Tomoji Matsuura

Properties of test metal ceramic titanium alloys

Four test alloys were prepared using a high frequency centrifugal casting machine and a ceramic crucible for the development of titanium bonding alloys that can be cast in the ordinary atmosphere. Of these alloys, 10.06% Ti, 78.79% Ni, 9.02% Pd, 1.77% Sn and 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir could be cast by the conventional high frequency centrifugal method; however, 89.18% Ti, 8.75% Ni, 1.03% Pd, 0.28% Sn and 89.81% Ti, 8.15% Ni, 1.01% Pd, 0.18% Sn, 0.67% Ir could be cast only by the argon are melting method. The alloys 10.06% Ti, 78.95% Ni, 9.02% Pd, 1.77% Sn and 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir showed excellent physical and mechanical properties and bonding strengths, surpassing those of the commercial alloys TPW and Unimetal. Concerning the elution of component elements, the amounts of titanium eluted from these alloys were far smaller than those from pure titanium or a Ti-6Al-4V alloy, and nickel elution, which has become an issue in relation to metal allergy, was almost nil in contrast to Unimetal (Ni-Cr alloy). The alloy 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir showed properties that indicated its favorable use as an alloy for the bonding of dental porcelain.

Firing Behavior of Titanium and Titanium Alloy.

To use titanium alloys with excellent properties as prosthetic materials, the amount of the oxide film produced after firing and its physical properties, which have major effects on their binding with porcelain, were studied in pure titanium and Ti-6Al-4V alloy.The following results were obtained:1. The amount of the oxide film was related to conditions of firing. It was greater as the rate of the increase in the temperature was slower, the duration of firing was longer, and the final firing temperature was higher.2. The color of the oxide film was also related to conditions of firing. Pure titanium became whiter, and Ti-6Al-4V alloy became browner, as the amount of film produced was greater.3. The hardness was similarly related to the amount of film produced. The materials were harder as the film was thicker.4. At 1, 000°C the expansion rate of Ti-6Al-4V alloy was about twice that of pure titanium. The coefficient of expansion of the alloy was also slightly greater at 200-700°C. Pure titanium has a transition point near 885°C at which the crystalline structure changes from α-phase to β-phase, but this transition point was not observed in Ti-6Al-4V alloy.

Studies on photopolymerized crown and bridge resin. Part 1. Physical properties of Dentacolor.

Light activated composite resin, Dentacolor, was examined on chemical composition, polymerization characteristics and bonding to a metal and adhesive resin cement in order to confirm the dental application of it. For bonding, the surface of metal, Au-Ag-Pd alloy, was treated as follows; a) retention beads added, b) retention beads+alumina sand blasting+tin electroplated+adhesive resin cement (Panavia EX), c) alumina sand blasting+tin electroplated+adhe sive resin cement.The results were summarized as follows;1) Dentacolor consists of 31 wt% of urethane dimethacrylate with a small amount of other methacrylate (unknown) and 69 wt% of composite filler (inorganic phase 47 wt%).2) The surface hardness of the cured product of Dentacolor was little affected by a position of a specimen in a photo-irradiation apparatus (Dentacolor XS) and a shade of Dentacolor, however, conversion of polymerization, which was presumed by its hardness of a vertical plane, was relatively high in the center of a flask.3) Compared with heat cured composite resin (Isosit), the surface hardness, wear resistance and solubility in water of Dentacolor were nearly equal, but the bending strength and water sorption were slightly lower than those of Isosit.4) The bonding strength of Dentacolor when another layer was put on the surface of its cured product was comparatively high (170 kg/cm2) and its value was little affected by the irradiation time to the first layer.5) The bonding strength of Dentacolor to the metal was increased with the surface treatment of the metal except for the method a)(170-180 kg/cm2).6) After thermal cycling, a good improvement of marginal sealing was shown by the surface treatment of the metal except for the method a)

A comparison of mandibular position by four different guiding methods; Gothic arch tracing, habitual closure, voluntary tapping and myo-monitor centric.

The purpose of this study was to compare and evaluate the relative reproducibility and equality as well as jaw relationships produced by four jaw guiding methods; the gothic arch tracing, the voluntary tapping, the myomonitor centric and to occlude warm wax bite rim by light habitual closure. Four patients were selected whose remaining teeth had already lost the maximum intercuspation. The intraoral tracer was fixed on upper complete denture base and lower removable partial denture in three cases. Only in one dentulous case needed complete occlusal rehabilitation, the appliance was fixed on transfer coping crowns.The mandibular position guided by each methods was measured to the nearest 0.1mm in laterally and anteroposteriorly (x and y components). The accuracy of this experiment was estimated at 0.22mm (±2σ) or 0.34 mm (±3σ). This error was derive from width of tracing line, area of tapping point, mobility of denture base and mounting on articulator. Within the limits of this investigation, it is concluded that;1. Each guiding methods determined different mandibular position in case 1, 2 and 4. But in case 3, they terminated in the same mandibular position.2. The gothic arch tracing produced the least variable and the voluntary, tapping the most variable. The habitual closure tended toward eccentric position laterally. The myo-monitor centric produced more variable than the gothic arch tracing but less than the habitual closure.3. The estimated region of apex point was 0.57mm in laterally and 0.45mm in anteroposteriorly, the myo-monitor centric showed 0.62mm in laterally and 0.76mm in anteroposteriorly, the habitual closure determined 0.97 mm in laterally and 0.96mm in anteroposteriorly and the voluntary tapping produced 0.95mm in laterally and 1.59 mm in anteroposteriorly in an average of rejection ellipse (α=0.05).4. In an average of mandibular positon in anteroposteriorly, the gothic arch apex was the most retruded. The distance between apex point and the habitual closure was 0.4mm, the myo-centric was 0.7mm and the voluntary tapping was 0.9mm anterior.5. An average distance between apex point and mean points of each methods produced more consistent mandibular position that ranged within 0.15mm in laterally.