Magister Scientiae Dentium - MSc(Dent) / CAD/CAM crowns have become popular due to the many advantages associated with this technology. Optimal bonding adhesion is crucial for the durability of these indirect restorations and many factors influence this crucial step. Currently, there is no consensus or evidence-based guidelines on the best adhesion protocol for CAD/CAM crowns fabricated from hybrid materials. This study was aimed at investigating the influence of three types of resin cements on the shear bond strength of a hybrid CAD/CAM material in vitro.

Indiana University-Purdue University Indianapolis (IUPUI) / The luting agent is a crucial factor in the outcome of cemented fixed restorations. A new water-based cement, Ceramir C&B (CM), approved to be marketed in the US, is composed of calcium aluminate and glass ionomer. CM is a luting agent indicated for permanent cementation of cast restorations, all-zirconia or all-alumina crowns, and prefabricated metal and cast dowel and cores. The manufacturer claims that the cement has demonstrated favorable biocompatibility properties when tested in vitro and in vivo and has proven to be bioactive. The objective of this study was to evaluate volumetric dimensional changes and the amount of Ca2+ released by the new luting agent. Twenty specimens of each material, namely calcium aluminate glass ionomer, resin-modified glass ionomer, and two resin luting agents, were fabricated and weighed. The 20 specimens for all materials were divided into four groups (five samples in each group) based on storage conditions: silicone oil at 22°C and 37°C and distilled water at 22°C and 37°C. Using the manufacturers’ instructions for each material, cylindrical specimens were prepared with dimensions of 7 +0.1 mm in diameter and 2 +0.1 mm in height. A 0.01-mg resolution balance was used to determine volumetric dimensional change using an Archimedean equation. Measurements were made 30 minutes after mixing, and at the time intervals of 7 days, 14 days, 21 days, and 30 days, and after total dehydration of the specimen. Chemical analyses of the solutions were performed using atomic absorption spectroscopy to determine the Ca+2 ion concentration. Moreover, the pH values were measured to determine the OH–concentration in the solutions. The results showed that CM had the most expansion among the tested luting agents in distilled water at 22°C and 37°C, and significantly increased at higher temperature. In silicone oil, resin-modified glass ionomer shrank the most and also shrank more with the high temperature. The result of the ion concentration analysis indicated that Ca+2 and OHion release increased with increasing time and also significantly with temperature rise. In conclusion, calcium aluminate-glass ionomer exhibited the most significant dimensional change when stored in water storage. The solubility of the tested luting agents should be evaluated in the future because they were not evaluated in this study. Furthermore, to evaluate the clinical effect of the dimensional changes, the impact on the gap formation at tooth-crown margins should be determined in future work.

Indiana University-Purdue University Indianapolis (IUPUI) / MICROTENSILE BOND STRENGTH OF NEW PASTE/PASTE RESIN-MODIFIED GLASS IONOMER CEMENT SYSTEMS: THE EFFECT OF DENTIN PRETREATMENT by Yasser Fawaz Al-fawaz Indiana University School of Dentistry Indianapolis, Indiana Background: In order to improve the clinical performance of RMGIC 3M ESPE and GC America introduced paste/paste resin-modified glass ionomer cements, Ketac™ Nano and Fuji Filling™ LC, respectively. Both companies developed non-rinse substrate conditioners (i.e., Ketac Nano Primer-3M ESPE and GC Self-Conditioner-GC America) that should be used with these new materials instead of the conventional polyacrylic acid. It has been also advised by both manufacturer’s to use this novel substrate conditioner with the previously marketed RMGICs. Objective: to investigate whether the use of novel non-rinse conditioners (i.e., Ketac Nano Primer 3M ESPE and GC Self Conditioner GC America) as substrate pre-treatment and the new paste/paste resin-modified glass-ionomer cement, RMGIC (Ketac™ Nano 3M ESPE and Fuji Filling™ LC GC America) would affect the microtensile dentin bond strength (µTBS) of the material when compared to the traditional RMGIC with polyacrylic acid as a surface substrate pre-treatment. Materials and Methods: 96 extracted non-restored human molar were sectioned to expose occlusal dentin. Dentin surface was finished with SiC paper to standardize the smear layer. Bonding protocols of the different materials to dentin were performed following the use of two dentin conditioners. Eight groups (n=12) were tested: G1: Ketac Nano Primer + Ketac Nano, G2: Ketac Conditioner + Ketac Nano, G3: Ketac Nano Primer + Photac Fil, G4: Ketac Conditioner + Photac Fil, G5: GC Self Conditioner + Fuji Filling LC, G6: GC Cavity Conditioner + Fuji Filling LC, G7: GC Self Conditioner + Fuji II LC and G8: GC Cavity Conditioner + Fuji II LC. The specimens were stored in 37°C for 24h in 100% humidity before cutting non-trimmed beams for the µTBS with cross-sectional areas of approximately 0.8 × 0.8 mm2. Nine beams were used from each specimen. Test was done using universal testing machine at a cross-head speed of 1mm/min. Debonded specimens were examined under a stereomicroscope at 45× magnification to evaluate the failure mode. Eight randomly chosen representative debonded beams were imaged under a scanning electron microscope (SEM). Results: µTBS in MPa (mean ± SE) were: G1: 9.5±1.0, G2: 11.0±1.0, G3:20.0±1.0, G4:16.8±0.9, G5: 15.1±1.0, G6: pre-test failure, G7: 20.0±1.0, G8:14.1±0.9. Weibull-distribution survival analysis was used to compare the differences in microtensile peak stress among the groups. Group5 has cohesive predominant faultier mod while the other groups have adhesive predominant failure. Conclusion: Within the limitations of this study, the use of the novel non-rinse conditioners did not improve the microtensile bond strength of new paste/paste RMGIC to dentin. In fact, the use of the novel non-rinse conditioners enhanced the bond strength of the traditional RMGIC to dentin.

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Endodontics / Master / Master of Dental Surgery

published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

O objetivo no presente trabalho foi avaliar a resistência da união adesiva de uma cerâmica vítrea (IPS e.max Press) fixada sobre o esmalte de dentes bovinos. Empregaram-se dois métodos de cimentação um, com a fotoativação prévia do adesivo; outro, com a fotoativação simultânea do adesivo e do cimento compósito após a fixação do disco cerâmico, que tinha 5mm de diâmetro e 2mm de espessura. Pela combinação de dois sistemas adesivos fotopolimerizáveis (Optibond FL e Single Bond 2), e de dois cimentos (Variolink II e RelyX ARC), um fotopolimerizável e outro de cura dupla associados às duas técnicas de cimentação formaram-se oito condições de cimentação. As amostras foram submetidas a ensaio de cisalhamento pela técnica do fio de aço. Com base nos valores encontrados nas condições estabelecidas, após o respectivo tratamento estatístico, foi possível concluir que: a) a técnica de cimentação com fotopolimerização simultânea do adesivo com o cimento produziu índices de resistência superiores aos obtidos pela técnica de fotopolimerização prévia do adesivo; b) A combinação do adesivo Single Bond 2 com o cimento Variolink II resultou em menores valores de resistência adesiva, diante das outra três combinações de cimentos e adesivos formadas. / The aim of this study was to evaluate the strength of adhesive bonding of a glass-ceramic (IPS e.max Press) fixed on the enamel of bovine teeth. There were used two methods of cementation one in which the adhesive was pre-cured, and another in which the photopolymerization of the adhesive and composite cement was performed simultaneously after the fixing of ceramic disc, which was 5mm in diameter and 2mm thick. Through a combination of two light cured adhesive systems (Single Bond and FL Optibond 2) and two resin cements (Variolink II and RelyX ARC), one light-cured and another dual-cured associated with the two luting techniques eight conditions of cementation were formed. The samples were subjected to shear test technique. Under the established conditions, after statistical treatment of results the following conclusions could be drawn: a) the cementation technique with simultaneous curing of the adhesive with cement produced resistance rates higher than those obtained by the technique of pre-curing the adhesive; b) the combination of adhesive Single Bond 2 with cement Variolink II resulted in lower bond strength, in comparison with the other three combinations of cements and adhesives formed.

Glass‐ionomer cements (GICs) are acid base reaction cements used in dentistry for restorative applications. In conventional GICs aluminosilicate glass is used to react with a polyalkenoic acid such as poly acrylic acid. Glass–ionomer cements have the potential to be used for bone cement applications, however there is a concern over the neurotoxicity of aluminium in the glass component of these cements. In this work zinc containing phosphate glass based glass–ionomer cement has been developed for the bone cement application. In this relation structure of zinc containing phosphate glasses in the system Na2O:CaO:ZnO:P2O5 ranging from metaphosphate compositions to invert phosphate compositions has been examined. Various advanced techniques in solid state nuclear magnetic resonance (NMR) such as dipolar recoupling and solid state NMR of low  quadrupolar nuclei (67Zn and 43Ca) and neutron diffraction have been employed. Special emphasis has been focused on structural role of zinc in glasses of different composition and the effect of different cations on coordination of zinc along with the effect on phosphate tetrahedra. 67Zn and 43Ca solid state NMR spectra of selected glass samples have been successfully acquired at ultrahigh field 900 MHz using Solid Echo pulse sequence. In addition solid state NMR spectra of two polymorphs of crystalline Zn(PO3)2 have also been acquired at 850 MHz using DFS– WURST–QCPMG pulse sequence in order to distinguish between the magnitude and orientation of electric field gradient (EFG) of zinc in octahedral and tetrahedral coordination. Structure determined through various techniques has been related to the dissolution behaviour of glass compositions from metaphosphate to invert phosphate. A decrease in pH of surrounding medium has been observed due to the presence of zinc. Insertion of ZnO4 tetrahedra between PO4 tetrahedra has been observed in invert phosphate glasses with high zinc oxide content which renders them suitable for glass– ionomer cements. Glass–ionomer cement from glass composition 10Na2O:50ZnO:10CaO:30P2O5 and hydroxyapatite and, acrylic acid and vinyl phosphonic acid co‐polymer has been produced successfully.

Orientador: Maria Amélia Máximo de Araújo / Banca: Ivone de Oliveira Salgado / Banca: Michel Nicolau Youssef / Banca: Sérgio Eduardo de Paiva Gonçalves / Banca: Horácio Faig Leite / Resumo: O objetivo deste estudo foi comparar a efetividade de três cimentos: Cimento Resinoso (3M), Variolink (Vivadent) e Fuji Plus (GC Coorp.); na adesão de discos de porcelana (Fortune,Williams) e de um polímero de vidro (Artglass, Kulzer), à dentina bovina. A superfície vestibular de 120 incisivos bovinos, previamente incluídos em resina acrílica, foi planificada com lixa d'água (granulação 80), e a dentina exposta e regularizada, com lixas de papel de granulação decrescente (240,400 e 600), sob-constante refrigeração de água. Sobre estas superfícies foram cimentados discos, de 5mm de diâmetro x 3mm de altura, de porcelana ou do polímero de vidro, que tinham recebido em sua base um alívio de 40µm, para conter o cimento e padronizar sua espessura. A cimentação foi estática, realizada com o auxílio de um delineador adaptado, e os cimentos empregados de acordo com as indicações dos fabricantes. Os espécimens foram divididos aleatoriamente em grupos de dez. Cada dois grupos receberam o mesmo material e cimento; sendo que destes, um foi testado após 24 h e o outro após seis meses, quanto à resistência ao cisalhamento, em máquina de ensaios universal Instron. Os valores de resistência adesiva obtidos, receberam os testes estatístico ANOVA e de Tukey, 0,05%. As superfícies fraturadas foram observadas em estereomicroscópio (Karl Zeiss). Os resultados demonstraram que o Cimento Resinoso (3M) foi o que apresentou os maiores valores médios de resistência adesiva (14,16MPa); que a adesão da porcelana foi superior; e, que o tempo influenciou, apresentando a avaliação após seis meses, resultados maiores que após 24h. As fraturas foram predominantemente mistas, com algumas fraturas coesivas do cimento e dos materiais também. Pode ser concluído que o Cimento Resinoso e os procedimentos empregados ofereceram uma razoável resistência ao cisalhamento, tanto à porcelana , ... / Abstract: The aim of this study was to investigate the effectiveness of three luting agents : Resin Cement (3M), Variolink (Vivadent) e Fuji Plus (GC Coorp.); in bonding porcelain (Fortune, Williams) and glass polymer (Artglass, Kulzer) discs. To bovine dentin. The facial surfaces of 120 bovine incisors, previously mounted in self-cured resin, were ground flat on wet 80-grit SiC paper. Dentin surfaces exposed had their final finish accomplished by grinding on wet 240, 400 and 600-grit SiC paper. The specimens were randomly assigned to test groups of ten samples. Onto the pretreated dentin surfaces, the discs (5mm diameter,3mm height) were cemented Jhey were seated to a standardized luting thickness of 40µ. Each two groups were cemented with the same luting agent, and one of them shear tested after 24 h and the other after 180 days in an Instron machine. The bond strength data obtained were analysed by ANO VA and the Tukey test, 5%. The mode of failure was classified. The shear test results indicated significant differences among the luting agents: Variolink II (6, 02MPa), Fuji Plus (1 1,20MPa) and with the highest shear bond stregth accomplished when the 3M Resin Cement was the luting agent (14,16MPa). Higher values were also obtained with the porcelain discs and after the 180 days storage period. Mode of failure varied among the groups, with predominance of mixed fractures at the tooth/cement interface, and with a few cohesive porcelain and glass polymer fractures. It can be concluded that the Resin Cement (3M) and the procedure used offer reasonable strength on the porcelain and dentin site / Doutor