Comparison of Treatment Effects of Herbst and Advansync Appliances on Hyoid bone position and Cervical posture in Skeletal Class II Malocclusion – A Prospective Randomized Clinical Trial

Archana Jaglan,*
Seema Grover,
Namrata Dogra,
Pandurangan Harikrishnan

Abstract

Background: Mandibular retrusion is the most common cause of Class II Division 1 malocclusion, which needs correction of the underlying skeletal discrepancy. The objective of this study was to evaluate the Hyoid bone position and cervical posture changes following treatment with two fixed functional appliances - Herbst and AdvansyncTM (Ormco, Orange, CA, USA) appliances in skeletal Class II malocclusion using pre and post treatment lateral cephalograms. Methods: For this randomized controlled trial, 40 patients (21males and 19 females) were divided into two groups Group I, Herbst Appliance group (mean age: 12.6 +/- 0.67 years) and Group II, AdvansyncTM group (mean age: 12.8 +/- 0.66yrs). Pre and post-treatment (after appliance therapy of 8 months duration) lateral cephalograms were evaluated using Planmeca Romexis software 5.0.0.R version for hyoid bone position and cervical posture changes. Results: The Hyoid bone had displaced anteriorly by 1.64 mm in Group I and in Group II by 1.97 mm. There was downward displacement of hyoid bone by 1.73 mm in Group I and 2.03 mm in Group II with reference to the Frankfort horizontal (FH) plane. The Mandibular plane-Odontoid process tangent angle used for determining upper cervical posture decreased by 7.13o in Group I, while by 0.33 o in Group II. Conclusion: This study concluded that both Herbst and Advansync appliances showed an improvement in hyoid bone position and the cervical posture while Advansync appliance demonstrated greater uprighting of cervical posture which was statistically significant.