Three-dimensional mandibular dental changes with aging.

INTRODUCTION: This study aimed to evaluate the 3-dimensional (3D) mandibular dental changes over 42 years using the registration of digital models. METHODS: The sample comprised digital dental models of 8 untreated subjects (4 males and 4 females) with normal occlusion measured longitudinally at ages 17 years (T1) and 60 years (T2). Using 13 landmarks placed on the mucogingival junction, we registered the T2 model on the T1 model. Three-dimensional changes in the position of the landmarks on the buccal cusp tip of the posterior teeth and incisal edge of the central incisors were measured by 2 examiners. Registration and measurements were performed using SlicerCMF (version 3.1; http://www.slicer.org) software. Intra- and interrater agreements were evaluated using intraclass correlation coefficients and the Bland-Altman method. One-sample t tests were used for evaluating interphase 3D dental changes (P <0.05). RESULTS: Adequate intra- and interrater reproducibility was found. From T1 to T2, the mandibular teeth showed significant 3D positional changes. A significant dental eruption relative to the mucogingival junction was observed for the anterior and posterior teeth. Anteroposterior movements of mandibular teeth were not significant except for the right molar that drifted mesially. Transverse movements included slight lingual tipping at canines and premolars regions. CONCLUSIONS: Dental changes in untreated normal occlusion were very slight from early to mature adulthood. The eruption of the mandibular teeth was the most consistent finding. A tendency for mesial movement of molars and lingual movement of first premolars and canines was observed in the mandible during the aging process.

3D Mandibular Superimposition: Comparison of Regions of Reference for Voxel-Based Registration.

INTRODUCTION: The aim was to evaluate three regions of reference (Björk, Modified Björk and mandibular Body) for mandibular registration testing them in a patients' CBCT sample. METHODS: Mandibular 3D volumetric label maps were built from CBCTs taken before (T1) and after treatment (T2) in a sample of 16 growing subjects and labeled with eight landmarks. Registrations of T1 and T2 images relative to the different regions of reference were performed, and 3D surface models were generated. Seven mandibular dimensions were measured separately for each time-point (T1 and T2) in relation to a stable reference structure (lingual cortical of symphysis), and the T2-T1 differences were calculated. These differences were compared to differences measured between the superimposed T2 (generated from different regions of reference: Björk, Modified Björk and Mandibular Body) over T1 surface models. ICC and the Bland-Altman method tested the agreement of the changes obtained by nonsuperimposition measurements from the patients' sample, and changes between the overlapped surfaces after registration using the different regions of reference. RESULTS: The Björk region of reference (or mask) did work properly only in 2 of 16 patients. Evaluating the two other masks (Modified Björk and Mandibular body) on patients' scans registration, the concordance and agreement of the changes obtained from superimpositions (registered T2 over T1) compared to results obtained from non superimposed T1 and T2 separately, indicated that Mandibular Body mask displayed more consistent results. CONCLUSIONS: The mandibular body mask (mandible without teeth, alveolar bone, rami and condyles) is a reliable reference for 3D regional registration.

Common 3-dimensional coordinate system for assessment of directional changes.

INTRODUCTION: The aims of this study were to evaluate how head orientation interferes with the amounts of directional change in 3-dimensional (3D) space and to propose a method to obtain a common coordinate system using 3D surface models. METHODS: Three-dimensional volumetric label maps were built for pretreatment (T1) and posttreatment (T2) from cone-beam computed tomography images of 30 growing subjects. Seven landmarks were labeled in all T1 and T2 volumetric label maps. Registrations of T1 and T2 images relative to the cranial base were performed, and 3D surface models were generated. All T1 surface models were moved by orienting the Frankfort horizontal, midsagittal, and transporionic planes to match the axial, sagittal, and coronal planes, respectively, at a common coordinate system in the Slicer software (open-source, version 4.3.1; http://www.slicer.org). The matrix generated for each T1 model was applied to each corresponding registered T2 surface model, obtaining a common head orientation. The 3D differences between the T1 and registered T2 models, and the amounts of directional change in each plane of the 3D space, were quantified for before and after head orientation. Two assessments were performed: (1) at 1 time point (mandibular width and length), and (2) for longitudinal changes (maxillary and mandibular differences). The differences between measurements before and after head orientation were quantified. Statistical analysis was performed by evaluating the means and standard deviations with paired t tests (mandibular width and length) and Wilcoxon tests (longitudinal changes). For 16 subjects, 2 observers working independently performed the head orientations twice with a 1-week interval between them. Intraclass correlation coefficients and the Bland-Altman method tested intraobserver and interobserver agreements of the x, y, and z coordinates for 7 landmarks. RESULTS: The 3D differences were not affected by the head orientation. The amounts of directional change in each plane of 3D space at 1 time point were strongly influenced by head orientation. The longitudinal changes in each plane of 3D space showed differences smaller than 0.5 mm. Excellent intraobserver and interobserver repeatability and reproducibility (>99%) were observed. CONCLUSIONS: The amount of directional change in each plane of 3D space is strongly influenced by head orientation. The proposed method of head orientation to obtain a common 3D coordinate system is reproducible.

Are there bone dehiscences in maxillary canines orthodontically moved into the grafted alveolar cleft?

INTRODUCTION: The aim of this study was to assess the bone morphology of teeth mesialized into the grafted region in patients with unilateral alveolar cleft. METHODS: The sample comprised 30 patients with unilateral cleft lip and palate with a mean age of 20.5 years. High-resolution cone-beam computed tomography images of the maxilla were obtained 6 months to 2 years after comprehensive orthodontic treatment. The contralateral canines and lateral incisors were used as controls. Axial section was used to measure the bone thickness, and cross section was used to measure the alveolar crest height using the cementoenamel junction as a reference. Paired t tests and Wilcoxon tests were used to compare the cleft and noncleft sides (P <0.05). RESULTS: High individual variability was found. In general, the canines in the cleft side had statistically thinner buccal bone plates than the contralateral teeth. No differences between the cleft and noncleft sides were found for the lingual bone plate thickness. The canine on the cleft side showed a slightly greater distance between the lingual alveolar crest and the cementoenamel junction than the lateral incisor in the noncleft side. CONCLUSIONS: In patients with unilateral cleft lip and palate, mesial orthodontic movement of the maxillary canines into the grafted alveolar cleft results in acceptable buccal and lingual periodontal morphology.

Is the presence of Simonart's band in patients with complete unilateral cleft lip and palate associated with the prevalence of missing maxillary lateral incisors?

INTRODUCTION: The aim of this study was to compare the prevalence of agenesis of the maxillary lateral incisors in the cleft area of patients with unilateral cleft lip and palate with and without Simonart's band. METHODS: A sample of panoramic radiographs of 121 patients with a mean age of 7 years was divided into 2 groups: group 1 included 60 patients with Simonart's band, and group 2 included 61 patients without Simonart's band. Patients with syndromes were not included. Chi-square tests were used for intergroup comparisons (P <0.05). RESULTS: In the pooled subgroup, the prevalences of maxillary lateral incisor agenesis, supernumerary maxillary lateral incisors, 1 maxillary lateral incisor mesial to the cleft, and 1 maxillary lateral incisor distal to the cleft were 40.5%, 12.5%, 8.2%, and 38.8%, respectively. In group 1, these frequencies were 35%, 10%, 6.7%, and 48.3%; in group 2, they were 45.9%, 13.1%, 11.5%, and 29.5%. There was a statistically significant difference between the groups for the prevalence of a maxillary lateral incisor distal to the cleft. CONCLUSIONS: The presence of Simonart's band is associated with a higher frequency of maxillary lateral incisor development in the maxillary process.

Alveolar bone morphology in patients with bilateral complete cleft lip and palate in the mixed dentition: cone beam computed tomography evaluation.

OBJECTIVES: To verify the thickness and level of alveolar bone around the teeth adjacent to the cleft by means of cone beam computed tomography (CBCT) in patients with complete bilateral cleft lip and palate prior to bone graft surgery and orthodontic intervention. METHOD: The sample comprised 10 patients with complete bilateral cleft lip and palate (five boys and five girls) in the mixed dentition. The mean age was 9.5 years, and all subjects showed a G3 interarch relationship according to the Bauru index. The thickness of alveolar bone surrounding the maxillary incisors and the maxillary canines was measured in CBCT axial section using the software iCAT Xoran System. The distance between the alveolar bone crest and the cement-enamel junction (CEJ) was measured in cross sections. RESULTS: The tomography images showed a thin alveolar bone plate around teeth adjacent to clefts. No bone dehiscence was observed in teeth adjacent to clefts during the mixed dentition. A slight increase in the distance between the alveolar bone crest and the CEJ was observed in the mesial and lingual aspects of canines adjacent to cleft. CONCLUSION: In patients with BCLP in the mixed dentition, teeth adjacent to the alveolar cleft are covered by a thin alveolar bone plate. However, the level of alveolar bone crest around these teeth seems to be normal, and no bone dehiscence was identified at this age.

Morfologia alveolar sob a perspectiva da tomografia computadorizada: definindo os limites biológicos para a movimentação dentária / Alveolar bone morphology under the perspective of the computed tomography: Defining the biological limits of tooth movement

INTRODUÇÃO: a tomografia computadorizada (TC) permite a visualização do osso alveolar que recobre os dentes por vestibular e lingual. OBJETIVO: o propósito deste estudo foi expor e discutir as implicações da morfologia do osso alveolar, visualizado por meio da TC, sobre o diagnóstico e plano de tratamento ortodôntico. MÉTODOS: foram descritas as evidências sobre a inter-relação entre características dentofaciais e a morfologia das tábuas ósseas vestibular e lingual, assim como evidências sobre a repercussão da movimentação ortodôntica sobre o nível e espessura dessas estruturas periodontais. RESULTADOS: pacientes adultos podem apresentar deiscências ósseas previamente ao tratamento ortodôntico, principalmente na região dos incisivos inferiores. Os pacientes com padrão de crescimento vertical parecem apresentar menor espessura das tábuas ósseas vestibular e lingual no nível do ápice dos dentes permanentes, comparados a pacientes com padrão de crescimento horizontal. O movimento dentário vestibulolingual descentraliza os dentes do rebordo alveolar e ocasiona deiscências ósseas. CONCLUSÃO: a morfologia do rebordo alveolar constitui um fator limitante para a movimentação dentária e deve ser considerada, de forma individual, na realização do plano de tratamento ortodôntico.

INTRODUCTION: Computed tomography (CT) permits the visualization of the labial/buccal and lingual alveolar bone. OBJECTIVES: This study aimed at reporting and discussing the implications of alveolar bone morphology, visualized by means of CT, on the diagnosis and orthodontic treatment plan. METHODS: Evidences of the interrelationship between dentofacial features and labial/buccal and lingual alveolar bone morphology, as well as the evidences of the effects of the orthodontic movement on the thickness and level of these periodontal structures were described. RESULTS: Adult patients may present bone dehiscences previously to orthodontic treatment, mainly at the region of the mandibular incisors. Hyperdivergent patients seems to present a thinner thickness of the labial/buccal and lingual bone plates at the level of the root apex of permanent teeth, compared to hypodivergent patients. Buccolingual tooth movement might decentralize teeth from the alveolar bone causing bone dehiscences. CONCLUSION: The alveolar bone morphology constitutes a limiting factor for the orthodontic movement and should be individually considered in the orthodontic treatment planning.

Mordida aberta anterior dentoalveolar: diagnóstico morfológico e abordagens terapêuticas / Dentoalveolar anterior openbite: morphological diagnosis and therapeutic approaches

Este trabalho tem como objetivo demonstrar o diagnóstico da mordida aberta anterior dentoalveolar baseado na morfologia e suas modalidades de tratamento. Os fatores como as idades cronológica e dentária do paciente, disciplina familiar, dependência do hábito deletério quando presente, força da língua' como fator etiológico e, finalmente, o padrão de crescimento facial serão discutidos por meio de relatos clínicos, visando a definição de uma abordagem terapêutica individualizada.

The aim of this study is to demonstrate the diagnosis of dentoalveolar anterior openbite based on its morphology and therapeutic approaches. Factors like chronological and dental ages of the patient, familiar- discipline, dependence of deleterious oral habits, tongue force as the etiological factor and, finally, the facial growing pattern will be discussed through clinical reports with the aim of defining an individualized therapeutic approach.