Morphological analysis of glass, carbon and glass/carbon fiber posts and bonding to self or dual-cured resin luting agents

OBJECTIVE: The aim of this study was to evaluate the morphology of glass (GF), carbon (CF) and glass/carbon (G/CF) fiber posts and their bond strength to self or dual-cured resin luting agents. MATERIAL AND METHODS: Morphological analysis of each post type was conducted under scanning electron microscopy (SEM). Bond strength was evaluated by microtensile test after bisecting the posts and re-bonding the two halves with the luting agents. Data were subjected to two-way ANOVA and Tukey's test (&#945;=0.05). Failure modes were evaluated under optical microscopy and SEM. RESULTS: GF presented wider fibers and higher amount of matrix than CF, and G/CF presented carbon fibers surrounded by glass fibers, and both involved by matrix. For CF and GF, the dual-cured material presented significantly higher (p<0.05) bond strength than the self-cured agent. For the dual agent, CF presented similar bond strength to GF (p>0.05), but higher than that of G/CF (p<0.05). For the self-cured agent, no significant differences (p>0.05) were detected, irrespective of the post type. For GF and G/CF, all failures were considered mixed, while a predominance of adhesive failures was detected for CF. CONCLUSION: The bonding between fiber posts and luting agents was affected by the type of fibers and polymerization mode of the cement. When no surface treatment of the post is performed, the bonding between glass fiber post and dual-cured agent seems to be more reliable

Strengthening Of Porcelain Provided By Resin Cements And Flowable Composites

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This study evaluated the effect of mechanical properties of resin-based luting agents on the strength of resin-coated porcelain. The luting agents tested were two flowable resin composites (Filtek Z350 Flow and Tetric-N Flow), a light-cured resin cement (Variolink Veneer [VV]), and a dual-cured resin cement (Variolink II) in either light-cured (base paste) or dualcured (base + catalyst pastes [VD]) mode. Flexural strength (sigma(f)) and modulus of elasticity (E-f) of the luting agents were measured in three-point bending mode (n=5). Porcelain discs (Vita VM7) were tested either untreated (control) or acid etched, silanized, and coated with the luting agents. Biaxial flexural strength (sigma(bf)) of the porcelain discs was tested using a ball-onring setup (n=30). The sigma(bf) of the resin-coated specimens was calculated at z-axial positions for multilayer specimens in the ball-on-ring test: position z = 0 (ceramic surface at the bonded interface) and position z = -t(2) (luting agent surface above ring). The sigma(f) and E-f data were subjected to analysis of variance and the Student-Newman-Keuls test (alpha=0.05). A Weibull analysis was performed for sigma(bf) data. Weibull modulus (m) and characteristic strength (sigma(0)) were calculated. Linear regression analyses investigated the relationship between mechanical properties of the luting agents and the strengthening of porcelain. VD had higher and VV had lower mechanical strength than the other materials. At z = 0, all resin-coated groups had higher sigma(bf) than the control group. No significant differences between the luting agents were observed for sigma(bf) and sigma(0). At z = -t(2), VD had the highest sigma(bf) and sigma(0), whereas VV had the poorest results. No significant differences in m were observed across groups. A linear increase in flexural strength of the porcelain was associated with increased sigma(f) and E-f of the luting agents at position z = -t(2). In conclusion, resin coating and use of luting agents with better physical properties generally improved the mechanical performance of porcelain.41179188FAPERGS/Brazil [0902063]CNPq/Brazil [503897/2012-4]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Bonding to wet or dry deproteinized dentin: microtensile bond strength and confocal laser micromorphology analysis

Aim: To investigate the influence of deproteinization and moisture condition (wet vs. dry) on the bond strength and micromorphology of resin-dentin bonding interfaces. Methods: Dentin surfaces were etched with 37% phosphoric acid for 15 s and rinsed with water. Four groups (n = 10) were tested: WET: dentin was left visibly moist; DRY: dentin was dried with compressed air; WET-D: dentin was deproteinized for 60 s using 10% NaOCl solution and left moist; DRY-D: dentin was deproteinized and dried. Prime&amp;Bond 2.1 adhesive was applied and the teeth were restored with composite resin. Microtensile test was carried out after 24 h, and failure modes classified under magnification. Data were subjected to two-way ANOVA and Tukey’s test (P &lt; 0.05). The bonding micromorphology was analyzed by confocal laser scanning microscopy. Results: The group DRY showed significantly lower bond strength (P &lt; 0.05) than the other groups, which were similar to each other (P &gt; 0.05). Adhesive failures were predominant. Analysis of micromorphology showed formation of a collagen-resin hybrid layer only for the non-deproteinized groups. Adhesive penetration into the dentinal tubules was deeper for the DRY-D compared to the WETD group. Conclusion: The bond strength was not dependent on the moisture condition and a more homogeneous hybridization was obtained when dentin was deproteinize

Influence of post and resin cement on stress distribution of maxillary central incisors restored with direct resin composite

The current study evaluated the influence of two endodontic post systems and the elastic modulus and film thickness of resin cement on stress distribution in a maxillary central incisor (MCI) restored with direct resin composite using finite element analysis (FEA). A three-dimensional model of an MCI with a coronary fracture and supporting structures was performed. A static chewing pressure of 2.16 N/mm2 was applied to two areas on the palatal surface of the composite restoration. Zirconia ceramic (ZC) and glass fiber (GF) posts were considered. The stress distribution was analyzed in the post, dentin and cement layer when ZC and GF posts were fixed to the root canals using resin cements of different elastic moduli (7.0 and 18.6 GPa) and different layer thicknesses (70 and 200 μm). The different post materials presented a significant influence on stress distribution with lesser stress concentration when using the GF post. The higher elastic modulus cement created higher stress levels within itself. The cement thicknesses did not present significant changes.34222322

Correlation between patient complaint, temporomandibular disorder diagnosis and mandible head morphology

The aim of this study was to evaluate the correlation between patient complaints, clinical diagnosis of temporomandibular disorder (TMD) based on the diagnostic criteria for TMD, and morphology of the mandibular condyle obtained by cone-beam computed tomography (CB-CT). Data were collected from 40 patients. The anatomy of the mandibular condyle was assessed using CB-CT, the diagnosis of TMD according to diagnostic criteria for TMD, and patients' complaints was registered at the appointment. Data were explored and all statistical references were completed in bicaudal tests, with 95% confidence level (α=0.05). The Chi-squared test was used with Bonferroni correction (z-tests). Main complaints found were grouped as muscular, articular, muscular and articular, or headache and articular symptoms. Clinical diagnosis of TMD involved myalgia, local myalgia, myofascial pain, myofascial pain with reference, myofascial pain with arthralgia, arthralgia, or disc displacement with reduction. At least one joint showed condylar flattening, erosion, sclerosis, or osteophytes. No correlation was observed between main complaints, clinical diagnosis, and morphology of the mandibular condyle in all comparisons. The findings suggest that due to the absence of clinical and morphological correlation, CB-CTs should be requested only in specific cases, when doubt remain after careful TMD diagnosis, to avoid their over-indication

Endocoroa em pré-molar utilizando cerâmica reforçada por dissilicato de lítio: um relato de caso

This study reported a clinical case about restoration of an endodontically treated tooth using an endocrown in lithium disilicate-reinforced ceramic fabricated by CAD/CAM system. Case of a female patient, 48 years old who presented coronal fracture of an endodontically treated tooth. Restoration with endocrown in lithium disilicate-reinforced ceramic fabricated by CAD/CAM system was indicated. The crowns were evaluated using a California Dental Association (CDA) quality assessment system at baseline and at follow-up examination. Endocrown in lithium disilicate-reinforced ceramic fabricated by CAD/CAM system was a reliable restorative alternative for an endodontically treated premolar. The minimally invasive prepare for endocrown preserves maximum tooth structure as a gold standard for tooth restorations. In addition, such restorative alternative is advantageous in comparison to conventional full post-and-core supported crown since it presents appropriate mechanical performance and longevity as a lower cost and faster clinical procedure.Este caso clínico descreve a restauração de um dente tratado endodonticamente com uma endocoroa em cerâmica de dissilicato de lítio fabricada pelo sistema CAD/CAM. O caso é de uma paciente do sexo feminino, 48 anos, que apresentava fratura coronária de um dente tratado endodonticamente. Uma restauração com endocoroa em dissilicato de lítio fabricada pelo sistema CAD/CAM foi indicada. As coroas foram avaliadas usando um sistema de avaliação de qualidade da Associação Dental da Califórnia e exame de acompanhamento. Uma endocoroa cerâmica em dissilicato fabricada por CAD/CAM foi uma alternativa de tratamento restaurador confiável para um pré-molar tratado endodonticamente. O preparo minimamente invasivo para endocoroa que preserva o máximo de estrutura dentária é considerado padrão ouro para restaurações dentárias. Ainda, tal alternativa restauradora é mais conservadora em comparação à coroa total com retentor intrarradicular e apresenta apropriado desempenho mecânico e longevidade com um menor custo e rapidez no preparo

Different fabrication techniques of implant-supported prostheses: microhardness and fracture strength

Aim: This study evaluated the mechanical behavior of implant-supported crowns obtained by different fabrication technique after thermomechanical cycling. Methods: Thirty-two external hexagon dental implants were divided into four groups (n=10): CC – conventional casting with torch; EI – electromagnetic induction casting; PL – plasma casting; and CAD-CAM – milling through computer-aided design and computer-aided manufacturing. Vickers microhardness of the specimens were made before and after the thermomechanical cycling, and then subjected to fracture load. Fracture pattern was evaluated. Results: No significant difference was observed comparing the microhardness before and after thermomechanical cycling. CAD-CAM group presented significant lower microhardness than the other groups. No significant statistical difference was showed on fracture load between the groups. The CAD-CAM and PL presented lower number of failure by plastic deformation. Conclusion: The manufacturing techniques affected the mechanical behavior and the failure pattern of implant-supported crowns tested

Avaliação da rugosidade superficial de uma resina composta com uso de diferentes polidores

Introduction: The surface roughness is defined by the surface of a restorative material after the finishing and polishing steps, and is affected by the properties of the resinous composite as well as by the instruments used to perform the polishing. Objectives: To evaluate the surface roughness of a polished nano-hybrid composite resin with different polishing systems by atomic force microscopy (MFA) and polishing analysis by scanning electron microscopy (SEM). Materials and Methods: the factors under study are polishing systems at three levels: Enhance (Dentsply), Ultra-Gloss (American Burrs) and Dura-Gloss (American Burrs). The experimental units are composed of 30 specimens in conventional nano-hybrid composite resin, divided randomly into 3 groups (n = 10). The G1 Group received treatment with the single-stage polishing system: Dura-Gloss, Group G2, multi-step polishing system: Ultra-Gloss and Group G3 was treated with the single-stage polishing system: Enhance. The quantitative response variable is given by the surface roughness evaluated by atomic force microscopy (MFA). Results: the results showed that the systems of Dura-Gloss and Ultra-Gloss polishers presented similar surface roughness (p = 0.201) and differed statistically from the Enhance system (p = 0.023, Ultra-Gloss and p = 0.000, Dura- Gloss), which presented higher surface roughness for the nano-hybrid composite resin. Conclusion: Dura-Gloss and Ultra-Gloss polishers have a higher polishing capacity of nano-hybrid composite resin.Introdução: A rugosidade superficial é definida pela superfície de um material restaurador após as etapas de acabamento e polimento, e é afetada pelas propriedades do compósito resinoso, bem como pelos instrumentos utilizados para a realização do polimento. Objetivos: Avaliar a rugosidade superficial de uma resina composta nano-híbrida polida com diferentes sistemas de polimento por Microscopia de Força Atômica (MFA) e análise dos polidores por Microscopia Eletrônica de Varredura (MEV). Materiais e métodos: Os fatores em estudo são os sistemas de polimento em três níveis: Enhance (Dentsply), Ultra-Gloss (American Burrs) e Dura-Gloss (American Burrs). As unidades experimentais são formadas por 30 corpos de prova em resina composta convencional nano-híbrida, divididos aleatoriamente em 3 grupos (n=10). O Grupo G1 recebeu tratamento com o sistema de polimento de uma única etapa: Dura-Gloss; o Grupo G2, sistema de polimento de múltiplas etapas: Ultra-Gloss; e o Grupo G3 recebeu o tratamento com o sistema de polimento de uma única etapa: Enhance. A variável de resposta quantitativa se dá pela rugosidade superficial avaliada pela Microscopia de Força Atômica (MFA). Resultados: Os resultados obtidos demonstram que os sistemas de polidores Dura-Gloss e Ultra-Gloss apresentaram rugosidade superficial similar entre si (p=0,201) e diferiram estatisticamente do sistema Enhance (p=0,023, Ultra-Gloss e p=0,000, Dura-Gloss), o qual apresentou maior rugosidade superficial para a resina composta nano-híbrida. Conclusão: Os polidores Dura-Gloss e Ultra-Gloss tem maior capacidade de polimento da resina composta nano-hibrida

Shear bond strength test using different loading conditions – a finite element analysis

Aim: This study evaluated the stress distribution at the bond interface during shear bond strength testing for three loading conditions. Methods: A three-dimensional model was created of a specimen for evaluation by the shear bond strength test, using three cylindrical volumes representing the dentin, adhesive system and composite resin. A linear analysis was performed to calculate the stress distribution at the dentin-adhesive interface. Three models simulating different loading conditions were prepared: chisel, orthodontic-looped wire and stainless steel tape. Results: Chisel presented severe stress concentrations near the loading site (-10681 to 637 MPa). Wire presented stress concentrations along the radial loading axis (-382 to 216 MPa). Tape presented more uniform stress distribution (-83 to 21 MPa). Conclusions: The loading with stainless steel tape allowed more uniform stress distribution at the bond interface, and was a more reliable way to evaluate the bond with regard to the aim of the shear bond strength test