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ERGONOMICS IN DENTAL PRACTICE

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 International Journal of Dental and Health Sciences
Review Article Volume 01,Issue 01

ERGONOMICS IN DENTAL PRACTICE

Aasim Farooq Shah1, Pradeep Tangade2, Manu Batra3, Soumik Kabasi4
1. Post Graduate Student, Department Of Public Health Dentistry, Kothiwal Dental College &
Research Centre, Kanth Road, Moradabad, Uttar Pradesh, India
2.Professor and Head, Department Of Public Health Dentistry, Kothiwal Dental College & Research
Centre, Kanth Road, Moradabad-244001, Uttar Pradesh, India.
3. Assistant Professor, Department Of Public Health Dentistry, Teerthanker Mahaveer Dental College
and Research Centre, Moradabad, India.
4. Assistant Professor , Department Of Public Health Dentistry, Institute Of Dental Sciences and
Hospital, Bhubaneshwar, Odisha, India.

ABSTRACT:

Ergonomics is the science of fitting the task to human capabilities and limitation in order to
improve work place safety and productivity. Dental profession is not immune from MSDs or
cumulative trauma disorders (CTD). Risk factors for work related MSDs with specific
reference to dentistry include stress, poor flexibility, improper positioning, infrequent
breaks, repetitive movements, weak postural muscles, prolonged awkward postures and
improper adjustment of equipment. Proper ergonomic design is necessary to prevent
repetitive strain injuries (RSJ), which can develop over time and can lead to long term
disability. This article discusses the important issues of postures and offers different
methods to ergonomize the dental operatory so as to work with comfort, efficiency and
ease.

Key words: Ergonomics, MSD, CTD, Prolonged static postures (PSP).

INTRODUCTION:
Literature suggests that the prevalence
Dentistry is a social interaction between of skeletal or muscular pain in dentists,
helper and recipient in their limited job dental hygienists and dental students
setting and with personal characteristics. ranges from 93% to 64%. The most
A healthy dentist is one of the most prevalent regions for pain in dentists
important component in a successful have been shown to be the back (36.3% -
dental practice. It is estimated that more 60.1%) and neck (19.5- 80%).[2] Dentists
than half of practitioners have some kind and dental hygienists are at risk for work
of painful musculoskeletal disorder that related musculoskeletal disorders
is work related. Studies by Gorter et al, in compared to the general population. The
2000 show that one out of ten dentist’s most frequent injuries occur in the spine
reports having poor general health and (neck and back), shoulders, elbows and
three out of ten dentists report having hands. Although the causes of any
poor physical state. [1]

*Corresponding Author Address: Dr. Aasim Farooq Shah Department Of Public Health Dentistry, Kothiwal Dental
College & Research Centre, Kanth Road, Moradabad-244001,E-Mail: dr_aasimshah@yahoo.com
 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

particular case of a MSD are exceedingly The world health organization defines
difficult to identify with complete MSD as “a disorder of the muscles,
accuracy, certain risk factors are typically tendons, joints, intervertebral discs,
discussed in the field of ergonomic
peripheral nerves and vascular system,
studies. The primary occupational risk
factors for MSDs discussed in the not directly resulting from an acute or
literature include: instantaneous event hut installing
gradually and chronically.” Cumulative
trauma disorders (CTDs) are health
disorders arising from repeated
• Repetition biomechanical stress to the hands, wrist,
elbows, shoulders, neck and back. [9]
• Force

• Mechanical stresses Most common CTDs are carpal tunnel

syndrome and Low back pain.” The
• Posture common signs, symptoms and risk
factors of MSD are:
• Vibration

• Cold temperature
Some Symptoms of MSDs:
• Extrinsic stress [3, 4, 5, 6, 7]

Recently, “Ergonomics” has become a  Excessive fatigue in the shoulders and

popular term. The term has been used neck
with most professions but increasingly in
the dental profession. The word  Tingling, burning sensation in arms
‘Ergonomics’ was derived from the Greek
word: Ergo’ which means work; and  Weak grip. cramping of hands
‘nomos’ meaning natural laws. It is the
science of fitting the job settings  Numbness in fingers and hands
conducive to the worker. In simple
terminology, Ergonomics is a way to work  Clumsiness and dropping of objects
smarter- nut harder, by designing tools,
equipment, work stations and tasks to fit  Hypersensitivity in hands and fingers
the job to the worker- NOT the worker to
the job. Proper ergonomic design is Signs of MSDs:
necessary to prevent repetitive strain
injuries (RSI), which can develop over
 Decreased range of motion
time and can lead to long term disability.
[8]
 Loss of normal sensation
MUSCULOSKELETAL DISORDERS:
 Decreased grip strength

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 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

 Loss of normal movement Prolonged Static Postures (PSPs): When

the human body is subjected repeatedly
 Loss of co-ordination to PSPs, it can initiate a series of events
that may result in pain, injury or a career-
Some Risk Factors for MSDs :[10] ending MSD.

 Repetition Muscle Ischemia/Necrosis and

Imbalances: During treatment, operators
 Forceful exertions strive to maintain a neutral, balanced
posture and find themselves in sustained
 Awkward postures awkward postures. These postures often
lead to stressed and shortened muscles
 Contact stress which can become ischemic and painful,
exerting asymmetrical forces that can
 Vibration cause misalignment of the spinal column
(Al Wazzan et al, 2001). [11]
 Poorly designed equipment
workstation Hypo-mobile Joints: During periods of
PSPs or when joints are restricted due to
 Improper work habits muscle contractions, synovial fluid
production is reduced and joint hypo
 Genetics mobility may result.

 Medical conditions Spinal Disc Herniation and

Degeneration:In unsupported sitting,
 Poor fitness level pressure in the lumbar spinal discs
increases. During forward flexion and
 Physical/mental stress rotation, the pressure increases further
and makes the spine & disc vulnerable to
 Lack of rest/recovery injury (Al Wazzan, et al 2001). [11]

 Poor nutrition Neck and Shoulder Injury: Repetitive neck

movements and continuous arm and hand
 Environmental factors movements affecting the neck and
shoulder demonstrate significant
 Poor lighting associations with neck MSDs.

With specific reference to dentistry, the Carpal-Tunnel Syndrome (CTS): It has

risk factors include: stress, poor flexibility, been associated with both repetitive work
improper positioning, in frequent breaks, and forceful work. Symptoms can appear
repetitive movements, weak postural from any activity causing prolonged and
muscles, prolonged awkward postures increased pressure (passive or active) in
and improper adjustment of equipment. the carpal canal (Shugars et al, 1987). [12]

MECHANISMS MSDS IN DENTISTRY:

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 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

Low Back Pain: Low back discomfort has The best way to reduce pressure in the
been associated with dental work in back is to be in a standing position.
numerous studies. However, there are times when the
dentist needs to sit. When sitting the main
Psychosocial Factors:Dentists with work- part of the body weight is transferred to
related MSDs show a significant tendency the scat. Some weight is also transferred
to be more dissatisfied at work. They are to the floor, back rest and arm rests.
burdened by anxiety, poor psychosomatic Where the weight is transferred is the key
health and thus feel less confident with to a good seat design. [14]
their future (Shugars et al, 1987). [12]
When working in sitting postures a chair is
SITTING POSTURE: required to support the seat and back. In
this situation one should alternate active
Human spine has four natural curves; and passive sitting postures. The active
cervical lordosis, thoracic kyphosis, posture could be defined as the correct
lumbar lordosis and sacral kyphosis (Fig: body posture that is maintained by the
1). When sitting unsupported frequent muscles of the back, the back being
posture in dentistry the lumbar lordosis leaned forward. This posture cannot be
flattens. The bony infrastructure provides maintained for a very long time. The
little support to the spine, which now is passive posture is (he one in which the
hanging on the muscles, ligaments and back is sustained by the dentists’ back of
connective tissue at the back of the spine, the chair. [14]
causing tension in these structures.
lschemia can ensue, leading to low back Parameters of the correct working
strain and trigger points. Maintaining the postures’ [15] (Fig: 3)
cervical lordosis in the proper position is
equally important (Fig. 2). 1. The sitting posture is upright and
symmetrical.
Forward-head postures are common
among dentists, due to years of poor 2. The shoulders hanging down relaxed
posture involving holding the neck and with the upper arms beside the upper
head in an unbalanced forward position to body.
gain better visibility during treatment. In
this posture, the vertebrae no longer can 3. The forearms have been lightly
support the spine properly, and the elevated.
muscles of the cervical and upper thoracic
spine must contract constantly to support 4. The angle between lower and upper
the weight of the head in the forward legs is approx. 105-110.
posture. This can result in a pain pattern,
which often is referred to as tension neck 5. The legs are slightly apart, making an
syndrome. This syndrome can cause angle of between 30-45°.
headaches and chronic pain in the neck,
shoulders and inter-scapular muscles, and 6. The patient’s head is appropriately
it occasionally can radiate pain into the rotated in 3 directions.
arms. [13]

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 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

7. The light beam of the dental operating The doctor is now halfway between
light is as parallel as possible to the standing and sitting, so low back pressure
viewing. is even less than when seated in
traditional operator chairs.
8. The sitting location, between 09.00-
12.00 o’clock, for left-handed people Lumbar Support of the Chair: Must be
03.00- 12.00. used as much as possible by adjusting it
forward to contact your back.
9. The soles should he on the floor.
Avoid Static Postures: Dentists should
10. The patient’s head is rotated and the vary their work positions as often as
sitting location adjusted. possible to shift the workload from one
group of muscles to another.
11. Instruments held in 3 supporting
points. ALLERNATE BETWEEN STANDING AND
SITTING [10,16]
12. The upper part of the body should be
perpendicular on the chair forward Standing uses different muscle groups
movements should be made without than does sitting; therefore, alternating
curving the spine. between the two positions lets one
group of muscles rest, while the
13. The head could bend 20°-25°. workload is shifted to another group of
muscles Alternating between standing
14. The arms should be close to the body. and sitting also can he an effective tool in
preventing injuries.

Reposition the Feet: Subtle changes in

POSTURAL AWARENESS foot position can shift the workload from
TECHNIQUES [2,14, ] one group of low back muscles to
another, allowing the overworked tissues
Maintain the low back curve: This
to be replenished with nutrients.
facilitates proper posture and reduces
pressure on disks and muscles. The Position Patients al the Proper Height: A
following practices can help maintain the common mistake among dentists is
low back curve: positioning patients too high. This causes
elevation of the shoulders and abduction
Tilted Seat Plan: It opens the hip angle
of the arms, leading to prolonged static
by 110 degrees. Retrofit a non-tilting seat
muscular tension in the neck and
such as commercially available Fit—sit
shoulders. Operators should take the
ergonomic cushion for accomplishing
time to position their patients properly
this.
for mandibular and maxillary procedures.
Generally, patients should be placed in a
Saddle Stools: Consider using saddle-
semi supine position for mandibular
style operator stool that promotes the
procedures and a supine position for
natural low back curve by increasing the
maxillary procedures. Sit Close to the
hip angle to approximately 130 degree. It
Patient and position knees under the
is ideal for confined operatory spaces.
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 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

patients chair if possible. This can be Selection of Instruments: Tool

facilitated by tilting the scat and using instrument design should be such that it
patient chairs that have thin upper hacks reduces forceful exertion and maintains
and headrests. hand wrist in neutral posture.

Adjust the Chair: So your hips are slightly While using hand instruments look for:
higher than your knees and distribute
your weight evenly by placing your feet 1. Hollow or resin handles.
firmly on the floor. The forward edge of
the chair should not compress the backs 2. Round, Knurled or compressible
of your thighs. Sit close to tile patient and handles.
position knees under the patient’s chair if
possible. This can be facilitated by tilting 3. Carbon steel construction (for
the scat and using patient chairs that instruments with sharp edges).
have thin upper backs and headrests.
While using automated instruments look
Adjust Armrests: Which are designed to for:
decrease neck and shoulder fatigue and
strain, to support elbows in the neutral 1. Light weight, balanced models
shoulder position. (cordless preferred).

Avoid Twisting: When possible, dentists 2. Sufficient power.

should position instruments within easy
reach. Repeated unilateral twisting in 3. Built in light sources.
one direction may result in muscle
4. Angled vs. straight shank.
imbalances or structural tissue damage.
Leading to low back pain.
5. Pliable, light weight hoses.
MSD PREVENTION STRATEGIES
[17, 18, 19] 6. Easy activation.

7. Swivel mechanisms.
Use Magnification:Magnification enables
operators to maintain a greater working
Exercise: It is important to stabilize the
distance and position patients at the
low back curve by contracting the
proper height, with the shoulders relaxed
transverse abdominal muscles. To do this
and the forearms approximately parallel
while sitting, sit tall with a slight curve in
with the floor. Operating telescopes or
the low back, exhale, pull your navel
loupes arc available with flip-up or
toward the spine without letting the
through-the-lens designs. Working in
curve flatten. Continue breathing while
postures with greater than 20 degrees of
holding the contraction for one breath
neck flexion have been associated with
cycle. Repeat five times. Strive to
increased neck pain. The declination
maintain this stabilization regularly
angle of the scopes should allow you to
throughout the workday.
maintain less than 20 degrees of neck
flexion Chair-side Directional Stretching:Having
operators take frequent breaks and
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 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

reverse their positions is integral in an • Vary procedures within the same

effective injury prevention program. appointment.
Directional stretches can he performed in
or out of the operatory and can be • Alternate tough and easy patients.
incorporated into a daily routine that
facilitates balanced musculoskeletal • Shorten patient’s recall interval.
health. Directional stretching involves a
rotation, side-bending or extension Goals of ergonomics in any work place
component that generally is in the should include” [19]
opposite direction of that in which the
operator frequently works (Fig. 4). Figure 1. Reducing the risk of CTD.
5 shows various hand exercises to be
performed to reduce carpel tunnel 2. Increasing productivity.
syndrome (Fig 5). This strategy addresses
3. Increasing safety.
the muscle imbalances that tend to
develop. Frequent stretching breaks
4. Improving the quality of work.
address the detrimental physiological
changes that can develop while working 5. Decreasing fatigue and errors.
in optimal or awkward prolonged static
postures. MSD Prevention Methods” [20]
Micro breaks: To prevent injury from I. Adopting a correct working posture.
occurring to muscles and other tissues,
the operator should allow for rest 2. Use of adequate light.
periods to replenish and nourish the
stressed structures. In a study on the 3. Good planning of dental care sessions.
efficacy of microbreaks during the
workday, Morris and colleague found 4. Alternative planning of long and short
that by complying with regularly sessions.
Scheduled microbreaks. The subjects had
less discomfort and that the addition of 5. Alternating the body postures sitting
30 second microbreaks showed no and upright.
detrimental effect on worker
[17, 19] 6. Having short breaks after each care
productivity.
session and long coffee or lunch breaks,
Weight Control: For each additional 10 the sink should be installed at distance.
pounds of weight you carry, 100 pounds
of force is generated to the low back. 7. The working day should not be longer
than 7 hours.
Scheduling:Goal would be to provide
sufficient recovery time for the doctor 8. Every 6 weeks a journey should be
and the staff to avoid chronic muscle planned,
fatigue.

Potential Strategies

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 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

9. Sports activities should be practiced for problem can be managed or alleviated

about 45 minutes three times a week. effectively using a multifaceted approach
that includes preventive education,
CONCLUSION: postural and positioning strategies,
proper selection and use of ergonomic
Work-related pain is common among equipment and frequent breaks with
dental professionals. The development of stretching arid postural strengthening
four-handed operatory techniques has techniques. This represents a paradigm
made delivery of dental care more shift for daily dental practice. It is
efficient and productive: however, it also important that dentistry incorporate
has contributed to an increase in these strategies into practice to facilitate
prolonged static postures among balanced musculoskeletal health that will
operators. Because this problem is enable longer, healthier careers; increase
multifactorial, any possible solution productivity; provide safer workplaces
should he multifactorial as well. Available and prevent MSDs.
research supports the idea that this

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 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

FIGURES:

Figure 1: Four natural curves of human spine

Figure 2: Maintaining the cervical lordosis in the proper position

Figure 3: The upright and symmetrical sitting posture.

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 Shah A.F. et al., Int J Dent Health Sci 2014; 1(1): 68-78

Figure 4: Body stretching exercises

Fig 5: Different hand exercises

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