Effect of Antirotational Two-Piece Titanium Base on the Vertical Misfit, Fatigue Behavior, Stress Concentration, and Fracture Load of Implant-Supported Zirconia Crowns.

This study investigated the effects of antirotational titanium bases on the mechanical behavior of CAD/CAM titanium bases used for implant-supported prostheses. The aim was to assess the impact on the marginal fit, fatigue behavior, stress concentration, and fracture load of implant-supported CAD/CAM zirconia crowns. Forty titanium implants were divided into two groups: those with antirotational titanium bases (ARs) and those with rotational titanium bases (RTs). Torque loosening and vertical misfit were evaluated before and after cyclic fatigue testing (200 N, 2 Hz, 2 × 106 cycles). Fracture resistance was assessed using a universal testing machine (1 mm/min, 1000 kgf), and failed specimens were examined with microscopy. Three-dimensional models were created, and FEA was used to calculate stress. Statistical analysis was performed on the in vitro test data using two-way analysis of variance and Tukey's test (α = 0.5). Results show that the presence of an antirotational feature between the implant and titanium base reduced preload loss and stress concentration compared to rotational titanium bases. However, there were no differences in vertical misfit and resistance to compressive load.

Biomechanics of implant-supported restorations / Biomecânica das restaurações implantossuportadas

The rehabilitation of patients with dental implant-supported restorations is an ideal treatment option in contemporary dentistry. The aim of this review was to compile and to demonstrate the mechanical response during loading condition, on the stress distributions of implant-supported prostheses. The findings show that the majority of stresses were concentrated in the cervical region of the implant/abutment interface and that they can be affected by several clinical parameters and loading conditions. Finally, the final prosthetic design should combine superior mechanical response, long-term survival rate and allow patient satisfaction. (AU)

A reabilitação de pacientes com restaurações implanto-suportadas é uma opção de tratamento ideal na odontologia contemporânea. O objetivo desta revisão foi compilar e demonstrar a resposta mecânica durante a aplicação de carga, na distribuição de tensão de próteses implanto-suportadas. Os achados mostram que a maioria das tensões se concentram na região cervical da interface implante/pilar e pode ser afetada por diversos parâmetros clínicos e condições de carregamento. Por fim, o desenho protético final deve combinar uma melhor resposta mecânica, taxa de sobrevida a longo prazo e permitir a satisfação do paciente. (AU)

Torque Maintenance Capacity, Vertical Misfit, Load to Failure, and Stress Concentration of Zirconia Restorations Cemented or Notched to Titanium Bases.

PURPOSE: Different titanium bases for implant-supported prostheses can present different mechanical behavior. The goal of this study was to evaluate the torque before and after fatigue, the load to failure, and stress concentration of zirconia restorations cemented or notched to a titanium base. MATERIALS AND METHODS: Forty implants were included in polyurethane cylinders and divided into two groups: zirconia restoration cemented on a titanium base and zirconia restoration notched on a titanium base. The specimens had their torque loosening and vertical misfit evaluated before and after cyclic fatigue (200 N/2 Hz/2 × 106 cycles/37°C). Load to failure was evaluated in a universal testing machine (1 mm/min, 1,000 kgf). Failures were evaluated by scanning electron microscopy. Three-dimensional models were created, and the stress concentration was calculated using the finite element method. Data from the in vitro tests were submitted to two-way analysis of variance and Tukey test (α = .5). RESULTS: The cemented restorations presented less torque loosening (19.79 to 15.95 Ncm), lower vertical misfit (3.7 to 10.5 µm), lower stress concentration in the restoration (88.2 to 99.8 MPa), and higher fracture load (451.3 to 390.8 N) than notched restorations. CONCLUSION: The presence of a cement layer between the restoration and titanium base reduced the susceptibility to abutment screw loosening, improved the resistance to compressive load, and reduced the stress concentration in the restoration.

Lithium Disilicate Crown, Zirconia Hybrid Abutment and Platform Switching to Improve the Esthetics in Anterior Region: A Case Report.

The hybrid abutment emerged as an alternative to maintain a stable and favorable volume of peri-implant tissue; it is composed of a mesostructure in ceramic and a metallic connection, which can be machined according to the peri-implant emergence profile. This case report presented the clinical steps for a dental implant with immediate provisional restoration, followed by the installation of implant-supported all-ceramic crowns with zirconia abutment and platform switching. A 40-year-old male patient was rehabilitated with an implant-supported ceramic crown in the region of element 11 and a ceramic veneer was cemented on the upper right central incisor. To do so, an atraumatic extraction of the upper left central incisor was performed followed by implant placement and immediate loading. In this case, a zirconia hybrid abutment was used with a metallic link in the cervical region with a concave platform switching base. This association of clinical steps enabled improving the aesthetics in the anterior dental region.

Comportamento biomecânico das diferentes conexões entre restaurações monolíticas de zircônia e bases de titânio em próteses implanto-suportadas / Torque maintenance capacity, vertical misfit, load to failure and stress concentration in zirconia restorations cemented or notched to titanium bases

Este estudo avaliou a eficiência da pré-carga antes e após fadiga, desajuste vertical, carga para fratura e a concentração de tensões em restaurações de zircônia cimentadas ou acopladas a uma base de titânio (TB). Para isto, quarenta implantes foram incluídos em cilindros de polióxido de metileno (POM-DelrinDupont) e separados em dois grupos: restauração de zircônia cimentada em um TB ou acoplada em um TB experimental. Os corpos de prova tiveram o torque e o desajuste vertical avaliados antes e após a fadiga cíclica (200 N / 2 Hz / 2 x 106 ciclos / 37 °C). A carga até a fratura foi calculada em uma máquina universal de ensaios (1 mm / min, 1000 kgf) e as falhas foram avaliadas por estereomicroscopia e microscopia eletrônica de varredura. Modelos tridimensionais foram criados baseados na geometria dos espécimes laboratoriais e a concentração de tensão calculada pelo método dos elementos finitos. Os dados dos testes in vitro foram submetidos à análise de variância dois fatores e teste de Tukey (α = 0,5). As restaurações cimentadas apresentaram menor perda de torque (19,79 N.cm), menor desajuste vertical (3,77 µm), menor concentração de tensão na restauração (88,2 MPa) e maior carga de fratura (451,3 N) do que as restaurações acopladas (15,95 N.cm, 10,51 µm, 99,8 MPa e 390,8 N, respectivamente). Conclusão: A presença de uma camada de cimento entre a restauração e a base de titânio reduziu a suscetibilidade ao afrouxamento do parafuso do pilar, melhorou a resistência à carga compressiva e reduziu a concentração de tensão na restauração(AU)

The goal of this study was to evaluate the torque and vertical misfit before and after fatigue, the load to failure and the stress concentration of zirconia restorations cemented or notched to a titanium base (TB). Forty implants were included in Acetal Polyoxymethylene (POM-Delrin-Dupont) cylinders and divided in two groups: zirconia restoration cemented on a TB and zirconia restoration notched on an experimental TB. The specimens had their torque loosening and vertical misfit evaluated before and after cyclic fatigue (200 N / 2 Hz/ 2 x 106 cycles /37 °C). Load to failure was calculated in an universal testing machine (1 mm/min, 1000 kgf) and failures were evaluated by optical microscopy and scanning electron microscopy. Three-dimensional models were created based in the in vitro geometries and the stress concentration calculated using the finite element method. Data from the in vitro tests were submitted to two-way analysis of variance and Tukey test (α = 0.5). The cemented restorations presented less torque loosening (19.79 N.cm), lower vertical misfit (3.77 µm), lower stress concentration in the restoration (88.2 MPa) and higher fracture load (451.3 N) than notched restorations (15.95 N.cm, 10.51 µm, 99.8 MPa and 390.8 N, respectively). Conclusion: The presence of a cement layer between restoration and titanium base reduced the susceptibility to abutment screw loosening, improved the resistance to compressive load and reduced the stress concentration in the restoration(AU)

Adjacent implant-supported restorations in the esthetic zone: understanding the biology.

UNLABELLED: Traditionally, whe n considering adjacent implants in the esthetic zone, clinicians have encountered problems associated with deficient interproximal soft tissues. These discrepancies were often solved either by fabricating restorations with long interproximal contacts or by adding pink ceramics, both of which represent an esthetic compromise in today's demanding standard of care for restorative dentistry. This challenge has led to the recent introduction of scalloped implants. An understanding of the biology of wound healing of bone and soft tissue around implants and the remodeling process with implant-supported restorations allows the dental team to offer patients an alternative restorative solution consisting of combining conventional flat prosthetic table implants and scalloped implants. CLINICAL SIGNIFICANCE: This article illustrates the biologic behavior of wound healing associated with dental implants and shows a step-by-step clinical case in which a patient received four adjacent implants in the esthetic zone. It also describes key elements in laboratory communication when dealing with the aforementioned restorations.

Achieving aesthetic success with an immediate-function implant and customized abutment and coping.

UNLABELLED: The absence of teeth in the anterior region often results in a number of negative consequences compromising appearance and facial anatomy, as well as patients' self-esteem and social behavior. Dental implants have increasingly become a viable option for achieving natural-looking restorations. The success of anterior restorations, however, depends upon several factors. The following case presentation discusses these factors as well as the implementation of clinical and laboratory procedures for the restoration of a missing anterior tooth. LEARNING OBJECTIVES: This article demonstrates an implant surgical procedure and restorative sequence used to replace a fractured single anterior tooth. Upon reading this article, the reader should: Understand how dental implants can be a viable solution based upon factors within the proximity of the region being restored. Realize that optimal aesthetics can be achieved when the final abutment is installed at the time of implant placement.

Restaurados cerâmicos com as novas porcelanas hidrotérmicas de baixa fusäo (LFC) / Ceramic restorations with low-fusing hydrothermal dental ceramics (LFC)

Säo apresentadas as etapas clínicas e laboratoriais da utilizaçäo das porcelanas hidrotérmicas de baixa fusäo (LFC) na construçäo dos restaurados cerâmicos com uma maior qualidade estética