Effect of Tool Design on Hand Pain in Dental Practitioners
Condition: Shoulder Pain
MeSH terms: Shoulder Pain
Study type: Interventional

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.
    

Detailed 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).
    

Intervention name(s): narrow diameter heavy dental tool; large diameter light weight tool
Intervention type(s): Other; Other
Intervention description(s): 8mm diameter, heavy periodontal tool made from steel; Periodontal tools (4-8) provided to dental practitioners to use for all dental scaling or cleaning. This tool handle diameter is 11 mm diameter and it is made from lightweight Delrin.
Other intervention name(s): traditional tool; intervention tool
Allocation: Randomized
Intervention model: Single Group Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Prevention
Keywords: ergonomics; workplace; occupational; tool; dental; dentist