Ten-year longitudinal study on the state of dentition and subjective masticatory ability in community-dwelling elderly people.

PURPOSE: The aim of this study was to reveal whether the differences in further loss of teeth and occlusal supports, and change in masticatory ability depend on the status of dentition at the age of 70 in community-dwelling elderly people. METHODS: A 10-year longitudinal survey was carried out on 349 (176 females and 173 males) elderly subjects. The subjects to be analyzed were classified into four groups in accordance with the classifications of Miyachi's Triangular Classification. Zone A: subjects with ten or more occlusal supports. Zone B: those with nine to five occlusal supports. Zone D: those with four or fewer occlusal supports and 11 or more remaining teeth. Zone C: those with ten or fewer remaining teeth. The numbers of remaining teeth and occlusal supports were recorded in both examinations. Questionnaires regarding their food intake status were given to subjects. RESULTS: Subjects in Zone B had greater numbers of teeth loss than those in Zones A and C. Subjects in Zone B and D lost greater numbers of occlusal supports than subjects in Zones A and C. The number of food items that could be chewed had significantly decreased in subjects who remained in Zone A and those who changed from Zone B to Zones D and C. CONCLUSIONS: It was shown that various states of dentition classified by Miyachi's Triangular Classification at the age of 70 resulted in different numbers of remaining teeth and occlusal supports and changes in masticatory ability 10 years later in community-dwelling elderly people.

[Difference of body movements accompanying mandibular movements in standing and sitting positions].

PURPOSE: To assess whether body movement accompanying jaw movement exists even in sitting position, and, if so, to investigate differences of body movements in the sitting and standing positions. METHOD: The subjects were six men (age, 25-29 years, mean, 27.0 years) without stomatognathic problems. During the measurements, their Camper's planes were kept horizontal. One measurement sequence consisted of 20 s of tapping preceded and followed by 10 s of intercuspation. Mandibular movements (lower incisor point) were measured by referring to a coordinate system located on the maxilla, and head movements (upper incisor, condyle, etc) with TRIMETII (Tokyo Sizaisya) and body movements (sternum point) in sagittal plane were measured by referring to a coordinate system located on the floor with Proreflex (Qualisys). RESULTS: Body movements accompanying jaw movements were detected even in sitting position. The ratio of body movements to jaw movements was significantly larger in standing position than in sitting position using Wilcoxon matched-pairs signed-rank test. Peak power of body movement at corresponding frequency to the open-close movement was significantly larger in standing position than in sitting position using Wilcoxon matched-pairs signed-rank test. On the other hand, there was no difference between sitting and standing position in probability of body movement detection by the original wave analysis using Wilcoxon matched-pairs signedrank test. CONCLUSION: Body movements accompanying jaw movements were detected even in sitting position, and were smaller than in standing position. However, the probability of movements detected in original wave had no difference between the positions. Thus we concluded that we can analyze body movements during mastication in natural sitting position.

A precise and useful method for coordinating computed tomography and jaw movement frames of reference.

PURPOSE: The aim of this study was to develop a means of coordinating helical computed tomography (CT)- based morphological data in 3 dimensions (3-D) with that pertaining to jaw movement as recorded by a device that measures jaw movement in six-degrees-of-freedom (6-DOF), thus producing multi-point movement analysis of the condyle. METHODS: The study sample was two volunteers. One of the subjects had erosive bony changes in both condyles, while the other had healthy condyles. We employed a customized facebow, which enabled us to coordinate jaw movement data and morphological volume data from CT. Total uncertainty of the coordination was computed, according to International Organization for Standardization (ISO). In order to demonstrate the effects of multi-point analysis for complex condylar movement, we tried to visualize the trajectory of the working condyle in lateral excursion. RESULTS: The overall uncertainty at a condylar center chosen as an example to illustrate the method was 0.38 mm, 0.19 mm, and 0.50 mm in antero-posterior, lateromedial, and supero-inferior directions, respectively, in terms of 95% coverage as defined by the ISO. CONCLUSION: We developed facebow-based X-ray markers with high clinical operability, which could correlate the helical CT's coordinate system with our 6-DOF jaw movement measuring system for precise analysis of 3-D condylar movements. In motion analysis of rotational condyle, even a small amount of measurement error cannot necessarily be neglected. Then, a multi-point approach such as that realized by our system presents the best option.

[Effect of occlusal form in buccal cusps of molars on masticatory function and intraoral food flow].

PURPOSE: The degree of crushing and intraoral food flow was evaluated using peanuts by the occlusal forms of a removable bridge as indices to clarify the occlusal formative effect of maxillary molars on masticatory function. METHODS: The subject was a 29-year-old male without any gnathostomatic disorders and his removable bridge ([7] 6 [5]) was so made in interocclusal distance as to be 0.5, 1.0 or 1.5 mm from 0 mm standard having occlusal contact to antagonist. Then the subject was asked to chew 3 g of peanuts in a series of unilateral chewing schemes consisting of 5, 10, and 20 masticatory strokes each. The pool rate in the buccal oral vestibule and lingual proper oral cavity as an index of food flow was calculated as the weight of peanut particles accumulated in each side as a percentage of the total volume of recovered peanut particles. Also, the degree of crushing was calculated as the weight of peanut particles that passed through 10-mesh sieves as a percentage of the total weight in each side. RESULTS: As the interocclusal distance to the mandibular cusp increased with abrasion on the inside at maxillary buccal cusps, the pool rate of the buccal oral vestibule was significantly increased and correspondingly that of the lingual proper oral cavity was decreased. The degree of crushing indicated non-significances statistically among 0, 0.5, and 1.0 mm and significantly decreased in 1.5 mm as compared with 0 mm. CONCLUSION: As the interocclusal distance to mandibular cusps from the maxillary inside of buccal cusps was increased, the pool rate of the crushed peanuts in the buccal side increased and the pool rate of crushed peanuts in the lingual side decreased, and the particles showed a comparatively low degree of crushing. It is clear that maxillary buccal occlusion has an effect on the crushing function and food flow.

Temporomandibular joint loading generated during bilateral static bites at molars and premolars.

The aim of this study was to investigate the features of the loading vectors of the temporomandibular joint (TMJ) generated during bilateral static bites at the molars and at the premolars, and to determine the major factors affecting the difference between the two loading vectors. We computed the subjects' estimated and theoretical minimum TMJ loadings under the two different bite conditions by applying the subjects' bite-force and electromyographic (EMG) data to a two-dimensional (2D) standard model of the jaw based on a rigid-body spring model of the TMJ. For a molar bite, (1) the estimated loading vector was not equal to its theoretical minimum; (2) the TMJ-loading/bite-force ratio, describing the proportion of TMJ loading, was relatively small, 0.477 on average; and (3) the estimated loading vector pointed in the direction of the central part of the articular disk's intermediate zone. For a premolar bite, on the other hand, (1) the estimated loading vector was nearly equal to its theoretical minimum; (2) the TMJ-loading/bite-force ratio was relatively large, 0.904 on average; and (3) the estimated loading vector pointed at the superior portion of the articular disk's intermediate zone. The differences between the TMJ-loading vectors for molar and premolar bites originated primarily from changes in the bite-point location.

Histological and histomorphometrical changes in rat alveolar bone following antagonistic tooth extraction and/or ovariectomy.

OBJECTIVE: To examine changes appearing in the alveolar bone following the removal of the mechanical stress of occlusal loading, as well as the added influence of estrogen deficiency on such changes. DESIGN: The right mandibular molars of female rats were extracted. After 8 weeks, 12 animals were ovariectomized (OVX), and the other 12 were subjected to sham surgery (sham). Four weeks after surgery, all rats were sacrificed. The left-half and right-half maxillas of the sham group (the sham-occluded side and the sham-extruded side, respectively) and right-half maxilla of OVX group (the OVX-extruded side) were examined by histological observation and bone histomorphometry. RESULTS: The vertical height of alveolar bone in the sham-extruded and the OVX-extruded sides increased as compared with that of the sham-occluded side. In both extruded sides, active bone formation occurred on the surface of the alveolar bone facing the periodontal ligament, but the bone marrow was expanded and the bone volume had decreased in the internal area of the alveolar bone. In the OVX-extruded side, the bone marrow expanded more remarkably than that of the sham-extruded side, and the highest percentage of osteoclast surface was detected. CONCLUSIONS: Around the extruded teeth, there were regional differences in bone dynamics between the internal area of the alveolar bone and the bone surface facing the periodontal ligament, and estrogen deficiency seems to have caused further loss of bone volume in the interior of the alveolar bone supporting the extruded tooth.

[Evaluation of prosthetic treatment using number of chewing strokes until swallowing of water absorbing rice crackers].

PURPOSE: Various methods of evaluating the ability of mastication have been reported, most of which involve evaluating of the ability to comminute foods. In this study, a new method of evaluating the ability of mastication focusing on bolus formation was applied to denture wearers. METHODS: One hundred and twenty-five subjects (71 males and 54 females) using removable dentures and receiving follow-up in the Niigata University Hospital were selected. This group was categorized by Eichner's classification, and investigated for the effect of prosthetic treatment by counting the number of chewing strokes until the first swallow of rice crackers. RESULTS: It was clarified that the number of chewing strokes until the first swallow counted by visual observation agreed well with the number of chewing strokes counted by electromyogram wave of masseter muscle, laryngeal motion, and swallowing sound, as a preparatory experiment. Using the method of counting chewing strokes by visual observation, the effect of prosthetic treatment was evaluated, and the results were as follows. 1)There is a significant difference in the number of chewing strokes without dentures between the Eichner A group, B group, and C group. 2)There was no significant difference in the number of chewing strokes with dentures among the three groups. 3)A significant decrease in the number of chewing strokes was proven by the use of removable dentures. 4)Both the improvement rate of chewing strokes (the ratio of the number of chewing strokes with dentures until the first swallow to that without dentures) and the difference of chewing strokes increased significantly in the order of Eichner A, B, and C. CONCLUSION: It was clarified that the effect of prosthetic treatment can be quantitatively evaluated by counting the chewing strokes of rice cracker. Moreover, it was suggested that the condition of prosthetic treatment can be evaluated by analyzing the improvement rate of chewing strokes.

Analysis of head and mandibular tapping movements in patients with mandibular protrusion.

The present study was conducted to investigate whether there was a functional coupling between the head and mandibular movements in ten patients with mandibular protrusion (MP) and ten control subjects with normal occlusion (Normal), using a six degrees-of-freedom measuring device. Single-peak waveforms were predominantly seen in both MP (98.2%) and Normal (99.3%). However, vertical displacements of the upper and lower incisor points (VD(UIP) and VD(LIP)) were all significantly larger in MP than those in Normal. The ratio VD(UIP)/VD(LIP) also increased more sharply with an increase in VD(LIP) in MP, compared to that in Normal. Mandibular rotation in MP was also significantly larger than that in Normal. The results showed that, in MP, the head moves more vertically in rhythmical coordination with mandibular movement during tapping. Finally, it may be that this larger vertical head movement is related to the greater condylar rotation in MP subjects.

Condylar bone change and sagittal incisal and condylar paths during mandibular protrusive excursion.

This study showed significant differences in sagittal condylar and incisal path angles during mandibular protrusive excursion, as well as flattening of the condylar path related to the existence and type of condylar bone change. Twenty-eight (28) patients with signs and symptoms of TMJ disorders were studied, using a six-degrees-of-freedom measuring device and helical CT. Sagittal incisal and condylar path angles at two mm and three mm condylar path lengths (CPL) were significantly shorter in the bilateral condylar bone change (BBC), compared to the no bone change (NBC) group. Also, NBC incremental sagittal condylar path angles from three to five mm CPL and NBC condylar path curvature at five mm CPL were both significantly larger than in BBC. Comparing types of bone change, incremental sagittal condylar path angles from three to five mm CPL was significantly less in osteophyte than in NBC or erosion groups. Condylar path curvature at five mm CPL was also significantly less in osteophyte than in NBC.

[A study on the differences in function of free-sided and unilateral chewing].

PURPOSE: Unilateral chewing requires a greater number of chewing strokes up to the point of the first swallowing. The rate of storage of ground food particles in the oral vestibule is said to be high during unilateral chewing. However, influence of the masticatory method, that is free-sided or unilateral chewing, involved in masticatory efficiency has not been elucidated. On that point, in order to clearly represent the effects that free-sided (bilateral) chewing and unilateral chewing have on the chewing efficiency, our purpose was to examine the difference of the functions of both free-sided chewing and unilateral chewing. METHODS: We used 116 dentate subjects with normal occlusal relations, and compared the number of chewing strokes for peanuts up to the point of the first swallowing (abbreviated as "chewing strokes") for both free-sided chewing and unilateral chewing. Following this, we made calculations regarding the amount of saliva secretion, occlusal force, and contact points of posterior teeth. Based on the averages of three parameters (saliva secretion, occlusal force and contact points of posterior teeth), all the subjects were classified into two groups (high score group and low score group). In the two groups, we counted the difference in the number of free-sided chewing and unilateral chewing. And also in two groups, the amount of remaining coarse particles immediately prior to the first swallowing was investigated between free-sided chewing and unilateral chewing. RESULTS: The number of chewing strokes by free-sided chewing for all subjects was 10% less than that of unilateral chewing. Furthermore, the numbers of chewing strokes by free-sided chewing were all less than those of unilateral chewing in both groups on three parameters. The amount of remaining coarse particles by free-sided chewing was significantly smaller than that of unilateral chewing in the low score group of saliva secretion and occlusal force. CONCLUSIONS: The number of chewing strokes by free-sided chewing was less than that of unilateral chewing in both of the high score group and low score group on the amount of saliva secretion, occlusal force, and contact points of posterior teeth.

The relationship between morphological changes of the condyle and condylar position in the glenoid fossa.

AIMS: To investigate whether condylar morphological changes influence the condyle position in the glenoid fossa as well as the amount of condylar movement from the intercuspal position (IP) to the reference position (RP). METHODS: Helical computed tomography was used for precise measurement of the joint spaces at IP and RP in 22 subjects (mean age 22.7 years). Subjects were divided into 2 groups, those without condylar bone changes (n = 11) and those with condylar bone changes (n = 11). The latter group was further subdivided into a flattening subgroup and an osteophyte subgroup, according to the type of condylar bone change. RESULTS: There were no significant differences in the width of the anterosuperior or posterosuperior joint spaces at IP between either the 2 groups or the 2 subgroups. On the other hand, during condylar movement from IP to RP, the condyles moved significantly more superiorly and posterosuperiorly in the bone-change group than in the no-bone-change group. There was also greater absolute horizontal condylar movement between IP and RP in the bone-change group. In addition, within the bone-change group, the type of condylar bone change influenced the amount of condylar movement. Joints with osteophyte formation showed the most superior, posterosuperior, and absolute horizontal movement from IP to RP. CONCLUSION: The findings that condyles of the bone-change group, especially those with osteophyte formation, were located significantly more anteroinferiorly in the glenoid fossa at IP than RP than the condyles of the no-bone-change group suggest that condylar IP-RP positional changes might be related to condylar shape alteration.

The relationship between retruded contact position and intercuspal position in patients with TMJ osteoarthritis.

This study was conducted to investigate the relationship between posterior mandibular excursion movement and temporomandibular joint osteoarthntis (TMJ OA) in 25 orthodontic patients with Angle Class I and Class II, using a six degrees-of-freedom measuring device and helical computed tomography. There were significant differences found in three-dimensional length, antero-posterior, absolute latero-medial and supero-inferior incisal, and condylar intercuspal position (IP)-retruded contact position (RCP) slides between bilateral, unilateral, and no condylar bone change groups. With respect to the types of condylar bone change, there were significant differences found in three-dimensional length, antero-postenor, and absolute latero-medial condylar IP-RCP slides between flattening, erosion and osteophyte groups. These results suggest that large three-dimensional, not only incisal but also condylar, IP-RCP slides might be related to the uni-/bilaterality and kind of TMJ pathosis, which might make such slides useful as clinical indices of TMJ OA.

Expression of estrogen receptor alpha (ER alpha) in the rat temporomandibular joint.

Numerous epidemiological studies have pointed out a higher frequency of temporomandibular disorder (TMD) in women than in men, which indicates the involvement of a sex hormone, such as estrogen, in the pathogenesis of TMD. Although estrogen is known to play pivotal roles in osteoarthrosis or rheumatoid arthritis in systemic joints, there have been few reports about the role of estrogen in the temporomandibular joint (TMJ). The effect of estrogen is generally mediated by the estrogen receptors (ERs) ER alpha (the predominant type) and ER beta. In this study we examined the expression of ER alpha protein and mRNA in the TMJ of adult male rats by immunocytochemistry and in situ hybridization histochemistry. Intense ER alpha immunoreactivity was localized in the synovial lining cells, stromal cells in the articular disc, and chondrocytes in the TMJ. These ER alpha-immunopositive synovial lining cells are characteristic of cytoplasmic processes identified with confocal and immunoelectron microscopy, which indicates that they are synovial type B cells. In situ hybridization histochemistry confirmed intense signals for ER alpha in the synovial lining cells and the sublining fibroblasts at mRNA levels. The nuclei of chondrocytes showed an intense immunoreaction for ER alpha in the maturative and hypertrophic layers of the articular cartilage. In addition to the nuclear localization of ER alpha, a weak immunoreaction appeared in the cytoplasm of some ER alpha-positive cells. These findings support the hypothesis that TMJ tissue-at least in the male rat-has the potential to be an estrogen target tissue.

Fatigue resistance of cast occlusal rests using Co-Cr and Ag-Pd-Cu-Au alloys.

STATEMENT OF PROBLEM: Fatigue failure in a removable partial denture framework includes fracture of the occlusal rest at the rest-minor connector angle. PURPOSE: This in vitro study evaluated the fatigue resistance of 0.8-mm-thick occlusal rests cast with Co-Cr and Ag-Pd-Cu-Au alloys. MATERIAL AND METHODS: The specimen consisted of occlusal rest (0.8 x 2.0 x 10 mm), vertical minor connector (0.9 x 2.0 x 5.0 mm), and denture base connector (1.5 x 5.0 x 25 mm). Twenty-five specimens each were cast with Co-Cr and Ag-Pd-Cu-Au alloys. From each group, 5 specimens were subjected to a load-deflection test conducted to determine the amount of deflection to be used in fatigue test. The fatigue test was performed such that the occlusal rest component was deflected by displacing the denture base component in a tissueward direction. Predetermined denture base displacement values of 0.25 and 0.49 mm for Co-Cr and Ag-Pd-Cu-Au specimens, respectively, were repeated at a rate of 500 cycles/min by use of a displacement-controlled fatigue testing machine, until occlusal rest failure occurred or a preset limit of 2 million cycles was achieved. The survival rates of the occlusal rests were calculated assuming a chewing cycle of 2 x 10(5) per year. Scanning electron microscopy (SEM) photographs were made to examine the fracture surfaces and to identify casting defects. The relationship between fatigue cycles and number of casting defects was determined by Spearman rank correlation analysis (P<.01). RESULTS: All 20 Co-Cr specimens outran the preset limit, whereas 18 Ag-Pd-Cu-Au specimens fractured. After 3 years of simulated clinical use, only 50% of the Ag-Pd-Cu-Au occlusal rests survived. Statistical analysis showed that the fatigue cycles and number of casting defects were inversely related (P<.01). Fatigue crack initiation occurred at the inner-curvature surface of the rest-minor connector angle. The typical Ag-Pd-Cu Au fatigue fracture surface consisted of smooth propagation and dimpled and smooth final fracture areas. CONCLUSIONS: This study suggests that cast Co-Cr rests are more rigid and fatigue resistant than Ag-Pd-Cu-Au rests. The fatigue resistance of 0.8-mm-thick occlusal rests may be adequate if cast with Co-Cr alloy. An increased number of casting defects may hasten the fatigue failure of occlusal rests.

Tissue-nonspecific alkaline phosphatase with an Asp(289)-->Val mutation fails to reach the cell surface and undergoes proteasome-mediated degradation.

A missense mutation in the gene of tissue-nonspecific alkaline phosphatase, which replaces aspartic acid at position 289 with valine [TNSALP (D289V)], was reported in a lethal hypophosphatasia patient [Taillandier, A. et al. (1999) Hum. Mut. 13, 171-172]. To define the molecular defects of TNSALP (D289V), this mutant protein in transiently transfected COS-1 cells was analyzed biochemically and morphologically. TNSALP (D289V) exhibited no alkaline phosphatase activity and mainly formed a disulfide-linked high molecular mass aggregate. Cell-surface biotinylation, digestion with phosphatidylinositol-specific phospholipase C and an immunofluorescence study showed that the mutant protein failed to appear on the cell surface and was accumulated intracellularly. In agreement with this, pulse/chase experiments demonstrated that TNSALP (D289V) remained endo-beta-N-acetyl- glucosaminidase H-sensitive throughout the chase and was eventually degraded, indicating that the mutant protein is unable to reach the medial-Golgi. Proteasome inhibitors strongly blocked the degradation of TNSALP (D289V), and furthermore the mutant protein was found to be ubiquitinated. Besides, another naturally occurring TNSALP with a Glu(218)-->Gly mutation was also found to be polyubiquitinated and degraded in the proteasome. Since the acidic amino acids at positions 218 and 289 of TNSALP are thought to be directly involved in the Ca(2+) coordination, these results suggest the critical importance of calcium binding in post-translational folding and assembly of the TNSALP molecule.

Long-term changes in trabecular structure of aged rat alveolar bone after ovariectomy.

OBJECTIVE: Trabecular structural changes in the jaw after long-term estrogen deficiency are not well understood. Therefore, we sought to observe the changes in rat alveolar bone for 1 year. METHODS: Six-month-old female rats were ovariectomized (OVX) or underwent a sham operation. After 1 year, bone histomorphometry and a node-strut analysis were performed on the interradicular septum of the mandibular first molar by using micro computed tomography and confocal laser scanning microscopy. Statistical analysis was carried out by using analysis of variance. RESULTS: The alveolar trabeculae of rats in the sham group had network structures, whereas the trabeculae of rats in the OVX group became fragmented. The trabecular bone volume, number, and thickness in the OVX group were significantly lower than those found in the sham group, and the trabecular separation was 4-fold higher in the OVX group than in the sham group. Bone resorptive and formative activity appeared to be moderately higher in the OVX group than in the sham group, but only the difference in bone formation was of statistical significance. CONCLUSION: By 1 year after ovariectomy, bone loss and trabecular fragmentation had occurred in the rat mandibular alveolar bone.

[Effects of ovariectomy on trabecular structures of rat alveolar bone].

To clarify the relationship between estrogen deficiency and tooth loss, we analyzed the trabecular structural changes of mandibular alveolar bone in ovariectomized rats. Two months after ovariectomy, the bone resorptive activity remarkably accelerated and caused high bone turnover. On the other hand, one year after ovariectomy, bone loss and trabecular fragmentation occurred in the alveolar bone, although the accelerated degree of bone resorptive activity was moderate. If elderly women could experience similar changes on their alveolar bone, we must pay more attention to the bone resorption presently after menopause and the trabecular fragility long after menopause.