CBCT analysis of the relative position between maxillary central incisors and alveolar bone in Southern Chinese adults / 口腔疾病防治

Objective@#Exploring the position and bone wall thickness characteristics of the maxillary central incisors in Southern Chinese adults to provide a clinical reference for the design of immediate maxillary central incisor implantation surgery.@*Methods@#The hospital ethics committee approved the study, and the patients provided informed consent. CBCT images of 990 adult patients (aged 20-79 years) from the Stomatology Hospital (January 2018 to December 2021) were categorized based on the dental arch form and age-sex groups. Sagittal CBCT images of the maxillary central incisors were used to measure the labial and palatal bone thickness wall at 4 mm the CEJ to apical, the middle of the root, and the angle between the tooth long axis and the long axis of the alveolar process, to compare the thickness of the labial and palatal bone walls in samples of male and female patients, and to explore the relationship between the angle between the tooth long axis and the alveolar process long axis in samples of male and female patients in different age groups (20-39 years; 40-59 years; 60-79 years).@*Results@#Significant differences were found in the labiopalatine side of the alveolar bone of the maxillary incisor root position. A total of 95.8% (948/990) of the maxillary incisors were positioned more buccally, 4.1% (41/990) were positioned more midway, and 0.1% (1/990) were positioned more palatally. The thicknesses of the bone wall at the CEJ of 4 mm below the palatal side, the middle of the root, and at the apex were greater (1.82 ± 0.56 mm, 3.20 ± 1.10 mm, and 7.70 ± 2.00 mm, respectively) than those at the labial side (1.21 ± 0.32 mm, 0.89 ± 0.35 mm, and 1.86 ± 0.82 mm, respectively), with statistical significance (P<0.05). Male bone wall thickness was generally greater than female bone wall thickness (P<0.05). The angle between the long axis of male teeth and the alveolar bone was 14.77° ± 5.66°, while that of female teeth was 12.80° ± 5.70°, with a statistically significant difference (P<0.05). The angle between the long axis of teeth and the alveolar bone in the 40-59-year-old group and the 60-79-year-old group was greater than that in the 20-39-year-old group, and the difference was statistically significant (P<0.05).@*Conclusion@#A total of 95.8% of adults in South China have maxillary central incisors with root deviation toward the labial bone cortex. The thickness of the labial bone wall is much thinner than that of the labial bone wall, which is the middle of the thickness of the root. In Southern Chinese adults, the angle between the upper central incisor and the long axis of the alveolar bone in males is greater than that in females, and the degree of the angle increases with age. It is recommended to pay attention to the thickness of the bone wall around the root and the angle between the teeth before immediate implantation surgery to choose a reasonable implantation plan.

A Narrative Review of Alveolar Bone Analysis and CBCT Classification related to Immediate Implant Placement in The Anterior Maxilla

@#Immediate implant placement into fresh extraction sockets has gained a lot of attention in implant dentistry. Besides proper risk assessment, the evaluation of tooth anatomy aids the clinicians to select the finest treatment protocol. Cone Beam Computed Tomography (CBCT) imaging was frequently used for alveolar bone analysis prior to tooth extraction in immediate implant placement. As an ideal position is required to prevent a buccally tilted implant or too palatal implant placement, various authors have proposed the treatment guidelines for immediate implant placement in the anterior maxilla. Although insightful, the previous classification was lacking anatomic variant and key anatomical features of alveolar bone and tooth angulation. Furthermore, there is no standardization method of measuring the specific degree of tooth angulation in CBCT scans that could possibly be used in clinical setting for appropriate treatment protocol. Thus, it is essential for the clinician to have adequate knowledge on the role of facial alveolar bone, palatal alveolar bone and tooth angulation related to immediate implant before selecting the appropriate treatment guidelines based on the classification reviewed. In this review, the previous quantitative measurements were categorized, and the previous classification was listed for the sake of familiarity by the dental practitioner with the major updates on implant placement strategy, patient selection and to reduce the rate of surgical complications.

Analysis of initial stress distribution in palatal bone around the implant in lingual orthodontics for single and double palatal implant systems: a FEM study

ABSTRACT Objective: To analyze and compare the Von Mises stress and principal stress distribution in palatal bone around the palatal implant in lingual orthodontics (LiO) for single and double palatal implant systems with varying lengths of lever arm. Methods: Two groups were assessed: single (Group 1) and double (Group 2) palatal implant systems, which were further divided into two subgroups, based on lever arm length, for analyzing stress in the palatal bone around the implant. Hence, two 3D finite element models of bilateral maxillary first premolar extraction cases were constructed in each system. Lingual brackets (0.018-in slot) were positioned at the center of the clinical crown. In both systems, 150g of retraction force was applied, and ANSYS v. 12.1 software was used to analyze and compare stress in the palatal bone around the palatal implant. Results: In this study, higher stress was observed at the inner threaded interface of cortical bone. Magnitude of Von Mises stress was higher in Group 2 (0.63 MPa and 0.65 MPa) in comparison to Group 1 (0.29 MPa and 0.29 MPa). Similarly, magnitude of principal stress was higher in Group 2, in comparison to Group 1. Higher stress was observed in the apical region of the implant-bone interface of cancellous bone. Conclusion: This study concluded that the Von Misses stress as well as principal stress in the palatal bone were within the optimal limit in both groups. Finally, it can be concluded that both systems (single and double palatal implant) were safe for the patients in clinical use of 150g of retraction force.

RESUMO Objetivo: Analisar e comparar as tensões de Von Mises e a distribuição das tensões principais no osso palatino ao redor de implantes palatinos em Ortodontia Lingual (OL) para sistemas de implantes palatinos unitários ou duplos com comprimentos variados do braço de alavanca. Métodos: Foram delineados dois grupos para o presente estudo: Grupo 1 - com sistema de implante palatino unitário e Grupo 2 - com sistema de implantes palatinos duplos. Em seguida, os grupos foram divididos em dois subgrupos, com base no comprimento do braço de alavanca, para analisar as tensões no osso palatino ao redor do implante. Para cada sistema, foram construídos dois modelos 3D de elementos finitos (MEF) de casos com extração bilateral de primeiros pré-molares superiores. Braquetes linguais (slot 0,018") foram posicionados no centro das coroas clínicas. Nos dois sistemas, foram aplicados 150g de força de retração nos dentes anteriores, e o software ANSYS v. 12.1 foi usado para analisar e comparar as tensões no osso palatino ao redor dos implantes. Resultados: Foram observados maiores níveis de tensões na parte interna rosqueada no osso cortical. A magnitude das tensões de Von Mises foi maior no Grupo 2 (0,63MPa e 0,65MPa) em comparação ao Grupo 1 (0,29MPa e 0,29MPa). De forma semelhante, foi observada maior magnitude das tensões principais no Grupo 2 do que no Grupo 1. Maiores tensões foram observadas na região apical da interface osso/implante no tecido ósseo esponjoso. Conclusão: A tensões de Von Mises e as tensões principais no osso palatino ficaram dentro do limite ideal em ambos os grupos. Ambos os sistemas de implantes palatinos (unitário e duplo) foram seguros para o uso clínico em pacientes com força de retração de 150g.

Contribución al Estudio Descriptivo del Foramen y Canal Palatino Mayor / Contribution to the Descriptive Study of the Foramen and Greater Palatine Canal

RESUMEN: El foramen y canal palatino mayor (FPM y CPM) comunican boca con fosa pterigopalatina. El conocimiento adecuado de su morfología, permite el abordaje anestésico del nervio maxilar. En el vivo, el FPM está recubierto por una mucosa gruesa, debido a esto los puntos de referencia óseos y dentarios son importantes para ubicar el sitio de punción. Se ha descrito gran variabilidad en cuanto a la etnia, posición, forma, diámetros, longitudes y permeabilidad. Este estudio tuvo como objetivo describir éstas características en cráneos de adultos chilenos. Se utilizaron 31 cráneos de ambos sexos. En los paladares se determinó; forma, largo, profundidad y ancho. En los FPM se consideró su forma, diámetros y localización. En los CPM se registró su permeabilidad y su coincidencia con la forma del FPM. Los registros se realizaron con cámara digital, compás de precisión, caliper digital, compas tridimensional de Korkhaus y sonda metálica. Los resultados muestran un predominio de la forma cuadrada del paladar por sobre las formas triangular y redondeada. Las mediciones de su largo, ancho y profundidad indican diferencias por sexo y por etnia. La forma del FPM no muestra diferencia por sexo, primando la forma ovalada por sobre la fusiforme y la redondeada. La posición de este mismo foramen tampoco muestra diferencias sexuales, primando la posición frente al tercer molar superior, seguida por la posición frente al espacio entre segundo y tercer molar superior y por último frente al 2do molar superior. Las dimensiones del FPM son mayores en individuos masculinos. Los CPM se observaron en su totalidad permeables y los FPM no siempre coincidieron en forma con la sección transversal del CPM. Estos resultados y su comparación con la literatura indican variaciones importantes, lo que impide establecer directrices objetivas a la técnica anestésica que utiliza esta vía anatómica.

ABSTRACT: The greater palatine foramen and canal (GPF and GPC) communicate with the pterygopalatine fossa. The adequate knowledge of its morphology allows the anesthetic approach of the maxillary nerve. In vivo, the GPF is covered by a thick mucosa, therefore, the bone and dental reference points are important to locate the puncture site. Great variability has been described in terms of ethnicity, position, shape, diameters, lengths and permeability. The objective of this study was to describe these characteristics in skulls of Chilean adults. 31 skulls of both sexes were used. In the palates shape, length, depth and width were determined. In the GPF its shape, diameters and location were considered. In the GPC, their permeability and their coincidence with the shape of the GPF were recorded. The records were made with digital camera, precision compass, digital caliper, Korkhaus three-dimensional compass and metallic probe. The results show a predominance of the square shape of the palate over the triangular and rounded forms. The measurements of its length, width and depth indicate differences by sex and ethnicity. The shape of the GPF shows no difference by sex, with the oval shape prevailing over the fusiform and the rounded. The position of this same foramen also shows no sexual differences, with the position prevailing against the upper third molar, followed by the position in front of the space between the upper second and third molars and finally against the upper 2-molar. The dimensions of GPF are greater in male individuals. The GPC were found to be entirely permeable and the GPF did not always coincide in form with the cross section of the GPC. These results and their comparison with the literature indicate important variations, which prevents establishing objective guidelines for the anesthetic technique used in these cases.

Caninos superiores retenidos por palatino: radiografía panorámica para evaluar ubicarlos en el arco dentario / Palatally impacted upper canines: panoramic radiography to assess their location in the dental arch

Los caninos superiores permanentes, estadísticamente, se encuentran entre las piezas dentarias que con más frecuencia quedan en retención ósea,después de los terceros molares.Sin embargo, los caninos, estética, funcionalmente, y para mantenimiento de las relaciones contactantes,a la hora de valorarlos en boca, desempeñan una función más importante que los terceros molares. Por eso la importancia de poder ubicarlos en el arco dentario. Cuando los ortodoncistas, sobre todo los menos experimentados, se enfrentan a la decisión de conservar los caninos que se encuentran en posiciones deretención ósea palatina, son muchos los interrogantes que se le plantean sobre su posible ubicación con éxito, en el arco dentario. Frecuentemente está la duda de cuál es el límite de la posición de retención para intentar su acomodamiento. Proponemos un simple trazado que se puede hacersobre la ortopantomografia panorámica, marcando dos líneas tangentes a la pared externa delas fosas nasales que se continuarán con los ejes longitudinales de los caninos retenidos de ambos lados. Si queda constituida una figura geométrica de apariencia de un rombo, significa que el extremo de la raíz se encuentra próximo a la posición que anatómicamente le pertenece (fosa canina del maxilar superior), existiendo una alta probabilidad de concluir con éxito su ubicación en el arco dentario.

Statiscally, permanent upper canines are the mostfrequently impacted teeth, after third molars.Upper canines though, have more significancethan third molars aesthetically, functionally andin maintaining contacting relations;thus the importance of bringing them inthe correct position within the dental arch.When an Orthodontist, particularly those lessexperienced, are faced with the decision ofmaintaining canines impacted in the palatal bone;many questions linger regarding the possibilitiesof successful relocation into the dental arch.Frequently, the question lays in the limitationsof moving it from its impacted positionto the correct one.We propose a simple tracing of theOrthopantomogram (OPG), marking twotangent lines to the lateral wall of the nasal cavitycontinuing on the long axis of the impactedcanines of both sides. If the result is a geometricfigure resembling a rhombus, it means thatthe radicular apex is close to the correctanatomical position (maxillary canine fossa),indicating high probabilities of successfullypositioning the impacted tooth.

Quantitative assessment of palatal bone thickness in an ethnic Indian population: A computed tomography study.

Context: Variations in palatal bone thickness (PBT) at various locations have caused considerable problems when using these sites for anchorage purposes. Aims: To find the comparative thickness of the palatal bone at different locations and to validate its morphology for anchorage purposes using mini-implants (MI). Settings and Design: This investigation was undertaken to compare the mean PBT and level of significance of differences between male and female subjects and between two different age-groups. Materials and Methods: The computed tomography (CT) data for 60 patients (30 males and 30 females) in two different age-groups (group A: 15-24 years; group B: 25-35 years) were imported into CAD-based medical software, (MIMICS® ; Materialise, Belgium) for multiplanar reconstruction. The measurements were made in two planes- transverse and sagittal-and at different positions in each of the planes. Statistical Analysis: The mean and standard deviations of the PBT at different points were calculated. The Student's t-test and Mann-Whitney U test were used for comparisons between the groups. Results: Significant variations were observed in the thickness of the palatal bone for both groups tested, with the anterior region at 4 mm behind the incisive papilla showing the maximum thickness. Conclusions: Despite the palatal bone being thickest in the mid-palatal suture (MPS) region, this is not the ideal site for anchorage purposes due to inadequate calcification and interposition of connective tissue, especially in young growing children. So, the alternate optimum position is the paramedian region, 3 mm lateral to the MPS and 4 mm from the incisive foramen (IF).