American journal of orthodontics最新文献

This article investigates the relationship of skeletal facial pattern and soft-tissue nasal form. The case sample comprises 123 white female subjects, aged 11.0 to 20.6 years, with no histories of pathology, trauma, surgical intervention, or orthodontic treatment. Measurements were made from cephalometric radiographs, posteroanterior radiographs, and the physioprint photographs. Skeletal classifications were based on the relationship of the maxilla to the mandible; the three classifications were straight profile, retrusive chin profile, and prognathic profile. Pearson product-moment correlation coefficients were used to test intercorrelations of all quantitative variables (including age) with each other. Correlations were highly significant for age, the three profile measurements, and two of the frontal measurements. Hence, noses and skeletal structures showed, as expected, increases with age. Also, profile measurements were highly significantly correlated; larger noses were larger in all profile dimensions. A stepwise discriminant analysis was used to study nonquantitative categories of nasal shape (straight, convex, and concave). This analysis indicated that more than 86% of patients in the sample of 123 demonstrated a correlation of nasal shapes with specific skeletal groupings. Patients with straight profiles tended to have straight noses; convex profiles accompanied convex nasal shapes; and concave profiles were found with concave nasal shapes. The clinical significance of this research is to emphasize the importance of total facial harmony (especially nasal shape) during orthodontic diagnosis and treatment planning.

In this exhaustive review, a number of parameters related to maxillary and mandibular second molar-extractions are discussed. The parameters reviewed include the timing of extractions and the effect of extractions on third molar eruption, posterior interdigitation, and incisor imbrication. The advantages and limitations of this procedure are outlined. The available information strongly suggests that the extraction of second molars relieves crowding in the posterior part of the arch, causes faster eruption of third molars, and diminishes the number of unerupted and/or impacted third molars. Consideration of the decrease in the number of impacted third molars after second molar extraction should be balanced with the fact that the extracted teeth are usually sound and are unimpacted. In addition, the third molars that do erupt frequently are poorly angulated and/or in poor contact with the first molars. This will necessitate an additional “late” period of fixed-appliance therapy to bring these teeth into good occlusion.

In this study eight macerated, human child skulls (dental age approximately 9.5 years) were subjected to a standardized high-pull headgear traction system. Tensile forces from 0.5 to 3.5 N (1 N = 0.1 kgf) per side were produced to the maxillae. Displacements of skeletal components were determined at 22 indicator points per skull by means of laser holography. Coordinated displacements and variations in amount and direction were established in all skulls. The overall amount of displacements was primarily a characteristic of an individual skull, not of a particular displacement. On the average, the maxillae were displaced in a slightly downward and posterior direction almost parallel to the occlusal plane. No deformations of skeletal components were seen. Results indicated that initial displacements of the maxillae and other skeletal components are not in the same direction as the direction of applied forces.