Osseointegration, antimicrobial capacity and cytotoxicity of implant materials coated with graphene compounds: A systematic review.

The use of graphecs excellent mechanical properties. However, it is necessary to evaluate the biological effects of this material. This systematic review aimed to observe and understand through studies the current state of the art regarding osseointegration, antimicrobial capacity, and the cytotoxicity of graphene coating applied to the surface of dental implant materials. Searches in PubMed, Embase, Science Direct, Web of Science, and Google Scholar databases were conducted between June and July 2021 and updated in May 2022 using the keywords: graphene, graphene oxide, dental implants, zirconium, titanium, peek, aluminum, disilicate, methyl-methacrylate, cytotoxicity, osseointegration, and bone regeneration. The criteria included in vivo and in vitro studies that evaluated antimicrobial capacity and/or osseointegration and/or cytotoxicity of dental implant materials coated with graphene compounds. The risk of bias for in vitro studies was assessed by the JBI tool, and for in vivo studies, Syrcle's risk of bias tool for animal studies was used. The database search resulted in 176 articles. Of the 18 articles selected for full reading, 16 remained in this systematic review. The use of graphene compounds as coatings on the surface of implant materials is promising because it promotes osseointegration and has antimicrobial capacity. However, further studies are needed to ensure its cytotoxic potential.

In situ evaluation of microbial profile formed on Ti-6Al-4V additive manufacturing disks: 16S rRNA sequencing.

STATEMENT OF PROBLEM: Dental implants obtained by additive manufacturing may present changes in the microbiome formed. However, studies profiling the microbial communities formed on Ti-6Al-4V are lacking. PURPOSE: The purpose of this in situ study was to characterize the profile of the microbial communities formed on Ti-6Al-4V disks produced by additive manufacturing and machining. MATERIAL AND METHODS: Titanium disks produced by additive manufacturing (AMD) and machining (UD) were housed in the buccal region of removable intraoral devices. These devices containing both disks were used by eight participants for 96 hours. After every 24 hours of intraoral exposure, the biofilm that had formed on the disks was collected. The 16S rRNA genes from each specimen were amplified and sequenced with the Miseq Illumina instrument and analyzed. Total microbial quantification was evaluated by analysis of variance-type statistics using the nparLD package. The Wilcoxon test was used to evaluate alpha diversity (α=.05). RESULTS: A difference was found in the microbial communities formed on additively manufactured and machined disks, with a reduction in operational taxonomic units (OTUs) for the AMD group compared with the UD group. Firmicutes and Proteobacteria were the most abundant phyla. Of the 1256 genera sequenced, Streptococcus predominated on both disks. CONCLUSIONS: The microbiome of the biofilm formed on the Ti-6Al-4V disks was significantly influenced by the fabrication method. The AMD disks showed lower total microbial counts than the UD disks.

Influence of Er:YAG laser irradiation on surface properties of Ti-6Al-4V machined and hydroxyapatite coated.

Surface treatment by laser irradiation can change the topography of titanium; however, little is known about the changes it causes when applied to other coatings. This study aimed to evaluate the influence of Er:YAG laser irradiation on the surface properties of titanium-aluminum-vanadium (Ti-6Al-4V) discs. Four Ti-6Al-4V surfaces were evaluated (n = 10): CON-control, machined without surface treatment; LT-machined + laser treatment; HA-hydroxyapatite coating; and LT-HA-hydroxyapatite coating + laser treatment. For the laser treatment, an Er:YAG laser with a wavelength of 2940 nm, a frequency of 10 Hz, and an energy density of 12.8 J/cm2 was used. The morphology of the coating was investigated by scanning electron microscopy and the surface composition by energy-dispersive X-ray spectroscopy. The influence of laser irradiation treatment on roughness and wettability was also evaluated. The Er:YAG laser promoted a significant reduction in the roughness Sa (p < 0.05) and in the contact angle (p = 0.002) of the LT surface compared to the CON surface. On the LT-HA surface, a significant decrease in roughness was observed only for the Rz parameter (p = 0.015) and an increase in the contact angle (p < 0.001) compared to the HA surface. The use of the Er:YAG laser with the evaluated parameters decreased the surface roughness and improved the wetting capacity of machined without surface treatment. In the group with hydroxyapatite coating, the laser influenced the surface roughness only for the parameter Rz and reduced their wetting capacity.

Relationship between dental implant macro-design and osseointegration: a systematic review.

PURPOSE: This systematic review aimed to determine whether differences in the macro-geometry of titanium implants promote changes in osseointegration. MATERIAL AND METHOD: SCOPUS, PubMed/Medline, Web of Science, and EMBASE databases were searched in June 2021. In addition, it was performed a manual search of the reference lists of the included articles. Eligibility criteria were in vivo studies that addressed the effect of titanium implant macro-geometry on osseointegration, studies that evaluated periodontally healthy models, and papers indexed in Journal Citation Reports. RESULTS: The database search resulted in 1037 articles. Of the 19 articles selected for full reading, 16 remained in this systematic review. These had a high heterogeneity making it hard to perform statistical analysis of the data, so a descriptive analysis was performed. CONCLUSIONS: Based on the studies included in this systematic review, implant macro-geometry provides influences on osseointegration. In this sense, the various isolated characteristics (thread type, thread pitch, thread depth, face angle) should be studied so that the implant geometry can balance the compressive stress and tensile stress and produce a minimum shear force.

Incorporation of a ß-AgVO3 Semiconductor in Resin Cement: Evaluation of Mechanical Properties and Antibacterial Efficacy.

PURPOSE: This in vitro study aimed to investigate the effect of incorporating the semiconductor nanostructured silver vanadate decorated with silver nanoparticles (ß-AgVO3) in a dual-cure resin cement on the degree of conversion (DC), microhardness, roughness, color, adhesion properties before and after artificial aging, and antimicrobial efficacy. MATERIAL AND METHODS: Three test groups were established: control (without ß-AgVO3), with the incorporation of 2.5% and 5% (by weight) of ß-AgVO3 in dual-cure resin cement (Allcem, FGM). The degree of conversion was measured using Fourier transform infrared spectroscopy (FTIR). To evaluate roughness (n = 10), microhardness (n = 10), color (n = 10), and to perform agar disk diffusion (n = 8), disks of 6-mm diameter and 2-mm height were manufactured using the same concentrations. For the color and shear bond strength test (n = 6), orthodontic brackets (Morelli) were used, which were cemented to natural human enamel and evaluated before and after artificial aging via thermocycling at 5°C and 55°C for 1000 cycles. For color measurements, a portable spectrocolorimeter and the CIE-Lab method were used. Data were analyzed using Student's t-test, ANOVA, and Tukey's multiple comparisons with significance set at α = 0.05. RESULTS: Semiconductor incorporation did not influence the cements's DC. The incorporation of 2.5% and 5% of ß-AgVO3 resulted in a significant increase in Knoop microhardness and surface roughness. Significant changes were observed in the color of the specimens when the semiconductor was incorporated. Adhesion after aging remained within the clinically recommended values in all groups, and antimicrobial activity was observed against Staphylococcus aureus, Streptococcus mutans, and Enterococcus faecalis at both concentrations tested. CONCLUSION: It is suggested to incorporate the semiconductor ß-AgVO3 in the dual-cure resin cement at both concentrations. Moreover, the physical-mechanical properties remained satisfactory for the proposed application.

Protein absorption on titanium surfaces treated with a high-power laser: A systematic review.

STATEMENT OF PROBLEM: The surface of titanium dental implants treated with a high-power laser has been reported to favor osseointegration, mainly by altering protein uptake. Despite the large number of articles that address the topic, the heterogeneity of methodologies and results makes an understanding of the treatment's benefits difficult, and a systematic review is needed. PURPOSE: The purpose of this systematic review was to further the knowledge on protein uptake on titanium surfaces that have undergone treatment with a high-power laser. MATERIAL AND METHODS: This review followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and was registered with the Open Science Framework (OSF) (osf.io/gcbna). Searches were performed in PubMed, Scopus, Web of Science, Embase, and Google Scholar databases. The articles were selected in 2 steps by 2 independent reviewers according to the previously selected eligibility criteria. The risk of bias was analyzed by using the Joanna Briggs Institute (JBI)-adapted quasi-experimental study evaluation tool. RESULTS: The studies addressed have shown that applying a high-power laser to the implant surface, depending on its settings, generates topographical changes that can optimize the protein absorption process and thus accelerate the other biological processes. CONCLUSIONS: The studies identified in this systematic review showed that surface treatment with a high-power laser represents a promising technique with a positive influence on protein uptake and osseointegration.

Effect of surface properties of ceramic materials on bacterial adhesion: A systematic review.

PURPOSE: The objective of this systematic review was to describe studies that report on whether surface characteristics such as electrostatic charge, surface free energy, and surface topography promote influence on bacterial adhesion on ceramic surfaces. MATERIAL AND METHOD: Searches in the SCOPUS, PubMed/Medline, Web of Science, EMBASE, and Google Scholar databases were performed between December 2020 and January 2021 and updated in March 2021. In addition, a manual search of reference lists from relevant retrieved articles was performed. The criteria included: studies that evaluated ceramic surfaces, which described factors such as surface free energy, electrostatic charges, roughness, zeta potential, and their relationship with bacteria. RESULTS: Database search resulted in 348 papers. Of the 24 studies selected for full reading, 17 articles remained in this systematic review. Another five studies were found in references of articles included, totaling 22 studies. These had a high heterogeneity making it difficult to perform statistical analysis, so a descriptive analysis was performed. CONCLUSIONS: For dental ceramics, not enough results were found to demonstrate the influence of the electrostatic condition, and its relationship with bacterial adhesion. However, studies of this review show that there is a correlation between bacterial adhesion, surface free energy, and topography. CLINICAL SIGNIFICANCE: The knowledge of ceramics with repulsive physical-chemical interactions would allow an environment suggestive of non-adhesion of pathogenic biofilm.

Bacterial adhesion to biomaterials: What regulates this attachment? A review.

Bacterial attachment to biomaterials is of great interest to the medical and dental field due to its impact on dental implants, dental prostheses, and others, leading to the need to introduce methods for biofilm control and mitigation of infections. Biofilm adhesion is a multifactorial process and involves characteristics relevant to the bacterial cell as well as biological, chemical, and physical properties relative to the surface of biomaterials. Bacteria encountered different environmental conditions during their growth and developed interspecies communication strategies, as well as various mechanisms to detect the environment and facilitate survival, such as chemical sensors or physical detection mechanisms. However, the factors that govern microbial attachment to surfaces are not yet fully understood. In order to understand how bacteria interact with surfaces, as well as to characterize the physical-chemical properties of bacteria adhesins, and to determine their interrelation with the adhesion to the substrate, in recent years new techniques of atomic force microscopy (AFM) have been developed and helped by providing quantitative results. Thus, the purpose of this review is to gather current studies about the factors that regulate microbial adhesion to surfaces in order to offer a guide to studies to obtain technologies that provide an antimicrobial surface.

Zircônia na odontologia: mini-revisão / Zirconia in Dentistry: mini-review

Objetivo: O objetivo deste estudo é fornecer ao cirurgião-dentista conhecimento sobre aspectos gerais da zircônia e abordar a introdução das diferentes gerações. Materiais e métodos: Foi realizada uma pesquisa eletrônica da literatura atual em inglês, incluindo artigos científicos publicados até 2019. Resultados: De acordo com os artigos selecionados, diferenças importantes foram encontradas em relação as novas composições da zircônia, sua microestrutura, diferenças no conteúdo da fase cúbica, e de ítria na fase tetragonal, levando a diferentes propriedades ópticas, mecânicas e de resistência ao envelhecimento. Conclusão: A zircônia é o material mais resistente disponível entre as cerâmicas, com diferenças mecânicas e ópticas entre os materiais disponíveis. A introdução das coroas monolíticas resolveu o problema de lascamento da porcelana de cobertura, mas foram necessárias modificações estruturais para fornecer adequada translucidez.

Purpose: This study aims to provide knowledge to clinicians about general aspects of zirconia and to approach the introduction of different zirconia generations. Methods:An electronic search of the English current literature was conducted including scientific articles published up to 2019. Results: According to the selected articles, important differences were found in terms of the novel compositions of zirconia, microstructures among the materials, differences in cubic phase content and yttria in the tetragonal phase, leading to different optical, mechanical and aging resistance properties. Conclusion: Zirconia is the most resistant material available among ceramics with mechanical and optical differences on available materials. The introduction of the monolithic crowns solving the veneering delamination but struc-tural modifications were necessary to provide adequate translucency

Influence of the electrostatic condition of the titanium surface on bacterial adhesion: A systematic review.

STATEMENT OF PROBLEM: Infection of a dental implant is undesirable and decreases the success rate of the dental prosthesis; however, systematic reviews on the issue are lacking. PURPOSE: The purpose of this systematic review was to evaluate studies that dealt with inherent factors or those applied to the titanium surface or alloys to provide an antimicrobial action. MATERIAL AND METHODS: SCOPUS, PubMed/Medline, Web of Science, EMBASE, and Science Direct databases were searched and manual searches made between June and July 2019 using the keywords "titanium," "surface," "implants," "photoelectron spectroscopy," and "fourier transform infrared spectroscopy." The criteria included in vitro studies evaluating the titanium surface and describing hydrophobicity, surface crystalline phase, nanotopography, surface charges, and their relationship with bacteria and/or osseointegration. RESULTS: A comprehensive search identified 767 articles that were selected by the title and/or abstract as per the inclusion criteria. Of the 58 studies selected for full reading, 7 were used for this systematic review. Another 6 studies were added by further research, resulting in 13 articles, all in vitro studies. As the selected studies had a high heterogeneity that precluded any statistical analysis of the data, a descriptive analysis of these topics was performed: hydrophilicity, surface crystalline phase, nanotopography, and surface charges. CONCLUSIONS: The articles analyzed in this systematic review suggest that hydrophilicity, crystalline phase, surface topography, and surface titanium charge, when altered, may provide an antimicrobial surface. However, the strategy used resulted in heterogeneous articles, making it impossible to demonstrate the unique effect of the electrostatic surface of titanium or titanium alloy used for implants and its effect on bacterial control.

Analysis of the mechanical and physicochemical properties of Ti-6Al-4 V discs obtained by selective laser melting and subtractive manufacturing method.

The surface properties of titanium and its alloys are commonly modified by different techniques, including additive manufacturing (AM), to improve the osseointegration of dental implants. The aim of this study was to evaluate and compare the wettability, topography, chemistry, and structure of titanium-aluminum-vanadium (Ti-6Al-4 V) discs fabricated by selective laser melting (SLM) and subtractive manufacturing (conventional machining). Three different groups were evaluated: selective laser melting (SLM); conventional machining with H3 PO4 + NaOH surface treatment (CM + ST); and conventional machining without surface treatment (CM), including analysis of wettability and roughness, morphological and chemical analyses by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), and structural characterization analysis by computed tomography (micro-CT), and X-ray diffraction (XRD). The results showed that SLM surface had higher roughness (9.09 ± 1.94 Ra; 51.93 ± 11.59 Rz; 11.03 ± 1.95 Sa) and lower wettability (103.23° ± 13) than CM (0.06 ± 0.01 Ra; 0.42 ± 0.078 Rz; 0.07 ± 0.01 Sa) (76.95° ± 4.18) and CM + ST (0.17 ± 0.38 Ra; 0.88 ± 0.15 Rz; 0.18 ± 0.04 Sa) (18.55° ± 6.47) (p < 0.05). SEM images also proved the higher roughness of SLM surface, and CM + ST discs showed a topography resembling a sponge, characteristic of the nanometric treatment applied. EDX and XRD found no differences between the different surfaces, and micro-CT demonstrated the solid characteristic of the SLM disc. Compared with conventional machining, the SLM technique resulted in higher roughness and lower wettability. Meanwhile, the chemical properties and structure of the titanium alloy was not altered by the technique.

Influence of AgVO3 incorporation on antimicrobial properties, hardness, roughness and adhesion of a soft denture liner.

The objective of this in vitro study was to investigate the effect of nanostructured silver vanadate decorated with silver nanoparticles (AgVO3) on antimicrobial activity, hardness, roughness, and adhesion of a soft denture liner. The antimicrobial efficacy of the Trusoft (Boswoth) liner incorporated with different concentrations of AgVO3 against Enterococcus faecalis, Pseudomonas aeruginosa, Candida albicans, and Staphyloccocus aureus (n = 5) was evaluated by the agar diffusion method. Roughness, hardness, and adhesion properties were also evaluated. The data were analyzed by analysis of variance (ANOVA) and Tukey's multiple comparison test with significance at the p < 0.05 level. At concentrations of 1 and 2.5%, AgVO3 incorporation was effective only against E. faecalis, and at 5 and 10%, against E. faecalis, P. aeruginosa, and C. albicans. None of the concentrations was effective against S. aureus. A decrease in hardness was found for the 1, 2.5, and 10% AgVO3 concentrations (p < 0.001) and at 5%, hardness was not affected. None of the concentrations affected the roughness of the material. A significant increase in tensile values was observed between the liner and heat-curing acrylic resin for 2.5% (p < 0.001) and 10% (p = 0.042) concentrations. AgVO3 incorporation to a soft denture liner promoted antimicrobial activity against E. faecalis, P. aeruginosa, and C. albicans without affecting roughness, maintaining the hardness properties recommended for soft and extra soft liners, and improving the adhesion between the liner and the acrylic resin used for dentures.

Development of an Impression Material with Antimicrobial Properties for Dental Application.

PURPOSE: To evaluate the antimicrobial activity and physico-mechanical properties of an irreversible hydrocolloid in which nanostructured silver vanadate decorated with silver nanoparticles (AgVO3 ) was added at various concentrations (0% - control, 2.5%, 5%, and 10% by weight). MATERIALS AND METHODS: The agar diffusion method (n = 10) was used to evaluate the inhibitory effect on the following species: Streptococcus mutans, Staphyloccocus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. The gelation time, flow capacity and plastic deformation were verified (n = 10). The data were analyzed using the Kruskal-Wallis test followed by the Dunn post-test, or via one-way ANOVA with multiple comparisons with a Bonferroni adjustment depending on the distribution (α = 0.05). RESULTS: All percentages of the nanomaterial were able to promote the antimicrobial activity of a hydrocolloid, with the formation of an inhibition zone (p < 0.05). In general, there was a dose-dependent effect on antimicrobial activity: higher concentrations of the nanomaterial promoted greater action except in the cases of P. aeruginosa (p < 0.001; F = 51.74) and S. aureus (p < 0.001), where the highest inhibition was for the 2.5% group. No difference was found in the gelation time when the control was compared with the groups with AgVO3 (p > 0.05). The difference was between the 5% and 10% groups (p = 0.007), and the latter promoted an increase in time. The flow capacity of the hydrocolloid with 5% of AgVO3 was significantly lower when compared with the control (p = 0.034). The AgVO3 influenced the plastic deformation (p < 0.001) in such a way that concentrations of 5% (p = 0.010) and 10% (p < 0.001) promoted an increase in this property when compared with the control. CONCLUSIONS: AgVO3 can be incorporated into an irreversible hydrocolloid as an antimicrobial agent without promoting adverse effects on physical-mechanical properties when used in concentrations of 2.5%.

Denture Liners: A Systematic Review Relative to Adhesion and Mechanical Properties.

PURPOSE: The objective of this systematic review is to compare results concerning the properties of adhesion, roughness, and hardness of dental liners obtained in the last ten years. METHODS: Searches on the databases LILACS, PubMed/Medline, Web of Science, and Cochrane Database of Systematic Reviews were supplemented with manual searches conducted between February and April of 2018. The inclusion criteria included experimental in vitro and in vivo, clinical, and laboratory studies on resilient and/or hard liners, assessment of hardness, roughness, and/or adhesion to the denture base, and physical/mechanical changes resulting from the disinfection process and changes in liners' composition or application. RESULTS: A total of 406 articles were identified and, from those, 44 are discussed. Twenty-four studies examined the bond strength, 13 surface roughness, and 19 the hardness. Of these 44 studies, 12 evaluated more than one property. Different substances were used in the attempt to improve adhesion. Considering roughness and hardness, the benefits of sealants have been tested, and the changes resulting from antimicrobial agents' incorporation have been assessed. CONCLUSION: Adhesion to the prosthesis base is improved with surface treatments. Rough surfaces and changes in hardness compromise the material's serviceability.

Reverse torque evaluation in indexed and nonindexed abutments of Morse Taper implants in a mechanical fatigue test.

BACKGROUND: This experimental study assessed reverse torque of indexed and nonindexed (NI) abutments in Morse Taper (MT) implants in a mechanical fatigue test. MATERIALS AND METHODS: In this experimental study It was used 37 implants MT and over them installed Pilar Flex abutments (4.8 mm × 6 mm × 1.5 mm). The groups were as follows: Group A used 19 MT implants with a NI Pilar Flex abutment loaded with 32 N/cm and Group B used 18 MT implants with an indexed (IN) Pilar Flex abutment loaded with 20 N/cm. The abutments were tested according to ISO standard 14801/2007. The specimens were installed at 30° from the axial axis and underwent a 133 N load, 4 Hz frequency, and 1,000,000 cycles. Once the test was completed, the reverse torque was provided by an electronic torque meter. Data were submitted to statistical analysis using the t-test for independent samples and paired t-test. The significance level was considered P < 0.05. RESULTS: Results obtained showed that the indexed Pilar Flex abutment had a percentage of torque loss from the initial torque of 49% and the NI Pilar Flex abutment lost 14%. Paired Student's t-tests revealed that for both NI (P < 0.001) and indexed (P < 0.001) abutments, the counter torque values were significantly lower than those applied at the initial torque. CONCLUSION: According on the methodology used, the NI Pilar Flex abutment was more effective regarding the reverse torque in single-unit implant prostheses versus the indexed Pilar Flex abutment. A greater loosening in the indexed Pilar Flex abutment retaining screw was noted in the reverse torque test, and the Pilar Flex abutment failed to show good outcomes related to the cold welding effect.

Biomechanical Behavior of an Implant System Using Polyether Ether Ketone Bar: Finite Element Analysis.

AIM AND OBJECTIVES: This study assessed, through finite element analysis, the biomechanical behavior of an implant system using the All-on-Four® technique with nickel-chromium (M1) and polyether ether ketone (PEEK) bars (M2). MATERIALS AND METHODS: Implants and components were represented in three-dimensional (3D) geometric models and submitted to three types of load: axial, oblique, and load on all teeth. The 3D models were exported to a computer-aided design-like software such as Solidworks 2016 (Dassault Systemes, Solidworks Corps, USA) for editing and Nonuniform Rational Basis Splines parametrization. RESULTS: Data were analyzed according to system's areas of action: peri-implant bone, implant, intermediates, intermediates' screws, prostheses' screws, and bars. Largest peak stress was shown in M2. CONCLUSION: PEEK is a promising material for use in dentistry; however, further studies are necessary to evaluate its performance.

Influência dos diferentes tempos de vazamento na variação dimensional de modelos de gesso / Influence of different leakage times in dimensional variation of plaster models

A variedade de materiais de moldagem, bem como o tempo decorrido entre o ato da moldagem e o vazamento do molde podem ser causas de alterações dimensionais nos modelos de trabalho e também falhas na fidelidade de cópia dos preparos protéticos. Objetivo: avaliar in vitro a variação dimensional de modelos de gesso vazados em diferentes tempos, produzidos por 4 materiais de moldagem. Materiais e métodos: os materiais de moldagem foram divididos em 4 grupos: (A) experimentais, sendo A1 e A2 Silicones de Condensação, A3 e A4 Silicones de Adição, os quais reproduziram uma matriz multifuncional. foram obtidos 48 modelos (n=192) pela técnica de moldagem única e vazados nos seguintes tempos 1, 4, 24 e 72 horas com gesso tipo IV. As medidas dos modelos de gesso foram obtidas utilizando-se scanner digital (3Shape, Compass, Brasil). Resultados: Nenhum dos materiais utilizados apresentou variação dimensional estatisticamente significativa (p>0,005) em quaisquer um dos tempos de vazamento. Conclusão: De acordo com a metodologia empregada, o tempo de vazamento não teve influência na variação dimensional observada, nem nos Silicones de Condensação, nem nos Silicones de Adição.

The variety of materials that can be used for dental impression, as well as the time spent between the dental impressions molding and pouring may be responsible for defects such as dimensional discrepancies observed on master casts and also lack of fidelity on the prosthetic work copies. Aim: Evaluate, in vitro, dimensional variation of cast models at different pouring times, considering (4) different impression materials. Materials and methods: The impression materials were divided into 4 groups; (A) experimental, with A1 and A2 condensation silicones, A3 and A4 addition silicones which reproduced a multifunctional matrix. forty-eight models were obtained (n=192) by one step impression technique and poured at the following times 1, 4, 24 and 72 hours with plaster type IV. The plaster models measurements were obtained using digital scanner (3Shape, Compass, Belo horizonte, Minas Gerais, Brazil). Conclusion: According to the used methodology, the molding OU pouring time did not have influence in the dimensional variation observed, neither on condensation silicones nor in addition silicones.

Avaliação da resistência flexural em diferentes métodos de soldagem / Evaluation of flexural resistance in different welding methods

O objetivo do presente estudo foi avaliar três diferentes tipos de soldagem: Chama Direta a maçarico (convencional\brasagem), Solda Mista representada por fixação de dois pontos (Solda Elétrica Fixator - Kernit, Brasil), e completada com solda convencional, e o método de Solda a Laser (Soldadora Desktop - Sisma LM 500, Itália). Dois implantes plataforma Bränemark 4.1 mm (Neodent, Curitiba/Brasil) foram fixados em uma matriz de alumínio para simular uma ponte fixa implanto-suportada de três elementos. Os espécimes foram obtidos a partir de um bloco de cera CAD-CAM (Ceramill-Amammgirrbarch). Trinta e duas UCLAs hexágono externo foram fresadas e posteriormente unidas a uma barra pré-fabricada em cera com 2,5mm. Os corpos de prova foram fundidos em liga de cobalto-cromo simulando uma prótese fixa de três elementos. Esses espécimes foram divididos aleatoriamente e separados em três grupos (n=6): grupo A (solda chama direta), grupo B (solda mista), grupo C (solda laser). Os espécimes foram seccionados ao meio e unidos com resina acrílica para simular uma soldagem em prótese fixa. Os corpos foram soldados e tratados de acordo com a proposição. Após a soldagem os corpos de prova foram usinados e levados ao teste de flexão na técnica de três pontos. Os dados foram submetidos aos testes estatísticos de Tukey. Os cálculos estatísticos foram conduzidos adotando-se o nível de significância de 5% (α = 0,05). Houve diferença estatisticamente significativa entre os grupos soldados. Os resultados demonstraram valores mais elevados nos grupos A e B, solda convencional e solda mista, e menor valor no grupo C, solda a laser. No entanto, considerando a metodologia aplicada, a solda a laser mostrou uma menor resistência flexural comparada à soldagem convencional e mista, e a fixação prévia de solda elétrica com complemento de solda convencional (solda mista) não alterou a resistência flexural, produzindo resultado semelhante à solda convencional

The objective of this study was to evaluate three different types of welding, blowtorch; (conventional/brazing), welder Joint; represented by securing two points (Arc Welding Fixator - Kernit, Brazil), and supplemented with conventional welding), and Laser welding method (welder Desktop - Sisma LM 500, Italy). Two implants Bränemark 4.1 mm platform (Neodent, Curitiba/Brazil) were fixed in an aluminum matrix. Specimens were obtained from a CAD-CAM wax block (Ceramill - Amammgirrbarch) were milled 32 UCLAs (external hexagon, Bränemark platform), and subsequently joined to a prefabricated bar also wax 2.5 mm, the specimens were casted in cobalt-chromium alloy. These specimens were randomly divided and separated into 3 groups: group A (welding direct flame), Group B (mixed welding), C (laser welding), with 6 samples for each group. The specimens of each group were cut in half to simulate a fixed prosthesis in welding, and put together with acrylic resin. The bodies were welded and treated according to the statement. After the specimens were welded, they were manually grinded and submitted to the 3 points bending test technique. Data were subjected to statistical tests of Tukey. Statistical calculations were performed adopting the significance level of 5% (α = 0.05), using SPSS 20 (SPSS Inc., Chicago, IL, USA). There were differences between the soldered groups. The data showed the highest values obtained in groups A and B, conventional welding and soldering joint, and lower in group C, the laser welding. However, within the applied methodology, the laser welding showed a lower flexural strength compared to conventional and mixed welding, and that the advance fixing of electric welding, conventional welding complement (mixed welding), does not change its flexural strength, producing results similar to conventional welding

Analysis of the Mechanical Behavior and Surface Rugosity of Different Dental Die Materials.

AIM: This work evaluated the mechanical and surface behavior of different die materials. The studied materials are polyurethane resin Exakto-Form (Bredent), Gypsum type IV, Fuji Rock EP (Gc), and Durone (Dentsply). MATERIALS AND METHODS: Two metallic matrices molded in polyvinyl siloxane provided 30 cylindrical test specimens for the diametral compression test and 30 hemispherical test specimens for the surface rugosity test. The cylindrical test specimens were submitted to tests of diametral compression strength using a DL2000 universal assay machine, with a load cell of 2000 Kgf and constant speed of 1 mm/min connected to the software. Kruskal-Wallis and Dunn's nonparametric tests were used to analyze the results. The hemispheres were submitted to the surface rugosity assay using a SJ201-P rugosimeter with a sensitivity of 300 µm, speed of 0.5 mm/s, and cut-off of 0.8 mm, and the readings were taken on the convex surface of the test specimens and metallic matrix. Results were analyzed using with Fisher's least significant differences test (LSD) and Dunnett's test. RESULTS: Kruskal-Wallis test showed significant difference between die materials for diametral compression strength (P = 0.002). Dunn's test showed significantly higher values for modified polyurethane resin (Exakto-Form). The gypsum type IV, which did not significantly differ regarding diametral compression strength, showed 34.0% (Durone) and 42.7% (Fuji Rock) lower values in comparison to Exakto-Form. CONCLUSION: Within the parameters adopted in this study, it is possible to conclude that Exakto-Form polyurethane resin showed higher resistance to compression and was closer to the metallic matrix rugosity, and, along with the gypsum type IV Durone, showed better reproducibility of details relative to the Fuji Rock.

Efeito de primer para zircônia sobre a resistência ao cisalhamento entre um cimento resinoso e a cerâmica de óxido de zircônio / Effect of primer on the bond strength between resin cement and zirconia

O objetivo deste estudo foi avaliar as influências acarretadas pelo tratamento das superfícies das zircônias com primer apropriado na resistência de união entre cimento resinoso e uma cerâmica de Zircônia. foram utilizados 20 corpos de prova em Zircônia VIPI BLOCK ZIRCONN (VIPI, São Paulo, Brasil) divididos em 2 grupos: Grupo 1 ­ tratamento de superfície da zircônia apenas com jateamento de óxido de alumínio e cimento resinoso PanaviaTF 2.0 (Kuraray, Kurashiki, Japão); e Grupo 2 ­ além do jateamento usou-se o primer Ceramic Primer (3M, São Paulo, Brasil). Os espécimes cerâmicos receberam o cimento manipulado na proporção de 1:1 e foram estocados em água destilada a 37ºC por 24 horas antes e após a termociclagem. O ensaio de cisalhamento foi realizado em máquina de ensaios EMIC DL2000 (EMIC, São Paulo, Brasil), os valores de resistência de união foram apresentados em Mpa e analisados através de Análise de Variância (ANOVA) e teste t Student para amostras independentes. Os valores resistência ao cisalhamento entre cimentos e cerâmica à base de zircônia utilizando os primers mencionados não foram estatisticamente diferentes, isto é, nenhuma diferença significativa foi encontrada entre os grupos G1 (8,70 ± 6,31) e G2 (8,18 ± 3,75). Os testes realizados com o primer não mostraram aumento considerável na resistência de união ao cisalhamento entre cimentos e cerâmica à base de zircônia.

The aim of this study was to evaluate the influence of the use of primer to treat zirconia surfaces on the bond strength between resin cement and zirconia ceramics. The 20 specimens were divided into 2 groups: group 1 ­ zirconia surface treatment with sandblasting with aluminum oxide and Panavia T f 2.0 (Kuraray); Group 2 ­ in addition to the sandblasting Ceramic Primer (3M) was used. Each specimen of the ceramic material received manipulated cement in the proportion 1:1. The specimens were stored in distilled water at 37 ° C for 24 hours before and after thermocycling. Shear test was performed in testing EMIC DL2000 (EMIC, São Paulo, Brazil) and the values of bond strength in MPa were analyzed using Analysis of Variance (ANOVA) and Student t test for independent samples machine. There was no significant difference between the values for shear strength between both studied groups: G1 (8.70 ± 6 groups, 31) and G2 (8.18 ± 3.75). The tests performed with the primer used in this study showed no significant increase on shear bond strength between cement and ceramics based on zirconia.