PubMed · 6573252
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H Schwickerath, U W Jahn. 1983. [Flowability of casting materials].. https://pubmed.ncbi.nlm.nih.gov/6573252/
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OBJECTIVES: A reaction layer forms on cast titanium surfaces due to the reaction of the molten titanium with the investment material. Such a layer prevents strong adhesion between titanium and porcelain. This study characterized the effects of surface modifications on cast titanium surfaces and titanium-ceramic adhesion. METHODS: ASTM grade II CP titanium was cast into an MgO-based mold. Castings were devested by sandblasting with alumina particles, and subjected to surface modification by immersion in one of the following solutions: (1) 35% HNO3-5% HF at room temperature for 1min; (2) 50% NaOH-10% CuSO4 x 5H2O at 105 degreesC for 10min; (3) the NaOH-CuSO4 solution followed by the HNO3-HF solution; (4) 50% NaOH-10% NaSO4 at 105 degreesC for 10 min; (5) the NaOH-NaSO4 solution followed by the HNO3-HF solution; and (6) 50% NaOH solution at 105 degreesC for 10min. Surfaces only sandblasted with alumina were used as controls. Specimen surfaces were characterized by XRD and SEM/EDS, and hardness-depth profiles were determined. All specimens were sandblasted with 110 microm alumina particles before porcelain firing. An ultra-low-fusing porcelain (Vita Titankeramik) was fused on the titanium surfaces. The titanium-ceramic adhesion was characterized by a biaxial flexure test, and area fraction of adherent porcelain (AFAP) was determined by X-ray spectroscopy. RESULTS: EDS analyses revealed a substantial amount (13-17 wt%) of Al on the control, and specimens modified with Methods 2, 4, and 6. XRD revealed residual stress in the titanium surfaces and corundum on the control, and Methods 2, 4, and 6 specimens. A new Ti(Cu, Al)2 phase was identified on the titanium surfaces modified by immersion in 50% NaOH-10% CuSO4 x 5H2O aqueous solution. Reduced residual stress was observed on Method 1, 3, and 5 specimens. No corundum peaks were detected on these specimens. Compared to the control, significantly lower (P < 0.05) hardness values were found for Methods 1-3 and Method 5 specimens at 20 microm below the surfaces and for Method 1-5 specimens at 50 microm below the surfaces. Significantly higher (P < 0.05) AFAP values were found for surfaces modified with Methods 2-6 compared to the control and Method 1, and no significant differences were found among Methods 1-6, and between control and Method 1. SIGNIFICANCE: Based on the results from the present study, porcelain adherence to cast CP titanium can be improved by the caustic baths used in the study.
OBJECTIVES: This study examined the influence of six handling techniques on the strength of four phosphate-bonded investment (PBI) materials. The size and distribution of pores produced by the handling techniques were investigated and their effect on room temperature strength determined. METHODS: Specimens were tested for strength using four point bend at a cross-head speed of 1 mm min-1. The fracture surface of randomly selected specimens was viewed through a light microscope to determine the pore size. A three-parameter Weibull distribution was used to describe strength giving values of Weibull modulus and characteristic strength. RESULTS: The handling technique that produced the smallest pore size resulted in the highest strength. Significant differences in strength (90% confidence level) were found between most handling techniques. The reduction of pore size by mechanical spatulation and setting under pressure was found to be the most effective method of increasing the strength of PBI. SIGNIFICANCE: Previous studies have related handling technique to the inclusion of air bubbles in dental investments but have not reported any consequent effect on strength. PBI materials are used in production of a range of dental appliances with a variety of different material forming processes and are required to withstand the loads applied without fracture or distortion to ensure accuracy of fit of these prostheses. The use of a handling technique that reduces pore size can significantly increase the strength of PBIs, thereby decreasing the possibility of die fracture or degradation.
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