The influence of mandibular divergence on facial soft tissue thickness in class I patients: a cephalometric study.

Background: The aims of this study were to evaluate the association between mandibular divergence and facial soft tissue thickness (FSTT) measured at different profile levels, and the gender difference in FSTT.
Materials and Methods: Lateral cephalograms were used to examine nine linear distances: the glabella area (G-G1), nasal (N-N1) and subnasal area (A-Sn), upper (Sd-Ls) and lower lip thickness (Id-Li), mentolabial sulcus (B-Sm), chin area (Pg-Pg1), gnathion area (Gn-Gn1) and menton area (Me-Me1) in 155 adult Caucasian subjects (79 males, 76 females) from the central Balkan area. Subjects were divided into three groups according to the ANB angle, Wit's appraisal and SN/GoGn angle into normodivergent (28 male, 27 female subjects), hypodivergent (26 males, 25 females) and hyperdivergent (25 males, 24 females).
Results: Progressive decreasing in the soft tissue thickness from hypo- towards hyperdivergent group was established in N-N1, A-Sn, Gn-Gn1, Me-Me1. There are significant differences in Gn-Gn1 and Me-Me1 (p < 0.02). Progressive increasing of FSTT happens only at the level of mentolabial sulcus and these differences are significant. Significant gender differences were established for the following distances: N-N1 in hyperdivergent, A-Sn in all three examined groups, the upper lip thickness in normo- and hyperdivergent, the lower lip thickness in hypodivergent, the thickness of mentolabial sulcus in hypo- and normodivergent, Pg-Pg1 in hyperdivergent and Me-Me1 in normodivergent subjects (p < 0.05).
Conclusions: Facial soft tissue thickness showed a various degree of dependence on vertical developmental pattern at different levels of measurement. The areas whose thickness is significantly conditioned by this pattern were established: the chin area at level Gn-Gn1, Me-Me1 and the region of the mentolabial sulcus (B-Sm). At most levels, male subjects have thicker soft tissues and these differences are significant for all three groups in the subnasal area.