齒模技工職業環境暴露與健康調查研究

Study on the Occupational Exposure and Health Concern of Dental Technicians

甲基丙烯酸甲酯單元體(Methyl methacrylate，MMA)及聚合體（聚甲基丙烯酸甲酯Polymethyl methacrylate，PMMA）在醫療上廣泛使用，在牙科方面則當作陶瓷用黏著劑的充填物及塑膠假牙。本研究隨機採樣不同規模大小之齒模技工所九家共40名操作 MMA 樹脂之員工為研究對象，對其作現場訪視、作業環境測定、問卷調查及健康檢查。以瞭解環境因素與職業傷害間的關聯性，提供齒模技術人員作業環境改善及推動健康促進之參考。作業環境測定結果 MMA 蒸氣濃度平均值為11.3ppm，總粉塵濃度幾何平均值為0.11mg/m3，可呼吸性粉塵濃度幾何平均值為0.01mg/m3，氣槍最大噪音為112.3dBA' 金屬床研磨最大噪音為89.7dBA，其噪音總劑量(D) 為53.8%，八小時日時量平均音壓級(TWA)為85.5dBA，皆符合法令之規定。研磨手機振動測定加權加速度值(WAS)為2.72m/s2。關於健康檢查神經系統之檢查部分結果，神經理學檢查中，有7位(23.3%)工作者之神經肌鍵反射(deep tendon reflex)低下；有3 位(10.0%)其肢體末端感覺異常；但未發現有肌肉萎縮或肌肉無力之現象，因此接觸 MMA 工作者，以感覺神經受傷之臨床表徵為主。神經傳導速率檢查(nerve conduction velocity)結果，於運動神經檢查發現以末端潛時(distal latency)異常之個案最多，佔34.2%。於感覺神經檢查則是以振幅下降之個案最多，佔26.3%。針對接觸 MMA 工作者，神經傳導速度檢查是一種非侵襲性且客觀的檢查方式，它可早期偵測周邊神經病變，作為健康監測指標。

Methyl methacrylate MMA monomer and polymer are extensively used in medical treatment. Their use in the field of dentistry include ceramics adhesive filling and plastic denture. Dental technicians who regularly use this resin often complain of numbness, paresthesia, and pain in the hands. The aim of this study is to clarify the neurotoxic effects of MMA in dental technicians.This study randomly chose 40 workers responsible for handling MMA resin from 9 tooth mold firms as research subjects. Questionnaires, health examinations, and workplace measurements were performed. The results of the workplace measurements are as follows: Average of MMA vapor concentration, 11.33ppm; geomean of total aerosol concentration, 0.11 mg/m3; geomean of respirable aerosol concentration, 0.01 mg/m3; instant maximum sound level for air cutter, 112.3dBA; instant maximum sound level for metal grounder, 89.7 dBA; daily noise dose is 53.8%; 8-hour time-weighted-average sound level is 85.5 dBA. All are below the current standards specified by the law. WAS (weighted acceleration sum) value of hand-arm vibration for metal ground is 2.72 m/s2. We recruited 40 dental technicians for detailed history review, neurological examination, and nerve conduction velocity study. The clinical signs study results show 7 workers, (23.3%) experience low deep tendon reflex and 3 (10.0%) have sense abnormality at the limbs ends. No muscle lacking strength is found. It is therefore summarized that workers handling MMA mostly demonstrate the sign of sense nerve damage. The results of nerve conduction study show that 34.2% of the worker have distal latency abnormality. The results of exam of sensory system show that amplitude drop account for most abnormality cases, 26.3%. For worker handling MMA, nerve conduction velocity study is a non-obtrusive and objective exam that is capable of detecting disease of peripheral nervous system in its early stage, and might be used as an indicator for health surveillance. The dental technicians exposed to MMA may develop sensory motor peripheral neuropathy. The nerve conduction velocity study provides an objective and non-invasive method to detect the early peripheral nervous dysfunction caused by MMA.