Internal fit of two all-ceramic systems and metal-ceramic crowns

OBJECTIVES: The aim of this study was to investigate the internal fit (IF) of glass-infiltrated alumina (ICA - In-Ceram Alumina), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP - IPS e.max ZirCAD), and metal-ceramic (MC - Ni-Cr alloy) crowns. MATERIAL AND METHODS: Sixty standardized resin-tooth replicas of a maxillary first molar were produced for crown placement and divided into 3 groups (n=20 each) according to the core material used (metal, ICA or Y-TZP). The IF of the crowns was measured using the replica technique, which employs a light body polyvinyl siloxane impression material to simulate the cement layer thickness. The data were analyzed according to the surfaces obtained for the occlusal space (OS), axial space (AS) and total mean (TM) using two-way ANOVA with Tukey s multiple comparison test (p<0.05). RESULTS: No differences among the different areas were detected in the MC group. For the Y-TZP and ICA groups, AS was statistically lower than both OS and TM. No differences in AS were observed among the groups. However, OS and TM showed significantly higher values for ICA and Y-TZP groups than MC group. Comparisons of ICA and Y-TZP revealed that OS was significantly lower for Y-TZP group, whereas no differences were observed for TM. CONCLUSIONS: The total mean achieved by all groups was within the range of clinical acceptability. However, the metal-ceramic group demonstrated significantly lower values than the all-ceramic groups, especially in OS

SEM analysis and push-out bond strength of fiberglass posts luted with different cements of glass-ionomer in humid environment: pilot test

The objective of this study was to evaluate the push-out bond strength of fiberglass resin reinforced bonded with five ionomer cements. Also, the interface between cement and dentin was inspected by means of SEM. Fifty human canines were chose after rigorous scrutiny process, endodontically treated and divided randomly into five groups (n = 3) according to cement tested: Group I – Ionoseal (VOCO), Group II – Fugi I (GC), Group III – Fugi II Improved (GC), Group IV – Rely X Luting 2 (3M ESPE), Group V – Ketac Cem (3M ESPE). The post-space was prepared to receive a fiberglass post, which was tried before cementation process. No dentin or post surface pretreatment was carried out. After post bonding, all roots were cross-sectioned to acquire 3 thin-slices (1 mm) from three specific regions of tooth (cervical, medium and apical). A Universal test machine was used to carry out the push-out test with cross-head speed set to 0.5mm/mim. All failed specimens were observed under optical microscope to identify the failure mode. Representative specimens from each group was inspected under SEM. The data were analyzed by Kolmogorov-Smirnov and Levene’s tests and by two-way ANOVA, and Tukey’s port hoc test at a significance level of 5%. It was compared the images obtained for determination of types of failures more occurred in different levels. SEM inspection displayed that all cements filled the space between post and dentin, however, some imperfections such bubles and voids were noticed in all groups in some degree of extension. The push-out bond strength showed that cement Ketac Cem presented significant higher results when compared to the Ionoseal (P = 0.02). There were no statistical significant differences among other cements

Evaluation of failure mode of ceramic crowns with and without framework design modification.

Coroas cerâmicas têm sido amplamente utilizadas, entretanto, problemas relacionados com a fratura destes materiais persistem principalmente nos sistemas ceramocerâmicos na região de molar. As hipóteses nulas testadas foram que o desenho da infraestrutura e o tipo de material não terão efeito significante na resistência à fadiga. Coroas metalocerâmicas e ceramocerâmicas foram fabricadas sobre o preparo de um molar superior, o qual reproduzia a complexa morfologia dos preparos dentários. Quatro grupos foram estabelecidos (n=10 por grupo) baseados no desenho das infraestruturas (padrão ou alterada) das coroas metalocerâmicas (MC) e das ceramocerâmicas (CC), denominadas de MCSA e CCSA para as I.E. com desenho padrão e MCCA e CCCA para as com alteração no seu desenho. As infraestruturas com desenho padrão apresentaram espessura de 0,5mm em todas as suas paredes e as com alteração no desenho apresentaram a cinta lingual com 2,0mm de altura e postes proximais com 3,5mm de altura e as demais áreas com 0,5mm de espessura. As coroas ceramocerâmicas consistiam do sistema à base de alumina (In-Ceram Alumina slip cast) e as infraestruturas das coroas metalocerâmicas foram fabricadas com metal não nobre (Ni-Cr). Todas as coroas foram cimentadas com cimento resinoso Rely X ARC sobre uma réplica do preparo de resina composta, a qual teve a proposta de simular o módulo de elasticidade encontrado na dentina. Estas coroas foram submetidas ao teste de resistência à fadiga, ciclagem dinâmica, por 106 ciclos ou até que qualquer tipo de fratura fosse observada, com carga variando entre 30-300N. A força foi aplicada axialmente entre as vertentes palatina e vestibular, com endentador metálico esférico. Em intervalos de 125.000 as coroas eram verificadas à procura de danos com auxílio de estereomicroscopia. As coroas que não sofreram fraturas foram polidas sequencialmente e cada corpo de prova recebeu escores de acordo com o tipo de falha apresentada. O teste Kruskal Wallis foi utilizado para verificar se houve diferença estatisticamente significante entre os materiais e o teste de Student-Newman-Keusl foi utilizado para as comparações múltiplas. Diferenças estatisticamente significante foi encontrada entre materiais e desenhos, entretanto, os grupos com I.E. metálica (MCCA e MCSA) não apresentaram diferença estatisticamente significante. O grupo CCCA mostrou diferença estatisticamente significante em relação ao grupo CCSA. A presença do metal na infraestrutura foi preponderante na resistência à fadiga. A alteração no desenho da infraestrutura cerâmica provou ser superior em relação ao desenho sem alteração.Ceramic crowns have been widely used, however, problems related to brittle fracture of these materials persist, especially in the posterior area. The present study tested the null hypothesis that there were no differences in fatigue resistance related to the framework design as well as to the materials used. One maxillary molar was prepared, reproducing the complex morphology of a dental preparation, to receive metal-ceramic and all-ceramic crowns. Four groups (n=10) were established based on framework designs (standard and modified) for metal-ceramic (MC) and all-ceramic (CC) crowns, named as MCSA and CCSA for standard framework designs and MCCA and CCCA for the proposed framework design modifications. On the standard design, frameworks presented 0.5mm thick walls and those with design modification a 0.5mm thick framework with a vertical increase of 2.0mm lingual and 3.5mm proximal walls. All-ceramic frameworks were made with In-Ceram Alumina slip cast and the metal-ceramic frameworks were made with nickel-chromium alloy. All crowns were cemented with resin cement (Rely X ARC) on resin composite replicas, witch have an elastic modulus similar to dentin. They were subjected to dynamic cycling fatigue test (106 cycles or until fracture), at ranging load of 30-300N. Load was located between the buccal and lingual cuspals of the crowns. At 125.000 cycles intervals, crowns were analysed under a stereomicroscopy to search for damages. Crowns without fracture were polished sequentially and received scores according to the failure mode. Kruskal Wallis test was used to check if there were a significant differences between the framework design and materials (metal and ceramic) and the Student-Newman-Keuls was used for multiple comparisons. Significant differences were found between materials and designs, however, both metal frameworks (MCCA e MCSA) were similar. CCCA group showed higher survival than CCSA group. The metal presence in the framework seemed to improve the resistance to fatigue test. However, the design modification in ceramics achieved better results than the standard design

Effect of indenter material on reliability of all-ceramic crowns

A incompatibilidade entre o módulo de elasticidade (E) do endentador e dos materiais cerâmicos durante os testes de fadiga tem gerado controvérsias. Foram testadas as hipóteses que coroas totalmente cerâmicas apresentarão confiabilidade à fadiga acelerada progressiva do tipo step-stress (hipótese 1) e modos de falha (hipótese 2) similares, quando dois endentadores, um à base de carboneto de tungstênio (WC, E = 600 GPa) e outro de cerâmica esteatite [SB, E = 90 GPa] forem utilizados para transferir a carga. Para avaliar o efeito dos endentadores, um preparo para coroa total em um molar inferior foi realizado. A partir deste modelo mestre, 42 coroas à base de Y-TZP e 42 réplicas em resina composta foram produzidas. As réplicas em resina foram envelhecidas por 30 dias. Todas as coroas foram cimentadas sobre estas réplicas com cimento autoadesivo (Rely X Unicem - 3M/ESPE, St. Paul, EUA) e divididas em dois grupos de acordo com o endentador (WC ou SB). As coroas foram submetidas tanto ao teste de resistência à fratura (n = 3 por grupo), empregado para determinar os perfis de carga (leve, moderado e agressivo) quanto à fadiga (n = 18 por grupo), utilizando um endentador novo para cada coroa. Impressões de todas as coroas e endentadores submetidos ao perfil leve foram obtidas, em pontos específicos do perfil (0, 40k, e, 80k 120k, 160k), vazadas com resina epóxi e avaliadas sob MEV, com a finalidade de inspecionar a morfologia e medir a área endentada. O Use level Probability mostrou sobreposição entre os intervalos de confiança, indicando que não houve diferença significante entre os grupos, independente do critério de falha. O módulo de Weibull Beta (&#x3B2;) calculado para IA (análise inicial) foi de 1,99 e 1,67 para SB e WC, respectivamente, apontando que a fadiga acelerou o fracasso em ambos os grupos. Este não foi o caso para os valores de &#x3B2; para a análise de FA (análise final) (SB = 1,1 e WC = 0,72), revelando que a carga pode ter influenciado sozinha o mecanismo de falha. Ambos os endentadores produziram padrões semelhantes de desgaste/danos nas coroas. A análise fractográfica revelou modos de falhas concorrentes, mas as trincas tipo cone parciais foram as mais dominantes em ambos os grupos. As medições das áreas endentadas mostraram diferença estatística entre os grupos (SB vs. WC) (p <0,05). No geral, o endentador WC exibiu área maior do que a produzida pelo SB. O endentador mais compatível (SB) com a superfície cerâmica produziu confiabilidade e modos de falhas semelhantes ao ser comparada com o WC; assim, as hipóteses 1 e 2 foram aceitas.Concerns about elastic modulus (E) mismatch between indenter and ceramic materials during fatigue testing have generated controversy. We hypothesized that all-ceramic crowns will exhibit similar step-stress sliding contact fatigue reliability (hypothesis 1) and failure characteristics (hypothesis 2) when using high stiffness tungsten carbide (WC, E = 600 GPa) vs enamel like steatite (SB, E = 90 GPa) indenters. To evaluate the effect of indenters, a preparation for a full crown was made on a first lower molar. From this master die 42 Y-TZPveneered all-ceramic crowns and 42 tooth-resin réplicas were made. Crowns were cemented onto the aged (30 days) tooth-resin réplicas with self-adhesive resin-based cement (Rely X UniCem - 3M/ESPE, St. Paul, USA). After, crowns were divided into two groups according to indenter (WC or SB). Specimens were subject to single-load to fracture (n = 3 per indenter type) to determine the step-stress profiles (mild, moderate, and aggressive) and to mouthmotion step-stress fatigue-tested (n = 18 per indenter type). Two failure modes were determined (inital analysis [IA] and final analysis [FA]). For each crown, a new indenter was used and labelled accordingly for surface damage evaluation. Impressions from all crowns subjected to mild profile were taken following a pre-arranged number of cycles (0, 40k, 80k, 120k e, 160k), poured with epoxy resin and SEM evaluated to inspect the morphology and to measure the indented area. The use level probability plots of the fatigue data showed overlap between the 2-sided 90% confidence bounds. The calculated Weibull Beta (&#x3B2;) for IA was 1.99 and 1.67 for SB and WC, respectively, pointing out that fatigue accelerated the failure in both groups. This was not the case for the &#x3B2; values for the FA analysis (SB = 1.1 and WC = 0.72), revealing tha the load alone dicted the failure mechanism. Both indenters produced similar pattern of wear on crown surfaces. Fractographic landmarks showed competing failure modes, but partial cone cracks were the most dominant for both groups. The indented area measurements showed statistical difference between groups (SB vs WC) (p < .05). Overall, the WC indenter displayed the largest area than SB, except when 120k was taken into account. The more compliant SB indenter led to similar reliability and failure modes to WC (hypotheses 1 and 2 accepted)

Challenges in reconstructing an isolated anterior tooth with a metal-free crown

Introduction: Currently, new esthetic treatments are available to the dentist due to the advent of ceramic-ceramic prostheses. A new option has become part of daily clinical practice, with the promise of esthetic optimization through the elimination of metal in prosthetic crowns. The translucence of these new systems allows the transmission of light through the tooth structure, minimizing gingival darkness and producing a vibrant and natural appearance. Case Report: The patient, 30 years old, female, showed with a fractured tooth crown at the cervical level in the right lateral incisive. It was observed that the tooth had prior adequate endodontic treatment. A metal-free restorative system was selected. A plaster model was obtained for subsequent tooth preparative scanning and manufacture of ceramic framework. After receiving the framework, adjustments were made and the color choice of covering ceramic, following the protocol of choice for a chroma suboptimal aiming further characterization. After the ceramics application, adjustments in shape, texture, and occlusion were made. The crown was characterized by exterior paint, getting a favorable result, restoring esthetics and function. Discussion : The metal-free systems are a viable alternative to the restorative treatment when esthetics is desired, allowing a natural and harmonious smile, combined with the reliability of the restorative material

Bone-Forming Capabilities of a Newly Developed NanoHA Composite Alloplast Infused with Collagen: A Pilot Study in the Sheep Mandible

Lateral or vertical bone augmentation has always been a challenge, since the site is exposed to constant pressure from the soft tissue, and blood supply only exists from the donor site. Although, for such clinical cases, onlay grafting with autogenous bone is commonly selected, the invasiveness of the secondary surgical site and the relatively fast resorption rate have been reported as a drawback, which motivated the investigation of alternative approaches. This study evaluated the bone-forming capability of a novel nanoHA alloplast infused with collagen graft material made from biodegradable polylactic acid/polyglycolic acid versus a control graft material with the same synthesized alloplast without the nanoHA component and collagen infiltration. The status of newly formed bone and the resorption of the graft material were evaluated at 6 weeks in vivo histologically and three dimensionally by means of 3D microcomputed tomography. The histologic observation showed that newly formed bone ingrowth and internal resorption of the block were observed for the experimental blocks, whereas for the control blocks less bone ingrowth occurred along with lower resorption rate of the block material. The three-dimensional observation indicated that the experimental block maintained the external geometry, but at the same time successfully altered the graft material into bone. It is suggested that the combination of numerous factors contributed to the bone ingrowth and the novel development could be an alternative bone grafting choice

Push-out bond strengths of different dental cements used to cement glass fiber posts

Statement of problem: Since the introduction of glass fiber posts, irreversible vertical root fractures have become a rare occurrence; however, adhesive failure has become the primary failure mode. Purpose: The purpose of this study was to evaluate the push-out bond strength of glass fiber posts cemented with different luting agents on 3 segments of the root. Material and methods: Eighty human maxillary canines with similar root lengths were randomly divided into 8 groups (n=10) according to the cement assessed (Rely X luting, Luting and Lining, Ketac Cem, Rely X ARC, Biscem, Duo-link, Rely X U100, and Variolink II). After standardized post space preparation, the root dentin was pretreated for dualpolymerizing resin cements and untreated for the other cements. The mixed luting cement paste was inserted into post spaces with a spiral file and applied to the post surface that was seated into the canal. After 7 days, the teeth were sectioned perpendicular to their long axis into 1-mm-thick sections. The push-out test was performed at a speed of 0.5 mm/min until extrusion of the post occurred. The results were evaluated by 2-way ANOVA and the all pairwise multiple comparison procedures (Tukey test) (?=.05). Results: ANOVA showed that the type of interaction between cement and root location significantly influenced the push-out strength (P<.05). The highest push-out strength results with root location were obtained with Luting and Lining (S3) (19.5 ±4.9 MPa), Ketac Cem (S2) (18.6 ±5.5 MPa), and Luting and Lining (S1) (18.0 ±7.6 MPa). The lowest mean values were recorded with Variolink II (S1) (4.6 ±4.0 MPa), Variolink II (S2) (1.6 ±1.5 MPa), and Rely X ARC (S3) (0.9 ±1.1 MPa). Conclusions: Self-adhesive cements and glass ionomer cements showed significantly higher values compared to dual-polymerizing resin cements. In all root segments, dual-polymerizing resin cements provided significantly lower bond strength. Significant differences among root segments were found only for Duo-link cement.Significant differences among root segments were found only for Duo-link cemen