in cases where the chin is well positioned at the beginning of the treatment [1, 7], pogonion kept in the same position to increase the lower facial height ; class II division II low-angle malocclusion uncorrected by orthodontic treatment alone, especially in patients that need advancement but have an excessive mental projection ; mandibular vertical alveolar deficiency; anterior open bite; mandibular ramus sagittal split osteotomy relapse; cases of condylar agenesis and hypoplasia; lateral open bite [4, 10]; and in cases that need a profound change in the mentolabial sulcus [1, 11].
Both techniques yielded long-term stability even though TMAO had better results in reducing the depth of the mentolabial sulcus. This finding has proven a clinical significance in using TMAO for those patients in whom an alteration in the mentolabial sulcus is desired.
In addition, the mentolabial sulcus was significantly deeper in controls (p = 0.05) and the length of the lower lip was decreased in the experimental group in comparison with the control group (p = 0.015).
The mentolabial sulcus was significantly different among the subjects in our sample; it was shallower in the experimental group, possibly because the lower lip is too stretched as it tries to be as close as possible to the upper lip, which is slightly retrusive according to the S-line.
The lower lip was the most affected of all soft tissue structures in both anteroposterior and vertical planes in our study, as mentioned earlier, and its relation with the chin, therefore, was also affected; the mentolabial sulcus was shallower in the group having missing teeth.
Although the majority of soft tissue variables were not statistically significant between our experimental and control groups of the sample, some were significant, such as the lower lip retrusion, mentolabial sulcus depth, and the length of the lower lip.
The Turkish norms had the following statistically significant differences: larger facial convexity angle (P = 0.035), lower face-throat angle (P = 0.004), nasolabial angle (P = 0.001), and upper lip protrusion (P = 0.005), more retruded pogonion (P = 0.043), deeper mentolabial sulcus (P = 0.001), and smaller interlabial gap (P = 0.046).
The mentolabial sulcus depth was significantly greater in Turkish adults than in the European-Americans; perhaps this might be attributed to mandibular retrusion.
North Indian subjects had convex profile, more obtuse lower face-throat angle, protrusive lips, acute nasolabial angle, deep mentolabial sulcus, and shorter interlabial gap than in European-Americans .
Postburn deformity of lip-chin complex: a method to restore the mentolabial sulcus
. Int J Oral Maxillofac Surg.