In vitro cytotoxicity of resin cement and its influence on the expression of antioxidant genes / Avaliação in vitro da toxicidade de cimentos resinosos e sua influência na expressão de genes antioxidantes em fibroblastos humanos

ABSTRACT Aim: This study evaluated cytotoxicity and antioxidant gene expression of resin cements on human gingival fibroblasts (hGF). Materials and Method: RelyX Ultimate™(RXU), Variolink™II(VLII), and RelyXU200™(RXU200) resin cements were incubated with culture medium for 24 h to obtain eluates. Then, the eluates were applied over hGF to assess cell viability at 24 h, 48 h, and 72 h and antioxidant gene expression at 24 h. hGF cultures non-exposed to the eluates were used as Control. Data were submitted to ANOVA and Bonferroni tests (α≤0.05). Results: RXU and RXU200 reduced the number of viable cells in 24 h. Longer exposure to cement extracts caused cell death. Gene expression showed peroxiredoxin 1 (PRDX1) induction by all resin cement types, and superoxide dismutase 1 (SOD1) induction by RXU200 and VLII. Moreover, RXU200 induced not only PRDX1 and SOD1, but also glutathione peroxidase 1 (GPX1), catalase (CAT), and glutathione synthetase (GSS). Conclusions: All resin cements showed toxicity, and induced antioxidant genes in hGF. Antioxidant gene induction is at least partly associated with cytotoxicity of tested cements to oxidative stress experience.

RESUMO Objetivo: O objetivo deste estudo foi avaliar a toxicidade dos cimentos resinosos Rely X Ultimate 2, Rely X U200 e Variolink II, bem como sua influência na expressão de genes antioxidantes em fibroblastos gengivais humanos. Materiais e Método: Corpos de prova de cada cimento foram colocados em meio de cultura por 24 h e os extratos correspondentes foram aplicados aos fibroblastos. A viabilidade celular foi avaliada após 24, 48 e 72 h de exposição pelo ensaio de exclusão do azul de tripano e MTT. A expressão gênica foi avaliada por PCR quantitativo após 24 h de exposição aos extratos. Estes parâmetros foram comparados aos das células não expostas aos cimentos. Os dados foram submetidos ao teste ANOVA, seguido pelo pós-teste de Bonferroni (a≤0.05). Resultados: Os resultados demonstraram que todos os cimentos promoveram redução do número de células viáveis e da atividade mitocondrial nos períodos de 48 e de 72 h (p < 0,01), sendo que o Variolink II apresentou o menor efeito e os cimentos Rely X Ultimate e Rely X U200 promoveram similarmente os maiores efeitos. A análise de expressão gênica evidenciou influência significativa em todos os cimentos avaliados sobre os níveis de transcritos de PRDX1, SOD1, GPX1 e GSS (p> 0,05), com um aumento considerável no Rely X U200. Conclusão: A indução de genes antioxidantes está, pelo menos em parte, associada à citotoxicidade dos cimentos testados para a experiência de estresse oxidativo.

Resistencia de unión al cizallamiento de diferentes agentes de fijación a aleaciones metálicas odontológicas / Shear bond strength of different bonding agents to dental metal alloys

Introducción: La fijación de las restauraciones indirectas es uno de los pasos más importantes, para conseguir una adecuada retención y sellado de la interfase entre el material restaurador y el diente. Objetivo: Evaluar la resistencia de unión al cizallamiento de diferentes agentes de fijación a dos aleaciones metálicas utilizadas en odontología. Métodos: Estudio experimental in vitro. Cien especímenes de aleaciones de metales base, 50 de níquel-cromo y 50 de níquel-cromo-titanio fueron preparados y divididos de manera aleatoria en 5 grupos. Esta división se realizó acorde con el agente de fijación utilizado: sistema autograbante de dos pasos (Clearfil SE Bond; CSB), sistema adhesivo universal (Single Bond Universal; SBU), cemento resinoso autoadhesivo (Maxcem Elite; ME), ionómero de vidrio (IV) y fosfato de zinc (ZnPO). Posteriormente a la aplicación de cada agente de fijación, los especímenes tratados fueron almacenados en agua destilada por 24 h a 37 ºC y sometidos a un ensayo de resistencia de unión al cizallamiento. Resultados: La resistencia de unión al cizallamiento fue influenciada significativamente por el tipo de agente de fijación (p = 0,002) y el tipo de aleación utilizada (p < 0,001). La resistencia de unión al cizallamiento fue mayor, al utilizar el sistema Clearfil SE Bond, seguida de Single Bond Universal; las diferencias entre Maxcem Elite y el Fosfato de zinc no fueron significativas. Finalmente, el IV no mostró adhesión a ninguna de las aleaciones metálicas utilizadas. Conclusiones: El uso de Clearfil SE Bond aumentó la resistencia de unión de los cementos resinosos a las aleaciones metálicas(AU)

Introduction: The bonding of indirect restorations is one of the most important steps, in order to achieve adequate retention and sealing of the interface between the restorative material and the tooth. Objective: To evaluate the shear bond strength of different bonding agents to two metal alloys used in dentistry. Methods: In vitro experimental study. One hundred specimens of base metal alloys, 50 nickel-chromium and 50 nickel-chromium-titanium were prepared and randomly divided into 5 groups. This division was made according to the bonding agent used: two-step self-etching system (Clearfil SE Bond; CSB), universal adhesive system (Single Bond Universal; SBU), self-adhesive resin cement (Maxcem Elite; ME), glass ionomer (IV) and zinc phosphate (ZnPO). After the application of each bonding agent, the treated specimens were stored in distilled water for 24 hr at 37 ºC and subjected to a shear bond strength test. Results: Shear bond strength was significantly influenced by the type of bonding agent (p = 0.002) and the type of alloy used (p < 0.001). Shear bond strength was highest when using the Clearfil SE Bond system, followed by Single Bond Universal; the differences between Maxcem Elite and Zinc Phosphate were not significant. Finally, IV did not show adhesion to any of the metal alloys used. Conclusions: The use of Clearfil SE Bond increased the bond strength of resinous cements to metallic alloys(AU)

Pain and removal force associated with bracket debonding: a clinical study

Abstract Objective: Pain is a problem during bracket removal, and more comfortable treatment is needed. This study examined the association of pain with the removal force required for ceramic brackets, compared with metal and plastic brackets, to determine which removal method resulted in less pain and discomfort. Methodology: 81 subjects (mean age, 25.1 years; 25 males and 56 females) were enrolled, from whom 1,235 brackets (407 ceramic, 432 plastic, and 396 metal) were removed. Measured teeth were distinguished at six segments. Pain was measured with a visual analogue scale (VAS) during the removal of each bracket. An additional grip was placed on the grips of debonding pliers with right-angled beaks; a mini loading cell sensor pinched by the grips was used to measure removal force during debonding. VAS and force values were statistically analyzed. The Kruskal-Wallis test followed by the Mann-Whitney U test with Bonferroni correction were performed for multiple comparisons; multiple regression analysis was also performed. Results: Forces in the upper and lower anterior segments were significantly smaller (p<0.05) than those in the other segments. Pain tended to be greater in the upper and lower anterior segments than in the posterior segments. In all segments, the removal force was greater for metal brackets than for plastic or ceramic brackets. Ceramic brackets caused significantly greater pain than plastic brackets for the upper and lower anterior segments. Debonding force was involved in the brackets, following adjustments for pain, upper left segment, age, and sex. Conclusions Pain and discomfort are likely to occur during bracket debonding.

Resistencia a la tracción diametral in vitro de cinco cementos dentales usados como cementantes de puentes y coronas en prótesis fijas / In vitro diametral tensile strength of five dental cements used as bridge and crown cement in fixed prostheses

RESUMEN Objetivo: El propósito de la investigación fue evaluar la resistencia a la tracción diametral in vitro de cinco cementos dentales: BisCem, Duolink, Ketac Cem, Meron, Allcem, cuatro adhesivos convencionales y un autoadhesivo polimerizado químicamente utilizados como cementantes de puentes y coronas en prótesis fijas. Materiales y métodos: Se prepararon 100 especímenes conformados por cementos: BisCem, Duolink, Ketac Cem, Meron, Allcem, los cuales se dividieron aleatoriamente en 5 grupos de 20 especímenes cada grupo sujetas a fotopolimerización y auto polimerización de 8mm de diámetro y 5mm de alto, con 2mm de distancia aproximadamente de la lámpara para la polimerización, se utilizó un formador de probetas de polietileno de alta densidad estandarizado, el tipo de muestreo es no probabilístico. Se sometieron a los especímenes de cada grupo a la prueba de tracción utilizando una máquina de ensayo universal (zwickiLine by Zwick/Roell), hasta lograr el fracaso del cemento, sometidas a una fuerza continua de 500 kg, con una velocidad de desplazamiento fija de 1 cm/min. Resultados: La resistencia promedio a la tracción diametral de probetas del cemento BisCem fue de 38,75 ± 11,56 MPa, del cemento Duolink fue 64,30 MPa, del cemento Meron 57,14 MPa, del cemento Ketac Cem es de 32,23 MPa, del cemento BisCem (38,753 MPa) y el cemento Ketac Cem (39,233 MPa). El cemento dental Duolink es aquel que presenta mayor resistencia a la tracción diametral de probetas en comparación a Meron (57,137 MPa) que es su similar. La tabulación y el análisis han sido sometidos a los test de Shapiro Wilk, análisis de varianza ANOVA y la prueba de Tuckey los valores de cada muestra se distribuyen normalmente existiendo diferencias significativas entre los grupos estudiados. Conclusiones: Las probetas del cemento de resina adhesiva Duolink evidenció una mayor resistencia a la tracción diametral con mejores valores significativos de resistencia a diferencia de los cementos Ketac Cem, Allcem, Meron y BisCem.

SUMMARY Objetive: The purpose of the research was to evaluate the in vitro diametral tensile strength of five dental cements: BisCem, Duolink, Ketac Cem, Meron, Allcem, four conventional adhesives and a chemically polymerized self-adhesive used as bridge cements and crowns in fixed dentures . Materials and methods : 100 specimens consisting of cements were prepared: BisCem, Duolink, Ketac Cem, Meron, Allcem, which were randomly divided into 5 groups of 20 specimens each group subject to photopolymerization and self-polymerization of 8mm in diameter and 5mm high, with an approximate distance of 2mm from the lamp for polymerization, a standardized high density polyethylene specimen was used, the type of sampling is not probabilistic. The specimens of each group were subjected to tensile testing using a universal testing machine (zwickiLine by Zwick / Roell), until the failure of the cement was achieved, subjected to a continuous force of 500 kg, with a fixed displacement speed of 1 cm / min Results: The average tensile strength of diametral tensile specimens of BisCem cement was 38.75 ± 11.56 MPa, Duolink cement was 64.30 MPa, Meron cement 57.14 MPa, Ketac Cem cement was 32.23 MPa, BisCem cement (38.753 MPa ) and Ketac Cem cement (39,233 MPa). Duolink dental cement is the one with the highest tensile strength of diametral specimens compared to Meron (57,137 MPa), which is similar. The tabulation and the analysis have been submitted to the Shapiro Wilk test, ANOVA analysis of variance and the Tuckey test. The values of each sample are normally distributed with significant differences between the studied groups. Conclusions : Duolink adhesive resin cement specimens showed a higher diametral tensile strength with better significant strength values unlike Ketac Cem, Allcem, Meron and BisCem cements.

Dental Cement Preparation of Zinc Oxide Eugenol-Ethoxy Benzoic Acid (ZOE-EBA) with Addition of Filler Aluminum Oxide (Al2 O3 )

@#Introduction: The quality of Zinc Oxide Eugenol-Ethoxy Benzoic Acid (ZOE-EBA) dental cement could be improved by the addition of Aluminum Oxide (Al2 O3 ). It was caused by the characteristic of alumina which are easy on fabrication process, resistant on corrosion, endurance usage, bioinert, and biocompatible. The purpose of this study was to determine the effect of the addition of Al2 O3 in ZOE-EBA cement. Methods: Nanoparticle of ZnO (zinc oxide), Al2 O3 , MgO (magnesium oxide),eugenol liquid and EBA (Ethoxy Benzoic Acid) fluid. The variations of Al2 O3 were 24%, 26%, 28%, 30%. First is the sintering on 1000°C and tested by XRD. Sintered powder was mixed with liquid, with a ratio of powder: liquid 7:1. The mechanical characteristic are compressive strength and hardness. Results: XRD test is showed that ZnO has dominant phase on the sample and there was new phase on cement powder such as Zinc-Aluminium oxide (ZnAl2 O4 ). The best result was shown on the addition of 26% of Al2 O3 composition in the 3 type test because the sample had ZnAl2 O4 phase volume fewer than 28% and 30% of Al2 O3 . This result was supported by the compressive strength and hardness which showed the optimum value at concentrations of 26%, which were 64.49 MPa and hardness of 69.33 VHN. Conclusion: Based on the result, it was found that Al2 O3 variation gives the best results in the teeth ZOE-EBA cement was 26%.

Caracterização físico-química e atividade biológica de um cimento dentário à base de quitosana, nanohidroxiapatita, nanopartículas de óxido de zinco para estimulação de células nervosas de Schwann (HS-SCH-2) / Physical-chemical characterization and biological activity of a dental cement based on chitosan, nano-hydroxyapatite, and zinc oxide nanoparticles for Schwann nervous cell stimulation (hs-sch-2)

Os cimentos dentários e ortopédicos são utilizados amplamente em diversas aplicações clínicas. Novos cimentos vêm sendo propostos visando à preservação ou regeneração tecidual. Contudo, pouco se conhece sobre o papel desses biomateriais na regeneração nervosa. As células mais comumente envolvidas na regeneração nervosa são as células de Schwann (SCs) sendo sua principal função o suporte aos axônios através da liberação de fatores de crescimento e isolamento axonal através da formação da bainha de mielina. Como estratégia da presente pesquisa, foi estudado um cimento à base da quitosana com adição de substâncias que podem atuar sinergicamente na resposta celular nervosa, tais como, as nanopartículas (NPs) de hidroxiapatita e o óxido de zinco, visto que têm propriedades bioativas e biocondutoras, além de promoverem a condução de prolongamento axonal. A doxiciclina (Dox) foi acrescida como antimicrobiano, potente inibidora de metaloproteinases (MMPs) e estimuladora da diferenciação celular no processo de regeneração tecidual. Assim, as propriedades físico-químicas e biológicas do cimento de nano-hidroxiapatita, quitosana, óxido de zinco e doxiciclina foram avaliadas, bem como a capacidade de promover um ambiente favorável para as células nervosas periféricas. Os cimentos foram caracterizados físico-químicamente mediante a determinação do pH, tempo de presa e solubilidade, lixiviação de íons cálcio, liberação controlada de doxiciclina, difração de Raios X, Termogravimetria (TG), espectroscopia Raman, molhabibidade, e testes de atividade biológica, para assim também serem avaliados em contato com células nervosas de Schwann (HS-Sch-2). O cimento apresentou pH neutro (7,0), tempo de presa de 5,7 ± 0,22 minutos, solubilidade menor que 3%, lixiviação de cálcio de 8,14 ± 0,71 mg L-1 após 14 dias, estabilidade térmica e a análise espectroscópica ratificou a presença e diferenciação das estruturas químicas dos componentes do cimento coerentemente com as imagens das análises microscópicas. Além disso, o cimento se mostrou hidrofílico, teve efeito hemolítico baixo (17%), obteve alta citocompabilidade celular em fibroblastos ATCC 3T3 (72%) e ação antimicrobiana. O cimento aumentou significativamente o crescimento das células de Schwann, 48,6% a mais do que o grupo controle (p≤0.05), e maior capacidade metabólica na análise mitótica quando em contato com este material (33%). Pode-se concluir que o cimento proposto à base de quitosana contendo hidroxiapatita e óxido de zinco nanoparticulados com adição de doxiciclina obteve efeito bioativo em células de Schwann promovendo, assim, o crescimento e a atividade mitótica celular, sendo então um biomaterial promissor para estudos de remielinização de nervos periféricos e regeneração nervosa in vivo.

Dental and orthopedic cements are used widely in several clinical applications. New cements have been proposed aimed the tissue preservation or regeneration. Nevertheless, nerve regeneration is not well known. The cells most commonly used in nerve regeneration are Schwann cells (SCs) which represent glial cells in the peripheral nervous system, their main function being supporting axons by releasing growth factors and axonal isolation through the formation of the myelin sheath. As a strategy of this research, chitosan-based cement was studied with the addition of substances that can act synergistically in the nervous cell response, such as the hydroxyapatite and zinc oxide nanoparticles (NPs), since they have bioactive and bioconductive properties; in addition to furthermore, they promote the conduction of axonal prolongation. Doxycycline (Dox) was added as an antimicrobial, a potent inhibitor of MMPs, a stimulator of cell differentiation in the tissue regeneration process. Thus, the physical-chemical and biological properties of nanohydroxyapatite, chitosan, zinc oxide and doxycycline cements were evaluated, as well as the ability to promote a favorable environment for peripheral nerve cells. Blocks of cements were characterized physically and chemically by determining pH, setting time and solubility, calcium ions leaching, controlled release of doxycycline, X-ray diffraction, Thermogravimetry (TG), Raman spectroscopy, wetness, and biological activity tests, so they can also be evaluated in contact with Schwann nerve cells (HS-Sch-2). The cement showed neutral pH (7.0), setting time of 5.7 ± 0.22 minutes, solubility less than 3%, calcium leaching of 8.14 ± 0.71 mg L-1 after 14 days, stability thermal and spectroscopic analysis confirmed the presence and differentiation of the chemical structures of the cement components coherently with the images of the microscopic analysis. In addition, the cement was shown to be hydrophilic, had a low hemolytic effect (17%), and obtained high cell cytocompatibility in ATCC 3T3 fibroblasts (72%) and antimicrobial action. The cement significantly increased the growth of Schwann cells, 48.6% more than the control group (p≤0.05), and greater metabolic capacity in the mitotic analysis when in contact with this material (33%). It can be concluded that the proposed chitosan-based cement containing hydroxyapatite and zinc oxide nanoparticulated with the addition of doxycycline has a bioactive effect in Schwann cells, thus promoting cell growth and mitotic activity, thus being a promising biomaterial for studies of remyelinization of peripheral nerves and nerve regeneration in vivo.

Effect of Ions Released and pH of Two Glass Ionomer Cements in Human Gingival Fibroblasts / Efecto de la liberación de iones y pH de dos cementos de ionómero de vidrio en fibroblastos gingivales humanos

Abstract 20. Conventional glass ionomer cements are used as dental provisional restorative materials, which present several advantages such as adhesion to the tooth mineral phase among others. On the other hand, the knowledge about biological property of glass ionomers shows various approaches and results. In this work, it was studied the in vitro biological response of human gingival fibroblasts in contact with commercial cements of glass ionomer: Mirafil® and Ionglass® and with their extracts, according to ISO 10993. The extracts of the cements, in which the cells were cultured, were adjusted at different concentrations ranging 0.1% to 100%. The cellular metabolic activity of gingival fibroblasts was measured using the Alamar Blue® reagent. The results showed a significant effect on the cellular metabolic activity correlated with the concentration of liberated ions (Al³+ and Ca²+) for both ionomers, as well as the pH variations of the culture media. This could mean that the cellular metabolic activity is substantially influenced by ions and pH of the cell culture.

Resumen 24. Los cementos de ionómero de vidrio convencionales se utilizan como materiales de restauración provisional para uso dental, los cuales presentan varias ventajas como la adhesión a la fase mineral de los dientes. Por otro lado, las propiedades biológicas de los ionómeros de vidrio muestran diversos enfoques y resultados. En éste trabajo se estudió la respuesta biológica in vitro de fibroblastos gingivales humanos en contacto con cementos comerciales de ionómero de vidrio: Mirafil® e Ionglass® y con sus respectivos extractos según la norma ISO 10993. Los extractos de los cementos en los que se cultivaron las células estaban en diferentes concentraciones: de 0.1% a 100%. La actividad metabólica celular se midió usando el reactivo Alamar Blue®. Los resultados mostraron un efecto significativo sobre la actividad metabólica celular correlacionada con la concentración de iones liberados (Al³+ y Ca²+) para ambos ionómeros, así como las variaciones de pH de los medios de cultivo. Ello podria explicar la influencia por los iones y el pH del cultivo celular en la actividad metabólica celular.

Preparation of lithium-doped poly-glycerol sebacate scaffold and its properties / 吉林大学学报(医学版)

Objective: To prepare the lithium-doped poly-glycerol sebacate (PGS-Li) scaffold using the specific effects of lithium ions and the excellent performance of PCS, and to provide the basis for its application prospects in cementation tissue engineering scaffold. Methods: The scaffolds were divided into two groups. The PGS-Li scaffolds prepared by adding lithium phosphate during the PGS cross-linking process were used as PGS-Li group, and the PGS scaffolds synthesized by the equal-purification of sebacic acid and glycerol were used as PGS group. The molecular weights of the scaffolds in two groups were determined by gel permeation chromatography. The structures of the scaffolds in two groups were analyzed by fourier transform infrared spectroscope. The surface morphology and the porosities and the pore sizes of the scaffolds in two groups were observed by scanning electron microscope. X-ray photoelectron (XPS) spectroscope and inductively coupled plasma optical emission spectrometer were used to determine the Li ion contents in the scaffolds in two groups. Thermogravimetric analyzer was used to analyze the thermal stabilities of the scaffolds in two groups. Contact angle measuring instrument was used to compare the hydrophilicities of the scaffolds in two groups. In vitro weight loss test was used to determine the degradation rates of the scaffolds in two groups. The OCCM-30 cells were divided into experimental group (added with PGS-Li scaffold extract), PGS group (added with PGS scaffold extract) and blank control group (added with DMEM culture medium). MTT assay was used to detect the proliferation activities of cells in various groups at different time (24, 48 and 72 h); the cell morphology was observed by calcein-AM staining. Results: The gel permeation chromatography results showed that the molecular weight of the PGS-Li scaffold was slightly larger than that of the PGS scaffold. The specific absorption peak of phosphate was detected in the fourier infrared spectrum of the PGS-Li scaffold. The scaffolds in two groups had irregular three-dimensional network structures under scanning electron microscope∗ and the pore size was 20- 160 /im, the porosity of PGS scaffold was (53. 92 ±2. 18) %∗ and the porosity of PGS-Li scaffold was (53. 58± 1. 73)% ? there was no statistical difference between two groups ( P> 0.05). The XPS results showed that a peak appeared at 54. 9 eV in PGS-Li group, which coincided with the Li Is binding energy, while the inductively coupled plasma emission spectrometer results showed that the Li ion content in the PGS-Li scaffold was 0.084%. The thermogravimetric analysis results showed that PGS-Li scaffolds began to degrade at a higher temperature and ceased at a lower temperature compared with PGS scaffolds. The contact angle measurement results indicated that both the materials were hydrophilic materials; the contact angle of PGS scaffold meterial was 78. 26 ±2. 00 , and the contact angle of the PGS-Li scaffold material was 69. 78 ±1.15 ; there was statistical difference between two groups (P0. 05). The calcein-AM staining results showed the green fluorescence in the OCCM-30 cells in PGS and PGS-Li groups, and there were no significant changes in the morphology of cementoblasts. Conclusion: PGS-Li scaffolds have similar composition and structure to PGS scaffolds, and have better performance in hydrophilicity and thermal stability. PGS-Li scaffolds have no effect on the proliferation of cementoblasts and have broad application prospects in cementum tissue engineering.

Effect of ultrasonic and Nd: Yag laser activation on irrigants on the push-out bond strength of fiber post to the root canal

Abstract Objective: This in vitro study aimed to compare the efficacy of irrigants using various irrigation activation methods to the push-out bond strengths of fiber post to root canal luted with self-adhesive resin cement (SARC). Methodology: Forty-eight decoronated human canines were used. The specimens were divided into four groups corresponding with the post-space irrigation process and were treated as follows: distilled water (DW) (Control) group received 15 mL of DW; sodium hypochlorite (NaOCl)+ethylenediaminetetraacetic acid (EDTA) group was treated with 5 mL of 5.25% NaOCl, 5 mL of 17% EDTA, and 5 mL of DW; passive ultrasonic irrigation (PUI) group was treated with 5 mL of 5.25% NaOCl, 5 mL of 17% EDTA, and 5 mL of DW, and each irrigant was agitated with an ultrasonic file; and laser activated irrigation (LAI) group was treated with 5 mL of 5.25% NaOCl, 5 mL of 17% EDTA, and 5 mL of DW, and each irrigant was irradiated with Nd: YAG laser. Fiber posts were luted with SARC, and a push-out test was performed. Data was analyzed using one-way analysis of variance and Tukey HSD test. Results: The bond strength values for the groups obtained were as follows: Control (10.04 MPa), NaOCl+EDTA (11.07 MPa), PUI (11.85 MPa), and LAI (11.63 MPa). No statistically significant differences were found among all experimental groups (p>0.05). The coronal (12.66 MPa) and middle (11.63 MPa) root regions indicated a significantly higher bond strength compared with the apical (9.16 MPa) region (p<0.05). Conclusions: Irrigant activation methods did not increase the bond strength of fiber post to canal.

Comparison of debonding resistance and failure type of three orthodontic band cements / Comparación de la resistencia a la descementación y el tipo de falla de tres cementantes de bandas en ortodoncia

ABSTRACT Introduction: the objective of this study was to compare the debonding resistance and failure type observed in three materials used for band cementation by means of the universal testing machine and a stereomicroscope. Methods: 72 third lower molars were collected from patients who needed extractions; metal bands were cemented on them with a pre-soldered tube and internal etching (Bracket USED, OrthoUSA, USA). The samples were randomly sorted out in three groups, forming a control group (zinc phosphate) and two pilot groups (resin-modified glass ionomer and polyacid-modified composite resin). All samples were subjected to a process of 2000 thermal cycles, and later to a debonding resistance test in the universal testing machine (Instron 3367 class 0.5, with 0-30 Kn load cell, USA) at a speed of 2 mm/min. The data were calculated in megapascals, taking into account the surface area of bands (mm2). Finally, to determine failure type, a visual inspection was conducted using a stereomicroscope (Stemi 2000C, Carl Zeiss, Göttingen, Germany AXIOCAM Carl Zeiss Microimaging, Göttingen, Germany). Results: no statistically significant differences were found among the three study groups in terms of debonding resistance (p value = 0.119). The most predominant failure type in the three cements occurred at the cemento-enamel interphase, with 61.1%, showing a statistically significant difference. Conclusion: zinc phosphate, resin-modified glass ionomer and polyacid-modified composite resin showed similar debonding resistance values and the most predominant failure type in the three band cementing materials occurred at the cemento-enamel interface; however, the resin-modified glass ionomer showed a lower percentage.

RESUMEN. Introducción: el objetivo de este estudio consistió en comparar la resistencia a la descementación y el tipo de falla observada en tres materiales utilizados para la cementación de bandas, mediante el dispositivo universal de pruebas y el estereomicroscopio. Métodos: se seleccionaron 72 terceros molares inferiores, recolectados de pacientes que requerían exodoncias, a los cuales se les cementaron bandas metálicas con tubo presoldado y grabado interno (Bracket USA, OrthoUSA, USA). Los especímenes fueron distribuidos de forma aleatoria simple en tres grupos, formando un grupo control (fosfato de zinc) y dos grupos experimentales (ionómero de vidrio modificado con resina y resina compuesta modificada con poliácido). Todos los especímenes fueron sometidos a un proceso de 2000 ciclos térmicos, para posteriormente realizar la prueba de resistencia a la descementación en el dispositivo universal de pruebas (Instron 3367 clase 0,5, con celda de carga 0-30 Kn, EE.UU.) a una velocidad de 2 mm/min. Los datos fueron calculados en megapascales, teniendo en cuenta el área de la superficie de la banda (mm2). Finalmente, para determinar el tipo de falla se realizó una inspección visual utilizando un estereomicroscopio (Stemi 2000C, Carl Zeiss, Göttingen, Germany AXIOCAM Carl Zeiss Microimaging, Góttingen, Germany). Resultados: en cuanto a la resistencia a la descementación, no se observaron diferencias estadísticamente significativas entre los tres grupos estudiados (valor p = 0,119). El tipo de falla más predominante en los tres materiales cementantes se presentó en la interfase cemento-esmalte, con 61,1%, con una diferencia estadísticamente significativa. Conclusión: el fosfato de zinc, el ionómero de vidrio modificado con resina y las resinas compuestas modificadas con poliácido presentaron una resistencia similar a la descementación, y el tipo de falla que predominó en los tres materiales cementantes de bandas se presentó en la interfase cemento-esmalte; sin embargo, para el ionómero de vidrio modificado con resina esto ocurrió en un menor porcentaje.

Effect of cement washout on loosening of abutment screws and vice versa in screw- and cement- retained implant-supported dental prosthesis

PURPOSE: The purpose of this study was to examine the abutment screw stability of screw- and cement-retained implant-supported dental prosthesis (SCP) after simulated cement washout as well as the stability of SCP cements after complete loosening of abutment screws. MATERIALS AND METHODS: Thirty-six titanium CAD/CAM-made implant prostheses were fabricated on two implants placed in the resin models. Each prosthesis is a two-unit SCP: one screw-retained and the other cemented. After evaluating the passive fit of each prosthesis, all implant prostheses were randomly divided into 3 groups: screwed and cemented SCP (Control), screwed and noncemented SCP (Group 1), unscrewed and cemented SCP (Group 2). Each prosthesis in Control and Group 1 was screwed and/or cemented, and the preloading reverse torque value (RTV) was evaluated. SCP in Group 2 was screwed and cemented, and then unscrewed (RTV=0) after the cement was set. After cyclic loading was applied, the postloading RTV was measured. RTV loss and decementation ratios were calculated for statistical analysis. RESULTS: There was no significant difference in RTV loss ratio between Control and Group 1 (P=.16). No decemented prosthesis was found among Control and Group 2. CONCLUSION: Within the limits of this in vitro study, the stabilities of SCP abutment screws and cement were not significantly changed after simulated cement washout or screw loosening.

Biomechanical three-dimensional finite element analysis of monolithic zirconia crown with different cement type

PURPOSE: The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS: The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS: Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION: The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns.

Analysis of stresses during the polymerization shrinkage of self-curing resin cement in indirect restorations: A finite-element study.

Background: Adhesive cementation is essential for the longevity of indirect esthetic restorations. However, polymerization shrinkage of resin cement generates stress, which may cause failures in the tooth–restoration interface. So, understanding of the biomechanics of resin cement is important for predicting the clinical behavior of an esthetic indirect restoration. Aims: To analyze the stresses generated during polymerization shrinkage of self‑curing resin cement in ceramic and in indirect resin (IR) restorations, using the finite‑element method (FEM). Settings and Design: Numerical study using the finite‑element analysis. Materials and Methods: A three‑dimensional (3D) model of a second molar restored with ceramic or IR onlay restoration was designed. The polymerization shrinkage of self‑curing resin cement was simulated in FEM software using an analogy between the thermal stress and the resulting contraction of the resin cement. The localization and values of tensile stresses in the dental structure, cement, and adhesive layer were identified. Results: The location and value of the tensile stresses were similar for the two restorative materials. High tensile stresses were identified in the axiopulpal wall and angles of the tooth preparation, with the major stresses found in the cement located in the axiopulpal wall. Conclusions: The high stresses values and their concentration in the angles of the prepared tooth emphasize the importance of round angles and the use of cements with lower rates of shrinkage.

Cimentação em cerâmicas: evolução dos procedimentos convencionais e adesivos / Cementation in ceramics: improvement of conventional and adhesive procedures

O objetivo deste estudo foi coletar dados científicos para revisão de literatura sobre cimentação de cerâmicas, ressaltando propriedades, técnicas, indicações e contraindicações. O agente cimentante ideal deve apresentar como principais características alta resistência à compressão, tração e cisalhamento, além de selamento marginal adequado, baixa solubilidade aos fluidos bucais e espessura mínima de película. Em relação à técnica, foi observado que diferenças na microestrutura e composição dos sistemas cerâmicos exigem protocolos específicos de preparo da peça cerâmica e da superfície dentária. Atualmente, os tipos de agentes cimentantes disponíveis são: fosfato de zinco, ionômero de vidro convencional e modificado por resina, cimentos resinosos e autoadesivos. A evolução desses materiais ocorre no sentido de melhorar propriedades e simplificar a técnica.

The objective of the study was to collect scientific data to perform a literature review of ceramic cementation, highlighting their properties, techniques, indications and contraindications. An ideal luting agent has to present as main characteristics high compressive strength, tensile and shear, adequate marginal sealing, low solubility to oral fluids and minimal thickness of film. Concerning the technique, it was observed that differences on microstructure and composition on ceramic systems require specific protocols on preparation for the ceramic structure and for the dental element surface. Nowadays, the available luting agents are: zinc phosphate, conventional and modified glass ionomer, resin cements and self adhesive cements. The evolution of these materials occurs to improve properties and to simplify technique.

Comparison of the retention of the full veneer casted gold crowns with varying convergence angle, crown length and dental cements / 대한치과보철학회지

PURPOSE: The aim of this research was to establish the effect and variation in differing convergence angle and length of abutment on the retention of full veneer casted gold crown. MATERIALS AND METHODS: Two different length,5 mm and 10 mm in height with convergence angles of 5, 10, 15 and 25 degrees crowns were fabricated. Cementation was done using cements; zinc phosphate cement (Fleck's zinc phosphate cement), resin-modified glass ionomer cement (Vitremer) and resin cement (Panavia 21). These were tested for tensile force at the point of separation by using Instron Universal Testing Machine. Statistical analysis was done by SAS 6.04 package. RESULTS: In all cements the mean retention decreased with significant difference on increase of convergence angle (P<.05). Increase in every 5 degree-convergence angel the retention rate decreased with resin-modified glass ionomer cement of 15.9% and resin cement of 14.8%. With zinc phosphate cement, there was largest decreasing rate of mean retention of 25.5% between convergence angles from 5 degree to 10 degree. When the crown length increased from 5 mm to 10 mm, the retention increased with the significant difference in the same convergence angle and in all types of cement used (P<.05). CONCLUSION: The retention was strongly dependent on geometric factors of abutment. Much care is required in choosing cements for an optimal retention in abutments with different convergence angles and crown lengths.

Histopathological evaluation of root canal filling materials for primary teeth

This study aimed to assess the response of apical and periapical tissues of dogs' teeth after root canal filling with different materials. Forty roots from dogs' premolars were prepared biomechanically and assigned to 4 groups filled with: Group I: commercial calcium hydroxide and polyethylene glycol-based paste (Calen®) thickened with zinc oxide; Group II: paste composed of iodoform, Rifocort® and camphorated paramonochlorophenol; Group III: zinc oxide-eugenol cement; Group IV: sterile saline. After 30 days, the samples were subjected to histological processing. The histopathological findings revealed that in Groups I and IV the apical and periapical regions exhibited normal appearance, with large number of fibers and cells and no resorption of mineralized tissues. In Group II, mild inflammatory infiltrate and mild edema were observed, with discrete fibrogenesis and bone resorption. Group III showed altered periapical region and thickened periodontal ligament with presence of inflammatory cells and edema. It may be concluded that the Calen paste thickened with zinc oxide yielded the best tissue response, being the most indicated material for root canal filling of primary teeth with pulp vitality.

O objetivo deste estudo foi avaliar a resposta dos tecidos apicais e periapicais de dentes de cães, após obturação dos canais radiculares com diferentes materiais indicados para dentes decíduos. Foram utilizados pré-molares de cães, totalizando 40 raízes que, após pulpectomia e preparo biomecânico, foram divididas em 4 grupos, nos quais os canais radiculares foram obturados com os seguintes materiais: Grupo I - pasta comercial composta de hidróxido de cálcio e polietileno glicol 400 (Calen®) espessada com óxido de zinco; Grupo II - pasta composta de iodofórmio, Rifocort® e paramonoclorofenol canforado; Grupo III - cimento de óxido de zinco e eugenol; e Grupo IV - solução salina. Decorridos 30 dias, as peças foram submetidas ao processamento histológico. De acordo com os resultados da análise histopatológica observou-se que nos Grupos I e IV as regiões apical e periapical apresentaram aspecto de normalidade, com grande número de fibras e células e ausência de reabsorção dos tecidos mineralizados. No Grupo II observou-se infiltrado inflamatório e edema leves, com discreta fibrogênese e reabsorção óssea. O Grupo III apresentou alteração na região periapical e ligamento periodontal ampliado, com presença de células inflamatórias e edema. Os resultados obtidos permitiram concluir que a pasta Calen espessada com óxido de zinco apresentou a melhor resposta tecidual, sendo a mais indicada para a obturação de canais radiculares de dentes decíduos com vitalidade pulpar.

Experimental study on dental cement / 中国基层医药

0.05).The setting time of hydroxyaptite and glass ions cements with Co-F were longer but there was little effect on zinc phosphate cements. Conclusion The Co-F agent added to dental cement can not only improve the compressive strength but also contin- ually release fluoride.

The effect of cementation materials on the fracture resistance of Artglass crown / 实用口腔医学杂志

Objective: To study the effect of cementation materials on the fracture resistance of metal free premolar Artglass crown. Methods: Thirty extracted human maxillary premolars were regularly prepared for cementation. Artglass crowns were cemented onto the teeth with zinc phosphate cement (ZnP), glass ionomer cement(GIC)or a resinous cement in combination with a dentinal bonding agent. Each of the cementation material was applied in 10 premolars. Artificial crowns were vertically loaded until the Artglass crowns compressed to failure. Significant differences of fracture loads between experimental groups were assessed by paired t test. Results: The fracture load(N) of ZnP, GIC and resinous cement were 1 743.1 ?383.4, 1 682.4?613.7 and 2 226.9?270.1 respectively( P