Stress Distribution on Various Implant-Retained Bar Overdentures.

The purpose of this study was to evaluate the effects of various fabrication techniques and materials used in implant-supported mandibular overdentures with a Hader bar attachment over added stress distribution. Three-dimensional geometric solid models, consisting of two implants (3.3 mm × 12 mm) placed at the bone level on both mandibular canine regions and a Hader bar structure, were prepared. Model 1 simulated a bar retentive system made from Titanium Grade 5 material by Computer Numerical Control (CNC) milling technique without using any converting adapter/multi-unit element on the implants, while Model 2 simulated the same configuration, but with converting adapters on the implants. Model 3 simulated a bar retentive system made from Cobalt-Chromium material, made by using conventional casting technique with converting adapters on the implants. Static loads of 100 Newton were applied on test models from horizontal, vertical and oblique directions. ANSYS R15.0 Workbench Software was used to compare Von Mises stress distribution and minimum/maximum principal stress values, and the results were evaluated by using Finite Element Analysis method. As a result, the highest stress distribution values under static loading in three different directions were obtained in Model 1. Stress was observed intensely around the necks of the implants and the surrounding cortical bone areas in all models. In scope of the results obtained, using converting adapters on implants has been considered to decrease transmission of forces onto implants and surrounding bone structures, thus providing a better stress distribution. It has also been observed that the type of material used for bar fabrication has no significant influence on stress values in those models where converting adapters were used

Princípios atuais de fixação de próteses totais removíveis sobre implantes

Dissertação para obtenção do grau de Mestre no Instituto Universitário Egas MonizAo longo dos últimos anos, as mudanças demográficas e epidemiológicas, bem como os avanços na medicina, levaram a um aumento significativo da qualidade e esperança média de vida. No entanto, a perda dentária mantém-se um problema atual e afeta sobretudo a população geriátrica. Fatores sistémicos do indivíduo e aspetos socioeconómicos são determinantes para o risco de vir a sofrer desta condição. A perda de dentes sem substituição por prótese dentária leva a uma grave perda da função mastigatória e ao desenvolvimento de doenças relacionadas. A falta de dentes e consequente incapacidade de comer adequadamente resultam em mudanças na aparência, problemas de comunicação e um complexo de reações psicossomáticas, que levam frequentemente ao isolamento social. O edentulismo é definido como a perda completa de todos os dentes. O tratamento protético de pacientes edêntulos tem sido desenvolvido desde o início da Medicina Dentária com progressos consideráveis ao longo do tempo. Ainda assim, continua a ser um desafio para o dentista, que tem de satisfazer as expectativas do paciente. No edentulismo, a atrofia óssea dos maxilares torna impossível uma fixação e estabilidade suficientes. Contudo, graças aos avanços na área da implantologia é possível dar aos pacientes desdentados totais próteses totais removíveis de qualidade: com boa estabilidade, capazes de melhorar significativamente a sua função mastigatória, capacidade fonética, aparência física, autoestima e, evidentemente, a sua qualidade de vida. A presente monografia tem por objetivo descrever as diversas formas de reabilitação de desdentados totais com recurso a próteses totais removíveis sobre implantes: as sobredentaduras ou overdentures, bem como os attachments e sistemas retentivos associados às mesmas.Over the past few years, demographic and epidemiological changes, as well as advances in medicine, have led to a significant increase in quality of life and average life expectancy. However, tooth loss remains a current problem and affects the geriatric population. Systemic factors of the individual and socioeconomic aspects are determinants of the risk of suffering from this condition. Tooth loss without replacement by a dental prosthesis leads to a severe loss of chewing function and the development of related diseases. The lack of teeth and consequent inability to eat properly result in changes in appearance, communication problems, and a complex of psychosomatic reactions, often leading to social isolation. Edentulism is defined as the complete loss of all teeth. The prosthetic treatment of edentulous patients has been developed since the beginning of dentistry with considerable progress over time. Still, it remains a challenge for the dentist, who must meet the patient's expectations. In edentulism, bone atrophy of the jaws makes sufficient fixation and stability impossible. However, thanks to advances in implantology it is possible to give edentulous patients quality removable full dentures: with good stability, capable of significantly improving their chewing function, phonetic ability, physical appearance, self-esteem and, of course, their quality of life. This monograph aims to describe the various forms of rehabilitation of edentulous patients using removable full dentures on implants: overdentures, as well as the attachments and retention systems associated with them.Au cours des dernières années, les changements démographiques et épidémiologiques mondiaux, l'évolution des connaissances scientifiques et les progrès de la médecine ont conduit à une augmentation significative de l'espérance de vie. Cependant, la perte de dents, partielle ou totale, reste un problème actuel et touche principalement la population gériatrique. Les facteurs systémiques de l'individu et les aspects socio-économiques sont des déterminants du risque de subir une perte de dents. La perte d'une dent sans remplacement par une prothèse dentaire entraîne une grave perte de la fonction masticatoire et le développement de maladies associées. L'absence de dents et l'incapacité qui en résulte de s'alimenter correctement entraînent des changements d'apparence, des problèmes de communication et un ensemble de réactions psychosomatiques, conduisant souvent à l'isolement social. L'édentulisme est défini comme la perte complète de toutes les dents. Le traitement prothétique des patients présentant une perte complète de leurs dents a été développé depuis les débuts de la dentisterie et des progrès considérables ont été réalisés au fil des ans. La réhabilitation des personnes totalement édentées reste cependant un défi pour le dentiste. Les exigences fonctionnelles et esthétiques du patient doivent être satisfaites. Chez les patients édentés, il est impossible d'obtenir une fixation et une stabilité satisfaisantes avec les prothèses complètes conventionnelles. Grâce aux progrès de l'implantologie, il est possible de fournir à ces patients des prothèses totales amovibles de qualité : d'une bonne stabilité, capables d'améliorer significativement leur fonction masticatoire, leur capacité phonétique, leur apparence physique, leur estime de soi et, évidemment, leur qualité de vie. Cette monographie a pour objectif de décrire les différentes formes de réhabilitation des patients édentés à l'aide de prothèses amovibles complètes sur implants : overdentures, ainsi que les attachements et systèmes de rétention qui leur sont associés