Tahereh Jalaly - Associate Professor, Department of Orthodontics, School of Dentistry and Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
Farzaneh Ahrari - Assistant professor, Department of Orthodontics, School of Dentistry and Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
Rasool Saheb Alam - Assistant Professor, Department of Pediatric Dentistry, School of Dentistry and Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
Foroozandeh Amini - Dentist

Objective: In spite of the continuous interest of orthodontists in the effects of soft tissues on dental and skeletal structures, this influence is not well clear. The purpose of this investigation was to clarify the effect of open lip posture on selected dentoskeletal features of growing children.Materials and Methods: In this cross sectional study, ۱۹۳ pupils (۹۹ girls, ۹۴ boys) with age range of ۹ to ۱۳ years were participated. All patients were examined by a trained investigator and those having incompetent lip seal were selected and their dentoskeletal features were compared with a control group consisting of ۳۶ subjects with normal occlusion. The data were analyzed by independent sample t-tests.Results: Among the ۱۹۳ students examined in this study, ۱۹ cases (۱۰%) were diagnosed as having lip incompetence. A more open lip posture was associated with an increase in overjet, lower incisor inclination and Palatal plane to Mandibular plane angle (p<۰.۰۵); while Interincisal angle was significantly decreased in this group compared to control subjects (p<۰.۰۵). The amount of overbite and upper incisor inclination were not statistically different between the two groups (p>۰.۰۵).Conclusion: The data from this study suggest that lip incompetence may have a significant environmental effect on dentofacial structures. Since lip seal assessment can be achieved simply by practitioners, parents or teachers, it is suggested that adults observe and provoke children to maintain appropriate lip posture. 

lip posture, dentofacial development, overjet, overbite, Cephalometry