BACKGROUND: Through the years denture processing with polymethyl methacrylate (PMMA) has been studied extensively to achieve outstanding physical properties and the natural aesthetics of the material. However, the hazardous effect that methyl methacrylate (MMA) monomer brings to the dental technician while handling the material during denture fabrication remains the same.


OBJECTIVES: The general objective of the study was to evaluate the peripheral neuropathy among dental laboratory technicians exposed to methyl methacrylate in comparison to unexposed control. The specific objectives were to (a) compare urine levels of monomer derivative trichloroethyl methacrylate ester among exposed and unexposed workers; (b) characterize local neurotoxicity based on the following criteria: clinical manifestations on fingers and hands, nerve stimulation tests on motor and sensory nerves, dynamometer measurements on hand and pinch grips, and sensory modalities; and (c) determine the possible relationship between methyl methacrylate exposure and local neurotoxicity.


METHODS: A cross sectional design was used to compare two sets of technicians: the exposed group (n=48) and unexposed group (n=26). The following procedures were done on all subjects: measurement of urine levels of the monomer derivative, survey of clinical signs and symptoms being experienced, nerve stimulation tests on specific sensory and motor nerves, measurement of hand and pinch grips, and neurological examination for sensory perception changes.


RESULTS: Urine levels of the monomer derivative trichloroethyl methacrylate ester was detected more frequently among the exposed (54 percent) than the unexposed (4 percent). Clinical signs and symptoms reported by both groups of subjects were numbness, coldness, pain and pallor. Sixty percent of the exposed and 54 percent of the unexposed manifested at least one of these signs and symptoms. Sixty-four percent of exposed subjects had abnormal nerve stimulation test results compared to 11 percent among the unexposed. Ten percent of the exposed had below normal grips with concomitant abnormal nerve stimulation test against 4 percent among the unexposed. Among the exposed technicians sensory changes in pain, vibration and temperature perceptions were observed (12 percent) which ranged from mild to severe deficits. However, there were no statistically significant associations found between urine levels of the derivative, signs and symptoms, grip measurements, sensory perceptions, and the resulting abnormal nerve stimulation tests. Logistic regression analysis showed that peripheral neuropathy was significantly associated with work exposure to the monomer (p < 0.02) which places exposed technicians at higher risk of developing the disease than the unexposed.


CONCLUSIONS: This study confirms that work exposure to the MMA monomer gives rise to acquired peripheral neuropathy that is of axonal degeneration type with concurrent demyelination. However, this methyl methacrylate-related peripheral neuropathy is not always accompanied by clinical signs and symptoms, abnormal hand and pinch grip measurements, changes in sensory modalities and elevated urine levels of the monomer derivative. Subclinical cases of peripheral neuropathy can also occur. (Author)

In: Acta Medica Philippina, 2007 vol. 41 (1) pages: 24-28