Influence of abutment collar height and implant length on stress distribution in single crowns

Abstract This in silico study evaluated the influence of the abutment collar height and implants length on the biomechanical behavior of morse taper single dental implants with different crown-to-implant ratio. Six virtual models were constructed (S11, M11, L11, S13, M13 and L13) by combining short (S: 2.5 mm), medium (M: 3.5 mm) or long (L: 4.5 mm) abutment collar heights with different implant lengths (11 or 13-mm). An upper central incisor of 11-mm height was constructed on top of each abutment. Each set was positioned in a virtual bone model and exported to analyze mathematically. A 0.60-mm mesh was created after convergence analysis and a 49 N load was applied to the cingulum of the crown at an angle of 45°. Load-generated stress distribution was analyzed in the prosthetic components according to von Mises stress criteria (σvM) and in the cortical and cancellous bone by means of shear stress (εmax). The use of longer collar abutments (L11) increased the stress on the abutment by 250% and resulted in 40% higher stresses on the screw and 92% higher cortical shear stresses compared to short collared abutments (S11). Increasing the implant length produced a slight stress reduction on cortical bone. Cancellous bone was not affected by the crown-to-implant ratio. Longer abutment collars concentrate stresses at the implant level and cortical bone by increasing the crown-to-implant ratio.

Resumo Este estudo avaliou a influência da altura da porção transmucosa do pilar protético com junção cone morse e do comprimento dos implantes no comportamento biomecânico coroas unitárias com diferentes proporção coroa-implante. Seis modelos virtuais (S11, M11, L11, S13, M13 e L13) foram construídos combinando pilares protéticos com transmucoso considerado: curto (S: 2,5 mm), médio (M: 3,5 mm) ou longo (L: 4,5 mm) com diferentes comprimentos de implantes (11 ou 13 mm). Um incisivo central superior de 11 mm de altura foi construído para cada pilar. Cada conjunto foi posicionado em um modelo de osso virtual e exportado para análise matemática. Uma malha de 0,60 mm foi criada após análise de convergência e uma carga de 49 N foi aplicada ao cíngulo da coroa em um ângulo de 45°. A distribuição de estresse gerada por carga foi analisada nos componentes protéticos de acordo com o critério de tensão de von Mises (σvM) e no osso cortical e medular por meio da tensão de cisalhamento (εmax). O uso de pilares com porção transmucosa mais longa (L11) aumentou a tensão no pilar protético em 250%, e resultou em tensões 40% maiores no parafuso e 92% no osso cortical em relação aos pilares com transmucoso curto (S11). O aumento do comprimento do implante produziu uma ligeira redução da tensão de cisalhamento no osso cortical. O osso medular não foi afetado pela relação coroa-implante. Pilares protéticos com porção transmucosa mais longa concentram tensões no implante e no osso cortical, quando a proporção coroa-implante é aumentada.

Survival rate of modern all-ceramic FPDs during an observation period from 2011 to 2016

PURPOSE: In literature, many studies compare survival rates of different types of FPDs. Most of them compared restorations, which originated from one university, but from different clinicians. Data about restoration survival rates by only one experienced dentist are very rare. The aim of this study was to evaluate the survival rate of allceramic FPDs without the blurring effects of different clinicians. MATERIALS AND METHODS: 153 veneeredzirconia FPDs were observed for follow-up. 22 patients received 131 single crowns and 22 bridges. Because of the different bridge lengths, one unit was defined as a restored or replaced tooth. In total, 201 units were included. Only the restorations performed by the same clinician and produced in the same dental laboratory from 2011 to 2016 were included. Considered factors were defined as “type of unit”, “type of abutment”, “intraoral region”, and “vitality”. Modified UHPHS criteria were used for evaluation. Statistical analysis was performed using cox-regression. RESULTS: 189 units (94.0%) showed no kind of failure. 5 chippings (2.4%) could be corrected by intraoral polishing. 4 units (1.9%) exhibited spontaneous decementation. These polishable and recementable restorations are still in clinical use. Chippings or decementations, which lead to total failure, did not occur. One unit was completely fractured (0.5 %). Biological failures (caries, periodontitis or periimplantitis) did not occur. The statistical analysis of the factors did not reveal any significant differences. CONCLUSION: Modern all-ceramic FPDs seem to be an appropriate therapy not only for single restorations but for complex occlusal rehabilitations.

Avaliação do assentamento de coroas totais à base de dissilicato de lítio produzidas por três diferentes fluxos de trabalho: convencional, digital ou parcialmente digital / Fit of lithium dissilicate crowns made by three workflows: conventional, partially digital and totally digital

Este estudo avaliou os assentamentos marginal e interno em 4 áreas predeterminadas de coroas totais à base de dissilicato de lítio produzidas por 3 fluxos de trabalho distintos. Um modelo-mestre de titânio com um preparo para coroa total em um molar foi confeccionado. Foram produzidas 36 coroas totais à base de dissilicato de lítio. As coroas foram divididas em 3 grupos, de acordo com o fluxo de trabalho: Totalmente Convencional (TC): moldagem do modelo-mestre com polieter, vazagem com gesso tipo IV e confecção de 12 coroas (IPS e.max PRESS) no laboratório de prótese; Totalmente Digital (TD): escaneamento do modelo-mestre com a Bluecam™ e usinagem de 12 coroas totais (IPS e.max CAD™) no CEREC 3™; e Parcialmente Digital (PD): moldagem do modelo-mestre com polieter, vazagem com gesso tipo IV, escaneamento do modelo de gesso com a Bluecam™ e usinagem de 12 coroas totais (IPS e.max CAD™) no CEREC 3™. Para a avaliação do assentamento foi utilizada a técnica da réplica, onde a base leve do silicone de adição simulou um cimento. Duas réplicas por coroa total foram confeccionadas, gerando imagens de interfaces vestíbulo-palatal e mesio-distal sob magnificação de 50x. Quatro áreas foram definidas para a avaliação: Abertura Marginal (AM); Chanfro (CH); Parede Axial (PA); e Parede Oclusal (PO). Um software realizou a medição dos valores em toda a área demarcada, gerando aproximadamente 6.000 pontos de avaliação por interface. Os resultados foram estatisticamente analisados por meio dos testes One-Way-Anova e Scheafer's Post-Hoc, com grau de significância estabelecido em 5%. Todas os grupos testados no estudo apresentaram médias de valores clinicamente aceitáveis para os assentamentos marginal e interno. Não houve diferença significativa em AM, CH e PO entre os três grupos testados. Em PA, o grupo TC apresentou valores significativamente maiores do que PD e TD (p = 0,001). Os diferentes fluxos de trabalho, convencional ou digitais, aplicados neste estudo, foram capazes de prover adequados assentamentos marginal e interno, dentro dos valores clínicos estabelecidos para coroas totais à base de porcelana.

The aim of this study was to evaluate the marginal and internal fit of porcelain indirect restorations produced by three distinct workflows in four pre-determined interface areas. A titanium master model - simulating a full crown molar preparation - was built to this study. 36 lithium dissilicate full crowns coverage were produced. The restorations were divided in 3 groups, according to the workflow: Totally Conventional (TC), where a polieter impression of the master model was poured with type IV gypsum, and 12 full crown coverages (IPS e.max PRESS™) were produced in the dental technician; Totally Digital (TD), where the master model was scanned with the Bluecam™ and 12 full crown coverages (IPS e.max CAD™) were milled in the CEREC 3™; Partially Digital (PD), where a polieter impression of the master model was poured with type IV gypsum, with the Bluecam™ scanning the working model and the 12 full crown coverages (IPS e.max CAD™) being milled by the CEREC 3™. The replica technique, where the light body silicone simulate the cement, was used to evaluate the fit of the crowns. Two cross sectioned replicas per crown were obtained, generating images of the bucco-palatal and mesio-distal interfaces under 50x magnification. Four interface areas were choosen to the evaluation: Marginal Opening (AM); Chamfer (CH), Axial Wall (PA); and Occlusal Wall (PO). The hole interface area of each image was evaluated, generating approximately 6.000 points to be rated per interface. Results were statistical analyzed with one-way-Anova and Scheafer's post hoc with a 5% level of significance. All the 3 tested groups showed clinically acceptable mean values for marginal and internal fit. For the areas AM, CH and PO, similar results were found between the 3 groups. For the PA area, TC group showed significantely higher values than PD and TD groups (p = 0,001). The different workflows, conventional or digitals, used in this study were proven capable to present elegible marginal and internal fit, based on the accepted current values for porcelain full coverage crowns.

Influência das desadaptações angulares unilaterais na distribuição de tensões da região peri-implantar de elementos unitários tipo UCLA submetidos a pré-carga e carga axial: estudo in vitro / Influence of the unilateral angular misfit in frameworks made of UCLA on the peri-implant strain distribution, subjected to preload and axial load

Atualmente, os implantes são utilizados em diversos tipos de tratamento na reabilitação oral. Para manutenção da osseointegração, é essencial que o conjunto prótese/implante/osso seja submetido a forças às quais estejam aptos a suportar. Os diferentes tipos de desadaptações das infraestruturas das próteses sobre implantes são fatores que podem contribuir para o aumento das tensões na região peri-implantar. Este estudo teve como objetivo avaliar a influência das desadaptações angulares unilaterais na distribuição de tensões na região periimplantar de pilares tipo UCLA, no momento da pré-carga e carga axial. Infraestruturas de CoCr, confeccionadas utilizando-se pilares tipo UCLA, foram divididas em quatro grupos: Grupo A (adaptado), Grupo B, Grupo C e Grupo D (50, 100 e 200 μm de desadaptação unilateral angular por vestibular, respectivamente). Cada grupo foi representado por quatro infraestruturas (n=4). Quatro implantes (4.1mm/15mm) foram posicionados em uma matriz metálica, onde posteriormente foi vazado o poliuretano (PU), com função de simular o tecido ósseo. Quatro extensômetros (strain gauges) foram posicionados na região vestibular, distal, lingual e mesial de cada implante, para aferir a quantidade de deformação; cada grupo foi posicionado em seu respectivo implante. Foram realizados dois testes: o teste de pré-carga com um torque de 32Ncm e o teste de carga com uma força axial estática de 300N. Cada infraestrutura foi sujeita aos dois testes, por cinco vezes. Para análise estatística dos dados, foram utilizados ANOVA (dois critérios) e o teste de Tukey (p<0,05). Os resultados mostraram que os grupos A e B tiveram menos deformação da região peri-implantar em ambos os testes, quando comparados aos grupos C e D. A estatística também mostrou que o Grupo A apresentou melhor distribuição de tensões em sua região, peri-implantar quando comparado aos outros três grupos (p<0,05). Como conclusões, este estudo mostrou que as desadaptações influem...

Nowadays implants are used in several kinds of oral rehabilitation treatments. For the osseointegration maintenance it is important that crow/implant/bone are subjected to forces which are able to withstand. Different kinds of misfit on the crown frameworks are factors that could lead to an increase of strain around the implanted bone. This study aimed to evaluate the influence of the unilateral angular misfit in frameworks made of UCLA on the peri-implant strain distribution, subjected to preload and axial load. Frameworks made of chrome-cobalt were fabricated on UCLA abutments and divided in 4 groups: Group A (no misfit), Group B, Group C, Group D (50, 100, and 200 of unilateral angular misfit by buccal side, respectively). Each group was represented for 4 frameworks (n=4). Four implants (4.1mm/15mm) were positioned in a metallic matrix which was subsequently poured the polyurethane (PU) to simulate the bone. Four strain gauges were positioned on the buccal, distal, lingual and mesial sides of each implant to assess the amount of strain, each group was connected on its respectively implant. It was performed 2 tests: the preload test with a 32Ncm torque and the load test by applying an axial force of 300N. Each framework was subjected to the both test five times. To the statistics analysis ANOVA (2 ways) and Turkeys test were performed. The results showed that the Groups A and B presented less deformation when compared to Groups C and D. The statistics also showed that the Group A presented better distribution of strain on its peri-implant bone when compared to the other three groups (p<0,05). In conclusion this study showed that misfit had influence on the strain distribution on the peri-implant bone and that strain increased on the Groups C and D which presented higher levels of misfit.

Influência das desadaptações angulares unilaterais na distribuição de tensões da região peri-implantar de elementos unitários tipo UCLA submetidos a pré-carga e carga axial: estudo in vitro / Influence of the unilateral angular misfit in frameworks made of UCLA on the peri-implant strain distribution, subjected to preload and axial load

Atualmente, os implantes são utilizados em diversos tipos de tratamento na reabilitação oral. Para manutenção da osseointegração, é essencial que o conjunto prótese/implante/osso seja submetido a forças às quais estejam aptos a suportar. Os diferentes tipos de desadaptações das infraestruturas das próteses sobre implantes são fatores que podem contribuir para o aumento das tensões na região peri-implantar. Este estudo teve como objetivo avaliar a influência das desadaptações angulares unilaterais na distribuição de tensões na região periimplantar de pilares tipo UCLA, no momento da pré-carga e carga axial. Infraestruturas de CoCr, confeccionadas utilizando-se pilares tipo UCLA, foram divididas em quatro grupos: Grupo A (adaptado), Grupo B, Grupo C e Grupo D (50, 100 e 200 μm de desadaptação unilateral angular por vestibular, respectivamente). Cada grupo foi representado por quatro infraestruturas (n=4). Quatro implantes (4.1mm/15mm) foram posicionados em uma matriz metálica, onde posteriormente foi vazado o poliuretano (PU), com função de simular o tecido ósseo. Quatro extensômetros (strain gauges) foram posicionados na região vestibular, distal, lingual e mesial de cada implante, para aferir a quantidade de deformação; cada grupo foi posicionado em seu respectivo implante. Foram realizados dois testes: o teste de pré-carga com um torque de 32Ncm e o teste de carga com uma força axial estática de 300N. Cada infraestrutura foi sujeita aos dois testes, por cinco vezes. Para análise estatística dos dados, foram utilizados ANOVA (dois critérios) e o teste de Tukey (p<0,05). Os resultados mostraram que os grupos A e B tiveram menos deformação da região peri-implantar em ambos os testes, quando comparados aos grupos C e D. A estatística também mostrou que o Grupo A apresentou melhor distribuição de tensões em sua região, peri-implantar quando comparado aos outros três grupos (p<0,05). Como conclusões, este estudo mostrou que as desadaptações influem...

Nowadays implants are used in several kinds of oral rehabilitation treatments. For the osseointegration maintenance it is important that crow/implant/bone are subjected to forces which are able to withstand. Different kinds of misfit on the crown frameworks are factors that could lead to an increase of strain around the implanted bone. This study aimed to evaluate the influence of the unilateral angular misfit in frameworks made of UCLA on the peri-implant strain distribution, subjected to preload and axial load. Frameworks made of chrome-cobalt were fabricated on UCLA abutments and divided in 4 groups: Group A (no misfit), Group B, Group C, Group D (50, 100, and 200 of unilateral angular misfit by buccal side, respectively). Each group was represented for 4 frameworks (n=4). Four implants (4.1mm/15mm) were positioned in a metallic matrix which was subsequently poured the polyurethane (PU) to simulate the bone. Four strain gauges were positioned on the buccal, distal, lingual and mesial sides of each implant to assess the amount of strain, each group was connected on its respectively implant. It was performed 2 tests: the preload test with a 32Ncm torque and the load test by applying an axial force of 300N. Each framework was subjected to the both test five times. To the statistics analysis ANOVA (2 ways) and Turkeys test were performed. The results showed that the Groups A and B presented less deformation when compared to Groups C and D. The statistics also showed that the Group A presented better distribution of strain on its peri-implant bone when compared to the other three groups (p<0,05). In conclusion this study showed that misfit had influence on the strain distribution on the peri-implant bone and that strain increased on the Groups C and D which presented higher levels of misfit.

Condición periodontal de las prótesis fijas singulares realizadas en la Clínica Odontológica Integral del Adulto de la Universidad Mayor de Temuco / Periodiontal condition of fixed single prostheses made at Integral Adult Dental Clinic of the Universidad Mayor in Temuco

El objetivo de esta investigación fue determinar la condición periodontal en prótesis fijas singulares (PFS) realizadas en la clínica odontológica Integral del Adulto I y II de la Universidad Mayor de Temuco entre los años 2007 y 2009. Se evaluaron 73 PFS mediante un examen clínico, realizadas en 41 pacientes. Se analizaron las variables: edad, sexo, pieza dentaria, año de atención, año académico en que se realizaron las PFS, material de las prótesis fijas; los parámetros periodontales evaluados en este estudio fueron edema y eritema, sangramiento y recesión gingival. La frecuencia de edema y eritema fue de 81 por ciento, el sangramiento lo encontramos en un 77 por ciento y la recesión gingival en un 27 por ciento. Las mujeres presentaron mayores problemas de los tejidos periodontales con un 85 por ciento de edema y eritema y un 81 por ciento de sangramiento. Las PFS realizadas en el 4to año académico presentaron un 55 por ciento de recesión gingival y las realizadas en el 5to año mostraron un 17 por ciento. En relación al año de atención en el que se realizaron las rehabilitaciones, las PFS realizadas en el año 2007 presentaron un 100 por ciento de inflamación, mientras que en los otros años (2008 y 2009) las PFS presentaron menos daño a nivel gingival. Las piezas más afectadas según la ubicación en la boca, fueron las posteriores con un 84 por ciento de edema y eritema. Respecto al material, las PFS que presentaron más problemas de edema y eritema fueron las de metal cerámica con un 82 por ciento. Del total de los 41 pacientes observados, la mayoría estaban satisfechos con su rehabilitación. Finalmente se puede concluir que no existió evidencia estadísticamente significativa para concluir que existe una asociación entre las variables edad, sexo, año de atención y las variables edema y eritema, sangramiento y recesión gingival. En cambio, si se encontró evidencia estadísticamente significativa entre el cuarto y quinto año académico/ durante el tiempo/...

The aim of this study was to determine the periodontal condition in fixed single prostheses made at Integral Adult Dental Clinic I and II of the Universidad Mayor in Temuco, between the years 2007 and 2009. Seventy-three fixed single prostheses were evaluated by clinical examination, made in 41 patients. Variables were analyzed: age, sex, tooth, year of care, year in which the fixed single prostheses were made, fixed single prostheses material; periodontal parameters evaluated in this study were edema and erythema, bleeding and gingival recession. Edema and erythema's frequency were 81 percent, bleeding in 77 percent and gingival recession in 27 percent. Women presented major problems in periodontal tissues with 85 percent of edema and erythema and 81 percent of bleeding. Fixed single prostheses made in 4th year showed 55 percent of gingival recession and the ones that were made in 5th year showed 17 percent. In relation to the year of care in which the rehabilitations were made, the fixed single prostheses made in 2007 showed 100 percent of inflammation, while in the other years (2008 and 2009) the fixed single prostheses showed less damage at gingival level. The most affected teeth according to the location in the mouth were the back ones with 84 percent of edema and erythema. Regarding material, the fixed single prostheses that showed more edema and erythema problems were the metal-ceramics with 82 percent. Of the total of the 41 patients observed, the majority was satisfied with their rehabilitation. Finally we can conclude that there was no statistically significant evidence to conclude that there is an association between the variables age, sex, year of care and the variables edema and erythema, bleeding and gingival recession. In contrast, if found statistically significant evidence between the 4th and 5th year/ during the time/ years in which the fixed single prostheses and the gingival recession were made.

A Feasibility Study On The Application Of The Knitted Glass Fabric Composites To Fixed Prosthodontic Restoration In Dentistry / 대한치과보철학회지

Current dental restorations present a relatively weak resistance to fracture. Owing to their unique mechanical properties, fibre-reinforced polymers are now being considered. Unidirectional or woven continuous fibres, made of glass, polyethylene, carbon or Kevlar, have been evaluated. This study focused on the use of glass fibre knitted fabrics to reinforce acrylate resins, in order to investigate the possibility to construct single crowns as well as three unit bridges. Some points affecting the final composite system were tested: 1) static strength, with focus on the stress transfer under a occlusal contact point; 2) modelling of a three unit bridge; 3) fatigue strength as a posterior three unit bridge material. The study demonstrated that knitted fabric reinforcements are showing an interesting compromise between stiffness, static strength for single crown. For three unit bridge applications in the posterior arch, however, knitted glass fabric reinforcements were not strong enough in fatigue. An additional reinforcement in the posterior arch fixed partial denture design was recommended.