Facial growth: separating shape from size.
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Optical surface scanning technologies produce dense three-dimensional (3D) data sets, which allow detailed analysis of surface morphology. This paper describes a method of analysing change in facial shape independently of change in size. The 3D data from three male subjects from the age of 6-21 years were recorded using an optical surface scanner. A series of 22 conventional landmarks were located with the aid of horizontal and vertical profiles across the face, and were analysed using geometric morphometrics. The 3D landmark co-ordinates were scaled and aligned using Generalized Procrustes Analysis (GPA) and analysed by Principal Component Analysis (PCA) to determine the shape change over the growth period for each individual. The results show that the centroid size reaches a steady value at different times for each of the subjects. When analysing shape versus age, highly significant correlations were found with principal component 1 (PC-1), but not with other principal components. PC-1 encompassed 40 per cent of the total variance for each subject. The movement of facial landmarks with time that is represented by PC-1 in each of the individuals is described. The use of these techniques has enabled the individual characteristics of facial growth to be identified and also has revealed the subtle changes in shape that continue after change in size has ceased. (+info)
Analysis of Holdaway soft-tissue measurements in children between 9 and 12 years of age.
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In this study, 43 lateral cephalometric radiographs from 20 boys and 23 girls subjects were used to determine the Holdaway soft tissue growth changes. Subjects with Class I occlusions, balanced skeletal profiles, normal growth and development, and no orthodontic treatment history were included in the investigation. The cephalometric measurements were carried out on the first and second radiographs of each subject, with an average interval of 5 years. The growth changes in both sexes were analysed separately. The changes resulting from growth and development were determined by a paired t-test. The results showed that all measurements were significant at various levels except for upper lip sulcus depth, subnasal-H line distance, and lower lip H distance in girls, and upper lip sulcus depth, subnasal-H line distance, H angle and lower lip H line distance in boys. The measurement differences were observed with a Student's t-test. No significant difference was found for any measurement except upper lip base thickness (P < 0.001) and upper lip thickness (P < 0.01). The following measurements during the observation period were statistically different: soft-tissue facial angle (P < 0.01 in girls, P < 0.05 boys), nose prominence (P < 0.001 in girls and boys), skeletal profile convexity (P < 0.001 in girls, P < 0.01 in boys), basic upper lip thickness (P < 0.001 in girls and boys), upper lip thickness (P < 0.05 in girls, P < 0.001 in boys), H angle (P < 0.001 in girls), lower lip sulcus depth (P < 0.001 in girls and boys), and soft-tissue chin thickness (P < 0.001 in girls, P < 0.001 in boys). (+info)
The influence of orthodontic extraction treatment on dental structures: a two-factor evaluation.
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The purpose of this investigation was to evaluate the effects of different growth patterns and treatment types on dentoalveolar structures in patients treated with fixed Edgewise mechanics and the extraction of four first premolars. A total of 41 patients with a mean chronological age of 14 years 7 months and skeletal age of 14 years 6 months were included in the study. The type of growth pattern was assessed as mesio- or hyper-divergent, and the treatment type as the use or non-use of headgear. The results were analysed by two-way analysis of variance (ANOVA). The decrease in overbite in the mesiodivergent group was statistically significant when compared with the increase in the hyper-divergent group (P < 0.01). Extrusion of the lower molar was observed in all groups, and a statistically significant difference was found between the mesio- and hyper-divergent groups (P < 0.05). Interaction between growth pattern and treatment type was not found to be significant for any variable. It can be concluded that premolar extractions and the use of headgear with fixed appliances does not significantly change the overjet, occlusal plane angle, upper and lower anterior dentoalveolar heights, upper posterior dentoalveolar height, or the inclination of the upper and lower incisors. The only significant changes were observed in overbite as a result of treatment mechanics and in lower posterior dentoalveolar height due to the growth pattern. (+info)
Craniofacial growth and skeletal maturation: a mixed longitudinal study.
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The purpose of this study was to investigate the relationship between craniofacial growth and skeletal maturation. The material consisted of the cephalometric and hand-wrist film pairs of 35 males and 43 females (78 subjects) whose development was followed for a period of 4 to 7 years. The subjects were grouped according to their skeletal maturation. Their mean ages were: Group I 10.27, Group II 11.55, and Group III 14.79 years, respectively, at the beginning of the observation period. Intra- and inter-group differences were examined through paired t-tests, and Pearson correlation analysis was used to detect the relationship between craniofacial growth and skeletal maturation (percentage growth potential). The results show that the middle cranial base (T-W) maintained its stability in all pubertal growth periods. However, posterior cranial base length (T-Ba) increases significantly (P < 0.001) throughout the same period. There were similar increases in the vertical dimensions of the face and alveolar height throughout pubertal growth. Despite the intensified increases in both the sagittal and vertical directions, facial characteristics were constant in the sagittal direction. The skeletal development (percentage growth potential) has clearly been effective in the vertical facial development commencing in Group I and reaching its maximum level in Group II. However Cd-Go was the exception. (+info)
The effect of zigzag elastics in the treatment of Class II division 1 malocclusion subjects with hypo- and hyperdivergent growth patterns. A pilot study.
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The aim of this study was to investigate the effect of zigzag elastics in the treatment of Class II division 1 malocclusion subjects with hypo- or hyperdivergent growth patterns. Two groups were established, each consisting of 10 subjects classified as hypo- or hyperdivergent according to their pre-treatment SN-GoGn angle. The cephalometric radiographs taken before and after an elastic application period of approximately 4 months were used to generate 22 variables. In both groups, there were no statistically significant differences in the vertical position of the lower molars, the SN-GoGn angle or the inclination of the lower incisors, whereas the sagittal skeletal relationship was improved as a result of an increase in the SNB angle and the mandibular length (P < 0.01). Upper incisor extrusion was statistically significant in both groups (P < 0.05). The downward rotation of the occlusal plane and the increase in overbite were found to be significant in the hypodivergent group (P < 0.05). Significant differences were observed between the groups in the extrusion of the upper incisor, the inclination of the occlusal plane, and the amount of overbite (P < 0.05). The results show that the zigzag elastic system is preferable, especially in hyperdivergent Class II division 1 subjects, as the use of such elastics does not cause an unfavourable effect on vertical jaw base relationship. (+info)
Good occlusal practice in children's dentistry.
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The difference between paediatric dentistry and most other branches of dentistry is that in the child the occlusion is changing. Consequently 'Good Occlusal Practice' in children is a matter of making the right clinical decisions for the future occlusion. The clinician needs to be able to predict the influence that different treatment options will have on the occlusion when the child's development is complete. (+info)
Cleft lip and palate: a review for dentists.
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The goals of primary closure of cleft lip and palate include not only re-establishing normal insertions for all of the nasolabial muscles but also restoring the normal position of all the other soft tissues, including the mucocutaneous elements. Conventional surgical wisdom, which recommends waiting until growth is complete before undertaking surgical correction of the postoperative sequelae of primary cheiloplasty, carries with it many disadvantages. If, after primary surgery of the lip, orolabial dysfunctions remain, they will exert their nefarious influences during growth and will themselves lead to long term dentofacial imbalances. These imbalances can significantly influence facial harmony. Unless accurate, symmetric and functional reconstruction of the nasolabial muscles is achieved during the primary surgery, not only will the existing dentoskeletal imbalances be exaggerated, but other deformities will be caused during subsequent growth, among which the most important are nasal obstruction and mouth breathing, reduced translation of the maxilla, dysymmetry of the nose and inability of the patient to symmetrically project the upper lip (+info)
Morphological differences in the craniofacial structure between Japanese and Caucasian girls with Class II Division 1 malocclusions.
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The craniofacial features of 49 Japanese and 75 British Caucasian girls with Class II division 1 malocclusions were evaluated from lateral cephalometric radiographs, and the morphological differences between both races were examined. The subjects' ages ranged from 11 years 1 month to 12 years 11 months. The mean values of 13 linear and 13 angular cephalometric parameters were compared. The Japanese Class II division 1 sample had a significantly shorter anterior cranial base length (S-N; P < 0.001) and a more obtuse articular angle (S-Ar-Go; P < 0.001). Analysis of the dentoalveolar components in Japanese subjects showed more proclined lower incisors (L1/Go-Me; P < 0.05) and a steeper occlusal plane (Occ.P/S-N; P < 0.01) relative to those of Caucasians. The short anterior cranial base length and excessive vertical development in the Japanese population might be common racial morphological features, but the main reason for the Class II division 1 skeletal disharmony in both races was different; it was caused by the anteriorly positioned maxilla in Caucasians and the backward rotated mandible in the Japanese. (+info)