Objective To figure out the relationship between mandiblular midline deviation and gingival recession of maxillary first molar. Methods 32 cases with no losing teeth, no temporomandibular disorders, and the tooth erupts right on the arch（buccal version or lingual version should be excluded） were included. We take an alginate impression, and pour the cast with hard die-stone. Then we make a facebow transfer to set the maxillary cast on Class Ⅲ articulator, and mounting mandibular cast with centric relation bite registration. At last, we record the direction from centric relation to maximum intercuspation, and measure the palatal gingival recession of maxillary first molar. Results Among the 32 cases we have been studied on, there are 15 cases that have suffered from mandibular midline deviation and the rest 17 cases have not. There are 18 cases that have suffered from the palatal gingival recession of maxillary first molar, and the rest 14 cases have not. The correlation coefficient to determine the relationship between these two data is 0.828. It demonstrated that the 2 variables have high relevance. Conclusion Based on this finding, there is a big correlation between mandibular midline deviation and gingival recession of maxillary first molar.
