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Year : 2020  |  Volume : 24  |  Issue : 3  |  Page : 227-232  

Standardized photometric assessment method: A novel approach for the analysis of dental ergonomic posture

1 Department of Periodontics, CSI College of Dental Sciences and Research, Madurai, Tamil Nadu, India
2 Department of Periodontics and Implantology, Rajas Dental College and Hospital, Tirunelveli, Tamil Nadu, India
3 Department of Public Health Dentistry, Karpaga Vinayaga Institute of Dental Sciences, Madhuranthagam, Tamil Nadu, India

Date of Submission02-Aug-2019
Date of Decision18-Feb-2020
Date of Acceptance26-Feb-2020
Date of Web Publication04-May-2020

Correspondence Address:
Thamil Selvan Muthuraj
29/4, C-1, O Trunk Road, Sattur, Viruthunager - 626 203, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jisp.jisp_405_19

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Background: Identification and documentation of the proper and improper dental ergonomic postures have gained its importance in the recent years due to the increased prevalence of work-related musculoskeletal disorders (WMSDs) among dentists and dental students who do not practice proper ergonomic procedure. Aim: The aim of the present study is to analysis ergonomic posture among dental students while performing supragingival scaling (SGS) procedure, using the standardized photometric assessment method (SPAM). Materials and Methods: A total number of 90 students from the third year (III year) to final year (IV year) and internship (Intern) (30 each) were included in the study. All the 90 students were asked to perform SGS procedure and were photographed and analyzed using the current technique. Eight dental ergonomic postures were analyzed in this study and grouped according to the classification system developed for scoring dental ergonomic postures by Garbin et al., in 2011. Analysis of variance test with Bonferroni correction was used to statistically analyze the collected data. Results: The mean index value for III year, IV year and Intern were 2.00, 2.03, and 2.13, respectively, which was not statistically significant (P = 0.709). Conclusions: Analysis of the dental students using the current method showed that most of them come under inadequate and regular category which puts them in a high risk for developing WMSDs. The SPAM to analyze the dental ergonomic posture was simple and effective and should be further explored in the future studies for its pros and cons.

Keywords: Ergonomic assessment, ergonomics, human factors engineering, musculoskeletal disorders, work-related musculoskeletal disorders

How to cite this article:
Muthuraj TS, Raja J, James JR, Mohan Raj JP, Subramnian D, Varatharajan A. Standardized photometric assessment method: A novel approach for the analysis of dental ergonomic posture. J Indian Soc Periodontol 2020;24:227-32

How to cite this URL:
Muthuraj TS, Raja J, James JR, Mohan Raj JP, Subramnian D, Varatharajan A. Standardized photometric assessment method: A novel approach for the analysis of dental ergonomic posture. J Indian Soc Periodontol [serial online] 2020 [cited 2022 Aug 10];24:227-32. Available from:

   Introduction Top

The word ergonomics is derived from two Greek words “ergon” and “nomos” meaning work and natural law, respectively. International Ergonomics Association defines ergonomics as “the scientific discipline concerned with the understanding of interactions among humans and other elements of system, and the profession that applies theory, principles, data, and methods to design to optimize human well-being and overall system performance.”[1] About 64%–93% prevalence of work-related musculoskeletal disorders (WMSDs) has been reported in dental literature among dentists and dental students who do not practice proper ergonomic procedure.[2] Hence, the identification and documentation of the proper and improper dental ergonomic postures have gained its importance in the recent years.

A number of exposure assessment methods have been proposed in literature which can be broadly grouped into three categories (self-reports, observational methods, and direct measurements).[3] In self-reports, questionnaires and interviews are used to collect data from the work place to analyze the exposure of the workers to risk factors for WMSDs.[4],[5] In observational studies, photography and videography are used to collect data and analyzed by simple observation or sophisticated computer software.[6],[7] In direct method, sensors such as handheld electronic goniometers, lumbar motion monitor, and tri-axial accelerometers are used to collect and analyze data.

Unfortunately, most of the above-mentioned methods are not specifically developed for dental ergonomic posture assessment, even though they have been used to record and analyze the dental postures and prevalence of WMSDs among dental students, dental hygienists, and dental clinicians. Hence, a novel method, standardized photometric assessment method (SPAM) which comes under the category of simple observational technique, has been proposed to assess exclusively the dental ergonomic posture followed by dental practitioners. In the current study, SPAM was used to record and compare the postures followed by dental students during the supragingival scaling (SGS) procedure.

   Materials and Methods Top

Study outline

A sample of 90 students, belonging to the third year (III year), final year (IV year) and internship (Intern) attending the department of periodontics and implantology and willing to participate in the study, were included. Each group consists of 30 students. The study was approved by the Institutional Ethical Committee and was conducted in full accordance with the World Medical Association Declaration of Helsinki. Verbal consents were obtained from all the participants which was approved by the Institutional Ethical Committee. All the students were photographed using the SPAM specification while they were performing SGS in a specified area. A total of 180 photographs (two photographs for each student sample) were taken and analyzed in the current study.

Dental ergonomic postures examined

Eight different dental ergonomic postures were analyzed as previously proposed by Garbin et al.,[8] which are as follows:

  1. Leg angle (LA): Angle between the lower and upper leg – approximately 110°
  2. Head tilt angle (HTA): Up to 25°
  3. Sitting position (SP): Tilt of the upper body between 10° and 20°
  4. Elbow position (EP): Angle between the upper limb and the upper body – approximately 10°–24°
  5. Distance between the mouth and the eye (DME): The distance between the patient's mouth and the operator's eye – approximately 35–40 cm
  6. Operating light position (OLP): The light beam and the viewing direction should be parallel
  7. Instrument tray position (ITP): Distance between the operator's hand and the instrument tray – approximately 20–25 cm
  8. Foot position on the petal drive (FPPD): The position of the petal drive should be close to one of the dentist's foot.

Standardized photometric assessment method

SPAM, a novel technique developed specifically for the photographic documentation and analysis of dental ergonomic posture among the dental practitioners and dental hygienists was used in the current study. SPAM consists of three parts.

  1. Standardization of the photograph
  2. Standardization of the working posture
  3. Visual aids for comparison.

Standardization of the photograph

For the standardization of the photograph camera specification, position of the camera, background color, and lighting angle and types are standardized, which was modified from PADOC system given by Roos and Cederblom in 1991.[9]

  1. Camera specification

  2. The camera specification was kept the same for all the photographs. In the current study, the following specification was used in all the photographs taken.

    1. Make: Canon (Canon Inc., Ōta, Tokyo, Japan)
    2. Model: Canon EOS 700D
    3. Exposure time: 1/125 s
    4. ISO Speed: ISO-800
    5. F-stop: f/6.3
    6. Exposure bias: 0 step
    7. Focal length: 18 mm.

  3. Position of the camera [Figure 1]
Figure 1: Schematic representation of the two-camera position (position A and position B) at two different angle and distance

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A standard position of the camera must be used for all the samples. Two positions were currents used in the study.

Position A [Figure 2]: To observe the LA, HTA, SP, EP, DME, OLP, and ITP, the following measurements were used.
Figure 2: Camera placed at position A (30° and 10 feet away from the chair)

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  1. Distance from the Chair: 10 feet
  2. Angulation: 30°
  3. Height of the Tripod: 3.3 feet.

Position B: To observe the FPPD, the measurements used were

  1. Distance from the chair: 3 feet
  2. Angulation: 15° (lens facing the floor)
  3. Height of the tripod: 4.3 feet.

Background color: Green color was used in the present study

Lighting angles (if used): not used in the present study

Type of lighting such as color and make (if used): not used in the present study.

Standardization of the working posture

To standardize the working posture, photographs of all the 60 samples were taken while they were operating the same area with the same instruments and performing the same procedure. In the current study, the following were taken:

  1. Operating area: Mandibular anterior lingual surface
  2. Operating instrument: Ultrasonic scaler and supragingival scaler set
  3. Performing procedure: SGS.

Visual reference aids for comparison

To measure the angle and distance in the photograph, visual reference aids (VRA) (i.e., placards) are used. In the current study, two angle placards and two distance placards were used [Figure 3].
Figure 3: Sample pictures taken from position A, showing the four visual reference aids for comparison (two angle placard showing 90° and two distance placards showing 25 cm and 40 cm

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  1. Angle placard: Two placards showing 90° were placed in the frame. One 90° placard (straight) was used as a VRA for measuring SP, EP, and HTA. The second 90° placard (upside down) was used as a VRA for measuring LA
  2. Distance placard: Two placards showing 25 cm and 40 cm were placed in the frame. The 25 cm placard was used as a VRA for measuring ITP. The 40 cm placard was used as a VRA for measuring DME.

Six of the eight postures were analyzed using the VRA, as previously mentioned. OLP and FPPD were analyzed visually by checking the parallelism of the operative light and the position of the foot and the pedal drive, respectively [Figure 4]. All the eight postures were observed by the same observer to avoid interobserver bias and marked as either correct or wrong accordingly. The classification system introduced by Garbin et al.,[8] was used to score and interpret the obtained data [Table 1].
Figure 4: Sample picture taken from position B, showing the foot position on petal drive

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Table 1: Garbin et al. classification system for scoring dental ergonomic postures

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Statistical analysis

ANOVA and ANOVA test with the Bonferroni correction was used to statistically analyze the collected data. Statistical significance was set at P ≤ 0.05.

   Results Top

[Table 2] shows the percentage of correct and wrong posture for each year. The III year, IV year, and Intern students showed 53.3%, 53.3%, and 73.3% correct LA, respectively. More than 50% of students in III year and Intern showed correct HTA while IV year showed 60%. More than 90% of III year and Intern students showed correct SP while IV year showed only 70%. Correct SP was the highest among all the DEP analyzed in this study in all the three groups. On the other hand, the correct EP angle was lowest among all the DEP analyzed in the current study in all the three groups (III year – 3.3%, IV year and intern – 6.7%). The correct DME was between 20% and 45% in all the three groups (III year – 26.7%, IV year – 43.3%, and intern – 26.7%). Correct OLP was the second lowest among the DEP analyzed in all the groups (III year and intern – 6.7% and IV year – 16.7%). The correct ITP increased from III year to Intern (III year – 33.3%, IV year – 63.3%, and intern – 70%). The correct FPPD was 50%, 33.3%, and 53.3% in III year, IV year, and Intern, respectively.
Table 2: Percentage of correct and wrong posture followed by each year

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[Table 3] shows the percentage of the scores obtained by each group. The inadequate class was 16%, 20%, and 16% in III year, IV year, and Intern, respectively. In case of regular class, the percentage in each group was 66.6% (III year), 56.7% (IV year), and 53.3% (Intern). The intern group showed the highest percentage of satisfactory class (30%), followed by IV year, which was 23.3% and the lowest was III year with 16.7%. The excellent class was 0% in all the three groups.
Table 3: Percentage of the scores obtained by each group

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The mean value was calculated for all the three groups using the ANOVA test [Table 4]. P <0.005 was considered as statistically significant. The mean value for III year, IV year, and Intern was 2.00, 2.03, and 2.13, respectively. Although the mean increases from III year to Intern, it was not statistically significant (P = 0.709). ANOVA test with the Bonferroni correction was used to calculate the mean difference in all the groups [Table 5]. There was no statistically significant difference in all the groups.
Table 4: Mean values for all the three groups calculated using ANOVA test

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Table 5: Mean difference calculated using ANOVA test with Bonferroni correction

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   Discussion Top

WMSDs are considered as multifactorial in origin.[10] Hence, the methods to record the risk factors for WMSDs should include important exposure factors such as working postures, frequent movements, vibrations, and psychological stress in work place.[3] In the current method, only the postural variations were recorded as it is the most common risk factor in dentistry for WMSDs, and it can be corrected easily.[11]

Posturegram, developed by Priel in 1974, is the first observational method developed to analyze the basic working posture. Many numbers of simple observational techniques were developed for recording the workplace exposure factors which include Ovako working posture analysis system,[12] Rapid upper limp assessment,[13] National Institute for Occupational Safety and Health lifting equation,[14] and many more. Some of these techniques are also used for assessing workplace exposure related to dentistry, even though they are not specifically developed for dentistry. Unlike these methods, SPAM was specifically developed for dental clinics and be modified according to a specific need.

Advanced observational technique such as task recording and analysis on computer,[15] hands relative to the body,[16] portable ergonomic observational method,[17] and posture, activity, tools, and handling[18] were developed, which uses videotapes or computers with dedicated software to record and analyze real-time postural variations. Direct methods such as Lumbar Motion Monitor,[19] electronic goniometry,[20] inclinometers,[21] body posture scanning systems,[22] force measurements,[23] and CyberGlove[24] were developed to measure the workplace exposure directly using sensors. The main limitations of these methods are that they are expensive and time consuming, so not suitable for workplace assessments.[3]

In contrast to these studies, SPAM is relatively simple, less expensive, less time consuming, and can be performed in clinical setup without interfering with the clinical activities. The main advantage of SPAM is that it can be modified according to the need. In the current study, two positions were used, one to record the body posture of the clinician while operating, and another was used to record the position of the foot on the footrest. The main disadvantage of this method is the Hawthorne effect; the behavior of the research participants is influenced by the observation.[11] To overcome this problem, the camera with the tripod was set in the position for a week so that the students will get used to the experimental setting. The current analysis with SPAM showed that more than 69% of the students examined in all the three groups were under inadequate and regular which are high risk for WMSDs which was in accordance with a pervious study by Movahhed et al.[25] They used RULA to assess the natural working posture among 104 dental students and reported that 66% of them were at high risk of developing WMSDs and their postures need to be corrected.[25]

Partido BB and Wright BM gave a similar photograph-based self-assessment tool to record the ergonomic posture of the operator during dental procedure called Modified-Dental Operator Posture Assessment Instrument (M-DOPAI).[26] Unlike SPAM which examines 8 ergonomic postures, M-DOPAI examines 12 components, and a different scoring system was used for final analysis. SPAM uses a standardized method for recording the photograph which is not followed in M-DOPAI which might interfere with the outcome.

The main drawback of the current study is that the number of sample size was less, and the correlation between the posture followed by the students and any symptoms of WMSDs if present were not recorded, which would have been a more effective way of analyzing the SPAM technique. SGS has to be performed in all the parts of the mouth, and the posture of the operator changes for each and every area that has to be scaled.[27] In the current study, postures were analyzed when the students were scaling the lingual surface of the mandibular interiors only. This was done to standardize the posture, but for more appropriate analyzes of SGS, all the postures utilized by the student while doing full mouth SGS should have been photographed and analyzed.

   Conclusions Top

Within the limits of the current study, it can be concluded that the SPAM technique to assess the ergonomic posture of dental clinicians is simple and effective. It can be modified according to the need of the procedure. SPAM analysis of the dental students showed that most of them come under inadequate and regular category which are the high-risk factors for developing WMSDs. The ergonomic postures improved from III year to IV year but were not statistically significance. Further studies with a larger number of participants are required to check the efficacy of the SPAM in different treatment models and different specialties of dentistry.


We would like to thank Dr. Vinej Somaraj, Senior Lecturer, Department of Public Health Dentistry, Rajas Dental College and Hospital, Kavilkinaru Jn, Tirunelveli Dt., Tamil Nadu for statistical assistance. We would also like to thank Dr. Nivedha K for assisting in organizing the current study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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

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


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