Kenji Notani

Influence of Retainers and Occlusal Contact of Lateral Eccentric Relation on Load Distribution of Abutment Teeth and Displacement of Denture. Part 2. The Case of 3 Remaining Teeth.

For the stability of removable partial dentures, both the occlusal relationship and the design of the denture are important.A mandibular simulation model with three remaining teeth (Nos. 22, 27, and 31 or Nos. 22, 27 and 31; universal tooth numbering system) was used in this study.Occlusal contact in the lateral eccentric jaw relation was varied, and the stress distribution of abutment teeth and displacement of the denture base were examined.The results were as follows:The occlusal contact in the lateral eccentric jaw relation rather than kind of retainer seemed to influence the stress distribution of abutment teeth and displacement of the denture base.In the case of bilateral balanced occlusion, there was no obvious difference between an Akers clasp and a cone-telescopic crown.Denture stability could be maintained by group functioned occlusion as well as by bilateral balanced occlusion, depending on the pattern of the remaining teeth.The results suggested that in the case of an asymmetrical pattern of the remaining teeth, occlusal contact in the right and left lateral eccentric jaw relation must be changed.

Complete Maxillary Denture Mobility Related to Posterior Tooth Position

Although a lot of artificial posterior tooth positioning techniques have been proposed, correlation between complete denture stability and posterior tooth position during mastication has not yet been clarified.This study was conducted to analyze the behavior of complete maxillary dentures that have two posterior tooth positions by the simulation method. Three-dimensional mobility of these dentures was measured during biting two sizes of simulated foods on centric and eccentric positions. One of two artificial posterior teeth arrangements was based on the alveolar crest (A-denture) and the other was in a neutral zone of muscular activity (N-denture).The results were as follows:1. The working side point of two complete maxillary dentures moved downward, forward, and outward when they were loaded on one side.2. The mobility of complete maxillary dentures was changed by posterior tooth position, simulated food size, mandibular position, and tooth contact on the balancing side.3. When biting thick food, there was no tooth contact on the balancing side. In this condition, the mobility of A-denture was less than that of N-denture.4. When biting thin food, there was tooth contact on the balancing side. This contact limited the mobility of two dentures. In this condition, however, the mobility of N-denture was less than that of A-denture.

Studies on the Displacement of Abutments, Changing Angles, Heights and Shapes of Konus-telescope Inner Crowns

It is clinically well known that the secondary splinting is as effective as the primary splinting, using the konus-telescope crown. The purpose of this study is to investigate and to evaluate the displacement of the konus-telescope outer crown under the lateral loads of them, changing angles, heights and shapes of konus-telescope inner crowns.The results were as follows:1. The horizontal and vertical displacement of the outer crown were influenced by not so much the angle as the height of inner crown.2. As for inner crown shape, the displacement of c.s.c. type outer crown was larger than that of konus-type.

The two step method of fabricating maxillofacial prosthesis with dynamic impressions and fluid resins.

Maxillary obturator had many problems in its sealing, retention and stability.This report introduced our methods to fabricate them by taking dynamic impressions and utilizing fluid resins.The fablication techniques were as follows.1. First, making the first prosthesis that were complete dentures without the obturate parts.2. By the use of them, we took dynamic impressions of maxillary defects.3. After getting the master casts contained the first prothesis, we finished the obturate parts made of the fluid resins “Palapress” over them.The advantages of the prosthesis were simple to construct, light in weight, good fitness, and no complainments.

The Influence of Retention Holes in Porcelain Teeth on Retentive Force and Impact Strength

The purpose of this investigation is to determine what are the diatoric forms of the posterior porcelain tooth possessing both sufficient toughness for impact and retentiveness to denture materials.In this article, an experiment with 10 types 27 sets of home-made artificial porcelain teeth (molars and premolars) consists of(1) the observation of the ratio of the diatoric forms area (SII) to the ridge lap surfaces of teeth (SI), the ratio SII/SI.(2) In the retention hole on the cross-sectional area of the porcelain tooth, the measurements of the height, the width, the undercut wells of them and the angle of intersection between the axis of crown and that of the retention hole.(3) tensile test.(4) repetitive impact test in distilled water at 37±1°C.The specimens for the both test were made by planting a porcelain tooth in a resin-block along the axis of crown and then were immersed in distilled water at 18°±2°C.Through these experiments, the following results were obtained.The ratio SII/SI was not constant in all types and molds. Preferably there was a tendency that the larger the crowns became, the smaller ratio SII/SI became. The height, the width and the undercut wells had similarly no relation. But the angle of inclination was closely resemble every molars and premolars regardless of upper or low teeth, and the premolars were higher than the molars.Conserning with the tensile strength, each porcelain tooth was as follow: 5, 8.5±2.1kg; 5, 8.6±2.5kg; 6, 11.4±2.7kg ;6, 11.6±2.8kg; on each mean, which indicated that the molars were always higher than the premolars although there was no constant relation with every mold. The tensile strength was affected by the diatoric designs, upon which not only the depth of the undercut wells but the height, the width, and the angle of inclination had seemingly great influence.After the test, fractures of the porcelain were left on the resin-blocks in the case of the specimens with high strength.As to the impact test, about the half of specimens were satisfactory. The rest of them were broken preceding 4000 strokes. Among them, the relation could be found in the molars that the number of the upper teeth broken was more than the low, but in the premolars could not.An important characteristics of this test was the effect of the air vent holes in mesio and distal surface of the porcelain teeth.The porcelain teeth with them generally had lower impact strength, and their crack (by the impact) always went through the air vent holes, which had frequently been seen in a clinic.Therefore the question was raised whether they were necessary.