ABSTRACT
If impression materials could be immersed in disinfectant solutions for a longer period, then this form of disinfection would be easier to incorporate into dental preparation procedures. This study investigated the dimensional changes in stone models resulting from immersion of medium-viscosity hydrophilic addition-type silicone rubber impression material in disinfectant solutions for 30 min and 24 h. Impressions of a master die designed to simulate a full crown preparation with adjacent teeth were immersed in 2% glutaraldehyde and 0.55% ortho-phthalaldehyde solutions. The dimensional changes in the mesiodistal and buccolingual dimensions in the stone models were then measured using a three-dimensional coordinate system. It was found that the dimensional changes in the stone models caused by immersion of the impression materials were less than 15 µm. Immersion in 2% glutaraldehyde or 0.55% ortho-phthalaldehyde for 24 h was as clinically acceptable for medium-viscosity hydrophilic addition-type silicone rubber impressions as immersion for 30 min.
Subject(s)
Dental Impression Materials/chemistry , Disinfectants/chemistry , Glutaral/chemistry , Silicone Elastomers/chemistry , o-Phthalaldehyde/chemistry , Dental Impression Technique , Polyvinyls/chemistry , Resin Cements/chemistry , Silanes/chemistry , Siloxanes/chemistry , Time Factors , ViscosityABSTRACT
This study investigated the effects of immersion of addition silicone rubber impressions in disinfectant solutions on the surface porosity of the resulting stone casts. Five brands of type 2 and 3 addition silicone rubber impression materials and one brand of type 4 dental stone were used. Impressions of a master die designed to simulate an abutment tooth were immersed in disinfectant for 30 minutes. The disinfectants used were 2% glutaraldehyde solution and 0.55% ortho-phthalaldehyde solution. The surface porosities of stone casts obtained from two brands of impression materials immersed in disinfectant for 30 minutes were determined. Results suggest that impression materials immersed in disinfectant solutions need sufficient time before pouring into dental stone.
Subject(s)
Calcium Sulfate/chemistry , Dental Impression Materials/chemistry , Dental Materials/chemistry , Disinfectants/chemistry , Models, Dental , Silicone Elastomers/chemistry , Glutaral/chemistry , Humans , Immersion , Materials Testing , Polyvinyls/chemistry , Porosity , Siloxanes/chemistry , Surface Properties , Temperature , Time Factors , o-Phthalaldehyde/chemistryABSTRACT
There is a concern that long-term immersion of impressions in disinfectant solutions may cause changes in the dimensions of the resulting stone casts. This study investigated the dimensional changes in stone casts resulting from immersion of five brands of addition-type silicone rubber impressions in disinfectant solutions for 30 min and 24 h. Impressions of a master cast designed to simulate an abutment tooth were immersed in 2% glutaraldehyde and 0.55% ortho-phthalaldehyde. The diameter of the stone cast was measured using a laser scan micrometer. For four brands of impression materials, 30-min immersion in disinfectant solutions produced no dimensional changes in the stone casts. For four brands of impression materials, 24-h immersion caused a significant decrease in the stone cast dimensions.
Subject(s)
Dental Disinfectants , Dental Impression Materials , Dimensional Measurement Accuracy , Models, Dental , Silicone Elastomers , Dental Abutments , Glutaral , Hydrophobic and Hydrophilic Interactions , Immersion , Lasers , Materials Testing , Time Factors , o-PhthalaldehydeABSTRACT
Using tensile tests, this study investigated differences in the welding strength of casts of cobalt-chromium and gold alloys resulting from changes in the voltage and pulse duration in order to clarify the optimum conditions of laser irradiation for achieving favorable welding strength. Laser irradiation was performed at voltages of 150 V and 170 V with pulse durations of 4, 8, and 12 ms. For cobalt-chromium and gold alloys, it was found that a good welding strength could be achieved using a voltage of 170 V, a pulse duration of 8 ms, and a spot diameter of 0.5 mm. However, when the power density was set higher than this, defects tended to occur, suggesting the need for care when establishing welding conditions.
Subject(s)
Chromium Alloys , Gold Alloys , Lasers, Solid-State , Welding/instrumentation , Cobalt , Dental Casting Technique , Dental Stress Analysis , Electricity , Lasers , Materials Testing , Tensile StrengthABSTRACT
This study evaluated the bond strengths between experimental Ti-20Cr-1X (X=Nb, Mo, Fe, Zr) alloys and porcelain (Duceratin). The results of this bond strength testing indicated that all the Ti-20Cr-1X alloys exceeded the lower limit value in the ISO 9693 standard for the 3-point bending test (25 MPa), and were all higher than that of commercially pure titanium (c.p. Ti). The coefficient of thermal expansion (CTE) values of all Ti-20Cr-1X alloys were higher than that of c.p. Ti, and this result of a closer match between CTEs shows the fact that the Ti-20Cr-1Mo alloy had a significantly higher bond strength than both the other Ti-20Cr-1X alloys and c.p. Ti.
Subject(s)
Dental Alloys/chemistry , Dental Bonding , Dental Porcelain/chemistry , Titanium/chemistry , Chromium/chemistry , Dental Stress Analysis/instrumentation , Elastic Modulus , Humans , Iron/chemistry , Materials Testing , Metal Ceramic Alloys/chemistry , Microscopy, Electron, Scanning , Molybdenum/chemistry , Niobium/chemistry , Pliability , Spectrometry, X-Ray Emission , Stress, Mechanical , Surface Properties , Temperature , Zirconium/chemistryABSTRACT
OBJECTIVE: The hardness and microstructures of Ti-15Mo-5Zr-3Al alloy castings were investigated for application to dental cast prostheses. MATERIALS AND METHODS: Cast specimens of Ti-15Mo-5Zr-3Al alloy, Ti-6Al-7Nb alloy and CP Ti were prepared using a centrifugal-type casting machine and a magnesia-based investment material. The hardness of the cross-sections of the cast specimens were measured. The microstructure of the castings was observed using an optical microscope and was then analyzed by X-ray diffractometry. RESULTS AND CONCLUSIONS: The hardness of Ti-15Mo-5Zr-3Al alloy at the inner part of the castings was 361 Hv, while the hardnesses of Ti-6Al-7Nb alloy and CP Ti were 384 and 269 Hv, respectively. The thickness of the surface hardened layer for Ti-15Mo-5Zr-3Al alloy was thinner than those for Ti-6Al-7Nb alloy and CP Ti. The microstructure of the Ti-15Mo-5Zr-3Al alloy casting was confirmed to be ß phase.
Subject(s)
Dental Alloys/chemistry , Dental Casting Investment/chemistry , Oxides/chemistry , Titanium/chemistry , Biocompatible Materials/chemistry , Crystallization , Dental Casting Technique/instrumentation , Dental Materials/chemistry , Hardness , Humans , Materials Testing , Microscopy , Surface Properties , X-Ray DiffractionABSTRACT
In this study, wedge-shaped CP titanium castings and Ti-6Al-7Nb alloy castings were produced by three types of investment. The effects of the castings' thickness on surface reaction layer were investigated by measuring Vickers hardness, observing the microstructure, and analyzing the oxygen concentration. It was found that the thickness of the surface reaction layer was affected by the thickness of the wedge-shaped castings, and that the hardness value near the surface became lower toward the tip of the wedge-shaped CP titanium and Ti-6Al-7Nb alloy castings. The surface reaction layer of the Ti-6Al-7Nb alloy castings was thinner than that of the CP titanium castings.
