Dental Workers, Musculoskeletal CumulativeTrauma, and Carpal

INTERNATIONAL JOURNAL OF
OCCUPATIONAL SAFETY AND ERGONOMICS 1996, VOL. 2, NO. 3, 218-233
Dental Workers, Musculoskeletal
CumulativeTrauma, and Carpal Tunnel
Syndrome: Who is at Risk?
A Pilot Study
Valerie J. Rice
Bradley Nindl
United States A rm y Research
Institute of Environmental
Medicine, USA
John S. Pentikis
United States A rm y Center fo r
Health Promotion and Preventive Medicine, USA
A p ilot study was conducted at a dental clinic to identify (a) the prevalence of musculoskeletal
cum ulative traum a disorders (MCTD), (b) associated sym ptom s (with special attention paid to
carpal tunnel syndrom e [CTS]), and (c) practitioners at risk. Videotapes, tw o questionnaires, a
medical record review, and interview s w ere used. Forty-five dental workers participated and were
classified into three categories: (a) dentists, (b) dental assistants and special assistants (DA/SA),
and (c) dental hygienists and dental assistant-expanded function (DH/DAEF). Categorical data
were analyzed using the chi- square statistic and risk ratios. The Fisher exact probability test was
used fo r categorical data w ith a small cell. One or m ore sym ptom s associated w ith CTS were
noted by 75.6% o f the dental workers, 11% reported diagnosed CTS, and 53% reported back and
shoulder pain. Both psychosocial factors and jo b demands appear to be associated w ith MCTD.
A ll three categories o f dental workers reported MCTD sym ptom s, and the DH/DAEF group was
found to be at greatest risk fo r developing upper extrem ity sym ptom s, CTS, and back pain.
dental hygiene
occupational hazards
repetitive m otion disorders
ergonom ics
1. INTRODUCTION
Musculoskeletal cumulative trauma disorders (MCTD) are occupationally related neuromus­
cular disorders caused by repeated biomechanical stress and microtrauma (Putz-Anderson,
1988). Over time, repeated microtrauma can evolve into a painful, debilitating state and
involve muscles, tendons, tendon sheaths, and nerves. Repetitive motions, forceful exertions,
acceleration and velocity of dynamic motions, vibration, mechanical compression, sustained or
awkward postures, extreme temperatures, and extended exposure to noise can contribute to
the development of MCTD (Armstrong & Silverstein, 1987; Bammer & Blignault, 1987;
Marras & Shoenmarklin, 1991; Putz-Anderson, 1988). Tendinitis, tenosynovitis, bursitis, chronic
muscle strain, and nerve entrapment syndromes are examples of MCTD.
The U.S. Occupational Safety and Health Administration (OSHA) has reported a dramatic
rise in MCTD and other work-related injuries due to ergonomic hazards (OSHA, 1991). In
Correspondence and requests for reprints should be sent to Valerie J. Rice, Military Performance & Neuroscience,
United States Army Research Institute of Environmental Medicine, Natick M A 01760-5007, U SA . E-mail:
< Rice@Natick-ilcn.army.mil> •
218
DENTAL WORKERS: WHO IS AT RISK?
219
August 1990, OSHA began a nationwide program to help decrease worker exposure to
ergonomic hazards (OSHA, 1991). According to the Bureau of Labor Statistics (1990), MCTD
account for 48% of work-related injuries in the private sector. A recent review of workers’
compensation records revealed that reports of MCTD have also increased for the U.S. Army
(M. Bonds, personal communication, 1992). The expense is considerable in lost work time,
medical treatment, rehabilitation, and diminished morale. The estimated workers’ compensa­
tion cost for the Army for one case of carpal tunnel syndrome (CTS) is approximately $10,000
(M. Bonds, personal communication, 1992).
Workplace factors are thought to be causative elements in 47% of all cases of CTS (Baker
& Ehrenberg, 1990). Occupations considered at risk for development of upper extremity
MCTD (including CTS) include office workers, cashiers, assembly-line industry workers, meat
cutters, butchers, musicians, cooks, and dental hygienists (Fry, 1986; Huntley & Shannon, 1988;
Jensen, Klein, & Sanderson, 1983; Nathan, Meadows, & Doyle, 1988; Paulozzi, Helgerson, &
Apol, 1984).
Work-related musculoskeletal injuries or illnesses reported by dental hygienists involve
areas of the back, neck, shoulder, elbow, wrist, and hand, as well as varicose veins and eye strain
(Boyer, Elton, & Preston, 1986; Macdonald, 1987; Shannon, 1984). Among dental workers,
work-related pain has been reported to be high for the back (44%), neck (62%), and shoulders
(80%), and for the three combined (72%; Gravois & Stringer, 1980; Oberg & Oberg, 1993;
Rundcrantz, Johnsson, & Moritz, 1990). A study of Minnesota dental hygienists revealed that
7% had been diagnosed as having CTS, whereas 63% reported experiencing one or more
symptoms associated with CTS (Osborn, Newell, Rudney, & Stoltenberg, 1990). Similar results
were found among California dental hygienists, among whom 6.4% of those surveyed had been
diagnosed with CTS (Macdonald, Robertson, & Erickson, 1988).
Although prior studies have examined the relationship between work conditions and
MCTD, none have explored the relationship of occupational classification with symptoms. This
study was conducted at the request of the Ft. Leonard Wood Dental Clinic staff for the
purposes of (a) identifying the prevalence of MCTD, associated symptoms and risk factors,
with special attention to CTS; (b) identifying dental practitioners at risk; and (c) developing
specific suggestions for decreasing risks for development of MCTD. Results pertaining to the
third goal are reported elsewhere (Rice, Pentikis, Rush, Murnyak, & Nindl, 1992). The study
included only personnel assigned to the Ft. Leonard Wood Dental Clinic.
2. MATERIALS A ND METHODS
Videotapes, two questionnaires, a medical record review (to confirm reported diagnoses), and
interviews were used in data gathering. All available dental workers (92% of employees) at
the Ft. Leonard Wood Dental Clinic in Missouri participated in the pilot study. All question­
naires were reviewed during interviews to help in distinguishing symptoms commensurate with
MCTD versus transient symptoms.
Forty-five dental workers completed two questionnaires. The first questionnaire was specifi­
cally developed for this survey. The second questionnaire was developed at Health Services
Command and was field tested during the survey at Fort Leonard Wood, MO. Participants
completed their questionnaires without discussing their responses with other dental care
workers. A member of the research team was present to respond to questions. The question­
naires addressed demographic information including height, weight, age, marital status, gender,
and ethnicity. Data was also obtained on the number of hours spent in leisure and self-care
pursuits involving prolonged upper extremity use and handedness. Work and occupational
histories included identification of occupational specialty; years worked in specialty; patients
treated per day; hours of work per week; percentage of time spent in patient care, laboratory
work, administration, and other duties; job satisfaction; and control over daily work routine.
Information was also gathered regarding previous job(s), exposure to vibration, time in specific
work tasks, sick leave, workers’ perception of whether their sick leave was related to their work
220
RICE, NINDL, AND PENTIKIS
duties, and limited duty assignments. Finger, hand, and wrist symptoms associated with CTS
(hand symptoms) were recorded: numbness or tingling, pain at night, sensation of “falling
asleep” during normal activity, stiffness, loss of strength, decreased sensation (loss of feeling),
frequent dropping of objects, and morning swelling. Participants identified specific work tasks
that caused pain: taking impressions, lip and cheek retraction, placing fillings, polishing teeth,
preparing filling mixture, and scaling. Participants were asked to list other procedures that
resulted in feelings of pain. Historical medical information included past hand or wrist injuries;
arthritis or joint problems; back pain or strain; prior hand, wrist, or arm surgery; a history of
repetitive trauma injury; diagnosed CTS; and participants’ perception of their general health.
Interviews were conducted to clarify responses and elicit additional information regarding the
dental environment.
In analyzing the questionnaire data, the five occupational specialties were combined into
three distinct categories: dentists, dental assistants and special assistants (DA/SA), and dental
hygienists and dental assistant-expanded function (DH/DAEF). Dental assistants-expanded
function receive special training that enables them to do work similar to that of a dental
hygienist and to perform a wide range of dental procedures under the direction of a dentist
including restoring teeth prepared by the dentist with permanent and temporary fillings;
placing, condensing, carving, finishing, and polishing amalgam restorations; supporting the
dentist in endodontic treatments by applying rubber dams, removing temporary fillings using
low-speed handpieces, and cleaning and drying the operative field. A detailed description of
the responsibilities of military dental hygienists and DAEF are described elsewhere (Rice et
al., 1992).
Three dentists, three dental hygienists, and six dental assistants-expanded function were
videotaped while treating a patient. The selection of procedures to be videotaped was based
on interviews with dental workers. Procedures that were common for each specialty were
included and individuals were randomly selected from scheduled appointments. All partici­
pants were right-hand dominant. To permit range-of-motion measurements, six locations on
the workers’ hands were marked with reflective tape prior to filming: (a) ulnar aspect of the
fifth digit metacarpophalangeal joint, (b) ulnar styloid process, (c) dorsum of the third digit
metacarpophalangeal joint, (d) natural depression in the capitate bone at the dorsal base of
the third metacarpal, (e) radial aspect of the second digit metacarpophalangeal joint, and (f)
the radial aspect of the radial styloid process.
Categorical data were analyzed using the chi-square statistic and risk ratios with Epi Into
statistical software (Dean, Dean, Burton, & Dicker, 1990). The Fisher exact test was used for
categorical data with a small cell n. Correlation coefficients (Pearson) were calculated for
continuous variables using the statistical Biomedical Data Processing Package (BMDP) analy­
sis of two-way frequency tables. Independent variables are listed in the description of the
questionnaire data. Dependent variables include the frequency of occurrence of CTS, number
of hand symptoms, specific incidence of upper extremity symptoms, back and shoulder symp­
toms, and reported sick leave used in the last year. Only significant findings are reported. It is,
therefore, important to be aware that none of the other data from the questionnaires were
found to be related to the frequency of occurrence of CTS, number of hand or wrist symptoms,
specific incidence of upper extremity symptoms, back and shoulder symptoms, or sick leave.
For example, there were no differences in the frequencies of men and women, ages of person­
nel, or number of years of dental work experience in the reporting of symptoms of CTS or the
other variables.
3. RESULTS
Of the 45 dental workers that responded to the questionnaire, 35 were married and 10 were
single; 30 were female and 15 were male. The age groupings were <34 (n = 12), 35 to 44 (n =
18), 45 to 54 (n = 10), and >55 (n = 5). Height groupings were <165.1 cm (n = 23), 167.6 to
DENTAL WORKERS: WHO IS AT RISK?
221
182.9 cm (n — 19), and over 182.9 (n = 3). Weight distribution was categorized as <56.3 kg (n
= 9), 56.8 to 67.7 kg {n = 9), 68.1 to 90.3 kg (n = 121), and >90.8 kg (n = 4).
Table 1 contains the videotape results. Because of the small number of participants, the
information was not statistically analyzed. The descriptive data are included to provide a
comparison among occupational groups. The table is divided into three sections. The top
section shows the percentage of patient treatment time spent with the hand held in power grip,
pinch grip, and holding the patient’s mouth open with a hand or finger. The category “other”
refers to any other position that the dental worker used during patient treatment. More than
50% of operative time for all three groups was spent using right and left pinch grips. Dental
hygienists and DAEFs spent more time holding the patient’s mouth open with their left hand
than did dentists. The second section shows the percentage of time spent with the wrist held in
an extreme posture. All three groups used their wrists in static positions of ulnar deviation,
flexion, and extension. All groups spent less time with their wrists in radial deviation. The last
row in Table 1 shows the high work to rest ratios for dentists, dental hygienists, and DAEF
identified from the videotape analysis. Dental hygienists had the highest ratios.
Back and shoulder pain was reported by 53% of the respondents. Women (65.5%, n = 29)
were 1.97 times as likely to report back pain as were men (33%, n = 15, p = .04). Persons
weighing <68.1 kg (76.4%, n = 17) reported back pain more frequently (1.91:1.00) than those
weighing more than 68.1 kg (40%, n = 25,p = .02).
Of the dental workers surveyed, 75.6% reported one or more symptoms associated with
CTS. Although there were only five diagnosed cases of CTS (11%), all reported experiencing
five or more (5+) hand symptoms (p < .01). Also, persons with diagnosed CTS were 3.3 times
as likely to report having 5+ symptoms compared with persons without diagnosed CTS
TABLE 1. Videotape Results: Percentage of Time in Static Hand or
Wrist Postures and Work/Rest Cycles
Dentist (n = 3)
DH (n = 3)
DAEF (n = 6)
Hand Position
left
right
left
right
left
right
power
0.0
5.6
1.2
7.0
3.2
12.3
pinch
59.2
69.5
53.0
79.1
50.2
66.5
hold
14.8
9.7
32 5
0.0
29 2
<1.0
other
26.9
16.0
13.3
13.9
17.6
21.8
ulnar
1.7
33.4
32.6
26.8
17.1
8.8
radial
<1.0
2.0
<1.0
0.0
0.0
0.0
neutral
<1.0
5.0
<1.0
2.4
2.9
7.5
flexion
55.1
39.4
30.5
32.4
37.8
50.1
extension
15.4
2.0
21.8
17.2
19.5
1 24
other
282
23.1
14.5
21.3
22.7
238
Work/rest ratio
2.8/1
5.3/1
6.5/1
6.2/1
4.4/1
2.6/1
Wrist Position
Note. DH—dental hygienist, DAEF— dental assistant-expanded function.
222
RICE, NINDL, AND PENTIKIS
(p = .006). Two other cases of CTS were reported, but were unconfirmed by physician diagno­
sis in their medical records.
Table 2 includes the hand symptoms that were found to be associated with diagnosed CTS
(p < .05). Of the 24 dental workers who reported experiencing hand or finger tingling, 25%
also had CTS, whereas none of the dental workers who did not report tingling had CTS (p =
.01). Approximately 29% of the dental workers who reported experiencing the symptom
“frequent dropping of objects” also had CTS, compared with 3% of those who did not
experience the frequent dropping of objects (p = .03). The confidence interval was large,
indicating that caution should be used in interpreting results. Individuals who reported expe­
riencing frequent dropping of objects were eight times more likely to have CTS than those who
did not report frequently dropping objects. Twenty-nine percent of those who reported expe­
riencing the sensation of their fingers or hand falling asleep, 35% of those experiencing
decreased sensation, and 23% of those experiencing a loss of strength also had CTS.
As a result of the relationship identified between diagnosed CTS and the number of hand
symptoms (Table 2), all persons experiencing five or more symptoms (17) were grouped
together and statistical analyses were conducted to identify associations between responses to
pertinent questionnaire items for persons with five or more symptoms, versus persons with
three or fewer symptoms. No person reported experiencing four symptoms.
For example, Table 3 shows the association between the number of patients treated per day
for persons with five or more symptoms compared with persons experiencing three or fewer
symptoms. Dental workers who typically treat between seven and nine patients per day
(56.3%) reported experiencing five or more symptoms more often than workers who treated
either fewer or more patients (p < .05). Table 4 shows the level of perceived job control
(moderate to total control, no to little control) X number of symptoms (5 + , ^ 3 ), and the level
of job control X the belief that sick leave taken in the last year was related to their work (yes,
no). Of the 25 individuals who perceived they had little or no control over their daily work
routine, 76% experienced five or more symptoms. Individuals who reported that they had little
or no control over their daily work routine were twice as likely to experience five or more hand
symptoms, compared with those who reported they had moderate to total control (38.9% ,p =
TABLE 2. Chi-Square and Risk Ratios (Rff) for Respondents Experiencing Carpal
Tunnel Syndrome and Finger or Hand Symptoms3
Condition
Experiencing
%
RR
Confidence Interval
p
Symptoms
Tingling
Frequent dropping
Falling asleep
Decreased sensation
Loss of strength
No (n = 20)
0.0
Yes (n = 24)
25.0
No (n= 14)
3.3
Yes (n = 30)
28.6
No (n = 17)
0.0
Yes (n = 27)
29.4
No (n = 14)
0.0
Yes (n = 30)
35.7
NO (n = 21)
0.0
YES (n = 23)
23.8
aOne participant had incom plete data, n = 44.
01
8.57
1.05 < R R < 69.82
03
.03
.02
02
DENTAL WORKERS: WHO IS AT RISK?
223
TABLE 3. Chi-Square Results
for Number of Patients Seen
per Day by Number of Symp­
toms
Patients/Day
n
%
6 or less
5
00
10-15
13
30,8
16 or more
11
36.4
25
7-9
16
56.3
.04
P
28
.01). Workers who reported they had little to no control over their schedules were twice as
likely to believe that their sick leave was related to their work (52.9%), compared with those
who felt they had more control (26.3% ,p = .03).
Workers who said they were less satisfied with their job did not report more symptoms.
Although marginally significant, respondents who found their work satisfying or very satisfy­
ing (n = 39) reported more symptoms (43.6%) than those who found their work unsatisfying
or very unsatisfying (n = 6, p = .06).
Of those who took sick leave in the preceding year (71% of respondents), 46.9% believed
the leave was related to their work duties (p = .002). Table 5 shows the relationship between
the belief that sick leave was related to their work (yes, no) and number of hand symptoms
(< 3 ,5 + ). It also shows the relationship between the belief that sick leave was related to their
work and CTS. Of the 30 workers who did not believe their previous year’s sick leave was
related to their work, 23% experienced five or more symptoms compared with 71 % of workers
who did believe their sick leave was related to their work. Individuals who believed their
previous year’s sick leave was related to their work were 3.06 times more likely to report
experiencing five or more symptoms (p = .002) and 8.34 times more likely to have diagnosed
CTS (p = .03).
Table 6 shows the relationship between persons who reported a history of a prior MCTD
(of any kind) with number of hand symptoms, specific hand symptoms, and CTS. Persons with
TABLE 4. Chi-Square and Risk Ratios (fffl) for Reports of Job Control by Number of
Symptoms3 and Job Control by Belief That Preceding Year's Sick Leave Was Related
to Work6
Condition
Job control
%
RR
Confidence
P
Interval
Numbers of
Moderate/Total Control (n = 18)
38.9
symptoms
No/Little Control (n = 25)
76.0
Believe leave
Moderate/Total Control (n = 17)
26.3
was related to
No/Little Control (n = 24)
52.9
(5+,
2.0
1.17 < R R < 4.96
.01
2.0
1.03 < R R < 6.25
.03
3)
work
(yes, no)
aTwo participants had incom plete data, n = 43. bFour participants had incom plete data, n = 41.
224
RICE, NINDL, AND PENTIKIS
TABLE 5. Chi-Square and Risk Ratios (/?/?) for Respondents' Belief That Sick Leave Was
Related to Work by Number of Symptoms and Belief That Sick Leave Was Related to Work
by Carpal Tunnel Syndrome (CTS)
Condition
Numbers o f sym ptom s
(5+ , <3>
CTS
(yes, no)
%
Sick leave related to work
No (n =
Yes (n =
No (n =
Yes (n =
23.3
71.4
3.2
26.7
30)a
14)
31)
14)
RR
Confidence Interval
P
3.06
1.48 < R R < 6.34
.002
8.34
1.01 < RR < 67.77
.030
aOne participant had incom plete data, n = 44.
a history of MCTD were more likely to report current experiences of five or more hand
symptoms; hand symptoms of tingling, pain at night, the sensation of “falling asleep” during
normal activities, loss of strength, decreased sensation, frequent dropping of objects, and
swelling; and CTS (p < .05). Only stiffness was not associated with a history of MCTD. Those
with a history of MCTD were also 12 times more likely to report experiencing CTS than those
with no history of MCTD, although the confidence interval was quite large.
Table 7 shows the relationship between occupational classification and CTS, back pain,
hand or wrist surgery, a history of MCTD, arthritis, a prior hand or wrist injury, and a number
of hand symptoms. All three occupational groups reported high incidences of back pain,
arthritis, and five or more hand symptoms. When compared with dentists, the DH/DAEF group
was 7.5 times more likely to report a history of MCTD, and 4.9 times more likely to report
experiencing five or more symptoms associated with CTS.
TABLE 6. Chi-Square and Risk Ratios (RR) for Respondents Reporting a History of Muscu­
loskeletal Cumulative Trauma Disorders (MCTD) by Symptoms
Symptoms8
Num ber o f sym ptom s
(5, S3)
Tingling
Pain at night
Sensation o f falling asleep
Loss of strength
Decreased sensation
Frequent dropping
Swelling
Stiffness
CTS
History of MCTDb
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
%
24.2
81.9
33.3
72.7
33.3
72.7
27.3
72.7
39.4
72.7
18.2
72.7
18.2
72.7
21.2
81.8
60.6
72.7
3.0
36.4
RR
Confidence Interval
P
3.4
1.74 < R R < 6.57
.0010
2.2
1.12 < R R < 3.75
.0400
2.2
1.19 < R R < 3.99
.0400
2.7
1.37 < R R < 5.18
.0100
1.9
1.06 < R R < 3.22
.0600
4.0
1.78 < R R < 8.98
.0020
4.0
1.78 < R R < 8.98
.0020
3.9
1.89 < R R < 7.88
.0006
1.2
0.76 < RR < 1.89
.7200
1.50 < RR < 96.28
.0100
12.0
aResponses to hand o r w rist sym ptom s and CTS were categorized as yes and no fo r current sym ptom s.
bResponses to p rior history o f MCTD were categorized as yes (n = 11) and no (n = 33). One participant
was m issing data, n = 44.
DENTAL WORKERS: WHO IS AT RISK?
225
TABLE 7. Chi-Square and Risk Ratios (RR) for Respondents' Occupational Classification by
Reported Condition or Symptoms
__________________________
Conditions3
CTS
Back pain
Hand or w ris t surgery
History o f MCT
A rth ritis
Prior hand or w rist injury
Num ber o f sym ptom s
(5, £3)
Occupation6
%
DA/SA
Dentist
DH/DAEF
Dentist
DH/DAEF
DA/SA
Dentist
DA/SA
DH/DAEF
D DA/SA
Dentist
DH/DAEF
Dentist
DA/SA
DH/DAEF
Dentist
DA/SA
DH/DAEF
Dentist
DH/DAEF
DA/SA
5.3
6.7
25.0
40.0
57.9
66.7
0.0
7.1
16.7
6.7
21.1
50.0
20.0
52.6
66.7
7.1
9.1
11.1
14.0
36.9
69.3
RR
Confidence Interval
Chi-Square
P
1.27
4.75
0.09 < R R < 18.527
0.70 < R R < 32.16
0.03
2.55
.700°
.150°
1.45
1.67
0.72 < R R < 2.91
0.81 < R R < 3 A 5
1.07
1.89
.300
.170
1.33
3.21
.440°
.150°
3.16
7.50
0.39 < RR < 25.38
1.04 < R R < 54.12
1.38
6.52
.250°
.016c
2.63
3.30
0.88 < RR < 7.89
1.12 < RR < 9.90
3.78
6.01
.052
.019C
1.27
1.56
0.09 < R R < 18.05
0.16 < RR < 15.01
0.03
0.15
0.690c
0.590c
2.58
4.85
0.63 < R R < 10.53
1.28 < R R < 18.38
2.07
8.43
0.140c
0.003c
Note. MCTD— musculoskeletal cum ulative traum a disorders, DA/SA—dental assistants and specialassistants, DH/DAEF— dental hygienists and dental assistant-expanded function.
R esponses were categorized as yes and no fo r current sym ptom s. bDentist: n = 14, DA/SA:
n = 18,DH/DAEF: n = 13. cFisher Exact.
Table 8 shows the relationship between occupational classification and specific hand and
wrist symptoms associated with CTS. The DH/DAEF group was more likely to report hand
symptoms of tingling, night pain, the sensation of their hand “falling asleep,” decreased
sensation, frequent dropping of objects, and swelling when compared with dentists (p < .05,
Figure 1). The DA/SA group reported experiencing hand and wrist symptoms of decreased
sensation, frequent dropping of objects, and swelling more often than dentists (p < .05). Only
the symptoms of hand and wrist stiffness and strength were not significantly different among
the three occupational groups (p = .15).
Figure 2 shows the percentage of time each occupational group reported spending in patient
care, administrative duties, lab work, and other duties. The category of patient care was further
broken down into specific tasks and the percentage of time spent in each task is in Figure 3.
The DH/DAEF group reported spending more time in scaling than did the DA/SA group, or
dentists (p < .05). Figure 4 shows that lip and cheek retraction was the task reported to most
often result in pain (p < .05).
4. DISCUSSION
A greater number of participants reported one or more hand symptoms, CTS, and back and
shoulder pain in this worksite analysis than in prior surveys of dental hygienists. However, the
number of dentists reporting back pain was similar to other studies (Table 9). Two important
differences between our study and other studies are that (a) our study was conducted at the
226
RICE, NINDL, AND PENTIKIS
TABLE 8. Chi-Square and Risk Ratios [RR) for Respondents' Occupational Classification by
Hand Symptoms
Symptoms3
Tingling
N ight pain
Asleep
S tiff
Decreased
sensation
Frequent
dropping
S welling
Strength loss
Occupation6
%
Dentist
DA/SA
DH/DAEF
Dentist
DA/SA
DH/DAEF
Dentist
DA/SA
DH/DAEF
Dentist
DA/SA
DH/DAEF
Dentist
DA/SA
DH/DAEF
Dentist
DH/DAEF
DA/SA
Dentist
DA/SA
DH/DAEF
DA/SA
Dentist
DH/DAEF
21.4
42.1
76.9
28.6
36.8
69.2
14.3
31.6
69.2
50.0
63.2
76.9
14.3
31.6
53.8
0.0
46.7
53.3
7.1
42.1
61.5
36.8
43.9
69.2
RR
Confidence Interval
2.0
3.6
0.67 < RR < 3.69
1.51 < RR < 8.56
1.55
8.32
.190°
.003
1.3
2.4
0.47 < R R < 3.51
1.07 < R R < 5.51
0.25
.46
.450c
.034
2.2
4.9
0.57 < RR < 8.59
1.67 < R R < 14.10
1.31
8.43
.230°
.004°
1.3
1.5
0.69 < RR < 2.32
0.86 < RR < 2.80
0.57
2.01
.450
.150°
2.2
3.8
0.57 < RR < 8.58
.14 < R R < 12.43
1.30
4.80
.023°
.037°
7.78
10.20
.005°
.002°
Chi-Square
P
5.9
8.6
1.24 < R R < 28.05
2.11< RR < 35.25
4.97
8.98
.030°
.004°
1.6
1.9
0.50 < RR < 2.72
0.95 < R R < 3.74
0.12
3.20
.170
.070
Note. DA/SA— dental assistants and special assistants, DH/DAEF—dental hygienists anddental assistantexpanded function.
R esponses were categorized as yes and no fo r current sym ptom s. bDentist: n = 14,DA/SA: n = 18,
DH/DAEF: n = 13. °Fisher Exact.
request of the dental clinic, indicating an already present concern, and (b) the number of
respondents in our analysis was substantially smaller than that collected during mass mailings
in other studies. All studies used questionnaires. Although the data seem to indicate that the
presence of the research team resulted in higher reports of symptoms, our interactions with the
dental workers seemed to indicate otherwise. We reviewed the workers’ questionnaires during
the interviews and were able to help respondents distinguish symptoms commensurate with
MCTD versus transient symptoms, with fewer symptoms claimed as a result.
In the general population, CTS occurs more often in women than in men and seems to be
more prevalent between the ages of 40 and 60. Neither gender nor any of the other demo­
graphic data were found to be associated with hand symptoms or CTS. However, women did
report more back pain. In contrast, Macdonald et al. (1988) found correlations among age and
hand weakness, hand clumsiness, and CTS. Macdonald et al. (1988) studied dental hygienists
practicing in California. Although the age range tested was not reported, it is reasonable to
assume that the larger sample size (n = 2,464) and different population provided a more
diverse sample compared with this pilot study.
Similar to findings by Macdonald et al. (1988), no relationships were found among leisure
activities and finger or hand symptoms, CTS, or back or shoulder pain. In addition, no relation­
ship was found between subjective assessment of general health and MCTD symptoms.
Table 10 shows a comparison of symptoms found in this study with those of Macdonald et
al. (1988) and Huntley and Mays (1986). Again, our results revealed a higher percentage of
DENTAL WORKERS: WHO IS AT RISK?
227
DH/DAEF
■ DROP
<
□
DA/SA
t in g l in g
13 DECREASE
CL
Z3
■ pain
o
o
S3 ASLEEP
o
■
s w e l l in g
S STIFFNESS
DENTIST
E x!o ra x X x xxxx xxx xxxi
0
20
40
60
80
100
PERCENTAGE REPORTING SYMPTOMS
Figure 1. Frequency distribution of hand and wrist symptoms x occupation.
respondents reporting symptoms. Huntley and Mays (1986) evaluated responses from 46
Wichita State University dental hygiene alumni and therefore, their number of respondents
was comparable to ours. As mentioned, we evaluated a worksite that was already concerned
about MCTD and CTS, indicating that workers had reported symptoms to their supervisors,
thus potentially inflating our findings.
DH/DAEF
R PA TIENT C A R E
□ LAB W O R K
S3 A D M IN
■ O THER
O
!<
CL
3
O
O
DA/SA
o
DENTIST
0
20
40
60
80
100
PERCENTAGE OF TIME
Figure 2. Percentage of time reported working in four major work areas x occupation.
228
RICE, NINDL, AND PENTIKIS
DH/DAEF
Z
O
£
CL
D
DA/SA
m IMPRESS
xmxxxxxxa
□ RETRACTION
O
O
o
FILLING
9 POLISH
S
mix
DENTIST
0
20
40
60
80
100
120
PERCENTAGE REPORTING SYMPTOMS
Figure 3. Percentage of time reported working in patient care tasks x occupation.
Table 11 compares our findings with those of Osborn et al. (1990). Osborn et al. (1990)
received questionnaires from 443 dental hygienists practicing in Minnesota and found that
63% of respondents had experienced at least one symptom typically associated with CTS.
Respondents from that group were then referred to as the “symptomatic” group. Again, our
findings (using the DH/DAEF group) revealed higher numbers of “symptomatic” and diag­
nosed CTS respondents experiencing specific symptoms, perhaps because CTS had already
been recognized as a problem for the particular clinic that we evaluated. Our findings agreed
with Osborn et al. that tingling or numbness, clumsiness (dropping), and loss of strength were
associated with CTS (Table 2). However, we did not find that night pain was associated with
CTS, and we did find that sensations of the fingers or hand falling asleep and decreased
sensation were associated with CTS. Because night pain has been a gold standard and
Osborn et al. (1990) found that 96% of those diagnosed with CTS experienced night pain, it is
possible that the questionnaire was phrased differently in the two studies.
The DH/DAEF group members were more likely to have experienced CTS, one or more
hand symptoms, and back pain. They were also more likely to have a history of MCTD. This
may be partially due to the DH/DAEF group doing more polishing and scaling, and using their
left hand in a static position during retraction for longer durations than the other groups.
Unlike Macdonald et al. (1988), we did not find that specific hand symptoms, the number
of symptoms, or the presence of CTS were related to number of years in practice or the number
of hours practiced per week. We did find that the number of patients treated per day was
related to the number of symptoms (i.e., dental workers who treated seven to nine patients per
day reported more symptoms). This result may be indicative of the amount of effort that was
required per patient, however, this variable was not considered in this study. Macdonald et al.
(1988) found the number of patients per day that had heavy calculus on their teeth was
DENTAL WORKERS: WHO IS AT RISK?
RETRACTION
MIXING
co
SCALING
co
^
FILLING
POLISHING
OTHER
0
5
10
15
20
FREQUENCY
Figure 4. Frequency distribution of tasks reported to cause hand or wrist pain.
TABLE 9. Comparison of Carpal Tunnel Syndrome (CTS) Diagnosis, CTS
Symptoms, and Back Pain Among Studies (%)
S tudy
One or M ore
S ym ptom s
CTS
Osborn et al., 1990
M acdonald et al., 1988
Huntley and Mays, 1986a
Boyer et al., 1986b
Fauchard Academy, 1965c
Rundcrantz et al., 1990d
7.00
6.40
| | JJJf-i |
Christensen et al., 1994d
i j g i i j i i i i i i i .§§§§
This study
Dentists
DA/SA
DH/DAEF
63.0
■
||j
0.07
m
i
54.0
1.6
'
11.00
7.10
5.30
25.00
Back Pain
-
75.6
71.4
73.7
84.6
• liM S lK i
8.3
33.3
upper
18
low er = 43
59.0
53.3
42.9
57.9
66.7
Note. Shaded areas not tested. DA/SA— dental assistants and special assistants,
DH/DAEF— dentalhygienists and dental assistant-expanded function.
aAII reported by Huntley et al. (1988). bAII respondents had 2-year w o rk experience,
56% were 22 to24 years old w ith a mean age of 26. cAs reported by Boyer et al.
(1986). P a rticip a n ts were dentists;other studies used dental hygienists.
229
230
RICE, NINDL, AND PENTIKIS
TABLE 10. Comparison of Hand Symptoms Reported Among Studies (%)
Symptoms
Huntley and Mays, 1986
Macdonald et al., 1988
Paresthesia
17
33.2
Weakness
Night Pain
34
Clumsiness
This study
32 0
46 7
28 0
42.2
192
31.1
Numbness
21
44.4
Tingling
17
44.4
Note. Shaded areas not tested.
associated with the presence of symptoms. Patients with heavy calculus require more physical
effort than those with light calculus.
The task reported most frequently to cause pain was retraction. This static task is required
of each of the occupational categories. In the videotape analysis, “holding” (i.e., holding the
patients mouth open with their hand) was found most often in the work of the DH/DAEF
group. Using the right hand in a flexed posture also occurred more often for DH/DAEF group
TABLE 11. Comparison of Symptoms in Participants With Diagnosed Versus Undiag­
nosed CTS Among Studies (%)
F in g e r o r H and
O sbo rn et al., 1990
T h is s tu d y
D iagn ose d
S ym p to m a tic
D iagnosed
S y m p to m a tic
Loss of strength
31.5
80
63
100
Shooting sensation
30.9
80
Tingling or num bness
29.3
96
40
100
Cold
26.7
44
Clum siness (dropping)
23.1
68
43
80
Night pain
21.4
96
57
80
Num bness on
20.7
84
49
100
Stiffness
83
100
Decreased sensation
43
100
Morning swelling
49
60
S y m p to m s
or pain while working
aw akening
Sensation of "falling
asleep" during normal
activity
Note. Shaded areas not tested.
DENTAL WORKERS: WHO IS AT RISK?
231
than for dentists. Smith, Sonstegard, and Anderson (1977) indicated that maximal pressure on
the median nerve is related to the load on the flexor digitorum profundus tendons of the
second and third digits (as occurs in pinch) and that greater pressure occurs when the wrist is
flexed. The DH/DAEF group also reported spending more time scaling and polishing than did
other groups. Scaling, root planing, and ultrasonic instrument scaling have been found to
initiate or aggravate upper extremity “altered sensations” (Stentz et al., 1994).
The greatest risk factors may be the tasks that dominate the dental practitioner’s daily
routine, such as using the hand in a flexed position, the practitioner’s method of practice,
and the effort required (heavy calculus). Although we did not examine the dynamic motions
(velocity and acceleration) and force used, both have been indicated in previous research
to be associated with high-risk jobs for MCTD and CTS (Marras & Shoenmarklin, 1991).
Cuthbertson, Shannon, Mays, Huntley, and Gien (1989) found dental hygienists with CTS
symptoms used a mean scaling pressure that was 66% higher than those without symptoms.
The same relationship did not hold true for total pressure differences between those with
and without CTS symptoms. Unfortunately, these results cannot be used to indicate that
force was necessarily a causal factor in symptom development, as increased force may have
been used to compensate for symptoms of paresthesia. The findings may also indicate that
specific tasks (e.g., scaling) are more closely associated with the risk for development of
MCTD and CTS symptoms, which has been surmised by other authors (Bauer, 1985; Edgington, 1983).
Medical conditions that are associated with CTS include diabetes mellitus, hyperthyroidism,
pregnancy, arthritis, myxedema, and injuries to the wrist. Osborn et al. (1990) found that
arthritis and traumatic injury to the wrist appeared to put respondents at greater risk for
development of symptoms. Although the incidence of arthritis was greater among DH/DAEF
and DA/SA occupational groups, the present study did not find arthritis to be associated with
the number of hand symptoms, prevalence of CTS, or back pain. Traumatic injury was also not
associated with hand symptoms.
Feelings of control over one’s daily work routine were associated with the number of hand
symptoms and with the belief that sick leave taken was related to work requirements. Dentists
had input into their own schedules and their assistants’ (DA/SA) schedules. DH/DAEFs’
schedules were determined by administrative staff, who may not comprehend the implications
of scheduling. It is important to note that these are not individuals who are merely dissatisfied
with their work. Instead, they appear to enjoy their profession and the general work environ­
ment, but are having hand symptoms. They also verbalized concern about their health, their
ability to do their job, and their future. Although we did not evaluate this, they may be
conscientious individuals who continue to do their best despite warning signals, such as pain,
that tell them they need to alter their work style.
The presence of upper extremity symptoms in the workforce is likely to be affecting
productivity, as those with five or more symptoms were nearly twice as likely to take sick leave
as those experiencing fewer symptoms and 46.9% of those who took sick leave in the last year
believed the leave was related to their work duties. We did not compare the number of
workdays lost for individuals with and without CTS. However, among aircraft workers, those
with CTS are reported to miss 54.3 workdays compared with 9.8 workdays lost by those
without CTS (Cannon, Bemacki, & Walter, 1981). Associated costs of worker injuries include
frustration and the lack of faith in the administration that can result, as well as the lost duty
time.
Prevention, followed by early identification and treatment, are the preferred methods of
managing MCTD. Applying sound ergonomic design principles in the workplace can best
guide an injury prevention program by emphasizing workplace redesign, use of ergonomically
designed instruments and furniture, training and education, environmental changes, adminis­
trative solutions, and establishment of a medical surveillance program. For example, because
tasks requiring static postures were associated with pain, modifying the work environment
with increased use of suction equipment, specially designed armrests on operator chairs, and
arm supports on patient chairs can reduce fixed working positions of the back, neck, and
232
RICE, IMINDL, AND PENTIKIS
shoulder (Oberg, 1993). An administrative solution would include giving dental workers some
control over their work schedules.
5. CONCLUSION
Because of the small number of participants, the data from this pilot study should be inter­
preted with caution. Rather than generalizing the results, they should be used to suggest trends
and ideas for future research considerations.
All three groups (dentists, DA/SA, and DH/DAEF) reported back and upper extremity
symptoms. However, the DH/DAEF group was found to be at greatest risk for development
of upper extremity symptoms, CTS, and back pain. Possible contributors to the higher risk for
the DH/DAEF group are repetitive motions and using the right hand in flexion during
polishing and scaling, the static position of the left hand during retraction, and the inability to
control their work schedules.
The results indicate that dental workers who report hand symptoms are not simply unhappy
with their work situation. Instead, our results indicate that workers who like their work are
more likely to report hand symptoms. One possibility that needs to be examined is whether
some workers put an exceptional amount of effort into their work; that is, take fewer breaks,
work harder and longer, thus putting themselves at increased risk.
Symptoms found to be associated with CTS were tingling or numbness, clumsiness (drop­
ping), and loss of strength. Early identification of symptoms could allow for earlier interven­
tion and prevent the development of CTS. Further studies should include identification of
symptoms that develop the earliest; examination of the prevalence of symptoms such as fingers
or hands falling asleep, decreased sensation, and night pain; and determination of whether the
number and type of symptoms are related to patients’ prognosis.
Although factors known to be associated with the development of CTS have been identi­
fied, the etiology is still being investigated. From the results of this study, it is reinforced that
static, awkward positions of the wrist (flexion) and fingers (pinch), and repetitive wrist motions
are implicated. Specific tasks, such as retraction and scaling, may emphasize these motions,
resulting in localized fatigue and putting the practitioner at greater risk for injury. Prospective
studies investigating dynamic motion, force, and individual differences are necessary to more
accurately define work-related causes of MCTD and to consequently develop effective pre­
ventive programs.
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