A Randomized Controlled Trial Among Dental Practitioners: Effect of Scaler Handle Design

Introduction
Among dental practitioners, the high pinch force applied during dental hygiene work is a risk factor for musculoskeletal disorders of the upper extremities. In the laboratory, we previously demonstrated that handle design influences pinch force during dental scaling; larger diameter handles were associated with less pinch force. The purpose of this study was to evaluate the effect of periodontal curette handle diameter and weight on right upper extremity pain among dental practitioners.

Methods
This was a 4-month cluster randomized controlled trial with randomization at the dental office. Dentists and dental hygienists (N=110; 90 offices) who performed scaling, root planing or dental prophylaxis were recruited. Right wrist, elbow and shoulder pain levels were assessed weekly. One month after starting the study, participants received either a set of light (14 g), large diameter (11 mm) or heavy (34 g), narrow diameter (8 mm) periodontal curettes. Changes in mean pain scores across the study period were compared between treatment groups using general linear models controlling for covariates.

Results
The mean right pain scores at baseline were: wrist 2.0 (±1.4), elbow 1.7 (±1.3), and shoulder 2.1 (±1.4). Over the intervention period, the pain scores improved more in all three body regions among subjects assigned the light, large diameter tools. After adjusting for age, gender, occupation and hours of tool use per week the differences due to tool were only significant for the shoulder (0.52 v 0.19, p=0.02).

Discussion
This study demonstrates that periodontal tool design influences upper extremity pain among dental practitioners, but the effect size was modest. Limitations of the study included the relatively short duration of the intervention and the lack of physical examination finding to confirm the subjective outcomes. Using a lighter, larger diameter instrument may be an easy and cost-effective intervention to reduce or prevent upper extremity pain associated with dental hygiene work.