The effect of loupes on neck pain and disability among dental hygienists

1.1 Musculoskeletal disorders in the dental hygiene profession

Musculoskeletal disorders (MSD) represent a significant and costly occupational health issue for the dental profession [1–4]. Work related MSD include injury, trauma and pain to both the soft and hard tissues of the body, and frequently develop over time [3]. As a preventive dental practitioner, the physical burden of performing repetitive and precise tasks such as scaling and debriding teeth places dental hygienists at a high risk of work related MSD [3, 5]. Recent research supports this observation, with the prevalence of MSD in the profession reported at rates between 64% and 93% [3]. Hygienists are more likely to suffer neck, shoulder and wrist pain than other dental professionals [6–8]. Hygienists are also exposed to a number of other identifiable risk factors, such as a large number of occupation related computer usage hours, psychosocial stress and being predominately of female gender [3, 9–13]. This occupational health issue leads to lost work time, diminished work performance, medical attention and possible early retirement [14, 15]. The economic ramifications of this situation are substantial, with lost earnings in the United States of America due to MSD in the dental profession reported at over $40 million some years ago [5]. With a considerable proportion of the profession reporting MSD, and the consequent effects and impacts of this, research into the prevention of this problem is imperative.

Neck pain specifically has been identified as a common complaint of dental hygienists, with the 12 month prevalence reported at between 54% and 69% [6, 17]. Work-related tasks such as scaling teeth appear to predict reported neck pain among Australian and Swedish dental hygienists, as does the stress of balancing work with family commitments [18, 19]. Dental hygienists suffering from neck pain are more likely to have time off work or are considering reducing their working hours [18], affecting productivity and career longevity.

It is evident that the problem is widely acknowledged, however much of the information regarding prevention of MSD among dental hygienists appears to be anecdotal [3]. Developing an ergonomic solution has been limited by attention bias when examining postural improvements [20, 21], and participants completing undemanding simulated tasks during the intervention [20, 23]. As a result, there has been little development or progression in ergonomics for the dental hygiene profession.

1.2 Loupes as a preventive measure against MSD

New technologies, such as loupes [surgical magnification] for the dental hygienist are being promoted as a preventive measure for MSD in the profession. Loupes are an eyewear system of telescopes attached to lenses (Fig. 1), which magnify the viewing field; in the case of dental clinicians, this means the teeth and the gingiva [24]. However, there appears to be no longitudinal studies or research using objective measures to support this innovation. The use of surgical magnification when providing dental treatment allows the clinician to maintain their natural posture, which in turn is believed to reduce the risk of musculoskeletal pain or discomfort [25]. It has been suggested that loupes may reduce the physical stresses on the body [26]. While the use of loupes amongst hygienists is not commonplace, it is nevertheless, a tool that hygienists may choose to use in their daily practice. At the current time loupes are not considered to be essential for workplace safety and sound ergonomics.

Current research into the effect of loupes appears to have been limited to self-reported measures of MSD through the use of questionnaires [18, 28], or a single case study reporting a student’s experiences [24]. To our knowledge, there is no contemporary research in the literature that has utilised triangulation methods to assess the effectiveness of using loupes on MSD in practising dental hygienists. The use of both self-reporting and objective outcome measures would provide a clearer insight into the potential benefits and limitations to wearing loupes during clinical patient care. The aim of the present study is to investigate the effect of the use of loupes on neck pain and disability in dental hygienists, using triangulation methods.

2.1 The intervention: Loupes

Subjects in the treatment group were issued with flip-up Galilean loupes in 2.5x magnification. This level of magnification offers the widest field of view and longest depth of focus when compared to higher powers. The flip up function allows the magnification lenses to be adjusted during treatment or flipped out of sight when talking with patients or writing notes. Participants in the treatment group were individually fitted for loupes, measuring the working distance for appropriate fit. Working distance is the distance between the eyes and the oral cavity, and is often crudely proportionate to height. These measurements are crucial for the hygienist to have a clear view of the oral cavity and work in a balanced working position. It has been suggested that poorly fitting loupes can actually exacerbate MSD, given that they may require the clinician to place themselves in an awkward position for optimal vision [25]. The intervention involved subjects wearing the loupes during all clinical care provided to their patients in practice for a period of six months.

2.2 Outcome measures

Both self-reported and objective measures of musculoskeletal pain in the neck region were collected. Self-reported measures of neck pain and dysfunction were evaluated by the Neck Pain and Disability Scale (NPDS). The objective measures of upper body musculoskeletal symptoms were evaluated by a physical assessment, following a standardised protocol. The physical assessment included measures of cervical range of movement (CROM), low load craniocervical flexion, cervical proprioception, and craniovertebral angle. Each of these measures are published in protocols elsewhere, and have been established as reliable and reproducible [29–34]. The characteristics of these measures are described in Table 1.

2.3 Recruitment

All full members of the New South Wales branch of the Dental Hygienists Association of Australia were contacted via post, and final year dental hygiene students at the University of Newcastle were also approached at the beginning of a clinical session on campus by a person not involved with the project. All those invited received a participant information statement, consent form and self-addressed reply-paid envelope. Interested participants who met the inclusion criteria and did not meet any of the exclusion criteria (Table 2), and who voluntarily returned the signed consent form were considered eligible for the study. The minimum sample size required to determine a statistical difference in outcomes was 12 participants in each group, based on the minimal important change of 12 points difference in NPDS scores, a type I error of α= 0.05 and 80% power.

2.4 Procedure

All participants were required to travel to The University of Newcastle (Ourimbah campus) to complete baseline demographic data collection, the NPDS survey and undergo the physical assessment. At this stage, participants in the treatment group were also personally fitted for loupes. Participants allocated to the treatment group were required to wear loupes during clinical treatment of patients, for the next six months. Participants allocated to the control group were required to work as usual, that is without the use of surgical magnification, for the next six months. Participants in the control group were also required to agree not to use loupes during the study period. At the end of the six month period, participants would again be required to complete the NPDS outcome measure as well as attend The University of Newcastle for a post-test physical assessment.

2.5 Analysis

An intention-to-treat analysis was adhered to throughout the study. Tabular summaries of demographic characteristics summarised responses using descriptive statistics, while comparison of the survey data pre- and post-test were performed using mixed ANOVAs. The primary outcome factor was change in neck pain and/or disability.

4.1 Strengths of the study

This research is unique, in that it utilised triangulation methods in a longitudinal study to measure loupes as a preventive measure or intervention for MSD. The use of physical measures to assess dental hygienists has been underutilised and in the few studies which attempt this, explicit standardised protocols have not been reported. In a five-year follow up of female dental personnel, it is claimed that a standardised protocol was adhered to for the physical assessment [6]. However, it seems only broad criteria for pain and palpable tenderness was stated rather than explicit and reproducible techniques. Similarly, a physical examination protocol examining the prevalence of carpal tunnel syndrome and upper extremity tendonitis among American hygienists did not report specific methodologies [41]. Furthermore, repeated physical measures have not been used previously when investigating MSD among dental hygienists. Previous studies have used physical examinations as a measure of real time muscle activities (electromyography) [22, 42] and positions (goniometry) [42, 43] or sensory perception ability (vibrometry) [44]. However, these studies fail to record changes in musculoskeletal symptoms over time.

4.2 Limitations

In Australia, while the dental hygiene profession is rapidly growing, it nevertheless remains a small and relatively young cohort when considered from an international perspective. As such, the recruitment of participants for this study was challenging, given the small numbers in the profession and the geographic distances required to travel for the physical assessments. At the current time it also remains unclear exactly how many practising hygienists are already wearing loupes, a situation which was a clear exclusion criteria in the current study. Another factor was the potential for confounding variables, such as the type of operator chair used, the type of practice worked in, and patient scheduling including breaks. However, as previously noted recruitment of participants was difficult, and further limiting the inclusion and exclusion criteria may have resulted in evener fewer participants, and the study would not have been viable. Despite the risk of potential confounders, this study allowed participants to work in their usual clinical settings over an extended period, which ensures authenticity.