Photoelasticity in Dentistry: a literature review

Introduction and Objective: Photoelasticity consists of an experimental technique of stress analysis. This technique is very used in most different areas including Dentistry. This literature review presents the several applications of photoelastic technique in Dentistry as well as its advantages and disadvantages. Literature review: Based on this method of analysis, it is possible the verification of the stress distribution and deformation in structures with complex geometry as maxilla and mandible. It can be used to evaluate the distribution of stress on several types of prosthesis as removable partial denture systems with different retention systems, conventional implant prosthesis, overdentures and Brånemark protocols. Moreover, photoelasticity can be used to assess the stress generated by various orthodontic movements, different orthodontic systems and different materials (orthodontic wires). In addition, it is used to analyze different defects of maxillectomy, splint types on traumatized tooth and post-core restoration methods. This technique can also be used to assess dental instruments such as evaluation of different designs of periodontal probe. Conclusion: The photoelastic analysis has been a technique of great importance in health area studies, more specifically in Dentistry. Based on this method of analysis, it is possible to measure the stress distribution and deformation in structures with complex geometry as maxilla and mandible.

Comportamento biomecânico do sistema prótese/implante em região anterior de maxila: análise pelo método de ciclagem mecânica / Mechanical behavior of prostheses / implant system in the anterior region of maxilla: analysis by the method of cycling mechanics

Introdução : O adequado posicionamento tridimensional dos implantes é indispensável para garantir a previsibilidade no tratamento com implantes dentários. Objetivo : Analisar comparativamente o comportamento mecânico do sistema prótese/implante em região anterior de maxila, diferindo os sistemas de encaixe e posicionamento dos implantes. Material e Método : Utilizando um modelo prototipado de maxila, as situações estudadas foram: Grupo IC - implantes nos incisivos centrais e cantilever nos incisivos laterais; Grupo IL - implantes nos incisivos laterais e pônticos nos incisivos centrais; Grupo ICIL - implantes no incisivo central e no incisivo lateral, intercalados com elementos suspensos. Para cada situação estudada, foram utilizadas as três conexões protéticas: hexágono externo, hexágono interno e cone-Morse. O ensaio de ciclagem mecânica foi realizado com a aplicação de 100 N de carga e frequência de 15 Hz no cíngulo dos incisivos a 45° com o longo eixo do dente, para simular o movimento mastigatório. Resultado : No ensaio de ciclagem mecânica, todos os modelos de todos os grupos com os três tipos de conexões protéticas atingiram um milhão de ciclos sem que ocorresse ruptura do parafuso, do componente protético ou da estrutura metálica. Conclusão : Com a metodologia e as condições empregadas, pode-se concluir que o comportamento mecânico das reabilitações implantossuportadas foi semelhante para os diferentes posicionamentos dos implantes e diferentes conexões protéticas. .

Introduction: The adequate three-dimensional positioning of implants is essential to ensure predictability in dental implant treatment. Purpose : Was to comparatively evaluate the mechanical behavior of the system prosthesis/implant in the anterior maxilla, differing the prosthetic connection and the placement of implants. Material and Method: By a maxilla prototyped model the situations were studied: Group IC- implants in the central incisor positions and cantilevers in the lateral incisor positions; Group IL - implants in the lateral incisor positions and pontics in the central incisor positions; Group ICIL one implant in a lateral and one in a central incisor position, with a pontic and a cantilever in the other positions. For each situations were used the prosthetic connections, external hexagon, internal hexagon and Morse-taper. In fatigue test was applied load 100N of frequency 15Hz in the incisors cingulum 45° to the long axis of the tooth to simulate a masticatory movement. Result: After the fatigue test all models of all groups with all three types of connections prosthetic reached 1 million cycles without rupture occurred screw, prosthetic component or metallic structure. Conclusion: According to methodology and conditions studied, can be concluded that the mechanical behavior of the implant-supported rehabilitation was similar to the different positions of the dental implants and the different prosthetic connections. .

Mechanical behavior of dental implants in different positions in the rehabilitation of the anterior maxilla.

STATEMENT OF PROBLEM: In dental rehabilitations that involve implants, the number of implants is sometimes smaller than the number of lost teeth. This fact can affect the biomechanical behavior and success of the implants. PURPOSE: The purpose of this study was to investigate the mechanical behavior of different implant positions in the rehabilitation of the anterior maxilla. MATERIAL AND METHODS: Three-dimensional models of the maxilla were created based on computed tomography images for 3 different anterior prosthetic rehabilitations. In group IL, the implants were placed in the lateral incisor positions with pontics in the central incisor positions; in group IC, the implants were in the central incisor positions with cantilevers in the lateral incisor positions; and, in group ILIC, one implant was in a lateral incisor position and one was in a central incisor position, with a pontic and a cantilever in the remaining positions. A 150 N load was distributed and applied at the center of the palatal surface of each tooth at a 45-degree angle to the long axis of the tooth. The resulting stress-strain distribution was analyzed for each group. RESULTS: The lowest displacement of the prosthetic structure was observed in group IC, although the same group exhibited the largest displacement of the bone tissue. In the bone tissue, the von Mises stress was mainly observed in the cortical bone in all groups. The maximum value of the von Mises stress shown in the cortical tissue was 35 MPa in the implant that neighbors the cantilever in group ILIC. The maximum von Mises stress in the trabecular bone was 3.5 MPa. CONCLUSION: The prosthetic configuration of group IC limited the displacement of the prosthetic structure but led to greater displacement of the bone structure. The use of a cantilever increased the stress concentration in the implant and in the bone structure adjacent to the cantilever under the conditions studied here.

Comportamento mecânico de sistemas prótese/implante em região dos elementos finitos e interferometria holográfica / Mechanical behavior of prosthesis / implant systems in the anterior maxilla: analysis by finite element method and holographic interferometry

A proposta deste estudo foi analisar, por meio do método de elementos finitos (MEF), o comportamento mecânico das estruturas envolvidas em uma reabilitação implanto suportada de 4 elementos na região anterior de maxila, utilizando apenas 2 implantes, variando os posicionamentos dos implantes e o tipo de conexão protética (hexágono externo, hexágono interno e cone-Morse) e ainda validar metodologia de análise computacional por meio da interferometria holográfica, uma técnica experimental. Modelos tridimensionais baseados em um banco de tomografias computadorizadas foram criados para todas as situações estudadas (Implantes nos Incisivos Laterais - IL; Implantes nos Incisivos Centrais - IC e Implante no Incisivo Central e Incisivo Lateral - ILIC). Uma carga equivalente à 150N foi aplicada a 45° na região de cíngulo de cada elemento dentário. Para a validação da metodologia de elementos finitos por meio da interferometria holográfica, criou-se um modelo prototipado com as mesmas situações estudadas e comparou-se os deslocamentos direcionais resultantes da aplicação de 3 intensidades de força. Como resultado foi observado: o menor deslocamento da estrutura protética e maior deslocamento na estrutura óssea no grupo IC. No tecido ósseo, a tensão de von Misses localiza-se predominantemente na região cortical. O valor máximo de tensão de von Misses foi observado no implante vizinho ao cantilever no grupo ILIC. Na conexão cone Morse, o parafuso protético mostrou metade da tensão de von Misses em relação a conexão hexágono interno e hexágono externo. Comparando-se os deslocamentos direcionais nas duas metodologias, verificou-se que havia uma correlação positiva entre os resultados, porém os valores obtidos experimentalmente eram superiores aos do modelo computacional. Pode-se concluir...

The purpose of this study was to analyze, by finite element method (FEM), the mechanical behavior of structures involved in an implant supported rehabilitation of 4 elements in the anterior maxilla, using only 2 implants, varying the placements of the implants and prosthetic connection types (external hexagon, internal hexagon and Morse taper) Moreover to validate the methodology of MEF by holographic interferometry, an experimental technique. Three-dimensional models based on a database CT scans were created for all situations studied (Implants in Lateral Incisors - IL; Implants in Central Incisors IC and Implant in Central e Lateral Incisor - ILIC). An equivalent load of150N was applied at 45° in the cingulum of each tooth. To validate the finite element method by Holographic Interferometry, a prototyped model was created with the same situations studied and compared the directional displacements, resulting from the application of the 3 intensities of force. As results it was observed: the lowest prosthetic displacement structure and greater displacement in the bone structure in the IC group. In bone tissue, the von Mises stress is located predominantly in the cortical region. The maximum value of von Mises stress was observed in the implant neighboring to cantilever in the group ILIC. In Morse taper connection, the prosthetic screw showed half the von Misses stress in relation to internal and external hexagon connection. Comparing the directional displacement in both methodologies, an positive correlation between the results was found, although the experimentally values obtained were higher than those of the computational model. It can be concluded that the placement of implants and prosthetic connection type have influence in the intensity and distribution of stress/strain on the implant-supported rehabilitation of anterior...

Comportamento mecânico de sistemas prótese/implante em região anterior de maxila: análise pelo método dos elementos finitos e interferometria holográfica / Mechanical behavior of prosthesis/implant systems in the anterior maxilla: analysis by finite element method and holographic interferometry

A proposta deste estudo foi analisar, por meio do método de elementos finitos (MEF), o comportamento mecânico das estruturas envolvidas em uma reabilitação implanto suportada de 4 elementos na região anterior de maxila, utilizando apenas 2 implantes, variando os posicionamentos dos implantes e o tipo de conexão protética (hexágono externo, hexágono interno e cone-Morse) e ainda validar metodologia de análise computacional por meio da interferometria holográfica, uma técnica experimental. Modelos tridimensionais baseados em um banco de tomografias computadorizadas foram criados para todas as situações estudadas (Implantes nos Incisivos Laterais - IL; Implantes nos Incisivos Centrais - IC e Implante no Incisivo Central e Incisivo Lateral - ILIC). Uma carga equivalente à 150N foi aplicada a 45° na região de cíngulo de cada elemento dentário. Para a validação da metodologia de elementos finitos por meio da interferometria holográfica, criou-se um modelo prototipado com as mesmas situações estudadas e comparou-se os deslocamentos direcionais resultantes da aplicação de 3 intensidades de força. Como resultado foi observado: o menor deslocamento da estrutura protética e maior deslocamento na estrutura óssea no grupo IC. No tecido ósseo, a tensão de von Misses localiza-se predominantemente na região cortical. O valor máximo de tensão de von Misses foi observado no implante vizinho ao cantilever no grupo ILIC. Na conexão cone Morse, o parafuso protético mostrou metade da tensão de von Misses em relação a conexão hexágono interno e hexágono externo. Comparando-se os deslocamentos direcionais nas duas metodologias, verificou-se que havia uma correlação positiva entre os resultados, porém os valores obtidos experimentalmente eram superiores aos do modelo computacional. Pode-se concluir que o posicionamento dos implantes e o tipo de conexão protética em reabilitação anterior de maxila influenciam a distribuição e intensidade de tensão/deformação nas estruturas da prótese implanto-suportada e ainda que o MEF pode ser usado como uma eficiente técnica para a análise de tensão, deformação e deslocamento quando utilizada com modelos validados experimentalmente

The purpose of this study was to analyze, by finite element method (FEM), the mechanical behavior of structures involved in an implant supported rehabilitation of 4 elements in the anterior maxilla, using only 2 implants, varying the placements of the implants and prosthetic connection types (external hexagon, internal hexagon and Morse taper) Moreover to validate the methodology of MEF by holographic interferometry, an experimental technique. Three-dimensional models based on a database CT scans were created for all situations studied (Implants in Lateral Incisors - IL; Implants in Central Incisors IC and Implant in Central e Lateral Incisor - ILIC). An equivalent load of150N was applied at 45° in the cingulum of each tooth. To validate the finite element method by Holographic Interferometry, a prototyped model was created with the same situations studied and compared the directional displacements, resulting from the application of the 3 intensities of force. As results it was observed: the lowest prosthetic displacement structure and greater displacement in the bone structure in the IC group. In bone tissue, the von Mises stress is located predominantly in the cortical region. The maximum value of von Mises stress was observed in the implant neighboring to cantilever in the group ILIC. In Morse taper connection, the prosthetic screw showed half the von Misses stress in relation to internal and external hexagon connection. Comparing the directional displacement in both methodologies, an positive correlation between the results was found, although the experimentally values obtained were higher than those of the computational model. It can be concluded that the placement of implants and prosthetic connection type have influence in the intensity and distribution of stress/strain on the implant-supported rehabilitation of anterior maxilla and moreover the FEM can be used as an efficient technique for analysis of stress, strain and displacement when used with experimentally validated models

Reabilitação implantossuportada da região anterior de maxila: relato de caso / Implant supported rehabilitation of the anterior maxilla: case report

Para reabilitação bucal de elementos dentários perdidos, cada vez mais tem se utilizado a reabilitação implantossuportada. Porém, o paciente pode apresentar condições que limitam a condição ideal para o adequado posicionamento tridimensional dos implantes. Algumas dessas condições são a quantidade, a qualidade e o volume ósseo em rebordo maxilar anterior. O enxerto ósseo autógeno é, atualmente, a melhor opção para reconstrução óssea em espessura na região anterior de maxila. Este artigo descreve a reabilitação de um caso clínico de ausência dos incisivos maxilares, cujo tratamento consistiu de reconstrução em espessura com enxerto ósseo autógeno, instalação de dois implantes e reabilitação final implantossuportada

Oral rehabilitation of teeth lost, has been increasingly used the implant-supported rehabilitation. However, the patient may present with conditions that limit an appropriate three-dimensional positioning of the implants. Some of these conditions are quantity, quality and bone volume in the anterior maxillary ridge. The autogenous bone graft is currently the best choice to fill thickness in the anterior maxilla. This article describes the rehabilitation of a clinical case of absence of maxillary incisors, whose treatment consisted on reconstruction with autogenous bone graft in thickness, installation of two implants and implant-supported final rehabilitation

Fatigue and fluoride corrosion on Streptococcus mutans adherence to titanium-based implant/component surfaces.

PURPOSE: The influence of fatigue and the fluoride ion corrosion process on Streptococcus mutans adherence to commercially pure Titanium (Cp Ti) implant/component set surfaces were studied. MATERIALS AND METHODS: Thirty Nobel implants and 30 Neodent implants were used. Each commercial brand was divided into three groups. Group A: control, Group B: sets submitted to fatigue (10(5) cycles, 15 Hz, 150 N), and Group C: sets submitted to fluoride (1500 ppm, pH 5.5) and fatigue, simulating a mean use of 5 years in the oral medium. Afterward, the sets were contaminated with standard strains of S. mutans (NTCC 1023) and analyzed by scanning electronic microscopy (SEM) and colony-forming unit counts (CFU/mL). RESULTS: By SEM, bacterial adherence was verified only in group C in both brands. By CFU/mL counts, S. mutans was statistically higher in both brands in group C than in groups A and B (p < 0.05, ANOVA). CONCLUSION: The process of corrosion by fluoride ions on Cp Ti implant/component sets allowed greater S. mutans adherence than in the absence of corrosion and with the fatigue process in isolation.

Influence of a fluoridated medium with different pHs on commercially pure titanium-based implants.

PURPOSE: The objective of this study was to assess the influence of a fluoride medium with different pHs on the corrosion resistance of three commercially pure titanium-based dental implant commercial brands, under scanning electron microscopy (SEM) and EDS. MATERIALS AND METHODS: Forty-two dental implants, from three commercial brands, were used. Five years of regular use of mouth rinsing, with NaF 1500 ppm content and two different pHs, were simulated by immersing the specimens into that medium for 184 hours. RESULTS: SEM and EDS analyses demonstrated no evidence of corrosion on the specimens' surfaces after being submitted to fluoride ions or incorporation of fluoride ions to the set surface. CONCLUSION: It was possible to conclude that both the fluoride concentration and the pH of the solutions did not exert any influence upon implant corrosion resistance.

Avaliação da adesão bacteriana em titânio revisão de literatura / Evaluatíon of bacterial adhesion to titanium - Literature review

O estudo da adesão e colonização bacteriana sobre o titânio é de grande importância, pois são fatores principais na patogenia de infecções em biomateriais. A adesão e colonização bacteriana podem variar de acordo com o biomaterial, tipo de microrganismo, fase de crescimento e propriedades superficiais dos materiais. A rugosidade de superfícies sólidas intraorais também tem uma influência na adesão bacteriana. Regiões com uma alta rugosidade de superfícies acumulam e retém mais placa bacteriana. A rugosidade de implantes dentais à base de Ti c.p. pode ser alterada por meio de corrosão por fluoretos.