The purpose of this study was to investigate the relationship between patients' satisfaction with and clinical examination of their complete dentures.
Twenty-five patients who received complete denture treatment at the Dental Clinic of the Niigata University School of Dentistry, between 1983 and 1992 were selected.
Patients' satisfaction with the following factors for their dentures was measured using a visual analog scale.
1. total satisfaction
2. appearance and aesthetics
3. adaptation and stability of denture base
4. occlusion
5. speech condition
6. condition of soft tissues
In clinical examination, the quality of their dentures and anatomical condition of the oral cavity were assessed.The relation between the total satisfaction, individual factors of satisfaction and clinical examination were analyzed.
The factors of patient satisfaction that changed first and the period of time on which these changes occurred after denture insertion were also investigated.
The following results were obtained.
1. A moderate correlation was found between total satisfaction and patients' satisfaction with adaptation, stability to maxillary denture base and appearance.
2. Patients who wore their dentures during sleep tended to show low total satisfaction and excessive attrition of artificial teeth and denture plaque.
3. The factors of patients' satisfaction that changed first were adaptation and stability of denture base: changes that occurred 28 to 62 months after the insertion of their dentures.

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Various new ceramics available for all-ceramic crowns have been developed recently. More esthetic and stranger materials are demanded. IPS Empress (Ivoclar AG) is developed to realize these requirements. To fabricate this material, a vacuum-pressure pressing machine was developed, and the used technique is the conventional lost wax process. Since the system was produced for dental restoration, it is important to understand dimensional change of this material to obtain restorations with a good fit. A metal die with cylindrical tooth preparation was used to determine the rate of expansion/contraction of the restorations. The dimensional change of this material was measured after pressing and firing. Ceramic ingots for the staining technique tend to expand (0.08%) after pressing, but shrink (0.12%) after first firing and (0.18%) after fifth firing. Ceramic ingots for the layering technique tend to expand (0.10%) after pressing, but shrink (0.13%) after first firing and (0.21%) after fifth firing. Furthermore, anterior IPS Empress crowns were made on epoxy resin models of abutment with clinical shape and dimensions. The crowns and abutments were embedded in epoxy resin and sectioned to allow measurement of the space between crown and abutment tooth. Precementation cross-sectional measurement of internal adaptation without spacer ranged between 14.8 and 190.6μm. After firing, the distance between crown and die increased. Based on this in vitro study, the following conclusions can be made. It is important to obtain a good fit of IPS Empress crowns, to which application of the die spacer is indispensable, and to keep the number of firing cycles as few as possible.

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The tissue reaction to four implant materials inserted transcortically and extending into the medullary canal of rat tibiae was examined, and quantitative assessment of the differences in bone reaction was made using an image processing system. The materials examined were pure titanium (Ti), anodic oxidated Ti (AO-Ti), titanium alloy (Ti-6 Al-4 V), and zirconium (Z_rO₂). Four bioinert implant materials were progressively encapsulated with bone tissues.
Analysis revealed no significant differences among the tissue reactions to Ti, AO-Ti and Ti-6 A1-4 V.The Z_rO₂ implant showed the highest bone contact rate.

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Denture tooth selection is based on the physical properties of denture teeth and the anatomic and physiologic requirements of the patients. There were two purposes for this study. One was to investigate criteria of posterior tooth selection in the fabrication of complete dentures at Tokyo Medical and Dental University. The other was to observe posterior teeth in complete dentures fabricated for 317 patients at this University Hospital from April 1992 to March 1993.
The results were as follows:
1. Of 29 dentists, 20 considered that the primary requirement for posterior denture tooth selection was high abrasion resistance. A high-strength tooth was the most popular.
2. The distribution for the combination of upper and lower posterior teeth in complete dentures was as follows: Both high-strength teeth; 71.9%, both acrylic resin teeth; 14.8%, both porcelain teeth; 6.6%, combination of porcelain and acrylic resin teeth; 5.7%, combination of high-strength and porcelain teeth; 0.9%.
3. The mesiodistal length of posterior teeth is one of the criteria for selection of posterior teeth. In commercial teeth, the smallest mesiodistal length of posterior teeth was used in 250 of 317 lower complete dentures.

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Fifty-four Donryu male rats were divided into three groups, the control group, the soft diet group (fed with powder diet containing the same components as solid one, from the 43rd week) and the molarless group (all molars were removed at 43 weeks and then fed with powder diet). At 47, 60 and 74 weeks, morphometries of mandibular bone by a handy microscope system and measurements of bone mineral density (BMD) by the image analyzing system were performed in addition to observations by light microscopy of the attachment of masseter muscle to mandible. The results obtained are as follows.
1. Occlusal-and masticatory alterations-related changes were observed in the attachment of the masseter muscle to mandible in addition to age-related changes.
2. The height of the mandibular ramus in the experimental groups were shorter than that of the control group, showing a statistical significance (p<0.01).
3. BMD at the attachment of the masseter muscle to mandible in experimental groups was less than that of control group in each weeks, showing a statistical significance (p<0.01).
4. BMD at the attachment of the masseter muscle to mandible in 60 and 74 weeks in experimental groups was less than that of the incisal alveolar bone, showing a statistical significance (p<0.05).

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To understand the causes of taste disorders on denture wearers, the following experiments were performed on 50 subjects indiscriminately, who have intact dentition. The subjects' impressions were taken, and then the experimental palatal plate was made. The gustatory responses of primary taste, which were shown by the threshold of sensation and the threshold of judgment, were examined by two sensory tests. Both tests were made with and without the palatal plate.
The first test was performed to find the direct cause of tasting difficulty due to the palatal plate covering the taste buds.
The second test was performed to find the indirect cause. Immediately upon wearing the palatal plate, it was confirmed that it is uncomfortable, the tongue space is infringed, speaking becomes difficult, the rhythm of mastication is disordered and the like. Therefore, it is expected that the stimulus of taste has a tendency to prevent transmission to the taste buds and so taste is hard to understand.
Consequently, as soon as the denture was worn, taste disorders were suspected to occur from not only the direct cause but also the indirect cause.

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Some changes take place in the abutment teeth and the denture supporting mucosa due to the insertion of a removable partial denture. The blood flow volume in the oral tissue was observed by examining the difference of both the impression pressure and the retainer with the laser doppler flowmeter at the time of passing.
The results were as follows:
1. The blood flow volume on the abutment teeth attached to gingiva tend to change in the case of high impression pressure.
2. The blood flow volume in the residual ridge mucous tend to change in the case of high impression pressure.
3. The conical telescopic denture wearer's blood flow volume on the abutment teeth attached to the gingiva decreased on day 3 and returned to the insertion-day level by day 14.
4. The conical telescopic denture wearer's blood flow volume in the residual ridge mucous increased on day 3 and returned to the insertion-day level by day 28.
5. The clasp denture wearer's blood flow volume on the abutment teeth attached to the gingiva increased after insertion and returned to the insertion-day level by day 28.
6. The clasp denture wearer's blood flow volume in the residual ridge mucous increased after insertion and returned to the insertion-day level by day 28.

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The purpose of this study was to establish a scoring method of the supporting tissues of complete denture patients by dentists. Seven elements of the supporting tissues such as shape, tissue resiliency, location of border tissue attachment of upper/lower ridges, and interridge relationship were evaluated in 317 complete denture patients with 3-4 point scales. Total clinical assessment of supporting tissues was also done with 10 point scales. The relationship between total clinical assessment of supporting tissues and 7 elements was evaluated by the quantification theory type I, known as one of the multiple factor analyses. Category scores given to 3 or 4 scale of each element were calculated. Total sum of these category scores of 7 elements in each patient was converted to an integral number distributed between 0 and 100. The converted score (supporting tissue score) was higher in male patients than in female ones (p<0.05). Positive linear correlation between the supporting tissue score and edentulous period was significant (p<0.01). It is concluded that a scoring method of supporting tissues of complete denture patients was established.

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In order to estimate the long-term influence of denture-wearing, we followed up 211 patients with the cone-crown-telescope retained dentures (CCRD's) worn for over 10 years. Of these patients, the clinical examinations were performed on 152 cases. The mean period of wearing denture was 12 years and the average age of cases was 62 years. The cases were divided into 4 groups as follows. The numbers by group were 29 for Kennedy class I, 54 for class II, 45 for class III and 24 for few remaining teeth (FR) group.
The following results were obtained.
1. In class I, II and III groups, CCRD's were generally functional, however, some oral changes were observed. But in the FR group, 30-60% were unfavorable for many items.
2. Of 614 abutments, 13.7% were extracted. The rate of discarded CCRD's occurred in 12.8% after wearing for 10 years.
3. Relining of dentures was performed frequently except for the class III group.
4. Breakage of dentures accounted for more than 90%. And severe states such as root fractures were 40% of these troubles.

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Eight basketball players were chosen as the subjects for this experiment concerning custommade mouth protectors and their effects on the muscular strength were examined by several movement tests. Muscular strength was measured in both conditions with and without mouth protectors.
The following results were obtained:
1. Leg-curl movement indicated the highest mean value of the increasing rate with 13.5%, followed by pull-down, chest-press, leg-extension and upper-back movements in this order.
2. The results showed remarkable differences between with and without mouth protectors in most subjects, that is, 7 subjects in leg-curl and pull-down movements and 6 subjects in leg-extension movements.
3. No large differences were found between with and without mouth protectors in 6 subjects in chestpress and upper-back movements.
4. Mouth protector would be more effective to the lower limbs in increasing rate of the muscular strength than to the upper limbs.

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In the previous report, the shear bond strength of dual-cured composite core resin to the dentin treated with 14 combinations of pretreatment agents, including primer and bonding agent, was measured before thermocycling. In this study, 6 combinations were selected, and the shear bond strengths after thermocycling 5, 000 and 10, 000 times were measured and compared.
The following results were obtained:
1. When dentin was treated by the conventional method with K-etchant and Clearfil photo bond, the shear bond strength increased after thermocycling in comparison with before thermocycling. After bond strength tests, interface failure between resin and dentin occurred, and SEM imaging showed some spaces between resin tags and dentinal canals.
2. When 10% NaOCL gel was used, the bond strength before thermocycling indicated almost the same value as the other pretreatment agents, but increased remarkably after thermocycling.
3. When both ED primer and Panavia 21 were used, bond strength before thermocycling showed comparatively high values, but after thermocycling decreased distinctly unless the pretreatment by 10% NaOCl gel was added.
4. The combination of ED primer and Clearfil photo bond was evaluated to be the most desirable of all combinations examined. Furthermore, SEM imaging of the dentin after bond strength tests in this combination showed no spaces between resin tags and dentinal canals.

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The basic study of the “Dental Prescale System” was performed using male persons and a plastic study model. We also studied the clinical value of appllying a thin layer of bite-silicone material (BM) to “Dental prescale” Fuji Photo Film Co.(DP). Although the data of occlusal contact area (OCA) with BM was smaller than that without, it was very easy to identify OCA when apllying BM on DP. And as there was no significant difference between the range of fluctation of OCA, the reliability of the data displayed on “Occluser” was attested in this study.

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The purpose of the present study was to make a histometrical evaluation of bone resorption under the denture base caused by lack of self-cleaning as a result of coverage by the denture base.
The experimental denture base was designed to make contact with the molar region of the palate of the rat and to transmit no occlusal force to the tissues under the denture base. The denture base was not removed throughout the experimental period. This procedure caused lack of self-cleaning, and it also caused continuous pressure to palatal tissues under the denture base by the accumulation of exfoliative horny cells, which induced bone resorption under the denture base.
Five rats of each denture wearing group and control group were sacrificed every week during the observation period of 10 weeks after the insertion of the experimental denture base. Palatal tissues were prestained with Villanueva bone stain, and then processed for undecalcified resin section for quantitative bone histomorphometry. These specimens were analyzed using a two-dimensional graphic analyzing system.
From the results of this study, it was revealed histometrically that bone resorption of palatal surface of hard palate bone tissue initiated under the denture base caused by the lack of self-claning as a result of coverage by the denture base one week after, became most active two weeks after and ceased five weeks after the insertion of the experimental denture base. But on the nasal surface of hard palate bone tissue, bone resorption was not observed.

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Histopathological initial changes in denture supporting tissues, in relation to the changes in intensity of occlusal pressure exerted through the experimental denture base, was studied. The denture base was applied to the palate of the molar region of the rat, and was installed to cover the palatal mucosa without any pressure unless occlusal force was exerted. The defined amount of occlusal pressure was transmitted to denture supporting tissue by allowing the denture base to subside the specified amount into palatal mucosa. The intensity of the occlusal pressure measured immediately after the insertion of the denture were 79.7, 31.7 and 10.7kPa. The animals were sacrificed at 2, 4, 7, 10 and 14 days after the insertion of the denture. Histopathological changes caused by the occlusal pressure were observed, and the changes in intensity of the occlusal pressure was also measured on every histopathological observation periods.
Histopathological changes of the denture supporting tissues showed dependence on the intensity of the occlusal pressure, and also showed high correlation with the subsequent gradual changes of the pressure. Compression of lamina propria mucosa, shortening of epithelial ridges, osteoclastic bone resorption, compression of epithelial tissue except for epithelial ridges and inflammatory cell infiltration in the lamina propria mucosa were observed with the elapse of time. These tissue changes came out early and became severe by increasing the occlusal pressure.

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Limitation of mouth opening, one of the symptoms of TMD, is commonly estimated by measuring the range of motion of the mandible (ROM). The values of ROM in previous studies show that ROM becomes smaller by fixation of the head while being recorded. Recently it has become obvious that the head postures, such as head extension, have a great effect on the stomatognathic function.
In this study, we investigated the influence of head extension and body posture on ROM to find out the reliability of measured ROM as a diagnostic aid in TMD and the mechanism of mouth opening; and simultaneously, we observed the EMG activity of the anterior belly of digastric muscle (Da).
The results were as follows:
1. As the head was extended, the ROM increased significantly. It is considered that the space under the mandible increased by head extension enables wider mandibular movement. This suggests that more consideration should be given to the head posture to obtain accurate ROM records of individuals.
2. The muscle activity of Da also increased significantly with head extended mouth opening. This confirms that Da plays an important role in mandibular rotation of maximum mouth opening.

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The determination of the correct vertical and horizontal mandibular position for edentulous patients is one of the most important techniques in complete denture construction.
The aim of this study was to develop a new method of interocclusal record using exchangeable screw jack apparatus to determine the vertical dimension utilizing the patient's proprioceptive sensation. Furthermore, we expect to develop a method for tracing the Gothic arch and recording the centric jaw relationship which could be easily performed in a one-treatment procedure.
The exchangeable screw jack placed on the maxillary occlusal rim makes contact with a plate fixed on the mandibular occlusal rim. The height of each screw is adjusted as follows: from 3mm lower (score 1) than the vertical dimension of the present denture (score 4) to 3mm higher (score 7) at intervals of 1mm. Using the apparatus, the upper and lower borders of the comfortable occlusal zone (COZ) are calculated from the patient's perception of mandibular position by the constant method. To understand the reproducibility of the method, each COZ of 5 edentulous patients wearing complete dentures without problem was measured on 3 or 4 different days.
There is no significant difference between COZs of different measurement days. On the other hand, the time required for measurement and recording and the patient's stress were greatly reduced with the new apparatus.

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Clinical symptoms of 326 patients having temporomandibular disorders (TMD) were surveyed. Research data were based on the clinical examinations during their first visit to the Department of Fixed Prosthodontics, Iwate Medical University Dental Hospital from 1981 to 1993.
An obvious gender difference of a male to female ratio of 1 to 3 and age distribution, showing a doublecurve peaking in the twenties and forties, were apparent among the patients.
The chief complaint of pain in the masticatory muscles tended to increase. Whereas, patients having occlusal problems involving premature contact, interference during movement to the eccentric position, or discrepancy tended to decrease.
These two distinctive points were thought to represent the yearly transitional trend of TMD patients in the northern part of the Tohoku region in Japan.

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A questionnaire was sent to 253 patients after they were treated for temporomandibular disorders (TMD) at the Department of Fixed Prosthodontics, Dental Hospital, Iwate Medical University from January of 1981 to January of 1994.
The results were as follows:
1. The questionnaire was answered by 53% of the patients.
2. Slight decreases in the degree of daily life interference, range of mouth opening, spontaneous pain, opening pain, and masticatory pain were observed.
3. The TMJ sound in 3.4% of the patients worsened, while 46.2% of the patients improved. In terms of bad habits, 1.7% patients worsened, and 21.9% patients improved.
4. Since the range in mouth opening that was evaluated subjectively did not exactly match the objective results, careful evaluation was necessary to determine the effect of the treatment.

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We are attempting to apply barrel finishing to improve the surface texture of the basal surface of the complete dentures.
The purpose of this study was to make sure the alteration of the surface texture and the cutting depth of denture base resin by barrel finishing. The board-shaped samples of denture base resin were used to investigate the alteration of the surface texture by barrel finishing, and cylindrical samples were used to measure the cutting depth. Half of the board-shaped samples were barrel finished and others were used as control samples. The upper surface of the cylindrical samples were masked by the adhesive tape except for the hole which has a diameter of 5 millimeters after being polished by the automatic polishing machine. First and second stage finishings were performed for 30 minutes respectively by the centrifugal barrel finishing apparatus.
After measuring the surface roughness (Ra, Rmax) by the surface texture measuring instrument, samples were observed under the scanning electron microscope.
The results were as follows:
1. The surface roughness significantlydecreased by barrel finishing.
2. The cutting depth by barrel finishing was 22.88±2.16μm (mean±SD).
These findings suggests that barrel finishing is useful to improve the surface texture of the basal surface.

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The lateral movements of 40 young adults were measured and the timing of the mandibular side shift was analyzed. The following results were obtained:
1. The KA angle-side shift curve was developed to analyze the timing of the mandibular side shift. The KA angle was defined as the rotation angle of the intercondylar axis for the working condyle during lateral mandibular movement.
2. The curves were classified as 5 patterns according to the timing of the side shift:
type I; a side shift occurred proportional to the KA angle (movement of the mandible).
type II; a side shift occurred in the early stage of the movement.
type III; the curve is sigmoidal, which means that a side shift occurred in the early and late stage of the movement.
type N; a side shift occurred in the last part of the movement.
type V; a side shift occurred in the middle of the movement.
And type 0, which has no significant side shift, was added to the timing.
3. Type 0-III were popular patterns in all 80 condyles, but type N and V were rare.
4. The significant side shift occurred before the middle of the lateral movements for most condyles.

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The purpose of the present study was to make a histometrical evaluation of bone formation under the denture base caused by lack of self-cleaning as a result of coverage by the denture base, utilizing a double labeling technique with bone markers.
The experimental denture base was designed to make contact with the molar region of the palate of the rat and to transmit no occlusal force to the tissues under the denture base. The denture base was not removed throughout the experimental period. This procedure caused lack of self-cleaning, and it also caused continuous pressure to palatal tissues under the denture base by the accumulation of exfoliative horny cells, which induced bone resorption and formation under the denture base.
Five rats of each denture wearing group and control group were sacrificed every week during the observation period of 10 weeks after the insertion of the experimental denture base. Palatal tissues were prestained with Villanueva bone stain, and then processed for undecalcified resin section for quantitative bone histomorphometry. These specimens were analyzed using a two-dimensional graphic analyzing system.
The following results were obtained.
1. One to three weeks after the insertion of the denture base, bone formation was suppressed or disappeared on the palatal surface of hard palate bone tissue under the denture base.
2. A transient but significant increase of bone formation was observed following bone resorption on the palatal surface of hard palate bone tissue under the denture base. And seven to ten weeks after the insertion of the denture base, bone formation was suppressed again.
3. On the nasal surface of hard palate bone tissue, increased bone formation was observed simultaneously with bone resorption on the palatal surface.

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Castable glass ceramics-porcelain jacket crown, in which castable glass ceramics are used as a coping and dental porcelain is partially or completely fired, is recommended from an aspect of esthetics. The adhesive strength between two ceramic materials is considered to be important for this jacket crown. The purposes of this study were to evaluate the adhesion of two ceramic materials under tensile load and to establish fabrication of tensile test pieces.
The following results were obtained.
1. Established method for fabricating tensile test pieces and tensile test are adequate to know the behavior of ceramic materials under a tensile load.
2. Dental porcelain used in this study showed favorable adhesion to castable glass ceramic, without detracting the inherent physical properties of castable glass ceramic.
3. The white layer, which shows the formation at the surface of castable glass ceramic after the ceraming process, does not affect the adhesion of dental porcelain to castable glass ceramic.
4. Reinforcement of the white layer is expected to be obtained by firing dental porcelain.

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