RESUMO
INTRODUCTION: Orthodontic treatment using clear aligners has experienced exponential growth since its introduction in the late 1990s. Three-dimensional (3D) printing has also grown in popularity among orthodontists, and companies have begun to produce resins to directly print clear aligners. This study aimed to examine the mechanical properties of commercially available thermoformed aligners and direct 3D-printed aligners under laboratory conditions and a simulated oral environment. METHODS: Samples were prepared (approximately 2.5 × 20 mm) from 2 thermoformed materials, EX30 and LD30 (Align Technology Inc, San Jose, Calif), as well as 2 direct 3D-printing resins, Material X (Envisiontec, Inc; Dearborn, Mich) and OD-Clear TF (3DResyns, Barcelona, Spain). Wet samples were subjected to phosphate-buffered saline at 37°C for 7 days, whereas dry samples were stored at 25°C. Tensile and stress relaxation tests were carried out on an RSA3 Dynamic Mechanical Analyzer (Texas Instruments, Dallas, Tex) and Instron Universal Testing System (Instron, Norwood, Mass) to calculate elastic modulus, ultimate tensile strength, and stress relaxation. RESULTS: The elastic modulus of dry and wet samples was 103.2 ± 17.3 MPa and 114.4 ± 17.9 MPa (EX30), 61.3 ± 9.18 MPa and 103.5 ± 11.4 MPa (LD30), 431.2 ± 16.0 MPa and 139.9 ± 34.6 MPa (Material X), and 38.4 ± 14.7 MPa and 38.3 ± 8.4 MPa (OD-Clear TF), respectively. The ultimate tensile strength of dry and wet samples was 64.41 ± 7.25 MPa and 61.43 ± 7.41MPa (EX30), 40.04 ± 5.00 MPa and 30.09 ± 1.50 MPa (LD30), 28.11 ± 3.75 MPa and 27.57 ± 4.09 MPa (Material X), and 9.34 ± 1.96 MPa and 8.27 ± 0.93 MPa (OD-Clear TF), respectively. Residual stress of wet samples at 2% strain for 2 hours was 59.99 ± 3.02% (EX30), 52.57 ± 12.28% (LD30), 6.98 ± 2.64% (Material X), and 4.39 ± 0.84% (OD-Clear TF). CONCLUSIONS: There was a significant difference in elastic modulus, ultimate tensile strength, and stress relaxation among the samples tested. Moisture, specifically a simulated oral environment, appears to have a greater effect on the mechanical properties of direct 3D-printed aligners when compared with thermoformed aligners. This is likely to impact the ability of 3D-printed aligners to generate and maintain adequate force levels for tooth movement.
Assuntos
Impressão Tridimensional , Técnicas de Movimentação Dentária , Humanos , Módulo de Elasticidade , Texas , Teste de MateriaisRESUMO
Bisphenol A (BPA) from dental materials may be linked to children's health issues. This study aimed to assess the release of BPA from commercially available 3-dimensional (3D)-printed resin materials and evaluate BPA-related apoptotic effects on human periodontal ligament cells and gingival fibroblasts. Commercially available 3D-printed resin materials for prosthodontic use were selected as follows: NextDent C&B MFH (3D Systems, Rock Hill, SC, USA), DIOnavi-P. MAX (Dio Co., Busan, Korea), and DIOnavi-Denture02 (Dio Co., Busan, Korea). Identical cuboidal samples (1 cm × 1 cm × 0.5 cm) were printed from the materials and cured. BPA release was assessed using liquid chromatography/mass spectrometry (LC/MS). In addition, human gingival fibroblasts and periodontal ligament cells were exposed to various BPA solutions based on the LC/MS results. Cell Counting kit-8 (CCK-8) and real-time polymerase chain reaction analyses were performed to evaluate BPA-related apoptotic effects. The LC/MS analysis confirmed that none of the 3D-printed resin materials released BPA after curing. Both human gingival fibroblasts and periodontal ligament cells showed lower viability after BPA exposure. Regarding apoptosis-related gene expression, Caspase10 (CASP10) expression in periodontal ligament cells was significantly different in the BPA solutions (p < 0.05). The expression of BAX and Capspase8 (CASP8) in gingival fibroblasts was significantly increased by BPA in a dose-dependent manner (p < 0.05). Within the limitations of this study, the 3D-printed resin materials were not found to release BPA. This finding implies that 3D-printed resin materials are not associated with potential BPA-related risks in children.
Assuntos
Materiais Dentários , Fenóis , Criança , Humanos , Materiais Dentários/química , Fenóis/farmacologia , Fenóis/análise , Fenóis/química , Compostos Benzidrílicos/toxicidade , Compostos Benzidrílicos/análise , Compostos Benzidrílicos/química , Apoptose , Teste de Materiais , Resinas Compostas/químicaRESUMO
INTRODUCTION: Developments in dental materials, CAD/CAM technologies and adhesive dentistry have improved the application of conservative restorations such as endocrowns and onlays. Among ceramics, zirconia has properties such as high strength, transformation toughening, chemical and structural durability, and biocompatibility, which enable zirconia to be used in the posterior area. AIM: This study is a comparative evaluation of fracture resistance and failure modes in endodontically treated molars restored with zirconia endocrown and onlays. MATERIALS AND METHODS: This study was performed on 20 human mandibular first molars with similar dimensions. After root canal treatment, the samples were divided into two groups: endocrowns and onlays (n=10). Restorations were made using a CAD-CAM milling machine with zirconia CAD blocks and, after cementation, subjected to 10,000 thermocycling and 500,000 fatigue cycle procedures, respectively. Each specimen was placed on a Universal Testing Machine and subjected to axial compressive force applied at a crosshead speed of 0.5 mm/min. The mean loads of failure of each group were statistically compared using the Student t-test. Chi-square tests were used to compare frequencies of failure modes among groups. RESULTS: Fracture resistance showed a statistically significant difference between endocrown (5374.6810±670.03445 N) and onlay (3312.5000±804.01428 N) (p<0.001). No statistically significant difference was detected in the distribution of failure types among the groups (p>0.05). CONCLUSIONS: The fracture resistance of endocrown is substantially higher than that of onlay, and failure type does not differ in both restorations. Zirconia is a reliable material to use in conservative restorations.
Assuntos
Coroas , Dente Molar , Humanos , Teste de Materiais , ZircônioRESUMO
INTRODUCTION: Masticatory pressure increases in the distal areas of the dentition. This should be considered when restoring partially edentulous patients with a metal-free fixed partial denture (FPD). An alternative abutment preparation design can be used in order to increase the materials' volume in the most fracture-prone "connector area" of an FPD. The increased size of the connection might positively influence the constructions' mechanical durability, thereby increasing its success and survivability. AIM: The aim of the present study was to investigate the influence of two preparation designs of the distal abutment on the fracture resistance of three-unit, monolithic, ZrO2 FPDs. MATERIALS AND METHODS: 3D printed replicas of a partially edentulous mandibular segment and a ZrO2, milled in full-contour, three-unit FPDs were used for this investigation. Two experimental groups (n=10 ) were defined based on the preparation design of the distal abutment tooth - classical shoulder preparation 0.8 mm deep, and endocrown preparation with a 2-mm retention cavity. The bridge - mandibular segment replica assembly was done with relyXU200(3M ESPE, USA), light-cured for 10 seconds per side with D-light Duo (GC, Europe). After cementation the test specimens were subjected to loading in a universal testing machine Zwick (Zwick-Roell Group, Germany). Statistical analysis was performed using R and includes descriptive statistics, t-test for quantitative and chi-squared test for qualitative variables. RESULTS: The results showed no difference between the two studied groups in the maximum force required to fracture the test specimens [t=-1.8088 (17.39), p-value=0.087; P>0.05]. 95% of the fracture lines were located in the distal connector. CONCLUSIONS: Within the limitations of this study, it can be concluded that both tested preparation designs show similar results in terms of the load required to fracture the test specimens. Furthermore, it is confirmed that the distal connector is the weakest area of an all-ceramic 3-unit FPD in the posterior area.
Assuntos
Planejamento de Dentadura , Zircônio , Humanos , Teste de Materiais , Projetos de Pesquisa , CerâmicaRESUMO
BACKGROUND: It is unclear which crown materials are optimum to disperse the generated stresses around dental implants. The objective of this study is to assess stress distribution and fracture resistance of green reprocessed Polyetheretherketone (PEEK) in comparison to un-reprocessed PEEK and zirconia single implant crown restorations. METHODS: Twenty crowns (n = 20) were obtained, five from zirconia and fifteen from pressed PEEK that were subdivided into 3 groups of five specimens each (n = 5) according to weight% of reprocessed material used. A 100% new PEEK was used for the first group, 50% new and 50% reprocessed PEEK were used for the second group, and a 100% reprocessed PEEK was used for the third group. Epoxy resin model with dental implant in the second mandibular premolar was constructed with strain gauges located mesially and distally to the implant to record strain while a load of 100 N was applied with 0.5 mm/min then specimens of all groups were vertically loaded till failure in a universal testing machine at cross head speed 1 mm/min. Data was statistically analyzed by using One-way Analysis of Variance (ANOVA) followed by Post-hoc test when ANOVA test is significant. RESULTS: No significant difference between strain values of tested groups (p = 0.174) was noticed. However, a significant difference between fracture resistance values was noticed where the zirconia group recorded a significantly higher value (p < 0.001). CONCLUSIONS: Implant restorative materials with different moduli of elasticity have similar effects regarding stresses distributed through dental implant and their surrounding bone. Reprocessed PEEK implant restorations transmit similar stresses to dental implant and surrounding bone as non-reprocessed PEEK and zirconia restorations. Zirconia failed at higher load values than all tested PEEK restorations but all can be safely used in the posterior area as crown restorations for single implants. CLINICAL RELEVANCE: Applying "green dentistry" principles may extend to include reprocessing of pressed PEEK restorative materials without affecting the material's shock absorption properties.
Assuntos
Implantes Dentários , Humanos , Análise do Estresse Dentário , Coroas , Polietilenoglicóis , Cetonas , Materiais Dentários , Teste de Materiais , Falha de Restauração Dentária , TitânioRESUMO
OBJECTIVE: The study aims to evaluate the wear surface using 3D surface roughness and other material characterization of zirconia fabricated using photopolymerization based Lithography-based Ceramic Manufacturing (LCM). METHOD: LCM technology was used to fabricate zirconia specimens of size 10 × 10 × 2mm3. Scanning Electron Microscope, 3D-profilometer, X-ray Diffraction, and hardness test characterized the samples before and after wear and Coefficient of friction (COF) was monitored. RESULT: The COF was around 0.7 and did not differ much between the horizontally and vertically printed specimens. However, the surface roughness after wear for horizontally printed specimen was 0.567 ± 0.139 µm, while that for vertically printed specimen was 0.379 ± 0.080 µm. The reduced valley depth and the dale void volume were low for the vertically printed zirconia specimen, indicating lesser voids and low fluid retention. In addition, it was observed that the hardness value of the vertically printed sample was better. The scanning electron microscopic images and 3D surface profiles of the zirconia specimens depicted the surface topography and revealed the wear track. CONCLUSION: The study shows that zirconia fabricated using LCM technology possesses surface roughness of about 0.5 µm with no machining scars that are usually associated with CAD/CAM dentistry and also indicating agreement with clinically acceptable values for minimal surface roughness of dental restorations. Dental restorations using LCM fabricated zirconia redues the requirement of post-processing work flow that is part of CAD/CAM dentistry.
Assuntos
Cerâmica , Porcelana Dentária , Humanos , Zircônio , Desenho Assistido por Computador , Propriedades de Superfície , Teste de Materiais , Materiais DentáriosRESUMO
The aim of this study was to clarify the effect of universal adhesive (UA) viscosity on the bond strength of resin composite to dentin prepared with Er:YAG laser. Four experimental UAs (SI-1, SI-2, SI-3, and SI-4) were developed by adding 1, 2, 3, and 4 wt/% nanosilica to BeautyBond Xtreme (Shofu), respectively. BeautyBond Xtreme was used as a control (SI-0). The viscosities of experimental UAs were measured using a B-type viscometer. After bovine mandibular anterior teeth were ground with #600 emery paper to obtain the flattened dentin surfaces, the dentin surfaces were cut thinly by irradiating the Er:YAG laser. Specimens were prepared using the respective UA and flowable resin composite and subjected to the microtensile bond strength (µTBS) test. The data from viscosity measurement and the µTBS test were statistically analyzed using the Kruskal-Wallis test. The mean values of viscosity significantly differed among the all experimental groups (p < 0.01). The µTBS of SI-1 and SI-2 was significantly higher than that of SI-0, SI-3, and SI-4 (p < 0.001). The µTBS of SI-0 was significantly lower than that of SI-4 (p < 0.001). The viscosities of the experimental universal adhesives significantly affected their bond strength to laser-cut dentin.
Assuntos
Adesivos , Lasers de Estado Sólido , Animais , Bovinos , Adesivos/farmacologia , Viscosidade , Dentina , Resistência à Tração , Cimentos de Resina/química , Resinas Compostas/química , Adesivos Dentinários/química , Teste de MateriaisRESUMO
Background: During orthodontic treatment, teeth with brackets may sometimes be restored with different restorative materials. In this case, the content of the orthodontic adhesive selected for bracket bonding may also be important. Aim: This study compared the bond strength of metal orthodontic brackets adhered to different resin composite and glass ionomer cement (GIC) restoration surfaces with glass ionomer-based and resin-based orthodontic adhesives to determine the best orthodontic adhesive for use in restored teeth. Material and Methods: This study prepared 80 discs. Four material groups of 20 discs were created: reinforced high-viscosity GIC, high-viscosity GIC, flowable bulk-fill resin composite, and nanohybrid resin composite. Specimens in each material group were divided into two subgroups that differed in the orthodontic adhesive used to bond the brackets to the prepared specimens. After 24 hours, the specimens were shear bond strength (SBS) tested at 1 mm/min using a universal tester. Results: The SBS of glass ionomer-based orthodontic adhesive differed significantly between metal brackets adhered to different bases (P < 0.001). The highest SBSs were observed between metal brackets and high-viscosity glass ionomer restorations (6.79 ± 2.38). The highest SBSs observed with a resin-based orthodontic adhesive were between metal brackets adhered to nanohybrid resin composite restorations (8.84 ± 2.10; P = 0.030). Conclusions: Glass ionomer-based orthodontic adhesive provided safer bond strength and demineralization prevention when applying metal brackets to teeth with glass ionomer restorations.
Assuntos
Colagem Dentária , Braquetes Ortodônticos , Humanos , Teste de Materiais , Resinas Compostas/química , Resinas Acrílicas/química , Dióxido de Silício , Cimentos de Ionômeros de Vidro/química , Cimentos de Resina/química , Resistência ao Cisalhamento , Análise do Estresse DentárioRESUMO
OBJECTIVE: To explore and characterize the effect of the discrepancy between crestal bone height (CB) and pulp chamber floor (PCF) in the fatigue performance of endodontically-treated teeth rehabilitated with an endocrown restoration. MATERIALS AND METHODS: A total of 75 human molars free of defects, caries history or cracks were selected, then endodontically treated and randomly allocated into 5 groups (N = 15) according to the difference between PCF and CB, as follows: PCF 2 mm above, PCF 1 mm above, PCF leveled, PCF 1 mm below and PCF 2 mm below. Endocrown restorations were made with composite resin (Tetric N-Ceram, shade B3, Ivoclar) in 1.5 mm thickness and luted with a resin cement (Multilink N, Ivoclar) onto the dental elements. Monotonic testing was performed to define the fatigue parameters, and a cyclic fatigue test was used until failure of the assembly. The collected data were submitted to statistical survival analysis (Kaplan-Meier followed by Mantel-Cox and Weibull), fractographic analysis and finite element analysis (FEA) were performed as complementary analyzes. RESULTS: The PCF 2 mm below and PCF 1 mm below groups presented the best results regarding fatigue failure load (FFL) and number of cycles for failure (CFF) (p < 0.05), but presented no difference between each other (p > 0.05). The PCF leveled and PCF 1 mm above groups presented no statistical difference between them (p > 0.05), but performed better than the PCF 2 mm above group (p < 0.05). The rate of favorable failures of PCF 2 mm above, PCF 1 mm above, PCF leveled, PCF 1 mm below and PCF 2 mm below groups were 91.7%, 100%, 75%, 66.7% and 41.7%, respectively. FEA showed different stress magnitudes according to the pulp-chamber design. CONCLUSION: The insertion level of the dental element to be rehabilitated with an endocrown interferes in the mechanical fatigue performance of the set. The discrepancy between the CB height and the PCF has a direct effect, where the higher the PCF in relation to the CB, the greater the risk of mechanical failure of the restored dental element.
Assuntos
Cavidade Pulpar , Dente não Vital , Humanos , Cerâmica , Resinas Compostas , Desenho Assistido por Computador , Coroas , Porcelana Dentária , Falha de Restauração Dentária , Análise do Estresse Dentário , Teste de Materiais , Propriedades de SuperfícieRESUMO
BACKGROUND: The purpose of the current study was to assess the impact of restoration thickness, surface conditioning and the interaction between them on the fracture resistance of CAD/CAM fabricated lithium disilicate occlusal veneers. METHODS: A total of 42 maxillary molars were prepared to receive CAD/CAM fabricated lithium disilicate occlusal veneer either with 0.5 mm (n = 21) or 1 mm (n = 21) thickness. Each main group was divided into 3 subgroups (n = 7), according to surface treatment, HF acid (HF-1, HF-0.5), acidulated phosphate fluoride (APF-1, APF-0.5) and Monobond etch & prime (MON-1, MON-0.5). Multilinik N (Ivoclar-Vivadent) adhesive resin cement was used for bonding according to the manufacturer instructions. One hour after bonding, specimens were stored in water bath for 75 days followed by cyclic loading fatigue for 240,000 cycles to simulate clinical situation. Finally, specimens were fractured under compressive load in (N) using a universal testing machine. Two and one-way ANOVA and Post Hoc Tukey test were used for statistical analysis. RESULTS: The means ± SD (N) fracture load for each group were calculated. MON-1 group showed the highest fracture load (1644.7 ± 155.3) followed by HF-1 group (1514.6 ± 212.5). Meanwhile, APF-0.5 showed the lowest fracture load (962 ± 249.6). CONCLUSION: CAD/CAM fabricated lithium disilicate occlusal veneers can be used with a thickness of 0.5 mm instead of conventional crowns. Monobond etch & prime is recommended as a surface treatment for CAD/CAM fabricated lithium disilicate occlusal veneer due to biological hazards of Hydrofluoric acid.
Assuntos
Cerâmica , Porcelana Dentária , Humanos , Cerâmica/química , Teste de Materiais , Porcelana Dentária/química , Coroas , Desenho Assistido por Computador , Análise do Estresse Dentário , Falha de Restauração DentáriaRESUMO
AIM: The aim of this study is to evaluate and compare the impact strength of conventional acrylic resin, high-impact acrylic resin, high-impact acrylic resin reinforced with silver nanoparticles, and high-impact acrylic resin reinforced with a zirconium oxide powder. MATERIALS AND METHODS: A total of 60 samples were prepared of dimensions 60 mm length × 7 mm width × 4 mm thickness to test impact strength. Machined stainless steel dies of the same dimension were used to form molds for the fabrication of these samples. Of 60 samples, 15 samples were prepared each from conventional acrylic resin (Group A1), high-impact acrylic resin (Group A2), acrylic resin reinforced with silver nanoparticles (Group A3), and acrylic resin reinforced with zirconium oxide powder (Group A4). Izod-Charpy pendulum impact testing machine was used. RESULTS: The impact strength of group A1 was in the range of 2.83-3.30 kJ/m2 (M = 3.12 kJ/m2, SD = 0.16), group A2 was in range of 5.10-5.78 kJ/m2 (M = 5.51 kJ/m2, SD = 0.18), group A3 was in range 3.18-3.56 kJ/m2 (M = 3.37 kJ/m2, SD = 0.11), and group A4 was in range 7.18-7.78 kJ/m2 (M = 7.5 kJ/m2, SD = 0.18). Statistical analysis using one-way ANOVA and t-test revealed significant differences (p < 0.001). CONCLUSION: High-impact acrylic resin reinforced with zirconium oxide powder has the highest impact strength. CLINICAL SIGNIFICANCE: This research sheds light on the usefulness of novel filler materials in clinical prosthodontics.
Assuntos
Resinas Acrílicas , Nanopartículas Metálicas , Pós , Prata , Polimetil Metacrilato , Bases de Dentadura , Teste de MateriaisRESUMO
PURPOSEï¼The purpose of this study was to evaluate the effect of various storage methods on shear bond strength of enamel of bovine teeth and find the storage condition that could preserve the similar bond strength as the freshly extracted teeth. METHODS: One hundred and thirty freshly extracted bovine teeth were divided into 13 groups. One was the reference group and 12 were the experimental group. Each group contained 10 teeth. Teeth in the reference group were operated on the same day as the teeth were extracted, while teeth in the experimental groups were stored in different methods (4% formaldehyde solution at 4 â, 23 â, 1% chloramine T at 4 â, 23 â, distilled water at 4 â, 23 â). After stored for 30 days and 90 days, the bovine teeth were taken out and then the shear bond strength was tested. The data were analyzed with SPSS 20.0 software package. RESULTS: The bovine teeth stored in 4% formaldehyde and 1% chloramine T at 23 â and in distilled water at 4 â achieved similar bond strength as freshly extracted teeth at 30 days and 90 days, and the bond strength did not change over time. The bovine teeth stored in 4% formaldehyde solution and 1% chloramine T at 4 â at 30 days had higher shear bond strength than freshly extracted bovine teeth, but over time the bond strength reduced and reached the similar level at 90 days. The bovine teeth stored in distilled water at 23 â obtained similar bond strength as freshly extracted teeth at 30 days but over time the bond strength reduced until 90 days. CONCLUSIONS: Bovine teeth stored in 4% formaldehyde solution and 1% chloramine T at 23 â and in distilled water at 4 â achieved similar bond strength as freshly extracted teeth and does not change over time. These three methods are recommended for storing bovine teeth.
Assuntos
Colagem Dentária , Bovinos , Animais , Colagem Dentária/métodos , Esmalte Dentário , Formaldeído/química , Água/química , Resistência ao Cisalhamento , Cimentos de Resina , Teste de Materiais , Análise do Estresse DentárioRESUMO
PURPOSE: The purpose of this in vitro study was to measure the color difference(â³E) on titanium alloy background and translucency parameter(TP) of four kinds of zirconia-based all-ceramic specimens, providing a clinical reference for restoring grayish abutment. METHODS: Four groups with a total of 24 ceramic specimens were fabricated to a final specimen dimension of 14 mm×14 mm×1.5 mm, two kinds of zirconia with different translucencyï¼Beitefu high-translucency, Cercon low-translucencyï¼and their corresponding body porcelain at the shade of A2 were used as followed:high-translucency zirconia sintered dentine porcelain(Group A),low-translucency zirconia sintered dentine porcelain(Group B),high-translucency zirconia sintered opaque and dentine porcelain(Group C),low-translucency zirconia sintered opaque and dentine porcelain(Group D).The color parameters of the specimens under two backgrounds (titanium alloy and shade A3 light-activated resin-based composite) were measured by Shade Eye NCC colorimeter, then the â³E value was determined by the relevant equations. The color parameters under black and white background were measured, and TP value was calculated. The experimental data were analyzed with SPSS 17.0 software package. RESULTS: There was significant difference of the TP value and the â³E value among four groups specimens(Pï¼0.05), the TP value was arranged as follows: group Dï¼group Cï¼group Bï¼group A. The specimen used with opaque porcelain showed significantly reduced translucency. The â³E value was arranged as follows: group D ï¼ group C ï¼ group B ï¼ 1.5 ï¼ 2 ï¼group A, the â³E value of group A cannot be accepted in clinic. CONCLUSIONS: The restoration of low-translucency zirconia sintered translucency veneering ceramic has better translucency, with value of â³Eï¼1.5 when used on the grayish abutment, which has a good aesthetic performance.
Assuntos
Porcelana Dentária , Titânio , Cor , Teste de Materiais , Cerâmica , Zircônio , Propriedades de SuperfícieRESUMO
AIM: This study aimed to compare the best restorative approach for the conservative class I cavity by comparing flowable and nanohybrid composites versus the placement technique regarding surface microhardness, porosity, and presence of interface gaps. MATERIALS AND METHODS: Forty human molars were divided into four groups (n = 10). Standardized class I cavities were prepared and restored using one of the following materials: Group I - Flowable composite placed by incremental technique; group II - Flowable composite placed in one increment; group III - Nanohybrid composite placed by incremental technique; and group IV - Nano-hybrid composite placed in one increment. After finishing and polishing, specimens were sectioned into two halves. One section was chosen randomly for the Vickers microhardness (HV) evaluation and the other section was used for the assessment of porosities and interfacial adaptation (IA). RESULTS: The surface microhardness range was 28.5-76.2 (p < 0.05), mean pulpal microhardness range was 27.6-74.4 (p < 0.05). Flowable composites had lower HV than conventional counterparts. The mean pulpal HV of all materials exceeded 80% of occlusal HV. Restorative approaches did not statistically differ in porosities. However, IA percentages were higher in flowable materials compared to nanocomposites. CONCLUSION: Flowable resin composite materials have lower microhardness than Nanohybrid composites. In small class I cavities, the number of porosities was similar between the different placement techniques and the interfacial gaps were highest in the flowable composites. CLINICAL SIGNIFICANCE: The use of nanohybrid resin composite to restore class I cavities will result in better hardness and less interfacial gaps compared to flowable composites.
Assuntos
Cárie Dentária , Restauração Dentária Permanente , Humanos , Resinas Compostas , Materiais Dentários , Restauração Dentária Permanente/métodos , Dureza , Teste de Materiais , PorosidadeRESUMO
PURPOSE: EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride) can increase dentin bonding longevity. This study aimed to evaluate the effect of final irrigation of the root canal with EDC on the bond strength (BS) longevity of an epoxy resin-based root-canal sealer. MATERIALS AND METHODS: Twenty maxillary canines were sectioned and standardized for root length at 17 mm. Roots were instrumented and distributed into 2 groups according to the final irrigation protocol: EDTA 17%+NaOCl 2.5% (C) and EDTA 17%+NaOCl 2.5%+EDC 0.5M (EDC). The canals were dried and filled with AH Plus (Dentsply Sirona). Three slices were obtained per third, and the first slice from each third was used for the immediate push-out test (i) followed by analysis of the failure pattern (n = 10); the second slice from each third was used for the push-out test after 6-month aging (A) followed by analysis of the failure pattern (n = 10); the third slice from each third was used to examine the adhesive interface under confocal laser scanning microscopy (CLSM) (n = 10). Data were analyzed with ANOVA, Fisher's exact and Kruskal-Wallis tests. RESULTS: Higher BSs were found for EDC-A (5.6 ± 1.9) than for EDC-I (3.3 ± 0.7), C-i (2.5 ± 1.0) and C-i (2.6 ± 1.0) (p = 0.0001), while C-A values were in some cases similar to C-i and in others similar to EDC-i. No statistically significant difference was observed between the thirds (p > 0.05), except for EDC-i, which showed lower BS for the cervical (2.79 ± 0.46) compared to the apical third (3.8 ± 0.5), while the middle third in some cases had values similar to those of the apical and in others to the cervical third (3.2 ± 0.7) (p = 0.032). More mixed adhesive failures were found in the cervical third, and more adhesive failures to the sealer occurred in the middle and apical thirds (p = 0.014). A significant difference was observed between treatments in terms of adaptation of the adhesive interface, with a higher percentage of good adaptation using EDC (66.7%) than using C (40%), and a lower percentage of poor adaptation with EDC (10%) compared to C (20%) (p < 0.05). CONCLUSION: Root canal irrigation with EDC increased the longevity of the adhesive interface of an epoxy resin-based root-canal sealer.
Assuntos
Colagem Dentária , Materiais Restauradores do Canal Radicular , Resinas Epóxi/química , Materiais Restauradores do Canal Radicular/química , Ácido Edético/química , Carbodi-Imidas , Cimentos Dentários , Dentina , Teste de Materiais , Cavidade Pulpar , Irrigantes do Canal RadicularRESUMO
The aim of this work was to investigate the elution of residual monomers as a function of the manufacturing process, which are CAD/CAM manufacturing, self-curing and 3D printing. The experimental materials used consisted of the base monomers TEGDMA, Bis-GMA and Bis-EMA and 50 wt.% fillers. Additionally, a 3D printing resin without fillers was tested. The elution of the base monomers into the different media (water, ethanol and ethanol/water (75/25 vol. %)) at 37 °C over a period of up to 120 d as well as the degree of conversion (DC) by FTIR were investigated. No monomer elution could be detected in water. Most residual monomers in both other media were released from the self-curing material whereas the 3D printing composite released relatively little. The CAD/CAM blanks released hardly any quantitatively detectable amounts of monomers. Relative to the base composition, TEGDMA eluted less than Bis-GMA and Bis-EMA. DC did not correlate with residual monomer release; thus, leaching was determined not only by the amount of residual monomers present but by further factors as possibly network density and structure. The CAD/CAM blanks and the 3D printing composite showed similar high DC but lower residual monomer release from the CAD/CAM blank, likewise the self-curing composite and the 3D printing resin exhibited similar DC but different monomer elution. In terms of residual monomer elution and DC, the 3D printing composite seems promising as a new material class for the use as temporary dental crowns and bridges.
Assuntos
Resinas Compostas , Água , Bis-Fenol A-Glicidil Metacrilato/química , Resinas Compostas/química , Teste de Materiais , Impressão Tridimensional , Etanol , Coroas , Materiais DentáriosRESUMO
Porous titanium alloy implants with simulated trabecular bone fabricated by 3D printing technology have broad prospects. However, due to the fact that some powder adheres to the surface of the workpiece during the manufacturing process, the surface roughness in direct printing pieces is relatively high. At the same time, since the internal pores of the porous structure cannot be polished by conventional mechanical polishing, an alternative method needs to be found. As a surface technology, plasma polishing technology is especially suitable for parts with complex shapes that are difficult to polish mechanically. It can effectively remove particles and fine splash residues attached to the surface of 3D printed porous titanium alloy workpieces. Therefore, it can reduce surface roughness. Firstly, titanium alloy powder is used to print the porous structure of the simulated trabecular bone with a metal 3D printer. After printing, heat treatment, removal of the supporting structure, and ultrasonic cleaning is carried out. Then, plasma polishing is performed, consisting of adding a polishing electrolyte with the pH set to 5.7, preheating the machine to 101.6 °C, fixing the workpiece on the polishing fixture, and setting the voltage (313 V), current (59 A), and polishing time (3 min). After polishing, the surface of the porous titanium alloy workpiece is analyzed by a confocal microscope, and the surface roughness is measured. Scanning electron microscopy is used to characterize the surface condition of porous titanium. The results show that the surface roughness of the whole porous titanium alloy workpiece changed from Ra (average roughness) = 126.9 µm to Ra = 56.28 µm, and the surface roughness of the trabecular structure changed from Ra = 42.61 µm to Ra = 26.25 µm. Meanwhile, semi-molten powders and ablative oxide layers are removed, and surface quality is improved.
Assuntos
Ligas , Titânio , Ligas/química , Titânio/química , Porosidade , Pós , Polônia , Propriedades de Superfície , Impressão Tridimensional , Teste de MateriaisRESUMO
BACKGROUND: Splinted multiunit cement-retained restorations with screw access channels over engaging abutments are viable implant prosthetic options. However, information regarding the maximum degree of divergence between multiple implants is lacking. The purpose of this in vitro study was to determine the maximum degree of divergence between 2 adjacent implants with conical connections that allows insertion and removal of splinted restorations with engaging preparable abutments or titanium base abutments. METHODS: Two implants were aligned in a stone base, one straight and the other at an angle ranging from 0 to 20 degrees. The implants represented an implant system that had an internal conical connection and a hexed abutment engaging the base of the connection. Two straight preparable engaging cement retained abutments were screwed onto the implants and splinted together using acrylic resin. A total of 11 angles were tested, with 7 specimens for every angle. Evaluation of dislodging force was performed by pulling out the splinted abutments after unscrewing them. This was performed subjectively by 3 blinded investigators who applied a tactile pulling force. A scale of 0-10 was used to estimate the pulling force. Objectively the dislodging force was measured in Newtons using a universal testing machine. A statistical correlation was made between the subjective and objective dislodging force values using Spearman's rank correlation coefficient. RESULTS: The mean subjective values increased gradually from 0 to 16 degrees. A sudden rise was noticed at 18 degrees (9.71 ± 0.23) and, at 20 degrees, the investigators were not able to remove the splinted abutments from the implants. The mean objective dislodgement force values increased gradually from 0 to16 degrees and abruptly from 16 degrees (13.57 ± 0.45 N) to 18 degrees (25.40 ± 0.66 N) and 20 degrees (35.22 ± 0.64). The correlation between the subjective and the objective evaluations assessed using the Spearman's rank correlation coefficient was 0.98 indicating a statistically significant correlation (P < .001). As the objective dislodging force increased, the subjective dislodgement difficulty increased. CONCLUSIONS: Splinting cement retained restorations with screw access channels on engaging abutments is possible when multiple implants with conical connections having an internal flare angle of 8 degrees are used, with implant divergence of up to 16 degrees.
Assuntos
Implantes Dentários , Humanos , Cimentos Dentários , Cimentos de Ionômeros de Vidro , Coroas , Titânio , Análise do Estresse Dentário , Prótese Dentária Fixada por Implante , Teste de MateriaisRESUMO
BACKGROUND: This study aimed to evaluate the surface hardness (VHN) and biaxial flexural strength (BFS) of dual-cured bulk-fill restorative materials after solvent storage. METHODS: Two dual-cured bulk-fill composites (Surefil One® and Activa™ Bioactive), a light-cured bulk-fill composite (Filtek One Bulk-Fill) and a resin-modified glass ionomer (Fuji II LC) were investigated. Surefil One and Activa were used in the dual-cure mode, all materials were handled according to manufacturer's instructions. For VHN determination, 12 specimens were prepared from each material and measured after 1 h (baseline), 1 d, 7 d and 30 d of storage in either water or 75% ethanol-water. For BFS test, 120 specimens were prepared (n = 30/material) and stored in water for either 1, 7 or 30 d before testing. Repeated measures MANOVA, two-way and one-way ANOVA followed by the Tukey post hoc test (p ≤ 0.05) were used to analyze the data. RESULTS: Filtek One had the highest VHN, while Activa had the lowest. All materials exhibited a significant increase in VHN after 1d of storage in water, except for Surefil One. After 30 d of storage, VHN increased significantly in water except for Activa, while ethanol storage caused a significant time-dependent reduction in all tested materials (p ≤ 0.05). Filtek One showed the highest BFS values (p ≤ 0.05). All the materials, except for Fuji II LC, exhibited no significant differences between 1 and 30 d BFS measurements (p > 0.05). CONCLUSIONS: Dual-cured materials had significantly lower VHN and BFS compared to the light-cured bulk-fill material. The low results of Activa VHN and Surefil One BFS, indicate that these materials should not be recommended in posterior stress-bearing areas.
Assuntos
Materiais Dentários , Resistência à Flexão , Humanos , Dureza , Solventes , Teste de Materiais , Resinas Compostas , Etanol , ÁguaRESUMO
This in vitro study investigated color stability of two photo-polymerized nano-filled and nano-hybrid composite resins in different polymerization modes immersed in different staining solutions before and after brushing. Disc-shaped specimens (n = 120) were prepared from two composite resins based on filler particle size: nano-filled (Filtek Z350, shade A1, 3M ESPE) and nano-hybrid (Spectra ST-HV, shade A1, Dentsply Sirona) composite resins (n = 60 per composite type). Specimens of each resin type were photopolymerized using the following polymerization modes: LED conventional, ramp, and pulse (n = 20 specimens per resin type and LED mode). After preparation, baseline color of the specimens was evaluated using a spectrophotometer (Easyshade V, VITA), and color change was evaluated using the CIE L*a*b* formula. Specimens were soaked in distilled water for 4 weeks in separate containers. The specimens from each polymerization-mode group were separated into two groups of 10 specimens; one group was stored in tea and the other group was stored in cola, each 1 hour daily for 4 weeks. After 4 weeks, the color was measured again. The specimens were brushed for 2 minutes under 200-g weight using an electronically powered toothbrush on the polymerized side of the specimen. The color was reevaluated immediately after brushing. Color-difference data (ΔE) between groups were analyzed by one-way analysis of variance for main comparison and by independent t test for color change after brushing. Nano-filled composite resin was more color-stable than nano-hybrid composite resin (P < .001), regardless of the staining media. For both composite resin types, the conventional polymerization method produced a more color-stable result (P < .0001). ΔE after brushing was reduced significantly (P < .0001). Both staining solutions have significant effects on color change, with tea staining more than cola (P < .0001). Nanofilled composite resin had greater color stability than nano-hybrid composite resin after immersion in staining solutions. Polymerization mode influences the color stability of both composite resin types. Int J Periodontics Restorative Dent 2023;43:247-255. doi: 10.11607/prd.6427.
