Objective
The purpose of this study was to determine whether lip incompetence relates to skeletal and dental discrepancies in growing and non-growing patients.
Materials and Methods
In this cross-sectional retrospective study, 1,028 subjects were divided into growing (GS) (6- to 17Y; n= 449; 266 F and 183 M) and non-growing groups (NGS) (18- to 68-years; n= 579; 391 F and 188 M). Lateral cephalograms and clinical records were used for analyzing skeletal pattern by the ANB and SN-MP. Lip competency parameters were assessed regarding the degree of perioral musculature activity and distance between upper and lower lips in the mandibular rest posture. The relationship between variables was assessed by Spearman correlation coefficients at a level of significance of 1%.
Result
For both of groups, subjects with lip incompetence presented considerably increased ANB, SN-MP and overjet values when compared to those with competent lips. Interlabial gap of skeletal Class II group correlated with both sagittal and vertical measurements (P < 0.05), whereas Class III group correlated only with the vertical ones (P < 0.05). On the other hand, no correlation was found between the vertical component and lip incompetency in skeletal Class I subjects.
Conclusion
Lip incompetency was not proportionally correlated with underlying hard tissue morphology, especially in Class I subjects. On the other hand, lip incompetency was associated with both horizontal and vertical factors in skeletal Class II and only with vertical one in skeletal Class III. An orthodontic total arch intrusion in both growing and adult patient was proposed.