A short-term epidemiological study of median nerve dysfunction in practicing dental hygienists

The purpose of this study was to assess over time changes in median nerve function in a group of 20 students who entered the University of Minnesota dental hygiene program in 1986. This is a follow-up report on 16 of the 20 students who were evaluated two years postgraduation in 1990. Comparisons were made with prior evaluations of the subjects completed at graduation in 1988, and one year postgraduation in 1989. Digital vibrometry was used to evaluate median nerve sensibility threshold at each of the time periods studied. Analysis revealed that after one year of clinical practice, there was a mean sensibility threshold shift of 11.04% in the left median nerve and 8.42% in the right median nerve as measured by digital vibrometry. Results at two years postgraduation indicated that the threshold shift observed in an earlier study had been arrested. The reasons appeared to be twofold: (1) a period of work hardening with a concept of neuromuscular ligamentous tissue hypertrophy or adaptation to the rigors of dental hygiene practice, and/or (2) the practicing dental hygienist had learned to become more efficient in the provision of hygiene procedures. There were no reported symptoms of median nerve dysfunction and none of the subjects had been diagnosed as having CTS at any time during the two years since graduation. Continued evaluations will be necessary to determine whether the observations noted during the second year postgraduation evaluation indicated temporary or permanent slowing of the conditions necessary for the development of CTS.