The Ergonomics of Dental Assisting: Preventing & Managing Work-Related Pain

Bethany Valachi, PT, DPT, MS, CEAS

March 2021 Course - Expires March 31st, 2024

American Dental Assistants Association

Abstract

All dental team members face physical challenges when delivering dental care, including sustained postures, awkward movements and repetitive motions. However dental assistants face a unique set of musculoskeletal challenges when working chairside: they are unable to position their knees under the patient, cannot freely re-position their chair to different “clock” positions, have difficulty viewing the oral cavity, and must frequently accommodate to the dentist’s positioning. Combined with poor operatory layout or delivery systems it is understandable why assistants report that their highest prevalence of musculoskeletal pain is in the low back.1,2 If dental professionals ignore regularly occurring pain or discomfort, the cumulative physiological damage can lead to an injury or career-ending disability.3 Knowledge of how physical damage occurs, proper body mechanics in the operatory, adjustment of ergonomic equipment and balanced musculoskeletal health can help assistants implement effective injury prevention strategies, make wise choices regarding ergonomic equipment and place of employment, improve quality of life and extend their careers.

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Ergonomics and the Dental Assistant

Ergonomics is the science of fitting jobs to the people who work them. The goal of an ergonomics program is to reduce work-related pain and injuries when a major part of the worker's job requires reaching, bending over, awkward positions, continuous force or repetitive motions. As it applies to dental assisting, ergonomics involves the design of operatory layouts, delivery systems, stools, and procedures that minimize excessive reaching, gripping, twisting and leaning.

Some jobs require workers to intermittently deviate from their optimal posture throughout the workday. Unfortunately, in dental assisting, frequent rotation often occurs repeatedly to one side, which can result in muscle imbalances and pain.4,5

Additionally, assistants are often required to hold one posture for prolonged periods of time, which may cause painful myofascial tightness and muscle ischemia.6 Therefore, an effective dental ergonomics program requires therapies aimed at the human body: frequent chairside stretching, specific exercise and myofascial work to develop and maintain balanced musculoskeletal health.

Implementing ergonomic and injury prevention techniques into the workday will mean less likelihood of fatigue, job burnout, musculoskeletal disorders and better morale.

CTDs in Dental Assisting

Cumulative trauma disorder (CTD) is a term that refers to many common diseases that affect the soft tissues of the body. A cumulative trauma disorder results from the accumulation of microtrauma that happens in the body at a rate faster than the body can repair it, thus causing a soft tissue disorder in the body. These disorders are considered to be work-related when the work environment and the performance of work contribute significantly to the development of a multifactorial disease.7

The most frequently reported CTD among assistants is chronic low back pain.1,2 Other common sites of pain include the neck, shoulders (right more than left), legs, arms and hands. Left untreated, this pain may result in muscle imbalances, ischemia, nerve compression and joint or disc degeneration.

Warning signs and symptoms of a CTD include:

• Decreased strength (example: gripping strength in assistants)

• Decreased range of motion (example: neck rotation in assistants)

• Pain or burning

• Shooting or stabbing pain into an arm or leg

• Swelling or inflammation

Maintaining optimal musculoskeletal health for dental assistants means understanding the unique muscle imbalances to which they are prone and how various working postures, positions, adjustment of ergonomic equipment and exercise can positively or negatively affect their musculoskeletal health.

Contributing Factors to CTDs

The causes of work-related musculoskeletal pain can be attributed to numerous risk factors, including prolonged static postures; non-neutral postures; repetitive movements; visual challenges; and mental stress.8-10 Each dental team member is predisposed to pain or injury in slightly different areas of the body depending on his or her tasks and positioning in relation to the patient. For example, assistants are predisposed to a higher incidence of low back pain, largely due to holding a position for a prolonged period with arms extended, repeated forward and side-leaning postures. Over time, these postures can lead to microtrauma, or damage that is occurring on such a small scale, the assistant does not feel it until the cumulative structural damage results in pain. The body is constantly repairing this micro-trauma, however if breaks are infrequent, the rate of damage can exceed the rate of repair. Pain or an injury may result.

Three primary types of microtrauma inherent to dental assisting are muscle imbalances, muscle ischemia and increased disc pressures. To better understand the microtrauma, we will briefly review spinal anatomy.

Spinal Anatomy and Microtrauma

The spine has three movable curves when viewed from the side. (Fig. 1) When the curves of the spine are present and balanced against the center of gravity (i.e. ear, shoulder, hip and ankle in alignment), the spine is supported mostly by the bony structure of the vertebrae resting on top of one another. In this position there is less stress on the surrounding muscles, ligaments and discs and microtrauma is lessened.

Muscle Ischemia

When these curves become flattened (Fig. 2) or the spine is bent to one side (Fig. 3), the spine depends increasingly on muscles, ligaments, disks and soft tissue to remain erect. As posture deviates from neutral, the muscles must contract harder to maintain working posture. This increased stress can cause muscle ischemia. When a muscle is constantly contracted for a prolonged period, the pressure inside the muscle rises and can occlude blood flow to the muscle. When muscles don't receive the needed oxygen and nutrients, and lactic acid cannot be removed, painful muscle ischemia can occur.11

This oxygen deficiency also lowers the effective working level of the muscle. Even in optimal seated posture, more than 50% of the body's muscles must contract to hold the body motionless while resisting gravity.12

Muscle Imbalances

Prolonged leaning postures (Fig. 3) can lead to muscle imbalances. Muscles on one side of a spine or joint become tighter and stronger, while muscles on the other side become longer and weaker (Fig. 4). Over time, these imbalances may hold the spine in improper alignment not only in the operatory, but outside as well. In assistants, a functional scoliosis may develop, where the spine is curved to one side as a result of constant leaning in the operatory.13

These asymmetrical forces on the spine can cause misalignment of the spinal column and loss of range of motion in one direction over the other. Nerve compression and spinal disc degeneration can result.

Increased Disc Pressure

Microtrauma can also result from the increased disc pressures in seated postures. When seated, pressure in the low back spinal discs increases by 40 percent over pressure from standing. When sitting, leaning forward and rotating, a position often assumed by dental assistants, the pressure increases to 400 percent,14 making the structure vulnerable to injury. Over time, repeated forward bending can weaken the wall of the disc, resulting in a bulging, or herniated, disc, which can cause low back, buttock or leg pain.

Safe Postural Working Range

One goal of an ergonomics program is to maintain the most neutral posture possible. Viewed from the side, neutral posture is ear, shoulder, hip and ankle vertically aligned (Fig. 1). Viewed from the back, the spine is straight. The more posture deviates from this neutral position, the greater the strain on muscles, discs, ligaments and joints. When assistants stand during assisting, they can stay fairly closely to this ideal neutral posture. (Fig. 5A) However, when seated, it becomes extremely challenging to maintain this posture, and excessive forward and side-leaning postures to one side are frequently observed, which are a potent combination for low-back pain. This is why the assistant should familiarize themselves with the safe ‘limits', or a safe postural working range in which they should strive to operate. Based on the research, working with the neck bent forward greater than 20 degrees is a risk factor for neck pain. Assistants will find that working with ergonomic dental magnification loupes with a steep declination angle will enable them to stay within this range.17 (Fig. 5B) Likewise, the hip angle should be open greater than 90 degrees. Assistant stools with a tilting seat pan or a saddle style stool enable this positioning. Arms should be lifted away from the sides no more than 20 degrees and reach forward no more than 25 degrees.19

The assistant should frequently use the torso support bar to support their arm weight, when making transfers, suctioning, etc. Assistants should avoid reaching across their mid-line with the right arm, as this creates a great deal of strain in the right shoulder and neck.

The assistant also faces the challenge of not being able to easily change clock positions around the patient. Due to these positioning challenges, assistants should seize every opportunity to change their posture and move. Alternating between sitting, standing and chairside stretching is imperative to the assistant's musculoskeletal health.20

The Seated Assistant

An area of great controversy for the assistant is use of the dental assisting stool. Specially designed assistant stools have been around for a long time. The unique features of these stools are supposed to increase comfort and help support assistants while they work. The stool should help stabilize the assistant without impairing movement, or inhibiting access to the patient. The variety of features can make the selection process confusing.

Dental assisting stools vary in design: those with torso support bar only, both backrest and a torso support bar, and saddle style stools. Seat pans differ in size and shape. It is probably due to the variety of assistant stools and positioning challenges, that such a wide array of seated postures are observed among assistants. Unfortunately, many of these postures contribute to CTDs. Table 1 lists the most common seating errors and their impact on musculoskeletal health.

First and foremost, operating within the safe postural working range and using the body properly should be a priority during dental assisting. To achieve this, the seated assistant must implement both mechanical and physical stabilization.

Physical Stabilization

The assistant cannot maintain neutral vertical spinal posture at all times during treatment. Whenever posture deviates from neutral, stabilization must come from within. The deep transverse abdominal muscles wrap horizontally around the trunk and attach in the low back. When strong, these muscles help stabilize and maintain the low back curve and have been shown to help reduce low back pain.21,22

Therefore, the assistant should learn how to physically stabilize the trunk with these muscles whenever the body is in an unbalanced posture (i.e. leaning forward or reaching), as well as target these muscles in a home exercise program. In the operatory, this can be achieved with the following exercise:

Dental Operator Pivot

Sit tall on the stool. Exhale, and actively pull the muscles below your belly button backward toward your spine. Your transverse abdominal muscles are now helping to maintain your low back curve. (One common mistake is to suck one's breath in to pull the spine toward the navel. You should still be able to talk, breathe and move while holding this contraction.) Assume a relaxed working position with your arms, and using your hips as a fulcrum, pivot forward at the hips, maintaining the contraction throughout the exercise. Strive to make this Operator Pivot exercise a habit throughout the workday - anytime you must leave a neutral sitting posture - to stabilize the lumbar spine and help reduce lower back pain.20

Mechanical Stabilization

Due to the postural challenges of seated dental assisting, mechanical stabilization is helpful in reducing muscle strain. External stabilizing of the spine may be accomplished with an ergonomically designed dental assisting stool. The most important ergonomic features on different assistant stools include:20

• Torso Support Bar: This is a mandatory feature on an assistant stool. The torso support bar should function as both an armrest and torso support. It is critical that the assistant take the time to adjust the height of the support bar to just below elbow height so the weight of the arm is fully supported when sitting upright. If assistants of different heights use the same stool, they must take the time to re-adjust the height of the torso support bar between patients. The torso support bar should adjust inward toward the assistant for optimal trunk support. (Fig. 2) This inward adjustment is achieved with either a ratcheting torso support bar or one that pivots inward. Older torso support bar models that swing in a circle around the edge of the stool cannot be adjusted inward to provide proper trunk support at the side of smaller assistants. This forces assistants to sit on the edge of their seat to utilize the support bar. These styles of stools should be replaced with more ergonomic styles.

• Backrest: This is an optional feature on some assistant stools. When properly adjusted, a backrest can help support the lumbar curve and prevent back pain.23

• Tilting Seat: Most assistant stools with a backrest have a seat that tilts forward. When properly tilted forward, this feature can help maintain the low back curve, reduce disc pressure, decrease muscle strain, and prevent back pain.24 The seat should be angled very slightly forward (5-15 degrees) so thighs slope slightly downward.

• Saddle Seat: By design, a saddle stool seat naturally places the pelvis in a neutral position, thereby promoting the body's natural lumbar curve, and reducing strain on the lumbar muscles and discs. Adding a backrest to a saddle stool further decreases muscular effort.25 Never angle a saddle seat forward! The author recommends only the narrowest (see Resources: Equipment Recommendations) saddle seats for assistants who side-sit next to the patient, due to the slightly rotated postures assistants frequently must assume. Because it opens the hip angle and allows closer positioning to the patient, this stool may be used either directly facing the patient or with assistant's hip at patient's shoulder.

• Footring: The footring provides stabilization for the assistant when it is properly adjusted. This is an important safety feature, as the assistant sits higher than the dentist and does not have the floor to provide stabilization.

Adjusting the Assistant Stool

It is imperative that if assistants of varying heights and sizes are using the same assistant stool, they take the time to re-adjust it prior to each procedure. The torso-support bar, foot ring, and/or backrest may all need to be adjusted, depending upon the physical differences between assistants. Adjust the stool as follows: (For stools without a backrest, skip all steps marked with an asterisk*)

1. Backrest*: Adjust the backrest height until it nestles comfortably in the low back curve. Then angle the backrest away from you.

2. Checking seat depth: Sit all the way back on the seat. Test for proper seat depth by placing 3 fingerwidths behind the back of the knee. If there is not enough room to easily move 3 fingerwidths between the back of the knee and edge of the seat, the seat pan is too deep, and the assistant should select an assistant stool with a shorter seat pan. (Some manufacturers make a special stool for taller/larger assistants and a special stool for shorter/smaller assistants. See Resources: Equipment Recommendations.)

3. Seat tilt/Backrest*: Most assistant stools with a backrest and torso support bar have one lever to adjust both the seat tilt and the backrest. Adjust the seat tilt forward until the thighs slope slightly downward, while bringing the backrest forward to snugly support the low back.

4. Saddle stool seats: Always position a saddle stool seat flat. Never tilt a saddle stool seat forward-even if it has this function-unless you have a congenital spinal deformity. Unlike conventional seats, saddle stools place your pelvis in a neutral position, so no seat tilt is needed.

5. Footring: Adjust the foot ring height to firmly support the feet with thighs angled slightly downward. Note: Non-adjustable, flat assistant seats will not allow ergonomic seating with thighs angled downward.

6. Torso support bar height: With the arm relaxed, and elbow at 90 degrees, adjust torso support bar height so it snugly supports the assistant's armweight without pushing the shoulder upward.

7. Torso support bar placement:

a. Stools with backrest: Torso support bar angles across the front of the body. Adjust the torso support bar across the front of the body, so the assistant is ‘sandwiched' snugly between the torso support bar and backrest. (Fig. 22)

b. Stools without backrest: Torso support bar swings freely around the periphery of the stool, and also can ratchet or glide inward toward the center of the stool. Sitting in the center of the seat, place the middle of the torso support bar at the assistant's side. Adjust the bar inward toward the side of the assistant to fit snugly against the torso under the ribs. The end of the bar should be only slightly in front of midline of the torso and provide enough bar support behind the assistant to rest the back. (Fig. 23)

8. Height: Adjust the height of the chair so assistant's eye level is four inches to six inches above the dentist's eye level.

Assistants may need to raise the stool slightly higher with treatment of the lower arch. Shorter assistants working with tall doctors may find their stool will not adjust high enough. If the cylinder won't raise high enough, consider purchasing a different model. Unlike operator stools, which are frequently available in multiple cylinder heights, manufacturers typically offer only one height cylinder for their assistant stool, however this height varies widely among manufacturers, ranging from about 27 inches to 34 inches.

Seated Assistant Positioning

To maintain neutral posture, the assistant must be seated close enough to the oral cavity to avoid forward leaning. Traditionally, the assistant has been taught to sit with their left hip at the patient's left shoulder, and knees angled toward the patient's head. (Fig. 7A) This positioning requires a significant degree of trunk rotation.

An inter-locking knee position enables the most neutral posture for the assistant during procedures. (Fig. 7B) However, some dentists and assistants may be uncomfortable with this amount of contact. Overcoming this hesitancy requires professionalism and communication between the dentist and assistant regarding the goal of this positioning, which is to preserve the health of the assistant and deliver quality patient care.

Saddle stools may allow the closest positioning, as the hips are angled more sharply downward. Saddle stools may be positioned angled as in 7A or 7B (narrow seat saddle only) and they are the only assistant stool that may be positioned facing the patient. (Fig. 7C)

Additional Positioning Considerations

The assistant is highly prone to developing right-sided neck and shoulder pain. This is usually due to frequent reaching across the assistant's mid-line with the right arm. At times, this may be difficult to avoid, however using the left arm as a fulcrum can greatly reduce the musculoskeletal strain associated with this positioning. The assistant must also remember that they do not always need to be watching the suction area. Once the suction is properly placed, the assistant should periodically sit up straight to give the body a rest.

The shape of the patient chair can also impact the assistant's posture. Wide "wings" on a patient chair prohibit the assistant from positioning the stool close to the patient, causing unsafe side-leaning. Some patient chairs can be retrofitted with a smaller pedo backrest to allow closer positioning to the oral cavity.

The Standing Assistant

As mentioned previously, the assistant is less able to move around the head of the patient and is most vulnerable to the damaging effects of prolonged, static postures. Assistants should therefore try to stand for up to half of treatment time. Alternating between standing and sitting moves the workload from one group of low-back muscles to another and may help reduce low-back pain.12,26

Keep in mind that the assistant should still be four inches to six inches above the dentist's height-even when standing. Certain height combinations will work better for this than others. A medium or tall height dentist and shorter assistant is the most ideal, since the assistant won't have to bend over while standing. If the dentist is too tall, the assistant can stand on a short platform to raise their height. (Fig. 8)

Perhaps the worst combination for standing is a short dentist and tall assistant. One way to make this work from an ergonomic standpoint is for both the dentist and assistant to stand. The assistant should still remember to perform the dental operator pivot in standing (pivoting at the hips) whenever leaving a neutral upright posture is necessary. Again, effective communication between dentist and assistant can help each attain better posture and positioning.

Assistant Delivery Systems

The most common ergonomic mistake observed with assistant delivery systems is positioning them too far away, causing excessive leaning, reaching and half-sitting on the dental stool (one foot on the floor and one foot on the footring). This posture is can be very damaging, and should be avoided at all costs.

All of the most frequently utilized handpieces, instruments and other equipment must be within fingertip reach, without leaning. The instrument tray is best positioned directly in front of the assistant, preferably extending over the assistant's lap.

One type of assistant delivery is on a fixed counter at the 1 o'clock position. These are frequently located too far away from the assistant and cause excessive reaching. If instruments are out of comfortable reach, try swiveling the patient chair 10 degrees to 20 degrees counter-clockwise. This may place the assistant closer to the delivery system.20 (Fig. 9) A better solution when utilizing a fixed counter, it is to mount the assistant's work surface on a swiveling tray on a long arm that swings out in front of the assistant, over the knees. Over-the-patient delivery systems should be placed as high on the patient's chest as possible, to prevent the assistant twisting backward to retrieve handpieces.

Another type of delivery is a mobile cart (a unit on wheels) that can move freely in the operatory. Mobile units are often an effective, inexpensive modification for operatories with ample room in the 1:00 position. Mobile carts often solve positioning problems, as they can be moved to the desired position in the operatory. Assistants should be able to position their knees easily under their delivery system.

Dental Delivery Systems

Both rear delivery and over-the-patient dental delivery systems are designed for the assistant to be fully utilized, meaning the assistant should be making all instrument and equipment transfers, as well as changing burs on handpieces. Unfortunately, many doctors do not receive training in dental school on how to utilize an assistant. Because the most popular style of delivery on the market today is rear delivery, many dentists repeatedly twist to one side to retrieve their own instruments, handpieces and change burs. Such twisting has been shown to lead to low back pain. With rear delivery systems, the assistant should always strive to do all instrument transfers and change burs on all handpieces-not only to ensure the doctor's health, but also to boost productivity!

Side delivery systems minimize the help the assistant can provide for the doctor, as the assistant cannot reach the handpieces, which are located on the doctor's side of the patient.

Lighting

Sometimes the assistant is expected to adjust the overhead light in the operatory during procedures. Two theories exist for overhead lighting. The newest guideline states that the overhead light should parallel the dentist's line of sight as closely as possible to reduce shadowing and provide optimal viewing of the oral cavity. To attain this, the overhead light will need to be slightly behind and to one side of the dentist's head. In this case, the dentist will need to adjust the light themselves, as the assistant cannot reach it in this position. However, most dentists are not taught this newer lighting guideline in dental school, and still use the decades-old standard of positioning the light over the patient's mouth for lower arch and angled up over the chest for the upper arch. In this case, it is incumbent upon the assistant to ask the doctor if they would like the assistant to adjust the light during the procedure, or if the doctor would prefer to adjust it themselves. If the light is difficult to pull along a track or to adjust, contact the manufacturer. Constant pulling on a stiff light can cause shoulder problems.

Hands and Gloves

Because hand and wrist discomfort is common among assistants, they should alternate between palm and pen grasps to avoid overworking one area of the hand and wrist. Gloves should be fit loosely across the palm and around the wrist, and snug in the fingers. Glove that fit too tight may cause pain at the base of the thumb. This is easily resolved with fitted gloves, which are molded in a working hand position. There is also one style of ambidextrous glove on the market that is ergonomic and reduces muscle strain (see Resources). Hoses on handpieces should also be long enough so excessive force is not necessary while working.

Positioning the Patient

It is frequently the job of the assistant to position the patient for the dentist prior to the procedure. Regardless, the assistant should be aware of how the patient chair and headrest operate. For maxillary procedures, it is generally recommended the patient be in a full supine position; for mandibular procedures, the semi-supine position.

The position of the headrest can have a significant impact on visibility into the oral cavity, and therefore on the doctor and assistant postures. For maxillary procedures, a double articulating headrest should be angled steeply downward, so the patient's occiput is comfortably supported and the occlusal plane is behind the vertical. This places the upper arch at the best angle for the doctor and assistant to preserve their most neutral working postures.20 (Fig. 11) For flat headrests without an articulation, have the patient move all the way to the end of the headrest and insert an ergonomic dental neck cushion to lift the chin. Use of an ergonomically designed dental neck cushion (see Resources) dramatically improves patient compliance by improving comfort. Generic neck pillows and rolled up towels are generally counter-productive as they are too large and push the patient's head forward and down, worsening viewing of the upper arch. For mandibular procedures, the double articulating headrest should be angled forward.

The Assistant as Operator

The assistant that functions in both assisting and sole operator roles has the advantage of varying their working positions and is therefore less prone to overstressing one part of the body.

Seating considerations for the assistant in the sole operator position are somewhat different than those in assisting. Close proximity to the patient is an important and often difficult factor for the operator. The operator stool should be adjusted in a similar manner as the assistant stool with backrest, ensuring the seat is tilted slightly forward to help gain closer positioning to the patient. A saddle stool with backrest is the most ideal seating solution for the assistant working alone. The assistant's forearms should be approximately parallel with the floor, elbows relaxed at the sides. The assistant should strive to properly position the patient for upper and lower arch as described previously, and work mostly in the 11-12 o'clock positions.20

Magnification

Properly adjusted dental loupes can reduce muscle strain in the neck and upper back by promoting proper neck and shoulder posture.17,28 Two general styles of scopes are available, through-the-lens and flip-up styles. The TTL, or through-the-lens, style is mounted directly in the lens, is non-adjustable, and generally has a poor declination angle. Flip-up style scopes have the steepest declination angle, hence promoting the most neutral head posture.

From a musculoskeletal standpoint, the declination angle of the scopes is the most important consideration. The declination angle is how steeply the scopes are angled downward toward the oral cavity. A good declination angle will allow the assistant to work with a more upright, neutral head and neck posture (Fig. 7C and Fig. 13).28 Selecting a larger frame size will allow the manufacturer to place the scope lower in the frame, enabling the best declination angle, and, hence the best neck posture. Although generic magnifying reading glasses are less expensive and improve visibility, they have no declination angle and therefore frequently result in poor head posture.

Another important factor to consider when purchasing loupes is working distance, which is the distance from the operator's eye to the working area. Since the assistant sits higher than the doctor, their working distance is usually siginificantly longer than the doctor's working distance. Measure the working distance in your own operatory, if possible, with arms relaxed at your sides and forearms approximately parallel to the floor. For assistants, a magnification of 2.0X - 2.5X is recommended.

Exercise

Due to their susceptibility to low back pain, assistants should maintain excellent endurance of specific trunk stabilizing muscles that have been shown to help reduce low back pain (transverse abdominal, oblique abdominal, multifidus and quadratus lumborum muscles).29 There are many ways to strengthen these muscles. The transverse abdominal muscles may be strengthened by lying on the floor, pulling the navel to the spine and holding it throughout the exercise while alternately lifting one leg, then the other off the floor (Fig. 14) or in quadruped while pulling navel to the spine, as in the Point Dog exercise (Fig. 15). The quadratus lumborum can be strengthened in side-lying (Fig. 16) and the multifidus and paraspinals can be strengthened extending over a ball (Fig. 17). Instructions on how to safely perform all four exercises are at www.posturedontics.com. Since dental professionals are prone to unique muscle imbalances (see video in Resources), generic exercise regimens should be carefully modified to prevent worsening of pain syndromes.

The above are guidelines only. As with all exercise, always consult your physician before beginning any strengthening or stretching programs.

Aerobic fitness is also important for assistants, since muscles become oxygen-deprived and ischemic during the prolonged, static contractions required in dental assisting. Aerobically fit individuals become much efficient at delivering oxygen to muscles and repairing ischemic tissue.

Self Managing Pain

Awkward, prolonged postures, muscle ischemia and mental stress can lead to myofascial tightness and painful trigger points in dental assistants.30 Regularly taking the time to treat this can go a long way in extending the assistant's career.

1. Trigger point treatment. Self-treating your trigger points with a small ball or trigger point tool (Backnobber) should be done daily. (Fig. 18) Specific guidelines for treatment can be found in the Resources section.

2. Foam rolling. Reducing myofascial tightness and mobilizing the vertebrae can effectively be done on a foam roller. The author prefers ‘The Grid' foam roller over styrofoam cylinders, which can be very hard and somewhat painful to roll on. Foam rolling should be done daily to reduce myofascial tension. (Fig. 24)

3. Chairside Stretching. Even with the best assisting stool and techniques, the assistant will intermittently have to leave optimal posture. When this occurs, it is usually toward one side, predisposing the assistant to muscle imbalances. The assistant should regularly perform chairside stretches that reverse these potentially harmful postures (i.e. primarily away from the patient).20 Make sure you are stretching the correct muscles. You want to be stretching muscles that are short, tight and ischemic, not elongated, weak muscles (see Resources). It is important to know how to stretch safely:

• Move into and out of a stretch slowly. This insures you won't overstretch and encourages relaxation of the nervous system.

• Breathe in and exhale slowly as you increase the stretch to a point of mild tension or discomfort.

• Hold stretch for 2-4 breathing cycles.

• Never stretch in a painful range.

Three examples of stretches for the trunk are shown in Figures 19-21. Stretches that target the neck, shoulder and hand/wrist are also important for assistants to perform.

4. Stress management. Mental stress can elevate the sympathetic nervous system, making it more sensitive to pain.31 Implementing relaxation therapies, monitoring stress and meditation techniques can go a long way in controlling stress-induced pain.

5. Weight control. For every 10 pounds of abdominal weight the assistant carries, it translates 100 pounds of force to the low back. Since assistants are already prone to low back pain, so weight control is essential to preventing low back pain.

Summary

Proper selection and adjustment of equipment, correct positioning, and learning about balanced musculoskeletal health can all contribute to preventing pain and injuries in dental assisting. Diligently implementing evidence-based ergonomic strategies in the operatory and at home can help ensure a long, comfortable and satisfying career in dental assisting.

GLOSSARY

Double articulating headrest - headrest on a patient chair that adjusts in multiple planes to optimally position the patient for treating either the upper or lower arch.

Flat headrest - headrest on a patient chair that is non-adjustable, and only slides in and out.

Fulcrum - a point of rest about which an object turns.

Ischemia - decreased oxygenation and cell death due to a mechanical obstruction of the blood supply.

Ligaments - a band of strong tissue connecting bones.

Multi-factorial - having more than one cause.

Mechanical stabilization - stabilization provided by a source external to the body.

Muscle imbalance - a muscle on one side of a spine or joint becomes stronger and shorter, while the opposing muscle becomes weaker and longer. This condition often results from repeated asymmetrical postures.

Microtrauma - structural damage to the musculoskeletal system occurring on a microscopic scale, that is usually not felt in the beginning stages.

Myofascial - the muscle and the network of connective tissue surrounding and connecting the muscle.

Occiput - refers to the occipital bone, the back part of the head.

Over-the-patient delivery system - a type of delivery system that is positioned directly over the patient's chest.

Physical stabilization - stabilization that is provided by the body's internal postural muscles.

Postural stabilizing muscles - muscles located close to the spine that function primarily to stabilize the body in upright posture for long periods of time.

Ratcheting arm - bar on an assisting stool that adjusts inward toward the center of the chair, and does not swing just around the periphery.

Rear-delivery system - a type of delivery system that is located behind the patient's head.

Scoliosis - a lateral curvature of the spine, to the left or right, which may be congenital (from birth) or functional (due to work-related postures).

Saddle stool - an assistant stool with a seat shaped similarly to a horse saddle.

Spinal disc - fibrous discs located between each vertebrae that allow movement of the spine.

Tendons - a fibrous cord or band that connects a muscle with its bony attachment.

Torso support bar - a bar on an assisting stool that adjusts inward, and serves as both an armrest and to stabilize the trunk.

Transverse abdominal muscles - the deepest group of abdominal muscles, which provide stabilization to the spine.

SUGGESTED RESOURCES

Dental Ergonomic Resources

Valachi, B. Assistant stool and dental loupes recommendations: www.posturedontics.com/equipment-recommendations/

Valachi, B. Muscle Imbalances in Dental Professionals video. https://posturedontics.com/educational-videos/

Valachi, B. Evidence-based Home Exercise and Chairside Stretching DVDs for dental professionals, trigger point therapy tools, articles, webinars and videos. Portland, Oregon 2017. Available at: www.posturedontics.com.

Crescent neck cushions - www.posturedontics.com

Finkbeiner B. Four-handed Dentistry: A hand- book of Clinical Application and Ergonomic Concepts. Prentice Hall. New Jersey 2001.

Self Managing Pain

Egoscue P. Painfree: A revolutionary method for stopping chronic pain. Bantam Publishing 2000.

Davis/Eschelman/McKay The Relaxation & Stress Reduction Workbook. New Harbinger Publications 2008.

The GRID foam roller - www.tptherapy.com

Davies, C. - The Trigger Point Therapy Workbook: Your self-treatment guide for pain relief, 3rd Ed. New Harbinger Publications 2013.

Novak J. Posture, Get it Straight! The Berkeley Publishing Group. New York

REFERENCES

1. Lalumandier J, McPhee S, Parrott C, Vendemia M. Musculoskeletal pain: Prevalence, prevention, and differences among dental office personnel. General Dentistry 2001; March/April.

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ABOUT THE AUTHOR

Dr. Bethany Valachi, PT, DPT, MS, CEAS

Dr. Bethany Valachi is author of the book, "Practice Dentistry Pain-Free", clinical instructor of ergonomics at OHSU School of Dentistry in Portland, OR and lectures internationally on the topic of dental ergonomics. For over 20 years, Dr. Valachi has helped thousands of dental professionals prevent pain and extend their careers with her relevant, evidence-based dental ergonomic education and consultations. She has published more than 60 articles in peer-reviewed dental journals and offers dental ergonomic educational materials and virtual coaching on her website at www.posturedontics.com.

Figure 1 – The human spine in balanced posture. (©2017 Posturedontics, LLC)

Fig. 1

Figure 2 – Forward bending posture

Fig. 2

Figure 3 – Side leaning posture

Fig. 3

Figure 4 – Muscle imbalance

Fig. 4

Figure 5A & B – Optimal standing and seated postures for the dental assistant.

Fig. 5

Figure 6A – Torso support bar only
Figure 6B – Backrest and torso support bar
Figure 6C – Saddle stool with torso support bar

Fig. 6

Figure 7A – Traditional seated position of assistant

Fig. 7A

Figure 7B – Ideal interlocking knee position of assistant

Fig. 7B

Figure 7C – Saddle stool position facing patient

Fig. 7C

Figure 8 – When standing, the assistant may use a short platform to raise their height

Fig. 8

Figure 9 – Proximity to delivery/chair swivel

Fig. 9

Figure 10 – Assistant performs all transfers with rear delivery systems.

Fig. 10

Figure 11 – Double articulating headrest position with cushion

Fig. 11

Figure 12 – Assistant operator posture

Fig. 12

Figure 13 – Loupes with good declination angle

Fig. 13

Figures 14 – Exercises to prevent low back pain in dental assistants

Fig. 14

Figures 15 – Exercises to prevent low back pain in dental assistants

Fig. 15

Figures 16 – Exercises to prevent low back pain in dental assistants

Fig. 16

Figures 17 – Exercises to prevent low back pain in dental assistants

Fig. 17

Figure 18 – Self-treating trigger points with a Backnobber tool

Fig. 18

Figures 19-21 – Chairside stretches for dental assistants; (Left to Right) Overhead stretch; The reversal, Trunk rotation

Figures 19-21

Figure 22 - Stool with backrest

Fig. 22

Figure 23 - Stool without backrest

Fig. 23

Figure 24 – Grid foam roller

Fig. 24

Table 1

Table 1

Take the Accredited CE Quiz:

CREDITS: 3 SI
COST: $48.00
PROVIDER: ADAA
SOURCE: American Dental Assistants Association | March 2021

Learning Objectives:

Upon completion of this course, the dental professional should be able to:
• Describe how ergonomic principles apply to dental assisting.
• State the primary Cumulative Trauma Disorder (CTD) to which dental assistants are susceptible and explain how this CTD occurs in dental assisting.
​• Recognize the warning signs of developing CTDs.
• Describe neutral posture of the spine, shoulder and wrist.
• Describe proper positioning of the assistant in relation to the patient and doctor.
• Demonstrate proper use and placement of the torso support bar.
• Identify important features of assisting stools and how to properly adjust them.
• Describe proper positioning of the patient in the chair using flat and double articulating headrests.
• Explain proper and improper placement of delivery systems and instrument trays and how these can affect the assistant’s musculoskeletal health.
• Identify 3 strategies to self-treat myofascial tightness and prevent pain.
• List four important muscle groups to strengthen to stabilize the trunk and prevent back pain.

Disclosures:

The author reports no conflicts of interest associated with this work.

Queries for the author may be directed to jromano@aegiscomm.com.