This article explains the mechanism of indirect retention for RPDs and discusses the factors which determine its effectiveness. Examples are given of designs which incorporate indirect retention. (+info)
Effects of Ga addition on the mechanical properties of 35Ag-30Pd-20Au-15Cu alloy.
(2/18)
Ten 35Ag-30Pd-20Au-15Cu alloys containing 0.00, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 2.00, 4.00, or 6.00% Ga were experimentally prepared to investigate the effect of Ga on their mechanical properties in addition to their use for denture frameworks, connectors and clasps. The effect of Ga addition on the mechanical properties was marked with a significant increase in the tensile strength, 0.2% off-set proof stress (proof stress) and Vickers hardness observed at low Ga contents (0.25-2.00%). On the other hand, the elongation significantly decreased with the addition of Ga at all contents used in this study. The tensile strength, proof stress and Vickers hardness of the 35Ag-30Pd-20Au-15Cu alloys containing 0.25-2.00% Ga were in the range of 809-957 MPa, 669-857 MPa and 260-301 MPa, respectively. These values are similar to those of Co-Cr alloys, suggesting that 0.25-2.00% Ga alloys can be used for denture frameworks, clasps and connectors. (+info)
Application of a glass fiber-reinforced composite material to clasps--the effects of immersion and repeated loading.
(3/18)
The aim of this study was to investigate the effects of water immersion and repeated loading on the mechanical properties of a glass fiber-reinforced composite (FRC) material. Measurements for three-point flexural tests were made at three different temperatures and cross-head speeds, while measurements for fatigue tests were made under three different loads in air or water at 37 degrees C after each cycle. The flexural strength and elastic modulus of the immersed specimens were significantly lower than those of the dry specimens at the same cross-head speed and temperature. On the whole, the values were inferior to those of metal. The deflection increased significantly as the load increased, but there were no significant differences between the values of dry and immersed specimens. With increasing load and number of cycles, the permanent deformation of both specimens increased significantly. The permanent deformation was similar to that of Co-Cr alloy. Based on the results of this study, it is recommended that more effort be devoted to exploring and devising shapes that would render FRC clasp arms with mechanical and physical properties that differ favorably from those of metal. (+info)
Stress analysis of clasps made of glass fiber-reinforced composite material using three-dimensional finite element method: influence of shape in cross and longitudinal sections of circumferential clasp arms.
(4/18)
The purpose of this study was to investigate the effects of different cross-sectional shapes and presence of taper on stress distribution in clasp arms made of glass fiber-reinforced composite (FRC) material. Stress analysis of clasps was performed under a constant load (5 N) using a three-dimensional finite element method with due consideration to the anisotropy of unidirectional FRC material. Results were then compared with clasp arms made of metal- an isotropic material. It was found that both FRC clasps and metal clasps yielded similar results. As for the displacement of clasp arms with a basic cross-sectional shape under a load of 5 N, the amount of displacement showed that FRC clasps provided sufficient retentive force required for clinical application. (+info)
Retention force of T-bar clasps for titanium and cobalt-chromium removable partial dentures.
(5/18)
Effect of bending on the mechanical properties of gold wrought-wire clasps: a non-linear finite element analysis.
(7/18)
The purpose of this study was to assess the effect of bending of dental gold alloy wires on the mechanical characteristics of wrought-wire clasps. We conducted a simulation of large deformation in straight wires by means of non-linear finite element (FE) analysis. A bending force increased the principal tensile stress on the outer surface of the bending corner and the compressive stress on the inner surface of the bending corner to their maximum values. After unloading with springback, a residual tensile stress was produced on the inner surface. A gold alloy wire clasp exhibited a relatively greater flexibility with small permanent deformation after the clasp tip deflection as compared to previously reported data for Co-Cr wires; this suggests that it is suitable for periodontally compromised teeth. Wire clasps are more susceptible to failure as compared to straight wrought wires because of the residual stress produced during the bending process. (+info)
Effect of mold temperature on the mechanical durability of titanium casting clasp model.
(8/18)
Titanium is widely used in dental applications. This study investigated the effects of casting conditions on the mechanical characteristics of cast titanium, with a special focus on mold temperature. As such, the mechanical characteristics of specimens prepared at various mold temperatures of 23, 200, 400, 600 and 800 degrees C were compared. On tensile strength, a significant decrease was observed at mold temperatures above 400 degrees C as well as an increase in the scattering of the measured values at higher mold temperatures. On the durability of cast titanium which was assessed by simulating the actual clasp movement during cyclic flexural test, it was found to decrease as the mold temperature increased. When compared with Type 4 dental gold alloy, titanium which was cast at room temperature exhibited equivalent or better durability. Based on the results of this study, it is recommended to perform casting at lower mold temperatures in order to produce highly fatigue-proof cast titanium clasps. (+info)