Biomedical subjects

T Nokubi

Publications and source records attributed to T Nokubi.

At least 19 recordsLinked to original sources

PubMed1992

Clinical application of a newly developed surveying system for designing and fabricating removable partial dentures.

In this paper, some problems in commercially available surveying systems were discussed, and a clinical technique for designing and fabricating clasps by using an improved 'Digital Surveyor' and a computer system were presented. This system has the advantages as follows: (1) morphological factors on abutment teeth could be measured and evaluated using the improved 'Digital Surveyor' and its accessories set, (2) clasps providing with proper mechanical properties according to various conditions in the mouth could be designed and fabricated precisely and easily. It became clear that conventional surveying methods involved empirical rules should be re-examined and replaced by the more rational surveying method like this system.

Computer-Aided Design↗

PubMed1992

Three dimensional shape measurement system for residual ridges.

It is very important for design and construction of complete dentures to evaluate the condition of residual ridges of edentulous patients objectively and precisely. The authors have been developing a shape measurement system for residual ridges. In this study, the outline of the system is described and the accuracy of the system is evaluated. The system consists of a high precision laser displacement meter, a working table and its controller, and a personal computer. The working table, on which a plaster model is placed, can move until the end of the moving range at a speed of 0.7 mm/sec. The height of the plaster model was measured intermittently with a frequency of 7 points/sec. To determine the accuracy of this system, experimental plaster models, which simulated the simplified shape of residual ridge, were measured and analyzed. The measurement error was 2.5%, which seemed to be highly accurate. The accuracy of the measurement decreased with the darkness of the color of the plaster model.

Alveolar Bone Loss↗

PubMed1992

Effects of heat treatment on mechanical properties of base metal wrought wire clasps.

The purpose of this study is to determine the effects of heat treatment and soldering on the change of shape and mechanical properties of cobalt-chromium-nickel alloy wrought wire clasps. The change of distance between the tips of the clasp arm was measured and mechanical properties were examined using the bending test. The following results were obtained. 1) By heat treatment at 500-700 degrees C for 10 minutes, bending rigidity and deflection at the proportional limit of the clasp arm increased significantly (p < 0.01), while permanent deformation after the bending test decreased considerably (p < 0.01). Concerning the deformation of clasp arms by heating, the distance between clasp tips increased remarkably above 500 degrees C (p < 0.01). 2) These mechanical properties of clasp arms were improved both by electric resistance soldering with silver solder and by heat treatment at 500 degrees C for 10 minutes after soldering. From these results, it was concluded that electric resistance soldering and adequate heat treatment were very effective to improve the mechanical properties of the clasp arm, especially to increase the deflection at the proportional limit and reduce the permanent deformation.

Chemical Phenomena↗

PubMed1992

Influence of dimensional factors and heat treatment on permanent deformation of wrought wire clasps.

The purpose of this study is to examine the fatigue profiles of wrought wire clasps during the clinical use. Cobalt-chromium-nickel alloy wires were bent into circular beams, which dimensions and fabrication methods were similar to the clinical cases. Deflections of 0.5 mm in a normal direction were applied 10,000 times to the tips of clasp arm and permanent deformations were measured. The following results were obtained. 1) The clasp arms with larger cross sectional diameter, shorter length and smaller radius of curvature showed larger amounts of permanent deformation. 2) The amounts of permanent deformation of the clasp arm remarkably decreased by electric resistance soldering and decreased further more by heat treatment at 500 degrees C for 10 minutes after soldering regardless of the number of deflection. From the results of this study, it was concluded that dimensional factors and heat treatment influenced the permanent deformation of the wrought wire clasps remarkably. Therefore, considering these factors, wrought wire clasps could be designed to reduce permanent deformation.

Chemical Phenomena↗

PubMed1990

[Teeth arrangement of anterior artificial teeth. 1. Age and teeth exposure].

In selecting and arranging anterior artificial teeth for edentulous patients, it is necessary to consider their sex, personality, age and other factors. The relation of upper and lower lip lines to incisal edge has been one of the standards for the selection and the arrangement of anterior artificial teeth. The purpose of this report was to establish and to evaluate decision bases for the selection and arrangement. We recorded and measured the exposure rate of anterior natural teeth (48 men, 46 women) during function, such as smile, pronunciation, by means of the image analysis. Following results were obtained. 1. As the age of patients increased, upper anterior teeth appeared less than lower's. 2. Differences in exposure ratio between upper and lower teeth were found more remarkable in smiling rather than in pronunciation.

Adult↗

PubMed1990

[Clinical studies on crevicular fluid of abutment tooth. 3. Effect of tannin-fluoride preparation on gingival health].

It was examined, in this study, whether the tannin-fluoride preparation (HY preparation), which might have a caries reductive, plaque inhibiting and astringent action, could reduce the incidence of gingival inflammation around abutment teeth for removable partial dentures. Zinc oxide eugenol cement mixed with HY preparation filled in the cavity prepared in the resin base facing the abutment tooth. Crevicular fluid (Periotron unit: GCF), gingival index (GI), plaque index (PII), probing depth and caries activity around the abutment tooth were measured during 12 months. The following results were obtained: 1. GCF decreased at 1 month later and showed low values at 2, 3, 6 and 12 months. 2. The percentage of low GI value showed an increasing tendency during the experimental period. 3. There was slight variation in PII and probing depth during the experimental period. 4. Caries activity showed a decreasing tendency. These results indicate that the tannin-fluoride preparation reduces not only caries activity but also gingival inflammation around abutment tooth.

Dental Abutments↗

PubMed1990

Clinical application of electric resistance welding and soldering methods to removable partial dentures.

The joining procedure for uniting metal structures is very important in the construction of removable partial dentures. However, it has several restricted problems in joining wrought wire clasps to rests or major connectors. For example, the base metal wires made of chromium-cobalt alloy are subject to changes in their mechanical properties caused by heating, and damage to acrylic resin materials (denture base and artificial teeth) occurs in the repair of removable partial dentures by using the torch soldering method. In this paper, in order to resolve these problems, an electric resistance welding machine was applied to attach wrought wire components to a removable partial denture framework. This welding machine was used to attach metal structures temporarily to each other, and to solder the welded joint with hard solder. Consequently, some problems of the conventional torch soldering method were improved by using the electric resistance welding and soldering methods. It was suggested that the clinical application of the electric welding and soldering methods was very useful in the construction of removable partial dentures.

Aged↗

PubMed1990

[Removable partial dentures applied by electric welding and soldering methods].

The joining procedure for uniting metal structures is very important in the dental clinic, and various kinds of metal joining methods have been performed for clinical application. The conventional torch soldering method using a blow torch has been generally adopted. However, it has several clinical problems, especially in the construction of removable partial dentures. The base metal wires made of a chromium-cobalt alloy are subject to changes in their mechanical properties caused by heating, when wrought wire clasps are joined to rests or frameworks. In addition to the flexibility of wrought wire clasps, damage to acrylic resin denture bases and acrylic resin teeth occurs in the repair of removable partial dentures. In this paper, the electric resistance welding and soldering methods were applied to attach wrought wire components to a removable partial denture framework to resolve the problems of the torch soldering method. As a result, it is suggested that these electric resistance welding and soldering methods have the following advantages, as compared with the conventional torch soldering method. 1. When using this electric resistance welding method, it is possible to fix metals temporarily to each other more securely and strongly than the conventional temporary fixation methods using sticky wax or acrylic resin. 2. The electric resistance soldering method does not require any heat insulation or a partition as the torch soldering method does, because the soldered area is only heated partially. 3. In the case of soldering electrically wrought wire clasps to metal structures such as rests and connectors, there is no fear of of overheating a wide area of wires.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromium Alloys↗

PubMed1990

Clasping system with rotational path of insertion. 2. Relation between mesio-distal distance of edentulous space and retentive force.

The rotational path of insertion differs substantially from the conventional path or perpendicular path of insertion. With a rotational path, one segment of the partial denture is seated first, then the remainder of it is rotated into position. One segment of this system is the rigid retentive component with a long occlusal rest and the other is the conventional clasp. This study examined the influence of mesio-distal distance of the edentulous space, the point of the displacing force, the undercut of rigid retentive component and the inclination of the abutment tooth on the retention of this system. The following results were obtained: 1) Retention of the denture was the lowest when a displacing force was applied at the conventional clasp part under the conditions of mesio-distal distances with edentulous spaces of 10, 20 and 30 mm, respectively. 3) Retention showed a tendency to decrease progressively as the proximal undercut on the rigid retentive component was changed to 2.0, 1.5, 1.0 and 0.5 mm, respectively. The values of the decreasing ratio of retentive forces were almost the same regardless of the mesio-distal distance of the edentulous space. 4) Retention of the denture was improved when a tilted tooth was used as an abutment tooth on the rigid retentive component side.

Dental Clasps↗

PubMed1990

Problems of denture wearers regarding denture cleaning.

With the increase of elderly population, the number of patients who need removable prostheses increase rapidly. Denture wearers have different problems from non-denture wearers in terms of maintaining oral health. In this study, we attempted to find out specific difficulties of denture wearers with questionnaires regarding social life problems as well as oral hygiene problems. Our results indicated that most of the denture wearers considered the cleaning of denture was essential to maintain their oral health, though methods they employed showed a great deal of difference. Also denture wearers felt difficulties in cleaning their dentures when they went out.

Denture Cleansers↗

PubMed1990

Mouth guard and occlusal force distribution.

Mouth guards are effective to prevent traumatic injury in maxillofacial region during sports activities. This study was designed to find out the influence of wearing mouth guards on occlusal force distribution using an occlusal force transducer system (T-Scan system). Occlusal forces were more evenly distributed when mouth guards were in place comparing with natural dentition and with wearing conventional full arch bite planes.

Adult↗

PubMed1990

[Clinical application of T-Scan System. 2. Evaluation of soft mouth guards].

Soft mouth guards are effective to prevent traumatic injury in the maxillofacial region. In this study, we tried to find out the effect of soft mouth guards on the distribution and the magnitude of occlusal force using the T-Scan system. Ten adult subjects volunteered to exert maximum biting force wearing three different types of soft mouth guards. With the limitation of the T-scan system reported in our previous article, following results were obtained. 1) Occlusal forces were more evenly distributed with soft mouth guards than without them. 2) Softer mouth guards were more effective for occlusal force distribution. 3) Since occlusal relationship between mouth guards and mandibular arch could alter the distribution pattern a great deal, occlusion of mouth guards should be examined more carefully.

Adult↗

PubMed1990

[Mouth guard and occlusal force distribution].

Mouth guards are effective to prevent traumatic injury in maxillofacial region during sports activities. This study was conducted to investigate the influence of wearing mouth guards on occlusal force distribution with the T-scan system. With comparison to the value of average occlusal force level per occlusal point (OFL) on natural dentition and wearing conventional full arch bite plane, following results were obtained. 1) Difference of OFL within the same dental arch became smaller when mouth guards were on. 2) Statistically significant difference in OFL was not found between two mouth guards with different hardness. 3) During three seconds clenching, OFL in posterior region changed great deal at the initiation but stayed at about the same level after that.

Bite Force↗

PubMed1989

[Effect of bite plane on electromyographic activity of masticatory muscles. 1. Muscle activity during tapping movement].

The purpose of this study is to examine the influence of the insertion of bite plane on masticatory muscle activity during tapping movement, and find out useful parameters for examination and diagnosis of stomatognathic dysfunction. The subjects in this study were twenty normal subjects with intact dentition and no signs of mandibular dysfunction as the control group, and twelve subjects with unilateral temporomandibular joint pain during jaw opening or closing movement as the patient group. Electromyographic activity in the bilateral anterior temporal and masseter muscles and mandibular movement using the Mandibular Kinesiograph were recorded simultaneously during tapping movement. The usefulness of the 61 items used in this study was evaluated. The results were summarized as follows: 1. In the patient group, a significant correlation between the jaw opening degree during tapping movement and the maximal jaw opening one without pain was recognized. 2. The total muscle activity in the patient group decreased significantly by the insertion of the bite plane. 3. Many subjects of the patient group showed a significant difference between the right and left activity of each muscle. 4. A significant difference between the two groups was found in the duration of muscle activity before and after Silent period, those coefficients of variation and the difference between those durations of the right and left muscle activity. This study suggests that the above factors are very useful parameters for examination and diagnosis of temporomandibular joint dysfunction.

Humans↗

PubMed1989

[Simulation of bone resorption in denture patients using finite element analysis. 1. Application of optimization method].

The purpose of this study was to simulate the process of bone resorption under removable denture bases. Two dimensional finite element models were prepared for the frontal section of a maxillary complete denture with its supporting mucosa and bone in the first molar region. Simulations were performed with the optimization program which could proportionally move the nodal points according to the stress level difference between the actual and the reference stress level. By exerting loads on occlusal table of the model, the bone resorption progressed in the similar manner to reported clinical observations. The location and magnitude of the resorption were highly related to the location and direction of the loads.

Alveolar Bone Loss↗

PubMed1989

[Inference engines of expert systems for designing removable partial dentures].

The expert system for designing removable partial dentures has a great potentiality for clinical and educational use. The system sorts out several solutions for clinical problems with the aid of logic and data bases stored in the memory bank. The most important part of this system is the inference engine. Production system and frame system are often used as the inference engine. The purpose of this report was to compare different types of inference engine in practical situations. Following conclusion were obtained. 1) Since each type of inference engine has its own advantages and disadvantages, one has to select most suitable one for the purpose of the system. 2) One must select the inference engine type which will help potential user's understanding.

Denture Design↗

PubMed1989

[Clinical application of T-scan System. 1. Sensitivity and reproducibility and its application].

Analyzing occlusal contacts is significant for establishing the occlusal scheme as well as for the diagnosis on dysfunction of stomatognathic system. We tested a new occlusal contact analyzing device (T-Scan: Tekscan Inc. Boston, U.S.A.) for its sensitivity and reproducibility in relation to its clinical application. Following results were obtained. 1) As the modeling of dental arch of this system was not always correct, much care should be needed for identifying the contact location. 2) The minimum amount of load needed for displaying each five step occlusal force increased linear fashion (step 1: 250 g and step 5: 1750 g) when the sensor was vertically pressed on the intersection of force sensitive line. The minimum amount of force changed with the loading condition such as area and direction. Distortion of the sensor could lead the measurement error. 3) Since the time measurement data by this system were shorter than actual length of time and were measured over about 250 g load, light and early occlusal contacts could not be detected.

Dental Arch↗

PubMed1989

[Construction of data base for designing removable partial dentures. 1. Retainer and abutment selection].

In designing removable partial dentures (R.P.D.) for edentulous patients, variety of designs are selected with considering the condition of residual teeth, alveolar ridge, occlusion and other factors. We have been trying to develop the computer consultation system for designing R.P.D. (so called "expert system") to rationalize the processes of R.P.D. design. In developing and expanding this system, the construction and enlargement of the rulebase and database are indispensable. In this report, we analyzed R.P.D. designs in student's clinic ('83-'85), in order to find the logic for design (rulebase) and to construct databases. Following results were obtained. 1) Wire clasps were most frequently used in Kennedy classification I, II in maxilla. Double clasps were mostly used in Kennedy class I, II in mandible. Akers' clasps were mostly used in class III. 2) Canine, first and second premolar were more frequently selected for abutment than other teeth.

Denture Design↗