To maintain good oral conditions following prosthetic treatment, the prosthesis must be functionally harmonized with the stomatognathic system. Biting forces during functional movements apply stresses to the teeth, periodontal ligaments, mandible, and maxilla. They produce distortion in all of them. Therefore, during function, it is very important for the prosthesis to clear the physiological tooth displacement. The upper molar showed a displacement of about 100mm in a palatal and apical direction during clenching, or during the biting of articulating papers. The lower molar showed a displacement about 50mm in a lingual and apical direction during clenching, or during the biting of articulating papers.
The molar of the patient with alveolar bone resorption showed a different displacement path from that in the subjects with healthy molars.
Implants and antagonistic teeth showed different displacement paths from that of the normal tooth. Implants (lower molars) showed displacements of 37-44mm in both lingual and buccal directions during mastication. The antagonistic teeth (upper molars) showed displacements of about 100mm in the lingual direction during mastication.
If the tooth displacement path is different from the normal one, it causes any periodontal disease to worsen. Therefore, in this case, it is important to diagnose the condition of the periodontium and the degree of bone resorption accurately. After periodontal treatment, to maintain good oral conditions following prosthetic treatment, we have to provide a prosthesis with occlusal contacts that lead the tooth to a normal displacement path.

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Purpose: We investigated diagnosis of the ridge contour and ridge mucosa for treatment of the denture patient, to discuss the need for examination, examination methods, and diagnosis (treatment planning) based on examination results.
Selection of study: Necessity of examination was discussed by presenting that buccolingual ridge contour and interridge relationship between maxilla and mandible, anteroposterior inclination of edentulous ridge, and tissue displacement influence on the stability or movement of denture, and furthermore the ridge contour and the property of ridge mucosa are affected by the bone resorption. As the examination method of the ridge contour, proposing to classify stress bearing area to vertical stress bearing area and horizontal stress bearing area, a method for analyzing the vertical stress bearing area and the buccolingual center of them related to artificial tooth arrangement, and anteroposterior inclination of ridge were shown. As examination method of ridge mucosa, measuring device for hardness (elastic modulus), vibration, and tissue activity were shown.
Results: It was shown that the above-mentioned examination methods were useful in diagnosing the ridge contour and mucosa property, and the legion of mucosal disease induced by denture. It is possible to make a diagnosis (treatment planning) for the ridge contour and properties and lesion of mucosa based on objective examination results.

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Purpose: There are reports on the efficacy of an oral appliance when used for dental treatment of obstructive sleep apnea syndrome. However, the influence of wearing it during evaluation of its therapeutic effects, on the soft tissue of the middle pharynx, has not been fully studied by magnetic resonance imaging. In this study, effects of anteflexion of the head position during the imaging were investigated, as to the shape of the pharyngeal space.
Methods: Sixteen healthy adults who did not snore were studied. Magnetic resonance imaging (MRI) was taken at four different positions of the head (H₂, H₄, H₆, H₈) with 2, 4, 6, or 8 intervening acrylic plates, 1cm in thickness inserting under the occipital region. For the control position (H₀), imaging was conducted without inserting the intervening plate. To determine the shape of the pharyngeal cavity from the sagittal view, the antero-posterior length, and the areas of posterior nasal spine, the posterior uvula palatina, and the posterior lingual radix, were measured on MRI images, and ratios of the respective measurements at the positions H₂, H₄, H₆ and H₈, to that of the control position H₀, were calculated, for comparison among the positions of the head. Statistical analysis was made by repeated-measures ANOVA for the factor of head position.
Results: From the sagittal view using MRI, the differences in each antero-posterior length of the posterior nasal spine and the posterior uvula palatina were not significant among the head positions, whereas the length of the posterior lingual radix was significantly different among head positions. The lengths of the posterior lingual radix for H₆ and H₈ were significantly shorter than those for H₂ and H₄.
Conclusion: The present results indicate that the position of the head should be restricted in MRI for morphological assessments of the pharynx from mid-sagittal views.

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Purpose: This study showed a pure titanium crown, of which the adaptation accuracy is high using a CAD/CAM system (Dental Cadim), which was fabricated for this procedure. The purpose of this is to show the fit accuracy of the crown produced on the abutment tooth. The model showed several kinds of axial surface taper.
Method: The pure titanium crown inner surface fabricated by CAD/CAM systems is cemented with white silicone and pressed with 20kgf of pressure. As to the thickness of the silicone, it was measured 3 times at each and every place. The mean value was observed, and the significance test was done between tapers at each measuring place.
Results: 1. The crown fabricated from abutment tooth model of tapers of 2° and 4° greatly rised. 2. The marginal distance between crown and abutment tooth model of taper 8°(30-50μm) is smaller than taper 6°. 3. The taper 6° is the gap between the crown inner surface and abutment tooth model and it showed very large value but the taper 8° is all measuring part places of small value. The distance between crown and abutment tooth model of taper 8° has 70μm clearance.
Conclusions: To fabricate the pure titanium crown using value and method for setting CAD/CAM system (Dental Cadim) in this study it is required the abutment tooth axial surface be over taper 8°.

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Purpose: We previously reported that the mandible is in motion during intercuspation, and that the range was about 40μm antero-posteriorly and laterally. In this study, we investigated the influence of bite registration materials between the upper and lower teeth on mandibular position, and on minute movements of the mandible.
Methods: The measuring system used was a silicon optoelectric position sensitive detector (PSD: Hamamatsu Photonics K.K., Japan). Eleven volunteers (6 males and 5 females; mean age, 24.6 years) with natural dentition, without symptoms of mandibular dysfunction, participated in the study. All subjects occluded their teeth without clenching in the intercuspal position for more than 30 seconds, while sitting in an upright position. The bite registration materials were Ramitec (ESPE), EXABITE II (GC), BITE-CHECKER (GC), and Paraffin Wax (GC). All subjects occluded without bite materials as a control. Two different jaw openings (wide and narrow) were requested before occlusion or biting. Ten trials (4 materials+control, and 2 jaw openings) were randomly performed, and were repeated three times. Variations of the mandibular position in the horizontal plane were computed by a Signal Processor (7 T 17). Data obtained were statistically analyzed by ANOVA.
Results: Bite registration materials displaced the mandible anteriorly, and the mandible moved around posteriorly in 30 seconds. Paraffin wax had the largest influence on these materials. A wide jaw opening distance produced more marked anterior mandibular displacement.
Conclusion: The mandible was in motion during occlusion with the bite registration materials in the intercuspal position. We considered that the property of the materials changed the mandibular position in the intercuspal position.

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Purpose: Many reports have described post and core in devitalized teeth with large amounts of remaining tooth crown and root. However, few reports have described post and core applied to decayed teeth consisting only of tooth roots with flared canals. This study aimed to determine optimal designs for post and core with flared canals.
Materials and Methods: Eighty premolars were divided into 8 groups (10 teeth per group), and restoration was carried out according to the following post and core designs: Composite resin core with no posthole; with 0mm coronal (Group I), 1mm (II), and 2mm (III). Flared post canals; composite resin post and core (IV), with short prefabricated post (V), with long prefabricated post (VI), short cast post and core (VII), and long cast post and core (VIII). After placing metal crowns on these post and cores, load testing was performed, to record the failure load and characteristics of root fracture.
Results: Among the 8 designs, the highest failure load was observed in Group VIII. However, many of these cases also demonstrated unrestorable root fracture following failure. Although failure load was almost identical in types II-VII, the characteristics of root fracture varied. The lowest failure load was observed in Group I.
Conclusion: The results of this study suggest that post and core using resin only is the most desirable design for restoration of flared canals, as relatively high failure loads were obtained, and many cases demonstrated restorable root fracture. With regard to cast post and core, although the highest failure load was obtained, unrestorable root fracture was caused in many cases.

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In this study, 10 subjects (8 men and 2 women) with no dysfunction of the stomatognatic system were selected. All of them were from 19 to 28 years old. Mandibular positions were determined using a custom made paraocclusal clutch and a gnathohexagraph, for three-dimensional sixdegree-of-freedom measurements. Despite changes of posture, they were improved so that they constantly maintain the distance and the angle between a camera used for measurements and head for each subject. Deviations of incisal point and bilateral condylar points at muscular positions, when the back of a dental chair was inclined backward through six stages: 15, 30, 45, 60, 75, and 90 degrees, were determined, for a multiple comparison of Scheffé on deviation.
Results: Both the bilateral condylar points and the incisal point showed posterior upward deviations under the condition of backward inclination, and posterior upward deviations demonstrated a propensity to increase with increasing angles of backward inclination. Deviations of the muscular position between the sitting position and each angle of backward inclination showed significant differences, which were greater than or equal to 45 degrees at the incisal point and the left condylar point; and 60 degrees at the right condylar point.
Conclusions: From results that showed mandibular deviations occurred significantly from a backward inclined angle of 45 degrees, in comparison with the sitting position, and that deviations demonstrated a propensity to increase with increasing angles of backward inclination, it became obvious that changes of posture during dental treatment had an effect on mandibular position. Consequently, it was suggested that registration of interocclusal relation and occlusal adjustment are required to be performed with the back of a dental chair not inclined back more than 45 degrees.

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Purpose: Recently, composite denture teeth have been commonly used for denture construction, but discoloration has frequently been reported. The purpose of this study was to investigate the discoloration of composite denture teeth. Thisin vivoandin vivostudy examined laboratory procedures for denture fabrication, the oral environment, and the methods of cleaning dentures, to clarify the phenomenon of discoloration.
Methods: Four kinds of composite denture teeth were prepared and immersed in yellow colorant solution, coffee solution, and distilled water for 3, 6, and 12months, respectively. Surface roughness, Vickers hardness, and discoloration of the composite denture teeth were measured at each specified period. During thein vivoinvestigation, the color differences after delivery of the dentures were measured, and examination of saliva was carried out. In addition, 42 patients were monitored regarding their denture cleaning methods.
Results: 1. Severe discoloration was observed on the teeth immersed in the yellow colorant solution, because composite denture teeth surfaces were rougher. In the coffee solution, remarkable discoloration was found on all composite denture teeth. The composite denture teeth with smooth surfaces and great hardness tended to show little discoloration.2.In thein vivoinvestigations, discoloration of the composite denture teeth was observed in 55% of 42 cases after 6-months, and the color differences (ΔE*) were more than 2.There was a high correlation between discoloration and the methods of denture cleaning (the use of dentifrices).
Conclusions: Composite denture teeth with rougher surfaces and lower Vickers hardness tended to show discoloration. Laboratory procedures for denture fabrication might also influence discoloration. To prevent discoloration, it is necessary to improve the mechanical properties of composite denture teeth. Furthermore, instructions to patients regarding proper handling and methods of denture cleaning are very important.

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Purpose: To establish a new color order system for natural teeth based on color depth B value.
Methods: The population sample tested in this study included 500 individuals from the Boston area. It was a multigenerational population, with a multiethnic background and a broad socioeconomic range. Reflectance values of 500 upper left anterior incisors and 90 dental shade tabs were measured by the Multispectral Camera system MSC-2000, and tristimulus values X, Y, Z were calculated. Using tristimulus values, the Computer Color Searching (CCS) program selected one shade tab (CCS tab) having the smallest dE less than 3.6 between a natural tooth and shade tabs. For a natural tooth uncovered by shade tabs, Computer Color Matching (CCM) tabs were made according to CCM prescription. Color depth B values for 70 tooth tabs (54 CCS tabs and 16 CCM tabs) were calculated. Then, 70 tooth tabs were minimized according to B value.
Results: Of 500 natural teeth, 472 were covered with CCS tabs, and 28 natural teeth were covered with CCM tabs. Seventy tooth tabs having B values from -14.98 to 22.66 were minimized to 52 tabs.
Conclusions: It could be said that this color order system, consisting of 36 CCS tabs and 16 CCM tabs based on B values, would be efficient for easy and accurate visual shade matching.

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Purpose: The purpose of this study is to clarify effects of the angle of the working side lateral condylar path of articulators on canine-equivalent lateral tooth guidance of prostheses.
Materials and Methods: Models were mounted on a semi-adjustable articulator, to determine the movement path of tips of working side mandibular canines using a Gnathohexagraph. The data that changed any adjustment system were compared regarding the sagittal-, horizontal-, and frontal-plane projection angles of the movement path.
Results: The projection angle of the working side canine path on the sagittal plane became large with an increase in the angle of the non-working side lateral condylar path, and the inclination of the sagittal condylar path as the angle of working side lateral condylar path moved in the minus direction. That angle on the horizontal plane became small with an increase in the angle of the non-working side lateral condylar path as the angle of the working side lateral condylar path moved in the minus direction, but there was no effect from the inclination of the sagittal condylar path. That angle on the frontal plane became large with an increase in the angle of the non-working side lateral condylar path, and the inclination of the sagittal condylar path as the angle of the working side lateral condylar path moved in the minus direction, but when that moved in the plus direction, a specific tendency was not shown.
Conclusion: It was determined that the effect of the angle of the working side condylar path in the minus direction became large with an increase in the angle of the non-working side condylar path and the inclination of the sagittal condylar path, so it is important to adjust the angle of the working side lateral condylar path of articulators.

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Purpose: The purpose of this study was to evaluate the color change property of a new colorchangeable chewing gum applied with a new coloring reaction, to measure masticatory ability and to analyze the correlation to masticatory performance.
Methods: Eleven healthy dentate subjects volunteered to participate in this study. Subjects chewed the gum 40, 80, 120, 160, 200, 240, or 280 times. Immediately after the trials, the color of the gums was measured and transformed using the CIE-LAB coloring system. The values of L*, a*, and b* were compared between the chewing strokes. The masticatory performance was also measured, using the sieving method. The correlation between the color of the gum and masticatory performance was analyzed.
Results: The values of L*, a*, and b* were influenced by the chewing strokes (p<0.05). The values of L* and a*, and the value of b*, statistically changed until the chewing strokes reached 120 and 160 times, respectively. The values of the correlation coefficient between the values of a* and masticatory performance exceeded 0.5 points for over 80 chewing strokes, and strong correlation was found at 160 chewing strokes (γ=0.690, p>0.05).
Conclusions: It was revealed that the color of a gum applied with a new coloring reaction changed according to the increment of the chewing strokes. A strong correlation between the color change and masticatory performance was found. It was suggested that the color-changeable chewing gum applied with a new coloring reaction was useful to measure masticatory ability.

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Purpose: The purpose of the present study was to evaluate the difference for stress transfer between titanium (Ti) and hydroxyapatite (HA) implants by measuring bone marrow pressure using a catheter pressure transducer, and then to clarify the relationship between the histological and biomechanical properties.
Methods: Ti and HA implants were inserted in the tibiae of rabbits. About 10 weeks following implantation, a hole, 1mm in diameter, was drilled in the bone distal to the implant, and a fine catheter pressure transducer was placed in the bone marrow through a tube. After the abutment was connected to the implant, the top of the abutment was vertically tapped with an impulse hammer, and the acceleration signal from the hammer, and the pressure signal from the catheter pressure transducer, were examined. In addition, histological examination was performed on each implant.
Results: Maximum bone marrow pressure (BMP) with Ti and HA was 117.4±54.8mmHg and 90.3±30.6mmHg, respectively. A significant difference was observed (p<0.05). Moreover, variation of the BMP with Ti was significantly larger than that with HA (p<0.05). A negative correlation coefficient between the time of contact recorded in the impulse and BMP was found with Ti. As to histological examination of the bone structure around several implants, no significant difference was found between Ti and HA implants.
Conclusion: The results show that the stress transfer is different between Ti and HA implants, using dynamics of bone marrow pressure. Little relation was found between biomechanical properties and histological views. The present study suggests that the evaluation of osseointegration requires consideration of biomechanical properties.

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