Evaluation of hyoid bone movements in subjects with open bite: a study with real-time balanced turbo field echo cine-magnetic resonance imaging / 대한치과교정학회지

OBJECTIVE: To assess the position and movements of the hyoid bone during deglutition in patients with open bite. METHODS: Thirty-six subjects were divided into 2 groups according to the presence of anterior open bite. The open bite group (OBG) and control group each comprised 18 patients with a mean overbite of -4.9 +/- 1.9 mm and 1.9 +/- 0.7 mm. The position of the hyoid bone during the 4 stages of deglutition was evaluated by measuring vertical and horizontal movement of the bone. RESULTS: Interactions of group and stage showed no significant effect on the measurements (p > 0.05). However, when group and stage were evaluated individually, they showed significant effects on the measurements (p < 0.001). In OBG, the hyoid bone was more inferiorly and posteriorly positioned, and this position continued during the deglutition stages. CONCLUSIONS: The hyoid bone reaches the maximum anterior position at the oral stage and maximum superior position at the pharyngeal stage during deglutition. Open bite does not change the displacement pattern of the bone during deglutition. The hyoid bone is positioned more inferiorly and posteriorly in patients with open bite because of released tension on the suprahyoid muscles.

Relationship between Class III malocclusion and hyoid bone displacement during swallowing: a cine-magnetic resonance imaging study / 대한치과교정학회지

OBJECTIVE: The displacement of the hyoid bone (HB) is a critical biomechanical component of the swallowing function. The aim of this study was to evaluate the swallowing-induced vertical and horizontal displacements of the HB in subjects with 2 different magnitudes of skeletal Class III malocclusion, by means of real-time, balanced turbo-field-echo (B-TFE) cine-magnetic resonance imaging. METHODS: The study population comprised 19 patients with mild skeletal Class III malocclusion, 16 with severe skeletal Class III malocclusion, and 20 with a skeletal Class I relationship. Before the commencement of the study, all subjects underwent cephalometric analysis to identify the nature of skeletal malformations. B-TFE images were obtained for the 4 consecutive stages of deglutition as each patient swallowed 10 mL of water, and the vertical and horizontal displacements of the HB were measured at each stage. RESULTS: At all stages of swallowing, the vertical position of the HB in the severe Class III malocclusion group was significantly lower than those in the mild Class III and Class I malocclusion groups. Similarly, the horizontal displacement of the HB was found to be significantly associated with the severity of malocclusion, i.e., the degree of Class III malocclusion, while the amount of anterior displacement of the HB decreased with an increase in the severity of the Class III deformity. CONCLUSIONS: Our findings indicate the existence of a relationship between the magnitude of Class III malocclusion and HB displacement during swallowing.

Evaluation of anxiety level changes during the first three months of orthodontic treatment / 대한치과교정학회지

OBJECTIVE: To determine the changes in dental anxiety, state anxiety, and trait anxiety levels of patients and their parents after 3 months of active orthodontic treatment. METHODS: We evaluated 120 patients and one parent of each patient. State Anxiety (STAI-S), Trait Anxiety (STAI-T), and Corah's Dental Anxiety Scale (DAS) were administered before orthodontic treatment (T1) and after 3 months of treatment (T2). Differences in scores between T1 and T2 were compared using paired-sample t-tests and the relationship between the scores of the DAS and the STAI were analyzed using a bivariate two-tailed Pearson correlation test. RESULTS: Dental anxiety and state anxiety levels decreased among the patients after adjustment to orthodontic treatment (p 0.05). Patient trait anxiety affected patient state anxiety and dental anxiety (p < 0.01). Additionally, a significant correlation was found between patient dental anxiety and parent dental anxiety (p < 0.05). CONCLUSIONS: Dental anxiety and state anxiety levels decrease after patients become familiar with their orthodontist and they became accustomed to orthodontic treatment. However, 3 months is not a sufficient length of time to decrease parental anxiety levels.

Expansion of the mandibular arch using a trombone appliance / 대한치과교정학회지

OBJECTIVE: This case report describes orthodontic treatment of contracted mandibular arch using a trombone appliance. METHODS: A 14-year-old girl with Class II division 2 malocclusion, retroclined maxillary incisors, and buccally displaced maxillary canines required dental expansion in 3 spatial directions to correct the contracted maxillary and mandibular arches. In the initial phase of treatment, the maxillary arch was expanded and distalized using a quad-helix appliance and cervical headgear. Following the expansion and leveling of the maxillary arch, a trombone appliance was used to expand the mandibular arch. On correction of the mandibular arch and provision of sufficient space to level the mandibular teeth, fixed orthodontic treatment phase was initiated. RESULTS: A trombone appliance proved effective in correcting the contracted mandibular arch. Because of labiolingual and transversal expansion, the mandibular dental arch perimeter was increased by 7.4 mm; the misalignment of the mandibular teeth was corrected successfully. CONCLUSIONS: A trombone appliance may serve as an appropriate clinical alternative for treating moderate mandibular arch crowding caused by the contraction of the dental arch.