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The Influence of Postural Changes in the Horizontal Maxillomandibular on Cervical Back Strength and the Activity of Neck and Mastication Muscles
Tohru Ogawa
1998 Volume 42 Issue 5 Pages
729-739
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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In contact sports such as rugby and American football, there are injuries to the head, neck, and oral regions when playing sports due to collision of the body and sports goods.
Interest is growing in the prevention of trauma and injuries due to contact sports, according to the increasing use of mouth protectors.
It is thought that the wearing of inappropriate mouth protectors can affect both athletic performance and bodily functions and can even lead to serious injuries.
In this study, several types of upper jaw resin splint were used in various horizontal maxillomandibular positions to investigate their influence on the cervical neck muscles. The effects on cervical back strength and the activity of the neck and mastication muscles were observed.
The results suggested that positional changes in the horizontal maxillomandibular affect cervical back strength and the activity of the neck and mastication muscles.
Therefore, it seems important to select an appropriate mandibular position when wearing a mouth protector.
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Keisuke Nishigawa, Eiichi Bando, Masanori Nakano
1998 Volume 42 Issue 5 Pages
740-746
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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Nocturnal bite force during sleep associated bruxism was measured in ten subjects. Hard acrylic dental appliances were fabricated for each subject's upper and lower jaws. Miniature strain-gauge transducers were mounted on the right and left sides in the first molar regions of the upper dental appliance. Thin metal plates that contact strain-gauge transducers were also attached to the lower dental appliance. Nocturnal bite force was measured for three nights at each subject's home after one-week familiarization of these appliances. Bite force signals were obtained with dynamic data logger, and then transferred to a computer. In this study, we defined bruxism event by using the following criteria: 1) Elevations of bite force signal above 5 kgf were selected as bruxism events; 2) When the inter-events interval was equal to or less than 2 seconds, these events were linked and treated as a single event ; and 3) When the duration of the event was less than 2 seconds, the event was rejected.
Four hundred ninety-nine bruxism events that satisfied the above criteria were selected from recordings for a total of 30 nights. The maximum voluntary bite force during the daytime was also measured with this system. The mean amplitude of detected bruxism events was 22.5 kgf (s.d. 13.0 kgf), and the mean duration was 7.1 sec (s.d. 5.3 sec). The mean amplitude of the highest nocturnal bite force in individual subjects was 42.3 kgf (range 15.6-81.2 kgf). The mean maximum voluntary bite force during the daytime was 79.0 kgf (range 51.8-99.7 kgf) and the mean ratio of nocturnal/daytime maximum bite force was 53.1%(range 17.3-111.6%). These data suggested that nocturnal bite force during bruxism can exceed the amplitude of maximum voluntary bite force during the daytime.
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Atsushi Yamashita, Takuo Kuboki, Akio Yoshimoto, Chieko Shirai, Makoto ...
1998 Volume 42 Issue 5 Pages
747-749
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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In the current study, the longitudinal survival rate of Pin Bridge (first described by Yamashita et al., 1996) was compared and contrasted with that of full coverage bridges luted by conventional cements. Subjects of this study was 41 patients (46 cases) who consulted the fixed prosthodontic clinic from January 1984 to January 1998. The determination of survival or failure of the restoration for any reason was based on data from clinical and dental x-ray examinations. Then Kaplan-Meier analysis for the survival rates and Log-rank test for testing difference in the rates between the groups were employed. As a result, the survival rate of the Pin bridge (75.7%) was almost identical to that of the full coverage bridge luted byconventional cement (63.1%)(p=0.3518) 10 years after installation. These data suggested that the survival rate of the Pin Bridge was as high as that of the conventional full-coverage bridge even with a relatively noninvasive nature of the pin restoration.
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Atsushi Yamashita, Takuo Kuboki, Akio Yoshimoto
1998 Volume 42 Issue 5 Pages
750-753
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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It is clearly inevitable to make precise holes in the proximal surfaces of the abutment teeth to get a highly stable clinical outcome with the recently described exciting dental rehabilitation method, e.g., Pin Bridge System (Yamashita et al., 1996). However, using a conventional preparation pin instrument, sometimes chipping of the enamel and/or the instrument bar breakage has been experienced. This article describes a newly-developed pin-hole drilling instrument using ultrasonic vibration. Since the tip of this preparation pin instrument does not rotate and the required pressure during preparation pin holes is extremely less than that for the conventional instrument, it is easy to hold the instrument precisely in the same position without any adversed effect such as enamel chipping or drill breakage. Finally, the described precision of the preparation hole diameter was clinically acceptable. It was concluded that the new device for making a hole in the proximal surface of the abutment teeth is very useful with the special features.
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Masakazu Okubo, Toshihiko Matsumoto, Noriyuki Narita, Morio Iijima, Hi ...
1998 Volume 42 Issue 5 Pages
754-759
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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Authors of previous studies suggested that the blood flow of denture supporting mucosa becomes an important index to evaluate the dentures, and a method to evaluate mucosal blood flow needs to be developed.
The purpose of this study was to report a novel instrument (LSFD) for noninvasive, noncontact, and 2-dimensional measurement of mucosal microcirculation using the dynamic laser speckle effect, and to demonstrate that this instrument can detect an experimental change in palatal mucosal blood flow.
Using LSFD, blood flow in five volunteers was measured before and after injecting 2% lidocaine containing 1/80, 000 epinephrine (0.2m
l) into incisive papilla. LSFD offers a laser flowgram showing the 2-dimensional variation of the AD value, which is the quantitative index of the blood flow velocity, and the average AD (ADav, unit: AU) in the area of interest can be calculated. Thus the laser flowgrams were compared visually and ADav 100 s obtained from the incisive papilla region were compared quantitatively.
As a result, the changes showing local anemia around the injection site were visualized, and the ADav 100 after injection (56.4±4.6) was significantly decreased (p<0.01, paired t-test) in comparison with that before injection (100.2±9.3).
These findings suggested that LSFD can detect the change in palatal mucosal blood flow. Therefore, LSFD may be applied to evaluate the blood flow of denture supporting mucosa and dentures.
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Takayoshi Hiruma, Takeshi Suganuma, Masahiko Funato, Yukiko Hiruma, Ak ...
1998 Volume 42 Issue 5 Pages
760-767
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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Accurate measurement of the condylar position is important for diagnosis and treatment of temporomandibular joint (TMJ) dysfunction. Radiography has been used for this purpose and recently, Scanora
® multimodal radiography was introduced to Showa University. The projection capacity of the Scanora
® in TMJ is still unclear. The purpose of this study was to estimate the accuracy of the measurement of the condylar position on sagittal tomography with Scanora
® and to compare Scanora
® images with LGM-1 images. Six TMJs obtained from dried skulls were used. Impressions of the joint space were obtained in order to estimate the actual dimensions. The Scanora
® images, LGM-1 images, and impressions were measured with a profile projector. The results were as follows: 1) The measurement error of condylar position on Scanora
® with a mean value of 0.29mm was similar to that on LGM-1 (0.25mm). 2) The measurement errors on both images in 1 of 6 TMJs were especially great (Scanora: 0.72mm, LGM-1: 0.87mm) while the measurement of the other 5 TMJs on both images showed smaller mean errors (Scanora: 0.2mm, LGM-1: 0.12mm). Therefore, there may be a considerable value of errors in the measurement on both images in the case of particular morphological types of joints. 3) It showed that the measurement errors of Y coordinates were larger than those of X coordinates. 4) The projection grade of both images were similar. These results suggested that sagittal tomography on Scanora
® is useful for clinical estimate of the condylar position.
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Shigeo Nitta
1998 Volume 42 Issue 5 Pages
768-778
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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Polyelectrolyte complex (PEC) is produced as a result of mixting polycations and polyanions. Since PEC has strong bio-compatibility, attention has been paid to its applications such as to prostheses for sites of tissue defect. In this study, PEC coating was applied to implants with the aim of reducing the period required for achievement of osseointegration of the implant and bone and increasing contact area. Thus post-implantation tissue reactions were investigated. As a result, the PEC-coated Titanium (Ti) and Hydroxyapatite (HA)-coated implant required shorter periods for achievement of osseointegration than the non-PEC-coated implant used as the control, the width of the bone trabeculae formed was increased, and the bone contact ratio was accelerated. These results suggested that PEC is a useful biological material for reducing the period required for achievement of osseointegration of the implant and bone and for increasing the contact area.
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Noriyuki Narita, Hiroshi Endo, Toshihiko Matsumoto
1998 Volume 42 Issue 5 Pages
779-789
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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Brain activities related to jaw movement were investigated to clarify the relationship between mandibular motion and magnetic fields of the primary sensorimotor cortex using a magnetoencephalography (MEG) system. Two adult volunteers were asked to conduct movements, that is, jaw opening and jaw closing including bilateral or unilateral biting, lateral jaw movement, tongue protrusion, and forefinger abductive movement. A total of 100 trials were performed for each session.
The results were as follows:
1. Readiness fields related to jaw opening, unilateral or bilateral biting as jaw closing, lateral jaw movement, tongue protrusion, and unilateral forefinger abduction bilaterally appeared in the primary sensorimotor cortices.
2. Motor fields related to opening and tongue protrusion appeared in the bilateral primary sensorimotor cortices, while motor fields related to lateral jaw movement and unilateral forefinger abduction dominantly appeared in the contralateral primary sensorimotor cortex to the working side.
3. Source analysis of readiness and motor fields related jaw, tongue, and finger movements indicated anteriorly directed 2 dipoles in the bilateral primary sensorimotor cortices.
From these findings, it was concluded that bilateral primary motor cortices play a role in preparing jaw movement regardless of the type of movement, while contralateral primary motor cortex to the working side dominantly controls asymmetrical jaw movement.
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The Relationship between Masticatory Path Pattern and Stability of the Movement as Seen from the Incisal Point
Masaoki Yokoyama, Hiroshi Shiga, Yoshinori Kobayashi
1998 Volume 42 Issue 5 Pages
790-802
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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The purpose of this experiment was to clarify the relation between masticatory path pattern and function, specifically the stability of movement, and to find the path pattern that is the most functionally effective. One hundred healthy subjects were asked to chew chewing gum on one side, and the fifth to the fourteen cycles were classified into eight patterns according to the method developed by Akiyama et al. Stability in terms of masticatory path and rhythm were quantitatively compared between the chewing patterns. As a result, it was found that there was an intimate relation between masticatory path pattern and stability and that the pattern which opened smoothly from the centric occlusion toward the working side and then closed toward the centric occlusion but showed a convex closing path in the vicinity of the centric occlusion was the most functionally effective. Furthermore, it was concluded that it was relatively easy to objectively evaluate masticatory function by merely observing the masticatory path pattern.
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Yasuko Takayama, Fujio Tsuchida, Toshio Hosoi, Kaoru Kobayashi
1998 Volume 42 Issue 5 Pages
803-814
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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Thirty patients who visited our hospital with a chief complaint of mismatched dentures and were subsequently diagnosed as class C 1 according to Eichner's classification (mean age: 66.6 years) were the subjects. The oral cavity of each patient was examined. In addition, questions were asked and X-rays and MRI were taken to investigate the relationship between disc displacement and factors such as condyle position and the state of the oral cavity.
Fisher's exact probability test and multivariate analysis utilizing Hayashi's quantification theory were applied for statistical analysis.
The results were as follows:
1. MRI imaging revealed disc displacement in 20 joints of 13 patients (43.3%).
2. Condylar bone changes were seen in 11 joints of 8 patients.
3. A lateral or bilateral posterior shift of the condyle position was seen in 54% of the patients with disc displacement.
4. Statistical analysis revealed significant difference in the type of artificial teeth, deviations in the opening and closing movements of the mouth, past history of temporomandibular arthrosis, and joint click between the patients with disc displacement and healthy individuals.
5. The presence of disc displacement most strongly correlated with the past history of temporomandibular arthrosis, followed by deviations in the opening and closing movements of the mouth.
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Hiroshi Shimizu, Masaharu Yoshinaga, Tetsuya Habu, Yutaka Takahashi
1998 Volume 42 Issue 5 Pages
815-822
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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A secure bond between self-curing resin and denture base resin is necessary for clinical success in denture repair. This study was conducted to evaluate the bond strengths of a new self-curing resin with barbituric acid derivatives to pour-type denture base resin, heat-cured resin and microwave-cured resin and investigate the effect of surface treatment. The repair surfaces of test specimens were treated in various manners before self-curing resin was applied to the joint. A three-point loading test was carried out to determine the transverse strength of specimens, and the surfaces of the three kinds of denture base resin after surface treatment were observed with a scanning electron microscope.
The results were as follows:
1. The surface treatment with dichloromethane following alumina air abrasive was the most effective on the three kinds of denture base resin.
2. The bond strength of a new self-curing resin with barbituric acid derivatives was weaker than that of conventional self-curing resin to denture base resins without any surface treatment.
3. The effects of any surface treatment with a new self-curing resin with barbituric acid derivatives were inferior to those with conventional resin.
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Part 1. Stress Analysis at Abutment Teeth and Alveolar Bone by 2-Dimensional Finite Element Method
Yoshihisa Inoue, Akihiro Kuroiwa, Akira Ogata, Akira Suzuki, Takafumi ...
1998 Volume 42 Issue 5 Pages
823-831
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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The occlusal stress distribution and displacement of model in a supported tooth were examined.
The effects of presence or absence of the bound saddle on the residual ridge and the rigidity of the removable bridge were evaluated by 2-dimensional finite element method.
The results were as follows:
1. Stress distribution on the abutment teeth under loading was more dispersed in the plate type removable bridge than in the non-plate type removable bridge. This finding was observed more markedly in canine abutment than in that of the second molar.
2. Displacement of the node of the removable bridge under loading was decreased in the plate type removable bridge than in the nonplated type removable bridge.
3. Irrespective of the presence or absence of the plate, the stress distribution in the abutment teeth under loading was more dispersed in the removable bridge made of metal with high Young's modulus than in the bridge with low Young's modulus.
4. Irrespective of the presence or absence of the plate, displacement of the node of the removable bridge under loading was more decreased using the removable bridge made of metal with high Young's modulus than in the bridge with low Young's modulus.
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Part 2 The Creation of the Tooth Crown Basic Models of Anterior Teeth
Hideki Aita, Yasuo Ueda, Takumi Yorimoto, Kazuhiro Hikita, Noboru Ohat ...
1998 Volume 42 Issue 5 Pages
832-838
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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For the past 10 years, we have been engaged in research on development of CAD/CAM system for prosthetic restoration such as crown and bridge in molar teeth. In order to apply this system to anterior teeth, it is necessary to create the crown basic model data of the anterior teeth. The purpose of this study was to complete a library of basic crown model data of all teeth for the CAD system.
The results were as follows:
1. By dividing the incisal edge or the cuspid into a grid pattern, solid models of anterior teeth represented by bicubic Bezier surfaces were made from three-dimensional coordinate data of four-fold enlarged plaster models measured from five directions.
2. In order to represent the coronal anatomical features of the anterior teeth, it was necessary to divide the four-fold enlarged models into more than 104 Bezier surfaces, and the real size models into more than 43 Bezier surfaces.
3. The results suggested that consideration of the functional crown forms of the natural teeth may be necessary to decide the most suitable surface for basic crown models.
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Shoichi Ishigaki, Emiko Morishige, Kyohei Kajiwara, Fumio Takashima, T ...
1998 Volume 42 Issue 5 Pages
839-846
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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The purposes of this study are to reveal whether there is a corresponding activity in cervical and dorsal muscles during chewing function and whether the size and the hardness of the testing food affect those activities.
The subjects were 15 males and 15 females. Mandibular movement during chewing motion and EMG activities of the anterior belly of digastric muscle, the sternocleidomastoid muscle, and the post-cervical and shoulder regions of the trapezius muscle were simultaneously recorded with Bio PAK System.
The results of this study showed corresponding cervical and dorsal muscle activities during chewing. Furthermore, these EMG activities were affected by the size as well as the hardness of the test food.
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Mika Mochizuki, Kensuke Yamagata, Kiyomi Tokutomi
1998 Volume 42 Issue 5 Pages
847-856
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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Dynamic palatography was used to identify contact patterns of tongue-to-palate and tongue-toteeth movements in 18 dentulous adults (11 males and 7 females) during the production of the following sentence:[sakura-no-hana-ga-sakima ∫ita].
The palatography sensor of thin film type with 96 electrode arrays (KAY: model 6300) covered the subject's palate and maxillary teeth. Real-time recording of speech sound waves and tongue-to-sensor touch signals were taken simultaneously. Then, speech sound waves, spectrum, and palatogram were simultaneously displayed on the CSL (Computerized speech lab, Model 4300 B) so that the relationship between speech sound analysis and movement of the tongue could be easily observed.
The results showed that the tongue-to-teeth contact area of each sound differed from the others. However, its range was confined within the cervical half of lingual surface of incisors and the lingual cusps of the molars. When the contact patterns of this dynamic palatograms were compared with the contact patterns of static palatograms, the maximum contact pattern of [s, k, ∫, and t] sounds was found to be quite similar. However, a slight difference was noted between the dynamic and static palatograms for [r] and [n] sounds. The duration of the articulatory activity for the initial [s] in the sentence was significantly longer than that in the middle of the sentence (p<0.01). The maximum contact area for [lc] in [ki] was significantly larger than that in [ku](p<0.01).
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Searching for a Test Food for Evaluating Stability
Ichiro Chiwata, Hiroshi Shiga, Yoshinori Kobayashi
1998 Volume 42 Issue 5 Pages
857-866
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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In order to find the most suitable food for objectively evaluating the stability of masticatory movement, the stability of masticatory rhythm and path of 30 healthy subjects chewing boiled fish paste, chewing gum, gumi-jelly, and peanuts were compared. As a result, it was found that out of the four types of food tested chewing gum had the smallest coefficient of variation values for cycle, occluding, closing and opening times and there was a statistically significant difference between chewing gum and the other three types of food. Further more, it was found that chewing gum had the smallest SD/OD (standard deviation/amount of opening) for lateral component of opening time, lateral component of closing time, and vertical component. Further, from all these indicators it was found that gumi-jelly was the second best indicator. The results suggested that the best type of food for objectively evaluating the stability of masticatory rhythm and path was chewing gum and the next best type of food was gumi-jelly.
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Bond Strengths Measured by Three-Point Bending Test
Ikumi Shiozawa, Takahiro Sato, Minoru Kuriyama, Takehiro Otake, Hideya ...
1998 Volume 42 Issue 5 Pages
867-874
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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This study was conducted to compare bond strengths of three different kinds of dental alloys and one low fusing porcelain (Deguceram Gold, DG) with a fusing temperature around 780°C. The tested alloys were the recommended metal for Golden-Gate-system (Degunorm, DN), a gold-platinum alloy (Casting Gold MC type IV, CG), and a gold-palladium-silver alloy (Castwell MC 12, CW). A conventional metal cerami combination, a gold-platinum-palladium alloy (Degudent-Universal, DU)/VMK 68 was also tested as the control for bond strength.
A uniform thickness of 1 mm of porcelain was applied for an 8 mm in the central portion of metal specimens measuring 25×3×0.5mm. The specimens were subjected to a three-point bending test, and the load of bond failure was recorded. Bond strength (in MPa) was calculated from the load at the porcelain separation.
The debonded metal surface was observed by metal microscopy, SEM, and EPMA to examine the mode of bond failure.
The mean bond strengths of DN/DG, CG/DG, and CW/DG were 50.6, 56.1, and 65.2 MPa respectively, and were compared with the conventional DU/VMK 68 combination (40.4 MPa). Elements from porcelain such as Si, K, and Sn were observed on the debonded metal surface by EPMA. The results suggested that the low-fusing porcelain (DG) not only bonds to the recommended alloy but also to the ordinary dental alloys.
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Psychological Factor
Masako Furuya, Takashi Nokubi
1998 Volume 42 Issue 5 Pages
875-880
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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The purpose of this study was to examine the cause of taste disorders of denture wearers. In this study, the following experiments were performed using fifty subjects of intact dentition and without taste disorders.
After producing the experimental palatal plate, the gustatory responses of primary taste shown by the threshold of judgment were examined with the gustatory test using filter-paper disc. The gustatory test was performed in the following three steps: without the plate, just after insertion of the plate and two weeks after insertion of the plate. The change of the threshold of judgment on the tongue and the soft palate was examined. A questionnaire on the sense of incongruity for the plate was taken. The results were as follows:
1. All fifty subjects felt incongruity to the plate just after insertion, but two weeks later, only nine subjects (18%) felt incongruity.
2. Just after the plate was inserted, the threshold of judgment became higher than that without the plate.
3. In two weeks after insertion of the plate, the threshold of judgment recovered almost to the condition before the inserting the plate.
The results suggested that the change of somaesthetic information by wearing the hard palatal plate would give rise to a psychological contrast of taste.
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Takashi Nokubi, Sakae Yasui, Yuko Edamoto, Tie Kusunoki, Tadashi Nagas ...
1998 Volume 42 Issue 5 Pages
881-885
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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A new method for producing porcelain teeth by pouring muddy porcelain mixed with powder and water in a silicone impression mold, and then pressing and freezing it was developed and reported.
This method has many advantages in comparison to the conventional pile method. This study was conducted to find countermeasures to compensate for the shrinkage of porcelain baked by this method. The right cylinder specimen (10 mm in diameter and 10 mm in height) with a conical concavity (8 mm in diameter and 1.3 mm in depth) on the top was used to examine the dimensional change between the metal model and ten porcelain specimens by a universal material testing machine.
The results were as follows:
In the first and second times using this method, the reproductive coefficient of porcelain was about 84% and 94% of the original model, respectively. The dimensional difference between the baked porcelain and the metal model decreased by using this method two times. It was suggested that the porcelain teeth shaped and baked by using the freezing method could be similar to the original models.
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Hideharu Hibi
1998 Volume 42 Issue 5 Pages
886-887
Published: October 10, 1998
Released on J-STAGE: August 10, 2010
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