This study examined the differences in the masticatory function of patients with temporomandibular disorder (TMD) in Korea. The experimental groups were as follows: 23 patients with painful arthralgia classified as pain group according to the research diagnostic criteria for temporomandibular disorder (RDC/TMC) and 28 patients with pain-free disc displacement and reduction classified as clicking group. The subjects were obtained from those who had visited Yonsei University Dental Hospital from 2007 to 2008. Twenty dental students without TMD symptoms were enroled as the normal control group. The Mixing Ability Index (MAI) was used as the objective index, and the Food Intake Ability (FIA) Index, Visual Analogue Scale (VAS) and oral health impact profile (OHIP) were used as the subjective indices. The MAI, FIA and VAS were significantly lower in the pain group than in the normal and clicking groups (P<0·05). The pain group showed a MAI, FIA and VAS of 16%, 81% and 67%, respectively, compared to that of the normal group. However, there were no significant differences in the MAI, FIA and VAS between the clicking and normal groups. The pain and clicking groups showed a 1·7 and 1·4 times higher OHIP value than the normal group (P<0·05). The MAI and subjective indices, such as the FIA (r=0·40) and VAS (r=0·48), showed a moderate correlation (P<0·01). In conclusion, pain is the main factor for the reduced masticatory function in patients with TMD in Korea, and the joint sound, not the masticatory function, affects the declining OHIP.
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