New adhesive protocol improves shear bond strength of Polyetherketoneketone (PEKK).

OBJECTIVE: Inert surface of Polyetherketoneketone (PEKK) jeopardizes resin bonding. This study aimed to present a new adhesive protocol to improve PEKK bonding. METHODS: A total of 360 PEKK blocks were milled, polished (maximum roughness of 0.20 µm), and randomly assigned to groups. The new protocol was applied (n = 36) and compared to conventional treatments (no treatment; sandblasting (110-µm Al2O3 and silica); no adhesive; Visiolink (Bredent); and PEKKbond (AnaxDent)) (n = 36). For the new protocol, the surface was blasted (110 µm Al2O3 and 96% isopropyl alcohol at 60 psi), followed by 96% isopropyl alcohol washing, and air drying. PEKKbond was applied (dried for 3 min at 77 °C), followed by Visiolink (dried for 3 min at 60 °C); both light-cured for 3 min (800 mW/cm2). Preopaque (GC Europe) and Opaque (AnaxDent) were applied and light-cured (5 min). Morphological topography was analyzed, and flowable gingiva-colored composite (AnaxGum, AnaxDent) was bonded. All specimens were aged for 24 h and thermocycled (5000 cycles, 5-55 °C). Shear bond strength (SBS) was measured (MPa) and data were analyzed by two-way ANOVA, Tukey, and Weibull moduli estimation (α = 0.05). RESULTS: The highest SBS values were found in the new protocol (p < 0.05), regardless of aging. Thermocycling reduced SBS (p < 0.05), while Al2O3 and PEKKbond produced higher SBS values than silica and Visiolink, respectively (p < 0.05). SIGNIFICANCE: The new protocol strongly improves PEKK adhesiveness, and this can reflect in the longevity of prostheses.

Mechanical Response of PEKK and PEEK As Frameworks for Implant-Supported Full-Arch Fixed Dental Prosthesis: 3D Finite Element Analysis.

OBJECTIVE: Polymeric framework represent an innovative approach for implant-supported dental prostheses. However, the mechanical response of ultra-high performance polymers as frameworks for full-arch prostheses under the "all-on-four concept" remains unclear. The present study applied finite element analysis to examine the behavior of polyetherketoneketone (PEKK) and polyetheretherketone (PEEK) prosthetic frameworks. MATERIALS AND METHODS: A three-dimensional maxillary model received four axially positioned morse-taper implants, over which a polymeric bar was simulated. The full-arch prosthesis was created from a previously reported database model, and the imported geometries were divided into a mesh composed of nodes and tetrahedral elements in the analysis software. The materials were assumed as isotropic, elastic, and homogeneous, and all contacts were considered bonded. A normal load (500 N magnitude) was applied at the occlusal surface of the first left molar after the model was fixed at the base of the cortical bone. The microstrain and von-Mises stress were selected as criteria for analysis. RESULTS: Similarities in the mechanical response were observed in both framework for the peri-implant tissue, as well as for stress generated in the implants (263-264 MPa) and abutments (274-273 MPa). The prosthetic screw and prosthetic base concentrated more stress with PEEK (211 and 58 MPa, respectively) than with PEKK (192 and 49 MPa), while the prosthetic framework showed the opposite behavior (59 MPa for PEEK and 67 MPa for PEKK). CONCLUSION: The main differences related to the mechanical behavior of PEKK and PEEK frameworks for full-arch prostheses under the "all-on-four concept" were reflected in the prosthetic screw and the acrylic base. The superior shock absorbance of PEKK resulted in a lower stress concentration on the prosthetic screw and prosthetic base. This would clinically represent a lower fracture risk on the acrylic base and screw loosening. Conversely, lower stress concentration was observed on PEEK frameworks.

Effect of active application of self-etching ceramic primer on the long-term bond strength of different dental CAD/CAM materials.

BACKGROUND: The objective of this in vitro study was to evaluate the effect of the active application of self-etching ceramic primer (ME&P) on the bond strength of different dental CAD/CAM materials (Lithium Disilicate ceramic (LD), Leucite ceramic (LE), Zirconia reinforced lithium silicate ceramic (ZLS), and Hybrid ceramic (HC)) with thermocycling aging. MATERIAL AND METHODS: The samples were randomly divided into 16 groups (n = 20). Dual resin cement cylinders were made and light cured for 10 s (1.200 mW/cm2) for the shear bond strength test. 3-way ANOVA revealed that the factors were statistically significant (P< 0.05). RESULTS: The aging process had a negative impact on the bond strength for all groups except for Lithium Disilicate, with active application. ZLS and LE showed promising results with high bond strength values for the ME&P active application; however, after aging the bond strength value was significantly reduced. HC showed reduced bond strength values regardless the ME&P application. CONCLUSIONS: In order to obtain a durable bond strength, the recommended protocol of 20 s of active application followed by 40 s of sitting time in the self-etching ceramic primer should be followed when using reinforced-glass ceramics as restorative materials. Key words:Dentistry, dental materials, silane, shear strength, computer-aided design.

Evaluation of the influence of the impression technique, scanning direction and type of scanner on the accuracy of the final model / Avaliação da influência da técnica de impressão, direção de digitalização e tipo de scanner na precisão do modelo final

Objective: The purpose of this study is to evaluate the influence of the type of scanner and scanning direction on the accuracy of the final cast. Material and Methods: A partial master cast was used as a reference. A total of 128 scans were obtained and divided into two groups: the conventional method and the digital method. The digital group was divided into three groups: TRIOS 3, Omnicam and CS 3600. Each of these groups was subdivided according to the scanning direction, and each scan was overlaid on the digital reference cast to measure the trueness and precision of the procedures. Results: The overall precision values for the type of impression were 59.89 ± 13.08 µm for conventional and 13.42 ± 4.28 µm for digital; the values for trueness were 49.37 ± 19.13 µm for conventional and 53.53 ± 4.97 µm for digital; the scanning direction trueness values were 53.05 ± 4.36 µm for continuous and 54.03 ± 5.52 µm for segmented; and the precision values were 14.18 ± 4.67 µm for continuous and 12.67 ± 3.75 µm for segmented (p> 0.05). For the scanner type, the trueness values were 50.06 ± 2.65 µm for Trios 3, 57.45 ± 4.63 µm for Omnicam, and 52.57 ± 4.65 µm for Carestream; and those for precision were 11.7 ± 2.07 µm for Trios 3, 10.09 ± 2.24 µm for Omnicam, and 18.49 ± 2.42 µm for Carestream (p <0.05). Conclusions: The digital impression method is the most favorable method regarding precision; in terms of trueness, there are no differences between the types of impressions. (AU)

Objetivo: O objetivo deste estudo é avaliar a influência do tipo de técnica de moldagem, tipo de escâner intraoral e direção do escaneamento na precisão do modelo final. Material e Métodos: Um modelo parcial mestre foi usado como referência. Um total de 128 escaneamentos foi obtido e dividido em dois grupos: o método convencional (n = 32) e o método digital (n = 96). O grupo digital foi dividido em três grupos: TRIOS 3 (n = 32), Omnicam (n = 32) e CS 3600 (n = 32). Cada um desses grupos foi subdividido de acordo com a direção do escaneamento (n = 16), e cada escaneamento foi sobreposto ao modelo de referência digital para medir a veracidade e precisão dos procedimentos. Resultados: Os valores gerais de precisão para o tipo de impressão foram 59,89 ± 13,08 µm para convencional e 13,42 ± 4,28 µm para digital; os valores de veracidade foram 49,37 ± 19,13 µm para convencional e 53,53 ± 4,97 µm para digital; os valores de veracidade para a direção de digitalização foram 53,05 ± 4,36 µm para contínua e 54,03 ± 5,52 µm para segmentada; e os valores de precisão foram 14,18 ± 4,67 µm para contínua e 12,67 ± 3,75 µm para segmentada (p> 0,05). Para o tipo de scanner, os valores de veracidade foram 50,06 ± 2,65 µm para Trios 3, 57,45 ± 4,63 µm para Omnicam e 52,57 ± 4,65 µm para Carestream; e os de precisão foram 11,7 ± 2,07 µm para Trios 3, 10,09 ± 2,24 µm para Omnicam e 18,49 ± 2,42 µm para Carestream (p <0,05). Conclusões: O método de moldagem digital é o método mais favorável em relação à precisão; em termos de veracidade, não há diferenças entre os tipos de impressão (AU)

Study of the pterygoid canal (vidian canal) through images of cone beam computer tomography / Estudo do canal Pterigóideo (canal Vidiano) por meio de imagens de tomografia computadorizada de feixe cônico

Objective: The aim of this study was to evaluate the pterygoid canal (PC) by Cone Beam Computed Tomography (CBCT), establishing its configuration and proximity with anatomical structures. Material and Methods: We evaluated 398 CBCT exams, all from a public University radiology clinic archive. Four parameters were evaluated: single or double PC, distance between PC and the inferior part of the sphenoid sinus (SS), ratio of PC and SS and the distance between the PC and the foramen rotundum. Results: It was observed that most of the PC of the sample presented simple morphology, the most frequent type of relationship between the PC and the SS on both sides was the close contact with the wall. Among the cases that there were some distances between the PC and the inferior wall of the SS, the mean of this distance did not exceed 3.20 mm, being the left side (3.03 mm) slightly closer than the right (3.20 mm). Finally, the distances between the PC and the corresponding Foramen Rotundum are presented with mean values of 5.87 mm for the right side and 6.31 mm for the left side. Conclusion: CBCT examination is of paramount importance for PC identification; once in the studied sample, the mean values found evidence the close relation between the PC and the SS (AU)

Objetivo: O objetivo deste estudo foi avaliar o CP pela TCFC, estabelecendo sua configuração e proximidade com estruturas anatômicas. Material e Métodos: Foram avaliados 398 exames de TCFC, todos de um arquivo público da clínica de radiologia da Universidade. Foram avaliados quatro parâmetros: CP único ou duplo, distância entre PC e parte inferior do seio esfenoidal (SS), razão entre PC e SS e a distância entre o PC e o forame redondo. Resultados: Observou-se que a maioria dos CP da amostra apresentava morfologia simples, o tipo de relação mais frequente entre o CP e o SS de ambos os lados foi o contato próximo com a parede. Entre os casos em que houve algumas distâncias entre o CP e a parede inferior da ES, a média dessa distância não excedeu 3,20 mm, sendo o lado esquerdo (3,03 mm) um pouco mais próximo do que o direito (3,20 mm). Finalmente, as distâncias entre o PC e o forame redondo correspondente são apresentadas com valores médios de 5,87 mm para o lado direito e 6,31 mm para o lado esquerdo. Conclusão: O exame TCFC é de suma importância para a identificação do CP; uma vez na amostra estudada, os valores médios encontrados evidenciam a estreita relação entre o CP e o SS. (AU)

Resistência à fadiga de vitrocerâmicas cristalizadas por energia de micro-ondas / Fadigue resistance of glass-ceramics crystallized by microwave energy

O objetivo deste trabalho foi analisar a resistência à fadiga de duas vitrocerâmicas cristalizadas convencionalmente ou por energia de microondas. Foram confeccionados 120 discos (N) de 1,2 milímetros de espessura e 12 milímetros de diâmetro e estes foram distribuídos em 4 grupos (n=30) ­ Celtra cristalizado convencionalmente (CC), Celtra cristalizado por energia de micro-ondas (CM), e.max cristalizado convencionalmente (EC) e e.max cristalizado por energia de micro-ondas (EM). Foi realizado o cálculo de resistência à flexão biaxial em 5 amostras de cada grupo, servindo como parâmetro para a definição das taxas de carregamento do teste de fadiga. Os demais espécimes foram distribuídos na proporção 9:6:3 e testados sob fadiga acelerada (step stress) nos perfis leve (9), moderado (6) e agressivo (3), variando os incrementos de carga e o número de ciclos. Os espécimes fraturados foram avaliados em estereomicroscópio e microscópio eletrônico de varredura (MEV), para análise da superfície e das características de fratura. Os dados de sobrevivência foram utilizados para calcular o valor beta (ß) de Weibull e a confiabilidade para as missões dadas. Foi calculada a probabilidade de sobrevivência ­ de acordo com a carga e o número de ciclos ­ usando um software para análise de fadiga. Os valores de beta (ß) para os grupos CC, CM, EC e EM foram, respectivamente, 2,65, 0,25, 0,62 e 0,3. Quanto à confiabilidade para missões de 50.000 ciclos, não houve diferença estatística quando a carga aplicada foi de 50 Mpa. Para a carga de 100 Mpa, apenas o grupo CM apresentou diferença estatistica em relação aos outros grupos, com maior probabilidade de falha. O método de cristalização não influenciou no desempenho do dissilicato de lítio com 150 Mpa de carga, enquanto o silicato de lítio reforçado por zircônia apresentou 9% a mais de confiabilidade quando cristalizado convencionalmente. Com 200 e 300 Mpa de carga, o método de cristalização e o tipo de cerâmica influenciaram no resultado, com destaque para o desempenho do dissilicato de lítio cristalizado por energia de micro-ondas (maior confiabilidade; 89% para 200 Mpa e 6% para 300 Mpa). Concluiu-se que a cristalização por energia de micro-ondas é uma alternativa viável, pois apresentou resistência compatível aos grupos controle, com o grande benefício de economia de energia(AU)

The objective of this study was to analyze the fatigue strength of two glass ceramics conventionally crystallized or crystallized by microwave energy. 120 discs (N) of 1.2 mm thickness and 12 mm diameter were made and distributed in 4 groups (n=30) ­ Celtra conventionally crystallized (CC), Celtra crystallized by microwave energy (CM), e.max conventionally crystallized (EC) and e.max crystallized by microwave energy (EM). Biaxial flexural strength was calculated in 5 samples from each group, serving as a parameter to define the loading rates of the fatigue test. The remaining specimens were distributed in a 9: 6: 3 ratio and tested under step stress in light (9), moderate (6) and aggressive (3) profiles, varying the load increments and the number of cycles. Fractured specimens were evaluated by stereomicroscope and scanning electron microscope (SEM) for surface and fracture characteristics analysis. Survival data were used to calculate Weibull's beta (ß) value and reliability for the given missions. The survival probability - according to load and number of cycles - was calculated using software for fatigue analysis. The beta (ß) values for the CC, CM, EC and MS groups were, respectively, 2.65, 0.25, 0.62 and 0.3. For 50,000 cycles missions, there was no statistical difference when the applied load was 50 Mpa. For the 100 Mpa load, only the CM group presented statistical difference with the other groups, with a higher probability of failure. The crystallization method did not influence the performance of the 150 Mpa charged lithium disilicate, while zirconia reinforced lithium silicate showed 9% more reliability when conventionally crystallized. At 200 and 300 Mpa of charge, the crystallization method and the type of ceramic influenced the result, especially the performance of microwave energy crystallized lithium disilicate (higher reliability; 89% for 200 Mpa and 6% for 300 Mpa). It was concluded that microwave energy crystallization is a viable alternative because presented resistance compatible with the control groups, with the with the great benefit of energy saving(AU)