Objective To investigate the influence of different hardness bolus on bite force and the functional characteristics of masseter and temporalis-anterior muscle during unilateral maxmal biting .Methods PVC film was placed on the surface of mandibular second premolar and the first molar on one side of the subject , the contralateral same teeth were placed in doughy acrylic .Then the a-crylic resin piece was made by maxmal biting .Using T -Scan Ⅲbite analyzer and Bio-Pak EMG the bilateral maximum bite force and masseter and temporalis-anterior muscle activity were measured under ICP and unilateral biting .Results (1) During ICP maxmal bit-ing,no differences was found in EMG activity between bilateral temporalis -anterior muscles or between bilateral masseters .(2) During unilateral maxmal bitting , bilateral side of masseter muscle activity had no obvious difference (P>0.05), but EMG activity of the temporalis-anterior muscle on the biting-side(147.75 ±31.37)μν,(145.70 ±35.08)μνwere higher than that of the contralateral side (115.87 ±24.08)μν,(121.24 ±22.78)μν(P<0.05).(3)During unilateral maxmal biting, masseter muscle activity had no obvi-ous statistically significance when compared with ICP maximal biting (P>0.05), but the contralateral temporalis-anterior muscle val-ues(147.75 ±31.37)μν and (145.70 ±35.08)μν were much smaller than that of ICP maxmal biting (136.88 ±29.54)μν, the difference was statistically significant (P<0.05).(4) Unlateral occlusion, all the subjects (20/20) had the contralateral occlusal contact phenomenon.The bite force of soft bolus (9174.60 ±955.29)raw was bigger than that of he hard bolus (6156.70 ±979.27) raw (P<0.05).But the masseter and temporalis-anterior muscle activity in soft bolus had no obvious difference when compared with hard bolus (P>0.05).Conclusions Compared with hard bolus, the bite force of soft bolus is relatively smaller than that of hard bo-lus, the influence of different hardness of occlusal bolus has no significant effect on masticatory muscle .%目的：研究单侧最大紧咬不同硬度物质对咬合力和咬肌、颞肌前束的肌电值的影响。方法在受试者一侧下颌第2前磨牙与第1磨牙上放置聚氯乙烯（polyvinyl chloride，PVC）软片，对侧同名牙放置面团期丙烯酸树脂（acrylic resin， AR），最大紧咬时制取丙烯酸树脂片为硬物；使用T－ScanⅢ咬合分析仪和Bio－Pak肌电图仪测量受试者在牙尖交错位（ intercus－pal position， ICP）和单侧咬合软硬物下双侧最大紧咬时的咬合力和咬肌（ masseter muscle， MA）、颞肌前束（ temporalis－anterior muscle， TA）的肌电值。结果（1）ICP最大紧咬时，双侧MA肌电值、双侧TA肌电值均无明显差异（P＞0．05）；（2）单侧最大紧咬时，咬合侧与咬合对侧MA肌电值无明显差异（P＞0．05）；而咬合侧TA肌电值分别为（147．75±31．37）μν、（145．70±35．08）μν，均明显大于咬合对侧（115．87±24．08）μν、（121．24±22．78）μν，差异均有统计学意义（P＜0．05）；（3）单侧最大紧咬时，MA肌电值与ICP最大紧咬时相比差异无明显统计学意义，咬合对侧TA肌电值（147．75±31．37）μν和（145．70±35．08）μν均明显小于ICP最大紧咬时的TA肌电值（136．88±29．54）μν，差异有统计学意义（P＜0．05）；（4）单侧咬合时，所有受试者（20／20例）均出现了咬合对侧接触现象。单侧最大紧咬时软物的咬合力为（9174．60±955．29） raw，明显大于硬物的咬合力（6156．70±979．27）raw，差异有统计学意义（P＜0．05）；但软物最大紧咬时的MA和TA肌电值分别与硬物比较差异无统计学意义。结论与硬物相比，软物对咬合力的影响相对较小，但不同硬度咬合物对咀嚼肌肌电值无明显影响。
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