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1.
J Prosthet Dent ; 2024 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-38184396

RESUMO

STATEMENT OF PROBLEM: Reasons associated with the failure of facial prosthesis are of major concern and may be associated with deterioration of both elastomeric materials and magnetic attachments. However, the extent of deterioration of these components is unclear. PURPOSE: The purpose of this in vitro study was to evaluate selected retrieved facial prostheses and provide information regarding the electrochemical characterization of the recovered magnetic attachments. MATERIAL AND METHODS: Five facial prostheses (RP1, RP2, RP3, RP4, RP5) fabricated at the University of Texas, M.D. Anderson Cancer Center were retrieved following clinical use. The intaglio and external surfaces of the prostheses along with the incorporated magnetic attachments were photographed. The areas with the detected failures on the retrieved prostheses, as well as the recovered magnetic attachments, were evaluated under a reflected light stereomicroscope at ×16 nominal magnification and photographed with a digital camera. Five magnetic attachments recovered from the prostheses (retrieved group RT) were evaluated for degradation of their corrosion resistance after electrochemical testing in artificial sweat solution and were compared with 5 unused magnetic attachments (control group, CT). To identify the elemental composition of the intact magnet surface, 1 specimen from the control group was investigated by X-ray energy dispersive spectroscopy (EDS). Means and standard deviations of the open circuit potential (EOCP), the zero-circuit potential (Ecorr), and Icorr were calculated and statistically analyzed by a t test (α=.05 for all tests). RESULTS: The main reasons of failure were discoloration, degradation and rupture of the silicone elastomer, marginal misfit, and delamination of the polyurethane sheet. Additional findings were tarnish and discoloration of the magnetic attachments accompanied by considerable smear build-up. EDS results verified the Ni plating of tested magnets. Electrochemical testing revealed that retrieved magnets showed significantly lower OCP (P<.001) and Ecorr (P<.001) but similar Icorr (P=0.083) while the pseudopassivity region of unused magnets vanished in the retrieved group, denoting a degradation of electrochemical properties after clinical use. CONCLUSIONS: In vivo aging exerts extended degradation on the elastomer part of facial prostheses as well as deterioration of their surface integrity and electrochemical properties.

2.
J Prosthet Dent ; 132(3): 646.e1-646.e10, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38955601

RESUMO

STATEMENT OF PROBLEM: Three Co-Cr alloy types (Co-Cr-Mo, Co-Cr-W, and Co-Cr-Mo-W) have been commonly used in the fabrication of dental prostheses. These alloys can be manufactured using either conventional casting or selective laser melting (SLM) techniques. Nevertheless, research that directly compares these materials and/or manufacturing processes in terms of their microstructural and mechanical characteristics is sparse. PURPOSE: The purpose of this in vitro study was to conduct microstructural and mechanical analysis via X-ray interpretation, optical microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), image analysis, X-ray diffraction (XRD), instrumented indentation testing (IIT), and 3-point bending testing to characterize Co-Cr-Mo, Co-Cr-W, and Co-Cr-Mo-W alloys produced through conventional casting and SLM. MATERIAL AND METHODS: Six Co-Cr-based alloys were analyzed and divided into 3 types based on their elemental composition (Co-Cr-Mo, Co-Cr-W, and Co-Cr-Mo-W). Additionally, each group was categorized based on the manufacturing process used (casting or SLM). X-ray scans were used to assess porosity. The microstructures of the specimens were assessed through SEM/EDS examination and XRD analysis. IIT was used to determine the Martens hardness (HM) and elastic index (ηIT), while the elastic modulus (E) was estimated through the 3-point bending test. The mechanical properties were statistically analyzed using 2-way analysis of variance (ANOVA) and the Tukey multiple comparison post hoc test, with alloy type and manufacturing process as discriminating variables (α=.05). RESULTS: All cast groups exhibited gross porosity, while no pores or other flaws were found in the SLM groups. Based on the XRD results, the crystalline structure of all Co-Cr specimens consisted of the face-centered cubic γ phase (γ-fcc), along with the hexagonal close-packed ε phase (ε-hcp) and Cr23C6 carbide. Different microstructures were identified between the cast and SLM alloys. Significant differences were identified for the mean standard deviation HM (ranging from 2601 ±94 N/mm2 to 3633 ±61 N/mm2) and mean ±standard deviation ηIT (ranging from 16.8 ±0.3% to 20.9 ±0.3%) among alloys prepared by the same manufacturing process, while all SLM alloys had statistically higher HM and ηIT results than their cast counterparts (P<.05). No statistically significant differences were identified for the mean ±standard deviation Eb (ranging from 170 ±25 GPa to 244 ±36 GPa) among the groups prepared with the same manufacturing process (P>.05), but the SLM alloys had significantly higher results (P<.05) than the cast alloys. CONCLUSIONS: In general, the manufacturing procedure significantly affected the porosity, microstructure, and mechanical properties of the tested Co-Cr alloys. SLM decreased the internal porosity, provided a uniform microstructure, and improved the mechanical properties for all the tested alloy types.


Assuntos
Ligas de Cromo , Técnica de Fundição Odontológica , Lasers , Teste de Materiais , Ligas de Cromo/química , Microscopia Eletrônica de Varredura , Difração de Raios X , Propriedades de Superfície , Espectrometria por Raios X , Dureza , Técnicas In Vitro , Ligas Dentárias/química
3.
Eur J Orthod ; 46(1)2024 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-37936263

RESUMO

OBJECTIVE: The objective of this study was to examine the impact of intraoral aging on the mechanical properties of directly printed aligners (DPA) compared to thermoformed aligners (TA). MATERIALS AND METHODS: This prospective in vivo experiment included three types of aligners: DPAs (group DP) fabricated from Tera Harz TC-85 DAC resin (Graphy, Korea), TA (group INV) made from a polyurethane-based polymer (Align Technology, Inc., CA, USA), and TA (group DUR) made from polyethylene glycol terephthalate based polymer (Scheu-Dental, Germany). Each group was categorized into retrieved (Clin) and unused aligners (Ctr). Thirty patients (10 per group) wore the aligners for 7 days, thereby generating the retrieved samples. Thirty unused aligners were employed as control samples. The following mechanical properties were determined: Martens Hardness (HM), indentation modulus (EIT), elastic index (ηIT), and indentation relaxation (RIT). Intergroup comparisons were conducted using ANOVA/Kruskal-Wallis test. Comparisons between retrieved and control samples were done using Wilcoxon-Mann-Whitney-U/Student's t-test/Welch's test. RESULTS: Statistically significant differences between the groups were found for both control and used samples (P < .001). Pairwise comparisons also revealed significant differences between the samples. The mechanical properties did not differ significantly between unused and retrieved INV- and DUR-aligners, whereas for DP-aligners significant differences for ηIT and RIT were found following intraoral service (P-values .012 and .002, respectively). CONCLUSIONS: Group DUR showed generally more favorable mechanical properties compared to DP and INV. The much higher RIT and EIT in DP aligners suggest their higher rigidity and force decay, which could compromise their clinical efficacy.


Assuntos
Fenômenos Mecânicos , Poliuretanos , Humanos , Estudos Prospectivos , Dureza , Polietilenoglicóis , Teste de Materiais
4.
Eur J Orthod ; 46(1)2024 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-38073597

RESUMO

OBJECTIVES: Three-dimensional (3D)-printed aligners present a promising orthodontic treatment modality, whose clinical success largely depends on the material's mechanical properties. The aim of this study was to evaluate the mechanical properties of resin-made 3D-printed aligners and assess the effect of two different post-curing conditions. MATERIALS AND METHODS: Forty dumbbell-shaped specimens and 40 resin aligners were 3D-printed and divided into four equal groups according to post-curing conditions: presence or absence of oxygen during post-curing and water heat treatment at 85°C for 15 s or none. Samples from the central incisor of the aligner (n = 5/group) were studied by Attenuated Total Reflection Fourier-transform infrared spectroscopy (ATR-FTIR). The dumbbell-shaped specimens were loaded up to fracture under tensile mode and yield strength, ultimate tensile strength, elastic and plastic strain were calculated. The first mandibular molar area from 3D-printed aligners (n = 10/group) was cut and embedded in acrylic resin and then underwent metallographic grinding and polishing followed by instrumented indentation testing to determine the following mechanical properties: Martens hardness, indentation modulus, elastic index, and indentation relaxation. After descriptive statistics, differences according to each post-curing protocol, as well as their combination, were analyzed with linear regression modeling at a 5% significance level. RESULTS: All groups showed identical ATR-FTIR spectra, while no statistically significant effects were seen for either post-curing protocol (N2 presence and heat treatment) or their combination (P > .05 in all instances). CONCLUSIONS: The mechanical properties of 3D-printed resin aligners were not considerably affected either by post-curing in N2 atmosphere or heat treatment.


Assuntos
Temperatura Alta , Dente , Humanos , Dureza , Impressão Tridimensional , Teste de Materiais , Propriedades de Superfície
5.
J Prosthodont ; 2024 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-39185809

RESUMO

PURPOSE: To investigate the effects of the elemental composition and the manufacturing process of cobalt chromium-molybdenum (CoCr-Mo), cobalt chromium-tungsten (CoCr-W), and CoCr-Mo-W alloys on metal-ceramic bond strength. MATERIALS AND METHODS: Six CoCr-based alloys were included in this study, a were classified into three different groups depending on their elemental composition (Ν = 10, for each group). The first group had molybdenum (Mo) as the third alloying element, the second group contained tungsten (W) (without Mo), and the third group included both alloying elements. The groups were further divided by the manufacturing process (casting or selective laser melting, SLM). Interfacial analysis was carried out using backscattered electron imaging (BEI) and energy-dispersive X-ray microanalysis (EDX) operating in line scan mode. The metal-ceramic bond strength was tested by a 3-point bending test according to the ISO 9693 requirements. The fracture mode of all specimens was examined under a stereomicroscope. The bond strength results were statistically analyzed by 2-way ANOVA and Tukey's multiple comparison post hoc test (a = 0.05). RESULTS: A continuous interface with the porcelain was found without pores, debonding areas, or other defects. Of the major elements found at the interface, Co showed the highest diffusion rate, while titanium (Ti) had the lowest diffusion rate. No statistically significant differences were identified in metal-ceramic bond strength either among materials or between manufacturing processes. The fracture mode was found to be cohesive for all specimens. CONCLUSIONS: The metal-ceramic bond strength is independent of the current CoCr alloy type and manufacturing process when comparing conventional casting and SLM. Interfacial analysis revealed no differences between the tested groups.

6.
Orthod Craniofac Res ; 26(3): 476-480, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-36648375

RESUMO

OBJECTIVES: Three-dimensional (3D) printing technology is a promising manufacturing technique for fabricating ceramic brackets. The aim of this research was to assess fundamental mechanical properties of in-office, 3D printed ceramic brackets. MATERIALS AND METHODS: 3D-printed zirconia brackets, commercially available polycrystalline alumina ceramic brackets (Clarity, 3 M St. Paul, MN) and 3D-printed customized polycrystalline alumina ceramic ones (LightForce™, Burlington, Massachusetts) were included in this study. Seven 3D printed zirconia brackets and equal number of ceramic ones from each manufacturer underwent metallographic grinding and polishing followed by Vickers indentation testing. Hardness (HV) and fracture toughness (K1c) were estimated by measuring impression average diagonal length and crack length, respectively. After descriptive statistics calculation, group differences were analysed with 1 Way ANOVA and Holm Sidak post hoc multiple comparison test at significance level α = .05. RESULTS: Statistically significant differences were found among the materials tested with respect to hardness and fracture toughness. The 3D-printed zirconia proved to be less hard (1261 ± 39 vs 2000 ± 49 vs 1840 ± 38) but more resistant to crack propagation (K1c = 6.62 ± 0.61 vs 5.30 ± 0.48 vs 4.44 ± 0.30 MPa m1/2 ) than the alumina brackets (Clarity and Light Force respectivelty). Significant differences were observed between the 3D printed and the commercially available polycrystalline alumina ceramic brackets but to a lesser extent. CONCLUSIONS: Under the limitations of this study, the 3D printed zirconia bracket tested is characterized by mechanical properties associated with advantageous orthodontic fixed appliances traits regarding clinically relevant parameters.


Assuntos
Óxido de Alumínio , Cerâmica , Dureza , Teste de Materiais , Óxido de Alumínio/química , Propriedades de Superfície
7.
Mar Drugs ; 21(11)2023 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-37999389

RESUMO

Periodontitis is a microbially-induced inflammation of the periodontium that is characterized by the destruction of the periodontal ligament (PDL) and alveolar bone and constitutes the principal cause of teeth loss in adults. Periodontal tissue regeneration can be achieved through guided tissue/bone regeneration (GTR/GBR) membranes that act as a physical barrier preventing epithelial infiltration and providing adequate time and space for PDL cells and osteoblasts to proliferate into the affected area. Electrospun nanofibrous scaffolds, simulating the natural architecture of the extracellular matrix (ECM), have attracted increasing attention in periodontal tissue engineering. Carrageenans are ideal candidates for the development of novel nanofibrous GTR/GBR membranes, since previous studies have highlighted the potential of carrageenans for bone regeneration by promoting the attachment and proliferation of osteoblasts. Herein, we report the development of bi- and tri-layer nanofibrous GTR/GBR membranes based on carrageenans and other biocompatible polymers for the regeneration of periodontal tissue. The fabricated membranes were morphologically characterized, and their thermal and mechanical properties were determined. Their periodontal tissue regeneration potential was investigated through the evaluation of cell attachment, biocompatibility, and osteogenic differentiation of human PDL cells seeded on the prepared membranes.


Assuntos
Nanofibras , Osteogênese , Adulto , Humanos , Carragenina/farmacologia , Sulfatos , Membranas Artificiais , Periodonto , Regeneração Óssea
8.
J Prosthet Dent ; 129(5): 811.e1-811.e9, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-36890002

RESUMO

STATEMENT OF PROBLEM: Evidence for the optimal spatial arrangement of magnetic attachments in implant-supported orbital prostheses is lacking. PURPOSE: The purpose of this in vitro study was to assess the effect of 6 different spatial arrangements on the retentive force of magnetic attachments following the in vitro simulation of clinical service by insertion-removal test cycles and the contribution of artificial aging to the morphological alterations induced on the magnetic surfaces. MATERIAL AND METHODS: Ni-Cu-Ni plated disk-shaped neodymium (Nd) magnetic units (d=5 mm, h=1.6 mm) were secured on leveled (50×50×5 mm, n=3) and angled (40×45×40 mm, interior angle=90 degrees, n=3) pairs of test panels in 6 different spatial arrangements: triangular_leveled (TL), triangular_angled (TA), square_leveled (SL), square_angled (SA), circular_leveled (CL), and circular_angled (CA) generating corresponding test assemblies (N=6). TL and TA arrangements included 3 magnetic units (3-magnet groups) and SL, SA, CL, and CA 4 (4-magnet groups). The retentive force (N) was measured at a mean crosshead speed of 10 mm/min (n=10). Each test assembly was subjected to insertion-removal test cycles with a 9-mm amplitude, ν=0.1 Hz, and n=10 consequent retentive force measurements at a crosshead speed of 10 mm/min at 540, 1080, 1620, and 2160 test cycles. Surface roughness alterations following the 2160 test cycles were measured by calculating the Sa, Sz, Sq, Sdr, Sc, and Sv parameters with an optical interferometric profiler with 5 new magnetic units used as a control group. Data were analyzed with 1-way ANOVA and Tukey HSD post hoc tests (α=.05). RESULTS: The 4-magnet groups had statistically significantly higher retentive force than the 3-magnet ones at baseline and following the 2160 test cycles (P<.05). In the 4-magnet group, the ranking at baseline was SA.05). CONCLUSIONS: Four magnetic attachments placed on an SL spatial arrangement resulted in the highest retention force but presented with the highest force reduction following the in vitro simulation of clinical service by insertion-removal test cycles.


Assuntos
Implantes Dentários , Retenção de Dentadura , Magnetismo , Imãs , Fenômenos Magnéticos , Análise do Estresse Dentário , Revestimento de Dentadura , Teste de Materiais , Prótese Dentária Fixada por Implante
9.
Eur J Orthod ; 45(3): 250-257, 2023 05 31.
Artigo em Inglês | MEDLINE | ID: mdl-36308302

RESUMO

OBJECTIVES: Interproximal enamel reduction (IPR) is routinely used in orthodontics to generate small to moderate amounts of space within the dental arch. Aim of this ex vivo study was to evaluate the effect of two different IPR systems on the enamel surface's waviness, roughness, and elemental composition after 6 months of intraoral exposure. MATERIALS AND METHODS: Fifteen orthodontic extraction patients were included in the present study. The 39 healthy premolars, which were scheduled to be extracted, were subjected to IPR at least 6 months before their extraction. IPR was performed on their mesial side with two different methods: (1) instrumented method with the Ortho-Strips system (on handpiece) and (2) manually with the Intensiv ProxoStrip (strips)-each with four different grits for contouring, finishing, and polishing. The distal side of each premolar served as its own internal control. Treated and untreated tooth surfaces were evaluated by optical profilometry, Raman, and scanning electron microscope/X-ray energy-dispersive (EDX) analyses. Data were analysed with descriptive statistics and generalized linear models at alpha = 5%. RESULTS: Both IPR methods significantly reduced the waviness of the enamel surface (P < 0.001), with manual IPR leading to smaller waviness reductions than the instrumented IPR (P ≤ 0.001). On the other side, both IPR methods led to a significant increase in enamel surface roughness (P < 0.001), with no significant differences between IPR methods. EDX and Raman analyses did not demonstrate any alterations on elemental composition of enamel after at least 6 months of intraoral exposure. CONCLUSIONS: Both stripping systems led to a flatter but rougher enamel surface. Further polishing is needed to restore the initial enamel smoothness. The elemental composition of the stripped enamel returns to the baseline level after 6 months of intraoral exposure.


Assuntos
Esmalte Dentário , Procedimentos de Cirurgia Plástica , Humanos , Dente Pré-Molar , Propriedades de Superfície
10.
J Orthod ; 50(4): 352-360, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-36573484

RESUMO

OBJECTIVE: To assess the surface roughness of in-house 3D-printed orthodontic aligners compared with Invisalign® appliances, both retrieved as well as in the 'as-received' control status. DESIGN: An in vitro study following intra-oral material aging. SETTING AND PARTICIPANTS: Twelve clinically used Invisalign® appliances and the same number of 3D-printed aligners, without involvement of attachments, were obtained from a respective number of patients. A similar number of 'as-received' aligners, of each material, were used as control (CON) groups. METHOD: Four groups of materials were examined: A = Invisalign® CON; B = Invisalign® used; C = 3D-printed CON; and D = 3D-printed used. Optical profilometry was employed to examine the following surface roughness parameters: amplitude parameters Sa, Sq and Sz and functional parameters Sc and Sv. Descriptive statistics and quantile regression modeling were conducted, and the level of statistical significance was set at α = 0.05. RESULTS: Intra-oral exposure of 3D-printed aligners was significantly associated with increase in all tested parameters (P < 0.001 at all occasions). Significant differences were detected in the retrieved 3D-printed aligners compared with Invisalign® retrieved, with the exception of Sz. The respective effect sizes (median differences) were as follows: Sa: 169 nm, 95% confidence interval [CI] = 89-248, P < 0.001; Sq: 315 nm, 95% CI = 152-477, P < 0.001; Sc: 233 nm3/nm2, 95% CI = 131-335, P < 0.001; and Sv: 43 nm3/nm2, 95% CI = 17-68, P = 0.002. CONCLUSION: Within the limitations of this study, we concluded that surface roughness differences existed between 3D-printed aligners and Invisalign® in the retrieved status, as well as between the control and retrieved 3D-printed groups.


Assuntos
Aparelhos Ortodônticos Removíveis , Humanos , Envelhecimento , Impressão Tridimensional
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