1,720,962 research outputs found
A Procedure for Designing Custom-Made Implants for Forehead Augmentation in People Suffering from Apert Syndrome
Full text linkThis paper presents a methodological procedure, based on the anatomical reconstruction and constrained deformation, to design custom-made implants for forehead augmentation in people affected by Apert syndrome, experiencing a frontal bone deficiency. According to the anthropometric theory, a cranial landmarks identification procedure was applied to retrieve, from a repository, a healthy skull, used as reference geometry for implant modelling. Then, using constrained deformation and free-form modelling techniques, it was possible to design a patient-specific implant. At last, the implant was realised using a custom mould, specially designed according to the patient’s needs to provide an accurate fit of the defect site. The design procedure was tested on a patient suffering from Apert syndrome. Three implants were virtually modelled and 3D-printed for pre-surgical evaluation. Their shapes were 3D compared with a reference one (handcrafted by a surgeon) to test the accuracy. Deviations are negligible, and the customised implant fulfilled the surgeon’s requirements
HoloLens 2 for Maxillofacial Surgery: A Preliminary Study
No full textSince custom-made 3D printed surgical guides for maxillofacial surgery are usually expensive, Augmented Reality (AR) can be efficiently employed to overcome the high costs. The proposed work aims to develop and test an AR application for different maxillofacial surgeries. The application consists in overlaying the cutting lines on the patient’s mandible to guide the clinician during the procedure. It has been realized in Unity and preliminary tested with HoloLens 2 and a 3D printed mandible. Seven participants performed two consecutive trials. The mandible with the obtained surgical lines has been scanned after each test to digitally reconstruct the traced lines and compare them with the surgical lines previously designed. The results allowed the preliminary analysis of the developed AR system’s accuracy and precision. Mean distances from the designed surgical guides showed good accuracy for the genioplasty (deviation error around 1.03 mm) and orthognathic surgery (deviation error around 1.27 mm), suggesting the applicability of HoloLens 2 for these kinds of surgery. On the contrary, the application was not suitable for the mandibular angle osteotomy (deviation error over 2.50 mm)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A finite element analysis for evaluating mandibular advancement devices
No full textObstructive sleep apnoea (OSA) is a disorder characterised by complete or partial occlusion of the upper airway during sleep. Muscles relax during sleeping and collapse into the airway, closing the throat and prohibiting air flowing into the lungs. Different solutions have been adopted to manage the pathology to improve the life quality of affected patients. Mandibular advancement devices (MADs) are proven to be a compliant and successful therapy in the forward repositioning of the mandible to increase the upper airway volume. However, this method has some long-term adverse events that may affect the teeth and periodontal ligaments. This paper presents a finite element model to evaluate the MADs effects (displacement and stress) on teeth and periodontal ligaments, by varying the design, the point of application of the force and the material. The modelled bodies have been reconstructed through a Reverse Engineering approach and computer-aided design tools starting from tomographic images of anatomic bodies and from laser scans of a physical MAD. The results suggest that a central connection mechanism could affect mostly the anterior teeth. In contrast, a lateral connection mechanism provides a more uniform distribution of the load on teeth
A procedure for analyzing mandible roto-translation induced by mandibular advancement devices
Full text linkBackground: Sleep-Related Breathing Disorders are characterized by repeated episodes of complete or partial obstruction of the upper airway during sleep. Mandibular advancement devices represent a non-invasive treatment in reducing the number of respiratory events and in decreasing symptoms. The advancement extent of these devices is responsible for the mandibular roto-translation and its effects on the temporomandibular joint. Methods: This study defined a systematic method to assess the mandible roto translation that is caused by MADs according to a scan-to-CAD approach. Starting from a closed mouth position and simulating the oral appliance at different settings it was possible to define a local reference system that is useful for the evaluation of the mandibular roto-translation. This latter was then applied to evaluate the movements of the condyle and the mandibular dental arch. Results: MAD1 resulted in a reduced mouth opening and protrusion, while MAD2 enabled a higher degree of motion of the mandible useful for patients who need an important protrusion. Conclusions: The two devices present different dynamics. Results that are achievable employing this method can be directly used by practitioners in comparing MADs, as well as by researchers in evaluating MADs effects
Effects of Oral Appliances for Obstructive Sleep Apnoea in Reduced Periodontium: A Finite Element Analysis
Full text linkBackground and objective: In the literature, no studies correlate the effects of mandibular advancement devices (MADs) with different titration systems to periodontitis. Through a finite element analysis (FEA), this study investigates the effects generated on periodontal ligaments (PDLs) and teeth by four commercial MADs in periodontal health and with 15% bone resorption. Methods: Four MADs (Somnodent FlexTM, Somnodent AvantTM, OrthoapneaTM, and HerbstTM) were digitalised starting from the impressions of a patient's dental arches. A force of 11.18 N, representing an advancement of 9.5 mm, was applied, and a FEA was subsequently performed. After measuring the stresses and displacements on the PDLs and teeth in healthy periodontal conditions, the vertical dimension of the alveolar bone was reduced by 15%, and measurements were repeated. Results: In terms of PDL stress, HerbstTM is the device which guarantees a more uniform increment in case of the first stage of periodontitis (+7% for mandibular and maxillary PDLs compared to the healthy condition). For SomnodentTM devices, the PDLs stress increment is almost null for mandibular PDLs but much higher than HerbstTM for maxillary PDLs (+17% and +21% for FlexTM and AvantTM). OrthoapneaTM determines a PDL stress augmentation between the other devices (+16% and +7%, respectively, for maxillary and mandibular PDLs). Concerning teeth movement, HerbstTM and OrthoapneaTM determine a lower and more uniform displacement than Somnodent devices. Conclusions: The stress distribution and teeth displacement are strictly related to MAD geometry. Since its minor effects on teeth and PDLs, the HerbstTM could be more appropriate in patients with periodontitis
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Evaluation of Mandibular Advancement Devices in Patients Suffering from Obstructive Sleep Apnea and Periodontitis
No full textThe Obstructive Sleep Apnea Syndrome (OSA) concerns episodes of complete or partial obstruction of the upper airway. Mandibular Advancement Device (MAD) is one of the most used systems for treating this syndrome. Clinicians frequently observe a combination of OSA and periodontitis. There is no research aiming to evaluate how periodontitis staging affects the overall mandibular and maxillary dental arches in the literature. Furthermore, no one has studied the combination between OSA and periodontitis and the effects of MADs on the patients in this condition. This paper aims to develop a numerical simulation approach based on FEM and evaluate the consequences (displacement and stress fields) of the periodontitis staging on PDL and teeth of patients suffering from OSA and treated with MADs. Simulations have been performed for evaluating Stage I of periodontitis. Results highlight a correlation between bone resorption and teeth displacement and periodontal ligaments stress (the higher the bone resorption, the higher the stress and displacement)
- …
