Examining the effects of acid etching duration on the bond strength between two CAD/CAM materials and one composite resin.

This study aimed to evaluate the effect of three hydrofluoric acid (HF) etching periods on the micro-tensile bond strength between two CAD-CAM ceramic systems [Vita Suprinity (VS) and feldspathic CEREC blocs (CB)] and a composite resin. The ceramics were categorized into six groups based on the surface conditioning protocol used, as follows: G1: CB-HF 5% for 20 s; G2: CB-HF 5% for 40 s; G3: CB-HF 5% for 60 s; G4: VS-HF 5% for 20 s; G5: VS-HF 5% for 40 s; G6: VS-HF 5% for 60 s. Scotchbond Universal was applied onto the pretreated ceramic surfaces and covered with Filtek Z350 XT composite resin. After 24 h, the specimens were cut into microbars (n = 16) and a micro-tensile bond strength test (µTBS) was carried out. An optical microscope was used to examine the fractured microbars. The results showed statistically significant differences between the factors tested (p < 0.01). Moreover, the mean MPa of G1(17.27), G2(13.03), G3(12.82), G4(15.83), G5(21.66), and G6(14.50) was seen to significantly differ. The predominant failure type observed was adhesive, and all three periods of HF etching produced satisfactory bonding between the composite resin and CB. An etching time of 40 s provided the highest µTBS value for VS.

The influence of roughness on the resistance to impact of different CAD/CAM dental ceramics

Abstract This study aimed to investigate the effect of surface roughness (polished vs. CAD/CAM milling simulation) on impact strength of five dental ceramics for manufacturing CAD/CAM monolithic restorations. Specimens of five ceramics (FC- feldspathic glass-ceramic; PICN- polymer-infiltrated ceramic-network; ZLS- zirconia-reinforced lithium silicate glass-ceramic; LD- lithium disilicate glass-ceramic; YZ- yttria-stabilized tetragonal zirconia polycrystal ceramic) to be tested under impact (15×10×2mm3; n= 15) were divided into two groups, according to surface treatment: polishing (pol) and grinding (gri) as CAD/CAM milling simulation. Impact strength was tested using the Dynstat method. Roughness, topographic, fractographic and finite element analyses were performed. The impact strength data were analyzed by Weibull, and Pearson correlation was used to correlate roughness and impact strength data. The CAD/CAM milling simulation led to significantly (p<0.05) greater roughness (Ra and Rz) and statistically reduced the impact strength for PICN (polPICN= 4.59 to griPICN= 1.09; ±76% decrease), for LD (polLD= 17.69 to griLD= 10.09; ±43% decrease) and for YZ (polYZ= 74.99 to griYZ= 20.67; ±72% decrease) ceramics; and also promoted a more irregular topography with scratches and grooves. Fractographic and FEA analyses depicted the origin of failure at the higher stress concentration side during the impact test, where the pendulum impacted. The CAD/CAM milling simulation significantly decreased the impact strength of the evaluated ceramic materials.

Resumo Este estudo teve como objetivo investigar o efeito da rugosidade da superfície (polido vs. simulação da usinagem em CAD/CAM) na resistência ao impacto de cinco cerâmicas odontológicas indicadas na fabricação de restaurações monolíticas em CAD/CAM. Espécimes de cinco cerâmicas (FC- vitrocerâmica feldspática; PICN- rede de cerâmica infiltrada com polímero; ZLS- vitrocerâmica de silicato de lítio reforçada com zircônia; LD- vitrocerâmica de dissilicato de lítio; YZ- cerâmica policristalina de zircônia tetragonal estabilizada com ítria), a serem testados sob impacto (15 × 10 × 2mm3; n= 15), foram divididos em dois grupos, de acordo com o tratamento superficial: polimento (pol) e desgaste (gri), usado como simulação da usinagem em CAD/CAM. A resistência ao impacto foi testada usando o método Dynstat. Foram realizadas as análises de rugosidade, topografia, fractografia e análise de elementos finitos. Os dados de resistência ao impacto foram analisados pela análise de Weibull, e a correlação de Pearson foi usada para correlacionar os dados de rugosidade e resistência ao impacto. A simulação da usinagem em CAD/CAM levou a uma rugosidade (Ra e Rz) significativamente maior (p < 0,05) para todas as cerâmicas, e reduziu estatisticamente a resistência ao impacto para as cerâmicas PICN (polPICN = 4,59 para griPICN = 1,09; redução de ± 76%), LD (polLD = 17,69 para griLD = 10,09; ± 43% de redução) e YZ (polYZ = 74,99 para griYZ = 20,67; ± 72% de redução); e também promoveu uma topografia mais irregular apresentando riscos e sulcos acentuados. As análises de fractografia e de elementos finitos mostraram a origem da falha no lado de maior concentração de tensão durante o teste de impacto, onde o pêndulo impactou o espécime. A simulação da usinagem em CAD/CAM reduziu significativamente a resistência ao impacto dos materiais cerâmicos avaliados.

Biomechanical behavior of CAD/CAM cobalt-chromium and zirconia full-arch fixed prostheses.

PURPOSE: To verify the influence of computer-aided design/computer-aided manufacturing (CAD/CAM) implant-supported prostheses manufactured with cobalt-chromium (Co-Cr) and zirconia (Zr), and whether ceramic application, spark erosion, and simulation of masticatory cycles modify biomechanical parameters (marginal fit, screw-loosening torque, and strain) on the implant-supported system. MATERIALS AND METHODS: Ten full-arch fixed frameworks were manufactured by a CAD/CAM milling system with Co-Cr and Zr (n=5/group). The marginal fit between the abutment and frameworks was measured as stated by single-screw test. Screw-loosening torque evaluated screw stability, and strain analysis was explored on the implant-supported system. All analyses were performed at 3 distinct times: after framework manufacturing; after ceramic application in both materials' frameworks; and after the spark erosion in Co-Cr frameworks. Afterward, stability analysis was re-evaluated after 106 mechanical cycles (2 Hz/150-N) for both materials. Statistical analyses were performed by Kruskal-Wallis and Dunn tests (α=.05). RESULTS: No difference between the two materials was found for marginal fit, screw-loosening torque, and strain after framework manufacturing (P>.05). Ceramic application did not affect the variables (P>.05). Spark erosion optimized marginal fit and strain medians for Co-Cr frameworks (P<.05). Screw-loosening torque was significantly reduced by masticatory simulation (P<.05) regardless of the framework materials. CONCLUSION: Co-Cr and Zr frameworks presented similar biomechanical behavior. Ceramic application had no effect on the biomechanical behavior of either material. Spark erosion was an effective technique to improve Co-Cr biomechanical behavior on the implant-supported system. Screw-loosening torque was reduced for both materials after masticatory simulation.

Analysis of Vertical Misfit of Crowns Fabricated with CAD/CAM Technology using Two Scanning Techniques: Direct and Indirect.

AIM: The study evaluated the marginal vertical misfit of feldspathic ceramic crowns fabricated by the computer-aided design (CAD)/computer-aided manufacturing (CAM) technology and compared the two methods of scanning techniques: direct digital impression and indirect digital impression. MATERIALS AND METHODS: The titanium specimens were divided into two groups: scanning with the direct digital impression (DDI) at the milled prosthetic abutment level and indirect digital impression (IDI) at the cast model and after milled feldspathic ceramics blocks. Vertical marginal misfit was analyzed. The t-test was used for the analysis of the comparison factor between the groups and the one-way analysis of variance (ANOVA) test, and post hoc Tukey test was used to compare the variance of crown analysis regions within the group. A significance level of 5% was considered for the analyses. RESULTS: There was no significant difference in vertical marginal misfit between the groups of DDI and IDI (p = 0.345). In relation to each region measured within the studied groups, it was observed the similarity between the six regions analyzed in the DDI group (p >0.05) and IDI group, a significant difference between two areas. CONCLUSION: The vertical marginal adaptation was similar between digital scanning methods. Based on the data evaluated, vertical marginal adaptation indices were within acceptable clinical standards. CLINICAL SIGNIFICANCE: The direct digital scanning in unit bodies was reliable, pointing that the coating of titanium dioxide in the titanium abutment did not negatively influence the vertical marginal adaptation of the feldspathic ceramic crowns.

Effect of Intracoronal Depth of Teeth Restored with Endocrowns on Fracture Resistance: In Vitro and 3-dimensional Finite Element Analysis.

INTRODUCTION: Endodontically treated teeth have an increased risk of biomechanical failure because of significant loss of tooth structure. The biomechanical behavior of endodontically treated teeth restored was evaluated using different extensions of endocrowns inside the pulp chamber by in vitro and 3-dimensional finite element analysis (FEA). METHODS: Thirty mandibular human molars were endodontically treated. Standardized endocrown preparations were performed, and the teeth were randomly divided into 3 groups (n = 10) according to different endocrown extensions inside the pulp chamber: G-5 mm, a 5-mm extension; G-3 mm, a 3-mm extension; and G-1 mm, a 1-mm extension. After adhesive cementation, all specimens were subjected to thermocycling and dynamic loading. The survival specimens were subjected to fracture resistance testing at a crosshead speed of 1 mm/min in a universal testing machine. All fractured specimens were subjected to fractography. Data were analyzed by 1-way analysis of variance and the Tukey post hoc test (P < .05). Stress distribution patterns in each group were analyzed using FEA. Qualitative analyses were performed according to the von Mises criterion. RESULTS: After dynamic loading, a survival rate of 100% was observed in all groups. For static loading, statistically significant differences among the groups were observed (P < .05) (G-5 mm = 2008.61 N, G-3 mm = 1795.41 N, and G-1 mm = 1268.12 N). Fractography showed a higher frequency of compression curls for G-5 mm and G-3 mm than for G-1 mm. FEA explained the results of fracture strength testing and fractography. CONCLUSIONS: Greater extension of endocrowns inside the pulp chamber provided better mechanical performance.

Passivity of Conventional and CAD/CAM Fabricated Implant Frameworks

The objective of this research was to evaluate the passivity by measuring the passive fit and strain development of frameworks screwed on abutments, made by CAD/CAM technology, and to compare these parts with samples manufactured by conventional casting. Using CAD/CAM technology, four samples were made from zirconia (Zircad) and four samples were manufactured from cobalt-chrome (CoCrcad). The control groups were four specimens of cobalt-chrome, made by one-piece casting (CoCrci), with a total of 12 frameworks. To evaluate the passive fit, the vertical misfit at the abutment-framework interface was measured with scanning electron microscopy (250×) when only one screw was tightened. The mean strain in these frameworks was analyzed by photoelasticity test. A significant difference in the passive fit was observed between the control and sample groups. CoCrcad exhibited the best value of passive fit (48.76±13.45 µm) and CoCrci the worst (187.55±103.63 µm); Zircad presented an intermediate value (103.81±43.15 µm). When compared to the other groups, CoCrci showed the highest average stress around the implants (17.19±7.22 kPa). It was concluded that CAD/CAM-fabricated frameworks exhibited better passivity compared with conventionally fabricated frameworks. CAD/CAM-fabricated Co-Cr frameworks may exhibit better passive fit compared with CAD/CAM-fabricated zirconia frameworks. Even so, similar levels of stress were achieved for CAD/CAM-fabricated frameworks.

O objetivo desta pesquisa foi avaliar a passividade através da medição da tensão induzida e adaptação passiva em infra-estruturas parafusadas sobre pilares, confeccionadas por tecnologia CAD/CAM, e comparar estas amostras com peças fabricadas por fundição convencional. Usando a tecnologia de CAD/CAM, quatro amostras foram feitas em zircônia (ZirCAD) e quatro amostras foram fabricados em cobalto-cromo (CoCrcad). Os grupos controle foram quatro espécimes de cobalto-cromo, feitos por fundição em monobloco (CoCrci), totalizando 12 infra-estruturas. Para avaliar a adaptação passiva, a diferença vertical entre a infraestrutura e o pilar protético foi medido em microscopia eletrônica de varredura (250 ×) quando apenas um parafuso foi apertado. A tensão média nestas infraestruturas foi analisada através do teste de fotoelasticidade. Foi observada uma diferença significativa na passividade entre os grupos controle e demais amostras. CoCrcad exibiu melhor valor de adaptação passiva (48,76±13,45 mm) e CoCrci o pior (187,55±103,63 mm), Zircad apresentou um valor intermediário (103,81±43,15 µm). Quando comparado com os outros grupos, CoCrci apresentou a maior tensão média ao redor dos implantes (17,19±7,22 kPa). Concluiu-se que a tecnologia CAD/CAM exibiu maior passividade em comparação com as infraestruturas confeccionadas pela técnica convencional. Infraestruturas confeccionadas em Co-Cr através do CAD/CAM apresentaram maior adaptação passiva em comparação com as amostras confeccionadas por CAD/CAM em zircônia. Entretanto, níveis de estresse similares foram obtidos para as estruturas fabricadas por CAD/CAM.

Dual-scan technique for the customization of zirconia computer-aided design/computer-aided manufacturing frameworks.

The use of bi-layered all-ceramic crowns has continuously grown since the introduction of computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia cores. Unfortunately, despite the outstanding mechanical properties of zirconia, problems related to porcelain cracking or chipping remain. One of the reasons for this is that ceramic copings are usually milled to uniform thicknesses of 0.3-0.6 mm around the whole tooth preparation. This may not provide uniform thickness or appropriate support for the veneering porcelain. To prevent these problems, the dual-scan technique demonstrates an alternative that allows the restorative team to customize zirconia CAD/CAM frameworks with adequate porcelain thickness and support in a simple manner.