ABC of Work Related Disorders: HAZARDS OF WORK David Snashall 

Most readers of this series will consider themselves lucky to have an interesting job. However tedious others may find it, work defines a person--which is one reason why most people who lack the opportunity to work feel disenfranchised. As well as determining our standard of living, work takes up about a third of our waking time, widens our social network, constrains where we can live, and conditions our personalities. "Good" work is life enhancing, but bad working conditions damage your health. Occupational disorders in general practice

General practitioners are likely to see as much work induced illness as doctors who work in occupational medicine, who spend most of their time assessing fitness for work on preventive programmes. Such illnesses do not necessarily present at work, and, as only a minority of workers have access to an occupational health department, they usually first consult their general practitioner.

How occupational diseases present in general practice

Musculoskeletal problems 48% Respiratory problems 10% Psychological problems 10%

These days few doctors see classic occupational diseases such as pneumoconiosis, heavy metal poisoning, or the various forms of occupational cancer. However, several conditions commonly seen in general practice may be occupational in origin--such as back pain, dermatitis, deafness, and asthma. Many of the injuries sustained at work will also be seen and dealt with in general practice or in accident and emergency departments. Reporting occupational illnesses:

Occupational diseases are supposed to be reported to the Health and Safety Executive by employers (usually advised by doctors) under RIDDOR (Reporting of Injuries, Diseases, and Dangerous Occurrences Regulations), but this cannot be relied on--if these official statistics were the only source of information, occupational illness would seem to be very rare.

Surveys in Finland, where reporting is assiduous, have shown rates of occupational disease to be underestimated 3-5 times

When the 1990 Labour Force Survey asked workers themselves it found that 2.2 million people had had an illness that year which they thought was caused or made worse by their work. It was estimated that these illnesses led to 7% of all general practice consultations. Further cases of occupational disease come to light via the Department of Social

Security's compensation scheme for diseases prescribed under the Industrial Injuries Provisions of the Social Security Act 1975.

It has been estimated that 4% of cancer deaths in the United States are directly due to occupational causes. Industrial agents that cause cancer include aromatic amines (rubber and dye industries), asbestos, benzene, ionising radiation, nickel, polyaromatic hydrocarbons, and wood dust

Newer initiatives have enabled us to gain a much better picture of certain occupational diseases--notably the SWORD (Surveillance of Work Related and Occupational Respiratory Disease in the United Kingdom) and EPI-DERM reporting systems, which have collected data on respiratory and skin conditions respectively from general practitioners and specialists. These have now been supplemented by OPRA (Occupational Physicians Reporting Activity), which will include other occupational diseases.

If work related illness is diagnosed Prescribed disease--Proof that a patient has acquired one of these diseases may lead to substantial compensation. Urge patients, even if they are retired,to contact the Department of Social Security Reportable disease--If one of these diseases related to work is diagnosed by a doctor, an employer must by law report this to the Health and Safety Executive Notifiable infectious disease (under the Public Health Acts) must be reported by doctors to the local authority

Industrial injuries are reported more fully than occupational diseases despite the fact that their impact on workers' health is less. Their cause is usually obvious and recent, whereas cause and effect in occupational disease can be far from obvious and the exposure to the hazardous material may have occurred many years before.

Total cost of work related illness, injury, and other accidents was £6bn-£12bn (1-2% of gross domestic product) in 1990

Is an illness occupational?

Whereas asbestosis and chronic lead poisoning can hardly be described as anything other than occupational diseases (about 70 of these are listed by the Department of Social Security), this may not be true of conditions such as back pain in a construction worker or an upper limb disorder in a keyboard operator when activities outside work may be contributing. A lifetime working in a dusty atmosphere may not lead to chronic bronchitis and emphysema, but, when it is combined with cigarette smoking, it makes this outcome much more likely. Common conditions for which occupational exposure is an important but not the sole or even the major cause can be more reasonably termed work related disease rather than occupational disease.

Certain occupations carry a substantial risk of premature death while others are associated with the likelihood of living a long and healthy life. This is reflected in very different standardised mortality ratios for different jobs, but not all the differences are due to the various hazards of different occupations. Selection factors are important, and social class has an effect (although this is defined by occupation). Non-occupational causes related to behaviour and lifestyle may also be important.

Occupations associated with high and low standardised mortality ratios (all causes) 1979-83 Occupation Mortality ratio Tailors and dressmakers (single women) 194 Road surfacers (men) 165 Bus conductors (men) 150 All occupations (men and single women) 100 Medical practitioners (men) 66 Physical and geological scientists and mathematicians (men) 38 University academic staff (single women) 35

Presentation of work related illnesses

Diseases and conditions of occupational origin usually present in an identical form to the same diseases and conditions due to other factors. Thus, bronchial carcinoma has the same histological appearance and follows the same course whether it results from working with asbestos, uranium mining, or cigarette smoking.

The possibility that a condition is work induced may become apparent only when specific questions are asked because the occupational origin of a disease is usually discovered (and it is discovered only if it is suspected) by the presence of an unusual pattern. For example, in occupational dermatitis the distribution of the lesions may be characteristic. A particular history may be another clue: asthma of late onset is more commonly occupational in origin than asthma that starts early in life. Daytime drowsiness in a fit young factory worker may not be due to late nights and heavy alcohol consumption, but to unsuspected exposure to solvents at work.

The occupational connection with a condition may not be immediately obvious because patients may give vague answers when asked what their job is. Answers such as "driver," "fitter," or "model" are not very useful, and the closer a doctor can get to extracting a precise job description the better. Sometimes patients will actually have been told (or should have been told) that there are specific hazards associated with their job, or they may know that fellow workers have experienced similar symptoms.

An "engineer" may work directly with machinery and risk damage to limbs, skin,and hearing or may spend all day working at a computer and risk back pain, upper limb disorders, and sedentary stress

Timing of events

The timing of symptoms is important as they may be related to exposure events during work. Asthma provides a good example of this: many people suffering from occupational asthma develop symptoms only after a delay of some hours, and the condition may present as nocturnal wheeze. It is essential to ask whether symptoms occur during the performance of a specific task and if they occur solely on work days, improving during weekends and holidays.

Working conditions

Patients should be asked specifically about their working conditions. Common problems are dim lighting, noisy machinery, bad office layout, dusty atmosphere, draconian management, and bad morale. Such questioning not only investigates possibilities but gives the doctor a good idea of the general state of a patient's working environment and how he or she reacts to it. A visit to a patient's workplace, if it can be arranged, may be a revelation and just as valuable as a home visit if you want to understand how a patient's health is conditioned and how it might be improved. Knowing about somebody's work can help you to place the person in context and to gain insight. Patients are often happy to talk about the details of their work: this may be less threatening than talking about details of their home life and can promote a better doctor-patient relationship.

The causes of occupational disease can extend beyond the workplace to affect local populations by air or soil pollution and other members of workers' families when overalls soiled with toxic materials are taken home to be washed.

Changing trends in work related illnesses

Changes in working practices in Britain are giving rise to work that is more intense and stressful but also less physically demanding. There are more jobs in service industries, more working from home, more handling of newly developed products, and more women at work. This is not necessarily so in many developing countries, where headlong industrialization has led to sweatshop labour and where occupational accidents and diseases, both acute and chronic, are much more common. As important, of course, are the effects on health of an increasing rate of long term unemployment among the potential workers of the post-industrial world.

Doctors can obtain further information and help about occupational diseases from the Employment Medical Advisory Service, which is contactable through local branches of the Health and Safety Executive. The executive produces many publications for doctors, workers, and employers, and these are available from any HMSO outlet. In addition, there

Posture related problems for dentistsMost of us do not relish our periodic visits to the dentist nor do we eagerly await undergoing surgery. In these situations sympathy usually lies fairly and squarely with the patient. What many people fail to appreciate, however, is that these situations place considerable musculoskeletal demands on those health professionals, such as dentists and surgeons, whenever they are treating us in an attempt to improve the quality of our lives. For the patient, a dental visit typically involves sitting in a reclined or even supine position, and the dentist often has to contort the body to perform the oral work. In an operation we are usually unconscious, and supine on an operating table, and the surgeon must contort the body to perform the necessary surgery. From a physical effort standpoint there are many similarities between the work of dentists and surgeons: both professions typically involve working in a standing posture, both require prolonged stooping over a reclined or supine patient, both must use a variety of hand tools in a delicate manner, and both occupy extended periods of time, typically less than an hour per patient for a dentist and often considerably longer than an hour for a surgeon. The kinds of posture-related musculoskeletal problems reported by dentists and surgeons are comparable to those found in other professions involved prolonged standing work in poor postures.

Ergonomics Research on Dentists and SurgeonsA number of studies have examined the ergonomics issues associated with dentists and surgeons. Most of this work has focused on the symptoms experienced by dentists, perhaps because of their repetitive daily activity patterns when treating patients.

A questionnaire survey and an associated time study of 16 male dentists working in an urban clinic found that dentists spend around two-thirds of each day actually performing dental work. There was a relationship between work-related physical complaints and daily-performed dental practices. Electromyograms of back muscle activity were taken from ten different postural positions. The inclination of the body was used to categorize three types of dental care postures. The most common posture among the dentists, who were right-handed, was a right-forward leaning position. The dentists reported a number of musculoskeletal problems with their arms, neck and shoulders, with their eyes and hands, and with the low back, and the number of problems differed among the three types of postures. When the dentists were in postures involving lateral bending of 30 degrees, and internal rotation (twisting) of 15 degrees the amplitude of the electromyograms was substantially increased. The daily repeated deviated body positions of the dentists were associated with an increase in their work-related musculoskeletal complaints.

The estimated one year prevalence for troubles among members of the Danish Society for Craniomandibular Disorders found that 65% of members reported neck and shoulder problems, and 59% reported low back problems. A follow-up in a field study of postures and electromyography (shoulder/neck) during the three most common work tasks was conducted. Results showed that dentists worked with high static muscle activity levels in the back and shoulders, with prolonged upper arm abduction, and with prolonged neck flexion Previous research suggests that prolonged working for more than 75% of the time with the neck above 15

degrees flexion may be hazardous. The present study showed that dentists spent 82% of their time working in of more than 30 degrees. Also, dentists who spent the longest times with their patients reported the most problems.

A recent book titled “Ergonomics and the Dental Care Worker” (1) describes results from several different surveys of dentists in Nebraska, South Carolina, Canada, Denmark, Poland and Norway, which consistently showed that around 40%-60% report cervical symptoms and low back pains.

Using a mail questionnaire, the prevalence of subjective complaints among 54 male orthopedists and 63 male general surgeons was investigated. Respondents were asked about their subjective musculoskeletal complaints. On average the age of the surgeons was in the early 40’s, and they had worked as surgeons for between 16 and 18 years. They worked an average 9.5-hour day. Results showed a higher prevalence of musculoskeletal complaints among the orthopedists than the general surgeons. Shoulders and lower back pain symptoms were the most frequently reported complaints, followed by neck problems.

Together, research results show that back disorders are relatively commonplace among dentists and surgeons, and this problem relates to their working postures, equipment design and duration of working. Fortunately, there are steps that can be taken to minimize back problems.

Prevention of Neck, Shoulder and Back DisordersErgonomic recommendations for minimizing the risks of back injuries focus on improving working posture and equipment design. These include:

1) Change Posture - Alternate between sitting and standing to reduce postural fatigue and maximize postural variety, which helps to reduce static muscle fatigue.

2) Use Support - When sitting or standing, don’t lean forwards or stoop in an unsupported posture for prolonged periods. If you are sitting, sit up straight or recline slightly in a chair with good back support, and use a good footrest if necessary. If you are standing for prolonged periods try to find something to help you lean against.

3) Safe reaching - Avoid having to reach awkwardly to equipment and work close to the patient. Keep the items used most frequently within a distance of about 20 inches (50 cm). Use assistants to help move equipment into this zone.

4) Normal arm posture - Keep elbows and upper arms close to the body and don’t raise and tense the shoulders when working. Also, ensure that hand postures are not deviated because this could lead to wrist problems.

5) Use Comfortable Equipment - Use equipment that isn’t too heavy, that can be used without awkward upper body posture, and that feels comfortable to use. Ergonomically designed equipment helps to minimize stresses on the upper extremities and the back.

6) Manage Time - Avoid long appointments where possible, or intersperse these with frequent short rest breaks in which you change posture and relax the upper extremities.

Background. The authors reviewed studies to identify methods for dental operators to use to prevent the development of musculoskeletal disorders, or MSDs.

Types of Studies Reviewed. The authors reviewed studies that related to the prevention of MSDs among dental operators. Some studies investigated the relationship between the biomechanics of seated working postures and physiological damage or pain. Other studies suggested that repeated unidirectional twisting of the trunk can lead to low back pain, while yet other studies examined the detrimental effects of working in one position for prolonged periods. Additional studies confirmed the roles that operators’ flexibility and core strength can play in balanced musculoskeletal health and the need for operators to know how to properly adjust ergonomic equipment.

Results. This review indicates that strategies to prevent the multifactorial problem of dental operators’ developing MSDs exist. These strategies address deficiencies in operator position, posture, flexibility, strength and ergonomics. Education and additional research are needed to promote an understanding of the complexity of the problem and to address the problem’s multifactorial nature.

Clinical Implications. A comprehensive approach to address the problem of MSDs in dentistry represents a paradigm shift in how operators work. New educational models that incorporate a multifactorial approach can be developed to help dental operators manage and prevent MSDs effectively.

Dental operators often cannot avoid prolonged static postures, or PSPs. Even in optimal seated postures, more than one-half of the body’s muscles are contracted statically, and there is little movement of the vertebral joints. This may result in damaging physiological changes (microchanges) that can lead to back, neck or shoulder pain or musculoskeletal disorders, or MSDs (macrochanges).1

In this article, we provide a brief review of spinal anatomy and the biomechanics of sitting postures. This will provide a clearer understanding of how damaging physiological changes occur and enable operators to apply prevention strategies both in and out of the operatory.

In optimal seated postures, more than one-half of the body’s muscles are contracted statically.

   THE NATURAL SPINAL CURVES

 

In standing postures, the spine has four natural curves when viewed from the side: cervical lordosis, thoracic kyphosis, lumbar lordosis and sacral kyphosis (Figure 1 ).2

The curves are interdependent; a change in one curve will result in a change in the curve above or below it.3 Since the sacral curve is composed of five fused vertebrae, its movement is extremely limited. However, the remaining curves—especially the lumbar and cervical curves—are more mobile and can be influenced more easily. When the curves of the spine are present and balanced against the center of gravity, the spine is supported mostly by the bony structures of the vertebrae resting on top of one another. When these curves become either exaggerated or flattened, the spine increasingly depends on muscles, ligaments and soft tissue to maintain erect.

Figure 1. The four primary curves of the spine: cervical lordosis, thoracic kyphosis, lumbar lordosis and sacral kyphosis. Adapted with permission of the publisher from Saunders and Saunders.2

 When sitting unsupported—a frequent posture in dentistry—the lumbar lordosis flattens (Figure 2 ). The bony infrastructure provides little support to the spine, which now is hanging on the muscles, ligaments and connective tissue at the back of the spine, causing tension in these structures. Ischemia can ensue, leading to low back strain and trigger points. This flattening of the lumbar curve also causes the nucleus in the spinal disk to migrate posteriorly toward the spinal cord. Over time, the posterior wall of the disk becomes weak, and disk herniation can occur. Therefore, operators need to know about strategies they can use to maintain the essential lumbar lordosis whenever possible.

Figure 2. The effects of poor posture on the curves of the spine: flattened lumbar lordosis and a forward-head position.

 Maintaining the cervical lordosis in the proper position is equally important. Forward-head postures are common among dentists, due to years of poor posture involving holding the neck and head in an unbalanced forward position to gain better visibility during treatment (Figure 2 ). In this posture, the vertebrae no longer can support the spine properly, and the muscles of the cervical and upper thoracic spine must contract constantly to support the weight of the head in the forward posture.4 This can result in a pain pattern, which often is referred to as tension neck syndrome. This syndrome can cause headaches and chronic pain in the neck, shoulders and inter-scapular muscles, and it occasionally can radiate pain into the arms. Sustained contraction of cervical muscles also causes weakening of the spinal disks, with possible disk degeneration or herniation.5 Therefore, frequent relaxing and stretching of the neck muscles, strengthening of the deep postural cervical muscles and preservation of the cervical lordosis in proper posture (ear over the shoulder) with all activities, including sleeping and driving, is essential for optimal musculoskeletal health of the neck.

A forward-head posture also can lead to muscle imbalances,1 contributing to a rounded shoulder posture. This posture can predispose the operator to impingement of the supraspinous tendon in the shoulder (rotator cuff impingement) when reaching for items.

Additionally, static posture of the arms in an elevated or abducted state of more than 30 degrees impedes the blood flow to the supraspinous muscle and tendon.6,7 Prolonged arm abduction also can lead to trapezius myalgia—chronic pain and trigger points in the upper trapezius muscle.

To effectively prevent injuries in dentistry, prevention strategies and ergonomic techniques must address these postural and positioning difficulties, as well as subsequent detrimental physiological changes: muscle imbalances, stiff joints, muscle necrosis and spinal disk degeneration.

   POSTURAL AWARENESS TECHNIQUES

 Maintain the low back curve. Research shows that maintaining the low back curve—the lumbar lordosis—when sitting can reduce or prevent low back pain (Figure 3 ).8,9

The following practices can help maintain the low back curve.

Figure 3. Maintaining the low back curve facilitates proper posture and reduces pressure on disks and muscles.

 – Tilt the seat angle slightly forward five to 15 degrees to increase the low back curve.10 This will place your hips slightly higher than your knees and increase the hip angle to greater than 90 degrees, which may allow for closer positioning to the patient. Chairs without the tilt feature can be retrofitted with an ergonomic wedge-shaped cushion.

– Sit close to the patient and position knees under the patient’s chair if possible. This can be facilitated by tilting the seat and using patient chairs that have thin upper backs and headrests. For some operators, this positioning may cause shoulder elevation or arm abduction. In such cases, a different working position should be assumed.

– Consider using a saddle-style operator stool that promotes the natural low back curve by increasing the hip angle to approximately 130 degrees. Using this type of stool may allow you to be closer to the patient when the patient chairs have thick backs and headrests.

– Adjust the chair so your hips are slightly higher than your knees and distribute your weight evenly by placing your feet firmly on the floor. The forward edge of the chair should not compress the backs of your thighs.

– Use the lumbar support of the chair as much as possible by adjusting the lumbar support forward to contact your back.

– Stabilize the low back curve by contracting the transverse abdominal muscles. To do this while sitting, sit tall with a slight curve in the low back, exhale, pull your navel toward the spine without letting the curve flatten. Continue breathing while

holding the contraction for one breath cycle. Repeat five times. Strive to maintain this stabilization regularly throughout the workday.

– Pivot forward from your hips, not your waist. Stabilize the low back curve by performing the previous exercise before pivoting forward.

Use magnification. Proper selection, adjustment and use of magnification systems have been associated with decreased neck and low back pain, as they allow operators to maintain healthier postures.11 Keep the following in mind when choosing and using a magnification system.

– Operating telescopes or loupes are available with flip-up or through-the-lens designs. The declination angle of the scopes should allow you to maintain less than 20 degrees of neck flexion. Working in postures with greater than 20 degrees of neck flexion have been associated with increased neck pain.12 You should try several operating telescope models to determine which suits your needs and fits you best.

– The working distance should allow you to maintain optimal posture, with your shoulders relaxed and your elbows close to your sides.

– Magnification of x2 will allow you to see working field detail that is approximately identical to that you would see when hunching over the patient without scopes. Magnification greater than x2 provides enhanced visual detail but a smaller field of vision.

– Operating microscopes allow for the highest magnification of available systems with the greatest operating detail and promote the most neutral postures by design.

Adjust operator chair properly. According to Chaffin and colleagues,10 the era when sitting work posture problems were solved by simply providing a chair is over. Operators need to know how to adjust the features of their chairs to obtain maximal ergonomic benefits.

– Adjust your chair first. A common mistake operators make is positioning patients first, and then adjusting their chairs to accommodate the patients. Allowances can be made when working with patients who are elderly or disabled.

– Position the buttocks snugly against the back of the chair. The edge of the seat should not contact the backs of the knees. A seat that is too deep can encourage you to perch on the edge of the seat.

– Place feet flat on the floor and adjust the seat height up until thighs gently slope downward while the feet remain flat on floor. This helps maintain the low back curve and enables you to position your knees under the patient more easily.

– Move backrest up or down until the lumbar support nestles in the natural lumbar curve of the low back. Then angle the lumbar support forward to facilitate contact with the low back.

– Tilt the seat forward about five to 15 degrees. If you are beginning to work with the seat tilt function, start with a slight tilt and later increase the degree of tilt as is comfortable.

– Adjust armrests, which are designed to decrease neck and shoulder fatigue and strain, to support elbows in the neutral shoulder position.

There are many ergonomically designed operator chairs available. Because of varied operator body sizes and needs, you should try out several chairs on display at dealer showrooms or in the workplace. Many manufacturers and dealers allow for in-office trial periods, enabling operators to evaluate which model best suits their needs.

   POSITIONING STRATEGIES

 Avoid static postures. According to Lehto and colleagues,13 the concept of a single correct work posture may be physiologically invalid, as the human body may be made for movement and ever-changing postures.

Some dental schools and educational programs stress the importance of using one "home" position while working. While it is important to use ergonomically correct positions and postures, some studies suggest that several home positions may be better than one.9,14,15 Spending long periods in static positions increases a worker’s susceptibility to injury due to the mechanisms we discussed in a previous article.1

Increasingly, the literature supports the idea that workers should vary their work positions as often as possible to shift the workload from one group of muscles to another.6,9,10,14,15

Alternate between standing and sitting. Standing uses different muscle groups than does sitting; therefore, alternating between the two positions lets one group of muscles rest, while the workload is shifted to another group of muscles. Alternating between standing and sitting also can be an effective tool in preventing injuries.15 One study revealed that dentists who worked solely in a seated position had more severe low back pain than did those who alternated between standing and sitting.16

Reposition the feet. Subtle changes in foot position can shift the workload from one group of low back muscles to another, allowing the overworked tissues to be replenished with nutrients.

A common mistake among dentists is positioning patients too high.

Position patients at the proper height. A common mistake among dentists is positioning patients too high. This causes elevation of the shoulders and abduction of the arms, leading to prolonged static muscular tension in the neck and shoulders. Magnification enables operators to maintain a greater working distance and position patients at the proper height, with the shoulders relaxed and the forearms approximately parallel with the floor.

Operators should take the time to position their patients properly for mandibular and maxillary procedures. Generally, patients should be placed in a semisupine position for mandibular procedures and a supine position for maxillary procedures.

Avoid twisting. Operatory design plays an important part in how often dentists perform detrimental twisting movements during the workday. Rear delivery systems encourage extensive trunk twisting and shift of vision to retrieve instruments, and side delivery systems require moderate twisting. Transthorax (or over-the-patient) delivery systems minimize twisting and shift of vision. When possible, dentists should position instruments within easy reach. If the operatory design requires the dentist to turn to retrieve instruments or handpieces, the dentist should swivel the chair to face the area squarely instead of twisting the torso. Operators should try to retrieve items with the closest hand, especially with rear delivery systems, to avoid twisting or reaching across the body. Repeated unilateral twisting in one direction may result in muscle imbalances or structural tissue damage, leading to low back pain.17,18

   PERIODIC BREAKS AND STRETCHING

 Chairside directional stretching. Studies suggest that the increase in operator pain since the 1960s may be due to longer work periods without breaks, due in part to the use of four-handed dentistry techniques.14,19 Having operators take frequent breaks20

and reverse their positions is integral in an effective injury prevention program.

It is difficult for most dental operators to avoid PSPs. In optimal PSPs, muscle ischemia and joint hypomobility can occur due to prolonged muscle contractions. When assuming awkward PSPs, dental professionals are predisposed to developing muscle imbalances caused by repeatedly flexing forward, bending to the side and rotating in one direction. In general, dentists tend to lose flexibility in the direction opposite to that in which they are postured statically during the day.21

Stretches performed in the reverse direction of awkward PSPs may prevent muscle imbalances that can lead to pain and MSDs. Directional stretches can be performed in or out of the operatory and can be incorporated into a daily routine that facilitates balanced musculoskeletal health. Directional stretching involves a rotation, sidebending or extension component that generally is in the opposite direction of that in which the operator frequently works (Figures 4A-4D ). This strategy addresses the muscle imbalances that tend to develop.

Figure 4. Examples of chairside directional stretches. A. Neck and shoulder

Figure 4. Examples of chairside directional stretches. A. Neck and shoulder combination.

With the elbow at shoulder height and at a 90-degree angle, gently pull the arm across the front of body with opposite arm. Look over the shoulder being stretched and hold for two to four breathing cycles. Repeat. B. The untwister. With the knees wider than shoulder width, bend to the left side, resting the full body weight through the left elbow on the left knee. Stretch the right arm overhead and look toward the ceiling. Hold for two to four breathing cycles. Repeat. C. Upper trapezius stretch. Anchor the right hand behind the seat of the chair. Gently bring the left ear toward the left armpit. Hold for two to four breathing cycles. Repeat. D. Downward squeeze. Assume a neutral head posture (ears over the shoulders) and do not let the head move forward throughout the exercise. Lift the chest upward, position the arms at the sides with fingers pointing upward and palms facing forward. Roll the shoulders back and down, squeezing the shoulder blades downward and together. Hold for one long breath cycle. Repeat five times.

 Frequent stretching breaks address the detrimental physiological changes that can develop while working in optimal or awkward PSPs: ischemia, trigger points, muscle imbalances, joint hypomobility, nerve compression and disk degeneration. Furthermore, stretching

– increases blood flow to muscles;

– increases production of joint synovial fluid;

– reduces formation of trigger points;

– maintains normal joint range of motion;

– increases nutrient supply to vertebral disks;

– creates a relaxation response in the central nervous system;

– warms up the muscle before beginning to work;

– identifies tight structures that may be predisposed to injury.

How to stretch safely. To avoid injury during stretching, keep the following tips in mind:

– assume the starting position for the stretch;

– breathe in deeply;

– exhale as you slowly increase the intensity of the stretch up to a point of mild tension or discomfort;

– hold the stretch for two to four breathing cycles;

– slowly release the stretch and return to neutral position;

– repeat the stretch if time allows;

– avoid stretching in a painful range and discontinue stretching if it increases pain. – perform stretches in both directions to detect unilateral tightness (Figures 4A-4C illustrate stretching in one direction only);

– perform directional stretches primarily toward the tightest side throughout the workday and perform the stretches in both directions at home.

Stretching during microbreaks. To prevent injury from occurring to muscles and other tissues, the operator should allow for rest periods to replenish and nourish the stressed structures. If these breaks are too far apart, the rate of damage will exceed the rate of repair, ultimately resulting in breakdown of tissue

According to Karwowski and Marras,6 resting for more than 50 seconds does not result in an increased force-generation capacity, or strength, of the muscles. This indicates

that to optimize the strength capacity of the worker and minimize the risk of experiencing muscle strain, following a schedule of brief, yet frequent, rest periods would be more beneficial to workers than would lengthy infrequent rest periods.

In a study on the efficacy of microbreaks during the workday, McLean and colleagues22

found that by complying with regularly scheduled microbreaks, the subjects had less discomfort and that the addition of 30-second microbreaks showed no detrimental effect on worker productivity. Other authors have pointed to the efficacy of using micropauses and stretching during dental procedures.23–25 Stretches can be modified so that dental operators can perform the stretches easily at chairside, while wearing their gloves (Figure 5 ). Operators should perform directional stretches regularly throughout the day, both in and out of the operatory setting. They also can benefit by walking or performing other activities involving movement during longer breaks.

Figure 5. Chairside stretching can be performed during breaks such as while waiting for anesthetic to take effect in the patient.

 Trigger points. Sometimes, operators may experience pain that is not relieved with stretching but instead worsened by it. This pain may be caused by a sustained contraction inside a tight band of muscle known as a trigger point, which feels like a small hard knot.26 When firm pressure is applied, trigger points are painful and may refer pain to another area. They do not allow the muscle fibers to contract or relax; therefore, they effectively decrease flexibility and reduce blood flow to the muscle. It is important that operators release trigger points as soon as possible. Various people can help treat trigger points:

– a physical therapist trained in trigger point therapy, contract and relax technique or muscle energy technique;

– a neuromuscular therapist;

– a massage therapist trained in trigger point therapy;

– a physician trained in spray and stretch technique or trigger point injection;

– the dentist self-administering trigger point therapy using a tennis ball or other small ball between the back and a wall or using a trigger point self-massage tool.27

   STRENGTHENING EXERCISESMSDs in dentistry often begin with fatigue of the postural stabilizing muscles of the trunk and shoulders. As these muscles fatigue, operators tend to slump into poor posture, setting the stage for injuries. Dentists should perform specific strengthening exercises for the trunk and shoulder girdle to enhance the health and integrity of the spinal column, maintain good working posture, optimize the function of the arms and hands and prevent injuries.

Areas to strengthen include the trunk stabilization muscles, primarily the transverse and

oblique abdominal muscles and multifidus muscles; the stabilizing muscles of the shoulder girdle, mainly the middle and lower trapezius muscles; and the downward gliding muscles of the rotator cuff, the infraspinous, subscapular and teres minor muscles. Dentists should avoid over-strengthening the chest and anterior neck musculature, deltoid muscles and upper trapezius muscles, as this may exacerbate muscle imbalances to which they are prone. Areas to stretch include the chest musculature, hamstring muscles, low back muscles, buttock (piriform) muscles and hip flexor (iliopsoas) muscles. This combination of strengthening and stretching addresses a unique pattern of muscle imbalances that can develop among dental professionals.

Guidelines for exercise. Certain guidelines should be observed when beginning any exercise program:

– consult a physician before beginning any exercise program;

– do not perform strengthening exercises for painful or fatigued muscles;

– begin exercise gradually, starting with the minimum number of repetitions;

– stop exercise immediately if numbness, tingling, dizziness or shortness of breath occurs;

– perform strengthening exercises three to four times per week and stretching exercises daily;

– always exercise in a pain-free range.

Aerobic exercise. Aerobic exercise should be performed three to four times a week for at least 20 minutes. One major contributing factor to MSDs is decreased flow of nutrients and oxygen to muscles.1 Aerobic exercise increases blood flow to all of the tissues in the body and improves their ability to use oxygen. In addition, aerobic exercise improves cardiovascular and cardiorespiratory function, lowers heart rate and blood pressure, increases high-density lipoprotein (good) cholesterol, decreases blood triglycerides, reduces body fat, improves stress tolerance, increases mental acuity, improves sleep quality and may increase longevity.28 Operators should choose aerobic exercises that they enjoy. It is advisable to do at least two types of aerobic exercise regularly, for both variety and the benefits of cross-training. The results of a study assessing the musculoskeletal symptoms of dentists found that physical exercise can be a buffer against musculoskeletal ill health and stress for dentists over a wide range of ages.13

Stress management. It generally is accepted that dentistry can be a stressful occupation. Stress can elicit muscular contraction and pain, especially in the trapezius muscle.29 Operators may use various stress-reduction techniques to decrease stress-related muscular tension. They include breathing techniques, progressive relaxation, visualization, massage, aerobic exercise, meditation or yoga.

   EDUCATION

 As professionals, dentists understand the concept of being lifelong students so they can maintain their proficiency in clinical techniques that benefit their patients. To protect their own health, dentists should seek out and receive education about musculoskeletal health, injury prevention and dental ergonomics. Ideally, this education should begin during dental school and continue through the dentist’s professional life.

One dentist, however, has found that injury prevention and dental ergonomics education still is in its infancy.25 Most dental practitioners have not been trained in these areas, and they have not developed the skills and knowledge necessary to practice in a manner that is ergonomically correct. This lack of training is due in part to the need for more research and for better teaching tools and better-informed and -trained teachers. Part of the blame for the lack of training can be attributed to the magnitude of the task.

Dental operators can be taught to manage and prevent injuries effectively. They can educate themselves and their staff members using a multifactorial approach that includes preventive education, postural and positioning strategies, proper selection and use of ergonomic equipment, and frequent breaks with stretching and strengthening techniques before painful episodes occur. Prevention strategies should be easy to use to ensure long-term compliance.

CONCLUSIONSWork-related pain is common among dental professionals. The development of four-handed operatory techniques has made delivery of dental care more efficient and productive; however, it also has contributed to an increase in PSPs among operators. Because this problem is multi-factorial, any possible solution should be multifactorial as well.

Aerobic exercise should be performed three to four times a week for at least 20 minutes.

Available research supports the idea that this problem can be managed or alleviated effectively using a multifaceted approach that includes preventive education, postural and positioning strategies, proper selection and use of ergonomic equipment and frequent breaks with stretching and postural strengthening techniques. This represents a paradigm shift for daily dental practice. It is important that dentistry incorporate these strategies into practice to facilitate balanced musculoskeletal health that will enable longer, healthier careers; increase productivity; provide safer workplaces; and prevent MSDs.

Data regarding the presence and specific region of musculoskeletal pain were collected as part of a study that surveyed more than 5,000 dental personnel, dentists, and dental

auxiliaries. The magnitude of the overall study, which included all types of dental professionals, made possible identification of the prevalence of musculoskeletal pain and comparison of regions of pain among the different dental professionals.

STUDY DESIGN: In vitro force and deformation measurements formed the basis for determinate, quasistatic analysis of principal forces in the seated lumbar spine. OBJECTIVES: To explore the relationship between seated postures and the mechanical response in component tissues of lumbar intervertebral joints. SUMMARY OF BACKGROUND DATA: Despite the high prevalence of low back pain syndrome, the precise mechanisms relating specific mechanical loads to spinal degeneration are not well understood. Simultaneous, time-dependent measurement of anterior column forces and articular facet forces has not been presented previously. consequently, a determinate analysis of principal component forces has not been possible. METHODS: Twelve lumbar spines (L1-S1) were subjected to constant loading conditions while in flexed and extended seated postures. Time-dependent forces were measured in the anterior column at the L4 and L5 superior endplates and in the four facets of the L3-L4 and L4-L5 motion segments. A quasi-static analysis of sagittal plane forces was used to compute the remaining principal joint forces, including ligament, disc shear, and facet impingement forces. RESULTS: Component forces changed under static loading in both postures. There were significant differences between the mechanical responses of the two postures. Although the vertical creep displacement was greater in the extended seated posture (3.22 mm versus 2.11 mm), the escalation of forces was more severe in the flexed posture. CONCLUSIONS: The results suggest a mechanism of force balancing in lordotic postures under static loads, whereas flexed postures produce large increases to the tensile forces in the region of the posterior anulus.

New technologies and changes in dental care, including the proprioceptive derivation (Pd) concept, aimed at providing dentists with greater comfort and better health, were introduced in Thailand. The aim of this study was to investigate the differences in dentists' working postures when adopting different work concepts: Pd and the conventional concept. The results showed differences in dentists' sitting posture, clock-related working positions, and Rapid Upper Limb Assessment (RULA) scores. This implied that Pd helped dentists to discover new ways of positioning themselves, and working comfortably and effectively, which made it possible for them to adopt better working posture and have lower RULA scores. In conclusion, the Pd concept had a positive effect on dentists' working posture.

How to Cope When You Have Low Back Pain: Lifting, Reaching, Sleeping and More

Lifting Objects - Try to avoid lifting objects if at all possible.

- If you must lift objects, do not try to lift objects that are awkward or are heavier than 30 pounds.

- Before you lift a heavy object, make sure you have firm footing.

- To pick up an object that is lower than the level of your waist, keep your back straight and bend at your knees and hips. Do not bend forward at the waist with your knees straight.

- Stand with a wide stance close to the object you are trying to pick up and keep your feet firm on the ground. Tighten your stomach muscles and lift the object using your leg muscles. Straighten your knees in a steady motion. Don't jerk the object up to your body.

- Stand completely upright without twisting. Always move your feet forward when lifting an object.

- If you are lifting an object from a table, slide it to the edge to the table so that you can hold it close to your body. Bend your knees so that you are close to the object. Use your legs to lift the object and come to a standing position.

- Avoid lifting heavy objects above waist level.

- Hold packages close to your body with your arms bent. Keep your stomach muscles tight. Take small steps and go slowly.

- To lower the object, place your feet as you did to lift, tighten stomach muscles and bend your hips and knees.

Reaching Overhead - Use a foot stool or chair to bring yourself up to the level of what you are reaching.

- Get your body as close as possible to the object you need.

- Make sure you have a good idea of how heavy the object is you are going to lift.

- Use two hands to lift.

Sleeping and Lying Down - Select a firm mattress and box spring set that does not sag. If necessary, place a board under your mattress. You can also place the mattress on the floor temporarily if necessary.

- If you've always slept on a soft surface, it may be more painful to change to a hard surface. Try to do what's most comfortable for you.

- Use a back support (lumbar support) at night to make you more comfortable. A rolled sheet or

towel tied around your waist may be helpful.

- Try to sleep in a position which helps you maintain the curve in your back (such as on your back with a lumbar roll or on your side with your knees slightly bent). Do not sleep on your side with your knees drawn up to your chest.

- When standing up from the lying position, turn on your side, draw up both knees and swing your legs on the side of the bed. Sit up by pushing yourself up with your hands. Avoid bending forward at your waist.

Other Helpful Tips - Avoid activities that require bending forward at the waist or stooping.

- When coughing or sneezing, try to stand up, bend slightly backwards to increase the curve in your spine when you cough or sneeze.

- Sit as little as possible, and only for short periods of time (10 to 15 minutes).

- Sit with a back support (such as a rolled-up towel) placed at the hollow of your back.

- Keep your hips and knees at a right angle (use a foot rest or stool if necessary). Your legs should not be crossed and your feet should be flat on the floor.

- Here's how to find a good sitting position when you're not using a back support or lumbar roll: Sit at the end of your chair and slouch completely. Draw yourself up and accentuate the curve of your back as far as possible. Hold for a few seconds. Release the position slightly (about 10 degrees). This is a good sitting posture.

- Sit in a high-back chair with arm rests. Sitting in a soft couch or chair will tend to make you round your back and won't support the hollow of your back.

- At work, adjust your chair height and work station so you can sit up close to your work and tilt it up at you. Rest your elbows and arms on your chair or desk, keeping your shoulders relaxed.

- When sitting in a chair that rolls and pivots, don't twist at the waist while sitting. Instead, turn your whole body.

- When standing up from the sitting position, move to the front of the seat of your chair. Stand up by straightening your legs. Avoid bending forward at your waist. Immediately stretch your back by doing 10 standing backbends.

Driving

- Use a back support (lumbar roll) while sitting or driving in the car.

- Move the seat close to the steering wheel to support the hollow of your back.

Standing - Stand with your head up, shoulders straight, chest forward, weight balanced evenly on both feet and your hips tucked in.

- Avoid standing in the same position for a long time.

- If possible, adjust the height of the work table to a comfortable level.

- When standing, try to elevate one foot by resting it on a stool or box. After several minutes, switch your foot position. " While working in the kitchen, open the cabinet under the sink and rest one foot on the inside of the cabinet. Change feet every 5 to 15 minutes.

Stooping, Squatting and Kneeling Decide which position to use. Kneel when you have to go down as far as a squat but need to stay that way for awhile. For each of these positions, face the object, keep your feet apart, tighten your stomach muscles and lower yourself using your legs.

Mechanical stress and dysfunction, affecting the musculo-skeletal system can often be traced to habitual mis-use of the body. Other causes, including congenital faults, such as supernumary vertebrae, cervical ribs, congenital short leg etc, or traumatic events such as whiplash injuries, or blows and falls, or the effects of long standing emotional stress (see previous chapter), should also be considered.

The daily habits of posture and use, at work and leisure, are frequently the unobtrusive, non-violent, yet persistent factors which mitigate towards somatic dysfunction and the consequences of general ill-health. Posture represents the sum of the mechanical efficiency of the body. It may be read as a book, to assess the integrity, potential, and to some extent, the history of the individual.

The ideal posture is one in which the different segments of the body, the head, neck chest and abdomen are balanced vertically one upon the other so that the weight is borne mainly by the bony framework with a minimum of effort and strain on muscles and ligaments. For such posture to be maintained, special postural muscles must be in a state of constant activity. These have a special physiological property called 'postural activity'. Correct posture is one in which the head is centered over the pelvis the face directed forwards, and the shoulder girdle approximately on the same plane as the pelvis.

The position of the bony framework is determined by the soft tissues which invest, support, bind and move it. Faulty tensions in these soft tissues will lead to abnormalities in the skeletal structures, and therefore to function itself. This may also result in changes in the organs and

functions (circulation) which are supported by soft tissues. Not only are the soft tissues subject to gravitational stress, but also to a battery of postural and occupational stresses overlaid with the normal contraction that come with age. Goldthwait [1] points to the importance of posture in the maintenance of health:

It has been shown that the main factors which determine the maintenance of the abdominal viscera in position are the diaphragm and abdominal muscles, both of which are relaxed and cease to support in faulty posture. The disturbances in circulation from a low diaphragm and ptosis (sagging organs) may give rise to chronic passive congestion on one or all of the organs of the abdomen and pelvis, since the local as well as general venous drainage may be impeded by the failure of the diaphragmatic pump to do its full work in the drooped body. Furthermore, the drag of these congested organs on their nerve supply, as well as the pressure on the sympathetic ganglia and plexuses (nerve centres), probably causes many irregularities in their function, varying from partial paralysis to overstimulation. Faulty body mechanics in early life, then, become a vital factor in the production of the vicious cycle of chronic diseases and present the chief point of attack in its prevention .... In this upright position, as one becomes older, the tendency is for the abdomen to relax and sag more and more allowing a ptosic condition of the abdominal and pelvic organs unless the supporting lower abdominal muscles are taught to contract properly. As the abdomen relaxes, there is a great tendency to a drooped chest, with a narrowed rib angle, forward shoulders, prominent shoulder blades, a forward position of the head, and probably prorated feet. When the human machine is out of balance physiological function cannot be perfect; muscles and ligaments are in an abnormal state of tension and strain. A well poised body means a machine working perfectly, with the least amount of muscular effort, and therefore better health and strength in daily life. Thus an orthodox medical scientist reiterated the osteopathic message. Soft tissues which have been subjected to stresses, of a postural nature, may become chronically stretched or shortened. Normalization, where possible, must involve treatment (soft tissues and joint manipulation), exercise, and above all re-education, to prevent recurrence. A combination of osteopathy and a system of postural re-education, such as Alexander technique, would seem to be the ideal.

Repetitive StressModern man constantly abuses his body. Consider the compound effects of repetitive industrial or clerical occupations; of driving; of accommodating the body to ill-designed, mass produced furniture or equipment; of physiologically damaging footwear, such as shoes with high heels; and of restrictive undergarments; of habits such as crosslegged sitting, or standing with the weight on only one leg, etc. Just for a moment consider what the body has to cope with in a 'normal day'. Having slept on a too soft bed, the body is obliged to bend or stretch itself through the rigours of washing, shaving and dressing. Wash basins being of uniform size and bodies growing to random lengths can cause stress, even in the simple act of washing the face. The body next finds itself seated in a car, a train or a bus, and then subjected to hours of repetitive duties, either at a desk, at a workbench or in the home, etc. All this is being done on high heels or at a too low or too high desk, or in a seat too deep or too shallow, and in an habitually one-sided manner, with a slouch or stoop. It is not surprising that man has been

described as 'a biped animal with backache'.

With this constant repetitive stress we can see why the degeneration of the spinal joints is well advanced by middle-age and why backache, stiff necks and general signs of 'wear and tear' are the rule rather than the exception.

When standing correctly the weight of the body is evenly distributed. A line drawn downwards from the ear should run through the centre of the ankle bone. If it falls in front of this point then the muscles of the neck and spine will be under stress in order to support the head. As the head is held forward of its correct position there occur compensating changes in the normal curves of the spine. These changes, if prolonged, produce permanent alterations which will have their effect on every aspect of body mechanics. Similar problems occur if the head is held to one side or if the pelvis is in a position of forward or backward tilting. The problem is to know how to correct these habitual postural mistakes.

It is interesting to realize that the position of the head and neck in relation to the trunk has a determining effect on the whole economy of the body. The position of the organs of the body is maintained by the fascial bands that support them. The fascia that decides the relative position of the heart, the liver or the spleen, for example, is attached directly to the fascia of the neck, which is joined to the base of the skull. Thus any permanent deviation from normal in this area will have widespread ramifications. Once again we see how the body parts interrelate.