コーヌスクローネ支台歯の挙動に関する 3 次元的解析 : 遊離端義歯のデザインの相違による影響

Abstract

Since the importance of the rigid connection between abutment teeth and retainer was advocated for supporting removable partial denture, the conical crown (Konuskrone) - retained dentures have stood high in the clinical evaluation. However, not a few problems involving falling down of inner crown, increase in abutment tooth mobility and breakage of denture have been reported. The present study was scheduled to experimentally investigate the characteristic behaviors of the abutment teeth for Konuskrone retainers when they were altered in number and location in the mandibular unilateral distal extension removable partial denture. Six types of unilateral distal extension partial dentures were constructed ; three of them were of unilateral designs having one, two and three abutment teeth on the same side of the denture base, respectively, and the other three of bilateral designs having additional one abutment tooth on the opposite side in each of the above unilateral designs. The tooth movement was measured in horizontal, frontal and sagittal planes by means of mandibular kinesiography (MKG) and laser displacement sensors on a Kennedy class II simulation model. The results obtained were as follows : 1. It was found that the abutment teeth movements involved not only simple tipping but also horizontal displacement and gyration of their tooth axes. 2. It was the most difficult to take countermeasures in Konuskrone to deal with the movement against the force from lingual side. 3. In the unilateral design, the primary abutment tooth movement could not be restrained by addition of one mesial abutment while one more mesial addition showed significant reduction in the movement. 4. In the case of the bilateral designs, application of only primary abutment tooth caused large displacement. Addition of one mesial abutment tooth on the denture side was effective for reducing the displacement ; however, one more mesial abutment had a tendency to rather increase the displacement. 5. In comparison of the designs having a given number of the abutment teeth, the bilateral design showed more favorable behavior than the unilateral with two abutment teeth while there was little difference in efficiency between them with three abutment teeth, against all the forces except from lingual side. No effects were found in both the two designs having two or three abutment teeth against the force from lingual side.