Comparison of frictional forces between aesthetic orthodontic coated wires and self-ligation brackets / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the clinical efficacy of polymer- and rhodium-coated wires compared to uncoated wires by measuring the frictional forces using self-ligation brackets. METHODS: 0.016-inch nickel titanium (NiTi) wires and 0.017 x 0.025-inch stainless steel (SS) wires were used, and the angulations between the brackets and wires were set to 0degrees, 5degrees, and 10degrees. Upper maxillary premolar brackets (Clippy-C(R)) with a 0.022-inch slot were selected for the study and a tensile test was performed with a crosshead speed of 5 mm/min. The maximum static frictional forces and kinetic frictional forces were recorded and compared. RESULTS: The maximum static frictional forces and the kinetic frictional forces of coated wires were equal to or higher than those of the uncoated wires (p < 0.05). The maximum static frictional forces of rhodium-coated wires were significantly higher than those of polymer-coated wires when the angulations between the brackets and wires were set to (i) 5degrees in the 0.016-inch NiTi wires and (ii) all angulations in the 0.017 x 0.025-inch SS wires (p < 0.05). The kinetic frictional forces of rhodium-coated wires were higher than those of polymer-coated wires, except when the angulations were set to 0degrees in the 0.016-inch NiTi wires (p < 0.05). CONCLUSIONS: Although the frictional forces of the coated wires with regards to aesthetics were equal to or greater than those of the uncoated wires, a study under similar conditions regarding the oral cavity is needed in order to establish the clinical implications.

A study on craniofacial growth analysis of Korean children by the finite element method / 대한치과교정학회지

Craniofacial complex is influenced by numerical skeletal elements. Though the analysis of growth change has been done by various analytical methods, it was dependent on any method of registration and superimposition, based on reference plane and reference point. However, the craniofacial growth is composed of a number of local growth elements. Therefore, it will be necessary to use a clinically useful method for estimating craniofacial skeletal growth independently. The author analysed longitudinal cephalometric roentgenogram of 15 Korean males and 15 Korean females aged from 6 to 12 years by the finite element method and results were as follows: 1. The finite element method for craniofacial skeletal complex and soft tissue made it possible to analyze the independent local growth. 2. Regression equations from the value of each strain will make it possible to predict the craniofacial growth. 3. The growth of anterior cranial base was different from that of other facial bone. 4. The growth of posterior cranial base influenced the growth of upper pharyngeal region, mid-facial region, maxilla and posterior region of mandible. 5. The growth of maxillary complex was vertical rather than horizontal. 6. The growth direction of ramus, mandibular body, alveolar bone was various. 7. The relation between hard tissue and soft tissue by finite element method was variant.

A cephalometric study on the hard and soft tissue changes by the rapid palatal expansion in Angle's Class III malocclusion / 대한치과교정학회지

This stydy was undertaken to evaluate the cephalometric changes of the soft tissue and skeletal profile subsequent to the palatal expansion in 25 Angle's Class III cases, ranging in age from six to fifteen years, with cross-bite of the anterior teeth, underdevelopment of maxilla and facial disharmony. Following results were obtained: 1. ANS moved downward, Point A presented forward & downward movement increasing SNA and point B presented backward & downward movement decreasing SNB. 2. Mandible was rotated to backward & forward and maxilla moved forward & downward with the bite opening and improvement of anterior teeth cross-bite. 3. Soft tissue on inadible was rotated to backward & downward rotation of Point B', Pog'. 4. Respones of the upper lip was more significant in downward than forward direction, and correlated with the upper central incisor and mandible rotation. 5. Reaponse of the lower lip was mord significant in downward than backward direction, and correlated with the mandible rotation. 6. There was a rather high degree of correlation between skeletal porfile and soft-tissue profile, :LS, 1:Pog', Pog:LS, Pog:LI:Pog' in horizontal measurements and 1:Pog', Pog:LI, Pog:Pog' in vertical measurements.