Document Type: Original Article


Assistant Professor, Department of Orthodontics, School of Dentistry, Shiraz University of Medical Sciences


Statement of Problem: The prevalence of Cl. III malocclusion has been reported to be various among different races (3-5%). Early treatment of this malocclusion is highly recommended.Purpose: This study was performed to determine the effect of chin cap in early treatment of Cl. III malocclusion on the nasomaxillary complex and mandible.Materials and Methods: In a cases control study, 40 Cl. III patients treated by upper jaw appliance and chin cap, on the basis of reverse overjet and/or concave profile, were chosen. The mean force was measured to be 200 gr on each side for 18 hours/day. The mean age was 8.5±2 years old while 55% were female and 45% were male. The analysis of cephalometric data before and after treatment were done considering the skeletal, dental and soft tissue variables. The mean treatment period was 22+12 months and was continued until 34 months.Results: Cephalometric measurements showed the following changes: SNA=0.5±1.313, Co-Po.A=2.7±2.348, SNB=-1.7±1.555, GoGnSN=1.7±1.605, NPog-FH=1.1±2.466, LAFH=2.8± 2.772, Wit’s=2.7±1.872, ANB=1.1±1.331, IMPA=-3.1±4.298, 1 to NA=3.1±5.078 demonstrating an increase in anteroposteiror indices of maxilla, vertical change of mandibular growth and a change in the angle of anterior teeth of upper and lower jaws. Changes in upper and lower pharyneal space were not statistically significant.Conclusion: There was a negative correlation between the effect of chin cap therapy and age which was appeared in the early stages of its application.Key words: Cl. III malocclusion, Chin cap, Cephalometric evaluation