Papers by Keyword: Dental Materials

Abstract: Present research work reports a study on new mechanical phenomenon of the porous Ti-3.5Nb-3.5Zr materials that address for implant materials in dental. The mechanical testing samples were prepared by two-step sintering method with dimension of 10 mm and height of 10mm. The compressive tests were carried on MTS instrument to determine the strain-stress curves. Then mechanical behavior of the materials was analyzed from those curves. For samples after sintering without space holder and binder addition, there were three deformation regions on the curves that were linear elasticity, plateau and densification. The mechanical behavior of materials was modeled, and the main parameters in the model were identified from the strain - stress curve. For sample after sintering with space holder and binder, materials were brittle. The mechanical properties of those samples were also determined. Microstructures of materials before mechanical testing were observed by SEM, and the surface was also analyzed by XRD.

Abstract: The influence of the treatment of the surface of IPS Empress II (e-max) glass-ceramic dental material with different silane agents on the surface roughness of this glass-ceramic was evaluated. IPS Empress II (e-max) cores were treated with five different commercial silane agents used in dentistry nowadays, for several periods of time and were finally air dried. After silanization, the surfaces of the glass-ceramic cores were observed with a light profilometer, a scanning electron microscope (SEM), and an atomic force microscope (AFM). The values of surface roughness (R_a) were also measured with the light profilometer. The results showed an important effect of silane treatment applied for different periods of time, especially for prolonged treatment for 24 hours, on the surface roughness of IPS Empress II (e-max). These results can have an important impact on the deep understanding of the cementation protocols applied in modern dentistry.

Abstract: The effect of Er,Cr:YSGG laser for ablation of commercialized adhesive dental materials were studied using 12 sets of tooth samples. The surface morphology and composition of the tooth samples was observed before and after irradiation using FESEM and EDX. Time dependency of exposure is observed in the tooth sample. Adhesive material Grēngloo produced better ablation on long exposure compared to adhesive material Blūgloo. The ablation effect was also compared between presence and absence of water. The enamel surface produced is highly dependent on the technique used to ablate the adhesive material. Without water, enamel surface appeared roughed and depth of crater was also created. In particular, both materials produce different quality of ablation and reacted differently under different laser parameter and setting.

Abstract: In this work, pre-sintered zirconia ZrO₂(Y₂O₃) ceramics were characterized aiming its acceptance in standard ISO 6872:2015 (Dentistry-Ceramic Materials). Pre-sintered zirconia blocks were sintered at 1450oC, 1500oC, 1530oC or 1600oC. Sintered samples were sanded, polished and characterized by relative density, crystalline phase, microstructure, hardness, fracture toughness, bending strength, translucence and dilatometry. The results indicated that the ceramic studied presents hardness superior to 1200HV, fracture toughness of 8MPa.m^1/2 and bending strength superior to 900MPa. Zirconia sintered at temperature of 1600oC, presented exaggerated grain growth which reduces the material toughness. With the porosity decreasing and the grain growth increasing it happens the increase of translucence, but the mechanical aspects must be analyzed carefully, in order to establish zirconia reliability for using it in dental prostheses.

Abstract: This work developed a ceramic material for dental application, spinel-base (MgAl₂O₄), a ceramic material with recognized translucency. Spinel powders were uniaxially pressed at 100 MPa and pre-sintered in order to obtain porous ceramic blocks. The pre-sintered blocks were characterized and indicated 80% of relative density. X-ray diffraction (XRD) only showed MgAl₂O₄ phase. Samples with 15 x 15 x 1 mm were submitted to infiltration using glass rich in lanthanum (La). The products were characterized by scanning electron microscopy (SEM) and mechanical properties, as hardness and fracture toughness. Results were compared to the commercial product VITA-InCeram Spinell. Relative densities exceeding 92%, hardness around 900 HV and high toughness 2.5 MPa.m^1/2 were obtained for both examined systems.

Abstract: The aim of this study was to evaluate the dependence of sintering conditions on mechanical properties and microstructure of zirconia stabilized by yttria. Commercial blocks of pre-sintered of zirconia stabilized (DeguDent Dentsply, Germany-Cercon) were investigated in this study. The blocks belonging to group 1 were sintered under the recommended conditions by the manufacturer (1350°C for 6 hours). The blocks of group 2 were sintered under 1500°C for 6 hours. The blocks of group 3 were sintered under 1350 C for 14.5 hours. The results indicated that the sintering conditions influenced the mechanical properties and microstructure of zirconia. The three sintering conditions analyzed in this study produces zirconia bodies with properties adequate to be used in clinical function. However, the decisive factor for change in the sintering conditions should be the cost/benefit during the prosthetical process and longevity of clinical material to perform its function in the oral cavity.

Abstract: Polymer-infiltrated-feldspar used for restorative composite CAD/CAM blocks were prepared by infiltrating polymerizable monomers into the partially sintered feldspar blocks. The flexural strength was tested according to the standard of ISO-4049. The micro-structure was examined by SEM. The effects of sintering temperature, high pressure and the addition of SiO₂ and Al₂O₃ on the ultimate flexural strength were evaluated. The flexural strength corresponding to infiltration with pressure was much higher than that without pressure at high sintering temperature. The addition of SiO₂ and Al₂O₃ into the natural feldspar mineral increased the flexural strength of the blocks significantly.

Abstract: Removable dentures aim to improve masticatory function, esthetics and phonetics. Different materials have been used as denture base materials but poly(methyl methacrylate) (PMMA) is most frequently used in most countries. Surface related properties of denture base materials (roughness, surface free energy, wettability, hydrophobicity, etc.) are of clinical importance since they affect plaque accumulation and staining. Surface roughness specifically influences the adhesion and retention of Candida Albicaans, which has a particular importance in denture-induced stomatitis pathogenesis. Bacterial plaque retention directly affects oral hygiene even if the patient achieves an appropriate cleaning of the denture. Ideally, denture base materials should be smooth so plaque adherence is reduced or even avoided. Test specimens of four heat polymerized materials were obtained by a classical press-pack dough molding technique of 1.5 mm thick wax-plate flasked in class III Moldano followed by the recommended polymerization regime. One of the materials was processed through a fast polymerization cycle. Injection-type materials were automatically produced using a dedicated injection unit. All plates were sectioned in 10 mm x 10 mm samples. No finishing protocol was applied. The selected specimens were examined under field emission scanning electron microscope (SEM). A large variation of surface topography was recorded between materials. There were visual differences between the four heat polymerized resins but also between the two injection-type materials. Surface topography was also influenced by the polymerization regime. Within the limitations of our study, we found that surface topography is influenced by the chemical composition of each material, the heat cure cycle and the processing method.

Abstract: Posterior composite restorations are difficult to contour and polish due to their occlusal anatomy and opposing occlusion. Our study describes a technique for duplicating occlusal surface anatomy, using different dental materials that are able to copy anatomic details. The aim of the study was to evaluate the efficiency of occlusal matrix technique, by comparing technical ease of different dental materials. The study was conducted on extracted teeth which had intact occlusal surfaces or initial carious lesions at this level. An impression of the occlusal surface was made prior to cavity preparation, with four different dental materials: a flow composite, a dual-cure resin cement, a temporary acrylic resin (powder and liquid) and a temporary crown and bridge two-component material in a Unidose®. When the last layer of composite has been placed, the occlusal matrix was forced into the uncured composite to replicate the original occlusal surface, instead of performing manual curing and shaping as in the standard approach. Time needed for complete finishing the case, the hardness of each occlusal matrix and the final morphology obtained were evaluated. The main benefits of the occlusal matrix technique are the technical ease of use due to its simplicity and its high accuracy in reconstructing occlusal morphology. Although the shortest time needed for occlusal matrix preparation was for the dual-cure resin cement, the best oclusssal matrix was obtained with the temporary acrylic resin (powder and liquid).

Abstract: The aim of this study was to determine the hardness and the elasticity modulus of the two composite resins base of BISGMA with different inorganic particles: a nanoparticulated with a ceramic withload, (Filtek Z350XT-3M) with and without thermal activation and a microhybrid with no ceramic load (Opallis-FGM). The samples were prepared and subjected to the tests of Vickers hardness (Shimadzu HMV) and acoustic excitation pulse (Sonelastic ®). The samples were divided into three groups: G1-Filtek Z350 XT; G2-Filtek Z350XT MO (subject to further polymerization microwave) and G3-Opallis. The results showed that the hardness of G2 was significantly higher than the groups G1 and G3. The elastic modulus was higher than the G2 to G1 and G3. One can conclude that the resins filled with inorganic ceramic filler showed higher hardness and elastic modulus. The thermal activation increased the hardness and the elasticity modulus of the resin with ceramic load.