The document discusses ergonomics in dentistry. It defines ergonomics as the study of work and outlines goals of improving job processes, reducing injury risk, and minimizing fatigue. Risk factors for musculoskeletal disorders in dentistry are identified, including prolonged static postures and repetitive motions. The document recommends applying ergonomic strategies like proper positioning, magnification, four-handed dentistry using an assistant, and work simplification techniques to reduce injury risks.

1. Ergonomics In Dentistry
Dr. Prabhu
Department of Public Health Dentistry

2. Objectives:
By the end of this lecture you will be able to:
•Become familiar with the field of Ergonomics.
•Identify risk factors and stressful individual behaviors in dentistry
which lead to injuries.
•Learn how to apply preventive strategies, including good posture
and positioning.

3. Outline:
• Definition of ergonomics.
• Ergonomics design goals.
• Risk factors for MSDs.
• Application of ergonomics in dentistry.
• Four Handed Dentistry.
• Work Simplification Techniques.

4. Definition
• Derived from the Greek…”ergo” meaning work and “Nomos” the study
of... Literally the study of work.
• The International Ergonomics Association (IEA) defines ergonomics
(or human factors) as
• “the scientific discipline concerned with the understanding of the
interactions among humans and other elements of a system, and the
profession that applies theoretical principles, data and methods to
design, in order to optimize human well-being and overall system
performance.

5. Ergonomic Design Goals
1. Improve job process by eliminating unnecessary tasks, steps &
effort.
2. Reduce potential for overexertion injury.
3. Minimize mental/physical fatigue potential.
4. Leverage workers ’skills/knowledge of their jobs to increase their
satisfaction, comfort and fulfillment.

6. Consequences of Poor Design:
• Discomfort →Chronic Pain
• Accidents →Injuries
• Fatigue →Increased Errors
• Work-Related Musculoskeletal Disorders (WMSDs):
-Low back pain**most common**
-Tendonitis
-Epicondylitis
-Carpal tunnel syndrome( CTS)

7. • More than 70 percent of dental students of both
sexes reported neck, shoulder and lower back pain
by their third year of dental school.
• Present in up to 81% of dental operators.
• The common reason for early retirement among
dentists is MSDs (29.5%)
(JADA, Vol. 136, January 2005)

8. Risk factors contribute to MSDs:
Prolonged use of
vibrating hand
tools.
Static neck, back,
and shoulder
postures.
Repetitive motions
(e.g., scaling,
polishing).
Grasping small
instruments for
prolonged periods.
Excessive Force
(e.g. tooth
extraction).

13. Application of Ergonomics in Dentistry

14. Application of Ergonomics in
Dentistry
Instruments
Hand
instruments
Vibrating
handpieces
Equipments
Lighting
magnification
Operator and
patient chair
Work postures
Patient
position
Dentist
position

15. 1-Instruments:
• Hand instruments:
Goal: to reduce force exertion while allowing for neutral joint
positioning.
Handle shape and size:
-Dental instrument diameter ranges from 5.6 to 11.5 mm.
-larger handle diameters reduce hand muscle load and pinch force.
-Sleeves that fit over the handles of mirrors.
-A round handle VS hexagon handle.

16. 1-Instruments:
• Hand instruments:
Weight:
-Light weight instruments (15 g or less).
- Hollow VS Resin
Balance:
-The instrument should be equally balanced within the hand so that the
tendency to deviate the wrist is reduced.
Sharpness:
-As a tool becomes dull, additional force is required to perform tasks.
Texture:
-Knurled handles such as diamond-shaped or crisscross patterns
Color coded instruments are easier to be identified

17. 1-Instruments:
• Dental Hand Pieces:
When selecting hand pieces, look for:
• Lightweight, balanced models (cordless preferred).
• Sufficient power.
• Built-in light sources.
• Angled vs. straight-shank.
• Easy activation.

18. 2-Equipments:
• Equipment layout:
Dental equipment should be located in a
manner which allows you to maintain
a neutral working posture and reduce
postural deviation while working.

19. 2-Equipments:
Frequently used items:
-“comfortable distance”
(22–26 inches)
-within a normal horizontal
reach which is the arc
created while sweeping the
forearm when the upper
arm is held at the side.
Less frequently used items:
- Should be placed within
the maximal horizontal
reach which created when
the arm is fully extended.

20. 2-Equipments:
• Lighting:
Goal: to produce even, shadow-free, color-corrected
illumination concentrated on the operating field to
also awkward working postures.
• Overhead light should be positioned as close as
possible to the sight line.
• Hand mirrors to reflect the light intra orally.
• Use fiber optics in handpiece.

22. 2-Equipments:
• Magnification:
Goal: to improve the neck posture and provide clear
vision.
• Use of various magnification systems, dental
professionals are able to increase their working
distance and assume more of an upright body posture.
• “surgical loupes” and can be mounted to a headband
or onto the operator’s glasses.

24. 2-Equipments:
• Patient’s chair:
Goal: to promote patient comfort and maximum patient
access.
Look for:
-Stability.
-Pivoting or drop-down arm rests (for patient ingress/egress).
-Supplemental wrist/forearm support (for operator).
-Articulating head rests.
-Hands-free or preset operation.

25. 2-Equipments:
• Operator chair:
Goal: is to promote mobility and patient access and to
accommodate different body sizes.
Look for:
-Stability (5 legged base w/casters).
-Adjustable lumbar support.
-Seat height adjustment.
-Adjustable foot rests.
-Adjustable, wrap-around body support or arm supports.

26. 2-Equipments:
• Operator chair:
RGP’s new Straddle stool
-provides optimal seating allowing for proper
positioning of the spine and the pelvis.
-the Straddle stool pre-positions you into an anterior
pelvic tilt.
-The angle of seat allows for proper balance of core
muscles and allows for the maintenance of normal
curvature without the use of a backrest and
without placing stress on the lower spine.

27. Normal stool RGP Straddle Stool

28. 3-Position and postures:
• Patient position:
“Supine position”
-The patient’s heels should be slightly higher than the tip of the nose.
This position maintains good blood flow to the head.
-An apprehensive patient is more likely to faint if positioned with the
head higher than the heels.
-The chair back should be nearly parallel to the floor for maxillary
treatment areas. (Chin up)
-The chair back may be raised slightly for mandibular treatment areas.
(Chin down)

29. 3-Position and postures:
Chair position when treating
maxillary Arch
Chair position when treating
mandibular arch

30. 3-Position and postures:
• Operator position:
Neutral position is the ideal positioning of
the body while performing work
activities and is associated with
decreased risk of musculoskeletal injury.

31. 3-Position and postures:
• Neutral seated position in relation to the patient:
1.Forearms parallel to the floor.
2.Weight evenly balanced.
3.Thighs parallel to the floor and knees are apart.
4.Hip angle of 90°.
5.Seat height positioned low enough.
6.Shoulders relaxed & parallel with floor.
7.Eyes directed downward.
8.(14-16) inches distance should be between the patient’s mouth & clinician’s
eyes.
9.Elbows close to sides.
10.Patient’s mouth at elbow height.

32. 3-Position and postures:

33. Some wrong Postures In
Dental Office

35. How to avoid all this pain!!!!
SCHEDULING

36. Scheduling
Recommendations when scheduling include:
•Incorporate brief “stretch break” periods between patients.
•Develop a patient difficulty rating scale to ensure difficult
treatment sessions are not performed consecutively.
•Increase treatment time for more difficult patients.
•Alternate procedures performed.

39. LOWER BACK STRETCH EXCERCISE

40. Four Handed Dentistry

41. Four handed dentistry:
• Definition:
“It is an ergonomically sound way to practice dentistry using the skills
of the dental assistant while including work simplification
techniques.”
- The term “Four handed dentistry” was first recorded in a conference
on “training dental students to use chair side assistants” in 1960.Since
then, this term has been widely used.
-Goal: to allow the dentist and assistant to function as a team in a
seated position with maximal efficiency and minimal strain.

42. Four handed dentistry:
• Basic tenets of four-handed dentistry:
To practice true four handed dentistry, the following criteria must
be met:
1.Minimize unnecessary motion, equipments must be
ergonomically designed.
2.Both the operating team and the patient should be comfortably
seated.
3.Pre-set trays are utilized.
4.The dentist assigns all legally delegable duties to qualified
auxiliaries based on the state’s guidelines.
5.Treatment Plan of the patient is designed in advance in a logical
sequence.

43. Four handed dentistry:
• Zones of activity:
- The work area around the patient is divided into four
“zones of activity”.
- Zones of activity are identified using the patient’s face as
the face of a clock.
• The four zones are:
a)Operator’s zone.
b)Assistant’s zone.
c)Transfer zone.
d)Static zone.

44. Four handed dentistry:
N.B: The static zone, which is the zone of least activity. Instruments that are
infrequently used such as the blood pressure equipment and portable curing light
can be stored in this area.

45. Four handed dentistry:

46. Four handed dentistry:
• Equipment setup design:
The basic dental unit designs available today include:
- Side delivery.
- Rear delivery.
- Split unit.
- Transthorax.

47. Four handed dentistry:
• Equipment setup design:
Transthorax:
- Promotes good ergonomic positioning.
- Save Time and less motion.
- The unit over the patient’s thoracic area.
- The assistant can easily retrieve the handpieces and transfer
them to the doctor who does not need to remove his or her
eyes from the operating site.

48. Four handed dentistry:
• Equipment setup design:
Side delivery:
- This unit requires the dentist to pick up the handpieces,
which forces him to remove his eyes from the treatment
site, twist and turn to grasp the instrument, and then
refocus, this results in stress and fatigue.
- The assistant can’t reach the instruments to exchange
handpieces or change burs, reducing productivity. (HVE)

49. Four handed dentistry:
• Equipment setup design:
Rear delivery:
- The units are mounted in a fixed position that cannot be
moved and HVE hosing and air/water syringes are
permanently fixed to an assistant’s work area.
- The doctor must pick up the handpiece then transfer it
from the retrieval hand to the operating hand.

50. Four handed dentistry:
• Equipment setup design:
Split unit/cart:
- This concept places part of the dental unit on the
operator’s side and the (HVE) and air/water
syringe on the assistant’s mobile cabinet.
- Doctor and assistant?

51. Four handed dentistry:
• Types of Instrument Transfer:
Single Handed Transfer Double Handed Transfer

52. Work simplification techniques:
• Four principles of work simplification:
1.Elimination: A 100% saving can be accomplished by elimination of
unnecessary equipment, instruments, steps in procedures and
movements.
2.Combination: If the functions performed by two instruments or
pieces of equipment can be combined into one instrument or a
piece of equipment, or if two steps in a procedure can be
combined to accomplished in one step, a 50% saving can be
realized.

53. Work simplification techniques:
• Four principles of work simplification:
3.Rearrangement: It may be possible to rearrange equipment and
materials in the operatory, scheduling of patients, or steps in clinical
procedures to take better advantage of available space and time.
4.Simplification: Every effort should be made to simplify dental office
equipment and patient treatment procedures in order to introduce a
minimum number of variables and permit the team to function
most effectively.

56. Conclusion:
• Considering the impact of ergonomically designed and chosen
equipment on the efficiency, One must modify the workplace to
reduce the possibility of injuries.
• 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.