In this journal (Vol.19 No.1 in 1975), we reported on removable partial dentures with conecrown-telescope (C. C. R. D.'s). Follow-up of these cases was carried out 19-20 years after denture insertion. Four patients had 5 prostheses that functioned well. Four of 15 abutments were extracted because of root fracture and secondary caries. Due to denture breakage, 4 prostheses were refabricated, using original retainers (Konuskrone). To obtain favorable prognosis, we need to be concerned about the following considerations. 1. The abutment teeth are selected sound remaining teeth. 2. The suitable check-up and treatment are carried out for the denture movement. 3. The strength of fabrications is firmly established by the structural design of the denture. 4. It is essential to maintain good hygiene habits of oral cavity and denture.
Partial denture obturator with conus crown restored remaining teeth (canine and two premolars) served as postoperative maxillary defect which was classified into Aramany's Class I category. Impression of denture bearing area, including defect periphery, was made by the dynamic impression technique to obtain the maximum support. Bilateral occlusal contact was applied on the defect side and canine guided occlusion (disclusion) was provided on the opposite side to prevent rotation of the obturator during lateral excursion. The stability of the obturator prosthesis depends upon good retention of the conus crown. The obturator prosthesis could preserve remaining teeth and tissue, and restored adequate functions, speech, deglutition, and mastication. The results of improvement were as follows; 1. An oral seal was confirmed by the standard lung function test and monitoring image during swallowing sequence by X-ray video fluorography. It created a good function of speech and swallowing. 2. The stability, retention and support of the obturator prosthesis applied by conus crowns, dynamic impression technique and occlusion could decrease the rotation and mobility of the obturator. It provided adequate mastication. 3. Conus crowns cause not only direct retention but also secondary splinting effects on remaining teeth. Mobility of remaining teeth decreased after wearing a prosthesis in spite of a large defect of denture bearing capacity.
The influence of nonworking side's contacts was investigated in vivo in the eccentric position to the response of the jaw closing muscles during clenching. This study was performed by changing the degree of clenching and the distance between upper and lower canines on the working side. Furthermore, the distance between the lower second molar and a splint inserted on the upper molars was changed using various thicknesses of metal plates. The thickness of the plate which allowed the first occlusal contact on the nonworking side during clenching was called D0. At 100% maximum voluntary clenching (MVC) and a distance of 1.5 mm between the upper and lower canines on the working side, the nonworking side's temporal muscle activity at D0 showed the lowest value. At the edge-to-edge contact of the working side's canines, the same results were obtained. However, at 50% MVC and the distance of 1.5 mm between the upper and lower canines, the activity, when no contact on the nonworking side was allowed, showed the lowest value. These findings indicate that nonworking side's contacts like that at D0 protect physiologically the temporomandibular joint from hypermobility during clenching in the eccentric position, and this protection is related with the degree of clenching.
The purpose of this study was to investigate stress distribution in bone around bone-bonded and bone-adapted titanium cylindrical implants with various countersink angles using 2-dimensional finite element analysis. In the bone-adapted model, the slip element was used at the interface between the bone and implant. The following results were obtained. 1. Stresses were observed at the compact bone around the countersink in both bone-bonded and boneadapted implants. Nevertheless, stress concentration differed in the location. In bone-bonded implants, the stress concentration was observed at the upper most part of the compact bone around the countersink of the implants. Whereas, in bone-adapted implants it was observed at the compact bone around the edge of the countersink. 2. In bone-bonded implants, various countersink angles scarcely affected the stress value in bone. But in bone-adapted implants, the 75 degrees of countersink angle reduced the stress value utmost.
The purpose of this study was to analyze movements of the incisor point during chewing (chewing movements) of the patients with craniomandibular disorders (CMD) and healthy subjects, to classify the parameters of chewing movements and to clarify the relationship between classified parameters and CMD. Chewing movements of right and left sides were recorded with Sirognathograph Analysing System. The number of analyzed sides was 80 in 40 healthy subjects and 171 in 95 patients with CMD (90 in 50 patients with anterior disk displacement with reduction (Click), 42 in 25 patients with anterior disk displacement without reduction (Lock), and 39 in 20 patients with myofascial pain dysfunction syndrome (MPDS)). The 68 parameters of chewing movements were divided into 10 categories by a principal component analysis. The results were as follows: 1. Distinctive parameters between healthy subjects and patients with CMD were irregularity of opening and closing path near the occluding point, unstable opening and closing speed, disturbance of rhythm, unstable occluding point and limitation of lateral closing path. 2. Characteristics of chewing movements were delay of maximum opening and closing velocity and small degree of its occurring point in patients with Lock, and long opening and closing phase in patients with MPDS.
Denture plaque is an important factor in the pathogenesis of denture stomatitis. Candida speciescan be found in high frequency in denture plaque related to denture stomatitis. This study was carried out to investigate the antifungal activity of denture cleansers with berberine hydrochloride, which has antifungal activity, againstC. albicans, C. tropicalis, and C. glabrata. The broth dilution method was used to test the fungicidal activity of the cleansers. S 16 showed more than 99% cidal activity at 60 minutes exposure inC. albicans.S 16 was tested for the effects on Candida removal. S 16 had removed adhered fungal cells from acrylic resin surfaces approximately 64-89%.
This study was designed to investigate the effects of pulp and different matters in pulp chambers such as core, posts, and artificial coloring cements on teeth color. Namely, we chromatically measured crowns and roots in 20 newly extracted maxillary anterior teeth. Using a spectroradiometer under the following 4 different conditions:(1) free from artificial matters (2) inserting red wax (3) inserting metal core (12% Pd alloy)(4) setting metal core with opaque cement. Further, extracted teeth were compared with natural teeth for crowns. The results were as follows: 1. Extracted teeth have higher values of L*, Hab°, and lower a* than natural teeth. It is supposed that these results depend on the lack of hemoglobin in soft tissues. 2. Inserting metal core and red wax caused the decrease in L*. And red wax influenced in a* and Hab°.As for color difference, metal core greatly influenced both crowns and roots. 3. Effects of opaque cement appears more clearly in crowns than in roots. 4. These results revealed that, in both crowns and roots, teeth coloring had affected the pulp and matters in pulp chambers because of its transparency. Therefore, it is important to consider the pulp's condition when treating an esthetic problem.
To develop porcelain-facing alloys for conical double-crown telescopic prosthesis, several alloys were manufactured by adding 0.5%, 1.0%, 1.5% Zr to a Co-Cr alloy containing 2% titanium. Physical and mechanical properties and the bond strength of these alloys were examined to investigate the optimal amount. The following results were obtained: 1. Oxidation at the melting point of the alloy were reduced by the addition of Zr. 2. The value of Vickers hardness were reduced by the addition of Zr. 3. The value of contraverse strength and elastic constant were reduced by the addition of Zr. 4. The bond strength was increased by the addition of 0.5% Zr, and the optical value was obtained at 1, 050° under reduced pressure. 5. The optimal additional amount was 0.5% for porcelain-facing alloys for conical double-crown telescopic prosthesis. 6. The bond strength was increased by the addition of Zr, because the form of Cr2Co3and CoO at the oxide layer were restrained.
A quantitative analysis for TMJ sounds was carried out to clarify the clinical, diagnostic reliability of TMJ. The proper recording point and sampling frequency for the spectral analysis of TMJ sounds were studied. Each recording point was compared by the differentiation between the silence group and the noise group, and the frequency-spectrum of each sound was observed. The results were as follows: 1. As for the total energy, the difference was largest at 20 mm anterior inferior of the arbitrary hinge axis point in both the groups and was smallest at the arbitrary hinge axis point. The largest difference was at 7 mm posterior superior of the arbitrary hinge axis point, where a condylar movement analyzing system was easy to attached. 2. The capability for differentiation at each recording point varied depending on other evaluations. 3. It was necessary to apply over 7 k Hz of sampling frequency to observe small frequency components.
The dimensional changes of denture base of maxillary removable partial denture (Kennedy class I division 1) following polymerization were measured by using the three-dimensional measurement system for 4 weeks. The maxillary partial dentures processed by three kinds of denture base resin (heat-cured, pour-type, microwave-cured) were compared. All dentures shrank toward the center of the denture immediately after deflasking. These dentures showed linear shrinkage of 0.38% to 0.54% for the heat-cured, 0.23% to 0.52% for the pour-type, and 0.34% to 0.40% for the microwave-cured resins. After deflasking up to 4 weeks, the heat-cured dentures, except alveolar groove, gradually expanded; the pour-type dentures gradually expanded and reached the original model size, but the buccal flange continued to shrink toward mucosal surface of denture; the microwave-cured dentures gradually expanded.
The objective of this study was to examine the effect of occlusal support on the whole body equilibrium function in edentulous patients during static and dynamic events. Ten edentulous and dentate adult volunteers over 50 years old were asked to stand on an equilibrium function testing machine (Equitest: Neurocom USA). The system consists of a computer controlled movable platform with five pressure sensors and movable surrounding walls with some scenery. By changing the location and angle of the platform with scenery angulation, equilibrium and balance adjustment function were evaluated during static and dynamic events. Our results suggested that occlusal support with prosthetic appliances in edentulous patients might be helpful for the static equilibrium function.
This study was designed to investigate the influence of ocular shift and closing eyelid on the path of human habitual jaw movement with (TC) or without (NC) tooth contact. Twenty-five normal subjects were selected. The path of incisal movement was measured with Mandibular Kinesiograph (Myo-tronics, K-6), and the average path was calculated with a signal processor (NEC San-ei, 7 T 17). The results were as follows: 1. Ocular shift caused contralateral deviation of jaw movement from the control path under both light and dark conditions. 2. Closing unilateral eyelid caused significant ipsilateral deviation of jaw movement. Under dark condition, the mean values of deviation increased. Values on NC were larger than those on TC. 3. Closing bilateral eyelids caused no significant change in jaw movement from the control path.
The adhesiveness between the resin cements and the dentin surfaces was studied. As the resin cement, Bistite resin cement (BI), Super-Bond D Liner plus (SB), and Imperva bond dual cement (ID) were used. The dentin surface was polished with # 1000 SiC paper and then pretreated with etching agents, conditioner or primers of each resin cement not only according to the manufacture's instruction but also by the various kinds of the combination of etching agents, conditioner and primers. After these pretreatments, each resin cement was applied to the pretreated dentin surface. The test samples were immersed in 37°C water for one day, and the shear bond strengths were measured by a universal testing machine at a cross head speed of 2mm/min. The effectiveness of original self-etching dentin primer, 10 T-2 (10% tannic acid-2% FeCl3-35% HEMA aqueous solution) on the adhesion of resin cements to the dentin was also examined by the method described above. The results were as follows; 1. When BI was used, the pretreatment to dentin with conditioner and primer had the highest mean bond strength of 6.0 MPa, and that with the combination of 10 T-2 and photo-bond had the mean value of 6.1 MPa. 2. When SB was used, the pretreatment to dentin with etching and primer had the highest mean value of 10.9 MPa, and pretreatment to dentin with the combination of 10 T-2 and photo-bond had the mean value of 9.2 MPa, which caused the cohesive failure of dentin. 3. When ID was used, the pretreatment to dentin with etching agent, primer and bonding agent had the highest mean value of 7.9 MPa, and that with the combination of 10 T-2 and photo-bond had the mean value of 8.9 MPa. 4. The pretreatment of dentin with the conditioner of DI, etching agents of SB or ID removed the smear layer, but 10 T-2 pretreatment preserved the smear layer on the dentin.
A new antimicrobial material, zeolite (Zeomic®), was added at concentrations of 0 (control), 1, 2, 3, 4 and 5% in the powder phase to a heat cured acrylic resin, and the effects of addition of this agent on the mechanical strength of acrylics and on the growth of Candida albicans were examined. Both mean tensile and bending strength decreased depending upon the dose of zeolite added, though, as compared with the control, 4% and 5% added specimens exhibited significantly low strength in both tests. These results suggest that the preferable concentration of addition of zeolite acrylic would be less than 4%, taking into account of mechanical strength. On the other hand, zeolite-combined acrylics, except 1%-specimen, showed significant fungicidal effects. Further, all zeolite-combined specimens showed significant growth inhibition of Candida albicans. These results, suggest the possibility of clinical use of this material, and that the optimal concentration of addition of zeolite is around 2%, in consideration of both mechanical properties and antifungal effects.
For the purpose of reinforcement to the castable ceramics (OCC), fusing of ceramics to the sintered zirconium body was examined. The state of bonding for each specimen was observed with the unaided eye and the bond strength was measured by push-out test. As a result, crack development of OCC was caused by the difference of the thermal expansion coefficient of sintered zirconium bodies and the recrystallization of OCC. When porcelain was coated to the sintered zirconium body before busing of ceramics to it, the bonding strength was increasing, but the diffusion of specified elements were not found around the bonding interface of the sintered zirconium body.
At present, immersion in anantiseptic solution is the most common method of sterilizing an impression. However, it is known that immersion in an antiseptic solution would have adverse effects on the accuracy and surface property of the impression. Thus it has been demanded that a sterilization method having no adverse effects on impressions be devised. In this study, the effects of impression materials on ultraviolet irradiation and those of ultraviolet irradiation on impressionswere evaluated using ultraviolet rays ith a wave length of 253.7 nm. The results were as follows: 1. Irradiation at 7, 000μW/cm2 showed a more stable sterilization ffect than that at 1, 000 μ/W/cm2. 2. In ultraviolet irradiation at 1, 000μW/cm2 for 30 seconds, viable cells of the indicator strain were significantly less on the silicone ubber impression than on the alginate impression (p<0.01). 3. In ultraviolet irradiation at 7, 000μW/cm2 for 5, 10, 15 and 20 seconds, viable cells of the indicator strain were significantly less on the silicone rubber impression than on the alginate impression (p<0.01). 4. On observation of the impression surface after ultraviolet irradiation under scanning electron microscopy, the number of cells of the indicator strain were found to have decreased.
The purpose of this study was to investigate the influence of the anterior palatal form on speech. The subjects used were 36 male and 14 female dentitions, which were native Japanese speakers. The palate of each subject was impressed and the study cast was made. Each palatal form was examined and classified. Parameters involve the palatal form ; WD-index, IM-angle, A-angle, PL 1, PL2, and PL 3 were measured. The acoustic characteristics during /s/ production of subjects were analyzed with a digital acoustic analysis system. The first and second peak frequencies and consonant duration of /s/, the first, second and third formant frequencies of following vowels were measured. The relation between the palatal form and the acoustic characteristic of /s/ sound was discussed. The following results were obtatined. 1. Palatal form was classified into three types: Type 1 represents a rounded square arch with a gentle anterior palatal slope and the maximumpalatal depth was low. Type 2 represents a rounded square arch with a sharp slope and the maximum depth was great. Type 3 represents a narrow paraboloid or V-shaped arch with a sharp slope and the maximum depth was great. 2. WD-index, IM-angle and PL 3 in male subjects were useful values to classify three palatal types, and WD-index, A-angle and PL 2 in female subjects. 3. The palatal form had little influence on the acoustic characteristics of /s/ sound.
With an increase in the aged population, the number of elderlypatients seeking dental treatment is increasing. Therefore, it has become increasingly important to evaluate the relation between oral and general conditions of elderly patients. Of patients seen for dental treatment at geriatric hospital in Yachiyo City, Chiba Prefecture from June 1993 to July 1994, three groups of patients, inpatients aged above 65 years, patients accommodated in the Health Service Institute for the Aged and outpatients, were chosen to comparatively investigate their oral conditions. The results were as follows: 1. The oral condition was best in the group of outpatients and worst in the group of patients accom- modated in the Health Service Institute. 2. Since only a few molars were found remaining in the mandible in all threegroups, the number of patients requiring replacement with a free-end denture seemed high. 3. Since mandibular cuspids were mostly preserved in all three groups, these were considered to serve effectively as abutment teeth.