Practice Related to Ergonomics: A Cross-Sectional Study Among Dentists Practicing in the Private Sector

1. Introduction

The dental profession is widely affected by musculoskeletal disorders (MSDs), which cause pain in different parts of the body (Bonanni, 2022; Brown, 2010; Chenna, 2022). In a study conducted by Altaş and al, 54% to 93% of the dentists suffered from MSDs due to their practice (Altaş, 2022). In 2023, we carried out a study among dentists working in the private sector in Agadir, Morocco. The results showed that 100% of dentists reported at least one musculoskeletal complaint. 57.5% of our study population reported a change in work frequency as the main consequence of their MSDs (Brown, 2010).

Several factors may lead or contribute to the appearance of MSDs, such as psychological stress, lack of physical activity, pathological changes in the musculoskeletal system (Pope-Ford, 2020; Valachi, 1939). Numerous studies have highlighted the correlation between poor working postures adopted by dentists and MSDs (Pope-Ford, 2020; Custódio, 2012; Benkiran, 2018; Sakzewski, 2014). Various parameters can influence working posture, including workplace equipment, choice of instruments, practices, patient positioning, lighting conditions (Pîrvu, 2014; Dable, 2014).  

Due to these constraints related to the nature of the dental work, ergonomics has received particular attention. The principles of ergonomics play an important role in the organization of all medical fields including dentistry. Ergonomics was introduced to improve working conditions in the dental practice (Dable, 2014). It is focused on various concept, such as the working posture of dentists, the position of their patients, the arrangement and the way of using instruments, the organization of the working environment and the impact of all of these factors on the dentist’s health. It therefore acts by reorganizing interventions and procedures for maximum comfort and safety in in the workplace, limiting and simplifying movements, and rationally using the available surface area (Valachi, 2003). In ergonomics, working posture is the way in which different parts of the body are positioned, establishing relationships between them that enable the execution of a specific task. In dentistry, the working posture is represented by the spatial arrangement of the dentist's body around the patient (De Sio, 2018). There is currently a growing demand for ergonomic studies assessing dentists' knowledge of ergonomic work posture and comparing this with the reality of their daily practice in order to better understand their suffering (Pîrvu, 2014; Dable, 2014; Valachi, 2003; De Sio, 2018). Our aim in this study is to evaluate the knowledge and practices in terms of ergonomics among dentists practicing in the private sector in the city of Agadir.

2. Subjects and Methods

To meet our objective, we conducted a descriptive cross-sectional study between May 2022 and January 2023 in the city of Agadir, Morroco. permission to participate in the study was obtained from each dentist prior to data collection.

The list of dentists practicing in the private sector in the city of Agadir was obtained by contacting the National Dental Council by email. The list included the names, addresses and telephone numbers of the 234 dentists in the city. The same eligibility criteria applied in the first part of the work were used in this study to select participants (Benfaida, 2024). As in the previous study, participants registered with the National Dental Association and accepting to participate in the survey were selected. A total of 234 dentists were selected, of which 57.3% were female and 42.7% were male. All age groups were represented. The average age of dentists was 38.96 years (+/-10.5). Practitioners under 35 represented 43.2% of our population.

Data were collected using a questionnaire comprised 19 closed questions relating to dentists' knowledge and practices in terms of dental ergonomics. The questionnaire was developed using data from the literature. The anonymous questionnaire took around 10 minutes to complete.

The questionnaires were distributed and collected by visiting dental offices. Practitioners were given one to two weeks to complete the questionnaire. The names of practitioners who returned questionnaires were progressively deducted from a pre-established list of all the city's practitioners, in order to ensure proper follow-up of responses.

Results were compiled and statistically analyzed using SPSS software at the Epidemiology and Research Laboratory of the Faculty of Dentistry, Casablanca.

3. Results

Of the 234 participants, 206 responded. The results of the study concerning ergonomics and its application in dental practices were obtained. The results show that dentists do not correctly respect working posture. The most affected regions by musculoskeletal disorders in our previous work are the same areas whose posture is not respected by the participants. Only the posture of the feet was respected by 74.8% of participants, while the posture of the remaining limbs doesn’t exceed 50% for the back, 18.9% for the arms, 21.4% for the hands and forearms, 27.2% for the knees and 31.1% for the legs. 84.5% of dentists report having enough space in the treatment room to work ergonomically. 48.5% of dentists sometimes adjust the position of the stool and 44.2% have invested in an ergonomic stool. 79.6% of participants "Always" adjust the position of the patient chair before the treatment. (Table 1).

Other ergonomic errors related to the instrument tray organization, the use of indirect vision, operating lights, optical aids or magnification accessories and operating aids were noticed (Tables 2,3,4,5 and 6):

Table 1: Ergonomics of the treatment room

Table 2: Results for the organization of the worktray

Table 3: Results for indirect vision, luminosity and optical aids

Table 4: Results for operating aids

Table 5: Results for pauses between patients and stretching exercises

Table 6: Results for factors preventing compliance with ergonomic rules

4. Discussion

We conducted a cross sectional study in Agadir city in order to assess the ergonomics practices. During data collection, we were confronted with a number of difficulties, such as the absence of certain dentists, the refusal to participate in the study, and the reluctance to share certain personal information. We must also take into account when interpreting the results of dentists' subjective assessment of work posture, since the ergonomic data were reported by dentists using closed-ended questions. Despite these difficulties and limitations, our work presents certain strengths, namely, an exhaustive survey of the city of Agadir with 88.04% as participation rate. The questionnaire we used in this survey represents a synthesis of the various proposals in the literature. The questions used were validated in the literature, and we added other sections to ensure the most complete version possible of the questionnaire.

In a previous study on the same population, we found that 100% of dentists in Agadir reported at least one musculoskeletal complaint (Benfaida, 2024). In the same study, we showed that the presence of musculoskeletal pain in our population could be explained by several factors, including obesity, physical inactivity, type of professional activity and number of years of dental practice. In this work, our objective was to assess practical ergonomic knowledge in the same population. The results of our survey highlighted a number of shortcomings that explain the prevalence of MSDs found:

For the surface area of the treatment room, the rules of ergonomic posture according to Custódio are rarely respected in small treatment rooms (Custódio, 2012). Benkirane et al have shown that the surface area of a treatment room without a desk should be a minimum of 9 square meters, with the ideal being 12 square meters. If the room includes an office, the minimum surface area is 12 square meters, and the optimum 15 square meters (Benkiran, 2018). 84.5% of dentists in our study replied that they had enough space to work ergonomically, we weren't able to investigate all the treatment rooms in the dental offices to be sure of the surface area.

For the dental stool adjustment, only 39.3% always adjust the position of the stool, and only 44.2% have invested in an ergonomic stool. The correct use of an ergonomic stool makes a major contribution to the adoption of a balanced posture (Sakzewski, 2014). The height adjustment of the stool is necessary for the correct orientation of the lower limbs. If the stool is too high, the dentist's weight is poorly distributed, tilting towards the edge of the seat. As a result, dentist's back loses contact with the back of the stool, and there is a risk of loss of balance and slipping. On the other hand, too low stool adjustment reduces the natural lumbar curvature of the spine due to posterior rotation of the pelvic region (Pîrvu, 2014). A stool with a horizontal seat can cause posterior rotation of the pelvic region and a reduction in lumbar curvature. In addition, the horizontal base is wide with hard edges, which can lead to compression of the thighs and disruption of blood circulation. A saddle seat, or a seat inclined within a range of 5° to 15° to prevent slippage, avoids these phenomena by positioning the trunk and thighs at an angle greater than 90°. They also allow closer proximity to the patient and therefore better visibility (Pîrvu, 2014). A study carried out in India on 90 dental students showed that students suffering from musculoskeletal pain reported an improvement in their symptoms after 3 months' use of horse-saddle stools (Dable, 2014). Back support is considered to be essential to avoid muscle fatigue and reduce lumbar curvature during long procedures (Valachi, 2003). Another study demonstrated that back support does not influence the postural behavior of dentists (Dable,2014). For long clinical procedures, the manual support of the stool can prevent back pain and increased tension in the shoulders and neck. However, stools with this type of support are often avoided by practitioners, as they take up more space and restrict the doctor's movements (Pîrvu, 2014).

Several authors highlight the importance of the adjusting of the dental patient chair (De Sio, 2018; Hill, 1986; Kroemer,1986). Kroemer and Hill have shown that when the back and head are straight, the preferred downward angle of vision is 29° to the horizontal. Postural muscle fatigue occurs when this angle reaches 45° or more. The higher the patient's height, while respecting the minimum eye-to-object distance, the more the practitioner will raise the head, thus avoiding flexion of the spine (Hill, 1986; Kroemer, 1986).   

Instruments should be positioned correctly. Ideally, if the dentists want to search an instrument, he should only move his arm horizontally or vertically, without compromising the balanced posture. The further apart the instruments are, the more extreme the movements required to grip them. The most frequently used instruments should therefore be positioned close to the practitioner (Pîrvu, 2014; HAMEL, 2013). Araùjo et al. conducted a study of dental students in Maranhão, Brazil and found that 77.3% of students kept instruments close to their hands during work (Custódio, 2012).

For the compliance with ergonomic posture rules, the dentists' self-assessment of their own posture revealed several postural errors:

·       Back posture: The back should be straight with respect for body symmetry to avoid C-rounding of the spine. Only 50% of participants keep their backs straight. In Poland, the spinal alignment of 40 female dentists was examined using a SonoSens ultrasonic measurement system. The results found that all subjects exceeded the norms in various segments of the spine. A correlation was observed between the severity of the dentists' back pain and the values of parameters assessed in the frontal plane of the lumbar section and the transverse plane of the thoracic and lumbar sections (Nowotny-Czupryna, 2018). A similar study in the Netherlands assessing the posture of 1,250 dentists showed that 89% adopted a forward-flexing posture exceeding the accepted postural limits of 20°-25° (Santana Sampaio, 2021). Araùjo et al. showed that only 52.3% of dental students in Maranhaõ, Brazil, maintain a straight back during treatment (Araújo, 2021). A similar study carried out among students and interns at the Faculty of Dentistry in Bhopal, India, showed that 70.5% put themselves in a cervical flexion position to gain better visibility (Munaga, 2013).

·       Arm posture: The arms should be positioned 10 cm from the body. Only 18.9% respected this postural rule. A study of 5th year dental students in Casablanca showed that 25% respected this ergonomic rule (Benkiran, 2016).

·       Hand and forearm posture: forearms should be perpendicular to the arms, and hands should be in line with the arms. Only 21.4% comply with these two postural rules. Dentists are most affected by disorders of the hand and wrist, the pain engendered can result from numerous musculoskeletal disorders, principally carpal tunnel syndrome (Gupta, 2013). The polyarticular muscles of the forearm respond to the tenodesis effect. This effect creates an extension of the fingers when the wrist is flexed, and vice versa. This tenodesis effect is a risk factor for rheumatological pathologies of the forearm, wrist and hand. When the hand is not in line with the forearm, and the wrist is flexed, this creates difficulty in holding instruments correctly, and requires much greater effort from the finger flexor muscles (HAMEL, 2012).

·       The distance between the practitioner's eyes and the patient: The eyes must be located 50 cm from the oral cavity. The minimum distance between the patient's mouth and the practitioner's eyes is 25cm for a normal eye. Below this distance, the precision of vision decreases (HAMEL, 2012). In our study, 28.2% of dentists complied with this rule. In Maranhão, Brazil, a similar study showed that 61.4% of students positioned their eyes at approximately 25cm from the oral cavity and 38.6% at approximately 40cm (Munaga, 2013). In the literature, the main errors confirmed are extreme forward tilting of the head and over-stretched neck, tilting and rotation of the trunk to one side, raising one or both shoulders and adopting an increased curvature of the thoracic spine (De Sio, 2018).

For the indirect vision only 24.3% of dentists "always" use indirect vision. A study among dental students and interns in Bhopal, India, showed that 76.6% prefer working with direct vision (Munaga, 2013). Nachemson has shown that when the dentist leans forward by flexing the trunk, this causes increased intradiscal pressure on the discs. The 3rd or 4th lumbar disc has to bear a weight of 180 to 230 kg in this position. It is therefore essential to avoid leaning forward to work, for example, with direct vision of the maxillary teeth. For the operating lights, 57.8% of dentists adjust it according to the dental sector concerned. The intensity ratio between operating room lighting and general treatment room lighting should be between 3 and 1.6 (Partido, 2020). The scialytic should be oriented in such a way that the light beam is parallel to the direction of observation, thus maintaining shadow-free illumination with a good distance between the light and the patient's mouth (Munaga, 2013). The use of corrective glasses and magnification accessories such as magnifying glasses or microscopes helps prevent excessive torsion and tilting of the dentist's head (Pîrvu, 2014). 64.6% of dentists in Agadir have invested in it. Microscopes have the advantage of reducing working distance, and above all, their angulation reduces flexion of the spine, enabling the dentist to maintain a comfortable eye position (HAMEL, 2012).

For operating assistants, 84% were "always" helped by an assistant during treatment. In Poland, a study conducted by Kierklo et al. showed that only 63.6% of dentists work without a dental assistant (Kierklo,2011). The dental assistant plays an important role in reducing the practitioner's repetitive movements and improving posture (De Sio,2018). Dentists need to get used to working with a dental assistant from their clinical training years onwards.

Dentists must take breaks between dental treatments. In our population, only 67.5% of the dentists took "Sometimes" breaks between patients and 54.2% estimated 5 min as a maximal duration of breaks. Kierklo et al. found that among 220 Polish dentists, only 8% took a break after each patient. 36.4% were satisfied with just one break during the working day (Kierklo, 2011).

Performing stretching exercises after each treatment session and at the end of the working day has been described as the most effective measure for preventing musculoskeletal disorders. 52.9% of the dentists in our study "never" did stretching exercises during their breaks. It is well known that the prolonged static posture adopted by dentists during treatment requires the contraction of 50% of the body's muscles. To reduce this muscular tension, slow, gentle, pain-free stretching exercises for a minimum of 15 to 30 seconds, were recommend 2 to 3 times a day (De Sio, 2018).

Concerned the factors preventing the participants from complying with ergonomic rules, we found that the main obstacles were: difficulty of operating procedures (73%), time (53.9%) and unsuitable equipment (28.6%). A similar study among the 5th-year dental students at the Casablanca Faculty of Dentistry showed that the main factors preventing students from complying with ergonomic rules were time (69.4%), unsuitable equipment (67.6%) and the difficulty of surgical procedures (42.6%) (Benkiran,2016). The continuing dental education programs treating dental ergonomics are mandatory to motivate dentists to follow ergonomic rules. Mohan Kumar P et al. conducted a comparative study among dental students in three different dental schools and found that the knowledge and practice scores of dental students were increased after applying ergonomic-related instructions than before in all the three different colleges of all the year students (Munaga, 2013).

The results of our study confirmed that there is a strong correlation between the musculoskeletal disorders observed in our population and the deficiencies observed namely:

Ø  Failures in the organization of the work-space (the adjust of the stool, the operating lights, dental instruments tray…)

Ø  Failure to respect back posture, position of arms, hands and forearms and lower limbs, distance between practitioner's eyes and patient

Ø  The non-use of indirect vision

Ø  Lack of investment in ergonomic equipment such as stools and optical aids...

Ø  Continuous work without taking breaks between dental treatments

5. Conclusion and future perspectives

Our study has shown that compliance with the various ergonomic posture rules among dentists in the private sector in the city of Agadir is deficient. This result explains the alarming rate of practitioners reporting at least one musculoskeletal complaint. To prevent the observed shortcomings, we propose:

·       To integrate of work ergonomics into continuing education cycles to raise dentists' awareness of the impact of ergonomics on career longevity and dental office productivity.

·       To provide frequent reminders on work ergonomics and in particular work posture for dental students during their clinical training years by planning seminars and round tables discussions.

·       To conduct observational studies in order to assess the posture’s errors of dentists more accurately using RULA/REBA charts filled in by researchers, or by taking photos/videos or using motion recording sensors to identify errors more accurately.

·       To conduct studies to better understand the role of professional activity and the layout of the dental practice in the development of MSDs.

·       To conduct comparative studies using the same protocol in other cities in our country, as well as in the student population of the Faculty of Dentistry.

Author Contributions: All authors contributed to this research.

Funding: Not applicable.

Conflict of Interest: The authors declare no conflict of interest.

Informed Consent Statement/Ethics Approval: Not applicable.