1. Ergonomics
Chapter 25
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2. Chapter 25 Lesson 25.1
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3. Learning Objectives Pronounce, define, and spell the Key Terms.
Describe the goal of ergonomics.
Identify common symptoms of musculoskeletal disorders.
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4. Introduction
Ergonomics deals with adaptation of the human body to the work environment. Ergonomic conditions are simply the safest, most efficient, and easiest way to work.
The word “ergonomics” comes from the Greek words ergon (work) and nomos (law of work).
The goal of ergonomics is to help people stay healthy and at the same time perform their work more effectively by changing the design of the workplace, instruments, systems, products, training, or some combination of these elements.
The Occupational Safety and Health Administration (OSHA) has a comprehensive four-pronged approach: guidelines, enforcement, outreach and assistance, and a national advisory committee on ergonomics.
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5. Fig. 25-1 Ergonomic factors in dentistry.
Ask students to name eight ergonomic chairside tips.
What is the importance of avoiding repetitive movement?
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6. Musculoskeletal Disorders
Headaches, neck and shoulder pain, back pain, and carpal tunnel syndrome (CTS; a wrist injury) account for many disabling and potentially career-ending musculoskeletal disorders among dental professionals.
Work habits, posture, and equipment and instrument design can contribute to these work-related disorders.
What are some of the more common conditions identified as musculoskeletal disorders reported by employees? (Tendinitis, tenosynovitis, epicondylitis, CTS, bursitis, De Quervain disease, ganglion cyst, thoracic outlet syndrome, sprains, strains, tears, general pain.)
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7. Chapter 25 Lesson 25.2
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8. Learning Objectives
Identify three categories of risk factors that contribute to increased risk of injury.
Demonstrate the neutral working position.
Describe the symptoms of CTS.
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9. Ergonomics in the Dental Office
Members of the dental team usually perform their work in a seated position, often with excessive motions and unbalanced postures.
Work-related musculoskeletal disorders can include back pain, joint pain, neck and shoulder pain, hand and wrist pain, and headaches.
The early onset of pain should alert you to an imbalance; if it is ignored, more serious damage can occur over time.
It is important for the dental assistant to understand how to implement ergonomic changes and methods.
What should the dental assistant do at the first sign of pain?
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10. Risk Factors
Three interrelated factors contribute to increased risk of job-related injury:
Posture
Repetition
Force
In 1994 the Bureau of Labor Statistics recorded data on workplace-related injuries. How many cases do you think were the result of overexertion or repetitive motion? (705,800 cases, which accounted for 32% of all cases.)
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11. Posture
Posture affects the ability of the dental assistant to reach for, hold, and use equipment.
It also influences how long the dental assistant can perform a task without suffering adverse health effects.
Over time, any position will eventually become fatiguing and may lead to lower-back pain.
Consider alternating assisting at chairside with other dental assistants in the office to give each other some variety in positions.
(Cont’d)
Studies by the Department of Labor provide strong evidence of a relationship between posture and neck and neck/shoulder pain.
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12. Posture
(Cont’d)
Establish a neutral position by sitting upright with your weight evenly distributed.
Your legs should be separated and your feet flat on the chair footrest.
Your back should be pressed against the back of the chair for lumbar support.
Your hips should be tilted forward to rotate the pelvis backward. The properly aligned spine resembles a gentle S.
When the spine is properly aligned, the ears, shoulders, and hips are in straight vertical alignment, providing balance, support, and equal distribution of weight.
Ask students to look around at the position of other students and practice sitting in the neutral position.
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13. Posture
(Cont’d)
There is a tendency for the dental assistant to deviate from the neutral position while assisting the dentist.
Examples of such deviations include leaning forward, twisting, overbending the back, and reaching.
These poor postures can lead to aches, pains, numbness, and tingling. Ideally, sitting and standing should be alternated whenever possible.
Back pain is the most prevalent and expensive work-related musculoskeletal disorder among U.S. industries, according to the National Institute for Occupational Safety and Health.
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14. Fig. 25-2 A, Dental assistant in poor position
Fig A, Dental assistant in poor position. B, Dental assistant in proper position.
Take a survey of the class, asking whether they chairs with lumbar support are available in their workplaces.
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15. Fig. 25-3 Configuration of the spine in a seated dental assistant.
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16. Reaching, Twisting, and Stretching
Frequent reaching, twisting, and working with the arms in awkward positions can cause strains and sprains.
Extreme stretching of muscles or ligaments causes strains, and sprains usually involve a sudden twisting or wrenching of a joint with resulting stretching or tearing of ligaments.
Shoulder problems can be caused by repeatedly reaching behind the body for instruments or supplies.
(Cont’d)
Remind the student that reaching, twisting, and stretching for equipment or supplies can greatly increase the chance of an injury.
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17. Reaching, Twisting, and Stretching
(Cont’d)
Keep the air-water syringe, handpiece, saliva ejector, and high-volume oral evacuator within a “normal horizontal reach.”
Keep the operatory light within a safe “maximum vertical reach.”
Other supplies used less frequently should be placed within the “maximum horizontal reach.”
Reaching behind your back and lifting can cause shoulder injury. When turning is necessary, rotate the chair rather than twisting your body.
Proper motion movement can prevent twisting and stretching injuries.
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18. Repetition and Force
Repetitive motion, overflexion, and extension of the wrist can significantly increase the risk of cumulative trauma disorders (CDTs), particularly when the task requires force.
To help prevent CDTs, periodic breaks and alternation of difficult procedures with less stressful procedures are recommended. One common CTD is CTS.
The estimated cost of cumulative trauma disorders is $25 billion to $40 billion dollars a year.
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19. Fig Small pieces of equipment should be placed in a position that does not require twisting or bending.
Proper storage of small equipment can limit the potential for injuries from twisting or bending.
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20. Carpal Tunnel Syndrome
The carpal tunnel is an anatomic area of the hand/wrist.
With improper motion, the tendons swell, exerting pressure on the median nerve.
The first symptoms of CTS is a painful tingling in one or both hands.
Decreased ability and power to squeeze objects or make a tight fist may follow.
In advanced cases the thenar muscle (located at the base of the thumb) may weaken, causing a feeling of decreased strength in the hand grip.
(Cont’d)
Inform the students that braces can be worn that will splint the tendon, preventing movement. This will allow the tendon to rest and recover from the stress of repetitive motion.
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21. Fig Repetitive stress on the bend in the wrist over long periods can lead to carpal tendon injury. This dental assistant should periodically change her grasp on the oral evacuator to straighten out her wrist. She should also use the back support on her chair.
Ask the class to suggest a better technique or use of equipment to prevent long-term injury to the carpal tendon.
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22. Fig. 25-6 A, Cross-section of the wrist
Fig A, Cross-section of the wrist. B, Schematic view of the carpal tunnel. (From Thibodeau GA: Anatomy and physiology, ed 4, St Louis, 2002, Mosby.)
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23. Carpal Tunnel Syndrome
(Cont’d)
Other repetitive hand and wrist movements such as knitting, gardening, and keyboard use can also cause CTS.
The use of ambidextrous gloves (gloves that are worn on either hand) can exert excessive tension on the hypothenar eminence (the fleshy elevation of the palm side of the hand) by forcing the hand to work against the vertical alignment of the glove form.
Right-left gloves that are properly sized support the hand in a natural position, which properly positions the thumb, index finger, and middle finger.
Remind students of the dangers of repetitive hand and wrist movements.
Encourage the proper use of equipment to minimize the stress on the tendon.
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24. Fig. 25-7 The arrow indicates the location of the thenar eminence on a gloved hand.
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25. Chapter 25 Lesson 25.3
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26. Learning Objectives
Demonstrate exercises that can reduce muscle fatigue and strengthen muscles.
Demonstrate exercises to reduce eyestrain.
Demonstrate exercises to reduce neck strain.
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27. Body-Strengthening Exercises
Stretching and strengthening the muscles that support the back and neck and those used in the forearm, wrist, and hand will help them remain strong and healthy.
You can engage in stretching periodically throughout the workday.
Before beginning any exercise program, you should check with your physician, particularly if you experience pain with any of the movements.
Remind students of the importance of body-strengthening exercises to prevent injury.
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28. Hand Exercises
Resting the hands frequently is believed to be one of the most important factors in preventing CTS.
Use the following exercises to stretch and relax the muscles in the hand.
Demonstrate the hand exercises to the class.
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29. Fig A and B, Slowly open and close your hands from a completely open position to a completely closed position, ending with your fingers tucked into your palms. A B
Discuss the benefits of this exercise.
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30. Fig. 25-8 C, Press the palms of your hands together and then relax them.
What part of the body benefits from this exercise?
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31. Fig. 25-8 D, Gently pull and relax each finger on each hand separately.
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32. Fig. 25-8 E, Cross the wrists and gently stretch and relax.
What repetitive motions in the dental office might cause pain in the wrists?
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33. Eye Exercises
To relieve eyestrain caused by focusing intensely at one depth of vision for long periods, look up from the task and focus your eyes at a distance for approximately 20 seconds.
Practice this frequently throughout the day to use your full range of vision and lessen eyestrain.
Have the class practice this exercise in class.
How frequently should this exercise be performed?
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34. Back Exercises
To relieve stresses on the back, neck, and shoulders, try the full back release.
Let the head roll forward slowly and allow the arms and head to fall between the knees; hold for a few seconds, then rise slowly by contracting the stomach muscles and rolling up. Bring the head up last.
Can these exercises be performed in the work setting?
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35. Fig Full back release.
Demonstrate full back release exercises to the class.
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36. Neck Exercises
Try head rotations for neck stiffness. Head rotations involve tilting the head from right to left, as well as forward and backward, without forcing the motion beyond your range of comfort.
Demonstrate neck exercises to the class.
What might result if the motion is jerky or the head is tilted beyond a comfortable range?
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37. Shoulder Exercises
Shoulder-shrugging can be used to stretch shoulder muscles that may be stressed by holding oral evacuators, instruments, and telephone handsets. Pull the shoulders up toward the ears, then roll them backward and forward in a circular motion.
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38. Fig. 25-10 Shoulder-shrugging.
Demonstrate shoulder shrugging technique to the class.
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