Preventing Musculoskeletal Disorders (MSDs) in Clinical Dentistry

2003;134;1604-1612 J Am Dent Assoc

BETHANY VALACHI and KEITH VALACHI disorders

mechanisms leading to musculoskeletalclinical dentistry: Strategies to address the Preventing musculoskeletal disorders in

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C L I N I C A L P R A C T I C E

1604 JADA, Vol. 134, December 2003

Background. The authors reviewedstudies to identify methods fordental operators to use toprevent the development ofmusculoskeletal disorders,or MSDs.Types of StudiesReviewed. The authorsreviewed studies thatrelated to the prevention of MSDs among dental operators. Somestudies investigated the relationshipbetween the biomechanics of seatedworking postures and physiological damageor pain. Other studies suggested thatrepeated unidirectional twisting of thetrunk can lead to low back pain, while yetother studies examined the detrimentaleffects of working in one position for pro-longed periods. Additional studies con-firmed the roles that operators’ flexibilityand core strength can play in balancedmusculoskeletal health and the need foroperators to know how to properly adjustergonomic equipment.Results. This review indicates thatstrategies to prevent the multifactorialproblem of dental operators’ developingMSDs exist. These strategies address defi-ciencies in operator position, posture, flexi-bility, strength and ergonomics. Educationand additional research are needed to pro-mote an understanding of the complexity ofthe problem and to address the problem’smultifactorial nature.Clinical Implications. A comprehen-sive approach to address the problem ofMSDs in dentistry represents a paradigmshift in how operators work. New educa-tional models that incorporate a multifacto-rial approach can be developed to helpdental operators manage and preventMSDs effectively.

Preventing musculoskeletal disorders in clinicaldentistryStrategies to address themechanisms leading to musculoskeletal disorders

BETHANY VALACHI, M.S., P.T., C.E.A.S.; KEITH VALACHI, D.D.S.

Second in a two-part series on the musculoskeletal health of dental professionals

Dental operators often cannot avoid prolongedstatic postures, or PSPs. Even in optimalseated postures, more than one-half of thebody’s muscles are contracted statically, andthere is little movement of the vertebral

joints. This may result in damaging physiologicalchanges (microchanges) that can lead to back, neck orshoulder pain or musculoskeletal disorders, or MSDs(macrochanges).1

In this article, we provide a briefreview of spinal anatomy and the biome-chanics of sitting postures. This willprovide a clearer understanding of howdamaging physiological changes occurand enable operators to apply preven-tion strategies both in and out of theoperatory.

THE NATURAL SPINAL CURVES

In standing postures, the spine has fournatural curves when viewed from the

side: cervical lordosis, thoracic kyphosis, lumbar lor-dosis and sacral kyphosis (Figure 1).2 The curves areinterdependent; a change in one curve will result in achange in the curve above or below it.3 Since the sacralcurve is composed of five fused vertebrae, its movement

In optimalseated

postures, more than

one-half of thebody’s musclesare contracted

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is extremely limited. However, the remainingcurves—especially the lumbar and cervicalcurves—are more mobile and can be influencedmore easily. When the curves of the spine arepresent and balanced against the center ofgravity, the spine is supported mostly by the

Copyright ©2003 American Dental Association. All rights reserved.


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bony structures of the vertebrae resting on top ofone another. When these curves become eitherexaggerated or flattened, the spine increasinglydepends on muscles, ligaments and soft tissue tomaintain erect.

When sitting unsupported—a frequent posturein dentistry—the lumbar lordosis flattens (Figure2). The bony infrastructure provides little supportto the spine, which now is hanging on the mus-cles, ligaments and connective tissue at the backof the spine, causing tension in these structures.Ischemia can ensue, leading to low back strainand trigger points. This flattening of the lumbarcurve also causes the nucleus in the spinal disk tomigrate posteriorly toward the spinal cord. Overtime, the posterior wall of the disk becomes weak,and disk herniation can occur. Therefore, opera-tors need to know about strategies they can use tomaintain the essential lumbar lordosis wheneverpossible.

Maintaining the cervical lordosis in the properposition is equally important. Forward-head pos-

tures are common among dentists, due to years ofpoor posture involving holding the neck and headin an unbalanced forward position to gain bettervisibility during treatment (Figure 2). In this pos-ture, the vertebrae no longer can support thespine properly, and the muscles of the cervicaland upper thoracic spine must contract con-stantly to support the weight of the head in theforward posture.4 This can result in a pain pat-tern, which often is referred to as tension necksyndrome. This syndrome can cause headachesand chronic pain in the neck, shoulders and inter-scapular muscles, and it occasionally can radiatepain into the arms. Sustained contraction of cer-vical muscles also causes weakening of the spinaldisks, with possible disk degeneration or hernia-tion.5 Therefore, frequent relaxing and stretchingof the neck muscles, strengthening of the deeppostural cervical muscles and preservation of thecervical lordosis in proper posture (ear over theshoulder) with all activities, including sleepingand driving, is essential for optimal muscu-

JADA, Vol. 134, December 2003 1605


Figure 1. The four primary curves of the spine: cervical lordosis, thoracic kyphosis, lumbar lordosis and sacralkyphosis. Adapted with permission of the publisher from Saunders and Saunders.2



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loskeletal health of the neck.A forward-head posture also can lead to muscle

imbalances,1 contributing to a rounded shoulderposture. This posture can predispose the operatorto impingement of the supraspinous tendon in theshoulder (rotator cuff impingement) whenreaching for items. Additionally, static posture ofthe arms in an elevated or abducted state of morethan 30 degrees impedes the blood flow to thesupraspinous muscle and tendon.6,7 Prolongedarm abduction also can lead to trapeziusmyalgia—chronic pain and trigger points in theupper trapezius muscle.

To effectively prevent injuries in dentistry, pre-vention strategies and ergonomic techniquesmust address these postural and positioning diffi-culties, as well as subsequent detrimental physio-logical changes: muscle imbalances, stiff joints,muscle necrosis and spinal disk degeneration.

POSTURAL AWARENESS TECHNIQUES

Maintain the low back curve. Research showsthat maintaining the low back curve—the lumbarlordosis—when sitting can reduce or prevent lowback pain (Figure 3).8,9 The following practices

can help maintain the low back curve.dTilt the seat angle slightly forward five to 15degrees to increase the low back curve.10 This willplace your hips slightly higher than your kneesand increase the hip angle to greater than 90degrees, which may allow for closer positioning tothe patient. Chairs without the tilt feature can beretrofitted with an ergonomic wedge-shapedcushion.dSit close to the patient and position kneesunder the patient’s chair if possible. This can befacilitated by tilting the seat and using patientchairs that have thin upper backs and headrests.For some operators, this positioning may causeshoulder elevation or arm abduction. In suchcases, a different working position should beassumed.dConsider using a saddle-style operator stoolthat promotes the natural low back curve byincreasing the hip angle to approximately 130degrees. Using this type of stool may allow you tobe closer to the patient when the patient chairshave thick backs and headrests.dAdjust the chair so your hips are slightlyhigher than your knees and distribute yourweight evenly by placing your feet firmly on thefloor. The forward edge of the chair should notcompress the backs of your thighs.dUse the lumbar support of the chair as muchas possible by adjusting the lumbar support for-ward to contact your back.dStabilize the low back curve by contracting thetransverse abdominal muscles. To do this whilesitting, sit tall with a slight curve in the low back,exhale, pull your navel toward the spine withoutletting the curve flatten. Continue breathingwhile holding the contraction for one breath cycle.Repeat five times. Strive to maintain this stabi-lization regularly throughout the workday.dPivot forward from your hips, not your waist.Stabilize the low back curve by performing theprevious exercise before pivoting forward.

Use magnification. Proper selection, adjust-ment and use of magnification systems have beenassociated with decreased neck and low backpain, as they allow operators to maintainhealthier postures.11 Keep the following in mindwhen choosing and using a magnification system.dOperating telescopes or loupes are availablewith flip-up or through-the-lens designs. Thedeclination angle of the scopes should allow youto maintain less than 20 degrees of neck flexion.Working in postures with greater than 20 degrees



Figure 2. The effects of poor posture on the curves of thespine: flattened lumbar lordosis and a forward-head position.



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chairs on display at dealer showrooms or in theworkplace. Many manufacturers and dealersallow for in-office trial periods, enabling operatorsto evaluate which model best suits their needs.

POSITIONING STRATEGIES

Avoid static postures. According to Lehto andcolleagues,13 the concept of a single correct workposture may be physiologically invalid, as thehuman body may be made for movement andever-changing postures.

Some dental schools and educational programsstress the importance of using one “home” posi-tion while working. While it is important to useergonomically correct positions and postures,some studies suggest that several home positionsmay be better than one.9,14,15 Spending longperiods in static positions increases a worker’s



of neck flexion have been associated withincreased neck pain.12 You should try severaloperating telescope models to determine whichsuits your needs and fits you best.dThe working distance should allow you tomaintain optimal posture, with your shouldersrelaxed and your elbows close to your sides.dMagnification of ×2 will allow you to seeworking field detail that is approximately iden-tical to that you would see when hunching overthe patient without scopes. Magnification greaterthan ×2 provides enhanced visual detail but asmaller field of vision.dOperating microscopes allow for the highestmagnification of available systems with thegreatest operating detail and promote the mostneutral postures by design.

Adjust operator chair properly. Accordingto Chaffin and colleagues,10 the era when sittingwork posture problems were solved by simply pro-viding a chair is over. Operators need to knowhow to adjust the features of their chairs toobtain maximal ergonomic benefits.dAdjust your chair first. A common mistakeoperators make is positioning patients first, andthen adjusting their chairs to accommodate thepatients. Allowances can be made when workingwith patients who are elderly or disabled.dPosition the buttocks snugly against the backof the chair. The edge of the seat should not con-tact the backs of the knees. A seat that is too deepcan encourage you to perch on the edge of theseat.dPlace feet flat on the floor and adjust the seatheight up until thighs gently slope downwardwhile the feet remain flat on floor. This helpsmaintain the low back curve and enables you toposition your knees under the patient moreeasily.dMove backrest up or down until the lumbarsupport nestles in the natural lumbar curve of thelow back. Then angle the lumbar support forwardto facilitate contact with the low back.dTilt the seat forward about five to 15 degrees.If you are beginning to work with the seat tiltfunction, start with a slight tilt and later increasethe degree of tilt as is comfortable.dAdjust armrests, which are designed todecrease neck and shoulder fatigue and strain, tosupport elbows in the neutral shoulder position.

There are many ergonomically designed oper-ator chairs available. Because of varied operatorbody sizes and needs, you should try out several

Figure 3. Maintaining the low back curve facilitatesproper posture and reduces pressure on disks andmuscles.



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instead of twisting the torso. Operators should tryto retrieve items with the closest hand, especiallywith rear delivery systems, to avoid twisting orreaching across the body. Repeated unilateraltwisting in one direction may result in muscleimbalances or structural tissue damage, leadingto low back pain.17,18

PERIODIC BREAKS AND STRETCHING

Chairside directional stretching. Studiessuggest that the increase in operator pain sincethe 1960s may be due to longer work periodswithout breaks, due in part to the use of four-handed dentistry techniques.14,19 Having opera-tors take frequent breaks20 and reverse theirpositions is integral in an effective injury preven-tion program.

It is difficult for most dentaloperators to avoid PSPs. In optimalPSPs, muscle ischemia and jointhypomobility can occur due to pro-longed muscle contractions. Whenassuming awkward PSPs, dentalprofessionals are predisposed todeveloping muscle imbalancescaused by repeatedly flexing for-

ward, bending to the side and rotating in onedirection. In general, dentists tend to lose flexi-bility in the direction opposite to that in whichthey are postured statically during the day.21

Stretches performed in the reverse direction ofawkward PSPs may prevent muscle imbalancesthat can lead to pain and MSDs. Directionalstretches can be performed in or out of the opera-tory and can be incorporated into a daily routinethat facilitates balanced musculoskeletal health.Directional stretching involves a rotation,sidebending or extension component that gener-ally is in the opposite direction of that in whichthe operator frequently works (Figures 4A-4D).This strategy addresses the muscle imbalancesthat tend to develop.

Frequent stretching breaks address the detri-mental physiological changes that can developwhile working in optimal or awkward PSPs:ischemia, trigger points, muscle imbalances, jointhypomobility, nerve compression and disk degen-eration. Furthermore, stretchingdincreases blood flow to muscles;dincreases production of joint synovial fluid;dreduces formation of trigger points;dmaintains normal joint range of motion;dincreases nutrient supply to vertebral disks;

susceptibility to injury due to the mechanisms wediscussed in a previous article.1 Increasingly, theliterature supports the idea that workers shouldvary their work positions as often as possible toshift the workload from one group of muscles toanother.6,9,10,14,15

Alternate between standing and sitting.Standing uses different muscle groups than doessitting; therefore, alternating between the twopositions lets one group of muscles rest, while theworkload is shifted to another group of muscles.Alternating between standing and sitting also canbe an effective tool in preventing injuries.15 Onestudy revealed that dentists who worked solely ina seated position had more severe low back painthan did those who alternated between standingand sitting.16

Reposition the feet. Subtlechanges in foot position can shiftthe workload from one group of lowback muscles to another, allowingthe overworked tissues to be replen-ished with nutrients.

Position patients at theproper height. A common mistakeamong dentists is positioningpatients too high. This causes elevation of theshoulders and abduction of the arms, leading toprolonged static muscular tension in the neck andshoulders. Magnification enables operators tomaintain a greater working distance and positionpatients at the proper height, with the shouldersrelaxed and the forearms approximately parallelwith the floor.

Operators should take the time to positiontheir patients properly for mandibular and maxil-lary procedures. Generally, patients should beplaced in a semisupine position for mandibularprocedures and a supine position for maxillaryprocedures.

Avoid twisting. Operatory design plays animportant part in how often dentists performdetrimental twisting movements during theworkday. Rear delivery systems encourage exten-sive trunk twisting and shift of vision to retrieveinstruments, and side delivery systems requiremoderate twisting. Transthorax (or over-the-patient) delivery systems minimize twisting andshift of vision. When possible, dentists shouldposition instruments within easy reach. If theoperatory design requires the dentist to turn toretrieve instruments or handpieces, the dentistshould swivel the chair to face the area squarely



A common mistakeamong dentists is positioning

patients too high.



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dcreates a relaxation response in the centralnervous system;dwarms up the muscle before beginning towork;didentifies tight structures that may be predis-posed to injury.

How to stretch safely. To avoid injuryduring stretching, keep the following tips inmind:dassume the starting position for the stretch;dbreathe in deeply;dexhale as you slowly increase the intensity ofthe stretch up to a point of mild tension or discomfort;dhold the stretch for two to four breathingcycles;dslowly release the stretch and return to neu-tral position;drepeat the stretch if time allows;davoid stretching in a painful range and discon-tinue stretching if it increases pain.dperform stretches in both directions to detectunilateral tightness (Figures 4A-4C illustratestretching in one direction only);dperform directional stretches primarily towardthe tightest side throughout the workday andperform the stretches in both directions at home.

Stretching during microbreaks. To preventinjury from occurring to muscles and other tis-

sues, the operator should allow for rest periods toreplenish and nourish the stressed structures. Ifthese breaks are too far apart, the rate of damagewill exceed the rate of repair, ultimately resultingin breakdown of tissue. According to Karwowskiand Marras,6 resting for more than 50 secondsdoes not result in an increased force-generationcapacity, or strength, of the muscles. This indi-cates that to optimize the strength capacity of theworker and minimize the risk of experiencingmuscle strain, following a schedule of brief, yetfrequent, rest periods would be more beneficial toworkers than would lengthy infrequent restperiods.

In a study on the efficacy of microbreaks duringthe workday, McLean and colleagues22 found thatby complying with regularly scheduled micro-breaks, the subjects had less discomfort and thatthe addition of 30-second microbreaks showed nodetrimental effect on worker productivity. Otherauthors have pointed to the efficacy of usingmicropauses and stretching during dental proce-dures.23-25 Stretches can be modified so that dentaloperators can perform the stretches easily atchairside, while wearing their gloves (Figure 5).Operators should perform directional stretchesregularly throughout the day, both in and out ofthe operatory setting. They also can benefit bywalking or performing other activities involving



A B C D

Figure 4. Examples of chairside directional stretches. A. Neck and shoulder combination. With the elbow at shoulderheight and at a 90-degree angle, gently pull the arm across the front of body with opposite arm. Look over theshoulder being stretched and hold for two to four breathing cycles. Repeat. B. The untwister. With the knees widerthan shoulder width, bend to the left side, resting the full body weight through the left elbow on the left knee. Stretchthe right arm overhead and look toward the ceiling. Hold for two to four breathing cycles. Repeat. C. Upper trapeziusstretch. Anchor the right hand behind the seat of the chair. Gently bring the left ear toward the left armpit. Hold fortwo to four breathing cycles. Repeat. D. Downward squeeze. Assume a neutral head posture (ears over the shoulders)and do not let the head move forward throughout the exercise. Lift the chest upward, position the arms at the sideswith fingers pointing upward and palms facing forward. Roll the shoulders back and down, squeezing the shoulderblades downward and together. Hold for one long breath cycle. Repeat five times.



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movement during longer breaks.Trigger points. Sometimes, operators may

experience pain that is not relieved withstretching but instead worsened by it. This painmay be caused by a sustained contraction inside atight band of muscle known as a trigger point,which feels like a small hard knot.26 When firmpressure is applied, trigger points are painful andmay refer pain to another area. They do not allowthe muscle fibers to contract or relax; therefore,they effectively decrease flexibility and reduceblood flow to the muscle. It is important thatoperators release trigger points as soon as pos-sible. Various people can help treat trigger points:da physical therapist trained in trigger pointtherapy, contract and relax technique or muscleenergy technique;da neuromuscular therapist;

da massage therapist trained in trigger pointtherapy;da physician trained in spray and stretch tech-nique or trigger point injection;dthe dentist self-administering trigger pointtherapy using a tennis ball or other small ballbetween the back and a wall or using a triggerpoint self-massage tool.27

STRENGTHENING EXERCISES

MSDs in dentistry often begin with fatigue of thepostural stabilizing muscles of the trunk andshoulders. As these muscles fatigue, operatorstend to slump into poor posture, setting the stagefor injuries. Dentists should perform specificstrengthening exercises for the trunk andshoulder girdle to enhance the health andintegrity of the spinal column, maintain good



Figure 5. Chairside stretching can be performed during breaks such as while waiting for anesthetic to take effect in thepatient.



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both variety and the benefits of cross-training.The results of a study assessing the muscu-loskeletal symptoms of dentists found that phys-ical exercise can be a buffer against musculo-skeletal ill health and stress for dentists over awide range of ages.13

Stress management. It generally is acceptedthat dentistry can be a stressful occupation.Stress can elicit muscular contraction and pain,especially in the trapezius muscle.29 Operatorsmay use various stress-reduction techniques todecrease stress-related muscular tension. Theyinclude breathing techniques, progressive relax-

ation, visualization, massage, aer-obic exercise, meditation or yoga.

EDUCATION

As professionals, dentists under-stand the concept of being lifelongstudents so they can maintain theirproficiency in clinical techniquesthat benefit their patients. To pro-tect their own health, dentists

should seek out and receive education about mus-culoskeletal health, injury prevention and dentalergonomics. Ideally, this education should beginduring dental school and continue through thedentist’s professional life.

One dentist, however, has found that injuryprevention and dental ergonomics education stillis in its infancy.25 Most dental practitioners havenot been trained in these areas, and they havenot developed the skills and knowledge necessaryto practice in a manner that is ergonomically cor-rect. This lack of training is due in part to theneed for more research and for better teachingtools and better-informed and -trained teachers.Part of the blame for the lack of training can beattributed to the magnitude of the task.

Dental operators can be taught to manage andprevent injuries effectively. They can educatethemselves and their staff members using a mul-tifactorial approach that includes preventive edu-cation, postural and positioning strategies, properselection and use of ergonomic equipment, andfrequent breaks with stretching and strength-ening techniques before painful episodes occur.Prevention strategies should be easy to use toensure long-term compliance.

CONCLUSIONS

Work-related pain is common among dental pro-fessionals. The development of four-handed oper-

working posture, optimize the function of thearms and hands and prevent injuries.

Areas to strengthen include the trunk stabi-lization muscles, primarily the transverse andoblique abdominal muscles and multifidus mus-cles; the stabilizing muscles of the shouldergirdle, mainly the middle and lower trapeziusmuscles; and the downward gliding muscles of therotator cuff, the infraspinous, subscapular andteres minor muscles. Dentists should avoid over-strengthening the chest and anterior neck muscu-lature, deltoid muscles and upper trapezius mus-cles, as this may exacerbate muscle imbalances towhich they are prone. Areas tostretch include the chest muscula-ture, hamstring muscles, low backmuscles, buttock (piriform) musclesand hip flexor (iliopsoas) muscles.This combination of strengtheningand stretching addresses a uniquepattern of muscle imbalances that can develop among dental professionals.

Guidelines for exercise. Certain guidelinesshould be observed when beginning any exercise program:dconsult a physician before beginning any exer-cise program;ddo not perform strengthening exercises forpainful or fatigued muscles;dbegin exercise gradually, starting with theminimum number of repetitions;dstop exercise immediately if numbness, tin-gling, dizziness or shortness of breath occurs;dperform strengthening exercises three to fourtimes per week and stretching exercises daily;dalways exercise in a pain-free range.

Aerobic exercise. Aerobic exercise should beperformed three to four times a week for at least20 minutes. One major contributing factor toMSDs is decreased flow of nutrients and oxygento muscles.1 Aerobic exercise increases blood flowto all of the tissues in the body and improvestheir ability to use oxygen. In addition, aerobicexercise improves cardiovascular and cardiorespi-ratory function, lowers heart rate and blood pres-sure, increases high-density lipoprotein (good)cholesterol, decreases blood triglycerides, reducesbody fat, improves stress tolerance, increasesmental acuity, improves sleep quality and mayincrease longevity.28 Operators should choose aer-obic exercises that they enjoy. It is advisable to doat least two types of aerobic exercise regularly, for



Aerobic exerciseshould be performedthree to four times a week for at least

20 minutes.



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atory techniqueshas madedelivery of dentalcare more effi-cient and pro-ductive; however,it also has con-tributed to anincrease in PSPsamong operators.Because thisproblem is multi-factorial, any possible solutionshould be multifactorial as well.

Available research supportsthe idea that this problem can be managed oralleviated effectively using a multifacetedapproach that includes preventive education, pos-tural and positioning strategies, proper selectionand use of ergonomic equipment and frequentbreaks with stretching and postural strength-ening techniques. This represents a paradigmshift for daily dental practice. It is important thatdentistry incorporate these strategies into prac-tice to facilitate balanced musculoskeletal healththat will enable longer, healthier careers;increase productivity; provide safer workplaces;and prevent MSDs. ■

Dr. and Ms. Valachi are co-founders of Posturedontics, a companythat provides continuing dental education courses on topics that areaddressed in this article.

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Ms. Valachi is a phys-ical therapist, a certi-fied ergonomic assess-ment specialist, andco-founder of Posture-dontics, Portland, Ore.

Dr. Valachi is in privatefamily practice, St.Helens, Ore., and is co-founder of Posturedon-tics, Portland, Ore.Address reprintrequests to Dr. Valachiat 2225 S.W. ScenicDrive, Portland, Ore.97225, e-mail“[email protected]”.



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Preventing Musculoskeletal Disorders (MSDs) in Clinical Dentistry

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