Background and Purpose. This study compared upper quarter muscle balance of working female dental hygienists and non-dental hygiene females who had no history of upper quarter pathology. The upper quarter was operationally defined as the shoulder and neck region; and muscle balance, as muscular flexibility and muscular performance. Muscular performance was operationally defined as a combination of strength and endurance.

Subjects. The study group consisted of 41 working dental hygienists between the ages of 22 and 60 years with a mean age of 38 years. The control group consisted of 46 non-dental hygienists between the ages of 20 and 54 years with a mean age of 29 years.

Methods.Passive muscular flexibility of the upper trapezius and levator scapula was measured using an inclinometer. Passive muscle length testing of the pectoralis major and minor was assessed using the Kendall Technique. Subjects were also instructed to maintain four different positions using isometric muscular contractions, each position representing a different group of scapular stabilizers. Muscle performance was measured by timing the duration, in seconds, of each of the four positions held. Additionally, all subjects filled out the Northwick Park Neck Pain Questionnaire (NPNPQ). Analysis of Covariance (ANCOVA) was used during data analysis to adjust for the age difference between groups.

Results. The results of this study suggest that female dental hygienists are more likely than non-dental hygiene females to develop tightness in the upper trapezius (p=0.007) and the levator scapula (p=0.01) of the non-dominant upper quarter. Muscle performance trends in the dental hygiene group for the serratus anterior position, upper trapezius and levator scapula position, and the pectoralis minor and lower trapezius position supported popular muscle balance theory that short muscles remain strong while lengthened muscles become weaker. Statistical significance was not achieved in any of the muscular performance measures because of high variability in the holding times for the testing positions. The dental hygiene group had higher totals in all nine parts of the NPNPQ (higher totals represent more pain complaints) compared to the non-dental hygiene group. Mean differences for five of these parts were statistically significant (p<0.05).

Conclusion and Discussion. The results of this study suggests that muscular imbalances in the upper quarter are more common in female dental hygienists than in female non-dental hygienists and may contribute to the numerous upper quarter pathologies associated with the profession of dental hygiene.

Key Words: Dental hygiene, Over-use disorder, Muscle balance, Disability

LLU Discipline

Physical Therapy


Physical Therapy


School of Allied Health Professions

First Advisor

Joseph Godges

Second Advisor

Everett B. Lohman III

Third Advisor

Sharon P. Anderson

Fourth Advisor

Joni A. Stephens

Fifth Advisor

Grenith J. Zimmerman

Degree Name

Doctor of Physical Therapy (DPT)

Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Muscular Diseases -- rehabilitation; Muscle Fatigue -- physiology; Shoulder Pain -- physiology; Shoulder Pain -- rehabilitation; Neck Pain -- physiology; Neck Pain -- rehabilitation; Postural Balance -- physiology; Dental Hygienists; Female; Occupational Diseases; Disability Evaluation; Self-Assessment; Isometric Contraction; Chi-Square Distribution; Factor Analysis, Statistical.



Page Count

vi; 41

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives