Three-dimensional analysis of mandibular landmarks, planes and shape, and the symphyseal changes associated with growth and orthodontic treatment

OBJECTIVE: To test reliability of 3D mandibular landmarks, planes of reference and surfaces and assess their correlation to conventional 2D cephalometric measurements. To analyze changes in three-dimensional shape of the symphysis due to growth and orthodontic treatment. METHODS: This was a retrospective analysis of CBCTs of healthy orthodontic patients. 32 subjects were included, 16 males and 16 females. Mean ages of 10.6 ± 1.5 years and 15.0 ± 0.9 years before and after treatment, respectively. The mean follow up time was 4.3 years. Subjects free of any craniofacial anomalies, and no observable pathology on panoramic radiograph were. 15 subjects had CVM 1 and 17 subjects had CVM 2 before orthodontic treatment. All subjects had CVM 5 after orthodontic treatment. For the first phase, 3D mandibular landmark identifications were digitized. Planes and landmarks were constructed and compared with conventional 2D mandibular measurements. For the second phase, mandibles were isolated by removing surrounding structures. Pearson correlation and paired t-test were performed to test for correlation and differences between 2D and 3D measurements, respectively. Statistical analysis was performed using SAS 9.4. Software. MorphoJ software (Version 2.0, www.flywings.org.uk) was used for symphysis shape analysis; and Discriminant Function Analysis (DFA) between pre-treatment and post-treatment was used for statistical analysis of the symphysis. RESULTS: We found statistical significant positive correlation between 2D and 3D pre-treatment ramus height (P-value =0.01), post-treatment ramus height (P-value < 0.0001), pre-treatment corpus length (P-value 0.0003), post-treatment corpus length (P-value 0.04), pre-treatment gonial angle (P-value <0.0001), and post-treatment gonial angle (P-value=0.05). Also, statistically significant differences in 2D ramus height (P=0.001), 3D ramus height (P-value=0.002), 2D corpus length (P-value <0.01), and 3D corpus length (P-value <0.01). For symphysis shape comparing between pre-treatment and post-treatment, we found that there is no statistically significant difference between them (P-value= 0.99). CONCLUSION: These results demonstrated statistically significant positive correlation between certain 2D and 3D measurements, pre-treatment and post-treatment differences in 2D and 3D measurements showed consistent results. Symphysis shapes do break out as distinctly separate groups, but the differences between the means is small

Sagittal and Vertical Growth of the Maxillo–Mandibular Complex in Untreated Children: A Longitudinal Study on Lateral Cephalograms Derived from Cone Beam Computed Tomography

The aim of this longitudinal study was to evaluate the sagittal and vertical growth of the maxillo–mandibular complex in untreated children using orthogonal lateral cephalograms com-pressed from cone beam computed tomography (CBCT). Two sets of scans, on 12 males (mean 8.75 years at T1, and 11.52 years at T2) and 18 females (mean 9.09 years at T1, and 10.80 years at T2), were analyzed using Dolphin 3D imaging. The displacements of the landmarks and rotations of both jaws relative to the cranial base were measured using the cranial base, and the maxillary and mandibular core lines. From T1 to T2, relative to the cranial base, the nasion, orbitale, A-point, and B-point moved anteriorly and inferiorly. The porion moved posteriorly and inferiorly. The ANB and mandibular plane angle decreased. All but one subject had forward rotation in reference to the cranial base. The maxillary and mandibular superimpositions showed no sagittal change on the A-point and B-point. The U6 and U1 erupted at 0.94 and 1.01 mm/year (males) and 0.82 and 0.95 mm/year (females), respectively. The L6 and L1 erupted at 0.66 and 0.88 mm/year (males), and at 0.41 mm/year for both the L6 and the L1 (females), respectively. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Comparison of conventional and Cone Beam CT synthesized cephalograms

The purpose of this study was to determine whether Cone Beam Computed Tomography (CBCT) synthesized cephalograms provide the same measurement accuracy and precision as conventional cephalograms. In Part I, cephalometric measurements of conventional and CBCT synthesized orthogonal or perspective projections of 10 skulls were compared with each other and with the actual skull measurements. In Part II, actual patient data was used to compare the three imaging modalities and both soft and hard tissue landmarks were utilized. This study demonstrated that most cephalometric measurements are not different for conventional and CBCT synthesized orthogonal and the perspective projections. Although there is a statically significant difference between mid-sagittal image measurements compared to actual skull measurements, these differences are very small .and are unlikely to have clinical relevance. Both of the projections can be used with an expectation of precision and accuracy similar to conventional cephalograms

In Vivo Comparison of Conventional and Cone Beam CT Synthesized Cephalograms

To compare measurements from synthesized cone-beam computed tomography (CBCT) lateral cephalograms using orthogonal and perspective projections with those from conventional cephalometric radiographs

Craniofacial growth of untreated children: A longitudinal CBCT study

Objectives: To conduct a longitudinal study of growth in untreated patients using CBCT. Materials and Methods: CBCT images were obtained for eleven male children (mean age 8.8 years at T1, 11.8 years at T2) and eighteen females (mean age 9.1 years at T1, 10.8 years at T2) and had been taken at least 1 year apart. A non-magnified 2D lateral cephalogram was derived from each CBCT image and superimposed to evaluate sagittal and vertical growth. The transverse widths of various skeletal areas (anterior and posterior nasal cavity, infra orbital foramina, infrazygomatic, mental foramina, Gonion, Antegonion, condyle) and the dentoalveolus at the first molar (2 mm, 6 mm, and 10 mm apical to the CEJ) were measured. Results: This study reports separated male and female average values. Relative to the cranial base, Orbitale, A point, and B point move anteriorly and inferiorly. Porion moves posteriorly and inferiorly. Nasion moves anteriorly and has a wide range of vertical movement. Within the maxilla, A point had variable sagittal movement and moves inferiorly. Within the mandible, B point has variable sagittal movement and moves superiorly, and the condyle moves superiorly. True rotation of the mandible and maxilla occurs in a counterclockwise direction, the inferior border remodels in a clockwise direction, the condyle rotates forward relative to the mandible, and the gonial angle reduces. These processes are correlated with each other and one subject had clockwise rotation of the jaws. The upper and lower first molars mesialize, upright bucco-lingually, and erupt vertically with age. The upper and lower central incisors erupt and the lower incisors procline. The transverse width of the posterior portions of the face increase more than the anterior. The mandibular and maxillary dentoalveoli increase at similar rates corono-apically. The maxillary dentoalveolus increases more than the mandibular dentoalveolus. Conclusions: Angular measurements with N, Or, Po, A, and B may not be reliable for longitudinal growth evaluation. This study confirms the unique facial patterns and correlations between developing processes described by Bjork and Skieller. The posterior skeletal increases in the mandible seems to primarily be the result of lengthening of the mandibular body. The small dentoalveolar increases in the mandible is likely the result of periosteal apposition. The skeletal and dentoaveolar transverse increases in the maxilla reflect the greater increases in the posterior than anterior portions of the mid-palatal suture. The width of the posterior portions of the maxilla and mandible increase in a coordinated fashion. The vertical eruption and bucco-lingual uprighting of the upper and lower first molars seem to bridge the differential sagittal, vertical, and transverse growth of the maxilla and mandible

Comparative linear accuracy of cone beam CT derived 3D images in orthodontic analysis.

Objective . To compare the in vitro reliability and accuracy of linear measurements between cephalometric landmarks on CBCT 3D images with varying basis projection images to direct measurements on human skulls. Methods . Sixteen linear dimensions between anatomical sites marked on 19 human skulls were directly measured. Skulls were imaged with CBCT at three settings: 153, 306, and 612 basis projections. The mean absolute error and modality mean of linear measurements between landmarks on 3D images were compared to the anatomic truth. Results . No difference in mean absolute error between the scan settings was found. The average skull absolute error between marked reference points were less than the distances between unmarked reference sites. Conclusion . CBCT measurements were consistent between scan sequences and for direct measurements between marked reference points. Reducing the number of projections for 3D reconstruction did not lead to reduced dimensional accuracy and potentially provides reduced patient radiation exposure

Contributions to the three-dimensional virtual treatment planning of orthognathic surgery

Orientadores: José Mario De Martino, Luis Augusto PasseriTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A tecnologia mais recente à disposição da Cirurgia Ortognática possibilita que o diagnóstico e o planejamento do tratamento das deformidades dentofaciais sejam realizados sob uma representação virtual tridimensional (3D) da cabeça do paciente. Com o propósito de contribuir para o aperfeiçoamento desta tecnologia, o trabalho apresentado nesta tese identificou e tratou quatro problemas. A primeira contribuição consistiu na verificação da validade da hipótese de que a mudança de definição do plano horizontal de Frankfort não produz diferenças de medição clinicamente relevantes quando sob indivíduos cujos crânios são consideravelmente simétricos. Os resultados da análise realizada no contexto deste tese indicam que, ao contrário do que se presumia, a hipótese é falsa. A segunda contribuição consistiu na extensão do método de análise cefalométrica de McNamara para que ele pudesse produzir valores 3D. Ao contrário de outros métodos de análise cefalométrica 3D, a extensão criada produz valores verdadeiramente 3D, não perde as informações do método original e preserva as definições geométricas originais das linhas e planos cefalométricos. A terceira contribuição consistiu a) no estabelecimento de normas cefalométricas para brasileiros adultos de ascendência europeia, a partir de imagens de tomografia computadorizada de feixe cônico, que produz uma imagem craniofacial mais precisa e confiável do que a telerradiografia; e b) na avaliação de dimorfismo sexual, para a identificação de características anatômicas diferenciadas entre homens e mulheres desta população. A quarta e última contribuição consistiu na automatização da principal etapa da tecnologia em questão, na qual o cirurgião executa o reposicionamento dos segmentos ósseos maxilares no crânio. O método criado é capaz de corrigir automaticamente os problemas dentofaciais mais comuns tratados pela Cirurgia Ortognática, que envolvem maloclusão esquelética, assimetria facial e discrepância de maxilares. Todas as contribuições deste trabalho foram publicadas em periódicos internacionais do campo da Odontologia e afinsAbstract: The latest technology available for orthognathic surgery allows the diagnosis and treatment planning of dentofacial deformities based on a three-dimensional (3D) virtual representation of the patient's head. In order to contribute to the improvement of this technology, the work presented in this thesis identified and treated four problems. The first contribution consisted in testing the validity of the hypothesis that changing the definition of the Frankfort horizontal plane does not produce clinically relevant measurement differences for subjects whose skulls are considerably symmetrical. The results of the analysis performed in this thesis indicate that, contrary to what was presumed, the hypothesis is false. The second contribution is an extension of the McNamara's method of cephalometric analysis to produce 3D values. Unlike other methods of 3D cephalometric analysis, the extension produces true 3D values, does not lose information captured by the original method, and preserves the original geometric definitions of the cephalometric lines and planes. The third contribution consisted in a) establishing cephalometric norms for Brazilian adults of European descent, based on images from cone-beam computed tomography, which produce a more accurate and reliable craniofacial image than cephalometric radiography; and b) evaluating sexual dimorphism, for the identification of distinct anatomic features between males and females of this population. The fourth contribution consisted in automating the main stage of the technology in question, in which the surgeon performs the positioning of jaw bone segments in the skull. The created method is able to automatically correct the most common dentofacial problems treated by orthognathic surgery, which involves skeletal malocclusion, facial asymmetry, and jaw discrepancy. The contributions of this work were published in international journals of the field of Dentistry and relatedDoutoradoEngenharia de ComputaçãoDoutor em Engenharia ElétricaCAPE

Applications of Cone Beam Computed Tomography in Orthodontics and Endodontics

Stelt, P.F. van der [Promotor]Sanderink, G.C.H. [Copromotor