[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Purpose: We investigated how various frame materials, porcelain firing temperature and heating rate influenced the fracture toughness of the veneer porcelain used for zirconia all-ceramic restorations.
Methods: The fracture toughness was evaluated according to the ISO 15732 standard. The veneer porcelain for the zirconia all-ceramic restorations was fired on 0.4- and 0.8-mm-thick zirconia frames (ZAC) at moderate firing schedules, and fired on ZAC(0.4) at low, moderate, and high temperatures and at slow, moderate, and fast heating rates. Veneer porcelain fired on metal frames for porcelain-fused-to-metal (PFM) ceramic restorations was also evaluated as a control. The data were analyzed using 2-way ANOVA and the Tukey-Kramer HSD test (ɑ = 0.05).
Results:
The effects of the ZAC and PFM frame thicknesses and the firing temperature on the fracture toughness of the veneer porcelain were not significantly different. The fracture toughness of the sample heated fast on the ZAC was significantly lower than that of the samples heated at slow and moderate rates (p < 0.05). The fracture toughness of the sample heated slowly on the PFM was significantly higher than that of the samples heated at moderate and fast rates (p < 0.05).
Conclusions: The results suggest that the effects of the ZAC frame thickness and firing temperature on the fracture toughness of the veneer porcelain were not significantly different; however, the heating rate significantly influenced the fracture toughness.

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Purpose: To examine the effect of lateral head tilt on mandibular position, we measured the positions of the condylar and incisal points in three dimensions after lateral tilting of the head. The relationship between head tilt angle and mandibular position was subsequently investigated.
Methods: Thirty healthy adults with normal occlusion and suffering no stomatognathic dysfunction were examined. An anterior jig was attached to the maxilla and a paraocclusal clutch was attached to the mandible. Left and right condylar and incisal points were measured by the Win Jaw System^® at the following head tilt angles: 0°, 5°, 10°, 15°, 20°, 25°, and 30° (toward either side). Anteroposterior, horizontal, and vertical shifts of the condylar and incisal points from the corresponding reference positions were calculated at each tilt angle. Differences in head tilt angle were analyzed by one-way repeated measures ANOVA and Bonferroni’s method.
Results: In the condylar points on the side of the flexed neck, anteroposterior, horizontal, and vertical shifts were not significantly different. Lateral head tilt caused significant anteroposterior and vertical shifts in the condylar points on the side of the extended neck, and the shift increased in line with head tilt angle of 10º or more. Lateral head tilt caused significant anteroposterior and horizontal shift in the incisal points, and the shift increased in line with head tilt angle of 10º or more.
Conclusions: Lateral head tilt causes a shift in the mandibular position which increases with increasing head tilt angle.

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Purpose: The purpose of this study was to investigate the effect of loss of posterior occlusal support on the stabilization of posture stance disturbed by electrical stimulation.
Methods: Experiments were performed on 15 young healthy adults (aged 26.3±3.1; mean ± SD). The subjects stood on a force plate with eyes open and in the upright position. The common peroneal nerve of the right leg was stimulated randomly by supramaximal percutaneous electrical stimulation once every 8 to 10 s to contract their peroneus longus and tibialis anterior muscles involuntarily. We analyzed the total length, anterior/posterior and lateral amplitude of body sway under the following three occlusal conditions: mandibular rest position (Control), maximum voluntary teeth clenching with splint covering only anterior teeth (AntSP-CL), and maximum voluntary teeth clenching (CL).
Results: The total length (p<0.01) and anterior/posterior amplitude of body sway (p<0.05) under the CL condition were significantly lower than those under the Control condition. The total length of body sway and anterior/posterior amplitude under the AntSP-CL condition did not show statistical differences compared with the Control and CL (one-way ANOVA, Bonferroni correction method).
Conclusions: It is suggested that occlusal supports of molar teeth would contribute to postural adaptation caused by teeth clenching to a novel environment. Accordingly, we consider that they would play an important role in not only masticatory function but also motor function.

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Patient: The patient (76 years old, male) visited the hospital with the chief complaint of masticatory impediment due to mandibular severe ridge resorption. A cobalt chrome double metal structure denture with physiological form using piezography and functional occlusal surface form using the functionally generated path technique were delivered.
Discussion: Higher denture stability could be obtained because the denture teeth arrangement and cameo surface were located within their individual piezographic spaces. It was thought that not only were denture adjustment times decreased, but also that the dentures contributed to the long-term denture stability of the occlusion by functional occlusion.
Conclusion: Complete dentures with functional occlusion and physiological denture form were delivered for mandibular severe ridge resorption which was effective for the long-term stability of masticatory function.

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Patient: The patient was a 54-years old male. The chief complaint was masticatory problems due to discomfort from the lower right fixed bridge and a missing of left molar region. The lower right side fixed partial denture was removed because of hopeless abutment teeth. The bilateral free-end partially edentulous jaw was occlusally reconsructed by implant prosthodontic treatment.
Discussion: The occlusal support provided by the implant enabled good masticatory function. More than three years after delivery of the prosthesis, the implants and remaining teeth were kept up by a maintenance program and a hygiene control at 4 months interval.
Conclusion: An appropriately positioned implant, good design of the superstructure, and maintenance after installation of the prosthesis resulted in the recovery of mastication and effective occlusal support in comparison with the removable partial denture.

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