In prosthesis for patients with temporomandibular disorders, centric relation should be determined after the clinician has restored the physiological condition by controlling the load placed on the joint due to the treatment denture. An 82-year-old female edentulous patient with a history of temporomandibular disorder was admitted to fabricate new dentures. Determining the mandibular position, the gothic arch, tapping point, bilateral manipulation, light chin point guidance, and light guide tapping position were distinguished and displayed on the same coordinates using a digital gothic arch tracer, whereby centric relation was determined. Reproducibility of the centric relation was evaluated by standard deviation for 20 continuous guidances, the averages for each guidance were distinguished and displayed, and the positional relationship of the mandible was evaluated to verify the determined centric relation.
The tracing apparatus was kept and stored for periodic observation of the horizontal mandibular position before and after fitting new dentures at the same coordinate. It was possible to observe correlating, approximating and focusing of the tapping point to the gothic arch apex. Occlusal stabilization suggested that the determined mandibular position was accurate, whereby the system offered a different method for judging the treatment results.

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This study was conducted to clarify functional differentiation among the anterior temporal muscle (AT), the middle temporal muscle (MT), and the posterior temporal muscle (PT) for producing bite force with various direction and magnitude. Six male subjects were asked to bite arbitrarily and the direction and magnitude were recorded using a three-dimensional bite-force-transducer. Concurrently, electromyogram of muscles was done. As a result, each muscle had a proper range of bite force direction with its range wider in AT and narrower in PT. Each muscle had a specific direction shown by highest EMG activity, anteriorly in AT and posteriorly in PT. In AT, the activity was higher than the others with anterior bite force direction. In MT, it was higher than the other two when the direction of bite force was posterior. In PT, the proportional activity to the combined muscle activity increased as the bite force direction changed to posterior, with an opposite tendency in AT. Changing the direction of bite force laterally had no effect on the proportion of muscle activity. The findings indicated a functional partitioning of the temporal muscle into at least three parts. The direction of muscle fibers seems to dictate the characteristics of muscle function.

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The purpose of this study was to investigate the effects of tongue space reduction on the mandibular positioning at the mandibular rest position. The three-dimensional positioning of the mandibular incisor tooth point and its variable range were determined at the mandibular rest position using three different tongue space reducing devices. The results were as follows:
1. The vertical and anteroposterior components of mandibular positioning range at the mandibular rest position were increased by tongue space reduction.
2. The lateral component of mandibular positioning range at the rest position was not significantly affected by hemilateral reduction of the tongue space.

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The purpose of this study was to investigate flow characteristics of four commercial polyaddition-type silicone impression materials (Regular Type) before mixing.
Base and catalyst pastes were filler and polymer separated by a centrifugal separator with benzene for component analysis. As a result, weight fraction of filler was 39-55% and the chief ingredient was silica. The main polymer of base and catalyst pastes was polydimethylsiloxane. Especially, base polymer included hydrogen polydimethylsiloxane which was a crosslinking agent. The molecular weight (Mw) of these polymer was mostly about 40, 000-70, 000.
The viscosities of these pastes before mixing were measured by a cone-plate viscometer. Both base and catalyst pastes demonstrated pseudoplastic behavior which is the non-Newton flow. Particularly, base pastes showed thixotropic properties because of their clear hysteresis curves and time dependency on the viscosity. One of the base pastes had a yield value.
The inorganic filler significantly affected on flow characteristics of impression materials. The results suggested a means to manufacture impression materials with superior characteristics for working.

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Mechanical properties and corrosion resistance for dental castings with Ti-15%Zr-4%Nb-4%Ta alloy without V and Al were evaluated by tensile test at room temperature, micro Vickers hardness test, anodic polarization test in 1% lactic acid and artificial saliva solutions. Trial fabrication of metal plates for complete and partial dentures, crown, and bridge with the new titanium alloy was conducted.
The 0.2%proof strength and ultimate tensile strength for the dental cast were 739±53 MPa and 915±51MPa, respectively. Total elongation and reduction of area were 7±2%and 8±6%, respectively, and Young's modulus was 86±8GPa. The results were satisfactory compared to the Japanese Industrial Standard values for various dental casting alloys. However, micro Vickers hardness on the casting surface was higher than that in the center. Anodic polarization curves of the dental casting showed corrosion resistance similar to that of annealed Ti-15%Zr-4%Nb-4%Ta alloy. Current density in the high-potential region (over 2 V vs. SCE) was lower than that of Ti-6%A1-4%V ELI (Extra Low Interstitial) alloy. Moreover, the Ti-15%Zr-4%Nb-4%Ta alloy was found to be applicable for making a dental prosthesis using casting conditions similar to those of commercial pure titanium (CP Ti) casting. The findings indicated that the Ti-15%Zr-4%Nb-4%Ta alloy could be successfully used as a dental casting alloy.

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The purpose of the present study was to reinforce the strength of the bonding between dental precious metal alloys and adhesive heat-curing type resin.
Three kinds of precious metal alloys were treated with three kinds of surface treatment methods, high temperature oxidation with pickling by acid solution and SnO electro-plating method, high temperature oxidation with pickling by acid solution, and only SnO electro-plating method. Adhesive heat-curing type resin containing 4-META was cured on the treated alloy surfaces. The adhesiveness was evaluated by a shear bonding strength test and a pigment percolation test after thermal cycling.
The results were as follows:
1. The porous structure on the alloy surface formed internal oxidation particles after pickling effectively reinforced the mechanical retention between alloys and resin.
2. The SnO electro-plating effectively increased the chemical adhesion between alloys and resin.
3. The method with internal oxidation and subsequent SnO electro-plating superiorly increased the durability and adhesiveness of alloys and resin.

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CerAdapt (Nobel Biocare), the ceramic abutment made from densely sinterd high-purity aluminium oxide, was developed for single unit implant restoration with good esthetics and biocompatibility. However, there have been few clinical reports in the literature about surface treatment and bond strength of CerAdapt.
The purpose of this study was to evaluate influence of various surface treatments on CerAdapt for shear bond strength of IPS Empress (IVOCLAR) cemented with Variolink II (VIVADENT). The surfaces of CerAdapt were treated by sandblasting with aluminium oxide for 10 seconds, 37% phosphoric acid for 60 seconds and 5% hydrofluoric acid for 60 or 120 seconds. As a control, the surface was not treated. Shear bond test was carried out with Instron 5567 (Instron Japan) at a cross-head speed of 1.0 mm/min.
The results were as follows:
1. The highest bond strength was obtained with sandblasting (20.8±1.85 MPa).
2. The treatment with 5%hydrofluoric acid for 120 seconds (11.4±1.14 MPa) significantly decreased the bond strength of control (13.6±1.62 MPa).

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Bond strength between abrasion-resistant plastic teeth and photo-cured composite resin for crown was investigated to evaluate the effect of eight kinds of surface treatment. The shear bond strength of abrasion-resistant plastic teeth to photo-cured composite resin was measured using a universal testing machine at a crosshead speed of 1 mm/min before and after thermocycling.
The result were as follows:
1. The shear bond strength of water saturated abrasion-resistant plastic teeth to photo-cured composite resin was significantly less than that of dried abrasion-resistant plastic teeth.
2. The surface treatment with silane coupling agent, bonding agent, and methylene chloride did not enhance the shear bond strength between abrasion-resistant plastic teeth and photo-cured composite resin.
3. The air abrasive treatment showed significant higher shear bond strength than no treatment.
4. The air abrasive treatment plus bonding agent showed the greatest bond strength and durability of all treatments.
It was concluded that the air abrasive treatment was effective for strengthening the shear bond strength of abrasion-resistant plastic teeth to photo-cured composite resin. All surface treatments without air abrasive treatment did not enhance their shear bond strength in service.

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