Vertical changes following orthodontic extraction treatment in skeletal open bite subjects. (41/289)

The purpose of this investigation was to assess the vertical changes occurring in skeletal open bite patients treated orthodontically with different extraction patterns. The study was conducted using lateral cephalometric radiographs taken before and after treatment. Fifteen patients who had an anterior open bite (AOB) only were treated with first premolar extractions (Group E4). Seventeen patients with an AOB extending to the posterior teeth were grouped according to the extractions: extraction of second premolars (Group E5) and first molars (Group E6). Cephalometric data were analysed according to the 'two-factor experiment with a repeated measure on one factor' model. The treatment group factor had three levels, E4, E5, and E6, and the time factor two levels, pre- and post-treatment. The differences between the pre- and post-treatment periods were statistically significant for all the cephalometric variables (P < 0.001, P < 0.0001), except for ANS-Me/Na-Me. The time and group interaction were found to be statistically significant for the variables where the time factor is important, such as SN-GoGn angle, SGn-NBa angle, ANS-Me dimension, Na-Me dimension, forward movement of the maxillary and mandibular molars, and the distance to the mandibular plane of the lower molars. The severity of vertical dysplasia did not change in group E4. Generally, however, within the appropriate indications, extraction of the second premolars or the first molars led to a closing rotation of the mandible in subjects with a skeletal AOB extending to the posterior teeth.  (+info)

A geometric morphometric study of regional differences in the ontogeny of the modern human facial skeleton. (42/289)

This study examines interpopulation variations in the facial skeleton of 10 modern human populations and places these in an ontogenetic perspective. It aims to establish the extent to which the distinctive features of adult representatives of these populations are present in the early post natal period and to what extent population differences in ontogenetic scaling and allometric trajectories contribute to distinct facial forms. The analyses utilize configurations of facial landmarks and are carried out using geometric morphometric methods. The results of this study show that modern human populations can be distinguished based on facial shape alone, irrespective of age or sex, indicating the early presence of differences. Additionally, some populations have statistically distinct facial ontogenetic trajectories that lead to the development of further differences later in ontogeny. We conclude that population-specific facial morphologies develop principally through distinctions in facial shape probably already present at birth and further accentuated and modified to variable degrees during growth. These findings raise interesting questions regarding the plasticity of facial growth patterns in modern humans. Further, they have important implications in relation to the study of growth in the face of fossil hominins and in relation to the possibility of developing effective discriminant functions for the identification of population affinities of immature facial skeletal material. Such tools would be of value in archaeological, forensic and anthropological applications. The findings of this study underline the need to examine more deeply, and in more detail, the ontogenetic basis of other causes of craniometric variation, such as sexual dimorphism and hominin species differentiation.  (+info)

Cranio-cervical posture: a factor in the development and function of the dentofacial structures. (43/289)

Many practitioners will recognize that subjects with a large mandibular plane inclination are characterized by an extended head posture and a forward inclined cervical column, i.e. an extended cranio-cervical posture. It is also typical that subjects with a short-face morphology often carry their heads somewhat lowered, and have a markedly backward-curved upper cervical spine, i.e. cervical lordosis. The aim of the paper is to link together the findings of a series of studies that attempt to clarify this relationship, and bring into focus cranio-cervical posture, which is a functional factor that seems to be involved in many clinical orthodontic problems. To provide a background for the article, the concept of standardized posture of the head and the cervical column is developed, and procedures for recording this posture, as well as categories of cephalometric variables that express the different postural relationships, are described. Findings that relate cranio-cervical posture to upper airway obstruction, to craniofacial morphology, and to malocclusion are surveyed, and a post-natal developmental mechanism that explains the findings and leads to further questions is discussed. Recent findings of a relationship between extended cranio-cervical posture and signs and symptoms of temporomandibular disorders further emphasize the biological importance of this functional parameter.  (+info)

Craniofacial differences between Japanese and British Caucasian females with a skeletal Class III malocclusion. (44/289)

The racial differences in the craniofacial structures of 28 Japanese and 24 British Caucasian females with Class III malocclusions associated with a severe skeletal pattern were examined using lateral cephalograms. The mean age of the Japanese and Caucasian patients was 19.6 +/- 3.5 and 20.2 +/- 3.8 years (+/- SD), respectively. The mean values of 14 linear and 13 angular cephalometric parameters were compared between the two groups. The results showed that the Japanese females had a significantly reduced anterior cranial base (P < 0.01), a more retrusive midfacial component (P < 0.05), and a significantly increased lower anterior facial height (P < 0.01) associated with a more obtuse gonial angle (P < 0.05) compared with the Caucasians. Analysis of the dento-alveolar component in Japanese patients indicated more proclined upper incisors (P < 0.01) compared with those of Caucasian subjects. The reduced anterior cranial base and midfacial component, and the high-angle facial pattern in the Japanese population, may be morphological features based on race, and these skeletal features seem to be less favourable for a skeletal Class III growth pattern compared with the Caucasian population.  (+info)

The extraction of permanent second molars and its effect on the dentofacial complex of patients treated with the Tip-Edge appliance. (45/289)

The aim of this investigation was to assess the dentofacial changes in a group of patients consecutively treated with Tip-Edge appliances and the extraction of four permanent second molars by one specialist orthodontic practitioner. Before and after treatment lateral cephalograms and study cast measurements of 45 individuals, 26 females (mean age 13.8 years) and 19 males (mean age 13.9 years), were collated and statistically analysed. Cephalometric variables that exhibited, before treatment, significant sex differences, included SNA, SNB (both smaller in males, P < 0.05) and U1-NA degrees (P < 0.05), nasolabial angle (P < 0.05), and upper lip length P < 0.01 (all larger in males). After treatment, sex differences were demonstrated for SNA (smaller in males, P < 0.05), mandibular length (P < 0.01), upper face height (P < 0.05), lower face height (P < 0.01), anterior face height (P < 0.001), posterior face height (P < 0.01), nasolabial angle (P < 0.05), and upper lip length and thickness (P < 0.001; all larger in males). For the cast analysis, before treatment differences indicated larger values for males than females for lower arch inter-canine, premolar, and molar widths, arch depth (all P < 0.05), tooth size, and arch length (P < 0.01). Similar findings were noted in the upper arch except for inter-canine and premolar arch width. Despite most arch variables displaying sex differences, no gender effect was found for irregularity or crowding parameters. The same variables exhibited significant sex differences and changes after treatment (except tooth size, lower arch depth, and upper arch inter-canine width). Overall, the pattern of correction exhibited by the subjects included dental, skeletal, and soft tissue changes. Males tended to have greater mean increases in mandibular skeletal and soft tissue variables compared with females. Both males and females had increases in most dental arch variables measured from the study casts. Both sexes demonstrated a small uprighting, but statistically non-significant distalizing of the buccal segments. The lower incisors in the sagittal plane revealed a mean tendency to remain in their pre-treatment positions, with some individual variation. Overall, the treatment results were considered favourable, but case selection appeared to bias towards Angle Class I skeletal patterns of average to slightly reduced facial height, overbite and overjet < or = 4 mm, lip competence, no incisor protrusion, and moderate tooth size to arch length discrepancy (3-3.5 mm lower arch, 1 mm upper arch). Further evaluation of third molar eruption responses may provide insight into appropriate timing of second molar extractions.  (+info)

Sagittal occlusal relationships and asymmetry in prematurely born children. (46/289)

The aim of this investigation was to examine the effect of pre-term birth on sagittal occlusal relationships. The subjects were 328 prematurely born white and black children and 1804 control children who participated in the cross-sectional study of the Collaborative Perinatal Project (USA) in the early 1960s and 1970s. Dental examinations, including dental casts and photographs, were performed at the age of 6-12 years. The sagittal occlusion of the permanent molars and the canine relationship was recorded by examining and measuring the hard stone casts. The pre-term and comparison groups were divided by sex and race. A significantly greater prevalence of pre-normal canine relationships was found in the pre-term group than in the controls (P < 0.001). The incidence of a bilateral symmetrical canine relationship was 60.3 per cent in both the pre-term and control groups, but in the pre-term group the girls had better symmetry than the boys. Asymmetry occurred significantly more often on the left side (P < 0.001), especially in the control boys, but this was not so clear in the pre-term group. The prevalence of mesial molar occlusion was greater in the pre-term group. These results suggest that premature birth and the consequent exceptional adaptation from intra- to extra-uterine nutrition may influence dental occlusal development. This emphasizes the importance of early functional activity and differences in masticatory muscle activity and the largely unknown phenomenon of early catch-up growth. Individual differences in neonatal factors, in the need for intubation and other medical care are also of importance. Pre-term birth may also interfere with the development of symmetry and lateralization.  (+info)

The cellular and molecular origins of beak morphology. (47/289)

Cellular and molecular mechanisms underlying differences in beak morphology likely involve interactions among multiple embryonic populations. We exchanged neural crest cells destined to participate in beak morphogenesis between two anatomically distinct species. Quail neural crest cells produced quail beaks in duck hosts and duck neural crest produced duck bills in quail hosts. These transformations involved morphological changes to non-neural crest host beak tissues. To achieve these changes, donor neural crest cells executed autonomous molecular programs and regulated gene expression in adjacent host tissues. Thus, neural crest cells are a source of molecular information that generates interspecific variation in beak morphology.  (+info)

Targeted deletion of a branchial arch-specific enhancer reveals a role of dHAND in craniofacial development. (48/289)

The basic helix-loop-helix transcription factor dHAND is expressed in the mesenchyme of branchial arches and the developing heart. Mice homozygous for a dHAND (Hand2) null mutation die early in embryogenesis from cardiac abnormalities, precluding analysis of the potential role of dHAND in branchial arch development. Two independent enhancers control expression of dHAND in the heart and branchial arches. Endothelin-1 (ET-1) signaling regulates the branchial arch enhancer and is required for dHAND expression in the branchial arches. To determine the potential role of dHAND in branchial arch development and to assess the role of the ET-1-dependent enhancer in dHAND regulation in vivo, we deleted this enhancer by homologous recombination. Mice lacking the dHAND branchial arch enhancer died perinatally and exhibited a spectrum of craniofacial defects that included cleft palate, mandibular hypoplasia and cartilage malformations. Expression of dHAND was abolished in the ventolateral regions of the first and second branchial arches in these mutant mice, but expression was retained in a ventral domain where the related transcription factor eHAND is expressed. We conclude that dHAND plays an essential role in patterning and development of skeletal elements derived from the first and second branchial arches and that there are heterogeneous populations of cells in the branchial arches that rely on different cis-regulatory elements for activation of dHAND transcription.  (+info)