What determines dental protrusion or crowding while both malocclusions are caused by large tooth size? / 대한치과교정학회지

OBJECTIVE: To examine the differences in lateral cephalometric characteristics between patients with dental protrusion and crowding in order to determine what factors affect dental protrusion or crowding while both malocclusion types are caused by large tooth size. METHODS: Twenty nine individuals with dental protrusion and 22 individuals with dental crowding were enrolled in this study. All subjects had larger teeth than average and Class I molar relationships. Craniofacial characteristics and hyoid bone positions were determined from lateral cephalograms and compared between the two groups. RESULTS: In the comparisons of craniofacial characteristics, the measurements indicating maxillary length and facial convexity showed greater values in the protrusion group than in the crowding group. Comparisons of hyoid bone positions showed that the hyoid bone was positioned more anteriorly and superiorly in the protrusion group than in the crowding group. CONCLUSIONS: The results of the present study indicate that some craniofacial characteristics and tongue position may affect the development of dental protrusion or crowding; when an individual has large teeth, dental protrusion or crowding might be determined according to maxillary growth and tongue position.

Use of Head Posture Aligner to improve accuracy of frontal cephalograms generated from cone-beam CT scans / 대한치과교정학회지

OBJECTIVE: The purpose of the present study was to evaluate the effectiveness of the use of Head Posture Aligner (HPA) during cone-beam computed tomography (CBCT) scan in generation of frontal cephalograms using 3D CBCT images. METHODS: CBCT scans and frontal cephalograms were made in 30 adult individuals. While a couple of CBCT scan was made for one subject, one was made with conventional method, without use of HPA, the other was acquired with the use of HPA. After creation of virtual frontal cephalogram from each 3D CBCT image, it was traced and compared with the tracing of real frontal cephalogram. RESULTS: In the comparison of the measurements, the virtual cephalograms with the use of HPA did not show statistically significant differences with the real cephalograms whereas the virtual cephalograms without the use of HPA presented significant differences with real cephalograms in many measurements. In the correlation analysis with the measurements of the real cephalograms, the virtual cephalograms with the use of HPA showed higher correlations in all measurements than the virtual cephalograms without the use of HPA. CONCLUSIONS: Measurements from CBCT-generated cephalograms become similar to those from real cephalograms with the use of HPA during CBCT scan. Thus, the use of HPA is suggested during the CBCT scan in order to construct accurate virtual frontal cephalograms using 3D CBCT images.

Fracture strength of tie wings in a newly-developed polycarbonate bracket / 대한치과교정학회지

OBJECTIVE: With an increasing demand for esthetic orthodontic appliances, the interest in polycarbonate brackets has also increased. However, polycarbonate bracket wings are prone to fracture. The purpose of this study was to evaluate the clinical usefulness of a newly-developed polycarbonate bracket by measuring the fracture strength of bracket tie wings. METHODS: Alice (K.M. Daicom, Seoul, Korea) and Spirit MB (Ormco, Glendora, CA, USA) brackets were used as an experimental and control bracket respectively. Each bracket group was divided into halves. One half was untreated and the other half was treated with 2,000 times of thermocycling between 5 degrees C and 55 degrees C. The fracture strength of the wing was measured by a universal testing machine. RESULTS: Alice bracket wings showed significantly higher strength than Spirit MB bracket wings in both untreated and thermocycled bracket cases. CONCLUSION: Alice brackets may be used clinically in terms of the strength of bracket wings.