Anatomical considerations relevant to implant procedures in the mandible

The authors review anatomical facts significant for preoperative planning of implant procedures in the mandible. This planning includes the precise evaluation of distinct anatomical factors, such as the position of the mandibular canal, the width of the mandibular cortical plates and the degree of involutive changes of the inferior dental artery.The mandibular canal is usually situated centrally in the mandibular corpus, slightly closer to the lingual cortex in its distal parts; towards the front, it approaches the vestibular cortical layer. Mesially from the mental foramen, a clearly defined incisive canal is present in only one third of the edentate mandibles.Mandibular corpus of the edentate mandibles consists of cancellous bone enclosed by a shell of compact cortical bone. Cortical layers demonstrate significant variations in width; nervertheless, the widths of lateral cortical layers, generally, enable safe placement of endosseal implants.Finally, in patient’s preoperative assessment, involutive changes of the inferior dental artery should also be considered. During the involution of the mandibular alveolar process, it shows changes of direction and calibre, changes in arborization and, sometimes, complete occlusion of the main trunk. The degree of these involutive changes points out the mandibular vascular supply and the regenerative capacity of the tissues needed for the success of the implant procedure.Les auteurs passent en revue les faits anatomiques importants qu’il convient d’avoir à l’esprit en établissant le programme préopératoire pour la mise en place d’implants dans la mandibule.Ce programme inclut l’évaluation précise des différents facteurs anatomiques tels que la position du canal mandibulaire, la largeur de la corticale mandibulaire et le degré des changements involutifs de l’artère dentaire inférieure.Le canal mandibulaire est habituellement situé au centre du corps mandibulaire, très proche du cortex ventral dans ses portions distales; vers l’avant» il s’approche de la corticale vestibulaire. Mésialement par rapport au foramen mentonnier, un canal incisif bien défini est présent uniquement dans seulement un tiers des mandibules édentées.Le corps mandibulaire des mandibules édentées consiste en un os réduit entouré par un os cortical de type compact. Les couches corticales démontrent des variations de largeur significatives; néanmoins, les largeurs des couches corticales latérales, permettent généralement le placement d’implants endo-osseux en toute sécurité.Enfin, au cours de l’établissement du programme préopératoire du patient, les changements involutifs de l’artère dentaire inférieure devraient également être prises en considération. Au cours de l’involution du processus alvéolaire de la mandibule, cette artère montre des changements de direction et de calibre, des changements de l’arborisation et quelquefois, une complète oblitération de son tronc principal. L’importance de ces changements involutifs, met l’accent sur la suppléance vasculaire de la mandibule et la capacité régénérative des tissus nécessaires pour le succès de la mise en place des implants

Morphometric analysis of mandibular canal: clinical aspects

Results of morphometric analysis of the mandibular canal (MC), carried out on 105 conserved mandibles, 70 being dentate and 35 edentate, was performed. The analysis was carried out on consecutive sections, at mutual intervals of 0.5 cm. In the mandibular ramus sections were carried out obliquely, approximately in the frontal plane, and horizontally, from mandibular foramen to the lowest region of the vertical part of the MC (all together two sections). In the mandibular corpus, consecutive transversal sections were carried out between existing teeth, or at mutual intervals of 0.5 cm in edentate regions.The obtained results pointed out the very close relationship between the MC and lingual cortical plate of the mandibular ramus. In its horizontal part, the average diameter of the MC was 2.6 mm. It was situated more lingually in the molar region; towards the front, it approached the vestibular cortical plate, being closest to it in the region of the second premolar. Similar relationships of the MC and both cortical plates existed in edentate jaws. Relationships of the MC and tooth root apices varied; however, the MC was closest to the apices of the third molar. Mesially from the mental foramen, a clearly defined incisive canal was present in 92% of the dentale mandibles, but only in 31% of the edentate ones. The nearest to the incisive canal was the apex of the first premolar.The authors point out the importance of presented results in everyday practice, especially in oral and maxillofacial surgery. Having in mind the existing relationship between the MC and neighbouring structures, it is possible to avoid the injury of its content during several oral surgical procedures in mandibular ramus and corpus.L’analyse morphométrique du canal mandibulaire (CM) a été faite sur 105 mandibules conservées. Parmices mandibules, 70 étaient partiellement édentées et 35 totalement édentées. Les distances du CM de la couche compacte osseuse de la mandibule et des apex des racines dentaires ont été mesurées sur les coupes successives pratiquées à une distance de 0,5 cm. Dans la région de la branche montante mandibulaire les coupes successives ont été pratiquées suivant le plan horizontal, de l'orifice postérieur du canal mandibulaire à la terminaison de la partie verticale du CM. La région du corps mandibulaire a été traitée par des coupes verticales. Ces sections ont été faites successivement à travers l’espace entre chaque deux dents ou à une distance de 0,5 cm dans les régions édentées.Les résultats obtenus montrent que le CM se dirige obliquement de haut en bas et en avant, très proche de la lame osseuse linguale. Dans la partie horizontale son diamètre est de 2,6 mm en moyenne. Dans la région des dents molaires le CM est très proche de la lame osseuse linguale; en cheminant en avant, le CM s’approche de la lame osseuse buccale dont il est le plus proche dans la région de la P2. Dans les mandibules édentées, le CM a des rapports semblables.La distance du CM des apex des racines dentaires est variable, pourtant il est le plus proche des apex des racines de la M3. Mésialement du trou mentonnier, le canal incisif était clairement individualisé dans 92% des mandibules avec la denture conservée, et dans 31% des mandibules édentées. La première prémolaire était la plus proche du canal incisif.Les auteurs montrent l’importance des résultats présentés pour la stomatologie clinique, surtout pour la chirurgie orale et maxillofaciale. Compte tenu des rapports du CM avec les structures voisines on peut éviter des lésions de son contenu au cours de certaines interventions chirurgicales sur la branche montante et sur le corps de la mandibule

Les rapports du canal mandibulaire avec les faces externes du corps de la mandibule et risques qui en découlent de le léser

The investigations of relations and position of the mandibular canal (CM) were carried out on 80 mandibles (33 dentulous, 27 partly edentulous and 20 completely edentulous).The studies of relations of CM to the sides of mandibular body were accomplished by morphometric analysis of CM on consecutive transversal sections of mandibular body (54 preparations). The relation of the CM to be buccal or to the lingual side is expressed as the distance from the surface of the correspondent side of the mandibular body, which is shown in Table 1. According to these data, the position of the canal is at first proximate to the lingual side, and from the first molar tooth (M1) it approaches the buccal surface of the mandibular body.The position of the entire CM was determined by analysis of mandibular preparations (26) after removing the buccal osseous lamina. These investigations revealed that the position of the CM is predominantly buccal. Reconstruction of relations of the CM to the sides of mandibular body, according to the data obtained from transversal sections, and the real position of the CM are presented in Scheme I.The difference in direction lines of relations and of predominant position of the CM is a consequence of morphological characteristics of mandibular body.Le CM a été étudié sur 80 mandibules (dont 33 avec la denture conservée, 27 peu édentées et 20 totalement édentées). L’analyse morphométrique des rapports du CM a été faite sur les coupes frontales de la mandibule (54). La position du CM en entier a été examinée après la trépanation du corps mandibulaire (26 préparations). La reconstruction des rapports du CM d’après les données obtenues sur les coupes fait apparaître que le canal a d’abord une position linguale, ensuite il croise la M1 et se termine dans une position buccale. Dans la plupart des cas, le CM a, dans la majeure partie de son trajet, une position buccale à cause de la configuration caractéristique du corps mandibulaire

Anatomie chirurgicale de la glande sublinguale

Because of its position, the sublingual gland is clinically important especially in the events of injuries and infections in the anterior part of the sublingual region.The morphology and relationships of this gland were studied by dissection methods applied on 80 fresh or formaldehyde fixed preparations of the mouth floor and of the tongue, which were partly (31 preparations) taken out together with the mandible.As for the shape of the gland, three main types were found: 1° the cuneiform type which was the most frequent (71 %), 2° the pyramidal type which was less frequent (16%) and the fusiform type (13%) which comprised the cases of a very elongated gland (up to 65 mm).The space in which the gland lied had four walls. Its internal wall consisted of the mylohyoid muscle and it comprised the hyoglossus muscle as well when the gland was very elongated. The inferior wall consisted of the mylohyoid muscle and sometimes it comprised also a narrow part of the superior surface of the geniohyoglossus muscle. An osseous depression on the internal side of the mandible represented the external wall of the sublingual gland space. The superior wall is clinically the most significant. It consists of the sublingual mucosa and a sublingual fold. This wall represents a main surgical access to the gland. In edentulous mandibles this mucous fold may be at the level of the upper mandibular border which may hinder the use of the lower dental prosthesis.La morphologie et les rapports de la glande sublinguale ont été étudiés par 80 dissections du plancher de la bouche et de la langue.Trois types différents de glandes ont été définis du point de vue forme: le type cunéiforme (71%), le type pyramidal (16%) et le type fusiforme (13%).La loge de la glande sublinguale possède quatre parois: deux (parois inférieure et interne) de nature musculaire, une (paroi externe) de nature osseuse et une (paroi supérieure) de nature muqueuse

La structure osseuse de la branche montante de la mandibule

Osseous structure of the ramus of mandible (RM) is of a practical clinical significance. Osteosynthesis of fractured segments and the success of the sagittal or the horizontal ramus split osteotomy depends on the cortical bone disposition and thickness.After morphometric investigations of the RM, conducted on 70 mandibles of adults, consecutive horizontal and frontal sections were made. On these sections, the cortical layer was studied and the cortical bone thickness was measured at four previously marked points.In the regard of morphometry, the significant datum is that nearly half of all the cases is grouped round the mean value of any parameter.Cortical bone is continuous and its two main sheets are the buccal and the lingual cortical plates. In its entirety, the buccal cortical plate is thicker than the lingual. The thickness of both cortical plates increases in the direction from the coronoid process to the angle of mandible.L’ostéosynthèse de la branche montante de la mandibule et le succès de l’ostéotomie sagittale ou horizontale de cette branche dépendent de la disposition et de l’épaisseur de sa couche osseuse compacte. Les examens morphométriques qui ont été faits sur 70 mandibules des sujets adultes montrent que presque la moitié de tous les cas se groupent autour de la valeur moyenne des paramètres mesurés (schéma 1 et tableau I).Sur les coupes horizontales et frontales, l’épaisseur des lames compactes buccale et linguale a été mesurée dans certains points prédéterminés et il a été établi que la lame buccale est toujours plus épaisse (schéma 2 et tableau II)

Altérations athéroscléreuses de l’artère dentaire inférieure en corrélation avec celles de la bifurcation carotidienne et de l’aorte abdominale

50 corpses from adults aged 20 to 75 have been used in order to study the atherosclerotic lesions occurring in typical regions (bifurcation of the common carotid artery and the abdominal aorta) and their relationship to atherosclerotic changes in the inferior alveolar artery. Histological analysis revealed that atherosclerotic alterations of the inferior alveolar artery may appear sometimes earlier than it would be expected on the ground of age. Intima cell proliferation and thickening of elastic elements in the middle layer of the arterial wall, the first signs of atherosclerosis, were found already at the beginning of the third decade of life when the signs of this process in the typical regions were not yet evident. Atherosclerosis affects essentially the functional capacity of the inferior alveolar artery. The development of atherosclerosis in the wall of this artery favours an hypovascularization of the mandible, which must be of certain importance in every operative procedure in oral surgery, especially in those inducing a severe and long traumatism in bone and soft tissues, such as dental implantations.Cette étude, faite sur 50 cadavres (de 20 à 75 ans) concerne les altérations athéroscléreuses de l’artère dentaire inférieure et leurs rapports avec les altérations athéroscléreuses dans les territoires typiques (bifurcation carotidienne et aorte abdominale). L’examen histologique a fait apparaître que les altérations athéroscléreuses de l’artère dentaire inférieure peuvent être relativement plus évidentes et précoces que l’on ne s’y attendrait compte tenu de l’âge. Une prolifération cellulaire de l’intima et un épaississement de la lame élastique moyenne dans la paroi artérielle, premiers signes de l’athérosclérose, peuvent apparaître dès30 ans, alors que l’on ne trouve pas encore d’altérations de ce type dans les territoires typiques. L’athérosclérose a une influence cruciale sur la capacité fonctionnelle de l’artère dentaire inférieure puisque celle-ci chemine dans le canal osseux, qui empêche sa dilatation. Le développement de l’athérosclérose dans la paroi de cette artère favorise une hypovascularisation de la mandibule, ce qui a une importance certaine lors de toute intervention en chirurgie orale, surtout lorsqu’elle entraîne un traumatisme grave et prolongée de l’os et des parties molles, comme c’est le cas lors de l’insertion d’implants dentaires

Volcanic impacts on peatland microbial communities: A tephropalaeoecological hypothesis-test

Volcanic eruptions affect peatlands around the world, depositing volcanic ash (tephra) and a variety of chemicals including compounds of sulphur. These volcanic impacts may be important for many reasons, in particular sulphur deposition has been shown to suppress peatland methane flux, potentially reinforcing climatic cooling. Experiments have shown that sulphur deposition also forces changes in testate amoeba communities, potentially relating to the reduced methane flux. Large volcanic eruptions in regions with extensive peatlands are relatively rare so it is difficult to assess the extent to which volcanic eruptions affect peatland microbial communities; palaeoecological analyses across tephra layers provide a means to resolve this uncertainty. In this study, testate amoebae were analysed across multiple monoliths from a peatland in southern Alaska containing two tephras, probably representing the 1883 eruption of Augustine Volcano and a 20th Century eruption of Redoubt Volcano. Results showed relatively distinct and often statistically significant changes in testate amoeba community coincident with tephra layers which largely matched the response found in experimental studies of sulphur deposition. The results suggest volcanic impacts on peatland microbial communities which might relate to changes in methane flux

Prediction of Amyloidogenic and Disordered Regions in Protein Chains

The determination of factors that influence protein conformational changes is very important for the identification of potentially amyloidogenic and disordered regions in polypeptide chains. In our work we introduce a new parameter, mean packing density, to detect both amyloidogenic and disordered regions in a protein sequence. It has been shown that regions with strong expected packing density are responsible for amyloid formation. Our predictions are consistent with known disease-related amyloidogenic regions for eight of 12 amyloid-forming proteins and peptides in which the positions of amyloidogenic regions have been revealed experimentally. Our findings support the concept that the mechanism of amyloid fibril formation is similar for different peptides and proteins. Moreover, we have demonstrated that regions with weak expected packing density are responsible for the appearance of disordered regions. Our method has been tested on datasets of globular proteins and long disordered protein segments, and it shows improved performance over other widely used methods. Thus, we demonstrate that the expected packing density is a useful value with which one can predict both intrinsically disordered and amyloidogenic regions of a protein based on sequence alone. Our results are important for understanding the structural characteristics of protein folding and misfolding

Bronchiectasis and asthma: Data from the European Bronchiectasis Registry (EMBARC)

\ua9 2024 The AuthorsBackground: Asthma is commonly reported in patients with a diagnosis of bronchiectasis. Objective: The aim of this study was to evaluate whether patients with bronchiectasis and asthma (BE+A) had a different clinical phenotype and different outcomes compared with patients with bronchiectasis without concomitant asthma. Methods: A prospective observational pan-European registry (European Multicentre Bronchiectasis Audit and Research Collaboration) enrolled patients across 28 countries. Adult patients with computed tomography–confirmed bronchiectasis were reviewed at baseline and annual follow-up visits using an electronic case report form. Asthma was diagnosed by the local investigator. Follow-up data were used to explore differences in exacerbation frequency between groups using a negative binomial regression model. Survival analysis used Cox proportional hazards regression. Results: Of 16,963 patients with bronchiectasis included for analysis, 5,267 (31.0%) had investigator-reported asthma. Patients with BE+A were younger, were more likely to be female and never smokers, and had a higher body mass index than patients with bronchiectasis without asthma. BE+A was associated with a higher prevalence of rhinosinusitis and nasal polyps as well as eosinophilia and Aspergillus sensitization. BE+A had similar microbiology but significantly lower severity of disease using the bronchiectasis severity index. Patients with BE+A were at increased risk of exacerbation after adjustment for disease severity and multiple confounders. Inhaled corticosteroid (ICS) use was associated with reduced mortality in patients with BE+A (adjusted hazard ratio 0.78, 95% CI 0.63-0.95) and reduced risk of hospitalization (rate ratio 0.67, 95% CI 0.67-0.86) compared with control subjects without asthma and not receiving ICSs. Conclusions: BE+A was common and was associated with an increased risk of exacerbations and improved outcomes with ICS use. Unexpectedly we identified significantly lower mortality in patients with BE+A

On the quest for selective constraints shaping the expressivity of the genes casting retropseudogenes in human

<p>Abstract</p> <p>Background</p> <p>Pseudogenes, the nonfunctional homologues of functional genes are now coming to light as important resources regarding the study of human protein evolution. Processed pseudogenes arising by reverse transcription and reinsertion can provide molecular record on the dynamics and evolution of genomes. Researches on the progenitors of human processed pseudogenes delved out their highly expressed and evolutionarily conserved characters. They are reported to be short and GC-poor indicating their high efficiency for retrotransposition. In this article we focused on their high expressivity and explored the factors contributing for that and their relevance in the milieu of protein sequence evolution.</p> <p>Results</p> <p>We here, analyzed the high expressivity of these genes configuring processed or retropseudogenes by their immense connectivity in protein-protein interaction network, an inclination towards alternative splicing mechanism, a lower rate of mRNA disintegration and a slower evolutionary rate. While the unusual trend of the upraised disorder in contrast with the high expressivity of the proteins encoded by processed pseudogene ancestors is accredited by a predominance of hub-protein encoding genes, a high propensity of repeat sequence containing genes, elevated protein stability and the functional constraint to perform the transcription regulatory jobs. Linear regression analysis demonstrates mRNA decay rate and protein intrinsic disorder as the influential factors controlling the expressivity of these retropseudogene ancestors while the latter one is found to have the most significant regulatory power.</p> <p>Conclusions</p> <p>Our findings imply that, the affluence of disordered regions elevating the network attachment to be involved in important cellular assignments and the stability in transcriptional level are acting as the prevailing forces behind the high expressivity of the human genes configuring processed pseudogenes.</p