Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT01332760 |
| Other study ID # |
H5534-32614 |
| Secondary ID |
R01OH008892 |
| Status |
Completed |
| Phase |
N/A
|
| First received |
April 6, 2011 |
| Last updated |
February 21, 2012 |
| Start date |
April 2009 |
| Est. completion date |
March 2011 |
Study information
| Verified date |
February 2012 |
| Source |
University of California, San Francisco |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
United States: Institutional Review Board |
| Study type |
Interventional
|
Clinical Trial Summary
Dentists and dental hygienists experience elevated rates of musculoskeletal disorders, such
as carpal tunnel syndrome and tendonitis, primarily due to the high pinch force required for
dental scaling. There is evidence that a lighter and larger diameter tool can significantly
reduce the pinch force. This randomized controlled study will determine if dentists or
dental hygienists who use such a tool report less hand and arm pain compared to those who
continue to use the conventional tool design.
Description:
This is a randomized controlled trial to evaluate the effects of a new dental tool handle
design on hand and arm symptoms among dentists and dental hygienists who perform dental
scaling. This will be a 4 month intervention in the practitioner's workplace. The study may
identify a tool handle design that reduces the risk for developing upper extremity
occupational musculoskeletal disorders (e.g., carpal tunnel syndrome) among dentists and
dental hygienists.
The specific aims of the project are to determine whether hand/wrist, forearm/elbow and
shoulder symptoms (e.g., pain, fatigue, paresthesias) and hand function are less severe
among dentists and dental hygienists who use a new dental tool in comparison to those who
use a more conventional tool for performing scaling. One hundred twenty (120) subjects will
be randomized to use one of 2 handle designs for a 4 month period and during this time will
perform their usual dental scaling work with the new tools. The effects on outcome measures
will be adjusted for potential covariates (e.g., age, gender, hours scaling per week, etc.).
The primary null hypothesis is: there is no difference in change in pain severity between
subjects who use a new tool in comparison to those who use a conventional tool.
RESEARCH DESIGN AND METHODS
In this study, 120 participating dentists and dental hygienists will be randomized to
receive one of 2 scaling tools and will use the tools for 3 months while performing their
usual dental scaling work. Randomization will be at the level of the clinic to avoid
participant contamination. Participants will complete a weekly questionnaire to assess
symptom severity. The data analysis will use an intention-to-treat approach and will control
for important covariates.
Interventions Based on the pilot data, the investigators have selected 2 tool handle designs
that are similar to conventional tools but have features that exploit the differences
identified in our preliminary data. The dependent measures of pinch force and muscle
activity were most sensitive to diameter, followed by weight, followed by shape. The tool
characteristics selected for this proposal are based on the data from the laboratory studies
presented in the Preliminary Studies section and the Appendix (Dong et al., JADA, 2006; Dong
et al., Appl Ergo, 2007). The tool parameters were selected to provide the greatest
difference in peak pinch force, yet be as close as possible to the look and feel of a
conventional instrument. Half of the participants will be provided with Tool 1 and half with
Tool 2. Tool 1 is the closest to a conventional tool in diameter and weight while Tool 2 has
a larger diameter and is lighter. The differences and similarities between Tools 1 and 2 are
listed below.
Tool 1 Tool 2 Color black black Material steel Dacron Surface texture medium diamond medium
diamond Diameter 7.5 mm 10.8 mm Weight 20 g 12 g Shape round round
The investigators expect participants to apply less force with Tool 2 than Tool 1 and,
therefore, decrease their risk for hand pain and disorders.
Subjects
Dentists and dental hygienists (N=120) will be recruited from community and private clinics
in the Bay Area.
Recruitment
Dentists will be recruited at county dental society meetings and through mailings to their
clinic (mailing list provided by the CDA and The Zenith). Dental hygienists will be
recruited through mailings to their homes or places of work (mailing list provided by
regional dental hygiene association) or at informational meetings at their regional dental
hygiene meetings or at dental clinics.
At recruitment meetings, potential participants will be handed the consent form and the
study. The inclusion criteria will be explained by one of the co-investigators and questions
will be answered. Potential participants will complete a brief, anonymous survey to indicate
whether they are eligible and whether or not they are interested in participating. If they
are interested and eligible in participating, they will sign the consent form and be
enrolled in the study.
Mailings will include a description of the study, the consent form and a participation
postcard. The postcard will have 3 check boxes: (1) yes I am interested in participating,
please call me, (2) I have more questions about the study, please call me, or (3) I am not
interested in participating, please do not contact me again. Those who agree to participate
will be instructed to sign the consent form and return it.
Baseline Questionnaire
Participants will be mailed a 30 minute baseline questionnaire to collect the following
demographic information and covariates: recent or current symptoms of an MSD; occupational
history; current job information (e.g., hours per clinic per week, hours scaling per week,
glove type used); medical history including previous musculoskeletal injury or illness, pain
medication usage, systemic diseases related to MSDs; tobacco use; personal demographics; and
psychosocial factors. The investigators plan to use the standardized Job Content
Questionnaire to measure job control, psychological demands, job strain, social support, and
job satisfaction (Karasek et al., 1998; Rempel et al. 2006).
End-of-Week Questionnaire: Pre-intervention
They will also begin completing a weekly, 5 minute, end-of-week questionnaire (see appendix)
which assesses work hours for the week, number of hours scaling for the week, medication use
for pain, hand function, and acute injury events to the upper extremities (e.g., laceration,
bruise) during the week (If an elevated pain score is due to an acute traumatic event, the
symptom score for that week will be excluded from the analysis). Three body regions (1) the
right hand/wrist, (2) right elbow/forearm and (3) the right shoulder (or left if the subject
performs scaling with the left hand), will be assessed for the worst pain during the
preceding 7 days using a 0 to 10 point scale (0=no pain; 10=unbearable pain) (Gerr et al.
2002).
Randomization and intervention
The dental office that the participant works in will be randomized to either Tool 1 or Tool
2. A computer generated random number sequence will be used. All participants at the same
dental office will use the same tool to avoid contamination.
After completing the end-of-week questionnaire for four weeks the participant will receive
the new set of 8 assigned dental tools and will be instructed on their use, tip replacement,
tip sharpening and sterilization. If there is more than one participant at an office, the
tools for each participant will be separately labeled with color tape to identify the owner.
End-of-Week Questionnaire: Post-intervention
The same end-of-week questionnaire will be administered for the next 3 months. However, the
questionnaire will contain an additional question which asks what percent of time they used
the new tools when scaling. This question will allow us to determine if the assigned tools
are being used.
Data Analysis and Sample Size Calculations
The analysis will follow an intention-to-treat approach. For the analysis of the effect of
intervention on pain in the three body regions, the primary outcome measure will be the pain
score change (difference between the mean post-intervention pain level, collected during the
last 4 weeks of their participation in the study, minus the mean pre-intervention pain
level). Because the analysis uses an intention to treat approach, if the subject drops out
of the study early, the investigators will use the pain data from the 4 weeks prior to the
drop out point to estimate the mean post-intervention pain score. Therefore, the
investigators collect weekly symptoms data throughout the intervention period. The subjects
studied are in relatively stable occupational settings, so the investigators do not
anticipate that many subjects will leave early. Ultimately, if there is a change in pain
scores after the intervention, all of the weekly data will be used graphically to explore
the time course of change. Missing weekly pain scores will be imputed by the mean of the
scores just prior to and following the missing data.
General linear models will be used to calculate the beta-coefficient and 95 percent
confidence intervals for the intervention for each of the two body regions. The mean
pre-intervention pain score will be forced into all models to reduce regression to the mean.
The other possible covariates (e.g., gender, age, occupation, hours per week of scaling,
psychosocial factors, etc.) will each be examined, one at a time, in multivariate models
which include the pre-intervention pain score. They will be included in the final models
only if they are modestly (p<0.2) related to both the dependent variable (e.g., pain score
change) and intervention group. The investigators expect effective randomization so it is
likely that few potential covariates will be included in the final model. The potential
problem with the unequal gender distribution between occupational groups will be addressed
by also testing the effect of a new single variable with 4 categories (male dentists, female
dentists, male hygienists, female hygienists) on the model. The analysis of the hand
function data will be similar to the analysis of pain.
The sample size calculations are based on the estimated mean hand pain score of 2.9 (SD 1.6;
scale of 0-10) (based on values collected from subjects in the preliminary studies). For
type I error of 5%, the investigators would need a total of 82 subjects (41 each group) to
have 80% power to detect a mean pain score change difference of 1.0 (33% difference in pain
score change). Covariates in the final model will increase the required sample size. To
account for covariates and dropouts the investigators will recruit a total of 120 subjects.
The selection of a difference of 1.0 for pain score change is based on the affects from the
expected difference of 27 to 40% in pinch force. Unfortunately, the investigators do not
have good dose-response data linking reduction in a risk factor level, such as pinch force,
to a reduction in pain levels. If the dose-response relationship is linear, the
investigators might expect a similar reduction in pain intensity. In 3 prior RCT
intervention studies, although the interventions were different than in this proposal, the
investigators observed such effect levels. The studies were among engineers, customer
service, garment workers with study durations of 6, 12 and 4 months. The observed effects on
upper extremity pain scores were 41% (1.2/2.9), 28% (0.7/2.3), 42% (1.0/2.4) (Tittranonda et
al., 1999; Rempel et al., 2006; Rempel et al., 2007).
