The mylohyoid line is highly variable but does not affect the microarchitecture of the edentulous alveolar bone - an anatomical micro-CT study.

OBJECTIVES: To evaluate in the absence of teeth the variability of the mylohyoid line (ML), the microarchitecture of the adjacent bone, and whether the variable prominence/width of the ML is associated with the quality of the adjacent bone. METHODS: µCT scans of 28 human mandibles from anatomical specimens were analyzed. The following parameters were assessed in four edentulous areas (first and second premolar (PM), first, second, and third molar (M1/2/3)): ML width, cortical thickness (CtTh), average cortical- (Avg.Ct.BV/TV), and trabecular bone volume fraction (Avg.Tb.BV/TV). RESULTS: The ML width increased from the PM towards the M2 region, which also showed the highest variance (range: 0.4-10.2 mm). The CtTh showed a decrease in the M3 region, while Avg.Ct.BV/TV and Avg.Tb.BV/TV hardly differed among the regions. In the multivariable model on the effect of the various parameters on the ML width, only gender and tooth region were significant. Specifically, male specimens were associated with a wider ML width compared to female specimens and the M2 region was associated with a wider ML width compared to the other tooth regions. CONCLUSION: The ML width was not associated with the cortical and trabecular bone quality in the adjacent bone, while gender and tooth region had a significant effect. Specifically, the ML width was lower in female, but peaked in the M2 region with a median width of 3-4 mm. CLINICAL RELEVANCE: From a clinical point of view, it was confirmed that the ML is in general a highly variable structure, especially in the M2 region, but the ML width does not allow any conclusions on the bone quality. Altogether, this underlines the need for an individual and accurate diagnostic prior to any surgical intervention.

Immediate small-diameter implants as abutments for an overdenture in the edentulous atrophic mandible: report of immersion endoscopic bone in vivo, and histologic bone-implant evaluation after 6 months of function / Implantes de pequeño diámetro como soporte inmediato de sobredentaduras en hueso alveolar mandibular atrófico: reporte de endoscopía de inmersion in vivo y evaluación histológica a los 6 meses de función

The aim of this report was to endoscopically evaluate bone quality in vivo in the immediate installation of temporary small-diameter implants, and again after 6 months of function, through an attachments system for overdenture, in the atrophic mandible of a patient. We also histologically evaluated bone-implant interaction in these temporary small-diameter implants, once the success of the osseointegration of the submerged implants was guaranteed. A patient received a total of 6 implants in the atrophic mandible, two of which were immediately loaded with a provisional prosthesis, and four were left to heal in a submerged way. Further, an immersion endoscopic evaluation was performed during bone drilling, and this showed a compact bone structure with limited vascularization and predominantly cortical structure.This immediate loading protocol involving an overdenture retained by two small-diameter implants of 2.9 mm in the atrophic mandible proved to be successful after 6 months of loading. Clinical and histologic osseointegration was consistently achieved for both of the retrieved immediately loaded implants. This modality allows the patient to be restored with a stable, functional, and aesthetic prosthesis during the osseointegration period of submerged implants and soft-tissue healing, before the removal of the provisional implants. The histological evaluation of bone-implant contact found that the space between the implant threads closer to the surface was filled with woven bone and lamellar bone, but the tissue in contact with the cervical portion of the implants was compatible with cortical bone organization. Also, the newly formed bone has a regular cell distribution and characteristics of advanced maturation after 6 months of function in the atrophic mandible. Anchored overdentures in 2 to 4 small-diameter implants (2.9 mm) for edentulous patients with severe atrophy of the mandible with cortical bone would be a minimally invasive alternative.

Vertical bone measurements from cone beam computed tomography images using different software packages

This article aimed at comparing the accuracy of linear measurement tools of different commercial software packages. Eight fully edentulous dry mandibles were selected for this study. Incisor, canine, premolar, first molar and second molar regions were selected. Cone beam computed tomography (CBCT) images were obtained with i-CAT Next Generation. Linear bone measurements were performed by one observer on the cross-sectional images using three different software packages: XoranCat®, OnDemand3D® and KDIS3D®, all able to assess DICOM images. In addition, 25% of the sample was reevaluated for the purpose of reproducibility. The mandibles were sectioned to obtain the gold standard for each region. Intraclass coefficients (ICC) were calculated to examine the agreement between the two periods of evaluation; the one-way analysis of variance performed with the post-hoc Dunnett test was used to compare each of the software-derived measurements with the gold standard. The ICC values were excellent for all software packages. The least difference between the software-derived measurements and the gold standard was obtained with the OnDemand3D and KDIS3D (-0.11 and -0.14 mm, respectively), and the greatest, with the XoranCAT (+0.25 mm). However, there was no statistical significant difference between the measurements obtained with the different software packages and the gold standard (p> 0.05). In conclusion, linear bone measurements were not influenced by the software package used to reconstruct the image from CBCT DICOM data.

Computer graphics applied to anatomy: a study of two Bio-CAD modeling methods on finite element analysis of human edentulous hemi-mandible / Computación gráfica aplicada a la anatomía: un estudio de dos métodos de modelización Bio-CAD sobre el análisis de elementos finitos de hemimandíbulas edéntulas humanas

Modeling is a step to perform a finite element analysis. Different methods of model construction are reported in literature, as the Bio-CAD modeling. The purpose of this study was to perform a model evaluation and application using two methods of Bio-CAD modeling from human edentulous hemi-mandible on the finite element analysis. From CT scans of dried human skull was reconstructed a stereolithographic model. Two methods of modeling were performed: STL conversion approach (Model 1) associated to STL simplification and reverse engineering approach (Model 2). For finite element analysis was used the action of lateral pterygoid muscle as loading condition to assess total displacement (D), equivalent von-Mises stress (VM) and maximum principal stress (MP). Two models presented differences on the geometry regarding surface number (1834 (model 1); 282 (model 2)). Were observed differences in finite element mesh regarding element number (30428 nodes/16683 elements (model 1); 15801 nodes/8410 elements (model 2). D, VM and MP stress areas presented similar distribution in two models. The values were different regarding maximum and minimum values of D (ranging 0­0.511 mm (model 1) and 0­0.544 mm (model 2), VM stress (6.36E-04­11.4 MPa (model 1) and 2.15E-04­14.7 MPa (model 2) and MP stress (-1.43­9.14 MPa (model 1) and -1.2­11.6 MPa (model 2). From two methods of Bio-CAD modeling, the reverse engineering presented better anatomical representation compared to the STL conversion approach. The models presented differences in the finite element mesh, total displacement and stress distribution.

El modelado es un paso para llevar a cabo un análisis de elementos finitos. Entre los diferentes métodos de construcción del modelo que se presentan en la literatura, está el modelado Bio-CAD. El propósito de este estudio fue realizar una evaluación del modelo y aplicación utilizando dos métodos de modelado de Bio-CAD desde la hemimandíbula humana edéntula en el análisis de elementos finitos. Desde tomografías computarizadas de cráneos humanos secos, fue reconstruido un modelo de estereolitografía. Se realizaron dos métodos de modelización: enfoque conversión STL (Modelo 1) asociado a simplificación STL y enfoque de ingeniería inversa (Modelo 2). Para el análisis de elementos finitos se utilizó la acción del músculo pterigoideo lateral como condición de carga para evaluar desplazamiento total (D), lo que equivale tensión de von Mises (VM) y la tensión principal máxima (MP). Los dos modelos presentan diferencias en la geometría de la superficie en relación con el número (1834 (modelo 1), 282 (modelo 2)). Se observaron diferencias en la malla de elementos finitos con respecto a número de elemento (30428 nodos/16683 elementos (modelo 1) y 15.801 nodos/8410 elementos (modelo 2)). La D, VM y áreas de tensión MP presentan distribución similar en ambos modelos. Los valores fueron diferentes respecto a los valores máximo y mínimo de D (desde 0 hasta 0,511 mm (modelo 1) y 0 a 0,544 mm (modelo 2), tensión VM (6,36E-04 - 11,4 MPa (modelo 1) y 2,15e-04 - 14,7 MPa (modelo 2) y tensiones MP (-1,43 a 9,14 MPa (modelo 1) y -1,2 a 11,6 MPa (modelo 2)) a partir de dos métodos de modelado de Bio-CAD. La ingeniería inversa presenta una mejor representación anatómica en comparación con el enfoque de conversión STL. Los modelos presentan diferencias en la malla de elementos finitos, el desplazamiento total y la distribución de la tensión.

Estudio de la localización del foramen mentoniano en mandíbulas maceradas con diferentes grados de edentulismo / Study of the localization of the mental foramen in macerated mandibles with different degree of edentulism

El estudio de la localización del foramen mentoniano se realiza estableciendo su posición por medio de la inspección y palpación de estructuras vecinas relacionadas. Se sabe de la importancia de ese elemento, ya que de él emerge un paquete neurovascular. La correcta determinación de su localización viene a facilitar actividades clínicas tales como la realización de anestesias, implantes, cirugías, así como también, la colocación de prótesis. Fueron analizadas en este trabajo, tres grupos de mandíbulas maceradas: 53 dentadas (presencia de dientes o de sus alvéolos), 55 desdentadas posterior e 62 desdentadas (con reabsorción de todo el proceso alveolar), sumando 170 piezas. En estas mandíbulas fueron realizadas mediciones del foramen mentoniano así como la distancia a estructuras vecinas, con el objetivo de predecir la localización de este foramen. Las estructuras anatómicas vecinas usadas como referencia fueron: base de la mandíbula, pogonion (punto craneométrico) y reborde alveolar. Fue realizado un análisis estadístico en cada grupo, comparándolos posteriormente. Se observaron diferencias entre los tres grupos, debido a la presencia o ausencia de los dientes, relacionado a la mayor o menor cantidad de hueso presente y, así, modificando la localización del foramen mentoniano cuando es medido desde el reborde alveolar; llegando en algunos casos a obtenerse valor cero en la medición, por la reabsorción ósea. En consecuencia, el foramen mentoniano se encontraba más próximo del reborde alveolar en las mandíbulas desdentadas, seguidas por las desdentadas posterior, y de éstas, por las dentadas.

The study of the mental foramen localization has the aim to establish its position through the inspection and touching related to the surrounded structures. Taking notice of the importance of this structure, since from it emerges a neurovascular bundle the correct determination of its localization facilitates the clinical activities such as the realization of anesthesia, implants, surgeries, as well as the placement of prosthesis. In this work three groups of macerated mandibles were used: 53 dentate (presence of teeth or their alveolus), 55 posterior edentulous and 62 edentulous (with reapsortion of all the alveolar process), totalizing 170 specimens. These mandibles were used to do mensurations of the mental foramen until their surrounding structures, with the aim of determining the localization of this foramen. The surrounding anatomic structures used as a reference were: the basis of the mandible, pogonion (craniometric point) and alveolar edge. The statistical analyses in each group were done, comparing among them later. There were observed differences between the three groups, due to the presence or not of the teeth meaning less or high quantity of the bone and, in this way, modifying the localization of the mental foramen when mensurated up to the alveolar edge, in some cases we could obtain a zero value of this distance, such was the osseous reabsorption. Therefore the mental foramen was localized closer of alveolar edge in the edentulous mandibles, followed by posterior edentulous and these, by the dentate.

Estudio del grosor del cuerpo mandibular en brasileños adultos / Study of the thickness of the mandibular body in Brazilian adults

Es indiscutible la importancia del correcto conocimiento del espesor de la mandíbula en las regiones donde son realizadas ciertas intervenciones, tales como los implantes dentarios. En vista de esto, hicimos este estudio que tuvo como objetivo la determinación del espesor medio del cuerpo de mandíbulas maceradas. Fueron utilizadas 150 mandíbulas de ambos sexos, todas pertenecientes al Departamento de Anatomia do Instituto de Ciências Biomédicas da Universidade de São Paulo. Éstas fueron divididas en tres grupos: 68 edéntulas, 38 dentadas y 44 desdentadas posterior, para cada una de ellas realizamos nueve medidas. Esas mediciones fueron hechas utilizándose un caliper digital de la marca Mitutoyo modelo CD-6” CS. Los valores obtenidos fueron sometidos a análisis estadístico siendo los valores medios encontrados: 10,24mm para las mandíbulas edéntulas, 11,33mm para las mandíbulas desdentadas posterior y 11,65mm para las mandíbulas dentadas. Concluimos que el espesor medio del cuerpo de mandíbulas edéntulas es menor de que el observado en mandíbulas desdentadas posterior, que a su vez, es menor de que el observado en mandíbulas dentadas e incluso, que existe diferencia significativa cuando consideramos los valores obtenidos en la región de la intersección de la línea mediana con una línea horizontal que pasa tangente al margen superior del foramen mentoniano, entre los grupos demandíbulas edéntulas y desdentadas posterior, así como para los grupos de mandíbulas dentadas y edéntulas. En todos los casos el nivel de significancia fue de p<0,05.

The importance of knowing the exact thickness of the mandible in the area where certain interventions, such as the dental implants, are done is undeniable. Due to this fact, we carried out this study to ascertain the average body thickness of the macerated mandibles. We used 150 mandibles from both genres belonging to the Department of Anatomy at the “Instituto de Ciências Biomédicas” from the “Universidade de São Paulo”. They were divided into three groups: 68 edentulous, 38 dentate and 44 posterior edentulous, and for each of them, nine measurings were done. This measuring were accomplished with a CD-6’’ CS Mitutoyo digital paquimeter. The obtained values undergone a statistic analysis and the obtained average values were: 10.24mm for the edentulous mandibles, 11.33mm for the posterior edentulous mandibles and 11.65mm for the dentate mandibles. We could conclude that the average thickness of the edentulous mandibles body is shorter than the one in the posterior edentulous mandibles, and this one is shorter than the ones from the dentate mandibles, and more, there is a significant difference between the values obtained in the intersection region of the median line with the horizontal line that touches the superior margin of the mental foramen, among the group of the edentulous and posterior edentulous mandibles, as well as for the group of the dentate and edentulous mandibles. In both cases the level of significance is p<0.05.

Dental management of low socioeconomic level patients before radiotherapy of the head and neck with special emphasis on the prevention of osteoradionecrosis

Head and neck cancer patients need to receive dental care previously to radiotherapy. Even patients who regularly visit dental offices need special attention including profilatic and curative treatments. The purposes of this study were to evaluate the dental status of Brazilian head and neck squamous cell carcinoma patients with low socioeconomic level as well as to discuss the dental treatment performed and the oral side effects of radiotherapy. Forty patients with head and neck squamous cell carcinoma received dental care and dental extractions prior to radiotherapy and were were followed up for a mean period of 28.7 months after the cancer treatment. Before radiotherapy, 28 patients were dentulous and 12 edentulous, and all of them had poor oral health and hygiene. The most common treatment performed were dental extraction and 23 patients had 8.6 teeth extracted on average. One out of 9 (11.1 percent) patients developed radiation caries and 5 out of 23 cases (21.3 percent - Group I) developed osteoradionecrosis, being only 1 case associated with previous dental extraction. Brazilian low-socioeconomic level patients with head and neck cancer were submitted to multiple dental extractions due to poor dental condictions and inadequate oral care. The dental treatment did not prevent osteoradionecrosis, which presumably presented a multifactorial etiology in most cases.

Pacientes portadores de carcinomas espinocelulares em cabeça e pescoço necessitam receber tratamento odontológico antes da radioterapia. Mesmo pacientes que visitam regularmente consultórios odontológicos requerem especial atenção incluindo profilaxias e tratamentos curativos. Os objetivos desse estudo foram avaliar a condição odontológica de 40 pacientes de baixo nível sócio-econômico antes da radioterapia em cabeça e pescoço e discutir o tratamento odontológico realizado. Os pacientes foram acompanhados durante o tratamento oncológico. Antes da radioterapia, 28 pacientes eram dentados e doze edêntulos, sendo que todos esses apresentavam péssimas condições sistêmicas e higiene oral deficiente. O tratamento mais comumente empregado foi a extração dentária e 23 pacientes tiveram a média de 8,6 dentes extraídos (Grupo I). Um em 9 (11,1 por cento) pacientes desenvolveram cárie por radiação e 5 em 23 (21,73 por cento) osteorradionecrose, sendo um caso associado a extrações dentárias prévias à radioterapia e outros de origem multifatorial. Pacientes de baixo nível socioeconômico com carcinoma espinocelular em cabeça e pescoço receberam múltiplas extrações dentárias devido à condição dentária precária e má higienização. O tratamento odontológico não preveniu a osteorradionecrose, que apresenta origem multifatorial na maioria dos casos.