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 Table of Contents  
Year : 2019  |  Volume : 5  |  Issue : 2  |  Page : 40-45

An overview of ergonomics in dentistry

Department of Public Health Dentistry, DYPU School of Dentistry, Navi Mumbai, Maharashtra, India

Date of Web Publication18-Nov-2019

Correspondence Address:
Dr. Sheiba Ronald Gomes
Professor, Department of Public Health Dentistry, Navi Mumbai, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijohr.ijohr_8_19

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Ergonomics is a branch of applied science pertaining to the design and application of products and procedures for safety and maximum productivity. Musculoskeletal disorders (MSDs) or cumulative trauma disorders are disorders that affect the muscles, nerves, tendons, ligaments, cartilages, joints, and spinal discs. These are caused due to repetitive movements, excessive application of force, and incorrect posture and hence are the most common occupational hazard among the dental professionals. This review article is an overview of various articles and studies conducted that analyze the prevalence, risk factors, signs and symptoms of MSDs, and also describe ergonomic methods, procedures, and practices to prevent and palliate the symptoms of MSDs.

Keywords: Dental personnel, dentistry, ergonomics, musculoskeletal disorders, prevention

How to cite this article:
Deshmuk RC, Gomes SR, Acharya SS, Khanapure SC. An overview of ergonomics in dentistry. Indian J Oral Health Res 2019;5:40-5

How to cite this URL:
Deshmuk RC, Gomes SR, Acharya SS, Khanapure SC. An overview of ergonomics in dentistry. Indian J Oral Health Res [serial online] 2019 [cited 2024 Feb 21];5:40-5. Available from: https://www.ijohr.org/text.asp?2019/5/2/40/271147

  Introduction Top

Ergonomics is derived from the Greek word “Ergos” which means “work” and “Nomos” which means “Natural law of systems.” The International Ergonomics Association defines ergonomics as, “A 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 to optimize human well-being and overall system performance.”[1] For a dental health-care professional, an appropriate posture is extremely essential. It not only provides better access and visibility while working[2] but also ensures the prevention from repetitive strain injuries and long-term disability. On the other hand, an incorrect or awkward posture increases the risk of musculoskeletal disorders (MSDs) in an individual.[1]

The present article overviews the use of ergonomics in dentistry. It attempts to review various MSDs among dental personnel, its classification, prevalence, signs and symptoms, distribution and emphasizes the importance of ergonomic techniques, and methods for intervention and prevention of debilitating MSDs among dental personnel.

  Musculoskeletal Disorders Top

MSDs are disorders affecting the muscles, tendons, the skeleton, ligaments, cartilage, and nerves.[3] They are also known as cumulative trauma disorders or repetitive motion injuries.[4] Work environment and workplace risk factors such as repetitive and forceful movements, frequent lifting or carrying of heavy objects, and prolonged awkward postures are major factors that lead to MSDs.[5]

  Prevalence of Musculoskeletal Disorders Top

A survey of 164 dental personnel was conducted by Dajpratham et al., Bangkok, Thailand. Among all the participants, 158 reported of musculoskeletal pain. Of those with musculoskeletal pain, 32 were clinical instructors (20.3%), 52 were postgraduate students (32.9%), and 74 were dental assistants (46.8%).[6] Another survey conducted by Rehman et al., among 137 dental practitioners in Khyber Pakhtunkhwa, reported MSDs in 46.7% of the participants.[7] Munshi et al., Gujarat, surveyed 420 dentists and reported that all participants suffered from at least one work-related musculoskeletal symptom in the previous year.[8] A similar study was conducted by Leggat and Smith, Queensland, Australia, where of 285 dentists, 87.2% reported with at least one MSD symptom in the past 12 months.[9]

  Classification of Musculoskeletal Disorders Top

MSDs are presented in varying forms. They are divided according to the part of the body affected. Back disorders such as lower back pain, upper back pain, herniated spinal disc, and sciatica. Hand and wrist disorders, including De Quervain's disease, tendonitis, tenosynovitis, epicondylitis, carpal tunnel syndrome, Guyon's syndrome, trigger finger, and ulnar neuropathy. Neck and shoulder disorders such as myofascial pain disorder, cervical spondylitis, thoracic outlet syndrome, rotator cuff tendinitis/tears, tension neck syndrome, cervical disk disease, brachial plexus compression, trapezius myalgia, adhesive capsulitis, and hand-arm vibration syndrome such as Raynaud's disease.[2],[4],[5]

  Risk Factors for Musculoskeletal Disorders Top

  1. Awkward postures are postures that deviate from neutral or natural positions while working.[1] For example, handling of the objects with the back bent compared to when the back is straight.[4] Dental personnel adopts awkward postures to coordinate between themselves while performing procedures on patients.[5] Awkward postures are also assumed for a better range of vision[5],[10] and for the comfort of the patient.[5] Inadequate postures/poor positioning are directly correlated to muscular pain.[11],[12] A study conducted by Lindfors et al. on female health workers indicated a strong correlation between strenuous positions and upper extremity disorders.[13] Another study conducted by Diaz-Caballero et al. concluded that adopting awkward postures could produce muscular pain[11]
  2. Repetitive motions by the dental personnel increase the risk of developing MSDs[5],[10],[12],[14],[15] frequently, continuously,[1] and for prolonged durations. Repetitive motions cause fatigue of the muscles and tendons, thus straining them.[5] Actions such as scaling and root planing for longer durations increase the risk of developing MSDs.[1] An ergonomic risk assessment among dental professionals by baseline risk identification of ergonomic factors survey conducted by Chaiklieng S et al. and Pirvuc et al. indicated that scaling tasks had the highest ergonomics risk level[15],[16]
  3. Forceful exertions exert a tremendous amount of load on the muscles, tendons, ligaments, and joints, causing them to fatigue. Such actions, when carried out frequently, can lead to musculoskeletal problems[5],[10]
  4. Contact stresses can result from repeated or continuous contact between sensitive body parts and hard/sharp objects. The tool handle pressing into sides of the fingers[5]
  5. Vibration from frequent contact of some parts of the body with any vibrating object can cause a MSD, for example, prolonged use of power hand tools[5]
  6. Other risk factors that contribute to the development of MSDs include incorrectly designed workstation, long working hours, genetic predisposition, mental stress, poor fitness level, and suboptimal lighting.[12],[17],[18]
  7. Static postures that are held for a relatively long period can increase the risk of developing MSDs in the dental personnel. Valachi and Valachi have explained that prolonged static postures create muscle fatigue and muscle imbalance, which leads to muscle ischemia, necrosis, trigger points, and muscle substitution, resulting in pain, followed by protective muscle contraction, joint hypomobility, nerve compression, spinal disk degeneration, and herniation leading to MSD[12],[19]

  Signs and Symptoms Top

Signs and symptoms of MSDs include difficulty in carrying out normal movements, loss of normal sensation of the body parts, reduced range of motion, uncoordinated movements, decreased grip strength, fatigue in the neck and shoulder region, pain, burning or tingling sensation in arms, cramping of finger and thumb leading to weaker grip, numbness in fingers and hands, and hypersensitive hands and fingers [Figure 1].[10]
Figure 1: Signs and symptoms of musculoskeletal disorders[26]

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  Distribution of Symptoms Top

  1. In the survey conducted by Dajpratham et al., Bangkok, Thailand, the prevalence of musculoskeletal pain among the 154 participants reported pain in at least one site [Table 1][6]
  2. The prevalence of musculoskeletal symptoms among the 420 participants in a survey conducted by Munshi et al., Gujarat, is shown in [Table 2][8]
  3. According to the survey conducted by Leggat and Smith, Queensland, Australia, the prevalence of musculoskeletal symptoms experienced by dentists who interfered with daily activities in the previous 12 months by bodily location and gender (total of 285 participants) [Table 3].[9]
Table 1: Prevalence of Musculoskeletal Pain Dajpratham et al

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Table 2: The prevalence of musculoskeletal symptoms (Munshi et al)

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Table 3: Prevalence of Muskuloskeletal Disoreders (Leggat and Smith)

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  Prevention and Intervention Top

The application of proper ergonomic principles while working to prevent the development of MSDs in dental personnel and the adaptation of ergonomic designed work environment alleviate the symptoms of MSDs. This includes:

  1. Operator position and sitting posture:

  2. Standing posture is the best way to reduce any pressure on the back. However, dental personnels are required to sit for majority of the treatment purposes.[1] Maintaining a neutral posture while sitting is essential to support the uncompromised musculoskeletal balance of the dental personnel[2],[4]

    Katrova et al.[18] in their scientific paper, “Ergonization of the working environment and building up of healthy working posture of dental students,” described the following parameters of correct working postures. The sitting posture is upright and symmetrical; the shoulders hanging down relaxed with the upper arms beside the upper body; the forearms have been slightly elevated; the angle between lower and upper legs is approximately 105–110; the legs are slightly apart, making an angle of between 30° and 45°; the light beam of the dental operating light is as parallel as possible to the viewing; the sitting location for the operator should be between 9.00 and 12.00 o'clock for right-handed people and for left-handed people 03.00–12.00 o'clock; the patient's head is rotated and the sitting location adjusted; and instruments are held in three supporting points

    Practices which help maintain a neutral posture are sitting with buttocks snugly against the back of the chair, keeping the feet flat on the floor, adjusting the seat until your thighs gently slope downward, adjusting the chair such that your hips are slightly higher than your knees and distribute the weight evenly by placing your feet flat on the floor, and settling the natural lumbar curve of the lower back comfortably against the lumbar support of the chair. Angle the support forward to allow contact with the lower back, tilt the seat forward about 5°–15°, and adjusting the armrests according to the height and comfort the operator [Figure 2]. This will decrease back and shoulder fatigue and will also support your elbows, stabilizing the lower back curve by contracting the transverse abdominal muscles, work close to the patient and try to position your knees under the patient's chair, pivoting forward the hips and not the waist, alternating between standing and sitting, and adjusting the chair before positioning the patient[2],[20]

  3. Patient positioning should be such that the patient should be allowed to rest on the chair in supine or semisupine position, patient's chair should be raised to allow free movement of the operator's thighs beneath the patient's chair, and for intraoral access sites, the maxillary plane should be extended 7° beyond vertical, whereas for treating maxillary second and third molars, the maxillary plane should be 25° beyond the vertical. While working on mandibular anterior teeth, bring the patient's chin down so that the maxillary plane is 8° ahead of the vertical[5],[20]
  4. Workstation and equipment layout should be such to decrease the risk of MSDs; the dental personnel should maintain a neutral position while working. All the required dental equipment should be arranged in such a way that minimum adjustment of the posture is required while reaching for them. Access to instruments while working should be effortless, and hence, frequently used instruments should be located within “comfortable distance” (22–26″ for most people) and not above shoulder height or below waist height. When an individual sits in an erect position, the working space is divided into two areas: normal working area and maximal working area. Normal working area is the arc created, while sweeping the forearm when the upper arm is held at the side. Maximum working area is the arc created when the arm is fully extended. Diagnostic instruments, handpiece, saliva ejector, high-volume evacuator, etc., are frequently used instruments and hence have to be located in the normal horizontal reach for easy access, and less frequently items should be placed in the maximal horizontal reach[1]
  5. Magnification is possible by means of operating telescopes or loupes which are available in different designs.[20] Dental loupes offer ×2–5 magnifications.[21] These enable a better range of vision and allow the operator to maintain greater working distance while working.[4] This thus maintains a neutral posture while working[20]
  6. Hand instruments should be checked for its sharpness. If the edges of the instrument are dulled, the operator will have to use additional force while working to achieve similar results. Hence, sharp instruments have to be used at all instances. Second, an instrument with a round handle and hard edges is preferable. This will relieve the muscular stress and nerve compression on the pads and sides of the fingers. Instruments with round, smooth handles require more pinching force, and instruments with hexagonal handles do not relieve the stress and thus should be avoided. Handles that have shallow circumferential grooves or knurling should be used because they provide better friction, and hence, less grasping force is required while using the instrument.[5] Carbon steel constructed instruments are preferable[21]
  7. Automatic instruments to be preferred over manual hand instruments to reduce excessive force used during working. Handpieces should be lightweight and well balanced. Handpieces with a built-in light source provide a good range of vision and hence should be preferred. Length of the hose in the automated instruments should be as short as possible. Retractable or coiled hoses should be avoided. Handpieces with swivel mechanisms are desirable because it enables them to rotate with minimum effort[1],[5]
  8. Lighting is essential for adequate visibility in the operating field which refrains the dental personnel from straining and bending their neck. The overhead light should solely focus on the operating area without casting any shadows that might hinder the visibility. The light source should be placed in the patient's sagittal plane, directly above and slightly behind the patient's oral cavity. It should be angulated at 5° toward the head of the operator in the 12 o'clock position[4],[5]
  9. Gloves of the appropriate size and fit while working are absolutely essential. Ill-fitting gloves can cause inconvenience while working and also cause pain in the hands and fingers mainly at the base of the thumb[4],[5]
  10. Proper temperatures are recommended to be kept above 25°C to avoid deleterious effects on dexterity and grip strength[4]
  11. Appointment schedule should be so spaced that the dental personnel avoid working on cases continuously without any breaks to prevent any injuries to muscles and other tissues. Appointments can be scheduled and modified considering the difficulty of the case, time required for the procedure, buffer times, etc. This will provide adequate recovery time for the staff to prevent muscle fatigue[1],[5]
  12. Operator's stool should provide proper mobility and access to the patient's oral cavity. It should be equipped with adjustable lumbar support and an adjustable seat height along with footrests. It should accommodate different body sizes and figures. It should also provide appropriate height, optimum arm, and elbow support. Saddle stool is ideal for working as it maintains the lumbar curve of the lower back[4],[21],[22],[23]
  13. Patient chair should have a flat surface. It should be stable and should come with proper drop-down armrests, headrest, neck support, wrist, and forearm support[4]
  14. Four-handed dentistry is one of the recent trends in the dental practice. It is ergonomically the most favorable way of working. It minimizes undesirable movements of the dental personnel and maximizes effectiveness. Arrangement of the dental chair and work area should be considerable of the assistant's work area. While choosing a dental unit for ergonomic practice, the dental assistant should be the primary focus. The assistants should be responsible for handling instruments, and handpieces, while the dentist is working. This allows limited hand, arm, and body movement and can focus solely on the working field. Ergonomics is considered the most efficient way of delivering dental services because it creates a stress-free and productive environment[24]
  15. Regular exercise, including stretching and exercising regularly, to alleviate the effects of repetitive activity on the muscles. Chairside exercises can be performed between patients and a 20 min workout thrice a week will help to avoid MSDs. A comprehensive exercise plan “Absolute Dent Ergonomics Workout” was designed by Ram CS et al., I. T. S. College of Physiotherapy, India. This plan included workouts for the head, neck, back, and shoulder[25]

    1. Neck combo:

    2. Stretching by sit on a chair with feet placed parallel and spine perpendicular to the floor; rotate the neck without rotating the shoulders to left for 15 s, followed by rotation to the right for 15 s, repeat three times

      Strengthening by sitting on a chair with feet placed parallel and spine perpendicular to the floor; place both hands behind the skull cupping each other and push the neck backward allowing no net displacement of the neck for 10 s, repeat three times

    3. Hand combo:

    4. Stretching by sitting on a chair with feet placed parallel and spine perpendicular to the floor; roll the fists with full force and open them as wide as possible, repeat 10–15 times

      Strengthening by sitting on a chair with feet placed parallel and keep your hand along its heel on a flat surface covering up to the elbow at the level of the heart, fold the thumb inside toward palmer surface and grasp the hand with your other free hand, bending the hand from wrist toward your body (adduction), while the bent hand pushes the against the force for 15 s, repeat three times

    5. Shoulder combo:

    6. Stretch by sitting on a chair with feet placed parallel and spine perpendicular to the floor and relaxing the shoulders and moving them upward. Hold the position for 15–20 s and release, repeat 5–6 times

      Strengthen by sitting on a chair preferably with back support with feet placed parallel and spine perpendicular to the floor; bring both hands behind your back at the level of the heart and join both hands trying to reduce the distance between both arms by applying force for 15 s, repeat three times

    7. Back combo:

    8. Stretch by standing up straight with spine perpendicular to the floor; bend and try to touch your feet with both hands. Hold the position for 15–20 s and release, repeat 3–4 times

      Strengthen by lying down on your back on a firm surface, while keeping your arms flat on the surface, bend your legs from the knees, and lift up your pelvis. Hold the position for 10 s and release, repeat three times

      Strengthen by lying on the stomach on a firm surface; keeping the arms flat on the surface, raise your neck upward involving the lower back. Hold the position for 10 s and release, repeat three times.
Figure 2: Ergonomically correct posture[27]

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  Conclusion Top

Dental professionals are prone to different MSDs, and hence, it is important for them to educate themselves regarding musculoskeletal health. Furthermore, they need to be aware of ergonomic interventions that not only alleviate muscle stress and fatigue but also avoid career-ending permanent deleterious effects on the muscles and spine. The ergonomic techniques and strategies ensure high productivity and healthy dental practice. Hence, dental professionals should begin to work ergonomically which will also help them to maintain optimal health.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]

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