Researchers Examine How Clinical Environmental Factors Impact Ergonomics in Dental Hygiene Students

Dental professionals are at an increased risk of developing work-related musculoskeletal disorders (WMSDs). With prevalence rates reaching up to 81% among dentists and 96% among dental hygienists, WMSDs are a workforce retention concern. These disorders are driven by the strenuous nature of clinical work, specifically by repetitive hand movements and prolonged static postures involving neck and trunk flexion and rotation. The resulting discomfort, pain, and physical impairment, if left unaddressed, can lead to reduced working capacity, premature retirement, or career changes.¹

To reduce the impact of WMSDs on oral health professionals, further research is necessary to develop effective prevention and maintenance strategies – one such strategy is ergonomic education. Because work habits are typically first developed during dental education, curriculum design and preventive training are particularly important. However, about three-quarters of dental hygiene students still experience musculoskeletal pain despite the focus on ergonomics. This early onset likely results from students spending three times longer with patients than during a typical dental hygiene appointment, as well as extended computer use, which makes them susceptible to poor postural habits early in their careers.¹

The limited effectiveness of current ergonomic training may be attributed to the complex interplay between individual and clinical environmental factors that contribute to awkward, static postures and WMSDs. However, existing studies primarily focus on individual associations with musculoskeletal pain, such as scaling method and equipment use, sitting versus standing, or operator positioning. Yet none of these factors are performed in isolation, and research investigating the combination of risk factors in a clinical or educational setting is lacking.¹

To address this knowledge gap, a study examined how environmental factors, such as dental hygiene students’ working positions, patient positioning, area of the mouth being treated, and scaling method, collectively influence posture. By assessing these combined factors, the goal is to inform more effective ergonomic training, postural instruction, and clinical modifications in dental education programs to protect emerging dental professionals from the start of their careers.¹

The Study

This observational study followed 36 right-handed female undergraduate dental hygiene students at 2 universities across 3 consecutive semesters. To capture authentic behavior and minimize observer effects, researchers recorded 2–3-hour patient visits using a three-camera setup (front, side, and overhead) designed to blend into the clinical background. From these recordings, a team of 3 trained coders independently isolated video segments involving instrumentation, excluding other tasks such as patient education or assessment, to ensure a focused analysis of high-risk activity.¹

To evaluate physical strain, the researchers used the Rapid Upper Limb Assessment (RULA), a validated tool that scores posture, muscle use, and force to assess the risk of musculoskeletal disorders. In this study, muscle use and force were held constant to isolate the impact of posture alone. RULA scores are divided into two sections: section A (arm and wrist) and section B (neck, trunk, and legs), which are combined into an aggregate score ranging from 1 to 7. Generally, scores 1–2 indicate acceptable postures, 3–4 indicate moderate risk, and 5–7 indicate high risk postures. Because fewer than 3% of video observations showed acceptable postures (scores 1–2), the researchers simplified the data into a binary outcome, comparing high-risk postures (scores 5–7) with lower-risk postures (scores 1–4).¹

The data collection also tracked six specific environmental factors:

• Clinician clock position: The location of the student’s hips relative to the patient’s mouth.
• Clinician sit/stand position: Whether the student was seated or standing.
• Clinician scaling method: Whether the student was hand scaling or ultrasonic scaling.
• Patient chair position: Categorized as either supine (the angle between the floor and the back of the chair was less than 25 degrees) or semi-supine (the angle was between 25 and 55 degrees).
• Patient head position: Categorized as either left or right (the angle between the bridge of the patient’s nose and the jugular notch on the sternum was greater than 15 degrees). Otherwise, the position was considered neutral.
• Patient quadrant: The quadrant of the mouth the student was treating (upper left, upper right, lower left, or lower right).¹

For the final analysis, 10 instrumentation segments were randomly selected from each video using a time-weighted sampling method to accurately reflect the time spent in various positions. Using a custom computer program to automatically score these postures, the researchers then applied statistical methods to determine which specific mix of factors – such as patient chair position and scaling method – was most likely to put a student at high risk of injury.¹

The Results

The study’s analysis of 151 video observations yielded 1,487 final RULA scores, revealing a lack of acceptable postures among dental hygiene students. The overall average score was 4.8, and slightly over half (54.5%) of all observations fell into the high-risk category. While arm and wrist scores showed moderate strain, the scores for neck, trunk, and legs were heavily skewed toward higher risk, often reaching the highest risk levels.¹

Statistical testing identified clock position, scaling method, and the choice to sit or stand as the most significant factors influencing RULA scores. Specifically, sitting at the 12 o’clock position and ultrasonic scaling were associated with the lowest risk. In contrast, working from the 7 and 8 o’clock positions, standing during instrumentation, and hand scaling increased the likelihood of high-risk scores. Other environmental factors – such as the patient’s head position, quadrant being treated, and the chair angle – did not show a statistically significant impact on risk levels.¹

The final predictive model confirmed that the 7–8 o’clock position is the riskiest, increasing the odds of poor posture by more than 8 times compared to the 12 o’clock position. Every other clock position studied nearly doubled the risk of poor posture when compared to the 12 o’clock benchmark. Ultimately, the combination of hand scaling while standing at the 7–8 o’clock positions was more likely to result in high-risk RULA scores.¹

Limitations

Because the video observations exclusively evaluated right-handed female dental hygiene students, the researchers note that these findings are not intended to be generalized to all dental professionals, students, or left-handed clinicians. The analysis also did not explore additional personal and patient factors that may influence posture, such as practitioner age, skill level, and patient disease severity. Similarly, the study did not consider all potential environmental factors in clinical settings, such as instrument sharpness. Finally, the study could not explore the effect of magnification loupes on posture because all students wore them, and the video recordings did not allow researchers to verify if students were using them correctly (e.g., looking through rather than over them).¹

Methodologically, the interpretation of findings must be considered within the limits of the RULA assessment. By grouping moderate risk scores (3–4) with acceptable scores (1–2) to create a single low-risk category, the analysis likely presents a conservative estimate of postural risk and does not allow for a nuanced understanding of absolute best practices. Additionally, the presence of cameras may have triggered an “observer effect,” where students potentially improved their posture because they knew they were being recorded, despite mitigation efforts. Finally, because RULA serves only as a proxy for upper-extremity musculoskeletal disorder risk, future studies should further evaluate the development of WMSDs and related pain and symptoms.¹

Conclusion

This study highlights how environmental factors influence the postural risk of right-handed dental hygiene students. The findings indicate that clock position, sit/stand position, and scaling method are all predictors of high-risk RULA scores. The highest risk was associated with standing while hand scaling at the 7- or 8-o’clock positions. While clock positions 7 and 8 were the most hazardous, all clock positions within the 7–10 and 1–4 ranges were significantly associated with high-risk RULA scores. Even the commonly used 9 o’clock position was found to quadruple the risk of poor posture compared to the 12 o’clock position, where students can more easily maintain a neutral spine.¹

While magnification loupes are intended to improve posture, the study found that neck, trunk, and leg scores contributed more to the aggregate RULA outcomes than upper arm and wrist scores. This suggests that dental hygiene curricula may need to shift toward more targeted ergonomic education to reduce environmental hazards that might lead to awkward postures. Specifically, the data support the ergonomic benefits of ultrasonic scaling, which requires less head and neck inclination and wrist flexion, extension, and deviation than hand scaling. However, researchers note that the potential long-term risks of vibration should be considered. Previous studies suggest that prolonged exposure may affect soft tissues and nerve receptors, which could reduce tactile sensitivity and increase the risk of developing WMSD symptoms.¹

The researchers conclude that a practical insight from this study is the importance of considering multiple environmental factors together when educating students on ergonomic techniques, as reducing one may help mitigate the effects of others. For example, faculty could encourage students to avoid prolonged standing when hand scaling between clock positions 7 through 10, particularly at the 7–8 o’clock positions. Choosing a seated position instead at these clock positions may be preferable to help reduce postural risks. Ultimately, these findings emphasize the importance of dental hygiene education in structuring clinical training to minimize awkward postures associated with the development of WMSDs among students.¹

Before you leave, check out the Today’s RDH self-study CE courses. All courses are peer-reviewed and non-sponsored to focus solely on high-quality education. Click here now.

Listen to the Today’s RDH Dental Hygiene Podcast Below:

Reference

1. Willie, T.M., Fang, Y., Baker, N.A., et al. Environmental Factors Increasing the Risk of Poor Posture in Dental Hygiene Students. J Dent Educ. 2025; 89(9): 1310-1318. https://pmc.ncbi.nlm.nih.gov/articles/PMC12353362/