Musculoskeletal Disorders
and Ergonomics in
Dentistry:
An Introduction
Pooya Daneshvar-MD
PhD candidate
Exercise therapy
USAF Dental Evaluation & Consultation Service
Musculoskeletal Disorders
(MSDs)

Include a group of conditions that
involve nerves, tendons, muscles,
and supporting structures such as
intervertebral discs
Severity of Symptoms
Mild periodic
Severe chronic &
debilitating conditions
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‫‪Ergonomics‬‬
‫=‬
‫‪MSDs‬‬
‫‪Musculoskeletal problems are the‬‬
‫‪problem and ergonomics is a‬‬
‫‪solution.‬‬
‫ارگونومی علم مهندس ی فاکتورهای انسانی است که هدفش‬
‫تطبیق دادن شغل با شاغل است و بالطبع راهکارهایی که بر‬
‫این اصول مبتنی هستند‪ ،‬مداخالت ارگونومیک نامیده‬
‫میشوند‪.‬‬
‫علم ارگونومی درحال حاضرپیشگیري ازآسیب هاي اسکلتی‪،‬‬
‫عضالنی شاغلین درصنایع و مشاغل پیچیده است‪.‬‬
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‫بهداشت حرفه اي دندانپزشكان‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫درحرفه دندانپزشکی همانند سایرمشاغل یک سري عوامل زیان آور‬
‫درمحیط کاروجود دارد که درصورت عدم رعایت موازین بهداشت‬
‫شغلی ‪ ،‬سالمتی شاغلین دراین حرفه را به خطرمی اندازند‪.‬‬
‫ارگونومی دردندانپزشکی برروي دو موضوع عمده تأکید دارد ‪:‬‬
‫فشارهاي فیزیکی و فشارهاي روحی روانی ‪.‬‬
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‫شيوع آسيبهاي شغلي عضالني اسكلتي در‬
‫دندانپزشكان‬
‫مطالعات انجام شده درحرفه دندانپزشکی نشان می دهد‬
‫دندانپزشکان بیش ازسایرشاغلین حرفه پزشکی درمعرض ابتال به‬
‫مشکالت اسکلتی و عضالنی قراردارند‪.‬‬
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‫شيوع‬


Studies indicate that back, neck, and
shoulder or arm pain is present in up
to 81% of dental operators.5
Back pain is the most common
complaint followed by neck pain and
shoulder pain
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‫علل بازنشستگي و از كارافتادگي زودرس‬
‫دندانپزشكان‬
‫نتایج انتشار یافته نشان می دهد اختالالت اسکلتی و عضالنی‬
‫‪%29.5‬‬
‫بیماري هاي قلبی و عروقی (‪)21.1‬و بیماري هاي سیستم عصبی‬
‫مرکزي(‪ ،)6.1‬تومورها(‪ )7.6‬درازکارافتادگی و بازنشستگی زودرس‬
‫دندانپزشکان مؤثرند‪.‬‬
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‫نتايج يك مطالعه ملي‬
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2-‫نتايج يك مطالعه ملي‬
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‫مطالعه دانشگاه پزشكي نيوكاسل‬




prevalence of general
musculoskeletal pain :64% and 93%.
The most prevalent regions for pain
in dentists :
the back (36.3-60.1%)
and neck (19.8-85%),
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‫مطالعه هندوستان(مطالعه گسترده)‬
‫فركانس بروز درد‪:‬‬
‫‪%7‬هميشه ‪ %83 ،‬دردهاي گاهگاهي‬
‫شدت بروز درد‪:‬‬
‫درد شديد كمر‪ %23.3‬و گردن‪%13.3‬‬
‫درد متوسط كمر‪ %67‬و گردن‪%33‬‬
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‫‪‬‬
‫‪‬‬
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‫آمار قرار گرفتن در معرض عوامل خطرساز‬
‫‪%100‬مجبور به انجام حركات چرخشي مكرر كمر‬
‫بيش از ‪%90‬خم كردن مكررگردن‪،‬شانه‪،‬كمريا آرنج‬
‫‪%83Finger pinch‬‬
‫مجبور به فاصله گرفتن مكرربيش از ‪ 20‬اينچ‪80%‬‬
‫رابطه معني دار بين تعداد بيمار روزانه و بروز دردها‬
‫رابطه معني دار بين قد دندانپزشك و بروز دردها‬
‫عدم وجود رابطه معني دار با‬
‫جنس‪،‬سن وحتي ساعات كار!!!!!!!!!!!‬
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‫جنس و بهداشت عمومي‬،‫تاثير سن‬

Yamalik[18] reported that age,
gender, and perceived general health
status are strongly associated with
chronic complaints and seeking
medical care. Elderly people, women,
and those who experience poor
general health also report more
chronic complaints
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‫بترسيد‬
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Types of MSDs

Neck and Shoulder
Disorders


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
Myofascial Pain
Disorder
Cervical Spondylolysis
Thoracic Outlet
Syndrome
Rotator Cuff
Tendinitis/Tears
Back Disorders
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Herniated Spinal Disc
Lower Back Pain
Sciatica

Hand and Wrist
Disorders

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DeQuervain’s Disease
Trigger Finger
Carpal Tunnel
Syndrome
Guyon’s Syndrome
Cubital Tunnel
Syndrome
Hand-Arm Vibration
Syndrome
Raynaud’s Phenomenon
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MSDs
Signs




Symptoms
Decreased range
of motion
Deformity
Decreased grip
strength
Loss of muscle
function

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
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

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Pain
Numbness
Tingling
Burning
Cramping
Stiffness
Mechanisms Leading to
Musculoskeletal Disorders (MSDs) in
Dentistry

Prolonged Static
Postures (PSPs):
Dentists frequently
assume static
postures. When the
human body is
subjected repeatedly
to PSPs, it can initiate
a series of events that
may result in pain,
injury or a careerending MSD.

Muscle Ischemia/Necrosis
and Imbalances: During
treatment, operators strive
to maintain a neutral,
balanced posture and find
themselves in sustained
awkward postures. These
postures often lead to
stressed shortened
muscles which can become
ischemic and painful,
exerting asymmetrical
forces that can cause
misalignment of the spinal
column
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Mechanisms Leading to Musculoskeletal
Disorders (MSDs) in Dentistry

Hypomobile Joints:
During periods of PSPs
or when joints are
restricted due to
muscle contractions,
synovial fluid
production is reduced
and joint hypomobility
may result.

Spinal Disk Herniation and
Degeneration: In
unsupported sitting,
pressure in the lumbar
spinal disks increases.
During forward flexion and
rotation, a position often
assumed by dental
operators, the pressure
increases further and
makes the structure
vulnerable to injury
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wow
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Contributing Factors for
Work-Related MSDs
(WMSD)

Routine exposure to:
 Forceful hand exertions
 Repetitive movements
 Fixed or awkward postures
 Vibrating tools
 Unassisted frequent or heavy lifting
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What Factors Contribute to
WMSDs?

Forceful hand exertions



Grasping small instruments for prolonged
periods
Forceful squeezing/release of instruments
Repetitive movements—e.g., scaling,
root planing, polishing
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What Factors Contribute to
WMSDs?

Fixed or awkward postures

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Neck, back, shoulder posture
Hand/wrist positions
Standing/sitting
Operatory organization
Patient positioning
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What Factors Contribute to
WMSDs?

Prolonged use of vibrating hand
tools—dental handpieces, laboratory
equipment
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Contributing Factors for
WMSDs


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A risk factor is not always a causation
factor
The level of risk depends on
 Length of time a worker is exposed
to these conditions
 How often they are exposed
 Level of exposure
Usually a combination of multiple risk
factors (vs. a single factor)
contributes to or causes a MSD
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Contributing Factors for
WMSDs

Do not focus solely on the workplace

Risk factors may be experienced
during non-occupational activities
(e.g., certain sports, exercising,
working with computers, needlework,
playing musical instruments)
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Contributing Factors for
WMSDs



Not everyone exposed to any or all of
the risk factors will develop a MSD
Individuals do not respond to them in
the same way
Predisposing factors such as age,
arthritis, renal disease, hormonal
imbalances, diabetes, and
hypothyroidism may play a role
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Neck and Shoulder
Disorders

Risk factors associated with dentistry
Prolonged static neck flexion and
shoulder abduction or flexion
 Lack of upper-extremity support
 Inadequate work breaks

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Neck and Shoulder
Disorders

Dental health-care personnel (DHCP)
commonly assume awkward work
postures

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To obtain better views of the intraoral
cavity
To provide a more comfortable position for
the patient
To coordinate their position relative to the
dentist or assistant
While operating equipment and reaching
for instruments and supplies
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Neck and Shoulder
Disorders

Examples




Myofascial Pain Disorder
Cervical Spondylolysis
Thoracic Outlet Syndrome
Rotator Cuff Tendinitis/Tears
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Neck and Shoulder Disorders
Myofascial Pain Disorder



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Pain and tenderness in the neck,
shoulder, arm muscles
Painful trigger points—may twitch
upon touch or massage
Restricted range of motion
Possible causes: overloaded
neck/shoulder muscles
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Neck and Shoulder
Disorders
Cervical Spondylosis
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Intermittent/chronic neck and shoulder
pain or stiffness
Headache
Hand and arm pain, numbness, tingling,
clumsiness may occur
Possible causes: age-related spinal disc
degeneration leading to nerve
compression and spinal cord damage;
arthritis
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Neck and Shoulder
Disorders
Thoracic Outlet Syndrome
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Pain in the shoulder, arm or hand (can be
all three)
Numbness, tingling of fingers
Muscle weakness/fatigue
Cold arm or hand
Possible causes: compressed nerves or
blood vessels passing into arms; trauma;
slouching forward or dropping shoulders
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Neck and Shoulder
Disorders
Rotator Cuff Tendinitis/Tears


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Pain and stiffness in the shoulder
associated with backward and
upward arm movements
Weakness of rotator cuff muscles
Possible causes: swelling or tearing
of rotator cuff soft tissue; shoulder
joint bone spurs/abnormalities; poor
shoulder posture
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Hand and Wrist Disorders

Risk factors associated with dentistry
 Chronic repetitive movements of the
hand and wrist
 Abnormal or awkward positions of the
wrist
 Mechanical stresses to digital nerves
such as sustained grasps on
instrument handles
 Forceful work
 Extended use of vibratory instruments
 Inadequate work breaks
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Hand and Wrist Disorders
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Examples
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DeQuervain’s Disease
Trigger Finger
Carpal Tunnel Syndrome
Guyon’s Syndrome
Cubital Tunnel Syndrome
Hand-Arm Vibration Syndrome
Raynaud’s Phenomenon
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Hand and Wrist Disorders
DeQuervain’s Disease
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Pain in thumb and wrist area when
grasping, pinching, twisting
Swelling in thumb area
Decreased range of motion of thumb
with pain
Possible causes: synovial sheath
swelling; thickening of tendons at
base of thumb; repeated trauma or
twisting hand/wrist motions
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Hand and Wrist Disorders
Trigger Finger (Tenosynovitis)
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Pain during movement that place
tendons in tension
Warmth, swelling, tenderness of the
tendon when palpated
Possible causes: sustained, forceful
powerful grip and/or repetitive
motion
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Hand and Wrist Disorders
Carpal Tunnel Syndrome
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Hand or finger numbness, pain, tingling,
burning, clumsiness
Eventual muscle weakness and atrophy
Symptoms often worse with increased activity
Pain or tingling that awakens the patient at
night with relief via shaking/massaging the
hand is considered a hallmark symptom for
diagnosis
Possible causes: compressed median nerve in
wrist via trauma, forceful exertion, repetitive
and awkward movements that deviate from
near-neutral positions
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Hand and Wrist Disorders
Carpal Tunnel Syndrome
All hand pain does not mean carpal
tunnel syndrome
 DHCP do not appear to be at
greater risk compared to the
general population for developing
carpal tunnel syndrome

Hamann C, Werner RA, Franzblau A, Rodgers PA, Siew C, Gruninger S.
Prevalence of carpal tunnel syndrome and median mononeuropathy
among dentists. J Am Dent Assoc 2001;132:163-170.
Werner RA, Hamann C, Franzblau A, Rodgers PA. Prevalence of carpal
tunnel syndrome and upper extremity tendinitis among dental
hygienists. J Dent Hyg 2002;76:126-132.
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Hand and Wrist Disorders
Guyon’s Syndrome
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Pain, weakness, numbness, tingling,
burning in the little finger and part of the
ring finger
Symptoms may worsen at night or early
morning
Possible causes: compressed ulnar nerve
in Guyon’s canal at the base of the palm;
repetitive wrist flexing; excessive pressure
on palm/base of hand
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Hand and Wrist Disorders
Cubital Tunnel Syndrome
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Pain, numbness, tingling and impaired
sense of touch in the little and ring fingers,
side and back of hand
Loss of fine control
Reduced grip strength
Possible causes: compressed ulnar nerve
in elbow due to trauma or repeated use;
prolonged use of elbow while flexed
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Hand and Wrist Disorders
Hand-Arm Vibration Syndrome
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Intermittent or chronic finger and hand
numbness and blanching
Reduced dexterity, grip strength, and
sensation
Greater sensitivity to cold
Possible causes: vibrations may injure
nerves leading to decreased blood flow
and lower oxygen supply to surrounding
tissues
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Hand and Wrist Disorders
Raynaud’s Phenomenon
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Intermittent spasm of finger and toe blood
vessels causing blanching, numbness, and
pain
Increased sensitivity to cold temperatures
Possible causes: carpal tunnel syndrome,
connective tissue diseases, repeated
vibration or use of tools that vibrate
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Back Disorders
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Risk factors associated with dentistry
 Awkward posture
Examples
 Herniated Spinal Disc
 Lower Back Pain
 Sciatica
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Back Disorders
Herniated Spinal Disc
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Back and leg numbness, tingling, pain,
weakness
Worsens with coughing, sneezing,
sitting, driving, bending forward
Possible causes: bulging or fragmenting
of intervertebral discs into spinal canal
compressing and irritating spinal
nerves; excessive heavy lifting without
adequate rest
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Back Disorders
Lower Back Pain
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Pain
Stiffness in lower spine and
surrounding tissues
Possible causes: heavy lifting and
forceful movements; whole body
vibration; bending/twisting;
awkward static postures
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Back Disorders
Sciatica
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Pain from lower back or hip radiating
to the buttocks and legs
Leg weakness, numbness, or tingling
Possible causes: prolapsed
intervertebral disc pressuring the
sciatic nerve; worsened with
prolonged sitting or excessive
bending/lifting
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Treatment and Management of
MSDs

Obtain an accurate diagnosis from a
qualified health-care provider
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Early intervention is key
Self-diagnosis is not recommended

MSD origins are complex with a broad
range of symptoms
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Treatment and Management of
MSDs
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Diagnostic tests may include physical
exams, provocative tests, and
electromyography
Treatment may range from pain-relief
medications and rest to surgery, and
ergonomic interventions both at work
and home
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What is Ergonomics?
“Ergo” means work
“Nomos” means natural laws or systems


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Ergonomics is the science of work
Ergonomics is much broader than preventing
work-related musculoskeletal disorders
Ergonomics plays an important role in
preventing injury and illness
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What is Ergonomics?

An applied science
concerned with
designing and
arranging things
people use so that
the people and
things interact
most efficiently
and safely
Job Demands
Worker
Capabilities
"fitting the job task to the
person performing the job"
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Consequences of Poor
Design
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Fatigue
Discomfort
Illness/Injury
Absenteeism
Errors
Lower productivity
Customer dissatisfaction
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Ergonomic Design Goals
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Enhanced
performance by
eliminating
unnecessary effort
Reduce
opportunities for
overexertion injury
Improve comfort by
curtailing the
development of
fatigue
Job Demands
Worker
Capabilities
"fitting the job task to the
person performing the job"
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Goals

Improved
 Productivity
 Safety
 Health
 Job Satisfaction
Job Demands
Worker
Capabilities
"fitting the job task to the
person performing the job"
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Dental Ergonomic Stressors
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Sustained/awkward postures
Repetitive tasks
Forceful hand exertions
Vibrating operational devices
Time pressure from a fixed schedule
Coping with patient anxieties
Precision required with work
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Ergonomic Risk Factors in
Dentistry

Neck and Shoulder: Repetitive neck
movements and continuous arm and
hand movements affecting the neck
and shoulder demonstrate significant
associations with neck MSDs.
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Incorrect & Correct
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‫محدوه ممنوع‬..‫محدوده خطر‬.. ‫محدوده مجاز‬
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Ergonomic Risk Factors in
Dentistry

Wrist and Hand: Carpal Tunnel
syndrome (CTS) has been associated
with both repetitive work and
forceful work. Symptoms can appear
from any activity causing prolonged
increased (passive or active)
pressure in the carpal cana
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Incorrect & Correct
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Ergonomic Risk Factors in
Dentistry
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Psychosocial Factors: Dentists with
work-related MSDs show a
significant tendency to be more
dissatisfied at work and to be more
burdened by anxiety, experiencing
poorer psychosomatic health and
feeling less confident with their
futures
Indian Health Service: Ergonomics Recommendations for Dental Programs.
http://www.cdc.gov/niosh/topics/ergonomics
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Ergonomic Risk Factors in
Dentistry
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Low Back Pain: Low-back discomfort has
been associated with dental work in
numerous studies. Good posture
correlated negatively with back pain and
dentists who sat 80 percent to 100 percent
of the day reported more frequent lowerback pain, than those that do not sit as
often (Shugars et al., 1987
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Prevention strategies
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‫دامنه حركت‬
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Preventing Ergonomic
Injuries
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Identify risk factors
Educate DHCP about ergonomic
hazards and preventing MSDs
Identify symptoms as soon as they
become apparent
Intervene quickly
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Preventing Ergonomic
Injuries
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Change human behavior
Consider ergonomic features for dental
equipment (e.g., patient chairs, operator
stools, hand/foot controls, instruments)
when purchasing new equipment
Modify working conditions to achieve
optimal body posture
Achieve optimum access, visibility,
comfort, and control at all times
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Workplace Intervention
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“Make the job fit the person” not vice
versa
Minimize extreme joint position
 Keep wrist in neutral (i.e., straight)
position
 Keep joints held at midpoint of range
of motion
Reduce the use of excess force
Reduce highly repetitive movement
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Applying Ergonomics to Dentistry
Provide Sufficient Space

Awkward bending, twisting, and
reaching places stress on the
musculoskeletal system and can
lead to discomfort
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Applying Ergonomics to Dentistry
Provide Sufficient Space
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Permanently place equipment used in
every clinical procedure within
comfortable reach (within 20 inches of
the front of the body)
Use mobile carts for less commonly
used equipment
 Allows convenient positioning when
required
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Applying Ergonomics to Dentistry
Provide Sufficient Space

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Provide a clear line of sight to the oral
cavity and all required equipment
Maintain a neutral, balanced position—
position of an appendage when it is
neither moved away from nor directed
toward the body’s midline; it also
should not be laterally turned or
twisted
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Applying Ergonomics to Dentistry
Accommodate Individual Preferences
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Individuals vary in size, shape, training,
and experience
Ensure equipment and work areas
allow flexibility; examples may include:
 Allows right- or left-handed use
 Allows different working postures
 Provides a choice in methods used
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Reduce Physical Effort

Avoid bent or
unnatural postures

Ideally, equipment
should allow work in
a relaxed and wellbalanced position


DHCP should adjust
equipment to the
appropriate height
Position the patient
to allow easy access
from the desired
position
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Reduce Physical Effort


Use reasonable operating forces and minimal
repetitions reduces overall physical effort
required by a task
Minimize sustained effort
 Brief but frequent rest pauses can
minimize fatigue and enhance productivity
 Try to incorporate a variety of different
activities to shift musculoskeletal demands
from one part of the body to another
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Instrument Design


Goal: reduce force exertion; maintain
hand/wrist in neutral position (no
wrist bend)
Considerations
 Overall shape/size
 Handle shape/size
 Weight
 Balance
 Maneuverability
 Ease of operation
 Ease of maintenance
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Hand Instruments

When selecting instruments, look for
 Hollow or resin handles
 Round, textured/grooves, or
compressible handles
 Carbon-steel construction
 Color-coding may make instrument
identification easier
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Dental Handpieces

When selecting handpieces, look for








Lightweight, balanced models
Sufficient power
Built-in light sources
Angled vs. straight-shank
Pliable, lightweight hoses (extra
length adds weight)
Swivel mechanisms
Easy activation
Easy maintenance
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Syringes and Dispenser

When selecting look for
 Adequate lumen size
 Ease in cleaning
 Textured/grooved handles
 Easy activation and placement
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Lighting




Goal: produce even, shadowfree, color-corrected
illumination concentrated on
operating field
Overhead light switch readily
accessible
Hand mirrors can be used to
provide light intraorally
Fiberoptics for handpieces add
concentrated lighting to the
operating field
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Magnification


Goal: improve neck posture; provide
clearer vision
When selecting magnification systems
consider






Working distance
Depth of field
Declination angle
Convergence angle
Magnification factor
Lighting needs
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Operator Chair


Goal: promote mobility and patient access;
accommodate different body sizes
Look for:
 Stability
 Lumbar support
 Hands-free seat height
adjustment
 Fully adjustable
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Patient Chair


Goal: promote patient comfort; maximize
patient access
Look for:
 Stability
 Pivoting or drop-down
arm rests (for patient
ingress/egress)
 Fully adjustable head rest
 Hands-free operation
USAF Dental Evaluation & Consultation Service
‫صندلي دنداپزشك‬
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Posture/Positioning


Goal: avoid static and/or awkward
positions
Potential strategies
 Position patient so that operator’s
elbows are elevated no more than
30 degrees
 Adjust patient chair when accessing
different quadrants
 Alternate between standing and
sitting
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Work Practices


Goal: maintain neutral posture; reduce
force requirements
Potential strategies
 Ensure instruments are sharpened,
well-maintained
 Use automatic handpieces instead of
manual instruments wherever possible
 Use full-arm strokes rather than wrist
strokes
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Scheduling


Goal: provide sufficient recovery time to
avoid muscular fatigue
Potential strategies
 Increase treatment time for more
difficult patients
 Alternate heavy and light calculus
patients within a schedule
 Vary procedures within the same
appointment
 Shorten patient’s recall interval
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Personal Protective Equipment


Glasses
 Lightweight, clean, well-fitted
 Magnifying lenses and head lamps
are encouraged
Clothing
 Fit loosely, lightweight, pliable
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Personal Protective Equipment

Gloves
 Be of proper size, lightweight, and pliable
 Should fit hands and fingers snugly
 Should not fit tightly across wrist/forearm
USAF Dental Evaluation & Consultation Service
Applying Ergonomics to Dentistry
Personal Protective Equipment

Gloves
 Ambidextrous (i.e., non-hand specific): exert
more force than fitted gloves across palmar
region of hand and may exacerbate
symptoms of carpal tunnel syndrome
 Hand-specific (i.e., right vs left) is
recommended
 Fit better
 Place less force on hand
USAF Dental Evaluation & Consultation Service
Eye protection
USAF Dental Evaluation & Consultation Service
‫مراقب خودتون باشيد‬
USAF Dental Evaluation & Consultation Service
‫ورزشهاي كششي‬
USAF Dental Evaluation & Consultation Service
‫ورزشهاي كششي‬
USAF Dental Evaluation & Consultation Service
‫ورزشهاي كششي‬
USAF Dental Evaluation & Consultation Service
‫ورزشهاي كششي‬
USAF Dental Evaluation & Consultation Service
‫حركات اصالحي‬
USAF Dental Evaluation & Consultation Service
‫حركات اصالحي‬
USAF Dental Evaluation & Consultation Service
‫حركات اصالحي‬
USAF Dental Evaluation & Consultation Service
‫حركات اصالحي‬


Shoulder Exercises:
Raise shoulders up
towards the ears
and rotate first in
clockwise direction
and then in anticlockwise direction
USAF Dental Evaluation & Consultation Service
References

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Ergonomics and Disability Support Advisory
Committee (EDSAC) to the Council on Dental
Practice (CDP). An introduction to ergonomics: risk
factors, MSDs, approaches and interventions.
American Dental Association;2004.
Grant KA. Ergonomics: is it optional? PowerPoint
presentation.
Murphy DC. Ergonomics and the Dental Care
Worker. American Public Health Association, United
Book Press, Washington, DC;1998.
NIOSH. Work-related musculoskeletal disorders.
1997.
SmartTec. Musculoskeletal disorders: their
symptoms and possible causes. Smartpractice;2002.
USAF Dental Evaluation & Consultation Service
‫شاد و پيروز و تندرست باشيد‬
USAF Dental Evaluation & Consultation Service