Lifetime prediction of veneered versus monolithic lithium disilicate crowns loaded on marginal ridges.

OBJECTIVE: To evaluate the probability of survival of monolithic and porcelain veneered lithium disilicate crowns comprised by a conventional or modified core when loaded on marginal ridges. METHODS: Lithium disilicate molar crowns (n=30) were fabricated to be tested at mesial and distal marginal ridges and were divided as follows: (1) bilayered crowns with even-thickness 0.5mm framework (Bi-EV); (2) bilayered crowns with modified core design (Bi-M-lingual collar connected to proximal struts), and: (3) monolithic crowns (MON). After adhesively cemented onto composite-resin prepared replicas, mesial and distal marginal ridges of each crown (n=20) were individually cyclic loaded in water (30-300N) with a ceramic indenter at 2Hz until fracture. The 2-parameter Weibull was used to calculate the probability of survival (reliability) (90% 2-sided confidence bounds) at 1, 2, and 3 million cycles and mean life. RESULTS: The reliability at 1 and 2 million cycles was significantly higher for MON (47% and 19%) compared to Bi-EV (20% and 4%) and Bi-M (17% and 2%). No statistical difference was found between bilayered groups. Only the MON group presented crown survival (7%) at 3 million cycles. The mean life was highest for MON (1.73E+06), lowest for Bi-M (573,384) and intermediate for Bi-E (619,774). Fractographic analysis showed that the fracture originated at the occlusal surface. The highest reliability was found for MON crowns. The modified framework design did not improve the fatigue life of crowns. SIGNIFICANCE: Monolithic lithium disilicate crowns presented higher probability of survival and mean life than bilayered crowns with modified framework design when loaded at marginal ridges.

Effect of aging and testing method on bond strength of CAD/CAM fiber-reinforced composite to dentin.

OBJECTIVES: To evaluate and compare the outcomes of shear (S) and microtensile (µT) bond strength tests of CAD/CAM fiber-reinforced composite (FRC) to dentin. Aging with either fatigue or thermocycling were conducted for comparison with baseline microtensile group. METHODS: CAD/CAM FRC (Trinia, Bicon LLC, Boston, USA) blocks were milled to 3-mm diameter cylinders for shear and to blocks (5×5×5mm) for µT. Sixty extracted human molars were flattened to obtain dentin surfaces and randomly divided in four groups (n=15): (1) SC: samples tested in shear 24h after bonding; (2) µTC: samples tested in µT 24h after bonding); (3) µTF: samples submitted to mechanical fatigue prior to µT test, and; (4) µTT: thermocycling prior to µT test. Bonding system was applied onto the FRC material (Cera-Resin Bond, CRB, Shofu Dental, Kyoto, Japan). A conventional three-step adhesive system (All-bond 3, Bisco, Schaumburg, USA) was use with a self-cure resin cement (C&B resin cement, Bisco, Schaumburg, USA). Bond strength tests were conducted at 0.75mm/min and data analyzed using Weibull distribution (p<0.05). RESULTS: Weibull contour plots showed a significantly lower characteristic strength (η) and Weibull modulus (m) for SC (η=6.9MPa and m=1.4) compared to µTC (η=20.9MPa and m=4.5). Fatigued and thermocycled µT groups presented significantly reduced characteristic strength (η=3.1MPa and η=4.1MPa, respectively) compared to µTC. Weibull modulus was significantly reduced only for SC and µTF groups compared µTC. Failure predominantly occurred at the cement/FRC interface. SIGNIFICANCE: FRC bonded to dentin samples presented lower Weibull modulus and characteristic bond strength when immediately tested in shear compared to microtensile. Aging through thermocycling or mechanical fatigue significantly reduced the characteristic strength in microtensile testing, with the majority of failures emerging between restoration material and cement interface.

Lifetime prediction of zirconia and metal ceramic crowns loaded on marginal ridges.

OBJECTIVE: To evaluate the fatigue life of zirconia-veneered and metal-ceramic crowns comprised by an even thickness or a modified framework design when loaded on marginal ridges. METHODS: Eighty marginal ridges were present after fabrication of forty molar crowns cemented onto composite-resin replicas and divided (n=20/each), in the following groups: metal-ceramic with even thickness (MCev) or with a modified framework design (MCm, lingual collar with proximal struts); porcelain-fused to zirconia with even thickness (PFZev) or with the modified framework design (PFZm). Each marginal ridge (mesial and distal) was subjected to cyclic loading separately with a lithium disilicate indenter for 106 cycles or until fracture. Kruskal-Wallis and Wilcoxon matched pair test (p<0.05) evaluated both marginal ridges. Every 125,000 cycles, the test was interrupted for damage inspection. Weibull distribution (90% confidence bounds) determined the probability of survival (reliability). RESULTS: Weibull 2-parameter contour-plot showed significantly higher fatigue life for PFZev compared to MC, and comparable with PFZm. A significant decrease in reliability was observed between groups from 625,000 until 106 cycles. Metal-ceramic groups presented significantly lower probability of survival at 106 cycles (MCev=0.66% and MCm=4.73%) compared to PFZm (23.41%) and PFZev (36.68%). Fractographic marks showed a consistent fracture origin and direction of crack propagation. Reliability was higher for porcelain-fused to zirconia than for metal ceramic crowns, regardless of framework design. SIGNIFICANCE: Zirconia-veneered crowns presented decreased fracture rates compared to metal ceramics, even when loaded at marginal ridges, regardless of framework design.

Avaliação da resistência à fadiga e modo de falha de coroas de dissilicato de lítio com aplicação de carga nas cristas marginais / Fatigue lifetime and failure mode of lithium disilicate crowns during load application in marginal ridges

As cerâmicas à base de dissilicato de lítio apresentam propriedades mecânicas, resistência química, biocompatibilidade, baixo índice de acúmulo de placa e resultados estéticos favoráveis. Entretanto, sua resistência à fadiga e probabilidade de sobrevida (confiabilidade) em sua forma estratificada e monolítica ainda é pouco conhecida. Este estudo tem como objetivo investigar a confiabilidade e o modo de falha das coroas estratificadas de dissilicato de lítio com e sem modificação do desenho da infraestrutura e de coroas monolíticas quando submetidas ao ensaio de fadiga por intermédio da ciclagem dinâmica em água. Trinta coroas foram divididas em 3 grupos: IEC (coroas estratificadas com infraestrutura convencional), IEM (coroas estratificadas com infraestrutura modificada) e MON (coroas monolíticas). Para os grupos IEC e IEM as infraestruturas apresentavam espessura de 0,8 mm. No entanto, no desenho modificado era adicionado uma cinta lingual de 2 mm de altura conectada a postes proximais de 3,5 mm de altura, ambos com 1,3 mm de espessura. As MON eram compostas inteiramente de dissilicato de lítio e apresentavam espessura oclusal de 1,5 mm. As coroas foram cimentadas em troqueis de resina composta e submetidas a ciclagem dinâmica em água (30-300 N). Um endentador monolítico de dissilicato de lítio aplicava carga axial sobre a crista marginal mesial até a fratura, e posteriormente na crista distal. Ao final, as coroas eram analisadas em estereomicroscópio e no microscópico eletrônica de varredura (MEV) para caracterização e classificação dos danos. As falhas encontradas nas coroas foram registradas a cada 125.000 ciclos. A distribuição Weibull a 2 parâmetros (Synthesis 9, Weibull ++; Reliasoft, Tucson, AZ, USA) foi utilizada para calculo da probabilidade de sobrevida em 1, 2 e 3 milhões de ciclos. Comparações entre os grupos também foram realizadas com o módulo de Weibull e a resistência característica (número de ciclos decorrido até a fratura)...

Lithium disilicate glass-ceramic provides desirable mechanical properties, chemical resistance, biocompatibility, diminished plaque accumulation, esthetics, and favorable esthetic results. However, the fatigue life and probability of survival (reliability) of lithium disilicate in its monolithic or layered form is still poorly understood. This study aimed to investigate the reliability and failure modes of porcelain veneered lithium disilicate crowns with and without core design modification, and of monolithic crowns when subjected to cyclic fatigue in water. Thirty lithium disilicate molars crowns were made and divided into 3 groups: IEC (bilayer crown with even thickness coping, i.e. conventional core), IEM (bilayer crowns with modified core design) and MON (monolithic crowns). For groups IEC and IEM, copings presented an even thickness of 0.8 mm and the modified design consisted of 1.3 mm thickness with a lingual margin of 2.0mm height connected to full contour proximal struts of 3.5 mm height. Monolithic crowns had an occlusal thickness of 1.5 mm. Crows were luted on composite resin abutment replicas and subjected to cyclic fatigue in water (30-300 N). A monolithic indenter of lithium disilicate was used to deliver the load on the mesial marginal ridge until failure, then the same procedure was performed in the distal ridge. For failure characterization crowns were analyzed in stereomicroscope and scanning electron microscope (SEM). Failure inspection was performed every 125,000 cycles. The 2-parameter Weibull distribution (Synthesis 9, Weibull ++; Reliasoft, Tucson, AZ, USA) was used calculate the probability of survival at 1, 2, and 3 million cycles. Comparisons between groups were also made for Weibull modulus and characteristic strength (number of cycles elapsed until failure). At both 1 and 2 million cycles, reliability was significantly lower for IEM relative to MON and IEC showed no difference between the IEM and MON. At 3 million cycles...

Avaliação da resistência à fadiga e modo de falha de coroas de dissilicato de lítio com aplicação de carga nas cristas marginais / Fatigue lifetime and failure mode of lithium disilicate crowns during load application in marginal ridges

As cerâmicas à base de dissilicato de lítio apresentam propriedades mecânicas, resistência química, biocompatibilidade, baixo índice de acúmulo de placa e resultados estéticos favoráveis. Entretanto, sua resistência à fadiga e probabilidade de sobrevida (confiabilidade) em sua forma estratificada e monolítica ainda é pouco conhecida. Este estudo tem como objetivo investigar a confiabilidade e o modo de falha das coroas estratificadas de dissilicato de lítio com e sem modificação do desenho da infraestrutura e de coroas monolíticas quando submetidas ao ensaio de fadiga por intermédio da ciclagem dinâmica em água. Trinta coroas foram divididas em 3 grupos: IEC (coroas estratificadas com infraestrutura convencional), IEM (coroas estratificadas com infraestrutura modificada) e MON (coroas monolíticas). Para os grupos IEC e IEM as infraestruturas apresentavam espessura de 0,8 mm. No entanto, no desenho modificado era adicionado uma cinta lingual de 2 mm de altura conectada a postes proximais de 3,5 mm de altura, ambos com 1,3 mm de espessura. As MON eram compostas inteiramente de dissilicato de lítio e apresentavam espessura oclusal de 1,5 mm. As coroas foram cimentadas em troqueis de resina composta e submetidas a ciclagem dinâmica em água (30-300 N). Um endentador monolítico de dissilicato de lítio aplicava carga axial sobre a crista marginal mesial até a fratura, e posteriormente na crista distal. Ao final, as coroas eram analisadas em estereomicroscópio e no microscópico eletrônica de varredura (MEV) para caracterização e classificação dos danos. As falhas encontradas nas coroas foram registradas a cada 125.000 ciclos. A distribuição Weibull a 2 parâmetros (Synthesis 9, Weibull ++; Reliasoft, Tucson, AZ, USA) foi utilizada para calculo da probabilidade de sobrevida em 1, 2 e 3 milhões de ciclos. Comparações entre os grupos também foram realizadas com o módulo de Weibull e a resistência característica (número de ciclos decorrido até a fratura). Tanto em 1...

Lithium disilicate glass-ceramic provides desirable mechanical properties, chemical resistance, biocompatibility, diminished plaque accumulation, esthetics, and favorable esthetic results. However, the fatigue life and probability of survival (reliability) of lithium disilicate in its monolithic or layered form is still poorly understood. This study aimed to investigate the reliability and failure modes of porcelain veneered lithium disilicate crowns with and without core design modification, and of monolithic crowns when subjected to cyclic fatigue in water. Thirty lithium disilicate molars crowns were made and divided into 3 groups: IEC (bilayer crown with even thickness coping, i.e. conventional core), IEM (bilayer crowns with modified core design) and MON (monolithic crowns). For groups IEC and IEM, copings presented an even thickness of 0.8 mm and the modified design consisted of 1.3 mm thickness with a lingual margin of 2.0mm height connected to full contour proximal struts of 3.5 mm height. Monolithic crowns had an occlusal thickness of 1.5 mm. Crows were luted on composite resin abutment replicas and subjected to cyclic fatigue in water (30-300 N). A monolithic indenter of lithium disilicate was used to deliver the load on the mesial marginal ridge until failure, then the same procedure was performed in the distal ridge. For failure characterization crowns were analyzed in stereomicroscope and scanning electron microscope (SEM). Failure inspection was performed every 125,000 cycles. The 2-parameter Weibull distribution (Synthesis 9, Weibull ++; Reliasoft, Tucson, AZ, USA) was used calculate the probability of survival at 1, 2, and 3 million cycles. Comparisons between groups were also made for Weibull modulus and characteristic strength (number of cycles elapsed until failure). At both 1 and 2 million cycles, reliability was significantly lower for IEM relative to MON and IEC showed no difference between the IEM and MON. At 3 million cycles, only...

Fracture resistance of endodontically treated teeth restored with different intraradicular posts with different lengths

Aim: This study compared the resistance to fracture of endodontically treated teeth restored with different intraradicular posts with different lengths and full coverage metallic crowns. Methods: Sixty extracted human canine teeth were randomly divided into 6 groups. Groups CP5, CP75 and CP10 were restored using custom cast post and core (CP) and groups PF5, PF75 and PF10 were restored with provisional pre-fabricated tin post (PF) and composite resin core at 5 mm, 7.5mm and 10 mm of intraradicular length, respectively. The specimens were submitted to dynamic cyclic loading and those that resisted to this load were submitted to load compression using auniversal testing machine. Compressive load was applied at a 45-degree angle to the long axis of the tooth until failure. Results: Kruskal-Wallis one-way analysis of variance by ranks showed statistically significant differences among the groups (p<0.0001). However, when the means were compared using the Tukey’s test, significant differences were noted between groups CP5 and CP10 and between groups CP10 and PF5. All groups presented root fractures and post displacements during mechanical cycling. All teeth in groups CP5 and PF5 failed the dynamic cycling test. Conclusions: This study showed that increasing intraradicular post length also increases resistance to fracture of endodontically treated teeth. On the other hand, most endodontically treated teeth restored with pre-fabricated tin posts (provisional posts) failed in thedynamic cycling test.

Análise de resistência à tração de pinos de fibra de vidro cimentados com diferentes cimentos de ionômero de vidro através do teste pull-out / Evaluation of tensile strength of fiberglass posts cemented with different glass ionomer cements through pull-out-test

Para que se consiga resistência e retenção de pinos intrarradiculares é essencial a adequada seleção do agente cimentante. Objetivo: analisar diferentes tipos de cimento de ionômero de vidro utilizados na cimentação de pinos intrarradiculares de fibra de vidro, o método através do teste de resistência à tração pull-out. Métodos: Foram cimentados pinos de fibra de vidro em 50 caninos humanos, divididos nos seguintes grupos (n = 10): Grupo I ? Ionoseal (Voco), Grupo II ? Lining and Cement (GC), Grupo III ? Fuji II Improved (GC), Grupo IV ? Rely X Luting 2 (3M Espe), Grupo V ? Ketac Cem (3M Espe). Resultados: o teste Anova mostrou diferença significativa entre os grupos. O teste de Tukey mostrou que o Lining and Cement foi estatisticamente mais resistente que o Ionoseal (p < 0,05). Conclusão: assim, analisando-se os resultados, pode-se concluir que avaliando a resistência à tração dos pinos de fibra de vidro cimentados com diferentes cimentos de ionômero de vidro através do teste pull-out o cimento de ionômero de vidro convencional Lining and Cement se mostrou superior aos outros cimentos.

Próteses parciais removíveis não convencionais parte II / Non-conventional removable partial denture part II

Dentes perdidos podem ser melhores substituídosempregando próteses fixas (dento ouimplanto suportadas). Contudo, algumas limitaçõescomo fatores econômicos, culturais, sociais,distribuição dos dentes, extensão do espaçoprotético e espessura do rebordo, podemlimitar o emprego dessas próteses. Dessa forma,a prótese parcial removível (PPR) torna-se umaalternativa segura e confiável quando a prótesefixa não pode ser indicada. Embora apresentedesvantagens, a PPR convencional preenche todosos requisitos para reabilitar qualquer áreaedêntula, pois recupera dentes e estruturas associadasperdidas (osso e tecidos moles). Entretanto,algumas alterações como modificaçõesdo desenho da infraestrutura, mudança do eixode inserção, tipo de dente usado na prótese(artificial ou natural), dentre outras, podem serrealizadas para melhorar o conforto, satisfaçãoe estética do paciente. Nesses casos, há a transformaçãoda PPR convencional em não convencional.Este trabalho tem objetivo de revisaras categorias de PPR não convencionais, assimcomo suas vantagens, desvantagens, indicaçõese contraindicações, na esperança que mais dentistaspossam considerar seu uso quando a situaçãoaparecer.

Fixed partial prostheses (tooth or implant based)are considerated as the best choice to replacemissing teeth. However, some clinical (teethdistribution, prosthetic space extension and residualbone thickness) or individual (economical,cultural and social factors) conditions may limitits indication. In such situations, the removablepartial denture (RPD) is a reliable alternative.Although the conventional RPD shows somedisadvantages, it presents all requirements torehabilitate any edentulous space. Moreover,RPD replaces both teeth and adjacent structures(soft and hard tissues) missed. Nevertheless,in order to delivery esthetic, comfort andself-confidence to patient, some specific clinicalconditions require a non-conventional RPD. Thisprosthesis is characterized by presenting a changedframework design, or a different insertionpath, or due to its association with implants,among others. Thus, understanding the nonconventionalRPDs concept is a subject matterimportant and pertinent. The present studysought to review the relevant literature aboutnon-conventional RPDs, including vantages, disadvantages,indications and contraindications,expecting that more dentists may consider thenon-conventional RPD as a treatment option.

Próteses parciais removíveis não convencionais - parte I / Non conventional removable partial denture - part I

Dentes perdidos podem ser melhor substituídos empregando próteses fixas dento ou implanto suportadas. Contudo, algumas limitações como fatores econômicos, culturais, sociais, saúde geral, distribuição dos dentes, extensão do espaço protético e espessura do rebordo, podem limitar o emprego dessas próteses. Desta forma, a prótese parcial removível (PPR) torna-se uma alternativa segura e confiável quando a prótese fixa não pode ser indicada. Embora apresente desvantagens, a PPR convencional preenche todos os requisitos para reabilitar qualquer área edêntula, pois recupera dentes e estruturas associadas perdidas (osso e tecidos moles). Entretanto, algumas alterações como modificações do desenho da infraestrutura, mudança do eixo de inserção, combinação com implantes, tipo de dentes utilizados na prótese (artificial ou natural), dentre outras, podem ser realizadas para melhorar o conforto, satisfação e estética do paciente. Nesses casos há a transformação da PPR convencional em não convencional. Este trabalho tem como objetivo revisar os tipos de PPRs não convencionais, assim como suas vantagens, desvantagens, indicações e contra-indicações, na esperança de que mais cirurgiões-dentistas (CD) possam considerar seu uso quando a situação aparecer

Fixed partial prostheses (tooth or implant based) are considered as the best choice to replace missing teeth. However, some clinical (teeth distribution, prosthetic space extension and residual bone thickness) or individual (economical, cultural and social factors) conditions may limit its indication. In such situations, the removable partial denture (RPD) is a reliable alternative. Although the conventional RPD shows some disadvantages, it presents all requirements to rehabilitate any edentulous space. Moreover, RPD replaces both teeth and adjacent structures (soft and hard tissues) missed. Nevertheless, in order to delivery esthetic, comfort and self-confidence to patient, some specific clinical conditions require a non-conventional RPD. This prosthesis is characterized by presenting a changed framework design, or a different insertion path, or due to its association with implants, among others. Thus, understanding the non-conventional RPDs concept is a subject matter important and pertinent. The present study sought to review the relevant literature about non-conventional RPDs, including vantages, disadvantages, indications and contraindications, expecting that more dentists may consider the non conventional RPD as a treatment option

Avaliação do modo de falha de coroas ceramocerâmicas de zircônia em função do protocolo de resfriamento e do desenho de infraestrutura / Evaluation of the zirconia crowns failure mode depending on cooling protocol and framework design

As excelentes propriedades mecânicas da zircônia como elevada resistência flexural e tenacidade à fratura fez com ela fosse o material cerâmico de eleição para as coroas e próteses fixas posteriores. Porém, mesmo com elevadas propriedades mecânicas os problemas relacionados a fratura ainda persistem. Variáveis como a baixa condutibilidade térmica da zircônia e a falta de suporte das infraestruturas às porcelanas são indicadas como possíveis causas. O presente estudo teve o objetivo de verificar se a modificação do desenho da infraestrutura e a alteração do protocolo de resfriamento durante a fase de glaze são capazes de melhorar a resistência das coroas ceramocerâmicas com infraestruturas de zircônia. Quarenta coroas unitárias com infraestruturas de zircônia (IPS e.max ZirCAD) na forma de molares foram confeccionadas sobre preparos padronizados e divididos em 4 grupos: ZrCRP (coroas com infraestruturas convencionais e resfriamento padrão), ZrMRP (coroas com desenho de infraestrutura modificado e resfriamento padrão), ZrCRL (coroas com infraestruturas convencionais e resfriamento lento) e ZrMRL (coroas com desenho de infraestrutura modificado e resfriamento lento). As infraestruturas com desenho convencional apresentavam espessura uniforme de 0,5 mm e as com modificação apresentavam espessura de 0,5 mm acrescentadas da cinta lingual de 2,0 mm de altura e postes proximais com 3,5 mm de altura, ambos com 1 mm de espessura. As coroas foram cimentadas com cimento resinoso (Rely X ARC) sobre réplicas de resina composta do preparo. Estas coroas foram submetidas ao teste de resistência à fadiga por meio da ciclagem dinâmica em água (106 ciclos ou até a fratura com carga variando de 30-300 N). Um endentador de aço inoxidável aplicava a carga axialmente entre as duas vertentes linguais e vestibulares. A ciclagem era interrompida em intervalos de 125 mil ciclos a procura de danos com auxílio de estereomicroscopia. Ao final, as coroas fraturadas eram submetidas a...

The exceptional mechanical proprieties such as high flexural strength and fracture toughness make Zirconia anatural choice as material for posterior dental prosthesis. However, even with these properties, problems related to fracture persist. Low heat conductibility of zirconia and lack of support for veneering porcelain may be pointed as possible causes. The proposed study investigate if modifications on core design and cooling rate protocol during glaze firing are able to improve allceramic zirconia reinforced crows resistance. Forty molar zirconia reinforced single crowns (IPS e.max ZirCAD) were manufactured from standard abutment and divided in four groups: ZrCRP (conventional core design and standard cooling rates), ZrMRP (modified core design and standard cooling rates), ZrCRL (conventional core design and slow cooling rates) e ZrMRL (modified core design and slow cooling rates) (Até aqui ta bem escrito). The standards design Cores presented uniform thickness of 0,5 mm and the modified design Cores consisted of 0.5 mm thickness with a thick lingual margin of 2.0mm height, connecting to full contour proximal struts of 3.5 mm height, remembering that both the standard and the modified Core possess 1 mm of thick. Crows were luted with resin cement (Rely X ARC) on composite resin abutment replicas. These crowns were then subjected to motion fatigue in water (106 cycles or till fracture with 30-300 N varying load). A stainless steel indenter was used to perform axial load between buccal and lingual cusps. Mechanical cycling was interrupted at each 125000 cycles for damage investigation in a stereomicroscope. Fractured crows were submitted to scanning electron microscopy and not-fractured crowns were included in epoxy resin, longitudinally sectioned and sequentially polished for damage analysis. Each crown received scores according to the type of failure. Statistical analysis was carried out with Kruskal-Wallis test and multiple comparisons between groups...

Estudo da anatomia do sistema de canais radiculares de incisivos laterais superiores, utilizando cortes macroscópicos e da diafanização / Lateral upper incisor radicular canal system study, using macroscopic cuts and clarifying technique

Cento e cinco incisivos laterais superiores extraídos foram utilizados na presente pesquisa, que analisou os aspectos da cavidade pulpar por meio de cortes macroscópicos e de diafanização. Verificou-se que 1,9 por cento das amostras apresentqu dois canais e 98,1 por cento, um canal radicular. A permeabilidade dentinária estava presente em 87,2 por cento das amostras, os canais secundários em 15 por cento, os canais laterais em 7,8 por cento e os deltas apicais em 2,8 por cento