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 Table of Contents  
Year : 2015  |  Volume : 4  |  Issue : 1  |  Page : 13-18

Correlation of Biomechanical Exposure with Cumulative Trauma Disorders of Upper Extremity in Dental Surgeons

Department of Physiotherapy, Pad. Dr. D.Y. Patil University, Nerul, Navi Mumbai, Maharashtra, India

Date of Web Publication19-Oct-2015

Correspondence Address:
Tejashree A Dabholkar
Haware's Green Park, B-2/603, Plot No. 15, Sector 22, Kamothe, Navi Mumbai - 410 209, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2277-4696.167531

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Aims and Objectives: The aim of this study was to determine the occupational musculo-skeletal problems in dentists and to investigate the related risk factors. Biomechanical risk exposures measures are available as is various activity limitations. Activity limitation is specific for various cumulative trauma syndromes found in dental occupation. Hence, this study aims at correlating these two parameters. Study population involves private and institutionalized dentists. So study aims to do a comparison in between the groups also. Materials and Methods: 250 dentists working in Navi Mumbai and Mumbai were included in the study. Their mean ages were 30.15 ΁ 5.70 years. The musculo-skeletal system problems, activity, limitations, pain levels, working posture are some of the factors investigated. Results: The biomechanical exposure analyzed (rapid upper limb assessment, occupational repetitive action) showed strong association with various cumulative trauma disorders assessed by (neck disability index, disabilities of arm, shoulder, hand, and carpal tunnel syndrome questionnaire). Conclusion: Musculo-skeletal problems existed due to the occupational working conditions and these problems caused activity limitation with varying degrees. Occupational risk factors in dentists make dentists conscious about this issue and also preventive rehabilitation programs have to be planned.

Keywords: Biomechanical exposures, cumulative trauma disorders, dentistry

How to cite this article:
Dabholkar TA, Gandhi P, Yardi S, Dabholkar AS. Correlation of Biomechanical Exposure with Cumulative Trauma Disorders of Upper Extremity in Dental Surgeons. J Dent Allied Sci 2015;4:13-8

How to cite this URL:
Dabholkar TA, Gandhi P, Yardi S, Dabholkar AS. Correlation of Biomechanical Exposure with Cumulative Trauma Disorders of Upper Extremity in Dental Surgeons. J Dent Allied Sci [serial online] 2015 [cited 2023 Mar 27];4:13-8. Available from: https://www.jdas.in/text.asp?2015/4/1/13/167531

  Introduction Top

Macdonald et al., Osborn et al. estimated that each year 70% of dental surgeons report musculo-skeletal pain with the low back pain, neck and shoulder, the most frequent sites of musculo-skeletal pain. [1] Because the dentists spend long hours hunched over their patients with their arms raised and their hands positioned relative to their patients' mouths, unsupported stress is placed on the muscles of the lower back, neck, and shoulder area of the dentist. Occasional pains from irregular stances or positions are to be expected while they are performing static work. [2] However, when the pain becomes a regular occurrence, the cumulative damage could arise leading to debilitating injuries. [3] When dentistry changed from a standing job to a sit down the task, musculo-skeletal pain in the neck and shoulder region also became more prevalent. This leads to various work-related musculo-skeletal disorders (MSDs).

MSDs may be caused, [4],[5] or aggravated by the presence of one or more or any combination of following risk factors: Repetition, awkward or static postures, high forces and contact stress. When these factors exist simultaneously, the risk of developing cumulative trauma disorders (CTDs) is significantly increased. [4] Although some musculo-skeletal injuries occur at one specific moment, many more injuries result from repeated strength demands coupled with the lack of significant rest periods that together.

Exceed the tissue tolerance of an individual stated by Putz-Anderson et al. Many difficult working postures including rotation and flexion of the cervical spine, flexion of elbow, and repetitive forceful hand grip are inherent in dental work. [6],[7] Since dental work consists of precision tasks, involving a high degree of visual and manipulative elements, sometimes in combination with the exertion of force. [7],[8]

Upper limb postures and movements during repetitive tasks are of basic importance in contributing toward the risk of various MSDs. A definite agreement is found in literature as to the potential damage coming from extreme postures and movements of each joint, from postures maintained for a long time (even if not extreme) and from specific, highly repetitive movements of the various segments. [9] Common awkward postures in dental practice include elbow and wrist flexion and thumb hyperextension, which have been shown to stress neurovascular structures and ligaments. [4]

CTDs are injuries of the musculo-skeletal and nervous systems that may be caused by repetitive tasks, forceful exertions, vibrations, mechanical compression (pressing against hard surfaces), or sustained or awkward positions. These painful and crippling disorders develop over periods of weeks, months, or years. They include carpal tunnel syndrome, [10] tendinitis, tenosynovitis, De Quervain's disease, ulnar and radial nerve entrapment syndromes, and various shoulder, neck, and upper back injuries.

The ergonomic tool kit provides a variety of ergonomic assessment tools and information on ergonomic analysis. When selecting ergonomic assessment tools to use to analyze a task, it is important to select a tool that:

  1. Analyzes the risk factors found in the informal assessment,
  2. Analyzes the body regions used for the task,
  3. Includes duration if the task is complex or multi-tasked, and
  4. Provides the results needed (qualitative vs. quantitative). [11]

The biomechanical risk exposures in this study are analyzed through various scales viz., rapid upper limb assessment (RULA), and occupational repetitive actions (OCRAs).

The RULA is a survey method developed to investigate the exposure of individual workers to risk factors associated with work-related upper limb disorders. The OCRA method, [9] which is suggested as a preferred method to measure the risk of biomechanical overload of the upper limbs in biomechanical standards, provides criteria and assessment tools for risk evaluation at different levels of detail. Apart from the OCRA index, a tool for an analytical risk assessment that should be used mainly when designing or redesigning jobs, the OCRA checklist has been proposed: This tool is used for an initial screening of the risk associated with the manual, repetitive work. Thus, this study is conducted to assess various biomechanical risk exposures among dental practitioners correlating it with a number of musculo-skeletal problems.

This study mainly focuses on the conservative dentistry as the primary goal of such dental surgeons includes the techniques and procedures to restore the teeth to full function and appearance. Analysis of biomechanical risk exposures helps to analyze work posture and activity limitation which is checked by various upper extremity tools such as disabilities of arm, shoulder, hand (DASH), carpal tunnel syndrome questionnaire (CTSQ), and neck disability index (NDI). Correlation existing between these two gives a guideline for further rehabilitation of dental professionals. Hence study aims at doing so.

  Materials and Methods Top

Institutional Ethics Committee approval was taken 250 dental surgeons involving institutionalized and private practitioner of Navi Mumbai and Mumbai and those fulfilling criteria were randomly selected for study.

Inclusion criteria

  1. Subjects below the age of 40 years.
  2. Subjects with the experience of more than 2 years.

Exclusion criteria

  1. Previous history of neurological problems.
  2. Subjects having any musculo-skeletal pathology or trauma.
  3. Subjects are having diabetes, thyroid gland disease, or on steroid therapy.


  1. Tripod stands [Figure 1].
  2. Camera.
  3. Measuring tape.
  4. Protractor [Figure 2].
  5. Software for analysis (Kinovea).

The subjects fulfilled the minimum criteria of BDS degree (100%). Out of these, BDS (12%), MDS (56%), and the rest were pursuing postgraduation (32%). Maximum subjects (n = 155) subjects were working on the lower jaw while others (n = 95) were working on the upper jaw.
Figure 1: Tripod stand

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Figure 2: Protractor

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The dentists' sitting position was noted (clock-related), of which the maximum dentists had acquired a 10 o'clock (80%) and a few of them had 11 o'clock position (10%) and 9 o'clock position (10%). Subjects were taken from the Conservative Dentistry Department whose treatment procedures include exfoliation, root canal treatment and management of traumatized teeth, which the common procedures are done even at private set up clinics. Four hand dentistry was practiced by 12% and two hand dentistry by 88%. The evaluations were carried out as follows.

Problems of the musculo-skeletal system

Body discomfort survey was used to determine the prevalence of symptoms related to the musculo-skeletal system. The questionnaire along with the presence of activity limitations in the last 12 months investigated the presence of musculo-skeletal system problems related to neck, shoulder, elbow, wrist, upper back.

Activity limitations

Two hundred and fifty dental surgeons with a common area of involvement as the neck, upper extremity and any clinical features of carpel tunnel syndrome as per the assessment were included. Activity limitations due to neck pain were evaluated by NDI. [12] Also shoulder activity limitation was assessed by DASH questionnaire [12] and the CTSQ considered symptom severity scale.

Working posture

The working dental postures were recorded by taking serial videos in three different views:

  1. Lateral/anterior view for upper body.
  2. Lateral/anterior view for entire body.
  3. Top view from head end for wrist positions.

A two-dimensional camera of 14 megapixels (Nikon) was placed on a tripod stand [Figure 1] so that still videos can be taken. The gyrometer on the tripod stand was used to set the camera parallel to the floor. Height or angular adjustments [Figure 2] were made according to the view needed and set at a perpendicular sagittal plane to record the view, the camera was placed about 1.5 m away from the dental chair [Figure 3]. This was done to take the recordings of the working dental posture [Figure 4]. The data acquired was then transferred to Kinovea Software (Franklin Street, Boston, USA) [13] to aid in the assessment of further evaluation [Figure 5].
Figure 3: Analysis using Kinovea software

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Figure 4: Line joining digital markers using Kinovea

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Figure 5: Measurements of angles using Kinovea

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Data analysis

Statistics done by graphPad instat3 software.

  Discussion Top

The purpose of the study was to analyze the association of various biomechanical risk exposures such as awkward postures, repetitive movements with the incidence of CTD's of the body in dental surgeons.

RULA proceeds to find action levels, recovery needs and indicates the level of intervention required to reduce the risk of injury due to physical loading on the operator. We can imagine dentist during his/her job that holds a mirror in one hand and a low or high speed instrument in the other hand (or other professional instruments) with neck in a constant position for better visual inspection. In other words, RULA ensues to assess this condition and makes us realize the seriousness of the affairs.

When Mann-Whitney U-test was used for comparing data, the study revealed that there is a statistically significant difference of RULA scores (P = 0.0163) in females (institutional and private) [Table 1]. Also when RULA scores were correlated with NDI, by using Pearson test, it was found that there is a significant association of RULA with NDI in both males and females [Table 2]. Private practicing males and females both showed a significant increase in NDI values [Table 3]. Thus, the biomechanical risk factor which was analyzed by RULA score showed association with neck problems. This could be because of the constant static awkward posture of the neck acquired by the dentist for long working hours. Also, age and years of practice add up to cause neck disabilities. Neck and arm strain can be prevented by keeping the head and neck in proper alignment. The slight inward curve of the neck balances the head on the spine. Holding the head forward disturbs this balance, straining the joints, and the muscles of the neck and upper back. This posture also causes compression of the nerves and blood vessels as they exit the neck, leading to symptoms in the arm and hand. [4] Neck problems generally arise from prolonged static neck flexion and shoulder abduction or flexion, lack of upper extremity support, and inadequate work breaks. Awkward postures are often adopted to obtain better views of the intraoral cavity, provide a more comfortable position for the patient and to coordinate their position relative to the dentist or assistant. [4] DASH found no significant association with arm and Shoulder pain in our study.
Table 1: Comparison of RULA and OCRA score between male (institutionalized vs. private) and female dentists (institutionalized vs. private)

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Table 2: Correlation matrix of RULA, OCRA with NDI, DASH, CTS

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Table 3: Comparison of activity limitation between male (institutionalized vs. private) and female (institutionalized vs. private) dentists

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OCRA is a tool, which covers recovery period, posture, force, and repetitiveness. An example of a gripping task requiring high force application could be holding small instruments for a prolonged period of time. This task is commonly performed with a pinched grip where the fingers are on one side of the object and the thumb is on the other. This form of gripping is undesirable as it requires a much greater force application than a power grip (object in the palm of the hand). Researchers have suggested that excessive use of a pinch gripping is the greatest contributing risk factor in the development of MSDs among dental surgeons (Sanders, 1997). [4] Additionally, scaling, drilling procedures involving both waving and rotary motion power strokes have been classified as the most demanding task required of dentists' (Horstman, 1997). [4] Thus, the repetitive tasks increase the probability of disorders such as carpal tunnel syndrome, De Quervain's, and Guyon's syndrome, etc.

During instrumentation, there is a constant alternation between wrist flexion, extension, and forearm rotation. Repetitive gripping is experienced throughout the day in order to write, clean and hold instruments, and expose radiographs. Such high usage of wrist and forearm musculature has been linked to an increased risk of fatigue and overuse (Sanders, 1997). Repetitive motions are extremely prevalent in clinical practice, particularly when performing scaling, root planning and polishing leading to CTDs of various kinds. In our study, we found that OCRA scores to show no statistical significant difference in Institutional and Private Practitioners [Table 1]. But when OCRA scores were correlated with CTS scores; using Pearson Correlation test [Table 2] there was significant association among institutional males (P = 0.024), and male private practitioners (P = 0.000) and in female institutional practitioners (P = 0.0008). There was no significant correlation in private practitioners females.

Less working hours could be a probable cause for this; with mean working hours of 6.91 ± 0.58 in comparison with others which was the higher mean of 8.38 ± 0.74 in private male subjects. This states that repetitive movements of wrists keeping ring finger as the fulcrum for their tasks poses a prevalence of wrist pains and carpal tunnel syndromes.

Thus to conclude, that there are various risk exposures leading to CTDs. Dental chair, the workspace, work station, instrumentation, equipment layout, lighting, and working posture is some of the ergonomic drawbacks causing dentists to suffer from MSDs. Work habits such as increased number of working hours, reduced number of breaks, no stretching and ROM. Exercises in breaks lack of awareness on ergonomics also in turn lead to aches and pains. According to RULA and OCRA scoring, it can be said that institutional practitioners are at medium risk and need investigation and care to be taken not to develop severe overuse disorders. Private practitioners are at higher risk, and implementation of proper ergonomics is needed soon.

  Conclusion Top

Musculo-skeletal problems existed due to occupational working conditions and these problems caused activity limitation with varying degrees. Occupational risk factors in dentists make dentists conscious about this issue and also preventive rehabilitation programs have to be planned for the prevention of activity limitation due to CTDs.


We wish to express our sincere thanks to Dr. Sujata Yardi (honorary and expert of advisory committee of Dr. D.Y. Patil University, Nerul, Navi Mumbai, Maharashtra, India) and Dr. Unnati Pandit (Professor and Director) of School of Physiotherapy, Dr. D.Y. Patil University, Nerul, Navi Mumbai, Maharashtra, India.

We would like to thank all the dental surgeons of Navi Mumbai, also all the Head of Departments of Dental Colleges in Navi Mumbai, Maharashtra, India, who allowed us to administer this instrument and for their cooperation.

Financial support and sponsorship

Equipment by Dr. D.Y. Patil University, Department of Physiotherapy, Nerul, Navi Mumbai, Maharashtra, India.

Conflicts of interest

There are no conflicts of interest.

  References Top

Anton D, Rosecrance J, Merlino L, Cook T. Prevalence of musculoskeletal symptoms and carpal tunnel syndrome among dental hygienists. Am J Ind Med 2002;42:248-57.  Back to cited text no. 1
Kaul R, Shilpa PS, Sanjay CJ. Musculoskeletal disorders and mental health related issues as occupational hazards among dental practitioners in the city of Bengaluru: A randomized cross-sectional study. Int J Med Dent Sci 2015;4:589-98.  Back to cited text no. 2
Pitts FM. Musculoskeletal Disorders in Dentistry. Bachelor of Science in Mechanical Engineering, Southern University, 1993-December; 2005.  Back to cited text no. 3
Ergonomics and Dental Work - Occupational Health Clinics for Ontario Workers Inc; p. 1-28, workbook. www.ohcow.on.ca  Back to cited text no. 4
American Dental Association. An introduction to ergonomics: Risk factors, MSDs, approaches and interventions. AEGIS communications: American Dental Association; 2004.  Back to cited text no. 5
Wieslander G, Norbäck D. Dental work. In: Brune D, Gerhardson G, Crockford GW, D′Auria D, editors. The Workplace. Vol. 2. Geneva, Switzerland: International Labour Office, Scandinavian Science Publishers; 1997. p. 82-9.  Back to cited text no. 6
Chaikumarn M. Differences in dentists′ working postures when adopting proprioceptive derivation vs. Conventional concept-department of human work sciences, Lulea University of technology, Lulea, Sweden. Int J Occup Saf Ergon 2005;11:441-9.  Back to cited text no. 7
Hagberg M, Hagberg C. Risks and prevention of musculoskeletal disorders among dentists. In: Brane D, Edling C, editors. Occupational Hazards in the Health Professions. Boca Raton, FL, USA: CRC; 1989. p. 323-32.  Back to cited text no. 8
Colombini D, Occhipinti E, Delleman N, Fallentin N, Kilbom A, Grieco A. Exposure assessment of upper limb repetitive movements: A consensus document. In: Karwowski W, editor. International Encyclopedia of Ergonomic and Human Factors. London: Taylor & Francis; 2001. p. 52-66.  Back to cited text no. 9
Haghighat A, Khosrawi S, Kelishadi A, Sajadieh S, Badrian H. Prevalence of clinical findings of carpal tunnel syndrome in Isfahanian dentists. Adv Biomed Res 2012;1:13.  Back to cited text no. 10
[PUBMED]  Medknow Journal  
Ergonomic Assessment Toolkit - AIHA. http://aihce2015.org/course/ergonomics-toolkit-applying-advanced-tools-in-assessment/  Back to cited text no. 11
Tonga E, Atasavun Uysal S, Cem Güngör H. Evaluation of occupational musculoskeletal problems and related risk factors among Turkish dentists working in a university clinic. Clin Dent Res 2013;37:38-44.  Back to cited text no. 12
Guzmán-Valdivia CH, Blanco-Ortega A, Oliver-Salazar MA, Carrera-Escobedo JL. Therapeutic motion analysis of lower limbs using Kinovea. Int J Soft Comput Eng 2013;3:359-65.  Back to cited text no. 13


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1], [Table 2], [Table 3]

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