Studies undertaken to establish a method for evaluating speech disorders from the standpoint of orofacial articulatory movements of edentulous and cleft palate subjects during the pronunciation of Japanese test sentences, are reviewed.
To form certain speech sounds, the tongue touches various portions of the teeth, the alveolar ridge, and the palate. When these structures are replaced or covered by a prosthetic appliance, proprioceptive feedback may be altered, so that speech articulation is disturbed. In this regard, static palatography and dynamic palatography were used to identify the contact patterns of tongue-to-palate and tongue-to-teeth movements. These methods were applied to determine the degree of misarticulation of cleft palate patients undergoing prosthetic therapy.
To determine the vertical dimension of occlusion (O. V. D.) by phonetic, methods in which the trajec-tories of face markers and the voice can be simultaneously recorded were designed, and the mandibular positions during speech were observed. The time frame during which each consonant was pronounced was identified based on a sound spectrogram. In cases of maxillofacial deformity, the mandibular positions during pronunciation of the test sentences were observed at various O. V. D. s, to predict acceptable occlusion. Further, to assess the speech pattern of edentulous patients, three-dimensional orofacial movements during speech were also observed.
In these studies, real-time speech spectrum analysis was useful to relate orofacial articulatorymovements and time-points for production of consonants in the test sentences.

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A 45-year-old woman with a chief complaint of opening limitation was referred to Iwate Medical University Dental Hospital, in 1994. She reported that intermittent locking in the right temporomandibular joint (TMJ) occurred several times a day, which she managed to unlock by herself. The active opening range was 22 mm between the upper and lower incisal edges during the TMJ locked condition. MR images showed her right TMJ to be in anterior disc displacement with reduction, while the left TMJ showed normal findings. The mandibular position was altered to an anterior therapeutic position of 2 mm in front of the intercuspal position, by use of a removable partial denture (RPD), in 1995. Alternation of the occlusal position maintained the normal disc position, to increase her jaw opening range to as wide as 52 mm. Neither clinical examination nor MR images showed any problems in terms of mandibular function or disc position in 1996. When she lost her RPD in 1997, a second RPD was designed so that the intercuspal position was the same as her present occlusal position. However, her right disc began to displace again in 1998, except this time it was an articular disc displacement without reduction. Although her opening range increased from 28 to 35 mm after pumping manipulation therapy, her right disc stayed displaced without reduction.
Discussion: Since the patient's mandibular positioning when adjusted to the intercuspal position caused a recurrence of disc displacement, the anterior therapeutic position should have been maintained in this patient.
Conclusion: The anterior therapeutic position may be preferable in patients with long-lasting intermittent locking due to anterior disc displacement with reduction.

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Purpose: The purpose of this study was to decrease the burden in both patients and clinicians, and to improve measurement accuracy, in a system to calculate biting forces during clenching from electromyograms of masticatory muscles.
Methods: We first calculated a representative regression formula in all the subjects, and a regression formula of respective integrated electromyograms (I-EMG), and evaluated the error of the calculated values of biting forces. We also attempted to simplify the calculation method. Then, we evaluated the correlation between the coefficient (β) in the regression formula and various related factors, such as the area of the lower denture base, to determine the factors that were related to the coefficient (β) in the regression formula.
Results: The error of the values of biting forces that were calculated from the representative formula in all the subjects, was 32% compared with the actually measured values. Regarding the representative formula of respective I-EMGs, it was shown that the error of the calculated values of biting forces was less than 19% in the subjects with maximum values of I-EMG of less than 6.0μV·s, and less than 25% in the subjects with maximum values of I-EMG of more than 6.0μV·s. The correlation with the coefficient (β) was higher in the order of the buccolingual cross-sectional area of the alveolar ridge in the lower posterior tooth region, the maximum value of I-EMG, the buccolingual width of the alveolar ridge in the lower posterior tooth area, the area of lower jaw denture base, the age of the subject, and mandibular corpus height.
Conclusions: These results suggested that it was necessary to determine the representative formula by classifying the subjects based on the related factors to the coefficient (β) in the regression formula.

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Purpose: To date, many researchers have reported arrangement methods for posterior artificial teeth. However, there are many unclear points concerning the effect of these arrangement methods on denture mobility. The purpose of this study was to obtain complete denture stability. This study was conducted to analyze three-dimensional behavior of lower complete dentures that have two posterior teeth arrangements, by a simulation method.
Methods: We simulated two kinds of lower complete dentures and a mandibular edentulous model. We selected two posterior teeth arrangement methods: one based on the alveolar crest (A-denture), and the other was re-establishing the natural tooth position (N-denture). In a 50 N loading condition to the unilateral occlusal surface by changing the thickness of simulated food and the load position, we measured the displacement of dentures.
Results: 1. In the loading condition to the unilateral, two lower complete dentures moved horizontally-protrusive-outward, the working side sunk, and the balancing side rose, even if we changed the thickness of the simulated food and the load position. 2. The displacement of lower complete dentures was influenced by the posterior teeth arrangement and the load position. The displacement of A-denture was less than that of N-denture, when compared in the difference between arrangement methods.
Conclusions: The results of this study suggested that the mobility of an artificial teeth arrangement method based on the alveolar crest was less than that of a method of re-establishing the natural tooth position.

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Objective: The purpose of this study was to clarify the influence of artificial posterior teeth occlusal configuration for lingualized occlusion, on masticatory function.
Methods: Two males and 4 females completely edentulous subjects were studied. They used complete dentures in which the artificial posterior teeth portion was removable, in order to be able to change it from 30-degree artificial teeth for lingualized occlusion (anatomic teeth) to our department's designed bladed teeth for lingualized occlusion (non-anatomic teeth). Then, masticatory movement and subjective sensations between these two types of artificial teeth were compared. As for test food, boiled fish-pastes, peel peanuts, raw carrots, and pickled Japanese radishes were used.
Results: The masticatory performance observed when boiled fish-pastes were chewed 10 times, was significantly smaller in 30-degree artificial teeth than bladed teeth; however, regarding other test foods, no significant difference was observed. During masticatory movement, the cycle time and occluding time were significantly smaller in bladed teeth than in 30-degree artificial teeth, for all test food used. All subjects could obtain a favorable sensation with bladed teeth, especially while chewing hard foods of raw carrots and pickled Japanese radishes.
Conclusions: The two types of artificial teeth for lingualized occlusion exerted the same masticatory efficiency; however, lower cycle time influence subjective sensations, and our department's designed bladed teeth were particularly effective in the mastication of hard foods.

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Objective: The criteria of the Inter-Coronal Freeway (I. C. F.), which may influence the stability and masticatory function of dentures, have not been clarified. The purpose of this experiment was to study the effect of the I. C. F. on force on dentures when crushing foods.
Methods: We used a simulator for this study, and carrot, pickled radish, boiled fish-paste, and peanuts were selected as the test foods. In each I. C. F., the maximum levels of vertical and horizontal forces (buccal, lingual, anterior, posterior) on dentures when crushing test foods on a simulator, were measured.
Results: Vertical force and horizontal force to the lingual and posterior side decreased with an increase of the I. C. F. in all test foods crushed. Horizontal force to the buccal and anterior side increased with an increase of the I. C. F. in carrot, pickled radish, and boiled fish-paste crushed.
Conclusions: The result of this paper shows that it is necessary to set the amount of the I. C. F. as 1.0 mm to 1.5 mm, in order to decrease the force to dentures when crushing foods. We suggest that an I. C. F. set at 1.0 mm to 1.5 mm is effective in both keeping good denture stability and preserving the alveolar ridge.

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Purpose: The purpose of this study was to clarify the influence of occlusal contact between full balanced occlusion and lingualized occlusion, on food crushing.
Methods: We calculated the impulse of vertical and horizontal components of occlusal contact during simulated crushing of different types of food: raw carrots, peanuts, pickled Japanese radishes and boiled fish paste. We used an experimental denture with full balanced occlusion and lingualized occlusion, testing the model in 3 impulse phases of the vertical component, and 3 impulse phases of the horizontal component, in the buccolingual/anteroposterior directions.
Results: The total impulse on crushing demonstrated by lingualized occlusion resulted in lower impulse levels in all directions for all test foods. On crushing carrots, lingualized occlusion showed lower levels in all crushing phases for all directions. On crushing peanuts, lingualized occlusion showed all lower levels, except for the first phase of the buccolingual direction. On crushing pickled Japanese radishes, lingualized occlusion showed all lower levels, except for the first phase of the buccolingual direction. On crushing boiled fish paste, lingualized occlusion showed lower levels in all crushing phases for all directions.
Conclusion: Lingualized occlusion was effective in food crushing, and the vertical and horizontal components of impulse in lingualized occlusion were smaller than in full balanced occlusion.

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Purpose: The purpose of this study was to assess the effect of occlusal adjustments to wearing complete dentures on the function of mandibular movements and comfort. And this study was to assess the Mandibular Movement-index. Materials and methods: Thirty edentulous patients (11 men and 19 women) with poor denture conditions were selected for this study. The patients answered a questionnaire about comfort (total satisfaction of dentures, stability, eating, speech, appearance and esthetics), pain, and preference region of the dentures for chewing, or the not-preferred region of dentures. Before and after occlusal adjustments, the changes of tapping movements were measured with a BioPAK^® system, and the changes were compared.
Results: 1. An increase of comfort and a decrease of pain were obtained by the occlusal adjustments. 2. The vertical distance of mouth-opening and velocities (opening velocity and closing velocity) of tapping movements were significantly improved. 3. After occlusal adjustments, the Mandibular Movement-index “(vertical distance of opening mouth/cycle time)×100” was increased.
Conclusion: It was importance to inquire of patient about preference region of the dentures for chewing, or the not-preferred region of dentures, because of the not-preferred region of dentures for chewing and premature contact agree approximately. In addition, curative effectiveness of occlusal adjustments are evaluated by a new expression of the Mandibular Movement-index “(vertical distance of opening mouth/cycle time)×100”.

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Purpose: This study was to clarify the relationship between the stability of tapping point and numbers of new denture adjustments in complete denture wearers.
Methods: The subjects consisted of 81 edentulous patients (35 males, 46 females; mean age, 69.2±8.0 years). Tapping point and the Gothic arch were recorded during fabrication of new dentures. The distance between the tapping point and the apex of the Gothic arch, deviate direction of the tapping point and convergence of the tapping point were analyzed. Then we examined the relation to the numbers of denture adjustments.
Results: The average of numbers of denture adjustments was 4.4±1.8 times (males, 3.8 times;females, 4.9 times). The average distance between the apex and the tapping point was 0.8±1.0mm (males, 0.5mm; females, 1.0mm). The deviation direction of the tapping point in 37 patients whose distance between the apex and the tapping point was above 0.6mm, was protrusion in 15 (40.5%) and lateral in 22 (59.5%). Tapping movements were converging in 70 patients (86.4%) and nonconverging in 11 (13.6%). High numbers of denture adjustments increased the distance between the apex and the tapping point to above 0.6mm.
Conclusions: These results suggested that high relations between numbers of denture adjustments and the distance between the tapping point and the apex of the Gothic arch were found in complete denture wearers, and the patients whose distance between the apex and the tapping point was above 0.6mm were increased the numbers of denture adjustments after wear of dentures.

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Purpose: The present report aims to provide some clinical index of human palatal mucosa for stress-bearing ability under the denture base, through the measurement of blood flow.
Method: Blood flow was measured repeatedly 4 times on different days in 9 adults with normal dentition, at each of 47 points on the palate, by using two sets of laser flowmeters. For detailed analysis of the obtained data, the measuring points were classified into 4 portions: central, frontal, lateral, and posterior, according to general anatomical characteristics. The measurements were carried out with or without some compression, such as 0.1 and 0.2 mm, on the palate, by using a specifically designed measuring stent made from a heat-vacuum-formed acrylic sheet and self-curing resin.
Results and Conclusion: 1. Blood flow at rest for the same subject showed good reproducibility in repeated tests on different days. 2. No significant difference in blood flow at rest was observed between the sexes. 3. The blood flow of the palate was smallest at the central portion, and greatest at the frontal portion. 4. The decreasing ratio of blood flow by compression was largest at the central portion, and was followed by, in order of decreasing ratios, frontal, lateral, posterior portions. 5. The decreasing ratio of blood flow was greater at 0.2 mm compression than at 0.1 mm compression.

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Purpose: This study was to investigate the effect of four mandibular major connectors: a lingual bar, a lingual plate, a lingual plate with continuous incisal rests, and it plussed labial hook so that it can be resist the torquing movement, on pressure distribution to the residual ridge under the denture base. This study also sought to determine which could be recommended for long-term clinical service.
Methods: A simulation model was designed to mandibular bilateral distal free-end. When vertical force (294 N) was applied to the experimental denture, the pressure distribution, denture displacement, and strain on the major connector were measured on the simulation model.
Results: 1. In the case of loading on the second molar region, the greatest pressure under both the denture base and the major connectors were observed when a lingual bar was used. 2. Regardless of the major connector designs, the least pressure under the major connector was measured at the loading on the first molar region. 3. The greater displacement occurred in all types of major connectors when the load was applied on the second molar region. 4. The greatest strain and displacement of the denture were observed when a lingual bar was used.
Conclusions: Lingual plate with continuous incisal rests which plussed labial hook indicates minimal displacement and can provide long-term clinical service.

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Purpose: The research investigated marketed hard resins for dental usage as to mechanical properties affected by dipping conditions, and as to glossiness provided by finishing materials. Three candidates: Esthenia, Conquest Thermocrystal, and Art Glass, went through the following tests, for that purpose.
Methods: 1. Dipping Test for Four Mechanical Properties: Compressive Strength, Tensile Strength, Bending Strength, and Vickers Hardness. Condition 1: Each candidate dipped in 37°C water for 24 hours. Condition 2: Dipped in 70°C water for one week. 2. Finishing Material Test for Glossiness. Employed Materials: A. Six kinds of waterproof polishing paper:# 150, 600, 1, 200, 2, 000, 4, 000, 8, 000. B. Silica powdered solution: 0.06μm fine.
Result: The data in Condition 1 were more ideal in each material property compared with Condition 2; Esthenia showed the highest result in each material property, of all the candidates. The test for glossiness indicated two noticeable orders of the candidates: a. Art Glass, Conquest Thermocrystal, and Esthenia, in descending order, qualified by the finishing materials # 150-2, 000. b. Esthenia, Conquest Thermocrystal, and Art Glass, by # 4, 000, 8, 000, and 0.06μm silica solution.
Conclusion: In conclusion, the research showed three results: All the resins showed higher material properties in 37°C water for 24 hours than in 70°C water for one week; Esthenia showed the highest measurement in the dipping test; and the finishing material test showed different glossiness ranks of Esthenia and Art Glass in # 2, 000 or lower and in # 4, 000 or higher of finishing materials.

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Objective: Recently crown and bridge resins containing high concentrations of filler (high-filler resins for crowns and bridges) were developed to achieve high abrasion resistance. The purpose of this experiment was to evaluate the abrasion resistance of high-filler-containing resin for crowns and bridges.
Methods: To evaluate the toothbrush abrasion of resin for crowns and bridges, water absorption, volume of abrasion, abrasion resistance, and surface roughness were determined.
Results: 1. Water absorption was increased in the order of belleGlass HP dentin (BD), belleGlass HP enamel (BE), and Gradia dentin (GD)≅Gradia enamel (GE), (p<0.01, t-test). 2. The amount of abrasion was increased in the order of BE and GE (Enamel Body)(p<0.01, t-test), BD and GD (Dentin Body)(p<0.01, t-test). 3. In evaluation, abrasion resistance was increased in the order of BE, BD, GE and GD. There was a significant difference between BE and GE (BE<GE), and between BD and GE (BD<GE)(p<0.01, t-test). 4. The surface roughness at the end of the experiment was increased in the order of BE, GD, BD, and GE. There was a significant difference between BE and GD (p<0.05, t-test).
Conclusions: The above results indicated that high-filler resins for crowns and bridges had various worn surface and abrasion resistance. We thought that was necessary to evaluate the toothbrush abrasion of resin for crown and bridge more clinical condition.

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Purpose: The reference plane for the face bow transfer will require the natural head position of patient to reproduce the cast situation for articulator. The purpose of this study is to investigate the positional relationship between various reference planes and a cast on an articulator.
Methods: Using cephalograms, we measured the reference coordinate of an angle against the occlusal plane and the cutting margin of the upper central incisors for reference planes in face bow transfer. The reference plane was determined as the arbitrary hinge axis point for the posterior reference point. The anterior reference point was determined as the following 4 planes: 1. The point at 23.3 mm below the inner canthus (C). 2. The midpoint between the inner canthus and the inferior margin of the ala nasi (M). 3. The point at 43 mm above the cutting margin of the upper central incisors (I). 4. The orbital point in the skin (O).
Results: Each level of C, M, and I was similar. The level of 0 was markedly different compared with those of the other 3 planes.
Conclusions: The reference planes in face bow transfer, C, M and I are similar to positional relationship. Then these planes are effective to transfer the cast at the natural head position. But, from a clinical point of view, C is appropriate to transfer at the natural head position.

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Purpose: The purpose of this study was to investigate the effects of laminate mouth guard wearing on balance function, which has been known to be essential to sports participation.
Methods: Gravity fluctuation in the upright posture was determined using the High-Reso Mat System under two conditions: a position of slight occlusal contact with wearing of a laminate mouth guard, and the intercuspal position without wearing the laminate mouth guard. Measurement was made with regard to the standard deviation of lateral components (X-S.D.) and that of anterior-posterior components (Y-S.D.), and also the migration distance of center of gravity. Differences between the two conditions were statistically analyzed using Wilcoxon signed ranks test.
Results: The respective mean values of X-S.D., Y-S.D., and migration distance of center of gravity were 0.21±0.11cm, 0.11±0.05cm, and 10.34±4.25cm in the condition with wearing the laminate mouth guard, and 0.21±0.12cm, 0.10±0.05cm, and 11.74±4.43cm without the laminate mouth guard. Statistical testing revealed no significant differences between the two conditions for any of the measurement items.
Conclusions: These results suggest that static balance functions essential to sports participation are not affected by wearing a laminate mouth guard.

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Purpose: The purpose of this study was to propose criteria for designing a custom-made laminated mouth guard.
Methods: In this paper, nine kinds of sheet materials were used for the experiment. The sheet materials were evaluated as to thickness and water absorption. Furthermore, deformation due to static loading and sheet thickness in various regions before and after forming, were determined.
Results: 1. For all of the sheet materials tested, thickness was almost the same, and these materials were uniform in thickness. 2. The water absorption rate was the maximum for D 20 (Erkodur 2.00mm), and the minimum for F 4 (Erkoflex 4.00mm), and the rates of Es (Essix) and Pr (Pro-form) were similar. 3. The rate of deformation due to static loading was increased in the immersion for Erkodur and decreased for Erkoflex, whereas the rates were not changed for Es and Pr. 4. The rate of reduction in thickness due to forming was 10-20% in the occlusal surface for Erkodur, Erkoflex, and Erkoflex in combination with Erkodur or Erkoflex; however, the rate was 30-46% in other regions. In comparison, for Es and Pr, the rate of reduction was 2-4% in the median palatal tooth surface, and 26-54% in other regions. Conclusions: In this study, water-absorbing capacity of a mouth guard material, and effects of dipping on the hardness of the mouth guard, were investigated, and the thickness of each part of the mouth guard after forming, was determined. The present results provided useful information for design and
construction of custom-made laminated mouth guards.

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Purpose: The purpose of this study was to investigate the influence of mesial inclination of an implant on stress distribution around dental implants.
Method: Two-dimensional finite element models, consisting of a bridge-shaped superstructure, implants, cortical bone, and cancellous bone, were constructed. The distal implant inclined mesially from 0° to 30° and loaded 98 N (10kgf) vertically on 3 points of the occlusal plane. Subsequently, stress distributions were calculated using the finite element method.
Results: 1. In the zero degrees model, highly stressed areas were found on implants, from the loaded point to the rigid connector of the superstructure, cortical bone around implants, cancellous bone around the apex of implants and the surface of the cortical bone among implants. As the mesial inclination of the distal implant increased, stress distribution did not change around the mesial implant but around the distal implant; stress decreased in the apex of the implant and in the rigid connector of the superstructure, and stress increased in the cortical bone around the mesial neck. 2. As the mesial inclination of the distal implant increased, the greatest stress increase in the bone was found around the mesial neck of the distal implant.
Conclusions: 1. It was shown that, as the mesial inclination of the implant is increased, areas that bear the load in the bone change, from cortical bone around the implant and cancellous bone around the apex of the implant, to the inclination side of the bone of the inclined implant. 2. In order to avoid bone resorption, mesial inclination of less than 15° is recommended.

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Purpose: The purpose of this study was to investigate the effectiveness of bone regeneration around bone defects, using absorbable electrified poly-L-lactic acid (PLLA) membrane, and to compare the effectiveness of membrane to Gore-Tex Augmentation material (GTAM®) and non-electrified polylactic acid (PLA) membrane.
Methods: Wistar-strain male rats, of ages 13 to 15 weeks, were used. A hole, 2.0mm in diameter, was drilled in the femoral diaphysis. Group A's experimental site was covered with GTAM®; Group B's was covered with non-electrified PLA; and Groups C's and D's were covered with PLLA membrane (Mw=10×10⁴ or 30×10⁴). The experimental periods were 2 and 4 weeks. Bone specimens were stained with Villanueva bone stain. Microscopic histopathological observations were made.
Results: The PLLA groups showed more accelerated bone growth and bone maturity than did the GTAM® groups in the early stages, especially in the 30×10⁴ Mw group, where a greater amount of bone tissue and increase of maturity was observed. Results of the GTAM® groups were almost the same as the control PLA group, and inferior to the PLLA groups, through all experimental periods. PLLA is easily shaped to fit bone surface to maintain desired space.
Conclusion: PLLA membrane might therefore be used to obtain a better result in clinical application for guided bone regeneration than PLA and/or GTAM®.

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