the worker in order to enable him/her perform comfortably to his/her best. Thus, the need is to recognize conditions that lead to discomfort and implement changes to minimize or eliminate those conditions.
Modern ergonomics is an interdisciplinary applied science that studies the optimization possibilities of the man-machine system design by knowing the human's physical and mental possibilities and limits, his/her capacity to learn, the factors generating errors, the work, the physiology, the human behavior as an individual and within a team, the managerial possibilities, the organizational culture (interdisciplinary study of anatomy, physiology, psychology, management), and the technical and designing possibilities (engineering, design). 
Dental work poses some interesting ergonomic challenges. While performing normal professional work, the dental surgeons have to repeatedly change their positions like sitting, standing, and sometimes in one position (static posture) for long periods. They bend forward or to the side while working on patients. While treating the patients, the dental surgeons are concerned about patients' comfort and pay little attention to their own health till they begin to experience discomfort or pain in their body. With a little attention and creativity, dental surgeons can improve their comfort on the job. 
The muscular effort can be either static or dynamic. In static muscular effort, the length of the muscle remains unchanged called as an isometric contraction, whereas in dynamic muscular effort, there are rhythmic changes of lengthening and shortening of the muscles known as isotonic contractions. The posture is the complex term used as reference for a number of movements and posture concepts. The posture has been defined in various ways - a posture or a body position, the relative postures of the body parts for a specific activity. Pain, fatigue and disorders of the musculoskeletal system may result from sustained inadequate working postures and poor working conditions. Musculoskeletal pain and fatigue may influence posture control which can increase the risk of errors and may result in low work efficiency.
Good ergonomic design of the workplace is a basic requirement for improving musculoskeletal health. The nature of the dental profession and the positions assumed by the dental surgeons during an average work day have a huge impact on the dental surgeon's body and carries with it a high prevalence of MSDs. The effects of MSDs will manifest themselves not only in the reduction of working hours of efficiency of the dental surgeons but shall also result in a reduction in quality time spent with their family members and friends. Although the dental surgeons rarely miss their work due to the MSDs, it is more likely to lead to severe disability and a subsequent impact on the quality-of-life. It is further observed that the most common complaint among dental surgeons is how MSDs are impeding their personal life and the lack of leisure time between working periods for recovery. 
A poor ergonomically designed workplace may not show immediate ill health effect, because the human body has the capacity for adapting to a poorly designed workplace or structured job. However, the compounding effect of job and workplace deficiencies will surpass the body's coping mechanisms causing MSDs. The successful application of ergonomics assures high productivity, avoidance of illnesses and injuries and increased satisfaction among workers. Unsuccessful application of ergonomics, on the other hand, can result in MSDs. ,
It has been seen that the dental surgeons practicing over the years expose themselves to the increased risks of MSDs due to adopting either repetitive or awkward positions during their work. This has resulted in a high incidence of musculoskeletal and circulatory conditions such as scoliosis, kyphosis, lordosis, varicosities, and other leg and foot problems. While it may be impossible to completely eliminate all ergonomic exposures in dentistry, the detrimental effects of these hazards can be minimized through engineering controls such as workstation design/adjustment and through administrative controls such as creative scheduling and rest breaks. The variety of tasks performed by a dental surgeon provides the opportunity for "musculoskeletal relief" offered by alternating task assignments.
Dental surgeons and other allied healthcare professionals trained in ergonomics awareness programs are able to recognize early signs of discomfort or MSDs. Training also increases awareness of ergonomic risk factors, body mechanics, and helps them develop possible solutions to ergonomic concerns. Early reporting of symptoms gives the employer the opportunity to respond quickly, address concerns, and to head-off or alleviate potential MSDs problems. With the availability of highly sophisticated dental equipment, the potential for improving the occupational health of dental surgeons has expanded. But in spite of this development, dental surgeons continue to experience chronic back, neck, and shoulder pain as occupational hazards, , often resulting in early retirement from the profession. 
Using Sports Medicine approach, dentistry may be viewed as a profession much like a "sport." There is an abundance of dental surgeons with work-related pain and dysfunction. Dentistry poses a huge challenge because of the ergonomics of dental work. The biggest risk factors are the awkward prolonged seated postures with no back support and the limited range of motion and isometric muscle contraction created by working in a confined area, namely the mouth. The physiologic effects of these elements are patterns of muscle imbalance and neuromuscular inhibition causing dysfunction and/or pain. Advances in ergonomics continue to ease the physical challenges of the dental profession. Use of office ergonomics does not replace the basics of a body being physically conditioned. However, one must try to learn how to work around the various risk factors. The ultimate goal should be to prevent injuries and maintain the health of the dental surgeons by rehabilitative exercises. 
In an effort to reduce the physical fatigue of standing and the resultant adverse effects on health, dental stools began to be used in the 1950s and thus the term "sit down" dentistry was coined. However, the initial stools were single pedestaled and often tilted and rotated, presenting a safety problem. Since then the design of the stool has been greatly improved. Despite these changes, dental surgeons experienced frequent musculoskeletal complaints.
Dentistry in 21 st century
The 21 st century tends to give greater importance to the human factor, neglected frequently before in favor of the technological factor. The transition from the ergonomics centered on technology to the human-centered ergonomics is also now the major preoccupation of the industry, which eventually has decided to optimize the quality of the activity in parallel with the reduction of the risks which generate conditions specific to the occupation. Unlike the initiatives in the past, the human-centered ergonomics gives priority primarily to the patient, secondarily to the practitioner, and finally to the working place design. The design of the working environment that has to be adapted both for the patient and for the practitioner's requirements can be conceived only after establishing a correct relationship between the dental surgeon and the patient. 
Despite numerous technical advances in recent years, many occupational health problems still persist in modern dentistry. These include percutaneous exposure incidents, exposure to infectious diseases (including bioaerosols), radiation, dental materials and noise, MSDs, dermatitis and respiratory disorders, eye injuries, and psychological problems. Apart from biological hazards, dental surgeons continue to suffer a high prevalence of MSDs, especially of the back, neck, and shoulders. Although modern dentistry has been described as probably among the least hazardous of all occupations, many risks remain in dental practices which continue to challenge this status. 
Today, most of the dental surgeons work with patients seated in a reclining position. From chair side and with the continuous assistance of a dental nurse, "four-handed" dentistry is usually practiced. The dental surgeon is usually on the right of the patient and the dental nurse on the left. High and low-speed handpieces, ultrasonic scalers, and water and air syringes are usually placed on a platform over the patient's chest while the suction equipment is on the left side. Hand tools are on a movable tray that can be placed in front of, alongside or behind the patient, as needed. The work is usually carried out while seated, with elevated and unsupported arms, frequently away from the body, for example, when reaching for an instrument at arm's length. The requirements of vision and accuracy in the work cause forward bends and rotated positions of the body. The patient's mouth is a small surgical area where the dental surgeon has to handle a variety of tools while simultaneously having a good general view. 
Postures assumed by the dental surgeons during their professional work
In dental work, the majority of awkward positions are held for a longer time without moving. The postural rigidity imposed on the shoulder girdle (neck, shoulder, upper back) and lower back muscles are a major problem. The areas affected depend on their role:
For dental surgeons, holding awkward postures without moving, or with little movement for prolonged duration, generally have more serious consequences on the joints of the neck, shoulder, upper and lower back, than repetitive movements, which have more of an impact on the elbow and wrist joints. 
- The shoulders and upper back are contracted to stabilize the arms and to allow greater precision of hand movements
- The neck muscles (extensors) are contracted to keep the head tilted to one side
- The lower back muscles (spinal extensors) are contracted to hold the torso in a forward leaning position.
In order to see into the far reaches of a patient's mouth, dental surgeons have to bend their heads forward. The angles of flexion of the neck required in dental work far exceed safe angles of flexion for the neck when they are held for longer periods.
The following changes occur when the head is bent forward as shown in [Figure 1]: 
|Figure 1: The muscles of the neck and upper back are under pressure to support the weight of the head and keep it from falling down|
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A forward-head posture can lead to muscle imbalances contributing to a rounded shoulder posture.  This posture can predispose the operator to impingement of the supraspinatus tendon in the shoulder (rotator cuff impingement) when reaching for items. In addition, static posture of the arms in an elevated or abducted state of more than 30° impedes the blood flow to the supraspinatus muscle and tendon. Prolonged arm abduction also can lead to trapezius myalgia-chronic pain and trigger points in the upper trapezius muscle. ,
- The weight of the head (approximately 9% of the body's weight) is pulled downward
- The rotation point of the head is the first cervical vertebra
- The muscles of the neck and upper back are contracted to keep the weight of the head from falling down
- After certain amount of time, this constant pressure on the neck muscles to hold up the weight of the head can lead to pain.
Dental surgeons are required to adopt nonneutral postures for many of the clinical tasks they perform. These postures frequently require prolonged static contraction of the trunk, scapulothoracic, and scapulohumeral musculature, combined with repetitive contraction of muscles in the wrist, hand, and fingers during fine motor control work. Dental surgeons, for example, most commonly use a combination of a flexed and right-side flexion position of the neck with a head-down position, often combined with shoulder abduction or flexion as shown in [Figure 2]. 
|Figure 2: Typical position used by many dental surgeons with flexed and twisted neck and torso|
Click here to view
Dental surgeons assume these positions for the following reasons
Much dental work requires high precision and the muscles used in sustaining such activity are at the risk of becoming fatigued and causing discomfort. Stability maintained through static muscle loading in the shoulder for prolonged periods could lead to fatigue and discomfort. Prolonged contraction of the upper trapezius during upper extremity stabilization (without armrests) can cause compression of adjacent blood vessels and nerves making the upper extremity susceptible to temporary ischemia.
- To coordinate the relative positions between dental surgeon and assistant
- To obtain optimal view of teeth within the patient's mouth
- To provide a comfortable position for the patient
- To maneuver complex equipment and reach for instruments.
Theoretical "ideal position" and its effect on neck flexion
In a neutral-seated position as shown in [Figure 3], the torso is leaning back slightly between 100° and 110° (90° is vertical), the buttocks, thighs, and legs are supported and the back of the knee is free. The operative field (the patient's mouth) to be placed at the same height as the practitioner's elbows is held close to the body. This shows that the arms are at 0° from the horizontal axis or 90° to the shoulder.
The theoretical "ideal position" as shown in [Figure 4] is rarely observed in dental clinics because for many dental surgeons the eye-task distance is too great. Dental work requires bending the neck and back in order to be able to see and to perform extremely precise work in the patient's oral cavity.
|Figure 4: Theoretical "ideal position": Shoulders in line with the ears and arms at nearly 90°. The patient's mouth is positioned at elbow level, forearm angle at 0° from the horizontal axis. The eye-task|
distance is too great
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Therefore, an inability to see is what makes a dental surgeon bend his/her neck and back to be able to see and perform quality work in his/her patient's mouth. Extremely, bent-over positions are frequently observed as illustrated in [Figure 5]. Dental surgeons, therefore, have a great deal of difficulty maintaining a straight back and neck position when their arms are held at 0° from the horizontal axis.
|Figure 5: Neck fl exion (70°) and back flexion (20°) when forearms are at 15° from the horizontal axis. These are common positions when the patient is positioned low|
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Two examples of sequences [Figure 5] [Figure 6] [Figure 7] [Figure 8] are given comparing neck and back positions resulting from the angles of the forearms in relation to the horizontal axis. By raising the level of the patient's mouth and holding dental surgeon's arms up, the dental surgeon can straighten both neck and back as illustrated in [Figure 6] and [Figure 8].
|Figure 6: Neck position is reduced (30°) when raising the height of the patient's head. There is less need to bend over to see into the oral cavity. Forearms are at 30° from the horizontal axis|
Click here to view
|Figure 7: Neck flexion (70°) and upper back fl exion (45°) when the patient is positioned low. The forearms are at 10° from horizontal. Leg movements are limited by the back of the patient's chair|
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|Figure 8: Neck flexion (30°) and back fl exion are reduced when the height of the patient's head is raised. The forearms are at 40° from horizontal. The legs can move freely under the back of the patient's chair|
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When raising the patient's head, dental surgeons often have the impression that the patient's mouth is much too close to their eyes. However, when measured the distance between the eye and the mouth in [Figure 7] and [Figure 8], it is found that the distance was almost the same. In many cases, the dental surgeons had less difficulty getting used to working at this new height when their arms were supported by free-motion elbow supports.
Most of the dental work done by dental surgeons is performed with the arms unsupported because the majority of stools do not have arm rests. When a person's torso is bent forward, his/her back is usually not in contact with the narrow torso support on the dental surgeon's stool, used as a lumbar support. Some of the older stools have a lumbar support that cannot be adjusted forward, which is usually necessary to be able to lean on it while working in the patient's mouth. Lack of support increases static load on the lower and upper back muscles required to maintain working positions. 
| Conclusion|| |
Musculoskeletal disorders result in loss of work efficiency among dental surgeons, and the prevalence and severity of these disorders decrease by adopting ergonomic interventions. Interventions or prevention strategies require an awareness of "how to fit the job to the worker and not the worker to the job." Applying ergonomics to the practice of dentistry not only could provide safety benefits, but a practice might also improve performance objectives through greater productivity. The ergonomics and healthy workplace help the dental surgeons increase their performance without putting at risk their own health. One of the main goals of ergonomics in dentistry is to minimize the amount of physical and mental stress that sometimes occurs day to day in a dental practice.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
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