To investigate the perpendicular occlusal condition of the mesially impacted mandibular third molars and its relationship with temporomandibular joint disorders (TMD).

Thirty-seven cases of mesially impacted mandibular wisdom teeth were selected as the observation group, and 20 cases of other oral diseases without the mesially impacted third molars were selected as the control group from Jun 2012 to Sep 2014. Occlusion in the vertical, buccal-lingual and mesial-distal directions were analyzed with occlusion index. Depth of Spee curve was measured by AutoCAD software.

Prevalence of TMD of observation group (51.4%) was significantly higher than the control group (15.0%), the difference between the two groups was statistically significant (χ²=7.24, P=0.007). Observation group's vertical abnormal occlusion rate (40.5%) was significantly higher than the control group (10.0%), the difference between the two groups was statistically significant (P<0.05). Average depth of Spee curve in observation group and control group were (2.41±0.26) mm and (2.05±0.18) mm respectively, the difference was statistically significant (t=4.51, P=0.009).

Incidence of TMD in patients with mesially impacted mandibular wisdom tooth is higher than that of patients without mesially impacted mandibular wisdom tooth. Mandibular impacted wisdom tooth may cause vertical abnormal occlusion. TMD is related to vertical abnormal occlusion.