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AIM: To compare the effects of Cervical Access Cavity (CervAC) and Traditional Access Cavity (TradAC) on root canal preparation, root canal filling, and fracture resistance in mandibular incisors. METHODOLOGY: Twenty recently extracted and intact mandibular incisors were initially scanned using a micro-CT device. The specimens were anatomically matched to create two groups (n = 10). A wedge-shaped non-carious cervical lesion (NCCL) was created on the buccal aspect of all teeth using a double-faced segmented diamond disc. In group 1, a TradAC was prepared, whilst in group 2, access was created through the simulated NCCL using a round diamond bur 1012. After root canal preparation with Rotate instruments sizes 15/0.04, 20/0.04, and 25/0.04, the teeth were scanned again and evaluated for root canal volume and surface area, static voxels, volume of removed dental tissue, and dentine thickness. After that, the root canals were filled using the single-cone technique, teeth were restored with composite resin, and subsequently rescanned to calculate the volume of filling materials and voids. Then, the restored teeth were subjected to fracture resistance tests using a universal testing machine. Statistical comparisons between groups were performed with the Mann-Whitney test or the Student's t-test, with a statistical significance level of 5%. RESULTS: Statistical comparisons indicated no significant differences between groups in terms of root canal volume, surface area, static voxels, removed root dentine, root canal filling volume, percentage of voids, or fracture resistance load (p > .05). Conversely, teeth prepared with TradAC showed a significantly higher percentage of dental tissue removed from the crown (p = .001) and a greater volume of filling material remnants in the pulp chamber (p < .001) compared to the CervAC group. A significantly lower percentage reduction in dentine thickness was observed only on the mesial aspect of root at Level 1 in TradAC group (p = .008). CONCLUSIONS: CervAC can be considered a viable alternative approach in the presence of NCCL in mandibular incisors.

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La preparación de la cavidad de acceso es el primer paso y un requisito esencial, para la instrumentación y obturación de los conductos radiculares durante el tratamiento endodóntico. El objetivo del presente estudio fue comparar la resistencia a la fractura in vitro de premolares con cavidad de acceso tradicional (CAT), cavidad de acceso conservador (CAC) y cavidad de acceso ultraconservador (CAU). Esta fue una investigación transversal, prospectiva y experimental pura. Se realizó con 40 segundos premolares superiores, divididos en 4 grupos. Todas las muestras fueron desinfectadas y almacenadas en recipientes con suero fisiológico al 0,9 %. Al primer grupo se designó como el control, al segundo grupo CAT, al tercer grupo CAC y al cuarto grupo CAU. Se realizaron todos los accesos endodónticos con una pieza de mano de alta velocidad con refrigeración respetando el protocolo de cada uno de los diseños, posterior a ello se realizó el tratamiento endodóntico y restauración de los especímenes. Una vez preparadas todas las muestras, estas fueron sometidas a una prueba de fatiga en una máquina de ensayo universal y los resultados se registraron en Newtons. La prueba estadística usada fue ANOVA con un nivel de significancia de 5 %. Las CAT obtuvieron el menor valor de resistencia a la fractura en comparación con el grupo control. Sin embargo, no se observaron diferencias estadísticamente significativas entre los grupos CAT, CAC Y CAU. Entre los grupos CAC y CAU, no se encontraron diferencias estadísticamente significativas en comparación con el grupo control.

The preparation of the access cavity is the first step and an essential requirement for the instrumentation and obturation of the root canals during endodontic treatment. The objective of the present study was to compare the in vitro fracture resistance of premolars with traditional access cavity (CAT), conservative access cavity (CAC) and ultraconservative access cavity (CAU). This was a cross-sectional, prospective and pure experimental research. It was carried out with 40 upper second premolars, divided into 4 groups. All samples were disinfected and stored in containers with 0.9 % physiological saline. The first group was designated as the control, the second group CAT, the third group CAC and the fourth group CAU. All endodontic accesses were carried out with a high-speed handpiece with refrigeration, respecting the protocol of each of the designs, after which the endodontic treatment and restoration of the specimens was carried out. Once all the samples were prepared, they were subjected to a fatigue test in a universal testing machine and the results were recorded in Newtons. The statistical test used was ANOVA with a significance level of 5 %. The CAT obtained the lowest fracture resistance value, presenting statistically significant differences with the control group. However, no statistically significant differences were observed between the CAT, CAC, and CAU groups. Furthermore, between the CAC and CAU groups, no statistically significant differences were found compared to the control group.

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This study assessed the mechanical properties of the Only One File Blue and the Reciproc Blue instruments. A total of 80 new 25 mm reciprocating NiTi instruments (25/.08v) were evaluated for their mechanical performance (n = 40 per group). Cyclic fatigue resistance, torsional fatigue, flexural resistance and buckling resistance tests were conducted. Statistical analysis was employed with a significance level set at 5%. The results indicated no statistically significant differences in resistance to cyclic fatigue neither in the fragment length between the instruments (p > 0.05). However, the Reciproc Blue instrument exhibited greater torque to fracture and a larger rotation angle than the Only One File Blue instrument (p < 0.05). The Only One File Blue instrument demonstrated higher flexibility but lower resistance to buckling compared to the Reciproc Blue instrument (p < 0.05). In conclusion, the tested instruments exhibit differences in mechanical properties, with the Reciproc Blue instrument generally presenting greater advantages than the Only One File Blue.

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OBJECTIVES: This study aimed to assess the influence of translucent monolithic versus bilayered crowns and whether the use of a CoCr base abutments affects the fatigue and fracture resistance of screwed implant-supported single crowns with external connections under mechanical cycling. MATERIALS AND METHODS: Fifty specimens were divided into groups: (1) metal-ceramic (MC) crown, (2) veneered zirconia crown (Zr), (3) veneered zirconia crown with a CoCr base abutment (ZrB), (4) monolithic translucent zirconia crown (MZr), and (5) monolithic translucent zirconia crown with a CoCr base abutment (MZrB). Specimens underwent mechanical cycling (5 × 106 cycles; 150 N) evaluating fatigue resistance (number of failures) and those that failed were subsequently subjected to fractographic analyses (stereomicroscope and scanning electron microscope) to evaluate failure location and area, and maximum fracture load was also measured. RESULTS: The failure-related survival rate (100%) and maximum fracture resistance of the MZrB were significantly higher than those of MC and Zr (50%; p < 0.05). There were no significant differences in the failure rate and fracture resistance when a CoCr base abutment was used or not in the translucent monolithic Zr groups (p > 0.05;MZrB vs. MZr). Failure location, with MC crowns' fractures, noted at the screw area (p = 0.043), while all-ceramic crowns were mostly in the cuspid and to failure area, the Zr group had the largest mean (15.55 ± 9.17 mm2) among the groups, significant difference only when compared with MC (1.62 ± 0.81 mm2) (p = 0.025). CONCLUSIONS: Translucent monolithic zirconia crowns exhibited significantly higher fatigue and fracture resistance compared with conventional MC and bilayered crowns. CLINICAL SIGNIFICANCE: The appropriate choice of material and manufacturing technique is crucial for predicting the higher clinical performance of single crowns. Enhanced mechanical resistance in terms of fatigue and fracture resistance can be achieved by replacing MC and bilayered restorations with computer-aided design and computer-aided manufacturing monolithic zirconia.

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During the preparation of fixed prosthesis (including individual bridges and crowns) it is important to select the materials that have the best features and properties to predict a successful clinical treatment. The objective of this study was to determine if the chemical and structural characteristics could cause to increase the fracture resistance, we used four bis-acryl resins Luxatemp, Protemp, Structur and Telio. Three-points bending by Flexural test were performed in ten bars and they were carried out to compare with Anova test. In addition, the bis-acryl resins were analyzed by scanning electron microscopy, to analyze microstructure and morphology and the molecular structure were performed by Infrared Spectroscopy through Attenuated Total Reflectance. A higher flexural strength was found in Luxatemp and Structur with, no significant differences between this study groups. Regarding Protemp and Telio, these study groups showed a lower flexural strength when were compared with Luxatemp and Structur. These results corroborate SEM and ATR analysis because Luxatemp sample showed a regular size particle on the surface and chemically presents a long cross-linkage polymer chain. The presence of CO3, SiO2 and N-H groups as a fillers particle interacting with OH groups cause a higher flexural strength compared with another groups.

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BACKGROUND: The literature is scanty regarding the effect of radiation therapy (RT) on the mechanical properties of immature permanent teeth. AIM: To evaluate the effect of RT on the fracture resistance of simulated immature teeth submitted to different types of root reinforcement. DESIGN: Sixty-four human teeth simulating the Cvek stage 3 of root development were distributed into eight groups (n = 8), according to exposure or not to RT (70 Gy) and the root reinforcement method: Group NR (control)-no reinforcement/no RT; Group NR + RT (control)-no reinforcement/RT; Group PO-tricalcium silicate-based cement (TS) apical plug/canal obturation/no RT; Group PO + RT-TS apical plug/canal obturation/RT; Group TS-canal filling with TS/no RT; Group TS + RT-canal filling with TS/RT; Group FP-TS apical plug/fibreglass post/no RT; and Group FP + RT-TS apical plug/fibreglass post/RT. Fracture resistance was determined using a universal testing machine (0.5 mm/min). RESULTS: In the intergroup comparison, nonirradiated teeth had higher fracture resistance (p < .05). Groups FP and FP + RT had higher fracture resistance (p < .001). CONCLUSION: Radiotherapy affected the fracture resistance of simulated immature teeth. Reinforcement with fibreglass posts increased the fracture resistance, regardless of the radiation.

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This research article explores the effect of grain boundary (GB) misorientation on the mechanical behavior of aluminum (Al) bicrystals by means of molecular dynamics (MD) simulations. The effect of GB misorientation on the mechanical properties, fracture resistance, and crack propagation are evaluated under monotonic and cyclic load conditions. The J-integral and the crack tip opening displacement (CTOD) are assessed to establish the effect of the GB misorientation angle on the fracture resistance. The simulations reveal that the misorientation angle plays a significant role in the mechanical response of Al bicrystals. The results also evidence a gradual change in the mechanical behavior from brittle to ductile as the misorientation angle is increased.

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The development of digital technologies has allowed for the fabrication of new materials; however, it makes it difficult to choose the best methods to obtain occlusal splints with optimal properties, so it is essential to evaluate the effectiveness of these materials. The aim of the study is to compare the fracture resistance of occlusal splints made of different materials after thermo-mechanical aging. METHODS: A total of 32 samples were made from 4 materials (two 3D printed polymeric materials, a PMMA disc for CAD/CAM, and a conventional heat-cured acrylic resin); subsequently, the fracture test was performed using the load compression mode applied occlusally on the splint surface. STATISTICAL ANALYSIS: Four statistical tests were used (Shapiro-Wilk, Levene's test, ANOVA, and Tukey's HSD test). RESULTS: The following study showed that there are differences in fracture strength among the four materials investigated, where the highest strength was observed in the milled splint, with a mean of 3051.2 N (newton) compared to the strength of the flexible splint with 1943.4 N, the printed splint with 1489.9 N, and the conventional acrylic splint with 1303.9 N. CONCLUSIONS: The milled splints were the most resistant to fracture. Of the printed splints, the splint made with flexural rigid resin withstood the applied forces in acceptable ranges, so its clinical indication may be viable. Although the results of this research indicated differences in the mechanical properties between the CAD/CAM and conventional fabrication methods, the selection may also be influenced by processing time and cost, since with a CAD/CAM system there is a significant reduction in the production time of the splint material.

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The aim of this study was to evaluate and compare the fracture resistance of a single-unit fixed prosthesis, using a CAD/CAM PMMA material and two printed materials (3DPPa and 3DPPb). A typodont with a specific preparation for a full crown was used; a digital impression was made with a state-of-the-art scanner (PrimeScanTM, Dentsply-SironaTM, New York, NY, USA), and a full coverage restoration was designed using a biogeneric design proposal by means of specific software (InLAB 22.1, Dentsply-Sirona, NY, USA). Sixty crowns were prepared, divided into three groups according to the material: 3DPPa (n = 20), 3DPPb (n = 20), both 3D-printed from the .STL file with a resolution of 50 µm, and PMMA (n = 20) milled-derived, which were subjected to a thermocycling process. A universal testing machine (Universal/Tensile Testing Machine, Autograph AGS-X Series) with integrated software (TRAPEZIUM LITE X) equipped with a 20 kN load cell was used to determine the fracture resistance. Significant differences were found by Kruskal-Wallis test and multiple comparisons (p < 0.05) in fracture resistance between materials. The fracture resistance for the PMMA material was higher, and the standard deviation was lower (x = 1427.9; sd = 36.9 N) compared to the 3DPPa (x = 1231; sd = 380.1 N) and 3DPPb (x = 1029.9; sd = 166.46 N) prints. The restorations from the milled-derived group showed higher average fracture resistance than the provisional restorations obtained from the printed groups. However, the results demonstrated that all three materials analyzed in single-unit restorations are capable of withstanding the average masticatory forces.

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Abstract This study aimed to evaluate the effect of antioxidant solutions on fracture strength and bonding performance in non-vital and bleached (38% hydrogen peroxide) teeth. One hundred and eighty dentin specimens were obtained, 60 for each test: fracture strength, hybrid layer thickness, and bond strength. The groups (n=10) were randomly composed according to post-bleaching protocol: REST - restoration, without bleaching; BL - bleaching + restoration; SA - bleaching, 10% sodium ascorbate solution, and restoration; AT - bleaching, 10% α-tocopherol solution, and restoration; CRAN - bleaching, 5% cranberry solution, and restoration; CAP - bleaching, 0.0025% capsaicin solution, and restoration. Data were analyzed with ANOVA, Kruskal-Wallis, Dunn, and Qui-Square tests (α=0.05). The highest fracture strength values were observed in REST (1508.96 ±148.15 N), without significant difference for the bleached groups (p>0.05), regardless of the antioxidant use. The hybrid layer thickness in the group that was not subjected to bleaching (REST) was significantly higher than in any other group. The bond strength in the bleached and antioxidants-treated groups (SA, AT, CRAN, CAP) has no differences with the bleached group without antioxidants (BL). Adhesive failures were predominant in the groups that did not receive the antioxidant application. In conclusion, the evaluated antioxidants did not show an effect on the fracture strength, hybrid layer thickness, or bond strength of dentin bleached after endodontic treatment. The application of 10% sodium ascorbate, 10% alpha-tocopherol, 5% cranberry, or 0.0025% capsaicin solutions is not an effective step and should not be considered for the restorative protocols after non-vital bleaching.

Resumo Este estudo teve como objetivo avaliar o efeito de soluções antioxidantes na resistência à fratura e resistência de união em dentes tratados endodonticamente e clareados (38% de peróxido de hidrogênio). Cento e oitenta espécimes de dentina foram obtidos, 60 para cada teste: resistência à fratura, espessura da camada híbrida e resistência de união. Os grupos (n=10) foram compostos aleatoriamente de acordo com o protocolo pós-clareamento: REST - restauração, sem clareamento; BL - clareamento + restauração; SA - clareamento, solução de ascorbato de sódio a 10% e restauração; AT - clareamento, solução de α-tocoferol a 10% e restauração; CRAN - clareamento, solução de cranberry a 5% e restauração; CAP - clareamento, solução de capsaicina 0,0025% e restauração. Os dados foram analisados ​​com os testes ANOVA, Kruskal-Wallis, Dunn e Qui-Quadrado (α=0,05). Os maiores valores de resistência à fratura foram observados em REST (1508,96 ±148,15 N), sem diferença significativa para os grupos clareados (p>0,05), independente do uso de antioxidantes. A espessura da camada híbrida no grupo que não foi submetido ao clareamento (REST) foi significativamente maior do que em qualquer outro grupo. A resistência de união nos grupos clareado e tratado com antioxidantes (SA, AT, CRAN, CAP) não apresentou diferenças com o grupo branqueado sem antioxidantes (BL). As falhas adesivas foram predominantes nos grupos que não receberam a aplicação do antioxidante. Em conclusão, os antioxidantes avaliados não mostraram efeito sobre a resistência à fratura, espessura da camada híbrida ou resistência de união à dentina clareada após tratamento endodôntico. A aplicação de soluções de ascorbato de sódio 10%, alfa-tocoferol 10%, cranberry 5% ou capsaicina 0,0025% não é uma etapa eficaz e não deve ser considerada para os protocolos restauradores após clareamento não vital.

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OBJECTIVE: This study is to evaluate fracture resistance, failure mode, and gap formation at the restorative interface of unrestored or restored non-carious cervical lesions (NCCLs) submitted to a short-term erosive environment. MATERIALS AND METHODS: Artificial NCCLs were produced in vitro in bovine incisors, and were randomly divided into four restorative resins groups (n = 22): nanohybrid-NR; bulk-fill-BR; flow with a nanohybrid layer-FNR; bulk-fill with a nanohybrid layer-BNR; and a group unrestored-UR (n = 16). Half of the specimens were submitted to an erosive challenge (per 5 min, 3 × a day for 7 days, before and after restoration), and the other half, was immersed in artificial saliva. After, all teeth undergone thermal (5 ºC, 37 ºC, and 55 ºC, 3600 cycles) and mechanical (50 N, 2 Hz, 300,000 cycles) aging. Eighty teeth were subjected to compressive loading, and resistance and failures were analyzed, while 24 teeth were evaluated for gaps by microcomputed tomography. Statistical tests were performed (p < 0.05). RESULTS: The restorative approaches affected fracture resistance (η2p = 0.14, p = 0.023), and gap formation (η2 = 0.18, p = 0.012) and so did the immersion medium (fracture η2p = 0.09, p = 0.008; gap η2 = 0.09, p = 0.017). BNR showed the highest resistance, while UR the lowest. FNR showed the highest gaps in both immersion media. Neither the resin groups nor the immersion media were associated with failure mode. CONCLUSIONS: The erosive immersion medium based in acid beverages has been shown to affect NCCLs with or without restoration, but when Bulk-Fill resin is covered by nanohybrid resin, the performance is good. CLINICAL RELEVANCE: Erosion negatively affects restorations, but unrestored NCCL shows worse biomechanical performance in stress-bearing situations.

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The aim of this in vitro study was to evaluate the biomechanical and chemical behavior of various bioactive materials in class II MOD restorations. Forty- eight standardized class II MOD cavities were prepared in sound extracted human molar teeth. The specimens were divided into four groups according to the restorative material: Group 1 (Filtek™ Z350 XT), Group 2 (Biodentine™ as a liner, and then restored with Filtek™ Z350 XT), Group 3 (Cention N™), and Group 4 (Activa™ Bioactive-Restorative). The samples were tested for fracture resistance by subjecting them to a compressive load in a Universal testing Machine. The failure modes of each specimen were evaluated. The alkalinizing potential and calcium ion release of the materials were measured. SEM-EDAX analyses were also performed for all materials. Data were analyzed using ANOVA and post hoc Tukey test (p<0.05). Group 1 showed the higher fracture resistance (p<0.05). Group 3 had greater fracture resistance values but no statistical difference from Group 4. Biodentine™ showed greater biomineralization potential. Class II MOD restorations of Group 1 displayed the higher fracture resistance; however, it was highly associated with catastrophic failure. Conversely, Biodentine™ presented a more significant bioactivity potential, and its use, as in Group 2, promoted the most favorable failure mode.

El objetivo de este estudio, in vitro, fue evaluar el desempeño biomecánico y químico de varios materiales bioactivos en restauraciones clase II MOD. Se prepararon cuarenta y ocho cavidades clase II MOD estandarizadas en dientes molares humanos extraídos. Las muestras se dividieron en cuatro grupos según el material de restauración: Grupo 1 (Filtek™ Z350 XT), Grupo 2 (Biodentine™ como base y luego restaurado con Filtek™ Z350 XT), Grupo 3 (Cention N™) y Grupo 4 (Activa™ Bioactivo-Reparador). La prueba de resistencia a la fractura fue realizada en una máquina de ensayo universal Instron. Se evaluaron los modos de falla de cada espécimen. Se midió el pH y la liberación de iones de calcio de los materiales. Se realizaron análisis SEM-EDAX. Los datos se analizaron mediante ANOVA y la prueba post hoc de Tukey (p<0,05). El grupo 1 mostró la mayor resistencia a la fractura (p<0,05). El Grupo 3 tuvo mayores valores de resistencia a la fractura que el Grupo 4, pero sin diferencia estadística. Biodentine™ mostró un mayor potencial de biomineralización. Las restauraciones Clase II MOD del Grupo 1 mostraron la mayor resistencia a la fractura; sin embargo, estuvo altamente asociado con fallas irreparables. Por el contrario, Biodentine™ presentó un potencial de bioactividad más significativo y su uso, como en el Grupo 2, promovió el modo de falla más favorable.

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Polymer nanoclay composites have received significant attention due to their substantially enhanced mechanical, thermal and barrier properties. However, the effect of these nanoclays on the dynamic fracture resistance of a polymer matrix during fast fracture events has not been documented. In this study, the effect of nanoclay addition on the rapid crack propagation (RCP) resistance of high-density polyethylene (HDPE) was investigated through the high-speed double torsion test. Results showed that the addition of 1, 3, and 5% of nanoclays improved the dynamic fracture resistance under the plane strain conditions (Gd1) of HDPE up to 65%. An increase in the storage and loss modulus, and a decrease in crystallinity and melt flow index with nanoclay content was also found. Although the presence of agglomerates can hinder the enhancement of Gd1 as it promotes agglomerate fracture and debonding, the increase in energy consumption through fibrillation and crazing promoted by the nanoclay prevails, suggesting that the nanoclay's toughening effect that has been extensively reported under quasi-static and impact tests, is also present under RCP conditions, and that the HDPE nanocomposites could be used in applications in which RCP must be prevented.

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Recent formulations of resin-based composites have incorporated different combinations of materials. However, the mechanical and bonding behavior of these materials with intraradicular posts are unclear. This study aimed to evaluate the effect of light-cure and dual-cure resin composite posts on the fracture resistance of endodontically-treated teeth. Materials and Methods: Ninety extracted human upper canines were selected and randomly divided into nine groups (n=10): (G1) endodontically treated teeth without endodontic posts; (G2) glass-fiber post cemented with glass-ionomer cement; (G3) endodontic post by dual-cure composite resin (Rebilda DC); (G4) endodontic post by dual-cure composite resin (Cosmecore); (G5) endodontic post by dual-cure composite resin (Bis-Core); (G6) endodontic post by light-cure composite resin; (G7) glass-fiber post customized with flowable composite resin; (G8) glass-fiber post cemented with light-cure composite resin; (G9) glass-fiber post cemented with self-adhesive resin cement. After the post insertion, all specimens were subjected to mechanical (250,000 cycles) and thermocycling (6000 cycles, 5 °C/55 °C) and immediate loading at 45 degrees in a universal testing machine until fracture. The data were analyzed by one-way ANOVA and multiple comparisons using the Fisher LSD Method (p < 0 05). Results: The mean failure loads (±SD) for the groups ranged from 100.7 ± 22.6 N to 221.9 ± 48.9 N. The G1 group (without endodontic posts) had a higher fracture strength than all experimental groups (p < 0.001). Conclusions: Within the limitations, the light- and dual-cure post technique did not present lower fracture resistance values as compared to the conventional glass-fiber post.

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O objetivo deste trabalho foi avaliar, ex vivo, pelo teste de compressão e ciclagem, a resistência a fratura de dentes que tiveram suas raízes fragilizadas em laboratório que receberam reforço intrarradicular com um modelo de pino de fibra de vidro Splendor-SAP em comparação ao pino de fibra de vidro Exacto. Além disso, foi realizada análise por elementos finitos para identificar os pontos de maior estresse estrutural. Foram utilizadas 60 raízes de dentes bovinos, os espécimes foram seccionados e padronizados com 16 mm de comprimento. Os canais foram instrumentados em toda a sua extensão utilizando limas endodônticas manuais. As amostras foram aleatoriamente distribuídas em seis grupos acordo com a espessura do remanescente radicular medidos a partir do terço cervical (2 mm e 3 mm) e o reforço radicular a ser utilizado (n=10): G1 - Controle 1, com remanescente radicular de 2 mm e sem reforço intrarradicular; G2 - Controle 2, com remanescente radicular de 3 mm e sem reforço intrarradicular; G3 - Com remanescente de 2 mm e reforço intrarradicular utilizando pino Exacto; G4 - Com remanescente radicular de 3 mm e reforço intrarradicular utilizando Exacto; G5 - Com remanescente radicular de 2 mm e reforço intrarradicular utilizando Splendor-SAP; G6 - Com remanescente radicular de 3 mm e reforço intrarradicular utilizando Splendor-SAP. Para a fragilização simulada, o desgaste radicular foi de 12 mm no interior do canal. Em seguida, os canais foram obturados e o material obturador removido dos terços cervical e médio, restando apenas 4 mm de material no terço apical. A cimentação dos pinos foi realizada seguindo o protocolo do fabricante. O teste de fadiga foi realizado por ciclagem mecânica dos espécimes para o envelhecimento das mesmas (1200000 ciclos; 3.8 Hz; carga = 88 N). Foi realizado o teste de compressão pela máquina de Ensaios Universais, com célula de carga de 100 Kg à velocidade de 1 mm/min com incidência a 45°. Os valores médios de resistência à fratura encontrados para os grupos, em ordem crescente, foram: G1 - 9,045 kgf, G2 - 9,753 kgf, G3 - 68,411 kgf, G4 - 80,167 kgf, G5 - 70,551 e G6 - 80,027. Os espécimes foram analisados em estereomicroscópio para classificação do modo de falha. Os resultados obtidos foram submetidos à análise estatística (ANOVA e Tukey) que demonstrou diferença estatisticamente significativa (p<0,05) (AU)

The objective of this work was to evaluate, ex vivo, by compression and cycling test, the resistance to fracture of teeth that had their roots weakened in the laboratory and that received intraradicular reinforcement with a Splendor-SAP fiberglass post model in comparison to the Exact fiberglass pin. In addition, finite element analysis was performed to identify the points of greatest structural stress. Sixty roots of bovine teeth were used, the specimens were sectioned and standardized with 16mm in length. The canals were instrumented along their entire length using manual endodontic files. The samples were randomly distributed into six groups according to the thickness of the root remnant (2 mm and 3 mm) and the root reinforcement to be used (n=10): G1 - Control 1, with a 2 mm root remnant and without intraradicular reinforcement ; G2 - Control 2, with root remnant of 3 mm and without intraradicular reinforcement; G3 - With a 2 mm remnant and intraradicular reinforcement using an Exacto post; G4 - With root remnant of 3 mm and intraradicular reinforcement using Exacto; G5 - With root remnant of 2 mm and intraradicular reinforcement using Splendor-SAP; G6 - With root remnant of 3 mm and intraradicular reinforcement using Splendor-SAP. For simulated embrittlement, root wear was 12 mm inside the canal. Then, the specimens were obturated and had the obturator material removed from the cervical and middle thirds, leaving only 4 mm of material in the apical third. The cementation of the posts was performed following the manufacturer's protocol. The fatigue test was carried out by mechanical cycling of the specimens for their aging (1200000 cycles; 3.8 Hz; load = 88 N). The compression test was carried out using the Universal Testing machine, with a load of 100 kg at a speed of 1 mm/min with an incidence of 45°. The average fracture resistance values found for the groups, in ascending order, were: G1 - 9,045 kgf, G2 - 9,753 kgf, G3 - 68,411 kgf, G4 - 80,167 kgf, G5 - 70,551 e G6 - 80,027. The specimens were analyzed under a stereomicroscope to classify the failure mode. The results obtained were submitted to statistical analysis (ANOVA and Tukey) which showed a statistically significant difference (p <0.05). (AU)

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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.

RESUMO

O aprimoramento da tecnologia CAD/CAM permitiu a confecção de placas estabilizadoras digitais, no entanto, há lacunas acerca do comportamento desses dispositivos frente a variáveis mecânicas e biológicas ainda desconhecidas. Dessa forma, o objetivo desse trabalho foi verificar se as resinas utilizadas na tecnologia digital das placas fresadas e impressas são capazes de influenciar na resistência à fratura e na adesão de micro-organismos em detrimento das resinas empregadas na confecção das placas termopolimerizáveis convencionais e se as propriedades testadas se relacionam com a variação da espessura desses dispositivos. Para tanto, foi realizado um estudo in vitro que contou com as fases mecânica e microbiológica, sendo cada uma composta pelos grupos Convencional (GC) (n=30), Fresado (GF) (n=30) e Impresso (GI) (n=30), de acordo com o método de confecção, possuindo cada um três subgrupos (n=10) que variaram a espessura dos espécimes de 1 a 3 mm. Na fase mecânica, as amostras, com formato de barras de 65 mm, foram testadas quanto à resistência à fratura na máquina de ensaios universal, com célula de carga de 500 kgf e velocidade de 1 mm/min; na microbiológica, a forma foi de discos com 15 mm de diâmetro, submetidos à adesão de micro-organismos à superfície com a exposição a Streptococcus mutans e mantidos por 24h a 35 °C em estufa para sucessiva contagem de UFC, com controle positivo. Os testes foram feitos em triplicata e os dados foram armazenados no SPSS 22.0 e a análise estatística contou com a ANOVA e o pósteste de Tukey. Nos resultados da fase mecânica, o ANOVA identificou diferenças estatisticamente significativas entre os grupos (p≤0,005), mostrando que GC e GF apresentaram melhores resultados. O pós-teste de Tukey considerou diferença estatisticamente significativa entre GF e GI (p=0,031), elencando GF como superior. Para a fase microbiológica, não foram verificadas diferenças estatísticas entre os grupos (p>0,005) em nenhuma das análises. Observou-se que para a resistência a fraturas, as resinas do modo fresado descreveram resultados superiores e/ou próximos aos da técnica convencional; e que as resinas da técnica digital e convencional, quanto à adesão superficial de micro-organismos, não diferiram entre si (AU).

CAD/CAM technology allowed the stabilizing splints manufacture, however there are gaps about these devices' behavior in face of mechanical and biological variables that are still unknown. Thus, the objective of this project was to verify if the resins used in digital technology of milled and printed stabilizer splints can influence fracture resistance and microorganism adhesion, in detriment of the resin applied in manufacture of conventional thermopolymerizable splints and if the tested properties are related to thickness variation of these devices. The method included mechanical and microbiological steps, each one composed by Conventional (CG) (n=30), Milled (MG) (n=30) and Printed (PG) (n=30) groups, according to the method of preparation, each one having three subgroups (n=10) that varied the specimen thickness from 1 to 3 mm. In the mechanical step, the samples, in the form of 65 mm bars, were tested for fracture resistance in a universal testing machine, with load cell of 500 kgf and speed of 1 mm/min; in the microbiological step, the shape was in form of 15 mm diameter discs, subjected to microorganism adhesion to the surface with exposure to Streptococcus mutans and kept for 24 hours at 35 °C in oven for successive CFU counting, with positive control. The tests were performed in triplicate and data were stored in SPSS 22.0 and statistical analysis used ANOVA and Tukey's post hoc. In the results of mechanical step ANOVA had identified statistically significant differences between the groups (p≤0,005), showing CG and MG had presented better results. Tukey´s post hoc had considered statistically significant difference between MG and PG (p=0,031), listing MG as superior. For the microbiological step, they did not show statistical differences between the groups (p>0.005) in any analysis. It was observed milled resins described superior results and/or close to the conventional technique one, for fracture resistance; and resins of digital and conventional technique, regarding the microorganism adhesion to the surface, did not differ from each other (AU).

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RESUMO

OBJECTIVES: The aim of this study was to compare the effect of three different access cavities on the tissue removal, deflection, fracture resistance, and stress distribution of extracted maxillary central incisors. MATERIALS AND METHODS: Forty human maxillary central incisors were randomly assigned in four experimental group (n = 10) including conservative access cavity "CAC," traditional access cavity "TAC," invasive access cavity "IAC," and without access cavity (control group). Cone-beam computed tomography "CBCT" scans were used to evaluate the tissue removal during the different access cavities. All specimens were restored with composite resin (Admira Fusion, Voco, Cuxhaven, Germany) and embedded in acrylic resin blocks after simulating the periodontal ligament using red wax, then the specimens were submitted to the deflection test applying a load of 250 N and to the load-to-fracture test after artificial aging in a mechanical cycling machine (150 N, 5 × 106 cycles, 10 Hz). Lastly, stress distribution was assessed by three-dimensional finite element analysis (3D-FEA), simulating the specimens restoration by two types of composite resins of low and high elastic modulus (8 and 18 GPa respectively) after the access cavities. The data were submitted to Shapiro-Wilk and KS normality tests. Then, they were analyzed by one-way ANOVA and Tukey tests with a significance level (α ≤ 0.05). RESULTS: CBCT scans showed a significant difference of worn tissues in CAC and TAC when compared to the IAC (P < 0.0001). In deflection test, CAC showed lower deformation values than the TAC and IAC. Load-to-fracture test presented no significant difference among the three experimental groups (P = 0.6901). 3D-FEA showed that the more conservative the access cavity, the higher the stress magnitude. CONCLUSIONS: CAC promote less worn tissue; however, this does not improve the stress distribution or fracture resistance of endodontically treated maxillary incisors. CLINICAL RELEVANCE: Clinicians should reconsider the pros and cons of the conservative access cavity.

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This systematic review aimed to assess if the use of fiber posts reinforces weakened immature teeth. A systematic review was conducted of laboratory studies that evaluated the fracture resistance of simulated immature teeth restored with fiber posts compared to teeth restored exclusively with resin. An electronic search was performed using the following databases: PubMed/MEDLINE, Web of Science, Scopus and LILACS, BBO, and grey literature. Two independent researchers screened the titles and abstracts of the retrieved studies for relevance to the research question. Subsequently, the full texts of potentially relevant studies were screened based on the exclusion criteria. Ten out of 1792 unique records were included in this systematic review. Risk of bias was assessed using an adapted tool based on the Cochrane risk of bias tool. The laboratory studies included in this systematic review were performed on both human and bovine teeth. Eight studies concluded that fiber posts reinforce the structure of weakened roots, and two studies reported that fiber posts did not strengthen the radicular structure compared to teeth exclusively restored with resin composite. The highly heterogeneous data made it challenging to synthesize the results into a summary estimate, and thus no meta-analysis was undertaken. A summary effect could not be estimated without a meta-analysis. Although the laboratory literature suggests that fiber posts reinforce the structure of immature teeth, the results should be interpreted with caution, as most of the studies had an unclear or high risk of bias.

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O objetivo deste relato de caso foi descrever em detalhes a técnica de transfixação de pino de fibra de vidro no sentido horizontal e restauração de resina composta em um dente molar tratado endodonticamete. Paciente, sexo feminino, 51 anos de idade, buscou o Centro Universitário da Serra Gaúcha (FSG ­ Caxias do Sul ­ Rio Grande do Sul) com a necessidade de realizar tratamento endodôntico do elemento molar número 26. Após a avaliação inicial, foi realizada a endodontia. O elemento havia pouca sustentação das paredes vestibular e palatina, então foi proposto a colocação de pino intrarradicular seguido de coroa, entretanto, por questões financeiras a paciente não aceitou. Logo, foi proposto a técnica de transfixação horizontal de pino de fibra de vidro associado a uma restauração de resina composta de forma direta. O procedimento foi realizado em sessão única e foi utilizado um pino de fibra de vidro número 1 disposto transversalmente entre as paredes mesiopalatina e distovestibular. A restauração foi realizada com resina composta Filtek Z350, devolvendo estética e função ao elemento dentário. Pode-se concluir que a técnica de transfixação horizontal de pino de fibra de vidro associado à resina composta é uma alternativa restauradora que possibilita maior resistência aos dentes tratados endodonticamente, apresenta resultados funcionais e estéticos satisfatórios, além de possibilitar uma maior sobrevida aos mesmos(AU)

The purpose of this case report was to describe in detail the technique of horizontal transfixion of a fiberglass post into an endodontically treated tooth. Female patient, 51 years old, sought the University Center of Serra Gaúcha (FSG - Caxias do Sul ­ Rio Grande do Sul) with the need to perform the endodontic treatment of molar element number 26. After the initial evaluation, endodontics was performed. The element had little support for the buccal and palatal walls, so an intraradicular postplacement followed by a crown was proposed, for financial reasons the patient did not accept it. Therefore, the technique of horizontal transfixion of a fiberglass pin was proposed, associated with a restoration of direct composite resin. The procedure was performed in a single session and a number 1 fiberglass post was fixed crosswise between the mesiopalatal and distobuccal walls. The restoration was carried out with composite resin Filtek Z350, restoring aesthetics and function. It can be concluded that the horizontal transfixion of a fiberglass post associated with composite resin technique is a restorative alternative that allows greater resistance to endodontically treated teeth, provides satisfactory esthetics and better survival rates(AU)

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