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Dentistry particularly the practice of general dentistry is a high risk profession with the reference to development of musculoskeletal disorders as the need for increased visualization of the operating field results in the adoption of affixed postures. The aims of this paper is to high light the extent of musculoskeletal problems faced by the dental professionals and to emphasize their management with specific and general recommendations.

It is hoped that the paper will help dental professionals to adopt correct postures, which will enhance their working capacity to work in a pain free environment and to deliver quality dental care to their patients.

Key words: Occupational hazard, musculoskeletal pain, ergonomics, dental practice.


Ergonomics is the science of fitting workplace conditions and job demands to the capabilities of the working population. The successful application of ergonomics assures high productivity, avoidance of illnesses and injuries, and increased satisfaction among workers. Unsuccessful application, on the other hand, can lead to work-related musculoskeletal disorders (MSDs).

The term work-related musculoskeletal disorders (MSDs) refers to musculoskeletal disorders to which the work environment contributes significantly or to musculoskeletal disorders that are made worse or longer lasting by work conditions or workplace risk factors.


The causes of any particular case of a MSD are exceedingly difficult to identify with complete accuracy. The primary occupational risk factors for MSDs  include:

Mechanical stresses
Cold temperature
Extrinsic stress

A risk factor itself is not necessarily a causation factor for any particular MSD. Many times it is not simply the presence of a risk factor, but the degree to which the risk factor is expressed that may lead to MSD. Similarly, to the extent a MSD case is attributable to a risk factor, often it will be a combination of multiple risk factors, rather than any single factor, which contributes to or causes an MSD.

In evaluating any particular case of a MSD, that risk factors may be experienced by the affected individual during non-occupational activities. In addressing any ergonomic issue, it would be a mistake to focus solely on the workplace.

Each of these work factors is discussed in more detail below.

Repetition :. Repetition rate is defined as the average number of movements or exertions performed by a joint or a body link within a unit of time.  Repeated identical or similar motions performed over a period of time could cause over-extension and overuse of certain muscle groups, which could lead to muscular fatigue. Interestingly, symptoms often relate not to the tendon and muscle groups involved in repetitive motions, but to the stabilizing or antagonistic tendon and muscle groups used to position and stabilize the extremity in space.

Force. Force is the mechanical or physical effort to accomplish a specific movement or exertion. The amount of force required by an activity can sometimes be magnified causing even more muscular fatigue.

Mechanical Stresses. Mechanical stresses are defined as impingement or injury by hard, sharp objects, equipment or instruments when grasping, balancing or manipulating. Mechanical stresses are encountered when working with forearms or wrists against the edge of a desk or work counter. The muscles and tendons are impinged when pressed into the sharp edge.

Posture. Posture is the position of a part of the body relative to an adjacent part as measured by the angle of the joint connecting them. Posture is one of the most frequently cited occupational risk factors.

There is a neutral zone of movement for every articulating joint in the body. For each joint the range of motion is defined by movements that do not require high muscular force or cause undue discomfort. Injury risks increase whenever work requires a person to perform tasks with body segments outside their neutral range in a deviated posture.

For the upper arm and shoulder area neutral posture is relaxed with the shoulders down and on the same plane, with arms at the side. Working with the arms abducted away from the body, overextended and shoulders hunched places these joints at the end of their normal range of motion, requires higher muscular force and greatly increases the risk for injury.

Posture and positioning profile factors such as torso twist, tipped shoulders, head tilt/rotation, raised elbows (either dominant, non-dominant, or both) and operating with hands close to the face are associated with increased risk of musculoskeletal symptoms

Vibration. Vibration has been found to be an etiological factor in work environments utilizing tools vibrating in the frequency band of 20 to 80 hz.1 Dental handpieces and powered automatic instruments operate at higher frequencies in the 5000 to 10,000 hz range, and duration of exposure to vibratory force during dental procedures is relatively short.

Cold Temperature. Low temperatures reduce manual dexterity and accentuate the symptoms of nerve-end impairment.2

Extrinsic Stress. Extrinsic stress, or sometimes called organizational factors, can be defined as the way in which work is structured, supervised and processed.5 Extrinsic stress reflects the objective nature of the work process. It may include such variables as job variety, job control, workload, time pressure, and financial constraints.

Some predisposing factors (i.e., age, rheumatoid arthritis, renal disease, hormonal imbalances, diabetes, hypothyroidism) are biological mechanisms that could account for an increased occurrence of tissue damage and MSDs. For other factors (i.e., weight, wrist dimension) Still other factors are even less well established (i.e. genetics, general conditioning). In addition, there are a host of non-work risk factors inherent to the hobbies and other activities a person engages in when away from work (i.e., knitting, crocheting, bowling, computer use, excessive driving)


Back Problems

Lower back pain.

Low back pain is second only to the common cold as the main reason for seeking medical attention.3,4

The cause of LBP is often multifactorial.  Any tissue or structure innervated with afferent nerve fibers has the potential to be a pain generator. That includes muscles, ligaments, facet and sacroiliac joints, intervertebral discs, nerve roots, and bony periosteum. However, this only addresses the “end organ” cause of pain. There can be many other biomechanical and functional deficits that might lead to tissue pain. In addition, the degenerative cascade affects multiple areas of the lumbar spine, including potentially, all of the pain generators.8

A fall, sudden jarring, or lifting incident can initiate the onset of pain in all of the tissues. However, certain persons are at increased risk of injury. Disc herniation occurs more frequently in middle age, usually due to early effects of degeneration of the outer disc annulus, combined with increased disc swelling pressure of the inner nucleus.

It has also been described that combined motions of lumbar flexion with rotation increase risk to the lumbar disc.

Furthermore, back pain can exist due to underlying normal age related processes, become exacerbated by abnormal postures, relative weakness and decreased endurance, and then exacerbated by a “specific” injury.

The treatment of low back pain has to be individualized for each patient. While there is little hard scientific evidence to support one specific intervention over all others, postural correction, proper patient positioning, general exercise, and possibly specific physical therapy techniques and/or manipulation may be beneficial.

Upper back pain.

Some individuals report extensive pain in the mid and upper back (thoracic area). The thoracic spine is designed for support in standing and for caging the vital organs, and is quite strong.8

Of course trauma or injury from strain could cause pain. Although the spinal structures (bones, discs, nerves) are less commonly injured, some conditions such as osteoporosis can predispose one to specific conditions such as compression fractures. Also, the thoracic spine is frequently involved in idiopathic scoliosis (side to side curve) or kyphosis (excessive forward curve). These can later develop into painful conditions, although the exact source and cause is often unclear.

Probably a more frequent cause of mid back pain, but again difficult to precisely diagnose, is muscular pain from the postural muscles and scapular muscles. The contributions of abnormal posture, static postures, poor strength and endurance, and overall individual conditioning need to be taken into account.

Hand and Wrist Problems

MSDs of the hand and wrist can take a variety of forms, such as, cumulative trauma disorder, repetitive strain injury, occupational repetitive micro-trauma, repetitive motion injury, overuse syndrome, carpal tunnel syndrome and repetitive stress disorder.2 A predominant cause of repetitive motion hand disorders is constant flexion and extension motions of the wrist and fingers.  Other common contributing factors to hand and wrist injuries include movements in which the wrist is deviated from neutral posture into an abnormal or awkward position; working for too long a period without allowing rest or alternation of hand and forearm muscles; mechanical stresses to digital nerves from sustained grasps to sharp edges on instrument handles, forceful work, and extended use of vibratory instruments.

Some of the specific hand and wrist conditions are discussed below.

Tendinitis/Tenosynovitis. Tendinitis and tenosynovitis refers to inflammation of the tendon and tendon sheath, respectively.  Inflammation can occur in any of the tendons of muscles that control the movement of the fingers, wrist and forearm.

The most common types of tenosynovitis of the hand and wrist are those involved with the muscles of the thumb and index finger.

DeQuervain’s Disease. DeQuervain’s disease is an inflammation of the common tendon sheath of two muscles to the thumb – abductor pollicis longus and extensor pollicis brevis.

Predisposing activities include postures that maintain the thumb in abduction and extension, forceful gripping, and thumb flexion combined with wrist ulnar deviation.10 Symptoms include sharp pain and swelling over the radial sytloid process of the wrist, the bony prominence just proximal to the wrist joint.

Trigger Finger. Tenosynovitis can progress causing a narrowing of the inflamed tendon sheath preventing the smooth movement of the tendon through the digital pulley system. A nodule will form on the tendon creating a “clicking” or “triggering” movement. Tenosynovitis of the finger is due to sustained, forceful power grip and/or repetitive motion. Symptoms include pain during physical movements that place the tendons in tension; and the presence of warmth, swelling and tenderness of the tendon on palpation.2


Cumulative trauma disorder, repetitive strain injury and repetitive stress disorder are terms often used to describe the condition when the nerves innervating the hands are compressed. Any of the three nerves of the hand – medial, radial, or ulnar – may be affected.4 The most common of these nerve compressions for dentistry, as well as for the general population, is carpal tunnel syndrome.

Carpal tunnel syndrome is difficult to deal with in the occupational setting because so many non-work factors may be involved. Numerous studies confirm that patients diagnosed with work-related carpal tunnel syndrome have a high prevalence of concurrent medical conditions that are capable of causing carpal tunnel syndrome without respect to any particular occupation.6-9 These medical factors include a genetic predisposition, obesity, metabolic or inflammatory diseases (i.e., arthritis, diabetes, hypothyroidism, neoplasms, gout, myxedema, amyloidosis, multiple myeloma); and hormonal factors (i.e., pregnancy, oral contraceptives, hormone replacement, menopause).

Symptoms of carpal tunnel syndrome include:

  • Tingling or numbness in the hand
  • Shooting pain from the hand up the arm
  • A swollen feeling in the hand without visible swelling
  • Hand weakness and clumsiness of the hands especially in the morning
  • Stiffness and numbness in the thumb, index finger, middle finger and radial side of   the ring finger
  • Difficulty grasping and pinching
  • Frequently dropping objects due to reduced sensation to touch
  • Symptoms are worse at night
  • Occurs most often in the dominant hand but is frequently bilateral

Guyon’s Syndrome. Guyon’s syndrome, or ulnar neuropathy most commonly occurs secondary to compression or injury at the elbow as the ulnar nerve passes through themcubital tunnel.  Compression of the ulnar nerve can occur just proximal to Guyon’s canal or at the distal end where the motor branch of the ulnar nerve enters an arcade of ligaments and tendons.10

Symptoms of ulnar neuropathy generally include pain, numbness and/or tingling in the distribution of the ulnar nerve in the ring finger and the small finger; and a shooting electrical sensation down the ulnar aspect of the arm. Motor symptoms are less common, but may include loss of control of the small finger, weakness and clumsiness of the hand.10


1. Armstrong TJ, Lifshitz Y. Evaluation and Design of Jobs for Control of Cumulative Trauma Disorders. Ergonomic Interventions to Prevent Musculoskeletal Injuries in Industry. Chelsea, Lewis Publishers, Inc., 1987.

2.Gerwatowski LJ, McFall DB, Stach DJ. Carpel Tunnel Syndrome Risk Factors and Preventive Strategies for the Dental Hygienist. J Dental Hygiene 2:89-94, 1992.

3.Center for Ergonomics. Introduction to Upper Limb Musculoskeletal Disorders. The University of Michigan College of Engineering, Ann Arbor, Online Training, Inc., 1998.

4. Carayon P, Smith MJ, Haims MC. Work Organization, Job Stress, and Work-Related Musculoskeletal Disorders. Human Factor 41(4):644-663, 1999.

5.  ANSI (1993) Control of Cumulative Trauma Disorders. ANSI 2-365, Illinois.

6.  Bramson JB, Smith S, Romagnoli G. Evaluating Dental Office Risk Factors and Hazards. JADA 129:174-183, 1998.

7.  Guay AH. Commentary: Ergonomically Related Disorders in Dental Practice. JADA  129:184-186, 1998.

8.Chin D, Jones N. Repetitive Motion Hand Disorders. J California Dental Association  30(2):149-160, 2002.

9. Andrews N, Vigoren G. Ergonomics: Muscle Fatigue, Posture, Magnification and Illumination. Compendium 23(3):261-272, 2002.

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