Decoding the ergonomics in the new normal for dentistry: A narrative review

Overview of the human body

Corporal frame has been studied by artists, engineers, architects and medical practitioners throughout history. A Leonardo da Vinci’s -1490 creation- “The Vitruvian man,”^[14] ([Figure 2]) says it all. Our body is an intricate composite assembly, comprising the nervous system – governed musculoskeletal network.^[15] All the constituents; the organs, systems, tissues and cells are highly interdependent and work together to function as a whole. Presently, diseases like obesity, diabetes, cardiovascular disease, arthritis of joints, cancer is on the rise^[16] notwithstanding our ancestors had traditionally been hunters -cum- gatherers and so the body not designed to sit in one place.

MSDs in dentistry

The hand-operated tools are indispensable but rigorously using them leads to a cumulative isometric muscular contraction and in turn, repetitive stress injuries (RSI). Beyond doubt, dentists are retiring earlier due to the following:-

The ‘ergo-dontics’ was proposed recently^[18] to deter MSDs i.e. “work related disorders of the musculoskeletal system having chronic gradual onset involving muscles, tendons, ligaments, joints, nerves, cartilage and spinal discs”,^[19] which can lead to long term disabilities^[20] ([Table 1]) In the present context, pain and headache are predominant^[6], ^[18], ^[19], ^[21], ^[22] and significantly prevalent among the group who worked in direct vision, without assistant, in standing position or following none of the fitness regimen.^[23] Further based on the literature search, the risk factors for MSDs were chalked up as dental –related vs. general ([Table 2]). The classification was put forth by Das et al,^[22] in this regard. ([Table 3])

Dentists’ neutral position

It is believed that the more a joint deviate from the neutral position, the greater the risk of injury. The neutral position is the ideal positioning of the body while performing work activities^[24] for a proper blood circulation to the clinician's legs, thighs, wrists and feet. Accordingly, the weight is evenly balanced with forearms and thighs parallel to the floor, the hip angle is 90 degree; and operator chair is positioned low enough to be able to rest feet on the floor. ([Figure 3] a)

Neutral neck position ([Figure 3] b)

Head tilt of 0° to 15°

The line from your eyes to the treatment area should be as near to vertical as possible

Avoid neck flexed at >20°

Do not tip the head too far forward or tilt the head to one side

Neutral shoulder position ([Figure 3] c)

Shoulders in horizontal line

Muscles relaxed

Weight evenly balanced when seated

Avoid lateral twisting of head and neck

Avoid side- bending of neck

Do not sit with weight on one hip

Neutral back position ([Figure 3]d)

Clinician may lean forward slightly from the waist or hips

Trunk flexion of 0° to 20°

Avoid standing with back curved

Neutral upper arm position ([Figure 3]e)

Upper arms hang in a vertical line parallel to long axis of torso

Elbows at waist level are held slightly away from the body

Avoid upper arms lifted upward

Neutral forearm position ([Figure 3] f)

Forearms has to be held parallel to the floor

Raised or lowered, if necessary, by pivoting at the elbow joint

Avoid forming an angle between forearm and upper arm < 60°

Neutral hand & wrist position

Little finger should be slightly lower than the thumb

Wrist aligned with forearm

Avoid pronation (rotating the forearm and hand inward, so that the thumb and little finger are level)

Every clinician (irrespective of being right- handed or left- handed) who uses the dental chair has to adjust it in the right way - the one that will fit his own body. ([Table 4], [Table 5] ) When working on positions 9-12 (or 12-3 for the left- handed) split your legs apart so that the base of the seat and your legs form a tripod. That is the most balanced and stable position. ([Figure 3]g)

Education for dentists

It is no secret that ‘knowledge is power’ and a good education has the power to change a life. What is only required for this transformation is to know the time for that change. Although the theme of dentist posture is treated with great care and often presented in the undergraduate courses and the continuing education courses, many dentists do not know the subject well enough nor the theoretical issues and therefore nor the practical applicability.^[25] A periodic inspection of specific clinical procedures incorporating the upcoming principles should be devised for dental teachings in the modern era. A diagnostic feedback on phantom jaws should be analyzed after certain time lest the noble field of ours becomes outdated.

Ergonomics has formed an integral aspect of dental education at the University of British Columbia since the early 1980s. However, studies continued to indicate that dentists are at risk for developing musculoskeletal problems. This provided the impetus for a study of the risk factors associated with these problems.^[26] Emphasis on teaching the biomechanical principles of instrumentation, positioning simulation, appropriate relaxation techniques followed by practical application of the principles at the clinical level, may help lessen developing musculoskeletal symptoms among dental and dental hygiene students. These may include specific training on reducing peak pinch force during SRP and relaxing the pinch grip between tooth areas.^[9]

It was necessary to have a realization of dental ergonomics in Bulgaria until 2007, when it became a section in reformed curriculum to qualify as a public dental health worker.^[27] The same was revised and has been restructured continually since then for final year students in more ways than one.^[9]

Physical ergonomics

The posture refers to the manner in which different parts of the body are located,^[25] meaning to appropriately use the patient and dentist chair, or establishing correct method of instrumentation. The proper workstations may include comfortable edges of work surfaces, lumbar, thoracic or arm support in dentist’s chair, ([Figure 4]) adequate lighting, proper ventilation,^[29] and pleasant temperature.^[30] From using light weight and textured instruments to hollow handle and 3/8 inch in diameter^[24] and syringes of adequate lumen size;^[22] all are practically advantageous. Studying a lighter instrument with a wider diameter; Dong et al,^[31] said that it required the least pinch force; and Rempel et al.^[32] believed that it reduced the upper-extremity pain. The light weight vibration handpiece with swivel mechanism and built- in light source, has an edge over the conventional types.

Cognitive ergonomics

Dentists appreciate that human mouth is a relatively small space in which to operate. Considering the size of the available instruments (burs, handpieces, etc.), magnifiers were explored among dental hygienists.^[33], ^[34] When Ludwig et al,^[33] in their study subjected twenty-seven healthy hygienists to calculus identification on chair- mounted typhodonts, a clear majority found it worth using and modifying it further.

Next to come were the Ergonomic microscopes, which according to the oral pathologists, not only improves workability, but reduces eye and back strain; and can have reproducible results.^[35] Microscopes were repeatedly used as low (3x-8x) and medium(8x-16x)^[36], ^[37] to uncover details which are otherwise impossible. However, the subtle color variance between secondary and tertiary dentin in teeth with calcific metamorphosis requires a high (16x-30x) magnification. The current trend is Four-handed dentistry (FHD) i.e., two hands each of dental assistant and dentist when integrated with these gadgets. FHD, as a whole significantly enables the operator to remain in a prolonged static posture,^[38] thereby avoiding the extreme of the ergonomic motions hypothesized by Carr et al,^[39] which involves twisting or bending.

Organisational ergonomics

A Tehran study revealed that the multifaceted intervention, with a focus on improving working conditions, identifying ergonomic risk factors and discussion group meetings, could decrease the prevalence of musculoskeletal disorders in dentists.^[40] The exemplar below gives a coherent explanation of ergonomics in the modern dental set-ups. ([Figure 5]).

Yoga and stretching exercises

Yoga is defined as an ascetic discipline embracing distinct bodily postures(asanas), breath control and simple meditation. The activity meant for both prevention and rehabilitation, influences pain perception and is used for relaxation.^[41] Bhujangasan, padma sanasarvangasana, matsyasana, vipareetakarani mudra and pranayama are particularly relevant. Regular body Strengthening, stretching, relaxation techniques help improve the quality of life.^[42] The unequivocal systemic reviews^[43] and meta-analyses^[44] have expressed the issue explicitly. Although, the Telephysiotherapy digital sessions^[8] and acupressure^[45] have shown promise, but exercises and chair-side stretches are imperative to prescriptions for musculoskeletal insults;^[46] the same are illustrated below. ([Figure 6]) Remember to hold for two to four breath cycles while performing the above all. No wonder the little change in our lifestyle can make a huge difference in the way we can escape this health hazard which is gulping the entire dental fraternity worldwide, like a monster.^[41]

Risk of bias

The data from the studies of Padhye et al^[9] and Rempel et al^[32] were flawless. Whilst former reported the use of a set of Gracey curettes, the latter used custom-designed instruments for performing SRP in patients. But the fact that manual dexterity varies amongst the subjects, is a potential source of error for force and/ or pain assessment. Risk of statistical bias was present in the studies of Saxena et al^[23] and Dehghan et al.^[40] The latter reported the use of randomisation techniques and stated that they used a paired t‐test to compare differences in prevalence. However, in the data tables they stated that they used repeated ANOVA test. Majority of reviews and clinical demonstrations have hitherto provided definite limitations. Further studies with a larger sample size that would increase the statistical power and be representative of age, gender, ethnicity and race more realistically should be undertaken.