International Journal of Dental Health Concerns (2015), 1, 1-5
Doi: 10.15713/ins.ijdhc.8
REVIEW ARTICLE
Ergonomic Principles to Prevent Musculoskeletal Disorders in
Dental Professionals
Nagar Shipra1, Nagar Rohit2, Neha Gupta Aggarwal3
Department of Orthodontics and Dentofacial
Orthopaedics, Inderprastha Dental College,
Ghaziabad, Uttar Pradesh, India.
2
Department of Conservative Dentistry and
Endodontics, Kalka Dental College, Meerut,
Uttar Pradesh, India.
3
Department of Orthodontics and Dentofacial
Orthopaedics, Maharana Pratap Dental College,
Kanpur, Uttar Pradesh, India.
Correspondence:
Nagar
Shipra,
Department
of
Orthodontics
and
Dentofacial
Orthopaedics,
Inderprastha
Dental College, Ghaziabad – 201 010, Uttar
Pradesh, India. Phone: +91-9971822949,
Email: [email protected]
How to Cite:
Shipra N, Rohit N, Aggarwal NG. Ergonomic
principles to prevent musculoskeletal disorders
in dental professionals. Int J Dent Health
Concern 2015;1:1-5.
Received: 23.09.2014
Accepted: 03.11.2014
1
ABSTRACT
Dental professionals are constantly exposed to certain occupational hazards owing to their
work environment. This wide range of occupational hazards includes the musculoskeletal
disorders which markedly affect the long term efficiency and health of the dental health
care workers. The effects on overall health and wellbeing are governed the nature of
work demands of a dentist. These physical demands when exceed the normal capacity
of function, lead to symptoms of muscle fatigue, pain and deformity. These potential
problems if left ignored could severely affect the functionality of a clinician. This article
briefly discusses the need to review the ergonomic principles to prevent jeopardizing the
health of dentists and in turn improve their quality of practice.
Key words: Biocentric, ergonomics, musculoskeletal disorders, occupational hazards,
static postures.
INTRODUCTION
ergonomics related risk of musculoskeletal disorders (MSDs),
etc. These potential hazards have a definite negative bearing on
the psychological wellbeing of dental professionals.[2-8]
Health is wealth. In these fast paced busy lifestyles, we are
losing health in a voracious attempt to gain wealth. There is an
alarming increase in the work related stress in every field globally.
However due to the nature of work in dental practice, there are
specific demands in this profession too. Every profession has an
occupational environment which has certain risks and hazards
associated with it. Dental health care personnel are also exposed
to numerous occupational hazards which if disregarded can
result in some serious long-term occupational illnesses. Recent
advances in techniques and material science have allowed
to manage several problems. The developed nations have
formulated governing bodies who design definite regulations
and systematic protocol to tackle these hazards. Conversely,
in a developing nation like ours, where day-to-day practice has
its own challenges, dental professionals are yet to reckon the
potentially harmful effects.
It has been elucidated in studies that dentists report
worse health problems frequently than other high risk
medical professionals.[1] An array of occupational hazards are
encountered by dental professionals, including but not limited
to risk of infections, percutaneous exposure incidents, allergic
reactions to toxins in chemicals used, physical injury from noise
induced hearing loss, eye problems, peripheral neuropathy due to
vibrations, psychological stress, social, financial and legal hazards
MSDs
MSDs are significant physical occupational hazards which include
injuries and disorders adversely affecting the musculoskeletal
system. It comprises acute as well as chronic injuries affecting
the muscles, tendons, nerves joints, spinal discs, and ligaments
particularly affecting wrist, fingers, elbow, shoulder, neck and
back.[9] The prevalence of musculoskeletal complications in
dentists is well-documented.[10,11] There is a high prevalence
of MSDs in India, but it is not well-documented. A survey in
Karnataka revealed that at least one-third of the participant
admitted to MSDs affecting their routine practice.[12] The
conditions can be mild initially but if adequate measures are not
taken timely it may get severe to debilitating. The long term effects
of these circumstances can be described as cumulative trauma
disorders. The cause of these stress injuries can be attributed to:
• Repetitive movements
• Awkward or static postures for long durations
• Prolonged static postures
• Working in a confined space
• Limitations with the tools and equipment used
• Vibrations.
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Repetitive Movements
When same part of the body is used repeatedly, without rest
periods, it may cause muscle fatigue, discomfort and pain.
Repetitive motions are well evident in every day practice,
particularly performing scaling, root planning, during root canal
instrumentation. At the same time, the effect will depend upon
how frequently is the same repeated, with or without breaks in
between and what is the time duration of one particular type of
movement.
Vibrations
Mechanical vibration exposure occurs when one must
hold vibratory equipment/tools like dental hand pieces or
mechanical scalers for prolonged periods of time. These
Vibrations transmitted may lead to cumulative traumas. These
microtraumas add up over time and cause “wear and tear” on
the muscles, tendons, nerve tissue and associated structures.
Fatigue develops in muscles of the hand due to over stimulation
by vibrations of hand instruments. This requires the operator
hold the instrument harder with more pressure to counter these
vibrations during use. The wide use of hand tools in dentistry
work can cause a chronic extrinsic compression of the nerves
present in the hand, and therefore may cause an entrapment of
digital nerves.[10] Neurological symptoms are of consequence in
profession where tactility and manual dexterity are relevant.
Figure 1: Wrist strength and posture
Source: Agr Ability Project 2002 What to look for when selecting or
modifying hand tools to provide a better fit with the user. Available
online: http://uwadmnweb.uwyo.edu/agrability/Fact_Sheets/What_
to_Look_for_in_Hand_Tools. pdf
the most prevalent musculoskeletal complaint.[13,14] Neck and
shoulder complaints were less prevalent than back pain.[15]
Hand/wrist complaints among dentists and especially dental
hygienists are highly prevalent.[16]
One can reduce the risk of developing MSDs by incorporating
simple Ergonomic principles in clinical practice. “International
Ergonomics Association” defines ergonomics as “the scientific
discipline concerned with the understanding of interactions
among humans and other elements of a system, and the
profession that applies theory, principles, data and methods to
design in order to optimize human well-being and overall system
performance.”
Ergonomics is the relationship of the worker with their
occupational environment. Ergonomics is a way to work smarter
with greater efficiency. Suitable ergonomic design is essential
to avoid repetitive strain injuries, which overlap with time
and progressively cause a long-term disability.[17] The design
of workplace, position of dentist, position of patient, type of
equipment, techniques of using equipments and tools are
among the several factors that have an impact on the health of
dentist. They can be modified to optimize the productivity of the
practitioner. The goals of applied ergonomics in dentistry can be
summarized as follows:
• Decrease work-related pain and injuries
• Increase efficiency
• Better musculoskeletal health
• Increase comfort
• Decrease work related stress
• Enhance quality of life
• Improve career span
Awkward Postures
Mostly a “neutral” posture implies that the joints are not used at the
extreme limits of their range of motion and muscles holding them
are not overstrained. As the joint deviates farther toward extremes
of its range of motion, the posture becomes awkward imbalanced,
leading to more strain on muscles and their associated structures.
A distinct reduction in strength is seen, as illustrated in Figure 1,
where the different positions of the wrist can be seen.
Prolonged Static Postures
Static postures imply the positions where the operator does
not change positions for considerably long time. When any
stationary continuous posture without intermission is assumed
for a long duration, the blood supply to tissues slows down. This
causes a reduction in the nutrients and oxygen supply resulting in
lactic acid accumulation and other metabolites, which can cause
pain. Studies have indicated that in as much as 37.7% of work
time, the dentist’s posture is strained, which induce stress injury
on the musculoskeletal system.[11] Prolonged static postures can
lead to pain and muscle imbalances, nerve compression, spinal
degeneration. To counteract the increased stress on one group
of muscles, other groups of muscles become functional and
substitute the same.
Several studies have illustrated that dental health care workers
show symptoms of MSDs affecting back, neck shoulders and
wrists related to sustained work positions. Low back pain is
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CLINICAL GUIDELINES
of most dental instruments could range between 5.6 and
11.5 mm. Large diameters (up to 10 mm) of handles diminish
the muscle load, however no advantage is added beyond 10 mm
size. Similarly, they stated that instruments with lighter weight
(up to 15 g) also reduce the load on muscles during pinch
grasp.[20] “No. 4” handle lessens pinch gripping and can be used
for most instruments.[18] Round handles with patterns, grooved
or textured surface offer a good grip without compromising on
tactile sensation. Using a pen grasp and modified pen grasp with
three digit support offers optimum balance and workability. It
takes more effort to work with dull instruments and hence their
sharpness should be maintained on a regular basis. Sharp edged
instruments manufactured from carbon steel make could be more
efficient. Tungsten Carbide cutting edges are preferred. Burs
and files should be discarded timely before they are overused.
Lightweight, cordless hand pieces with built-in light sources
should be preferred. Angled or straight shank variety should be
chosen according to use. Properly fitted gloves, preferably right
and left handed designs should be used for better performance.
Dentist’s Seat
A dentist’s seat should have a rigid base must to prevent tipping.
The base should be rigid yet compact enough to allow proper
functioning such as to allow free access to foot controls of
dental chair, non-interfering with dental chair’s base and do
not hinder the freedom of movements of operator’s feet. With
the adoption of digitized control panels on chair and base – free
dental chairs, the foot interference is less of a problem. The seat
height should also be modifiable. With feet properly supported
on the ground, the angle between back and thighs should be
90-110°.[18] Flat footwears should be chosen for workplace.
Researchers recommend height adjustment according to
clinician’s short and tall stature. The clinician’s seat should be
in a range where their thighs are nearly parallel to the ground
and feet are fully supported.[19] If the arm rest for elbow support
is incorporated in the doctor’s stool, it should be such that the
elevation of shoulders should not occur while using these elbow
rests.[18] At the same time, the rests should not interfere with the
access to the patient. Maintain an erect posture and adjust seating
to minimize forward or lateral bending. In a seated posture,
bending and twisting motions of the spine significantly increase
the pressure in the lumbar discs when compared with standing.
Equipment Placement
Equipment layout should be such that minimum adjustment
and effort is needed to access it. The size of the dental chair’s
instrument tray should allow free movement of hands to access
instruments or material. The accessory instrument trolleys on the
operator’s working side offer a good solution to it. Fixed cabinets
on non-working side can be used to keep armamentarium seldom
required by dentist himself. The necessary items of regular
use should be kept in a “comfortable distance” (22‑26 inches
for most people) and between the shoulder height and waist
height so that extending upwards or bending downwards is
minimized. Frequently used items should be kept at horizontal
arm’s distance. Items used less frequently required can be placed
within the maximal horizontal reach. The Figure 2 illustrates the
normal and maximum work field region demonstrated by fully
extended arms.
Dental Chair
Optimum position of the oral cavity of a patient seated in the dental
chair is considered to be at the level of the seated clinician’s heart.
Adjustments can be made to facilitate functionality according to
maxillary or mandibular arch as the area of working. Any position
at higher or lower level causes strain and fatigue of shoulders. It
will unnecessarily force the dentist to assume awkward bending
or leaning forward. The body should be in a relaxed, natural
position. Arms should not be elevated and tensed. The elbows
and upper arms should stay close to operator’s body. The elbow
and forearm should be at right angle to each other. Operator
should be able to move freely with legs beneath the chair’s
headrest to prevent from undesirable forward leaning toward
patient. The base-free dental chairs these days offer a better leg
room. There should be sufficient room for the stool to move
around in different O’ clock positions. The use of retractable
overhead variety of attachments is however controversial. The
added weight of cords and resistance offered can often influence
the muscle fatigue experienced by a clinician.
Instrument Design and Selection
Material science has progressed in leaps and bounds. There is a
large influx of manufacturers with a huge variety of instruments
available in the market. The clinician must carefully select the
instruments based on it specific utility design and handling
characteristics. Dong et al. in 2006 had pointed that the diameter
Figure 2: Preferred working area of the hands
Source: Esslab. 2010. Best Practices for Workstation Organization.
Available online: www.esslab.com/Vistalab/ergonomics5.htm
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Visibility Accessibility and Illumination
Good quality mouth mirrors, when used appropriately, can help
maintain a neutral working posture. Indirect vision using mouth
mirrors can significantly prevent awkward body positioning. In
addition, they can be used to reflect light, as well as retract tongue
or cheek. However, handles should be avoided to use for retraction
as they can be hurtful. Proper retraction methods should be
employed. Using dulled, or scratched mirror surfaces cause
undue strain on the eyes while obscuring the correct details as
well. Operator has a variety of anti-fogging, double sided, scratch
resistant and disposable ones to select from. Using compressed
air improves the clarity of the operating field as well as it
enhances the ability to appreciate color and differentiate textures
of tooth surfaces, restorations and mucosal surfaces. Dentists are
often compelled to bend closer to the oral cavity for better visual
acuity during intricate procedures. Surgical magnification can
be instrumental in reducing compromised undesirable working
postures. There are stationary, or fixed microscopes mounted
on wall or ceiling used for high magnification. Surgical Loupes
with lower magnification levels attachable to a head band or
mountable on operator’s glasses can dramatically augment their
visual competence thereby improving the working posture.
Proper lighting is of paramount importance during any clinical
procedure. Ideally it should create an uniform, shadow-free,
color-corrected illumination of the operating filed. Normally the
light source should be placed directly above and slightly behind
the patient’s oral cavity. To minimize shadows, the trajectory of
the light beam should be as close along as the line of vision of the
operator. Use of two light sources has also been suggested.
Take Home Tips
If musculoskeletal symptoms appear, seek professional
consultation from a physician. Intelligent and meticulous patient
management can be helpful. Modifying the work schedule to
include short “stretch break” periods between patients will
prevent muscle fatigue. It increases blood flow to muscles,
replenishes the nutrient supply and allows the stressed parts to
recompose. Incorporate appropriate finger rests where required.
One should change posture as frequently as one can to prevent
muscle ischemia associated with static postures. Schedule the
appointments such that easy and difficult, lengthy procedures are
alternately placed. Give more treatment time for more difficult
patients. One can reserve the dominant hand for precise operative
procedures while try to utilize the other hand for accessory tasks
like lifting objects, etc.
CONCLUSION
An ounce of prevention is better than a pound of cure. Considering
the impact of ergonomically designed and chosen equipment
on the efficiency one must modify the workplace to reduce the
possibility of injuries. Paying attention to body symptoms does
pay in the long run. Among the various occupational hazards,
MSDs are very much at the disposal of the clinician himself.
Adopting newer techniques, armamentarium and work strategies
can definitely prevent detrimental changes in the future.
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