Purpose: To clarify the effects of molar tooth loss on learning and memory, hippocampal glutamate release during a passive-avoidance task was measured with a telemetric glutamate biosensor.
Methods: Male Sprague-Dawley rats were used. Under general anesthesia, all the maxillary molars were extracted from the EXT group rats (n = 8); those in the CON group (control, n = 8) were anesthetized without tooth extraction. At age 7 weeks, the rats were subjected to a passive-avoidance task consisting of acquisition and retention trials. Simultaneously, hippocampal glutamate release was measured. First, during the acquisition trial, the rats were placed in a light compartment, and the duration before they entered a dark compartment was measured (reaction latency). Immediately after the rat entered the dark compartment, an electric shock was applied through a grid floor. After 24 h, the retention trial was performed, and the reaction latency was measured in the same manner. Further, a biosensor was used to measure the release of hippocampal glutamate before and after the start of each trial.
Results: Regarding the reaction latency during the passive-avoidance task, no significant differences were seen between the groups in the acquisition trial. Reaction latency increased in both groups in the retention trial, but was significantly shorter in the EXT group. Furthermore, hippocampal glutamate release in the acquisition trial was significantly shorter in the EXT group, but in the retention trial, no significant difference in glutamate release was seen between the groups.
Conclusion: Molar tooth loss may impede learning and memory.

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Purpose: The present study aimed to investigate the relationship between subjective oral dryness and stimulated saliva or oral moisture.
Methods: Twenty-one patients with subjective oral dryness (OD) and 21 healthy adults (HA) were enrolled in the study. The Saxon test was performed by chewing a gauze sponge for 2 minutes. Oral moisture was measured at the lingual mucosa (LM) and buccal mucosa (BM) by using an oral moisture checking device. Group differences in the amount of stimulated saliva and oral moisture were compared using the Mann-Whitney U test and Student's t test.
Results: The average amount of salivary secretion in OD and HA in the Saxon test was 0.65 ± 0.55 and 2.34 ± 1.41 g/2 min, respectively; the difference between the groups was significant (p < 0.01). The oral moisture at the LM in OD and HA was 27.2% ± 2.9% and 32.3% ± 1.7%, respectively; this difference was significant (p < 0.01). The oral moisture at the BM in OD and HA was 32.6% ± 2.1% and 34.0% ± 2.2%, respectively; this difference was also significant (p < 0.05).
Conclusion: This study demonstrated that the amount of stimulated saliva became less than 2.00 g and the moisture at the LM became less than 30.0% in patients with subjective oral dryness. These results suggest that stimulated saliva and oral moisture are related to subjective oral dryness; thus, both the Saxon test and the test using an oral moisture checking device are useful for the assessment of subjective oral dryness.

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Purpose: Highly crystalline thin hydroxyapatite (HA) layers deposited on the surface of commercially pure titanium (cpTi) by discharge anodic oxidation and hydrothermal treatment (SA treatment) enhance the value of cpTi as endosseous implants in clinical dentistry. In particular, the SA treatment affects the osteoconductive properties of cpTi. Determining whether this HA layer retains its chemical stability during osseous wound healing is crucial for its use in implants. In this study, we characterized the morphological, chemical, and structural features of HA layers on SA-treated cpTi implants in rat maxilla.
Materials and methods: SA-treated cpTi implants (diameter: 1.0 mm, length: 2.0 mm) were placed in the maxilla of 8-week-old Wistar rats. After 14, 21, and 28 days, the maxilla were harvested and the implant surfaces were analyzed by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and x-ray photoelectron spectroscopy (XPS).
Results: SEM analysis revealed precipitated HA crystals on the implant surface; the crystals had a typical single hexagonal columnar shape and they were highly crystalline. Implantation up to 28 days changed neither the morphology nor the crystalline features of the thin HA layer. EPMA revealed an even distribution of P and Ca in the HA layers before and after implantation in the maxilla, while XPS indicated no change in the binding energies of P and Ca in the HA crystals.
Conclusion: The thin HA layer formed on the SA-treated cpTi implants remained stable during the process of jaw bone formation.

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Purpose: The purpose of the present study was to investigate whether or not abutment tooth support helps to stabilize the overdenture using the dynamics of atmospheric pressure (DAP) as an index of denture stability.
Methods: Experimental dentures for measuring DAP were prepared by indirectly relining duplicates of overdentures used by five subjects (1 male, 4 females). The experimental dentures were relieved at the part of the abutment teeth. These dentures were not supported by the abutment teeth (non tooth-supported overdenture). Those were adjusted and used for 1 week. DAP under non tooth-supported overdenture was measured three times at the center of the palatal plate under experimental conditions with and without food in the mouth. After the measurements, non tooth-supported overdentures were immediately placed in contact with the abutment teeth using an auto-polymerizing resin (tooth-supported overdentures). DAP under tooth-supported overdentures was measured in a similar manner to that under non tooth-supported overdenture. Measurements for the respective experimental dentures were compared.
Results: Under both experimental conditions with and without food in the mouth, the respective patterns of DAP using tooth-supported overdentures and non tooth-supported overdentures were similar. However, the amount of change of atmospheric pressure (AP) was significantly smaller under tooth-supported overdenture than under non tooth-supported overdenture.
Conclusion: It is considered that smaller changes of AP reflect better stability of dentures. Accordingly, the stability of tooth-supported overdenture was superior to that of non tooth-supported overdenture.

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Purpose: The purpose of this study was to elucidate the temporal relationship between habituation to a palate covered by a prosthesis and swallowing function.
Materials and methods: Ten healthy adults were selected as subjects. Tongue pressure on an experimental palatal plate with four pressure sensors was recorded simultaneously with surface electromyography measurements of suprahyoid muscles during swallowing of 3 ml of water. Measurements were performed 6 times: immediately after placement of the experimental palatal plate (Day 0), and on Day 1, Day 3, Day 7, Day 10, and Day 14. Temporal changes were analyzed in terms of the order of EMG activity and tongue pressure, and the duration for total swallowing (DTS), oral preparatory stage (DOPS), oral stage (DOS), and pharyngeal stage (DPS).
Results: Onset of activity of the suprahyoid muscles was observed significantly earlier in all regions compared to onset of tongue pressure. Onset of tongue pressure in the posterior region was significantly delayed compared to onset of tongue pressure in another region. These results remained constant over the measurement period. DTS and DOS were significantly shortened on and after Days 3 and 7, respectively, compared to the respective values on Day 0. DOPS was significantly shortened on Day 7, compared to Day 0 and 1. DPS showed no significant change over time.
Conclusion: The time required for swallowing shows a tendency to decrease over time as a subject becomes accustomed to a palate covering. This was mainly due to shortening of the oral stage.

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The purpose of this study was to clarify the curricular structure, techniques, and materials used in predoctoral prosthodontic programs of Japanese dental schools. A survey of dental schools was conducted by the education committee of the Japan Prosthodontic Society in 2007. The questionnaire was mailed to the chairperson of the prosthodontic departments of 29 dental schools in Japan. Of these, 28 schools returned the completed survey, resulting in a response rate of 96.6%. Results from this survey show that a large majority of schools are using a similar curricular structure in pre-clinical clerkship programs; for instance, the mean number of laboratory hours is approximately twice as long as that of lecture hours. Total hours spent on fixed prosthodontics was the longest, followed by removable partial denture prosthodontics, and then complete denture prosthodontics. The clinical clerkship programs varied considerably from school to school, and in some schools, the opportunities for dental students are very limited. Conclusion: Predoctoral clinical prosthodontic programs vary from school to school, yet a large percentage of schools agree on many topics.

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One of the prominent roles of the occlusion would be to support the force balance wobbling in stomatognathic system, thus pacing and minimizing the change of force distribution with age. Patient's demands on the prosthetic treatment have been becoming higher and more complicated during the past several decades. These demands include not only the precise restoration of the decayed tooth but also the treatment to provide stable and comfortable state of the stomatognathic system in the longer term. These demands would deeply be related to ; 1) How to finalize the information on temporary or treatment prosthesis, which has the resulted shape of the precise functional adjustment, on the final prosthesis, and 2) How to cope with the persistent complaints regarding tooth, tongue and other related sensations. In these aspects, patient's subjectivity and/or esthesis might need to be satisfied with the form and/or function of the resulted prosthesis. The clinical difficulties might be related to the following two points, which are 1) the accuracy of the reproduction procedure from the treatment prosthesis to the final one and 2) stability of the mandibular position or the condylar position which support the functional basis for the prosthesis. In order to cope with the complicated requirements, we have been using double-casting method for providing cast restorations. This is a method to produce a cast restoration in two functional parts. The first casting step consists of a base-crown which covers the abutment tooth and adjacent proximal contact point(s). The second step is the molding of the functionally required occlusal form onto the base-crown. The third step is the metal casting onto the base-crown replacing the molded portion. This method could be applied in various situations where we are forced to match the function and the form. The purpose of this paper is to provide a good orientation to the double-casting method and also to discuss the concept that might pace and minimize the change of force distribution in stomatognathic system.

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The principle of dental treatment focuses on to achieve a good balance between “maintaining the residual tissues in healthy condition” and “the functional recoveries”. At first, the two major prerequisite for the residual tissues maintenance are bacterial control and mechanical loading force control, through pre-operative microbial test, and examinations and diagnostics of residual tissues such as temporomandibular joint, muscular groups, existing teeth, periodontal tissues, and residual ridges. Secondly, the functional recoveries are to increase the rate to the utmost of various functions of stomatognathic system as mastication, swallowing, respiration pronunciation and sensation, including aesthetics.

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The objective of this study was to observe what influences the differences in implant systems and their configuration and conditions at insertion of implant would cause in change of soft tissue over time after setting of crown, and consequently to clarify what type of clinical treatment should be applied in order to minimize invasion to patients as well as achieve maximum results. This study was conducted through implant-prosthetic treatments with the cases of single tooth loss in maxillary anterior area. The lengths of clinical crown were measured both at the time of setting crown and after follow-up of 4.5 years in average. Used were 60 implants, composed of 26 of Tapered Screw-Vent, 22 of Straumann and 12 of Ankylos. In the cases with Ankylos, whose configuration is of platform switching, the clinical crowns turned out to have got longer only by 0.3mm, while that with Tapered Screw-Vent by 1.1mm and that with Straumann by 1.3mm.
Furthermore, the cases with Tapered Screw-Vent were divided into 2 groups according to the conditions of insertion. One group was that the implants were inserted at an angle to the axis of natural teeth and on the labial side, and the other was that the implants were inserted vertically and on the palatal side. The variations were 1.9mm longer in the former group and 0.3mm in the latter respectively. The results obtained, in spite of the use of one implant system, varied according to the seating conditions, and with the cases with Tapered Screw-Vent seated vertically, the variation of soft tissue was as quite small as the cases with Ankylos. It indicates that a choice of appropriate implant system and the consideration about the conditions of implant insertion are significant in order to maintain satisfactory long-term esthetic results.

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The innovation and development of dental materials have radically changed modern restorative dentistry. The pace of development and progress has been unexpectedly rapid for dentists and dental technicians. In addition, patients now expect a higher level of esthetic restorative treatment because of information from the media and other sources. While these developments are positive, they also possess a certain element of danger. In other words, it is Possible to twist the essence of treatment into an excessive quest for esthetics. It is an axiomatic truth that esthetic restorative treatment cannot be called a real restorative treatment if it does not consider function, structural mechanics, and biology. With this in mind, it is important to establish the clinical basis for esthetic restorative treatment. At the same time, the more complicated and difficult the clinical cases become, the more cooperation with specialty fields such as orthodontics, periodontics, and implant dentistry will be needed at each clinical stage. Thus, the key to the success of a more refined esthetic restorative treatment is a minute and detailed discussion with these various specialists about diagnostic treatment planning. This article presents the author's interpretation of kay's classification of altered dental esthetics,1 along with an original way of classifying the cases. It also describes the latest dental materials and their usage.

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Purpose: To compare oral health-related quality of life (OHRQoL) with patients who requested implant treatment and conventional denture treatment.
Materials and methods: Data were collected by means of self-administered questionnaire during July 2004-January 2005 at four dental offices located in Japan. Subjects who requested implant treatment (IT) were 12, and requested conventional denture treatment (DT) were 19. OHRQoL was measured by the 16-item Oral Health Impact Profile (OHIP-JP16). The OHIP-JP16 total and subscale scores were calculated by summing the 16 items score without weighting. The mean OHIP-JP16 total scores and the mean scores of six subscales (functional limitation, physical discomfort, psychological discomfort, physical disability, psychological disability, handicap) between groups were analyzed by the Mann-Whitney U-test. Chi square tests were used compare responses to individual items. ‘Never’ and ‘hardly ever,’ (no impact) were recorded as ‘0’, ‘occasionally’, ‘fairly often’, and ‘very often’ (any impact) were recorded as ‘1’.
Results: The mean age was 62.4 years old in IT and 66.6 years old in DT (p=0.596). No differences in denture status, self-perceived oral health, number of teeth were found between two groups. DT subjects had better OHIP-JP16 total scores than IT, but it was not statistically significant (p>0.05). Chi square tests were performed for each of 16 items. The number of subject reported ‘any impact’ was significantly greater (p<0.05) in IT in the following items; ‘worried’, ‘self-conscious’, ‘avoid eating’, ‘upset’ and ‘life unsatisfactory’. No significant differences were detected in the following 5 subscales; ‘functional limitation’, ‘psychological discomfort’, ‘physical disability’ , ‘psychological disability’ and ‘handicap’, while ‘physical discomfort’ was signify- cantly lower (e.g. higher QOL status) in DT.
Conclusion: OHIP-JP16 scores of the subjects who requested implant treatment were significantly higher in ‘physical discomfort’ than requested conventional denture. The results of this study suggested that in the patients who requested implant treatment, OHRQoL might be lower than the patients who requested conventional denture treatment.

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The aim of this study was to compare different methods for effective adhesion between a glass fiber-reinforced composite (FRC) material for framework and a veneering composite (VC) material for coating framework when fabricating clasps (FRC clasp (with VC)). Vectris pontic and EG fiber were used as FRC materials, the glass fibers of which were preimpregnated with resin. Palfique estelite LV was used as the VC material.
Laminate specimens were fabricated by coating FRC with VC (Palfique⁄Vectris, Palfique⁄EG fiber). Five adhesion methods were used when coating the framework. Three specimens were prepared for each adhesion methods. Deflection and load when VC cracked were examined using the three-point flexural test. The mean and S.D. of each value were calculated and subjected to two-way analysis of variance (ANOVA) and multiple comparisons (Bonferroni⁄ Dunn) to determine the significance of the differences (P = 0.05 and 0.01) between the results of the respective methods.
The deflection of Palfique⁄Vectris and Palfique⁄EG fiber was 0.497-0.631 and 0.426-0.481 mm, respectively, the load of which was 92.33-108.00 and 60.17-72.50 N, respectively. The deflection and load under all adhesion methods were significantly higher in Palfique⁄Vectris than Palfique⁄EG fiber (P<0.01). In Palfique⁄Vectris, deflection under non-adhesion was significantly lower than under others, but there were no significant differences among loads in different adhesion methods. In Palfique⁄EG fiber, there were no significant differences among deflections and loads in all adhesion methods.
In the present study, the results suggested that sandblasting could be effective to increase the amount of deflection causing VC cracking in a clasp arm.

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This study investigated the present status of specialized dental treatment that was sought on the Internet by people in Japan and the United States. Searches on Yahoo! Japan and Yahoo! America were performed using “dental clinic” and specific specialties, for example, sports dentistry, orthodontics, periodontics, dental implant, as keywords. The magnitude of search results progressed in the order of sports dentistry, orthodontics, dental implant, and others in Japan. In the United States, the order of search results was oral surgery, sports dentistry, dental implant, and others. Regarding combinations of specialties, the most frequent found combination was dental implant and cosmetic dentistry in Japan. In the United States, it was a combination of cosmetic dentistry and sports dentistry. These findings showed that people were frequently interested in sports dentistry, cosmetic dentistry and dental implants in both countries. It is necessary to display these specialties on the dental clinic homepage in order to attract the interest of potentials in both countries.

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The purpose of this study was to investigate the mechanical risk factors of All-on-4 system by analyzing the stress distribution induced on implants and surrounding bone tissue using a 3-dimensional finite element method (3D-FEM). The effects of bone quality and superstructure material property were also investigated.
A 3D-FEM model of an edentulous mandible was constructed from computerized tomographic images. The two anterior-most implants were placed in the right and left lateral incisor areas. Two additional implants were placed anterior to the mental foramen with a distal inclination of 40 degrees to the occlusal plane. The 3D-FEM All-on-4 model included a fixed mandibular complete-arch superstructure supported by four implants. Four types of bone (1 to 4) were simulated by varying the Young's modulus for cancellous bone. In addition, three superstructure materials were prepared: acrylic resin, gold alloy, and Co-Cr alloy. A 100 N load was applied on the left first molar region. Stress concentration was observed around the left posterior inclined implants, especially on the distal side. When the cancellous bone is low elastic, greater stress concentration was observed. Of the three materials, the acrylic resin superstructure showed the greatest stress concentration around the inclined implant.
The present study indicated that the use of the superstructure with higher elastic material is useful for reducing the mechanical risk of All-on-4 system.

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The purpose of this study was a clinical evaluation of injectable dental ceramic restorations. In this study, Ceraeste system based on Diopside was used for injectable dental ceramics. Ninty two injectable ceramic restorations were investigated in 36 patients by a questionnaire survey performed from December 7th, 2001 to July 7th, 2004. The mean service time of the restorations was 18 months. One crown on a mandibular first molar was fractured. It was concluded that new injectable glass-ceramic restorations are suitable for clinical use, although not totally without problem, especially with survival rate of the injectable glass-ceramics, which might be shorter than the other restorations. These findings should be investigated sequentially.

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Purpose: All-ceramic restorations are widely used in esthetic dentistry. Various materials have been used to improve ceramic core strength, but it is unclear whether they affect the opacity of all-ceramic systems. The aim of this study was to compare the translucency of 9 all-ceramic system core materials at clinically appropriate thickness.
Materials and methods: A 360-degree round deep chamfer preparation for the all-ceramic crown was made for a maxillary right first molar tooth as the dental model. Coping of 0.5mm thickness were fabricated by Empress Esthetic (ETC1, EOC1, EO1, EO2), Empress2 (50) (IVOCLAR VIVADENT), Procera AllCeram, Procera AllZirkon (Nobel Biocare), LAVA (3M ESPE), and DentaCAD Systeme (Hint-Els). Abutments were made by black wax and white wax. Spectrophotometric measurements were made by a spectrophotometer. The final color of the central part of the buccal surface was measured and the L*a*b* color space was used to obtain the color values. Contrast ratios were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white (Yw) backing to give Yb⁄Yw with CIE illuminant D65 and 2-degree observer function (0.0=transparent, 1.0=opaque).
Results: Contrast ratio in order of most translucent to most opaque were as follows: EO2 .41, EO1 .43, ETC1 .43 , EOC1 .44, Empress2 .50, AllCeram .63, AllZirkon .74, LAVA .76, DentaCAD.80. There was no significant difference(p<.05) between the AllZirkon, LAVA, DentaCAD or ETC1, EOC1, EO1, EO2.
Conclusion: Within the limitations of this in-vitro study on 9 all-ceramic core systems, a significant range of translucency was identified across specimen groups.

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Recently, several fiber-reinforced plastic (FRP) posts have been applied for abutment build up; however, it is still unclear what type of build up is preferable for a funnel-shaped root canal. The purpose of this study was to evaluate the effect of a new abutment build-up method which combined an FRP post and metal core for a funnel-shaped root canal.
As the tooth for abutment build up, an epoxy artificial maxillary lateral incisor was used. The artificial tooth was cut in the cervix part and a funnel-shaped root canal was formed in the root. As the materials for abutment build up, a glass fiber-reinforced plastic post, core resin and gold-silver-palladium alloy were used. Abutment build up was performed using the following three methods: 1. Combination of an FRP post and core resin by the direct method (FP); 2. Conventional metal core by casting (MC); 3. Combination of an FRP post, core resin and coronal metal core (FM). In addition, as a control, an artificial tooth prepared for abutment (ET) was used. A destruction test was carried out to measure the destruction strength and observe the destruction aspect.
The destruction strength of FP was about 160N, significantly lower than that of MC, FM and ET. The destruction strength of FM showed the highest value of about 240N, but there was no significant difference among those of MC, FM and ET. When observing the specimen after the destruction test, FP, FM and ET were fractured or cracked near the cervix of the tooth, whereas MC was fractured near the center of the root.

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In the present study, we assessed the effects of commercially pure titanium (cpTi) by anodic oxidation and hydrothermal treatment (SA-treated cpTi) on osteoblastic differentiation and interfacial bone formation through parallel in vitro and in vivo investigations. Osteoblast cells were cultured on SA-treated cpTi disks for 5, 7, 10, and 14 days. Bone matrix mineralization was assessed by EPMA. The levels of collagen I, alkaline phosphatase, osteocalcin, osteopontin, bone sialoprotein, and β-actin mRNA were analyzed using RT-PCR. In addition, SA-treated cpTi implants were placed in the mandibles of beagles for 14 days, and then examined histologically by light microscopy. Widespread Ca and P signals were observed early in the in vitro culturing period, and mRNA expression was up-regulated in cells that were in contact with the SA-treated cpTi. The bone-to-implant contact formed at the mandible SA-treated cpTi implant sites involved direct contact of the implant with the surrounding bone tissue. These results demonstrate the potential of SA-treated cpTi surfaces for enhancing surface-specific expression of osteoblastic phenotypes and for inducing changes in bone matrix gene expression.

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Objectives: The purpose of this study was to determine the mechanically appropriate retainer design for unilateral distal-extension removable dentures.
Methods: Two models were constructed, each with a different design of retainer placed on the first and second mandibular premolars. Each model was composed of bone, denture underlying mucosa, retainer and denture base. In design A, Akers clasps were set on the first and second premolars, and in design B, an occlusal rest and back-action clasp with mesial rest were set on the first and second premolars, respectively. Loading on the occlusal surface of the denture was performed in the vertical and oblique directions. Load on the abutment tooth and displacement of the denture base were determined by 3-dimensional finite element analysis.
Results: Load on the abutment tooth in the vertical direction caused by vertical loading on the denture was lower in design B than in design A. No large difference in displacement of the denture base was observed between design A and B. Load on the abutment tooth both in the vertical and buccolingual direction induced by loading on the denture in the lingual and buccal directions was lower in design B than in design A. However, displacement of the denture base in the vertical and buccolingual directions induced by loading on the denture in the lingual direction was higher in design B than in design A.
Conclusion: In this study, displacement of the denture base was smaller in design A than in design B, so design A would be more useful clinically than design B, but the abutment tooth would require greater support.

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Severe speech difficulty is often caused after surgery for oral cancer. Prosthetic treatment with a removable obturator prosthesis is generally provided for such patients. To evaluate speech ability objectively, a speech intelligibility test has been used. In the previous report, the authors showed that measuring electrical resistance changes of skin caused by electrodermal response (galvanic skin response: GSR) during speech could be a useful method for assessing speech dissatisfaction of patients after oral cancer surgery; however, it is not clear that GSR can reflect the severity of speech disability. In the present study, the score obtained from evaluation methods for speech dissatisfaction using the GSR of maxillectomy patients was compared with speech intelligibility test and visual analogue scale (VAS) scores for speech satisfaction. A low correlation coefficient was observed between VAS improvement score and each of the two other scores (GSR improvement and speech intelligibility improvement scores). High correlation was observed between speech intelligibility improvement and GSR improvement scores. From these results, it is suggested that measuring electrical resistance change of skin during speech could reflect the severity of speech disability after oral cancer surgery.

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The aim of this study was to investigate the influence of the measurement condition on the measurement value of an oral moisture checking device. Healthy adults were enrolled to investigate the influence of repeating measurement, rinsing, and measurement time. Oral moisture was measured at the lingual (LM) and buccal mucosa (BM) using the oral moisture checking device. The statistical analysis (Friedman test) was performed to compare the moisture of 3 times' repeating measurement, and the moisture just after rinsing, 3, and 5 minutes after rinsing, and the moisture according to measurement time (at 9:00, and 11:00 a.m., and at 1:00, 3:00, and 5:00 p.m.). As the results of the repeating measurement, there were significant difference between the measurement value at LM of the first time and third time measurement, second time and third time measurement (p<0.01), and the first time and second time measurement (p<0.05). As the results of rinsing, statistically significant difference was found between the measurement value at LM just after rinsing and 5 minutes after rinsing, and 3 minutes after rinsing and 5 minutes after rinsing (p<0.01). There was not significant difference among the measurement time. The results of this study demonstrated that the measurement value increased at LM by repeating measurement and increased at 5 minutes after rinsing, and wasn't influenced by measurement time. It was suggested that practicing the measurement using an oral moisture checking device was necessary, and the measurement could be performed at any time.

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The purpose of this experiment was to clarify relations among temporomandibular disorders (TMDs), bruxism, lifestyle, and psychological stress. Participants were selected from female patients (n=29, 23-78 yrs, mean age 50.8 yrs).Eighteen females were diagnosed as having TMD (TMD group, mean age 47.6 yrs), and 11 females were diagnosed as not having TMD (Non-TMD group, mean age 55.9 yrs). All participants underwent self-administered questionnaires which consisted of the Health Practice Index (HPI), the Tokai University Type A Pattern Scale, the 28-item General Health Questionnaire (GHQ-28), and the Zung Self-Rating Depression Scale (Zung-SDS). They were instructed to sleep at home with the disposable sleep bruxism sensor (BiteStrip®, S.L.P.) attached on their left masseter. The number of bruxers was significantly higher in the TMD group than in the Non-TMD group (P<.05), which suggested an association between bruxism and TMD. Based on BiteStrip score, participants were divided into bruxers and non-bruxers. In Non-TMD groups there was significant difference only in lifestyle, especially sleep and mental stress between bruxers and non-bruxers (P<.05). Bruxers showed higher anxiety and insomnia score than non-bruxers. Bruxism in the Non-TMD group was associated with lifestyle, especially with sleeping hours and mental stress. This suggests that an improvement in lifestyle might reduce bruxism events in the Non-TMD group.

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The purpose of this study was to investigate whether the area and weight of removable dentures could influence patients' satisfaction with their dentures. The weight and area (projected area on occlusal plane) of 37 maxillary removable resin-based dentures fabricated in Okayama University Hospital were measured. Full consent from all of the denture users examined in this study was obtained prior to the test. Examination of the visual analogue scale (VAS) for denture satisfaction (0-100%) was performed for 13 users of these dentures. Statistical correlation between the denture areas and the number of missing teeth, and between denture weights and the number of missing teeth was examined. Statistical correlation between the VAS satisfaction level for dentures and the area⁄number of missing teeth, and between the VAS satisfaction level for dentures and the weight⁄number of missing teeth was also examined. A positive correlation was observed between the area of the denture base and the number of missing teeth (r = 0.854, p<0.001). A positive correlation was also observed between denture weight and the number of missing teeth (r = 0.842, p<0.001). According to the increase of the number of missing teeth, the area and weight of dentures increased. Therefore, the statistical level was estimated by dividing area and weight by the number of missing teeth. Positive correlation was observed between the VAS satisfaction level and the area⁄number of missing teeth (r = 0.645, p=0.017); in contrast, no statistical correlation was observed between the VAS satisfaction level and the weight⁄number of missing teeth. A positive correlation was observed between patients' satisfaction and area of the denture base⁄number of missing teeth. Patients' satisfaction with removable maxillary dentures did not depend merely on decreasing the size of the denture base.

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The purpose of this study was to establish a noninvasive method of evaluating swallowing function using swallowing sounds. Four handicapped patients with congenital or postnatal dysphagia were selected as subjects and five healthy, fully dentate males were selected as control subjects. A jelly on the market for the elderly in need of nursing care was used as the test food. Ultra-sound diagnostic equipment and a heart-sound microphone were used to record tongue movements and swallowing sounds. Moreover, an endoscope was used to observe the bolus and larynx. In all healthy subjects, the first swallowing sound before endoscopic whiteout and the second swallowing sound after endoscopic whiteout were detected in the swallowing test. On the other hand, in all subjects with dysphagia, the first swallowing sound and endoscopic whiteout were detected. However the second swallowing sound was not detected clearly in the 3 subjects with congenital dysphagia. Waveforms of an unclear first swallowing sound or second swallowing sound were observed repeatedly in the subject with postnatal dysphagia. A part of the bolus aspirated into the trachea upon inspiration made some patients choke and cough. Our findings suggest that the bolus remaining around the epiglottis contributes to an increased risk of aspiration and that observation of the second swallowing sound may be effective in the evaluation of swallowing function.

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Objective measurement of pain may be useful for dental diagnosis and therapy. The purpose of this study is to measure reactions to pain in the cerebral cortex during dental treatment using NIRS (Near Infrared Spectroscopy), and to assess potential applications of this measuring system in the field of dentistry. Oxygen exchange in the cerebral cortex (oxygenated Hb, deoxygenated Hb and total Hb) was measured to indicate brain function, with and without pain. Also, measured data were mapped using a COE (Cerebral functional mapping of Oxygen Exchange) system. We obtained the following results: (1) reactions in the cerebral cortex apparently related to dental pain were measured, (2) these reactions varied associated with the degree of pain, (3) these measurement responses were quick and reactions could be shown within a few seconds during an event, and (4) the reactions also disappeared quickly after the pain disappeared. The results of this research indicated that this measuring system of brain function has a high potential for use in dentistry.

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We developed an ambulatory bruxism recording system that analyzes sleep stage. This system enables us to measure sleep bruxism activities in each sleep stage on an electromyographic and auditory basis at home. The purpose of this study was to examine the usability of this recording system. Six volunteers with self-awareness of sleep bruxism were recruited. They were instructed to operate the recording system by themselves and they recorded their bruxism activities at home. Afterward, they were asked to answer the questionnaire on the usability and the influence of the device on sleep. Data recordings were carried out in 3 to 5 nights per subject. All subjects could easily operate this system. Two subjects, however, failed to record in some nights. They reported problems of the sensors falling off from the skin. There was no complaint on disturbance of sleep due to the measurement. Although no interference to sleep was observed, our ambulatory recording system caused some technical difficulty in a few subjects. More detailed operation manual and simplified software seemed to be necessary.

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Denture wearers often claim an alteration of taste and oral senses. There are many sensory spots on the hard palate but not taste receptors, so a palatal appliance does not cover taste receptors. Thus, the causes of these claims are not fully understood. In this experiment, we examined the effects of an experimental palatal appliance on taste and form discrimination ability. We took maxillary impressions and made a palatal appliance of acrylic resin. The subjects were seven healthy women (aged 21 to 25). They were divided randomly into two groups and the following two experiments were performed. Experiment 1: we checked the taste threshold for four basic taste stimuli (sucrose, NaCl, acetic acid, and hydrochloric acid quinine) by means of the whole mouth test and filter paper-disk method. Experiment 2: we examined their form discrimination ability. For form discrimination ability, we prepared test blocks of four forms of different sizes. Volunteers were asked to put one of the blocks into their mouth, and to identify the form of the block. There was no significant difference in the taste threshold whether they were wearing a palatal appliance or not. In form discrimination ability, there was no significant difference between subjects with and without a palatal appliance. The insertion of a palatal appliance causes few, if any, changes in oral senses. This study suggests that the alteration of oral senses after wearing dentures may be due to mental factors, the contact of food and oral mucosa, and the flow, flavor, and temperature of food and so on.

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Bruxism is a very common parafunction of the masticatory system. Currently, there is consensus about the multifactorial nature of the etiology of bruxism, and it is thought to be a central nervous system phenomenon related to stress and pain behavior rather than structural components. The relationship of bruxism and subjective stress has remained unclear. Recently, biomarkers have been used for assessing stress reaction such as chromogranin A (CgA) and cortisol. The level of CgA provides a sensitive and reliable index for evaluating psychological stress. We can have many reports about plasma CgA, but we can't have enough reports about salivary CgA. The aim of this study was to clarify circadian variation CgA in saliva. Four adults (1 male, 3 females) participated in this research. Subjects provided ten saliva samples. Saliva samples were collected in the morning (9 am) and in the night (21 pm), and every 3 h for 24 h. In addition, saliva samples were two-minute stimulated and unstimulated samples to measure CgA concentration, major salivary stress biomarkers. Unstimulated salivary CgA concentration varied more in time and individual difference than stimulated. Stimulated salivary CgA concentration was increased from 12 pm to 18 pm. Salivary CgA seemed to have a circadian variation with peak in the afternoon-night period and a nadir in the noon. With regard to circadian variations, salivary CgA concentrations, in particular stimulated saliva, hardly differ from plasma CgA. It was concerned that CgA concentration was influenced from a lot of factors.

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A review of the statistics and outcomes related to the use of titanium dentures used at the Tsurumi University Dental Hospital between 1992 and 1998 was previously reported. This report contains details of the evaluation of the use of titanium dentures between 1999 and 2007.
The patients were partially or completely edentulous individuals who received prosthodontic treatment, including cast partial or complete dentures, at the Tsurumi University Department of Removable Prosthodontics between 1999 and 2007. According to the laboratory instructions at the Tsurumi University Dental Laboratory Center, the denture frameworks were classified as partial (PD) or complete (CD) and fabricated from commercially pure titanium (CPTi), a titanium alloy (Ti Alloy), a cobalt-chromium alloy (Co-Cr), and a Type IV gold alloy (Au-Pt).
From April 1999 to March 2007, we prepared a total of 1,470 cast metal plate dentures, 295 (20.1%) of which were made with titanium. CP Ti (Grade 3) dentures were used in 263 patients (17.9%), and Ti Alloy (Ti-6Al-7Nb) dentures were used in 32 (2.2%). The majority of the cast plates were made with Co-Cr (995, 67.7%). CP Ti is well known to be softer and more prone to wear than Ti-6Al-7Nb but is frequently used for the preparation of partial dentures at our University because of its high biocompatibility.
CP titanium is favorable because it rarely results in metal allergy, and is lightweight.

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Purpose: The aims of using denture adhesives are to provide denture-wearers with improved fit and comfort of their dentures and to improve their chewing ability and confidence. However, there have been few reports on denture-wearers who regularly use denture adhesives, especially among maxillofacial patients. The objective of the present study was to evaluate the usefulness of a denture adhesive in a maxillectomy patient.
Materials and methods: The subject investigated in the present study was a maxillectomy patient who had undergone surgical resection and radiotherapy. After delivery of a new dento-maxillary prosthesis, we investigated his speech and masticatory functions objectively using a speech intelligibility test and mixing ability test, respectively.
Results: In the speech intelligibility test, the score changed from 22.3% without the prosthesis to reasonable scores of 83.7% with the prosthesis alone and 84.7% with the prosthesis plus the denture adhesive. In the mixing ability test, the score changed from being immeasurable without the prosthesis to scores of -0.48 with the prosthesis alone and 0.10 with the prosthesis plus the denture adhesive.
Conclusion: Use of the denture adhesive led a marked improvement of the masticatory function.

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The purpose of this study was to make plaster block using 3-dimensional system based on a hypothetical hexahedron model, measure the accuracy of them, and apply to make a mandible model for implant treatment. The application to the mandible model was suggested by measuring the accuracy of the made hexahedron model, and having obtained an excellent result.
On assumption of a hexahedron model, 20 x 30 x 40 mm on computer, data was input into the 3-dimensional system so that three different-sized hexahedron models were set by changing the size of base (x-axis and y-axis). A rectangular plaster block was prepared based on the output using 3-dimensional high-speed inkjet printer. Three lengths (x, y and z) of the hexahedron model were determined and compared with those of input data.
Each length of x-, y- and z-axis was examined for the three different plaster blocks prepared. The size difference in the horizontal direction (x- and y-axis) was not significant, but that in vertical direction (z-axis) was significant.
Although the size of plaster block was slightly larger in the vertical direction, we succeeded to prepare a jaw mold of almost the same size as the real one. The plaster jaw mold, which was prepared through output of imaging data obtained using 3-dimensional construction system for CT was in almost the actual size and able to directly look at a jaw from any angle, suggesting that the jaw mold was useful for choice of implant procedure and simulation of operation. Moreover, this would smoothly lead to patient's informed consent. These findings indicate that a plaster model constructed using CT would be very useful for implant treatments.

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Purpose: This study investigated the inhibitory effect of acrylic resin incorporating FAp-TiO₂ against the adhesion of C. albicans.
Materials and methods: FAp-TiO₂ was added at 1, 5, 10 wt% to acrylic resin to form specimen disks of 7 mm diameter, and the surface roughness was measured. Then, C. albicans was cultured aerobically at 37 °C for 24 hours in glucose peptone yeast extract (GPY) broth, and adjusted to OD=1 at 550 nm with a KCl-buffer. The disks were immersed in the C. albicans suspension for 2 hours at 37 °C with UVA from a black light source. After the incubation, the disks were washed gently with phosphate buffer saline (PBS), and the luminescent signal derived from the viable cells on the disks was determined using a bioluminescence adenosine triphosphate (ATP) assay.
Results: In the measurement of surface roughness, no significant difference was observed between any of the specimens. The adhesion assay of C. albicans revealed that a statistically significant decrease was observed in FAp-TiO₂ when compared with the control (p‹0.01).
Conclusion: We suggest that acrylic resin incorporating FAp-TiO₂ prevents the adhesion of C. albicans, indicating a wide range of possibilities for the practical use of new photocatalysts in acrylic resin.

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The purpose of this study was to determine the relationship between subjective discomfort⁄difficulty in function after insertion of a palatal bar and location of the bar. Also, the effect of palatal depth was examined. Thirty-four healthy subjects were asked to rate 3 types of bar (anterior, middle, and posterior bar) for 5 items representing various aspects of discomfort and subjective difficulty in function immediately after the insertion of each bar appliance. The palatal depth in anterior, middle and posterior regions was measured for each subject; and the relationship between the rated scores and palatal depth was investigated. In addition, in 12 of the 34 subjects, these palatal bars were inserted; and the score of each item was determined immediately and 3 days after the insertion. The posterior bar showed the highest scores for all items. The anterior bar showed a higher score on the item related to speech, but a lower score on the item related to chewing than did the middle one. The subjects with their palate being deeper at the middle region and shallower at the posterior showed a significantly lower score on the item related to speech than those with a palate deeper at the middle and posterior regions. By 3 days after the insertion of the middle bar, the scores significantly decreased for most of items. Our data suggest that the depth of palate both at the middle and at the posterior region have an influence on the subjective difficulty in speech immediately after the insertion.

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The purpose of this study was to compare the response to the treatment of TMD in the two major groups of TMD disc disorders. 80 subjects with disc disorders with reduction who were treated only with behavioral modification and exercise were compared with 30 disc disorder patients as previously reported.¹ Data gathered during the examination period was compared with the data after symptom were stabilized. First examination data included the TMD question and answer form, CMI test, and ordinary oral examination data. During the treatment duration, some of the data showed a significant correlation. However, no valid multivariate prediction formula for estimating treatment duration was seen. In the amount of mouth opening, two groups of TMD patients demonstrated different correlations between tenderness sites and amount of mouth opening. Tenderness of anterior temporalis at start of the treatment correlated with treatment duration and mouth opening at the end of the treatment. In patients without reduction group, more tenderness was shown. Result of this study showed that two group of TMD patients may have different responses to the TMD treatment.

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Generally, although the mandible is considered to be fixed during body movement, its dynamics have not been clarified. In this study, we investigated the condylar movement pattern in extension⁄flexion movement of the body trunk. Six healthy dentulous subjects performed extension⁄flexion movement of the body trunk using a multipurpose muscle function training system. The condylar and incisal point movement patterns were measured using a jaw movement analyzer and 3D ultrasonic navigator. The maximum displacements of the condylar and incisal points in the mouth opening were measured. The relative percentages of condylar point displacements in extension⁄flexion of the body trunk to the maximum displacements were calculated, and displacements in the anterior, and posterior, superior, and inferior directions were compared. The condylar point displacements in the anterior, posterior, superior, and inferior directions in extension⁄flexion of the body trunk were 8.1%, 30.1%, 73.2%, and 10.7% on the right side and 5.8%, 55.1%, 31.3%, and 13.0% on the left, respectively. The incisal point on mouth opening was 7.1%. Based on the above findings, the mandible is not fixed at the intercuspal position by clenching, but is displaced during muscle force exertion by the body trunk.

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The purpose of this study was to investigate the implant stability by means of Osstell™ that have been made progress since the surgery. Twenty patients previously treated with implants were participated in this study. The mean age was 52.6 years (range 23-75 years). All patients were treated implant surgery using socket-lift technique. Jaw bone shape and quality were judged from preoperative radiographs and during drilling according to the classification. Osstell™ is intended for measuring the stability of implants in the oral cavity and craniofacial region. The result is given as a numerical value ISQ and displayed waveform. Implant stability measurements were performed on implant surgery, second implant surgery, loading and regular check-ups at different times. The student t-test for unpaired observations was used for statistical analysis. ISQ values ranging from 60.2 to 80.8 were measured with a mean of 64.33±5.12 based on all normal implants in maxillary and 74.91±5.42 based on patient means. In general, statistically significant higher ISQ values were registered for implants using socket lift technique. Two cases, implants that was affected by soft bone showed a marked lower ISQ values.
Osstell™ were quick and easy to perform and about one minute was needed for attaching, measuring and removing the transducer for each implant. Osstell™ has been proven to be sensitive to measure changes in implant stability, it is presently not known if the technique can be used as a clinical instrument for predicting implant failure and success.

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The objective of this study was to evaluate the retentive force of one-piece implant (Nobel Direct; Nobel Biocare, Sweden) -supported overdentures including a telescope system. The regular platform Nobel Direct (4.3 mm dia.) was embedded in a brass patrix frame (10 x 10 x 25 mm) using autopolymerized polymethyl methacrylate (PMMA; Unifast II, GC). Two sizes of O-rings [O1 (2.8 mm dia.) and O2 (3.8 mm dia.), SAN-EI, Japan] and protection caps (PC; Straumann) were placed on the Nobel Direct abutment head. The plastic patterns of the Konus telescope outer crown were fabricated on the Nobel Direct abutment head and cast using the GC autocast system. As a control, the PMMA resin (RE) was made to directly touch the abutment head. The patrix and matrix frames were connected under 2 kg and then mounted on a screw-driven mechanical testing machine (Model UTM II, Toyo Boldwin, Japan). The retentive force (n=5, N) obtained at a crosshead speed of 40 mm⁄min was analyzed by ANOVA⁄Scheffe's test (α=0.05). The larger O-ring had less retentive force than the smaller O-ring. The Konus telescope had a retentive force comparable to that of the smaller O-ring (p>0.05). Although the retentive forces of the Konus telescope tended to increase as the connecting load increased, the force of the O-ring did not vary according to the connecting loads. For the one implant-supported overdentures, not only a medium-sized O-ring and protection cap but also coping and Konus telescopes demonstrated having appropriate retentive force.

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The purpose of this study was to compare and assess ultrasonic tooth preparation using an air-turbine and micro-motor. Twelve human extracted molars were used in this study. Each crown of the molar was roughly prepared from complete veneer crown and the cervical margin was divided equally into three-120° angles along the line of cement-enamel junction (CEJ). Three devices: Piezotome (SATELEC ACTEON, France), an air-turbine and a 1:5 speed friction grip (FG) micro-motor were used to finish the chamfer margin of each crown. After preparation, the margin continuity, sharpness and roughness, unevenness of prepared surface, were observed by a microscope with 8x magnification. Evaluation was made by 3 independent doctors evaluating the results using 3 levels and compared by the Kruskal-Wallis test. Piezotome showed excellent evenness and the evaluation results were highly significant compared with the micro-motor and significant compared with the air-turbine. Preparation time was analyzed by one way ANOVA and post hoc multiple comparison. The total preparation time of Piezotome was significant longer than the other two. Regarding the results of the simulated preparation test of the subgingival margin for complete veneer crowns using extracted human molars, completion of the cervical margin by Piezotome took more longer, but it could obtain a better cervical margin and this method has sufficient clinical value.

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The purpose of this study was to achieve optimal contrast of imaging characteristics in 4 dimensional MR images of the temporomandibular joint (TMJ) for evaluating the TMJ structures during mandibular movement. Twelve TMJs from six subjects without any TMJ dysfunction were studied. MRI was performed using a 1.5 MR system with an eight-channel phased array coil. The images were acquired using a balanced steady-state free precession (b-SSFP) sequence. The optimal flip angle was determined for differentiation for the main anatomical structures of the TMJ; the posterior band of the articular disc, the retrodiscal tissues, the condylar head, and the lateral pterygoid muscle, by examining the signal intensity (SI-d) of TMJ structures on b-SSFP MR images obtained using various flip angles. Repeated measures two-way analysis of variance (ANOVA) was performed, followed by Bonferroni's multiple comparison analysis. The main anatomical structures of the TMJ had the highest SI-d at flip angles of 30 degrees and 40 degrees, and there were the most significant differences between the SI-d of the articular disc and all other structures at a flip angle of 40 degrees, followed by a flip angle of 30 degrees. These data suggest that a flip angle of approximately 30 degrees to 40 degrees is appropriate for obtaining the optimal contrast of imaging characteristics for 4 Dimensional MR images of the TMJ with b-SSFP sequence.

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There are the problems of harmful side effect such as allergy and durability of antibacterial effect at the dental materials. The purpose of this study is to develop the dental materials which can solve these problems. And we focus on the anti-microbial proteins, lysozyme (LYZ) which exists in oral cavity commonly. In this study the development of anti-microbial dental cement containing the cation exchange resin which binds anti-microbial protein LYZ was performed. The amount of LYZ binding to the glass ionomer cement and its anti-microbial activity against Streptococcus mutans (S.mutans) were examined. Then the mechanical property of the glass ionomer cement-containing the cation exchange resin was tested. The result presented that the amount of LYZ binding to the cement containing the cation exchange resin was significantly greater than the cement non-containing the cation exchange resin (p<0.05). Moreover, the cement binding with LYZ showed anti-microbial activity against S.mutans. In compression strength test, the strength of cement containing cation exchange resin (3wt%) was lower than cement non-containing cation exchange resin (p<0.05). The findings suggest that glass ionomer cement-containing cation exchange resin binds LYZ and have an anti-microbial activity against S.mutans. After all, the application of cation exchange resin for prosthesis is useful for prevention of dental caries and treatment for the other oral diseases, since the concentration of anti-microbial protein in saliva may increase in oral cavity by this procedure.

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In our continually aging society, dental care professionals now have the option of using implants in addition to conventional defect prosthodontics to repair defects, and we can now better respond to a variety of defects. However, there are growing demands from patients for not only the recovery of oral function, but also strong urgings for the therapy to focus on prosthodontic morphology, esthetics, a shortening of the duration of the therapy, and convenience, among others.

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Patient: A 70-year-old edentulous woman with a flap reconstruction presented Kyushu University Dental Hospital for a masticatory dysfunction because of insufficient retention and stability with her complete denture. She had received 5 implants in the mandible for an implant-supported fixed prosthesis. Although an implant-supported fixed prosthesis could provide improved stability and function, the fixed prosthesis and lack of keratinized mucosa led to the difficulty of cleaning. To improve oral hygiene, an implant-supported overdenture was fabricated after free gingival graft from palate. However, a failure in the graft union and the subgingival plaque resulted in peri-implantitis. The patient received open flap debridement and was treated with antibiotics. Although the patient had used this prosthesis with a slight inflammation for 5 years, a deep pocket was observed around the implant. As a treatment of peri-implantitis, abrasive debridement with beta-TCP was performed. Up to the present, the patient healed uneventfully.
Discussion: The implant-supported prosthesis is an alternative to the conventional removable denture and is used to provide predictable retention, stability and function in a flap reconstruction patient. However, we should consider the patient's cleaning ability and the condition of soft tissue around implants.
Conclusion: Prosthodontic treatment planning is a complex process that involves various factors such as the surgical factors, occlusion, superstructure and oral hygiene. If we make a plan in the light of these factors, implant-supported prosthesis must offer better function, comfort and predictable result to the patients.

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Tongue plays an important role by making contact with palate in swallowing. This study was aimed for investigating the utility of originally developed measuring system of tongue pressure in the rehabilitation of dysphagic patients with prosthesis. Subject was a 68 years old male post-surgical laryngeal cancer patient who underwent percutaneus endoscopic gastrostomy because of dysphagia. Tongue pressure during dry swallow was recorded by using our original sensor sheet system (Nitta, Japan) with five measuring points (Chs.1-5) attached on the palatal surface of maxillary denture (RPD). Tongue impression was taken by his maxillary denture and the palatal contour was changed into palatal augmentation prosthesis (PAP), then tongue pressure with PAP was recorded and compared with that with RPD. Magnitude of tongue pressure on median line (CHs.1-3) of palatal surface of RPD was nearly 0 and that on the circumferential part (Chs.4 and 5) had laterality. In PAP, however, magnitude of tongue pressure on the median line increased and showed normal pattern (Ch.1>Ch.2>Ch.3) and that on the circumferential part showed no laterality. Improvement of the tongue pressure production described by our system might contribute to the bolus transport in oral phase of swallowing.

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Prosthesis has a close relation with parallel. When installing prostheses, sometimes dentists need to reform abutment teeth or remaining teeth. In the case of partial denture, remaining teeth and its contours should be parallel. In the case of crown & bridge, abutment teeth and pins should be parallel. In the case of implant, success of the following prostheses depends on implant's direction. The ideal preparation is not easy even for skilled dentists, much less for students and beginners. If they use parallel measurements, they would save time and its accuracy gets higher. Therefore, we invented the parallel measurement apparatus which is convenient for clinical use.

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