Papers by Keyword: Molar

Abstract: Due to the lower opacity and translucency of many core materials, bilayered ceramic crowns were introduced to obtain sufficient veneer support and to improve aesthetics. Interfaces can have significant influence on the mechanical performance of layered structures. Veneer chipping and zirconia frameworks fractures are critical issues in all-ceramic restorations. The objective of this study was to assess failure analysis of bilayered all-ceramic molar crowns, evidenced by different type of fractures. Experiments were conducted on a right first maxillary molar. Bilayered all-ceramic crowns were obtained with a 0.5 mm thick zirconia milled framework and veneered with hot-pressed ceramics. The specimens were tested at compressive load until failure. The typical macroscopic crack pattern of all samples showed that crack propagation resulted in more broken pieces with sharp edges. Ceramic materials show considerable variation in strength due to their extreme sensitivity to cracks. Understanding the fracture behavior of dental ceramics and its relation to different materials and restorations is important from a clinical point of view.

Abstract: This paper presents an experimental study of geopolymer material as an alternative material for grouting. The samples were class F Fly ash as raw materials, activated with 6M, 8M, and 10 M concentration of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃). Superplasticizer from naphtelenesulphonatedand polycarboxylic ether hyper plasticizer in the range of 0-3% were added to improve its workability. Some test methods are conducted to the samples to know the fresh and hardened-state properties of geopolymer mixture.The experimental results showed that the longest initial and final setting time were about 13 minutes and 20 minutes, respectively at the lowest alkali concentration mixtures. The flowability of geopolymer paste and geopolymer mortar were 154% with flow table test. However, mixtures with the highest alkali concentration showed highest compressive strength of 104,5 MPa and 71 MPa for pasteand mortar respectively.

Abstract: Teeth is the most hard tissue in human body, and its component contains over 96 wt.% inorganic mineral. When the teeth were destroyed by chewing, whiten, etched and friction, etc., ceramic materials are one of the most widely used materials for dental defect repairing or replacement [1-3]. Stress distribution of teeth is necessary to evaluate due to bearing the heavier load, especially the mandibular first molar. But its structure is so complex as not to measure the stress distribution accurately. With the development of CAD/CAM technology, some new technology and equipments occurrence may supply for good methods to evaluate the characteristics of complex structures [4-7]. Since Farah introduced a finite element analysis method into the field of oral medicine in 1973, the method was widely used to research the teeth mechanics, which is most suitable and efficient tools compared with other technologies [8]. In this paper, molar stress distributions were analyzed. By three-dimensional optical scanner and computer 3D design software such as solidworks, Geomagic Studio, CATIA V5, a molar model was built with accuracy and effectiveness, further the mechanical properties of ceramics denture was achieved.

Abstract: The dental community is using a variety of ceramic restorative materials such as porcelains (leucite or alumina based), glass-ceramics (leucite, mica, lithium disilicates), alumina-glass infiltrated, and CAD-CAM ceramics including pure alumina and zirconia (3Y-TZP) core materials. Polycrystalline ceramics such as alumina and zirconia serve as substructure materials (i.e., framework or core) upon which glassy ceramics are veneered for an improved appearance. Under masticatory loads, sudden fracture of the full-thickness restoration or of the veneering ceramic (chips) may occur. Stereomicroscope and scanning electron microscope analyses were used to perform qualitative (descriptive) fractography on clinically failed dental ceramic restorations. The most common features visible on the fracture surfaces of the glassy veneering ceramic of recovered broken parts were hackle, wake hackle, twist hackle, arrest lines, and compression curls. The observed features are indicators of the local direction of crack propagation and were used to trace the crack’s progression back to its initial starting zone (the origin). This paper presents the applicability of fractographic failure analyses for understanding fracture processes in brittle dental restorative materials and it draws conclusions as to possible design or processing inadequacies in failed restorations.