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1.
PLoS One ; 14(12): e0221137, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31877131

RESUMO

The curved planes of the human dentition seen in the sagittal view, the mandibular curve of Spee and the maxillary compensating curve, have clinical importance to modern dentistry and potential relevance to the craniofacial evolution of hominins. However, the mechanism providing the formation of these curved planes is poorly understood. To explore this further, we use a simplified finite element model, consisting of maxillary and mandibular "blocks", developed to simulate tooth eruption, and forces opposing eruption, during simplified masticatory function. We test our hypothesis that curved occlusal planes develop from interplay between tooth eruption, occlusal load, and mandibular movement. Our results indicate that our simulation of rhythmic chewing movement, tooth eruption, and tooth eruption inhibition, applied concurrently, results in a transformation of the contacting maxillary and mandibular block surfaces from flat to curved. The depth of the curvature appears to be dependent on the radius length of the rotating (chewing) movement of the mandibular block. Our results suggest mandibular function and maxillo-mandibular spatial relationship may contribute to the development of human occlusal curvature.

2.
Am J Orthod Dentofacial Orthop ; 156(4): 522-530, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31582124

RESUMO

INTRODUCTION: Although unquantifiable features, such as faculty passion and dedication to teaching, play a vital role in defining the quality of residency education, determinable features that are fundamental to the definition of a "top tier" orthodontic residency program also exist. The objective of this study was to identify those features. METHODS: A survey with 32 items was developed and validated to assess the features of an excellent orthodontic program based on the following 3 major domains: faculty, education, and resident/graduate student/alumni. The survey was sent to 62 orthodontic residency programs in the United States. RESULTS: Thirty-nine programs (63%) completed the survey. Recurring attributes that were identified in what constitutes an excellent program included the following: an adequate number of full-time clinical orthodontic faculty, with each member providing 1 day per week clinic coverage. The average of all respondents was 4, and the range was 1-6; a healthy mix of part-time faculty members with ≥1 full-time faculty member who monitors every clinical session; 80% full-time faculty members who are American Board of Orthodontics (ABO) certified; a craniofacial faculty member; 4 residents/graduate students per each faculty member who covers a clinical session; resident/graduate student exposure to a wide range of treatment modalities and appliances; approximately 70 new case starts per resident/graduate student (50%-60% of patients who are started are debonded by the starting resident/graduate student); patients with craniofacial anomalies and orthognathic surgery patients should be started by each resident/graduate student; 1.5 operatory chairs per resident or graduate student; 1 dental assistant per 4 residents/graduate students; 1 laboratory person; 1 receptionist/secretary per 4 residents; 100% of residents/graduate students successfully completing ABO written examination upon graduation; 60% of residents/graduate students obtaining ABO certification within 5 years of graduation; 50% of residents/graduate students presenting at national meetings would be ideal; and 50% of living alumni contributing financially to the department during the past 5 years. CONCLUSIONS: Based on the responses from the majority of the US orthodontic residency programs, this study has identified certain features that educators feel are ideal for an excellent orthodontic program.


Assuntos
Educação de Pós-Graduação em Odontologia/normas , Internato e Residência/normas , Ortodontia/educação , Ortodontia/normas , Docentes de Odontologia/educação , Docentes de Odontologia/normas , Humanos , Avaliação de Programas e Projetos de Saúde , Inquéritos e Questionários , Estados Unidos
3.
Angle Orthod ; 88(5): 530-537, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29667470

RESUMO

OBJECTIVES: The long-term skeletal effects of Class II treatment in growing individuals using high-pull facebow headgear and fixed edgewise appliances have not been reported. The purpose of this study was to evaluate the long-term skeletal effects of treatment using high-pull headgear followed by fixed orthodontic appliances compared to an untreated control group. MATERIALS AND METHODS: Changes in anteroposterior and vertical cephalometric measurements of 42 Class II subjects (n = 21, mean age = 10.7 years) before treatment, after headgear correction to Class I molar relationship, after treatment with fixed appliances, and after long-term retention (mean 4.1 years), were compared to similar changes in a matched control group (n = 21, mean age = 10.9 years) by multivariable linear regression models. RESULTS: Compared to control, the study group displayed significant long-term horizontal restriction of A-point (SNA = -1.925°, P < .0001; FH-NA = -3.042°, P < .0001; linear measurement A-point to Vertical Reference = -3.859 mm, P < .0001) and reduction of the ANB angle (-1.767°, P < .0001), with no effect on mandibular horizontal growth or maxillary and mandibular vertical skeletal changes. A-point horizontal restriction and forward mandibular horizontal growth accompanied the study group correction to Class I molar, and these changes were stable long term. CONCLUSIONS: One phase treatment for Class II malocclusion with high-pull headgear followed by fixed orthodontic appliances resulted in correction to Class I molar through restriction of horizontal maxillary growth with continued horizontal mandibular growth and vertical skeletal changes unaffected. The anteroposterior molar correction and skeletal effects of this treatment were stable long term.


Assuntos
Aparelhos de Tração Extrabucal , Má Oclusão de Angle Classe II/terapia , Aparelhos Ortodônticos Fixos , Ortodontia Corretiva/métodos , Estudos de Casos e Controles , Cefalometria , Criança , Humanos , Masculino , Má Oclusão de Angle Classe II/patologia , Ortodontia Corretiva/instrumentação
4.
Am J Orthod Dentofacial Orthop ; 151(3): 539-558, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28257739

RESUMO

INTRODUCTION: Genetic studies of malocclusion etiology have identified 4 deleterious mutations in genes DUSP6,ARHGAP21, FGF23, and ADAMTS1 in familial Class III cases. Although these variants may have large impacts on Class III phenotypic expression, their low frequency (<1%) makes them unlikely to explain most malocclusions. Thus, much of the genetic variation underlying the dentofacial phenotypic variation associated with malocclusion remains unknown. In this study, we evaluated associations between common genetic variations in craniofacial candidate genes and 3-dimensional dentoalveolar phenotypes in patients with malocclusion. METHODS: Pretreatment dental casts or cone-beam computed tomographic images from 300 healthy subjects were digitized with 48 landmarks. The 3-dimensional coordinate data were submitted to a geometric morphometric approach along with principal component analysis to generate continuous phenotypes including symmetric and asymmetric components of dentoalveolar shape variation, fluctuating asymmetry, and size. The subjects were genotyped for 222 single-nucleotide polymorphisms in 82 genes/loci, and phenotpye-genotype associations were tested via multivariate linear regression. RESULTS: Principal component analysis of symmetric variation identified 4 components that explained 68% of the total variance and depicted anteroposterior, vertical, and transverse dentoalveolar discrepancies. Suggestive associations (P < 0.05) were identified with PITX2, SNAI3, 11q22.2-q22.3, 4p16.1, ISL1, and FGF8. Principal component analysis for asymmetric variations identified 4 components that explained 51% of the total variations and captured left-to-right discrepancies resulting in midline deviations, unilateral crossbites, and ectopic eruptions. Suggestive associations were found with TBX1AJUBA, SNAI3SATB2, TP63, and 1p22.1. Fluctuating asymmetry was associated with BMP3 and LATS1. Associations for SATB2 and BMP3 with asymmetric variations remained significant after the Bonferroni correction (P <0.00022). Suggestive associations were found for centroid size, a proxy for dentoalveolar size variation with 4p16.1 and SNAI1. CONCLUSIONS: Specific genetic pathways associated with 3-dimensional dentoalveolar phenotypic variation in malocclusions were identified.


Assuntos
Má Oclusão/genética , Adolescente , Adulto , Idoso , Pontos de Referência Anatômicos , Criança , Tomografia Computadorizada de Feixe Cônico , Feminino , Estudos de Associação Genética , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Fenótipo , Análise de Componente Principal , Reprodutibilidade dos Testes
5.
Am J Phys Anthropol ; 161(2): 226-36, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27346254

RESUMO

OBJECTIVES: The curve of Spee (COS) is a mesio-distally curved alignment of the canine through distal molar cusp tips in certain mammals including modern humans and some fossil hominins. In humans, the alignment varies from concave to flat, and previous studies have suggested that this difference reflects craniofacial morphology, including the degree of alveolar prognathism. However, the relationship between prognathism and concavity of the COS has not been tested in craniofacially variant populations. We tested the hypothesis that greater alveolar prognathism covaries with a flatter COS in African-American and European-American populations. We further examined this relationship in fossil Homo including Homo neanderthalensis and early anatomically modern Homo sapiens, which are expected to extend the amount of variation in the COS from the extant sample. METHODS AND MATERIALS: These hypotheses were tested using three-dimensional geometric morphometrics. Landmarks were recorded from the skulls of 166 African-Americans, 123 European-Americans, and 10 fossil hominin mandible casts. Landmarks were subjected to generalized Procrustes analysis, principal components analysis, and two-block partial least squares analysis. RESULTS: We documented covariation between the COS and alveolar prognathism such that relatively prognathic individuals have a flatter COS. Mandibular data from the fossil hominin taxa generally confirm and extend this correlation across a greater range of facial size and morphology in Homo. DISCUSSION: Our results suggest that the magnitude of the COS is related to a suite of features associated with alveolar prognathism in modern humans and across anthropoids. We also discuss the implications for spatial interactions between the dental arches.


Assuntos
Dente Canino/anatomia & histologia , Hominidae/anatomia & histologia , Mandíbula/anatomia & histologia , Homem de Neandertal/anatomia & histologia , Animais , Antropologia Física , Evolução Biológica , Fósseis , Humanos
6.
Am J Hum Biol ; 28(6): 879-889, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27292446

RESUMO

OBJECTIVES: In humans, there is a large range of variation in the form of the maxillary and mandibular dental arches. This variation can manifest as either prognathism or retrognathism in either or both arches, which can cause malocclusion and lead to abnormal masticatory function. This study aims to identify aspects of variation and morphological integration existing in the dental arches of individuals with different types of malocclusion. METHODS: Coordinate landmark data were collected along the gingival margins of 397 scanned dental casts and then analyzed using geometric morphometric techniques to explore arch form variation and patterns of morphological integration within each malocclusion type. RESULTS: Significant differences were identified between Class II forms (increased projection of upper arch relative to the lower arch) and Class III forms (lower arch projection beyond the upper arch) in symmetrical shape variation, including anteroposterior arch discrepancies and abnormal anterior arch divergence or convergence. Partial least squares analysis demonstrated that Class III dental arches have higher levels of covariance between upper and lower arches (RV = 0.91) compared to the dental arches of Class II (RV = 0.78) and Class I (RV = 0.73). These high levels of covariance, however, are on the lower end of the overall range of possible masticatory blocks, indicating weaker than expected levels of integration. CONCLUSIONS: This study provides evidence for patterns of variation in dental arch shape found in individuals with Class II and Class III malocclusions. Moreover, differences in integration found between malocclusion types have ramifications for how such conditions should be studied and treated. Am. J. Hum. Biol. 28:879-889, 2016. © 2016Wiley Periodicals, Inc.


Assuntos
Arco Dental/anatomia & histologia , Má Oclusão/patologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Arco Dental/patologia , Feminino , Humanos , Iowa , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Adulto Jovem
7.
Am J Orthod Dentofacial Orthop ; 149(6): 781-2, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27241984
8.
Am J Orthod Dentofacial Orthop ; 148(5): 748-54, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26522034

RESUMO

INTRODUCTION: The National Matching Service provides an ethical and unbiased selection process between residency programs and candidates. Currently, 51 of the 66 accredited orthodontic residency programs in the United States participate in the matching service for orthodontic programs (the Match), and 15 do not. Our purpose was to identify the factors that contribute to an orthodontic residency program's decision to participate in the Match program or to refrain from doing so. METHODS: A survey was sent to 64 orthodontic programs regarding their perception of the Match. A qualitative content analysis of the survey responses was conducted. Common recurring themes were identified. Simple descriptive statistics were used to summarize the data. RESULTS: Fifty-six programs responded to the survey. Survey content analysis showed 2 prevailing themes: orthodontic programs participate in the Match because they believe it is a fair process, or they refrain from participating so that they can pressure selected candidates to accept positions early. CONCLUSIONS: Participation in the Match benefits candidates, schools, and orthodontic education in general. Candidates can interview at multiple schools and rank their choices without the pressure of early acceptance. Orthodontic programs are forced to compete for strong candidates; this ultimately strengthens the education their residents receive. The Match can accommodate complex requirements of different programs, including allowing them to recruit a certain mix or a diversity of students. We concluded that all orthodontic residency programs in the United States should participate in the Match.


Assuntos
Internato e Residência , Ortodontia/educação , Seleção de Pessoal , Atitude do Pessoal de Saúde , Grupos Focais , Humanos , Pesquisa Qualitativa , Critérios de Admissão Escolar , Faculdades de Odontologia , Estados Unidos
9.
Arch Oral Biol ; 60(6): 933-40, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25841069

RESUMO

OBJECTIVES: A thorough understanding of influence of maxillary growth on patterns of mandibular rotation during development is important with regard to the treatment of skeletal discrepancies. In the present study, we examined whether experimentally altered maxillary position has a significant influence on patterns of mandibular rotation in a pig model. DESIGN: Maxillary growth was altered in a sample of n=10 domestic pigs via surgical fixation of the circummaxillary sutures. We compared the experimental group to control and surgical sham samples and assessed the effects of altered maxillary growth on mandibular form using geometric morphometric techniques. We tested for significant differences in mandibular shape between our samples and examined axes of morphological variation. Additionally, we examined whether altered mandibular shape resulting from altered maxillary position was predictably associated with morphological changes to the condylar region. RESULTS: There was a statistically significant difference in mandibular shape between the experimental and control/sham groups. As a result of vertical displacement of the snout, mandibles in the experimental sample resulted in greater anterior rotation when compared to the control/sham pigs. Variation in rotation was correlated with morphological changes in the condyle including the shape of the articular surface and condylar orientation indicative of greater anterior mandibular rotation. CONCLUSIONS: Vertical displacement of the maxilla had a significant effect on mandibular shape by encouraging anterior mandibular rotation. This result has important implications for understanding the effects of altered mandibular posture on condylar remodeling the treatment of skeletal discrepancies such as the correction of hyperdivegent mandibular growth.


Assuntos
Mandíbula/crescimento & desenvolvimento , Maxila/cirurgia , Pontos de Referência Anatômicos , Animais , Modelos Animais de Doenças , Feminino , Mandíbula/anatomia & histologia , Côndilo Mandibular/anatomia & histologia , Côndilo Mandibular/crescimento & desenvolvimento , Rotação , Suínos
10.
Am J Orthod Dentofacial Orthop ; 145(3): 305-16, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24582022

RESUMO

INTRODUCTION: Class II malocclusion affects about 15% of the population in the United States and is characterized by a convex profile and occlusal disharmonies. The specific etiologic mechanisms resulting in the range of Class II dentoskeletal combinations observed are not yet understood. Most studies describing Class II phenotypic diversity have used moderate sample sizes or focused on younger patients who later in life might outgrow their Class II discrepancies; such a focus might also preclude the visualization of adult Class II features. The majority have used simple correlation methods resulting in phenotypes that might not be generalizable to different samples and thus might not be suitable for studies of malocclusion etiology. The purpose of this study was to address these knowledge gaps by capturing the maximum phenotypic variations in a large sample of white Class II subjects selected with strict eligibility criteria and rigorously standardized multivariate reduction analyses. METHODS: Sixty-three lateral cephalometric variables were measured from the pretreatment records of 309 white Class II adults (82 male, 227 female; ages, 16-60 years). Principal component analysis and cluster analysis were used to generate comprehensive phenotypes to identify the most homogeneous groups of subjects, reducing heterogeneity and improving the power of future malocclusion etiology studies. RESULTS: Principal component analysis resulted in 7 principal components that accounted for 81% of the variation. The first 3 components represented variation on mandibular rotation, maxillary incisor angulation, and mandibular length. The cluster analysis identified 5 distinct Class II phenotypes. CONCLUSIONS: A comprehensive spectrum of Class II phenotypic definitions was obtained that can be generalized to other samples to advance our efforts for identifying the etiologic factors underlying Class II malocclusion.


Assuntos
Má Oclusão de Angle Classe II/patologia , Fenótipo , Adolescente , Adulto , Cefalometria/métodos , Análise por Conglomerados , Grupo com Ancestrais do Continente Europeu , Feminino , Variação Genética/genética , Humanos , Processamento de Imagem Assistida por Computador/métodos , Incisivo/patologia , Masculino , Má Oclusão de Angle Classe II/genética , Mandíbula/patologia , Maxila/patologia , Pessoa de Meia-Idade , Análise de Componente Principal , Rotação , Adulto Jovem
11.
Am J Phys Anthropol ; 153(3): 387-96, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24264260

RESUMO

Variation in recent human mandibular form is often thought to reflect differences in masticatory behavior associated with variation in food preparation and subsistence strategies. Nevertheless, while mandibular variation in some human comparisons appear to reflect differences in functional loading, other comparisons indicate that this relationship is not universal. This suggests that morphological variation in the mandible is influenced by other factors that may obscure the effects of loading on mandibular form. It is likely that highly strained mandibular regions, including the corpus, are influenced by well-established patterns of lower facial skeletal integration. As such, it is unclear to what degree mandibular form reflects localized stresses incurred during mastication vs. a larger set of correlated features that may influence bone distribution patterns. In this study, we examine the relationship between mandibular symphyseal bone distribution (i.e., second moments of area, cortical bone area) and masticatory force production (i.e., in vivo maximal bite force magnitude and estimated symphyseal bending forces) along with lower facial shape variation in a sample of n = 20 living human male subjects. Our results indicate that while some aspects of symphyseal form (e.g., wishboning resistance) are significantly correlated with estimates of symphyseal bending force magnitude, others (i.e., vertical bending resistance) are more closely tied to variation in lower facial shape. This suggests that while the symphysis reflects variation in some variables related to functional loading, the complex and multifactorial influences on symphyseal form underscores the importance of exercising caution when inferring function from the mandible especially in narrow taxonomic comparisons.


Assuntos
Fenômenos Biomecânicos/fisiologia , Mandíbula/anatomia & histologia , Mandíbula/fisiologia , Adolescente , Adulto , Pontos de Referência Anatômicos , Antropologia Física , Humanos , Masculino , Mandíbula/diagnóstico por imagem , Mastigação/fisiologia , Tomografia Computadorizada por Raios X , Adulto Jovem
12.
Am J Phys Anthropol ; 153(1): 52-60, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24318941

RESUMO

Researchers have hypothesized that nasal morphology, both in archaic Homo and in recent humans, is influenced by body mass and associated oxygen consumption demands required for tissue maintenance. Similarly, recent studies of the adult human nasal region have documented key differences in nasal form between males and females that are potentially linked to sexual dimorphism in body size, composition, and energetics. To better understand this potential developmental and functional dynamic, we first assessed sexual dimorphism in the nasal cavity in recent humans to determine when during ontogeny male-female differences in nasal cavity size appear. Next, we assessed whether there are significant differences in nasal/body size scaling relationships in males and females during ontogeny. Using a mixed longitudinal sample we collected cephalometric and anthropometric measurements from n = 20 males and n = 18 females from 3.0 to 20.0+ years of age totaling n = 290 observations. We found that males and females exhibit similar nasal size values early in ontogeny and that sexual dimorphism in nasal size appears during adolescence. Moreover, when scaled to body size, males exhibit greater positive allometry in nasal size compared to females. This differs from patterns of sexual dimorphism in overall facial size, which are already present in our earliest age groups. Sexually dimorphic differences in nasal development and scaling mirror patterns of ontogenetic variation in variables associated with oxygen consumption and tissue maintenance. This underscores the importance of considering broader systemic factors in craniofacial development and may have important implications for the study of patters craniofacial evolution in the genus Homo.


Assuntos
Evolução Biológica , Face/fisiologia , Nariz/anatomia & histologia , Adolescente , Adulto , Análise de Variância , Antropologia Física , Antropometria , Tamanho Corporal , Criança , Pré-Escolar , Face/anatomia & histologia , Feminino , Humanos , Lactente , Masculino , Caracteres Sexuais , Adulto Jovem
13.
Am J Orthod Dentofacial Orthop ; 144(1): 32-42, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23810043

RESUMO

INTRODUCTION: Class III malocclusion is characterized by a composite of dentoskeletal patterns that lead to the forward positioning of the mandibular teeth in relation to the maxillary teeth and a concave profile. Environmental and genetic factors are associated with this condition, which affects 1% of the population in the United States and imposes significant esthetic and functional burdens on affected persons. The purpose of this study was to capture the phenotypic variation in a large sample of white adults with Class III malocclusion using multivariate reduction methods. METHODS: Sixty-three lateral cephalometric variables were measured from the pretreatment records of 292 white subjects with Class II malocclusion (126 male, 166 female; ages, 16-57 years). Principal component analysis and cluster analysis were used to capture the phenotypic variation and identify the most homogeneous groups of subjects to reduce genetic heterogeneity. RESULTS: Principal component analysis resulted in 6 principal components that accounted for 81.2% of the variation. The first 3 components represented variation in mandibular horizontal and vertical positions, maxillary horizontal position, and mandibular incisor angulation. The cluster model identified 5 distinct subphenotypes of Class III malocclusion. CONCLUSIONS: A spectrum of phenotypic definitions was obtained replicating results of previous studies and supporting the validity of these phenotypic measures in future research of the genetic and environmental etiologies of Class III malocclusion.


Assuntos
Má Oclusão de Angle Classe III/patologia , Fenótipo , Adolescente , Adulto , Cefalometria/métodos , Queixo/patologia , Análise por Conglomerados , Grupo com Ancestrais do Continente Europeu , Feminino , Variação Genética/genética , Humanos , Incisivo/patologia , Masculino , Mandíbula/patologia , Maxila/patologia , Pessoa de Meia-Idade , Osso Nasal/patologia , Análise de Componente Principal , Radiografia Dentária Digital , Sela Túrcica/patologia , Dimensão Vertical , Filme para Raios X , Adulto Jovem
14.
Am J Orthod Dentofacial Orthop ; 140(3): e93-8, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21889062

RESUMO

INTRODUCTION: The primary stability of orthodontic anchorage miniscrews is believed to result from mechanical interlock, with success based upon a number of variables, including screw diameter, angle of placement, monocortical vs bicortical placement, placement through attached or unattached soft tissue, presence or absence of a pilot hole, periscrew inflammation, and maximum placement torque. The purpose of this ex-vivo study was to further explore the relationship between maximum placement torque during miniscrew placement and miniscrew resistance to movement under load. METHODS: Ninety-six titanium screws were placed into 24 hemi-maxillae and 24 hemi-mandibles from cadavers between the first and second premolars by using a digital torque screwdriver. All screws were subjected to a force parallel to the occlusal plane, pulling mesially until the miniscrews were displaced by 0.6 mm. The Spearman rank correlation test was used to evaluate whether there was an increasing or a decreasing relationship between maximum placement torque of the screws, miniscrew resistance to movement, and bone thickness. A paired-sample t test and the nonparametric Wilcoxon signed rank test were used to compare maximum placement torque, bone thickness, and miniscrew resistance to movement between coronally positioned and apically positioned screws in the maxilla and the mandible, and between screws placed in the maxilla vs screws placed in the mandible. Additionally, 1-way analysis of variance (ANOVA) with the post-hoc Tukey-Kramer test was used to determine whether there was a significant difference in miniscrew resistance to movement for screws placed with maximum torque of <5 Ncm, 5 to 10 Ncm, and >10 Ncm. RESULTS: The mean difference in miniscrew resistance to movement between maximum placement torque groupings, <5 Ncm, 5 to 10 Ncm, and >10 Ncm, increased throughout the deflection range of 0.0 to 0.6 mm. As deflection increased to 0.12 to 0.33 mm, the mean resistance to movement for miniscrews with maximum placement torque of 5 to 10 Ncm was statistically greater than for screws with maximum placement torque <5 Ncm (P <0.05). As deflection increased to 0.34 to 0.60 mm, the mean resistance to movement for miniscrews with maximum placement torque of 5 to 10 Ncm and >10 Ncm was significantly greater than for screws with maximum placement torque <5 Ncm (P <0.05). At no deflection was there a significant difference in resistance to movement between the 2 miniscrew groups with higher placement torque values of 5 to 10 Ncm and >10 Ncm. CONCLUSIONS: Ex vivo, the mean resistance to movement of miniscrews with higher maximum placement torque was greater than the resistance to movement of those with lower maximum placement torque.


Assuntos
Análise do Estresse Dentário , Procedimentos de Ancoragem Ortodôntica/instrumentação , Processo Alveolar/cirurgia , Análise de Variância , Fenômenos Biomecânicos , Parafusos Ósseos , Cadáver , Humanos , Miniaturização , Movimento , Estatísticas não Paramétricas , Torque
15.
Am J Orthod Dentofacial Orthop ; 140(2): 182-8, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21803255

RESUMO

INTRODUCTION: The cervical vertebrae maturation (CVM) method has been advocated as a predictor of peak mandibular growth. A careful review of the literature showed potential methodologic errors that might influence the high reported reproducibility of the CVM method, and we recently established that the reproducibility of the CVM method was poor when these potential errors were eliminated. The purpose of this study was to further investigate the reproducibility of the individual vertebral patterns. In other words, the purpose was to determine which of the individual CVM vertebral patterns could be classified reliably and which could not. METHODS: Ten practicing orthodontists, trained in the CVM method, evaluated the morphology of cervical vertebrae C2 through C4 from 30 cephalometric radiographs using questions based on the CVM method. The Fleiss kappa statistic was used to assess interobserver agreement when evaluating each cervical vertebrae morphology question for each subject. The Kendall coefficient of concordance was used to assess the level of interobserver agreement when determining a "derived CVM stage" for each subject. RESULTS: Interobserver agreement was high for assessment of the lower borders of C2, C3, and C4 that were either flat or curved in the CVM method, but interobserver agreement was low for assessment of the vertebral bodies of C3 and C4 when they were either trapezoidal, rectangular horizontal, square, or rectangular vertical; this led to the overall poor reproducibility of the CVM method. These findings were reflected in the Fleiss kappa statistic. Furthermore, nearly 30% of the time, individual morphologic criteria could not be combined to generate a final CVM stage because of incompatible responses to the 5 questions. Intraobserver agreement in this study was only 62%, on average, when the inconclusive stagings were excluded as disagreements. Intraobserver agreement was worse (44%) when the inconclusive stagings were included as disagreements. For the group of subjects that could be assigned a CVM stage, the level of interobserver agreement as measured by the Kendall coefficient of concordance was only 0.45, indicating moderate agreement. CONCLUSIONS: The weakness of the CVM method results, in part, from difficulty in classifying the vertebral bodies of C3 and C4 as trapezoidal, rectangular horizontal, square, or rectangular vertical. This led to the overall poor reproducibility of the CVM method and our inability to support its use as a strict clinical guideline for the timing of orthodontic treatment.


Assuntos
Determinação da Idade pelo Esqueleto/métodos , Vértebras Cervicais/anatomia & histologia , Vértebras Cervicais/crescimento & desenvolvimento , Adolescente , Desenvolvimento Ósseo , Cefalometria , Vértebras Cervicais/diagnóstico por imagem , Criança , Feminino , Humanos , Masculino , Variações Dependentes do Observador , Reprodutibilidade dos Testes
16.
Am J Orthod Dentofacial Orthop ; 139(4): 456-64, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21457856

RESUMO

INTRODUCTION: During facial growth, the maxilla and mandible translate downward and forward. Although the forward displacement of the maxilla is less than that of the mandible, the interarch relationship of the teeth in the sagittal view during growth remains essentially unchanged. Interdigitation is thought to provide a compensatory (tooth movement) mechanism for maintaining the pattern of occlusion during growth: the maxillary teeth move anteriorly relative to the maxilla while the mandibular teeth move posteriorly relative to the basilar mandible. The purpose of this study was to investigate the hypothesis that the human chin develops as a result of this process. METHODS: Twenty-five untreated subjects from the Iowa Facial Growth Study with Class I normal occlusion were randomly selected based on availability of cephalograms at T1 (mean = 8.32 yr) and T2 (mean = 19.90 yr). Measurements of growth (T2 minus T1) parallel to the Frankfort horizontal (FH) for the maxilla, maxillary dentition, mandible, mandibular dentition, and pogonion (Pg) were made. RESULTS: Relative to Pg (a stable bony landmark), B-point moved posteriorly, on average 2.34 mm during growth, and bony chin development (B-point to Pg) increased concomitantly. Similarly, the mandibular and maxillary incisors moved posteriorly relative to Pg 2.53 mm and 2.76 mm, respectively. A-point, relative to Pg, moved posteriorly 4.47 mm during growth. CONCLUSIONS: Bony chin development during facial growth occurs, in part, from differential jaw growth and compensatory dentoalveolar movements.


Assuntos
Queixo/crescimento & desenvolvimento , Mandíbula/crescimento & desenvolvimento , Maxila/crescimento & desenvolvimento , Processo Alveolar/crescimento & desenvolvimento , Cefalometria , Criança , Arco Dental/crescimento & desenvolvimento , Oclusão Dentária , Dentição , Feminino , Seguimentos , Humanos , Incisivo/anatomia & histologia , Masculino , Mandíbula/anatomia & histologia , Côndilo Mandibular/anatomia & histologia , Maxila/anatomia & histologia , Dente Molar/anatomia & histologia , Osso Nasal/anatomia & histologia
17.
Am J Orthod Dentofacial Orthop ; 139(2): e147-52, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21300225

RESUMO

INTRODUCTION: Even though the use of titanium miniscrews to provide orthodontic anchorage has become increasingly popular, there is no universally accepted screw-placement protocol. Variables include the presence or absence of a pilot hole, placement through attached or unattached soft tissue, and angle of placement. The purpose of this in-vitro study was to test the hypothesis that screw angulation affects screw-anchorage resistance. METHODS: Three-dimensional finite element models were created to represent screw-placement orientations of 30°, 60°, and 90°, while the screw was displaced to 0.6 mm at a distance of 2.0 mm from the bone surface. In a parallel cadaver study, 96 titanium alloy screws were placed into 24 hemi-sected maxillary and 24 hemi-sected mandibular specimens between the first and second premolars. The specimens were randomly and evenly divided into 3 groups according to screw angulation (relative to the bone surface): 90° vs 30° screw pairs, 90° vs 60° screw pairs, and 30° vs 60° screw pairs. All screws were subjected to increasing forces parallel to the occlusal plane, pulling mesially until the miniscrews were displaced by 0.6 mm. A paired-samples t test was used to assess the significance of differences between 2 samples consisting of matched pairs of subjects, with matched pairs of subjects including 2 measurements taken on the same subject. One-way analysis of variance (ANOVA) with the post-hoc Tukey studentized range test was conducted to determine whether there were significant differences, and the order of those differences, in anchorage resistance values among the 3 screw angulations at maxillary and mandibular sites. RESULTS: The finite element analysis showed that 90° screw placement provided greater anchorage resistance than 60° and 30° placements. In the cadaver study, although the maximum anchorage resistance provided by screws placed at 90° to the cadaver bone surface exceeded, on average, the anchorage resistance of the screws placed at 60°, which likewise exceeded the anchorage resistance of screws placed at 30°, these differences were not statistically significant. CONCLUSIONS: Placing orthodontic miniscrews at angles less than 90° to the alveolar process bone surface does not offer force anchorage resistance advantages.


Assuntos
Parafusos Ósseos , Implantação Dentária Endo-Óssea/métodos , Análise do Estresse Dentário , Procedimentos de Ancoragem Ortodôntica/instrumentação , Análise de Variância , Cadáver , Análise do Estresse Dentário/métodos , Módulo de Elasticidade , Análise de Elementos Finitos , Humanos , Mandíbula/cirurgia , Maxila/cirurgia , Miniaturização , Estatísticas não Paramétricas
18.
Am J Orthod Dentofacial Orthop ; 139(2): 228-34, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21300252

RESUMO

INTRODUCTION: Headgears have been used to treat Class II malocclusions for over a century. The purpose of this retrospective study was to investigate the profile esthetic changes resulting from headgear use in growing Class II patients with protrusive, normal, and retrusive maxillae. METHODS: Profile silhouettes were created from pretreatment and posttreatment lateral cephalometric tracings of growing Class II patients treated with headgear followed by conventional fixed appliances. Ten patients had an initially protrusive maxilla (FH:NA, >92°), 10 had an initially normally positioned maxilla (FH:NA, 88°-92°), and 10 had an initially retrusive maxilla (FH:NA, <88°). A panel of 20 laypersons judged the profile esthetics of the randomly sorted silhouettes. Descriptive statistics, correlation analysis, and anlaysis of variance (ANOVA) with post-hoc Tukey-Kramer tests were used to ascertain differences between groups and the effects of treatment. RESULTS: A significant moderate correlation was found between initial ANB magnitude and the improvement in profile esthetic score with treatment (r = 0.49, P <0.01). No significant correlations were found between the initial anteroposterior position of the maxilla (FH:NA) and the initial, final, or change in profile esthetic scores. There were average improvements with headgear treatment in profile esthetics for all groups. CONCLUSIONS: In Class II growing patients with protrusive, normally positioned, or retrusive maxillae, headgear treatment used with fixed orthodontic appliances is effective in improving facial profile esthetics: the greater the initial ANB angle, the greater the profile esthetic improvement with treatment.


Assuntos
Estética Dentária , Aparelhos de Tração Extrabucal , Má Oclusão de Angle Classe II/terapia , Maxila/patologia , Análise de Variância , Cefalometria/estatística & dados numéricos , Criança , Face/anatomia & histologia , Humanos , Desenvolvimento Maxilofacial , Prognatismo , Retrognatismo , Estudos Retrospectivos , Estatísticas não Paramétricas , Resultado do Tratamento
19.
Anat Rec (Hoboken) ; 294(1): 68-78, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21157917

RESUMO

The influence of the chondrocranium in craniofacial development and its role in the reduction of facial size and projection in the genus Homo is incompletely understood. As one component of the chondrocranium, the nasal septum has been argued to play a significant role in human midfacial growth, particularly with respect to its interaction with the premaxilla during prenatal and early postnatal development. Thus, understanding the precise role of nasal septal growth on the facial skeleton is potentially informative with respect to the evolutionary change in craniofacial form. In this study, we assessed the integrative effects of the nasal septum and premaxilla by experimentally reducing facial length in Sus scrofa via circummaxillary suture fixation. Following from the nasal septal-traction model, we tested the following hypotheses: (1) facial growth restriction produces no change in nasal septum length; and (2) restriction of facial length produces compensatory premaxillary growth due to continued nasal septal growth. With respect to hypothesis 1, we found no significant differences in septum length (using the vomer as a proxy) in our experimental (n = 10), control (n = 9) and surgical sham (n = 9) trial groups. With respect to hypothesis 2, the experimental group exhibited a significant increase in premaxilla length. Our hypotheses were further supported by multivariate geometric morphometric analysis and support an integrative relationship between the nasal septum and premaxilla. Thus, continued assessment of the growth and integration of the nasal septum and premaxilla is potentially informative regarding the complex developmental mechanisms that underlie facial reduction in genus Homo evolution.


Assuntos
Evolução Biológica , Ossos Faciais/crescimento & desenvolvimento , Hominidae/crescimento & desenvolvimento , Desenvolvimento Maxilofacial/fisiologia , Septo Nasal/crescimento & desenvolvimento , Animais , Ossos Faciais/anatomia & histologia , Feminino , Hominidae/anatomia & histologia , Humanos , Septo Nasal/anatomia & histologia , Sus scrofa
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