The Journal of the Kyushu Dental Society

Various occlusion theories have been previously reported, particularly in the field of denture occlusion. As a result, it has been difficult to derive a theoretical basis for evidence accumulation related to denture occlusion. In the field of temporomandibular disorders, occlusion has been long a controversial issue. One hindrance in accumulating the evidence related to occlusion is the methodological difficulty of realizing occlusal concepts. In the present paper, logical analysis and a way to cope with the creation of future denture occlusal concepts are discussed and a method of realization in cast prosthetics, a double-casting method, is reported as well.

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Titanium has been widely used for dental implant owing to its superior biocompatibility and corrosion resistance. However, metal restorations involving the superstructure of the implant, bridge, crown and inlay are usually fabricated from alloys other than titanium. It is well known that electrochemical corrosion may be caused by galvanic reaction between the different alloys in contact with each other in an electrolyte, resulting in preferential corrosion of the electrochemically base metal. It is therefore recommended that dental restorations be designed not to bring different alloy systems in contact within an individual mouth, in order to avoid galvanic reaction. On the other hand, the corrosion behaviors of different alloy systems are still unclear when they coexist without being in contact. The present study examined the potential electrochemical corrosions of pure titanium and other dental alloys coexisting in contact or without contact in 1.0% lactic acid aqueous solution for 36 weeks. Little or no changes were seen in dissolutions of Au-Pt-Pd ceramo-metal alloy and titanium when they were immersed together, regardless of the contact. The amount of released Cu from the Au-Ag-Cu alloy tended to increase slightly in the presence of titanium, and the amount of Ti also increased. When the Au-Ag-Pd alloy and titanium coexisted, the release of Ag significantly decreased and Cu and Ti increased. There were no significant differences whether they were in contact or not. Marked dissolutions of Ag, Zn, Sn and In were found in the case of the Ag-Zn-Sn-In alloy specimen even if immersed alone. When titanium and the alloy were in contact, the releases of Ag and Ti were restrained while In was released to a greater degree. The same tendencies were found even when they were not in contact. With the Co-Cr alloy, Co was most released and its release was significantly accelerated in the presence of titanium. The release of Ti tended to show an increase both in the cases of contact and non-contact. In conclusion, any combination of titanium and dental alloys except for the ceramo-metal noble alloy exhibited galvanic corrosion, even if they were not in contact. These results suggest that titanium implants should be designed with due regard to total biocompatibility to prevent the possibility of increased release of allergic or toxic constituents from existing alloy restorations in the mouth.

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Actinobacillus actinomycetemcomitans is a facultative intracellular bacterium capable of inducing apoptosis in murine macrophages. In this study, we investigated the caspase cascade in apoptotic cell death of A. actinomycetemcomitans-infected macrophages. Flowcytometric analysis revealed that inhibitors of caspase-3, -8 and -9 significantly inhibited the apoptotic cell death of infected macrophages. We obtained evidence that infection with A. actinomycetemcomitans induced the activation of the caspase-8 and -9 and the executioner caspase-3 by immunoblot analysis. The activation of caspases induced the cleavage of poly (ADP-ribose) polymerase (PARP). These cleavages were observed within 12 to 18 h after the infection with A. actinomycetemcomitans. The PARP cleavage resulting from activation of the apoptotic pathways was prevented by the caspase-3, -8 and -9 inhibitors. These findings indicate that the pathway of A. actinomycetemcomitans-induced apoptosis involves the activation of caspases-3, -8 and -9, and that the activation of caspase-3 plays an important role in the cleavage of PARP during apoptosis in A. actinomycetemcomitans-infected macrophages.

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Over 10 years have passed since magnetic attachments have been applied clinically, and the problems of retention, magnetic field, and corrosion have gradually been solved. Recently, these magnetic attachments have been applied as retentive structures for various removable partial dentures. In this case, we made use of this attachment as an intracoronal and extracoronal attachment. The intracoronal and extracoronal magnetic attachments were placed on the patient's lower removable partial denture to improve esthetic appearance. A lingual plate was attached as the major connector to deal with her complaint concerning tongue discomfort. Her problems were solved by these measures.

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