How oral health conditions influence masticatory function and health in general was reviewed. The relation of cause and effect, which the number of remaining teeth is the most contributing factor to masticatory function, has been established by many researchers. Regarding the relationship between oral health and health in general, however, scientific information is still limited. Some reports suggested that the elderly with poor oral health have high risk for physical and/or mental health problems. Another report was also found that professional care in house calls by dentists made general health of homebound patients improve. On the other hand, leading oral epidemiologists are investigating the relationship between periodontal disease and heart disease or osteoporosis by the same means. For future research, large-scale interdisciplinary cohort studies should be necessary to clarify these relations. As for oral health, there is no doubt about the importance of preventing dental caries and periodontal diseases, which are considered the main causes of tooth loss.

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In order to verify the influence of aging, tooth loss, and diet on bodily function, 216 old Donryu and Wistar male rats were divided into the following groups, the control group (fed solid diet), the soft diet group (fed powder diet containing the same components as solid one), the molarless group (all molars were removed at 45 weeks and then fed powder diet), the low calcium solid diet group (fed solid diet low in calcium and deficient in vitamin D) and the molarless low calcium diet group (all molars were removed at 45 weeks and then fed powder diet low in calcium and deficient in vitamin D). The histometric, exercise-physiologic, biochemical, and immunohistochemical analyses were performed.
The results were as follows:
1. The weight of the soft diet group at 75 weeks was higher than that of the control group at 75 weeks, showing statistical significance (p<0.01).
2. The adrenal gland weight of the Donryu rats in the molarless group 4 weeks after extraction was higher than that of the control group, showing statistical significance (p<0.01).
3. Occlusal support loss-and dietary-related changes were observed morphologically and histologically at the condyle and the attachment of the masseter muscle to mandible in addition to age-related changes.
4. The endurance performance (exhaustion time during swimming) and the value of serum indices (creatine phosphokinase and free-fatty acid) after swimming in aged rats were considerably influenced by occlusal and masticatory alteration in addition to aging.
5. The number of choline acetyltransferase (ChAT)-positive neurons in the nucleus of medial septal nucleus/nucleus diagonal of Broca of the molarless group showed decrease as compared to the control group and the soft diet group by immunohistochemical techniques. However, the number of neurons in the trigeminal motor nucleus showed no significant differences among the three groups.

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It is often said that in healthy people good health brings a long life, that people who chew well do not get dementia, and that healthy teeth are genetically determined. However, until ten years ago, there was hardly any data on the relation between occlusion and the general physical condition. By considering occlusions of the elderly from the standpoint of dentists, both eating (biting, crushing, and grinding) and speaking are important functions of the oral cavity, hence maintenance of health and general physical activity is greatly affected if either of these functions is impaired.
There are wide individual differences in people's Ikigai. Ikigai is Japanese word which includes the concepts of objective quality of life as meaningful. But as a result of aging, or of the person's surroundings, the quality of life undergoes considerable change. Though there are many factors contributing to the quality of life of the elderly, general health must be one of the principal ones. However, the quality of life gradually changes as a result of general health, aging or the aging person's surroundings, and moreover, the decline is inevitable.
Recently we measured the masticatory ability of the elderly, using a jelly we devised for objective judgement of masticatory ability (G-jelly). In this paper, our survey of masticatory ability of the elderly (65to 84 years) and its relation to their general physical condition (body weight, gripping strength, balance, bone mineral volume), which was carried out using the jelly, was reported. The results suggested that people who have good masticatory ability are those who also have a good general physical condition.

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This survey was conducted to determine the chewing ability and self-denture evaluation by elderly full denture wearers. Forty patients whose dentures were made by the same dentist were divided into four groups of 10 patients according to gender and age (65-74 years, over 75 years). A subjective evaluation of the occlusion of the denture was made by using a visual analogue scale (VAS). The masticatory ability of these subjects were scored from 0 to 100 with the table for evaluation of chewing function designed by Satoh et al. The maximum occlusal force was measured with the pressure sensitive sheet “Dental Prescale 50 H.”The results were as follows:
1. 90% of the patients scored over 70 with the VAS for denture occlusion. Chewing function scores ranged from 25 to 90; the median value was 50. Maximum occlusal forces ranged from 49 N to 503 N; the median value was 216 N.
2. The female group over 75 years old showed lower values than any other group.
3. A significant correlation (p<0.01, Spearman's rank correlation) was found between VAS scores of occlusion and chewing function scores.
4. No significant correlation was found between the VAS scores of occlusion and the maximum occlusal forces.

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The policy to promote retention of at least 20 teeth in 80-year-old presents substantial challenges to a changing health care system. Community based dental health services data demonstrate that greater numbers of natural teeth are being retained by older adults due to higher dental service utilization, effective caries prevention strategies, and a dramatic decreasing prevalence of periodontal disease.“Older-old”elderly, however, are becoming more frail and functionally dependent. Their oral health status is typically compromised and poor oral hygiene is promoting high dental caries rates and extensive periodontal diseases. Dental care providers must assume greater leadership and become more active participants in providing oral care for these “at-risk” elderly including domiciliary dental services.
As older patients are retaining more natural teeth, their dental status is becoming increasingly complex. The delivery of dental care to “older” elderly patients can present tremendous challenges with clinical decision-making as well as overcoming barriers associated with treating the disabled elderly patient. In an effort to maintain and/or improve function and esthetics as well as treat symptoms and pathology, the dentist should consider: 1) patient desires and expectations; 2) type and severity of dental need; 3) impact on quality of life; 4) probability of positive outcome; 5) reasonable treatment alternatives; 6) ability to tolerate stress of treatment; 7) capability to maintain oral health; 8) financial and other resources; 9) dentist capabilities; and 10) other issues. These determining factors will help the dentist decide the appropriate extent of care to be provided.

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It has been well recognized that geriatric dentistry will become more important in the 21st century because of the increase of the elderly population and their longevity of life. Geriatric dentistry should tackle prevention, medication, and welfare as one. The main theme of prevention is health promotion to obtain high quality of life by maintaining their own teeth and occlusion. The purpose of medication is to enhance the quality of life by repairing masticatory function and esthetics. Moreover, dentists should take part in the care for the elderly with complex medical conditions through oral health care and rehabilitation of eating. Technology assessment is one of the most useful ways to examine the quality of medicine and quality of life. In this paper, technology assessment has been performed to evaluate complete denture treatment using our original scores. The subjects were classified into two groups, one group of 28 persons (12males, 16 females, mean age 71.5 years) who were treated by complete denture treatment at the university hospital and another group of 30 (13 males, 17 females, mean age 72.3 years) who were treated by complete denture treatment at private offices in Kure City. The complete denture score was obtained by examination of quality of medicine, the chewing function and satisfaction scores of complete denture prosthesis defined treatment outcome, and the QOL score was used to identify their own quality of life. As a result, complete denture score in the group at the university hospital was significantly higher than that in the other group. Significant relationship was detected between the complete denture and satisfaction scores (p<0.01). The complete denture score was closely related to the QOL score. Under limited conditions of this study, it could be concluded that high quality of complete denture treatment enhances the edentulous patient's quality of life.

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Mechanical properties (ultimate transverse strength, transverse elastic modulus, transverse deflection) of heat-cured denture base resin relined with four different types of denture reline materials were tested. As a result, the ultimate transverse strength of the denture base material relined with the four denture reline materials deteriorated compared with that of the denture base material itself. In general, the mechanical properties of the relined denture base follow the mechanical properties of the bulk denture reline material. The proportion of thickness of the denture reline material affects the mechanical properties of the relined denture base

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To understand the intrinsic factors of the pain sensitivity in patients with masticatory muscle pain, pressure pain threshold (PPT) changes in masseter muscles were measured before and after clenching.
Twenty-one outpatients (7 males, 14 females, aged 37.6±14.3) with unilateral masseter muscle pain lasting longer than 6 months were enrolled in the experimental group, and 19 healthy volunteers (7 males, 12 females, aged 41.7±7.4) were enrolled in the control group.
PPT measurement was performed before, right after, 30 min after, and 60 min after clenching. All the PPT data were evaluated by using the one before clenching as the relative value of 100.
During clenching, surface EMG_s were recorded from both masseter muscles.
All the recordings were performed on the day that the subjects did not feel any pain in the target region. Although little change was found in normalized PPTs on the control side of the control group and the symptomatic side of the experimental group at right after, 30 min after, and 60 min after clenching, those on the asymptomatic side increased to 111.9 and 113.6 at 30 min after and 60 min after clenching, respectively. Statistical significance was found in the PPTs between the asymptomatic side (111.9±23.0) and the symptomatic side (95.7±14.7) at 30 min after clenching (repeated measures ANOVA).
From the results, it was considered that the PPTs measurement before and after clenching task could be suitable parameters for diagnosis of chronic masticatory muscle pain in patients.

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IPS Empress^®, an all-ceramic crown system, achieves natural tooth color appearance, however, because of the light transmission itself, abutment tooth color is influenced by the final restoration.
This paper describes the effect of color blocking and changing through background color when using nine adhesive resin cements (50 and 100μm) and four ceramic ingots (TI, TII, OI and OII), which have different light transmission with a thickness of 1.5 mm in the middle coronal tooth portion, in the staining technique. The results were as follows:
1. The effect of color blocking was significantly improved when only using JO (IMPERVA DUAL Opaque) and PO (PANAVIA 21 Opaque) cementation insertion.
2. According to the increase in thickness of resin cement of all specimens, the value of L* tended to decrease as the luminosity decreased, the value of a* did not significantly change, and the value of b* tended to increase and there was a tendency to become more yellow.
3. As the effect of color blocking, specimens using Oil ingot with low light transmission had the highest value. As the influence of thickness through the resin cementation, T I ingot with higher light transmissionhad a significantly improved value.

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Stress distribution in a free-end saddle overlay denture retained by various types of metal root caps was analyzed using a two-dimensional finite element method (FEM). The analyzed model was a hemi-mandible with only a canine remaining, and sectioned into 13, 113 elements. The dynamic characteristic of a magnetic attachment was also analyzed in the same way on a model with 18, 000 elements. The analysis was to elucidate the basic functions of the magnetic attachment which had not been analyzed yet.
1. The number of elements is very important in the FEM analysis, because the results are affected significantly by the number of elements.
2. The height of the root cap has a significant effect on the stress distribution of the denture.
3. The steepness of the lateral face of the root cap also has a slight effect on the stress distribution.
4. The location of load showed the most notable influence on the stress distribution in tissues.
5. By application of a magnetic attachment such as a denture retainer, the abutment tooth will not deliver an excessive load.

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A multipurpose, maxillofacial X-ray tomographic device, Scanora 6 (Soledex), which can be installed in dental clinics because of its small size compared to conventional CT, has been developed and introduced to Japan. In a previous study, we examined the basic performance of Scanora to assess its applicability to prosthodontic diagnosis and reported that Scanora permitted evaluation of the maxillofacial morphology and structure including jaw bone and temporomandibular joints, that X-rays obtained with Scanora were highly reproducible, and that it was a very useful instrument for examination of temporomandibular joints.
In this study, prosthodontic diagnosis was carried out using Scanora in 5 patients with severe resorption or morphological abnormality of alveolar ridge in the area of defect.
It was found relatively easy to derive clear-cut information on alveolar morphology, which is an important element in prosthodontic diagnosis, from tomograms obtained with Scanora.

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To determine the relationship between the lateral dentoskeletal forms of complete denture wearers and the direction of bite force, the lateral dentoskeletal forms of eight subjects in the normal face group were examined by cephalography. The directions of bite force during vertical clenching in various maxillomandibular relations were measured and correlated with the craniofacial forms.
The results revealed that the lateral dentoskeletal forms and the direction of bite force in complete dental wearers had a closer relationship than that in subjects with normal occlusion and dentition. The direction ofbite force for complete denture wearers inclined more towards the front than in subjects with normal occlusionand dentition, and more so as the vertical maxillomandibular relation increased. The results suggested theextreme importance of setting a suitable occlusal plane and vertical maxillomandibular relationship.

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This study was conducted to evaluate the influence of the frontal dentoskeletal form in complete denture wearers on the lateralized masticatory index and the direction of the bite force.
The frontal dentoskeletal forms of eleven complete denture wearers in the normal face group were analyzed by posteroanterior cephalograms. The subjects were divided into left and right deviation groups, and the mechanisms of their jaw functions were analyzed in terms of the lateralized masticatory index and bite force angulation in the horizontal plane during vertical clenching. The magnitude of bite force was divided into two levels
.
As a result, it was found that the lateralized masticatory index was strongly influenced by the frontal dentoskeletal form and chewing habits during masticatory movement with relatively lower bite force.This suggested that the mandible function, including the direction of bite force and the frequency of the lateralized masticatory index, should be examined in detail to improve the right and left balance in the dentoskeletal form and denture retention and stability.

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Double casting method (cast on technique) is sometimes used for attachment work. As to this method, the present study was conducted to investigate the partial deformation of casting and the castability of the second casting. A wax sheet stuck on the first cast plate of a gold alloy was invested with a gypsum-bonded investment. Using a centrifugal casting machine, two kinds of alloy were cast in the mold heated to 700°C: one was the same alloy as the first casting and the other was a silver-palladium-gold alloy.
Protuberances on the first casting and the corresponding concaves on the second casting were found approximately beneath the sprue. Some protuberances appeared to be wavy, while the others appeared to be hemispherical, with a maximum height of 220μm. There were no differences in the size and shape of crystal grain as well as the composition between the protuberance and the body of the first casting. Therefore, the protuberances did not result from the adhesion of the molten metal to the first casting, but from the partial deformation of the first casting. In case of using a silver-palladium-gold alloy for the second casting, some of the first castings had concavities.
The castability of the second casting was significantly low, compared with general casting.

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In this investigation, functional displacement of upper and lower molars were revealed using the displacement transducer type M-3. This transducer was invented by Miura in order to reveal three dimensional tooth displacement.
The results were as follows:
1. In general, each upper molar moved in the apical palatal direction while each lower molar moved in the lingual direction.
2. For each upper molar, the amount of displacement varied proportionally depending on the clenching force. The direction of displacement was towards the palatal side.
3. For each lower molar, the amount of displacement varied proportionally depending on the clenching force. The direction of displacement was to the lingual side.
4. The amount of displacement depending on the clenching force was larger in each upper molar than that in each lower molar.
5. It was suggested that the relative position of the upper and lower molars and the relation of their occlusal contacts at the intercuspal position vary depending on the clenching force.

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In order to establish a standard for commercially available high functional gold alloys for clinical applications, a diversified study on the effects of softening and hardening heat treatment on the mechanical properties, including Vickers hardness, tensile strength, and the elongation of five commercial high functional gold alloys, was carried out. The commercial high functional gold alloys studied were Carrara H (CA), Degunorm (DE), DG/VO 8 (DG), Pontor LFC (PO), and Mainbond EH (MA).
The results were as follows:
1. Vickers hardness of these five commercial high functional gold alloys when cast ranged form 163 to 183 HV, while Vickers hardness of these five commercial high functional gold alloys after softenig and hardening heat treatment ranged from 122 to 148 HV and 182 to 208 HV, respectively.
2. Tensile strength of these five gold alloys when cast ranged from 51.5 to 63.32 kg f/mm². Tensile strength of these five gold alloys after softening and hardening heat treatment ranged from 36.8 to 54.32 kg f/mm² and 58.2 to 67.62 kg f/mm², respectively.
3. The elongation of these five gold alloys when cast ranged from 4.1 to 11.1%. The elongation of these five gold alloys after softening and hardening heat treatment ranged from 6.2 to 19.4% and 3.1 to 5.3%, respectively.

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The purpose of this study was to examine the effects of the direction of lateral tooth guidance on jaw movement. Nine healthy adult volunteers (10 experimental sides) with natural dentition were the subjects. Lateral excursion was recorded by using a six-degree-of-freedom jaw motion analyzing system while the subjects wore a maxillary acrylic resin splint. Six different acrylic resin guidances were attached to the canine region of this splint. These guidances included M typeo (latero protrusive) and D type (latero retrusive) with 15, 30, and 45 degrees of inclination.
It was found that D type lateral tooth guidance led a more posterior pathway for the incisal point and working condylar point than M type lateral tooth guidance at each inclination. The results showed that Dtype guidance could decrease posterior condylar space during bruxism and cause overload in temporomandibular joint.

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In case of fixed partial denture cases, how to set the contact state between the applied pontic basal surface of fixed partial denture and the alveolar mucosa is important. Various opinions are presented including slight and noncompression methods. How to confirm the contact state in the mouse depends on the doctor's experience and no established method is available. In determination of the contact pressure between the pontic basal surface and alveolar mucosa, a polyvinylidene fluoride film (PVDF) is continuously used.
In the present study, similar to Report 1, PVDF, previously bonded to pseudomucosa, was tested under various compression conditions using a pressure tool, which simulated the pontic basal surface, to analyze the amount of load in relation to the output voltage of PVDF. The results were as follows:
1. A high correlation was observed between the amount of load added and the output voltage of PVDF irrespective of the pressure condition.
2. By measuring the area surrounded by the PVDF output voltage line and zero-voltage line, it was possible to presume the amount of dynamic load applied to the pseudomucosa.
The results suggested that PVDF can be successfully applied to adjust the pontic basal surface of a fixed partial denture.

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In order to apply UCC to post and cores or bridges, sintered zirconium (3Y 20 A) was selected as the reinforcing material. In order to combine cast OCC to 3 Y 20 A, it is necessary to line them with dental porcelain as a binder. In order to determine a higher bonding strength, this study was conducted to observe diffusing of ion, to discuss strength of 3Y 20 A itself and bonding strength, and to apply heat treatment (Ht) to the 3Y 20 A specimen bonded to dental porcelain. The results were as follows:
1. K and Na ion diffused from dental porcelain to 3Y 20 A at 1, 200°C and 1, 400°C respectively.
2. The permeation of glass constituents of porcelain into 3Y 20 A, and the formation of the reacted layerwith growth and transformation of crystalline grains were found according to diffused area at 1, 400°C This factor is improper because the strength of the reacted layer is less than that of dental porcelain.
3. Annealing after machining 3Y 20 A is necessary because the strength of surface transformation increased by machining and decreased due to mutual transformation at 1, 200°C.
4. In this bonding strength 3Y 20 A/OCC test, Duceratin opaque had a maximum value of 1, 200°C.

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The purpose of this study was to evaluate the possibility of the color adjustability of luting resin cements to all ceramic crown. In this study, Laminabond system (Shofu Inc.) of luting cements was used and the color adjustability on all ceramic crown of IPS-Empress system, which has a high translucency, was examined. Color difference (dE) and color coordinates (dL* and dC*) of ceramic sample (shade A1, A3, and A4) on metals (Pd-alloy and Au-alloy) to target color (ceramic sample+ ingot) were measured by means of a spectrophotometer (CAS-ID 1) with or without luting resin cements in-between. The luting cements tested were monotone cements (Opaque, Light, Orange, Red, Brown, and Blue) and mixed cements of Opaque and one of the others with the mixing ratios of 80: 20, 60: 40, 40: 60, and 20: 80. Opaque cement and mixed cements of Orange, Red, or Brown indicated efficient color adjustability to increase dL* and dC* and of dE from 1.5 to 3.5 for any kind of ceramic shade and metal for underlaying layer. In conclusion, mixed cementsat an adequate mixing ratio have color adjustability for the all ceramic crown of IPS-Empress.

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The purpose of this study was to analyze the evoked EMG in masseter muscles in response to electrical and magnetic stimulation during fatigue.
In the electrical stimulation experiment, six healthy male subjects were asked to maximally clench their teeth for 15 sec 9 times. A single rectangular wave of 0.5 msec duration was applied to the skin over the mandibular notch during rest periods of maximum clenching. The evoked EMG was delivered by surface electrodes from ipsilateral masseter muscles. In the magnetic stimulation experiment, eight healthy malesubjects received magnetic stimulation via a figure 8-shaped coil to the optimum region of the scalp during rest periods.
With electrical stimulation, the latency of the evoked EMG was not changed during the sessions but the duration was extended and the amplitude was decreased.
With magnetic stimulation, the latency was longer and the amplitude was smaller than with electrical stimulations. When the periodic clenching passed, the amplitude decreased, while the latency and duration remained unchanged.
In conclusion, periodic clenching fatigue influenced the evoked EMG in masseter muscles induced by electrical and magnetic stimulation.

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We developed a barrel finishing condition for denture base resin. The purpose of this study was to clarify the effect of barrel finishing on the surface texture of artificial teeth. Artificial teeth used in this study were porcelain, composite resin, and acrylic resin teeth. The barrel finishing condition indicated by the manufacturer and that developed by our department were both used. The surface roughness values of Ra and Rt were measured with a surface texture measuring instrument. Then the samples were observed under a scanning electron microscope.
The results were as follows:
1. The luster of porcelain teeth and composite resin teeth were slightly decreased after barrel finishing.Many small cracks were observed under SEM.
2. The luster of acrylic resin teeth after barrel finishing was the same as that of untreated teeth.
3. Surface roughness of porcelain and composite resin teeth were slightly increased in Ra by barrel finishing, but the range of difference was from 0.02μm to 0.04μm.
4. Surface roughness of acrylic resin teeth was slightly decreased by barrel finishing.
It was considered that improvement of the surface texture of denture base resin was possible, even though surface roughness of porcelain and composite resin teeth was slightly increased by barrel finishing.

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