Frequency of Dentoskeletal Factors Affecting Soft Tissue Chin Strain on Lip Closure in Class I And Class II Div I Malocclusion

Abstract

Introduction: Contemporary orthodontics includes the treatment of dental and skeletal disharmonies, including careful consideration of integumental features of the face. Whenever there is a protuberance of upper or lower incisors, attempts by patients to close their lips result in lip strain, which is supplemented by hyperactive mentalis muscle function and elevation of the integument of the chin. Orthodontic treatment usually corrects this problem and results in smoother soft tissue contours.¹

Objective: To assess the frequency of dentoskeletal factors (UI-N.Pog distance, overjet, UI-ULip distance) affecting soft-tissue strain of chin on lip closure in class I and class II div I malocclusion.

Material and Methods: Lateral Cephalograms and pretreatment frontal and lateral facial photographs of eighty patients were analyzed to calculate the angular and linear measurements.

The frequency of dentoskeletal factors (UI-N.Pog distance, overjet, UI-ULip distance) affecting soft-tissue strain of chin on lip closure in class I and class II div 1 malocclusion were assessed.

Result: Soft tissue chin strain was seen in Class I and Class II div 1 malocclusion when upper incisor-nasion pogonion (UI-NPog) distances were greater than 14.2 mm, Overjet was greater than 4.7 mm, or Upper incisor-upper lip (UI-ULip) distances were greater than 5.6 mm.

Conclusion: UI-NPog, with a cutoff estimate of 14.2mm, was used to categorize no-strain or strain subjects, followed by overjet, which had a cutoff estimation of 4.7mm, and UI-upper lip distance, which had a cutoff estimation of 5.6mm. Orthodontic treatment should aim to decrease UI-NPog distance, overjet, and UI-Upper lip distance values in order to achieve optimum esthetics and to achieve ideal or near-ideal appearing soft tissue contours in individuals with Class I and Class II div 1 malocclusions.