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Resumo Este estudo teve como objetivo avaliar a resistência à fractura do silicato de lítio reforçado com zircônio todo o material cerâmico "Celtra Press" em comparação com um "IPS e-max Press" em condições orais simuladas. Quatorze coroas cerâmicas foram fabricadas em moldes epóxi que foram duplicados a partir de moldes principais de aço inoxidável e divididos em dois grupos iguais (n=7) de acordo com o material de construção; Grupo A: Coroas fabricadas com material IPS e-max Press e Grupo B: Coroas fabricadas com material Celtra Press. As coroas foram então cimentadas nos seus moldes correspondentes com um cimento de resina auto-adesivo e submetidas a ciclos térmicos e cargas cíclicas. Em seguida, foram carregadas para fraturar numa máquina universal de ensaios. Os resultados foram tabulados e analisados estatisticamente utilizando os testes Kolmogorov-Smirnov e Shapiro-Wilk. O teste t de Student usado para comparar os valores médios. O nível de significância foi fixado em P ≤ 0,05 e intervalo de confiança de 95%. A análise estatística foi realizada utilizando o software Graph Pad Instat (Graph Pad, Inc.) para Windows. Os valores médios ± SD da resistência à fractura foram registados para o grupo Disilicate de lítio (1706,01 ±154,32 N) enquanto que os valores médios ± SD registados com o grupo celtra foram (1550,67±196,71 N). As coroas cerâmicas de silicato de lítio reforçado com zircónio produziram valores de resistência à fractura comparáveis aos das coroas cerâmicas de dissilicato de lítio e ambos os materiais testados estão dentro dos valores clinicamente aceitáveis na área posterior.
Abstract The aim of this study was conducted to assess the fracture resistance of zirconia reinforced lithium silicate all ceramic material "Celtra Press" compared to lithium disilicate one "IPS e-max Press" under simulated oral conditions. Fourteen ceramic crowns were fabricated on epoxy dies which were duplicated from stainless steel master die and divided into two equal groups (n=7) according to the material of construction; Group A: Crowns fabricated with IPS e-max Press material and Group B: Crowns fabricated with Celtra Press material. The crowns were then cemented onto their corresponding dies with a self-adhesive resin cement and subjected to thermocycling and cyclic loading. Then they were loaded to fractur in a universal testing machine. The results were tabulated and statistically analyzed using Kolmogorov-Smirnov and Shapiro-Wilk tests. Student t-test used to compare mean values. The significance level was set at P ≤ 0.05 and 95% Confidence interval. Statistical analysis was performed using Graph Pad Instat (Graph Pad, Inc.) software for windows. The mean ± SD values of fracture resistance were recorded for lithium Disilicate group (1706.01 ±154.32 N) meanwhile the mean ± SD value recorded with celtra group were (1550.67±196.71 N). Zirconia reinforced lithium silicate ceramic crowns produced comparable fracture resistance values to lithium disilicate ceramic crowns and both tested materials are within the clinically acceptable values in the posterior area.
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BACKGROUND: Medial column instability is a frequent finding in patients with flatfeet and hallux valgus, within others. The etiology of hallux valgus is multifactorial, and medial ray axial rotation has been mentioned as having an individual role. Our objective was to design a novel cadaveric foot model where we could re-create through progressive medial column ligament damage some components of a hallux valgus deformity. METHODS: Ten fresh-frozen lower leg specimens were used, and fluorescent markers were attached in a multisegment foot model. Constant axial load and cyclic tibial rotation (to simulate foot pronation) were applied, including pull on the flexor hallucis longus tendon (FHL). We first damaged the intercuneiform (C1-C2) ligaments, second the naviculocuneiform (NC) ligaments, and third the first tarsometatarsal ligaments, leaving the plantar ligaments unharmed. Bony axial and coronal alignment was measured after each ligament damage. Statistical analysis was performed. RESULTS: A significant increase in pronation of multiple segments was observed after sectioning the NC ligaments. Damaging the tarsometatarsal ligament generated small supination and varus changes mainly in the medial ray. No significant change was observed in axial or frontal plane alignment after damaging the C1-C2 ligaments. The FHL pull exerted a small valgus change in segments of the first ray. DISCUSSION: In this biomechanical cadaveric model, the naviculocuneiform joint was the most important one responsible for pronation of the medial column. Bone pronation occurs along the whole medial column, not isolated to a certain joint. Flexor hallucis longus pull appears to play some role in frontal plane alignment, but not in bone rotation. This model will be of great help to further study medial column instability as one of the factors influencing medial column pronation and its relevance in pathologies like hallux valgus. CLINICAL RELEVANCE: This cadaveric model suggests a possible influence of medial column instability in first metatarsal pronation. With a thorough understanding of a condition's origin, better treatment strategies can be developed.
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Joanete , Hallux Valgus , Hallux , Ossos do Metatarso , Cadáver , Hallux Valgus/patologia , Hallux Valgus/cirurgia , Humanos , Ossos do Metatarso/patologiaRESUMO
Objectives: With regard to the prevalence of abutment screw loosening (SL) and bone height reduction, particularly in the posterior regions of the jaws, as well as the contradictory issue of applying short implants instead of surgeries, along with all preparations associated with longer implants, the present study aimed to compare the amount of torque loss in short implants with increased vertical cantilever abutments and standard ones. Material and Methods: In this experimental study, a total number of 20 implants (MegaGen Implant Co., Ltd, South Korea) with 4.5 mm diameter including 10 short implants (7 mm) and 10 standard ones (10 mm) were utilized. Using a surveyor, fixtures were perpendicularly mounted in 13×34 mm resin for short implants and 19×34 mm resin for standard ones. The abutments of the same height but different cuff heights (2.5 mm for the standard implants and 5.5 mm for the short ones) were then tightened with 30 N.cm, via a digital torque meter. To compensate the settling effect, the abutment screw was re-tightened with 30 N.cm after 10 min. Upon applying 500,000 cycles at 75 N.cm and 1 Hz along the longitudinal axis on each sample, blind reverse torque value (RTV) was measured with a digital torque meter. The data were finally analyzed using Student's t-test. Results:Both groups experienced torque loss, but there was no statistically significant difference between the case and control groups in terms of abutment SL (p = 0451). Conclusion: Short implants seem to be a good mechanical alternative in emergencies with respect to torque loss and abutment SL. (AU)
Objetivos: Considerando a prevalência de afrouxamento de parafuso dos pilares, redução da altura óssea especialmente nas regiões posteriores, a questão contraditória da aplicação de implantes curtos em vez de cirurgias e todos os preparos associados a implantes mais longos, este estudo buscou comparar implantes curtos com pilares cantilever verticais aumentados e implantes padrão na quantidade de perda de torque. Material e métodos: Neste estudo experimental, foram utilizados 20 implantes (Megagen, Coreia do Sul) com diâmetro de 4,5 mm, incluindo 10 implantes curtos (7 mm) e 10 implantes padrão (10 mm). A fixação foi realizada perpendicularmente em uma resina 13 × 34 mm para implantes curtos e uma resina 19 × 34 mm para implantes padrão, usando um topógrafo. Os pilares da mesma altura, mas com diferentes comprimentos de manguito (2,5 mm para os implantes padrão e 5,5 mm para os implantes curtos) foram apertados com 30 N, utilizando um torquímetro digital. Para compensar o efeito de sedimentação, o parafuso do pilar foi reapertado com 30 N após 10 min. Depois de aplicar 500.000 ciclos a 75 N e 1 Hz ao longo do eixo longitudinal em cada amostra, o valor de torque reverso cego foi medido com um medidor de torque digital. Os dados foram analisados pelo teste t de Student. Resultados: Todos os grupos tiveram perda de torque, mas não houve diferença estatisticamente significativa entre os grupos caso e controle em termos de afrouxamento do parafuso do pilar (p = 0451). Conclusão: Os implantes curtos parecem ser uma boa alternativa mecânica em emergências em termos de perda de torque e afrouxamento do parafuso do pilar. (AU)
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Parafusos Ósseos , Torque , Implantação DentáriaRESUMO
Fiber-reinforced foamed concrete (FRFC) is a lightweight material that has the potential to perform well in seismic applications due to its low density and improved mechanical properties. However, studies focused on the seismic assessment of this material are limited. In this work, U-shaped wall specimens, made of FRFC reinforced with henequen fibers and plain foamed concrete (PFC) with a density of 900 kg/m3, were subjected to shaking table tests. PFC and FRFC were characterized using compression and tension tests. FRFC exhibited enhanced mechanical properties, which were attributed to the fibers. The dynamic tests showed that U-shaped walls made of FRFC performed better than those made of PFC. The time period prior to the collapse of the FRFC U-shaped walls was longer than that of the PFC specimens, which was attributed to the enhanced specimen integrity by the fibers. Finite element simulations of the shaking table test allowed for the prediction of the stress concentration and plastic strain that may lead to the failure of the U-shaped wall. These results showed that U-shaped walls made of FRFC have the potential to perform well in seismic applications, however, these results are preliminary and further studies are needed to support the findings of this work.
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Objective: to evaluate ability of Nano Ceramic Composite endocrown to withstand occlusal forces when used in the anterior region. Material and Methods: eighty endodontically treated maxillary central incisors teeth were randomly divided into two main groups according to the restoration type. Forty of these teeth were post, core and crown restorations and 40 were endocrown restorations. Then they were divided by halves into two subgroups according to the material used 20 were made with Lava Ultimate and the other 20 with IPS e.max. Each subgroup was then further subdivided into two divisions according to the remaining tooth structure above the CEJ (n = 10): 2 mm and 0.5 mm above the CEJ. After teeth preparation, the restorations were all made by CAD/CAM system (Cerec MCXL). All samples had undergone cyclic fatigue testing, and then loaded to fracture using a universal testing machine. The specimens were measured and statistically analyzed using Mann-Whitney test for comparing the mean changes between the groups. Results: Lava Ultimate showed higher mean fracture load values than IPS e.max specimens. Conclusions: endocrowns were found to be more favorable when used on endodontically treated teeth than the conventional post, core and crown restorations.(AU)
Objetivo: Avaliar a capacidade do compósito nanocerâmico endocrown para suportar forças oclusais quando usado na região anterior. Material e Métodos: Oitenta incisivos centrais superiores tratados endodonticamente foram divididos aleatoriamente em dois grupos principais, de acordo com o tipo de restauração. Quarenta desses dentes receberam restaurações com retentor intrarradicular, núcleo e coroa e 40 receberam restaurações endocrown. Em seguida, foram divididos pela metade em dois subgrupos, de acordo com o material utilizado, sendo 20 confeccionados com Lava Ultimate e os demais 20 com IPS e.max. Cada subgrupo foi posteriormente subdividido em dois, de acordo com a estrutura dentária remanescente acima da JEC (n = 10): 2 mm e 0,5 mm acima do JEC. Após o preparo dos dentes, todas as restaurações foram realizadas pelo sistema CAD/ CAM (Cerec MCXL). Todas as amostras foram submetidas a testes de fadiga cíclica e submetidas ao esforço até a fratura em uma máquina universal de testes. As amostras foram medidas e analisadas estatisticamente pelo teste de MannWhitney para comparação das alterações médias entre os grupos. Resultados: lava Ultimate apresentaram valores médios mais altos de carga até a fratura do que as amostras IPS e.max. Conclusões: as endocrowns mostraram-se mais favoráveis quando utilizadas em dentes tratados endodonticamente do que as restaurações convencionais com retentor intrarradicular, núcleo e coroa.(AU)
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Força de Mordida , Cerâmica , Resinas Compostas , Fraturas ÓsseasRESUMO
Objective: To evaluate the effect of different occlusal preparation designs and CAD/CAM materials on the fracture resistance of maxillary premolars end crowns. Materials and Methods: sixty-four endodontically treated upper first premolars were randomly divided into four groups according to ceramic materials (Vita Enamic and IPS emax CAD) and occlusal preparation designs (Anatomical and horizontal butt joint). After teeth preparation, the restorations were all made by CAD/CAM system (Cerec MCXL). Half of each group had undergone cyclic fatigue testing of 105 cycles with 50N loading force at a frequency of 0.5Hz in a mechatronic chewing simulator machine, and then all samples were loaded to fracture using a universal testing machine with a cross head speed of 0.5 mm/min recording the fracture resistance values in N . The specimens were measured and statistically analyzed using using three-way analyses of variance (ANOVA), followed by serial two-way and one-way ANOVAs at each level of the study. P-values were adjusted for multiple comparisons using BENFORRONI correction and the significance level was set at P ≤ 0.05 for all tests. Results: Vita Enamic endocrowns showed higher fracture resistance values than IPS e max specimens. Conclusions: Vita Enamic endocrowns with anatomical preparations were found to be more favourable restoring endodontically treated maxillary premolars (AU)
Objetivo: Avaliar o efeito de diferentes tipos de preparo oclusal e materiais CAD/CAM na resistência à fratura de coroas endodônticas adesivas em pré-molares. Materiais e Métodos: Sessenta e quatro primeiros pré-molares superiores tratados endodonticamente foram divididos randomicamente em quatro grupos de acordo com os materiais cerâmicos (Vita Enamic e IPS emax CAD) e tipos de preparo oclusal (Recobrimento Incisal Anatômico e Horizontal). Após o preparo dental, as restaurações foram confeccionadas pelo sistema CAD/CAM (Cerec MCXL). Metade de cada grupo foi submetido a testes de fadiga cíclica de 105 ciclos com força de carga de 50N a uma frequência de 0,5Hz em uma máquina simuladora de mastigação mecatrônica, e então todas as amostras foram submetidas a fratura por uma máquina de teste universal com uma velocidade de 0,5 mm / min registrando os valores de resistência à fratura em N. As amostras foram medidas e analisadas estatisticamente usando análises de variância de três fatores (ANOVA), seguidas por ANOVAs de dois fatores e de um fator em cada nível do estudo. Os valores de p foram ajustados para comparações múltiplas usando a correção BENFORRONI e o nível de significância estabelecido foi de P ≤ 0,05 para todos os testes. Resultados: Coroas endodônticas adesivas da Vita Enamic mostraram maiores valores de resistência à fratura do que as amostras de IPS emax. Conclusões: Verificou-se que as coroas endodônticas adesivas da Vita Enamic com preparos com recobrimento incisal anatômico foram mais favoráveis para restaurar os pré-molares superiores tratados endodonticamente (AU)
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Dente Pré-Molar , Desenho Assistido por Computador , Coroas , Restaurações IntracoronáriasRESUMO
BACKGROUND: Different techniques have been described for percutaneous Achilles tendon rupture repair, but no biomechanical evaluation has been performed separately for proximal and distal suturing techniques. The purpose of this study was to biomechanically analyze proximal versus distal percutaneous Achilles suture configurations during cyclic loading and load to failure. METHODS: A simulated, midsubstance rupture was created 6 cm proximal to the calcaneal insertion in fresh-frozen cadaveric Achilles tendons. Fifteen proximal specimens were divided into 3 groups: (A1) triple locking technique, (A2) Bunnell-type technique, and (A3) double Bunnell-type technique. Twelve distal specimens were divided into 2 groups: (B1) triple nonlocking technique and (B2) oblique technique. Repairs were subjected to cyclic testing and load to failure. Load to failure, cause of failure, and tendon elongation were evaluated. RESULTS: None of the proximal specimens and 7/12 of the distal ones failed in cyclic testing. The proximal fixation groups demonstrated significantly more strength than the distal groups (P = .001), achieving up to 710 N of failure load in Group A3. Groups B1and B2 failed on average at 380 N with no difference between them (P > .05). The majority of all repairs failed in the suture-tendon interface. Distal groups had more elongation during cyclic testing (13.7 mm) than proximal groups (9.4 mm) (P = .02). CONCLUSION: The distal fixation site in this Achilles tendon repair was significantly weaker than the proximal fixation site. A proximal modified suture configuration increased resistance to cyclic loading and load to failure significantly. CLINICAL RELEVANCE: A modification can be suggested to improve strength of the Achilles repair.
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Tendão do Calcâneo/cirurgia , Ruptura/cirurgia , Técnicas de Sutura , Resistência à Tração , Fenômenos Biomecânicos , Cadáver , Humanos , Teste de Materiais , Pessoa de Meia-Idade , Estresse MecânicoRESUMO
Aim: The aim of this study was to evaluate the bond strength of artificial teeth to different types of denture base resins when submitted to thermomechanical cycling (TMC). Methods: Sixty artificial mandibular first molars (Trilux, Vipi) were randomly divided into 3 groups according to denture base acrylic resins (Vipi Wave, Vipi Cril, and Vipi Cril Plus, Vipi). The teeth were fixed onto self-polymerizing acrylic resin bars (0.5 cm2 cross-section x 2 cm height), and the set was included in a metal flask using dental stone/silicone. After the dental stone was set, the bar was removed, and the denture base resin was packed and processed according to the group studied (Vipi Wave: 180 W/20 minutes + 540W/5 minutes; Vipi Cril and Vipi Cril Plus: Water bath at 74ºC for 9h). After polymerization, the samples were divided into 2 groups (n=10), according to the TMC treatment received (simulation of 5 years of mastication or not). The samples were submitted to tensile bond strength test (1 mm/min), and the data (MPa) were statistically analyzed (2-way ANOVA, Bonferroni, α=0.05). The fracture interfaces were evaluated using a stereomicroscope (50x). Results: The bond strength results showed no statistically significant difference (p>0.05) between the resins studied. TMC was significant (p<0.05), demonstrating lower values for the bond strength of artificial teeth to Vipi Cril Plus. The predominant fracture type was cohesive in resin. Conclusions: It was concluded that there is no difference in bond strength between artificial teeth and the resins used for denture base. However, TMC decreases the bond strength values of artificial teeth and crosslink thermo-polymerizable acrylic resin
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Dente Artificial , Resinas Acrílicas , Prótese TotalRESUMO
OBJECTIVE: The aim of this study was to analyze failure modes and misfit of abutments with reduced diameter for both cement and screw retentions after cyclic loading. MATERIAL AND METHODS: Forty morse-taper abutment/implant sets of titanium were divided into four groups (N = 10): G4.8S-4.8 abutment with screw-retained crown; G4.8C-4.8 abutment with cemented crown; G3.8S-3.8 abutment with screw-retained crown; and G3.8C-3.8 abutment with cemented crown. Copings were waxed on castable cylinders and cast by oxygen gas flame and injected by centrifugation. After, esthetic veneering ceramic was pressed on these copings for obtaining metalloceramic crowns of upper canine. Cemented crowns were cemented on abutments with provisional cement (Temp Bond NE), and screw-retained crowns were tightened to their abutments with torque recommended by manufacturer (10 N cm). The misfit was measured using a stereomicroscope in a 10× magnification before and after cyclic loading (300,000 cycles). Tests were visually monitored, and failures (decementation, screw loosening and fractures) were registered. Misfit was analyzed by mixed linear model while failure modes by chi-square test (α = 0.05). RESULTS: Cyclic loading affected misfit of 3.8C (P ≤ 0.0001), 3.8S (P = 0.0055) and 4.8C (P = 0.0318), but not of 4.8S (P = 0.1243). No differences were noted between 3.8S with 4.8S before (P = 0.1550) and after (P = 0.9861) cyclic loading, but 3.8C was different from 4.8C only after (P = 0.0015) loading. Comparing different types of retentions at the same diameter abutment, significant difference was noted before and after cyclic loading for 3.8 and 4.8 abutments. Analyzing failure modes, retrievable failures were present at 3.8S and 3.8C groups, while irretrievable were only present at 3.8S. CONCLUSIONS: The cyclic loading decreased misfit of cemented and screw-retained crowns on reduced diameter abutments, and misfit of cemented crowns is greater than screw-retained ones. Abutments of reduced diameter failed more than conventional.
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Parafusos Ósseos , Coroas , Dente Suporte , Cimentos Dentários , Projeto do Implante Dentário-Pivô , Falha de Restauração Dentária , Análise do Estresse Dentário , HumanosRESUMO
PURPOSE: To evaluate the effectiveness of abutment screws coated with liquid Vaseline on the screw-joint stability of yttria-stabilized tetragonal zirconia (Y-TZP) abutment systems. MATERIALS AND METHODS: Forty Y-TZP prefabricated abutments, 20 Neodent and 20 Bionnovation, were tightened to 20 Ncm on their respective external hexagon implants, and divided into four groups (n = 10) according to the screws: coated with Vaseline or uncoated. The removal torque (RT) value of the abutment screw was measured before and after loading. A cyclic loading (0.5 × 106 cycles; 15 Hz) between 11 and 211 N was applied. Means were compared using a repeated-measures ANOVA (α = 0.05). RESULTS: There was no significant difference between coated and uncoated screws (p = 0.822). Significant differences were found between the abutment systems (p < 0.001). There was a significant effect of cyclic loading (p < 0.001). CONCLUSIONS: Coated and uncoated screws presented similar effectiveness in maintaining preload. CLINICAL RELEVANCE: The liquid lubricant used in this study does not influence the stability of Y-TZP single-implant restorations.