Purpose: We investigated the blood flow in the oral mucosa of the palatal area to evaluate the biological condition and clinical parameters. Recently, a new laser Doppler perfusion imaging system Periscan PIM II^R has been developed for spatial tissue and provides images of its perfusion of the superficial area. In order to measure the basal seat mucosa by using this system, we investigated a way of measuring the basal seat mucosa and correcting the perfusion value.
Methods: The effect of scanning distance and tissue curvature on perfusion values was investigated. The perfusion images in the palatal mucosa of 11 maxillary edentulous adults were measured and corrected.
Results: Perfusion values decreased with the increase of incident angle and scanning distance. In the ridge area, the perfusion value of the posterior alveolar ridge area was smaller than that of the anterior. In the palatal area, the perfusion value of the frontal area was the largest.
Conclusions: Our results suggested that the new perfusion imaging system would be useful for evaluating the mucosal condition and determining prosthetic procedures, because distribution maps of perfusion correspond to the anatomical marks and clinical observations. However, numerous examples still need to be accumulated. Key words blood flow, laser Doppler perfusion imaging, denture-bearing mucosa, palatal mucosa

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Purpose: The motions and stress distributions of mandibular complete dentures during use were compared and investigated in terms of denture rigidity using 3 D finite element method (FEM) stress analysis.
Methods: Four models for analysis of mandibular complete dentures with different elastic modulus (1. A resin base denture (C), 2. A resin base denture with reinforcement wire (R), 3. A metal base denture (M), 4. A metal plate denture consisting of a double structure (T)) and measured using 3 D FEM. Modes were separated into two elastic bodies: the dentures and residual ridge. Analyses were executed under the same conditions total loads of 20 kgf and contact.
Results: 1. The total equivalent-potential strain of dentures was high beneath the load point for C and R (2.38-2.86×10^-3ε at buccal-shelf of working side and 0.55-0.68×10^-3ε at posterior residual ridge). The entire dentures barely distorted for M and T (0.98-1.17×10^-3ε at buccal-shelf of working side and 0.21-0.25×10^-3ε at posterior residual ridge).2. In the main stress distribution of mucosa beneath denture bases, high loads were located beneath the loading point of dentures, at lingual distal areas of the working side in C and R. In M and T, increasing the rigidity of dentures reduced the stress beneath the loading point of dentures. Stress was distributed widely and evenly.
Conclusions: When the rigidity of dentures is high, the strain of dentures decreases, the stress of the residual mucous membrane will evenly become distributed, and the distance of the balancing side from the denture border to the residual mucous membrane at the time of unilateral balanced position will decrease.

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Purpose: Severe wear of cast commercial pure (CP) titanium teeth was observed in a clinical survey. This study evaluated the wear resistance of cast CP titanium and titanium alloy teeth after the surface was modified using laser technology.
Methods: Teeth patterns were duplicated from artificial first molars (Livdent FB 30, GC, Japan). All teeth specimens were cast with CP Ti grade 3 (T-Alloy H, GC) and Ti-6 Al-7 Nb (T-Alloy Tough, GC). After the occlusal surface was blasted with Al₂0₃, the occlusal contact points were modified using a laser (Neo laser L, Girrbach, Germany) at the following irradiation conditions (voltage: 260 V; pulse: 7 ms; focus: 1.5 mm). These parameters were determined by preliminary study. As a control, Type IV gold alloy (PGA-3, Ishifuku, Japan) was also cast conventionally. Both maxillary and mandibular teeth were worn using an in vitro two-body wear testing apparatus that simulated chewing function (60 strokes/min; grinding distance: 2 mm under flowing water). Wear resistance was assessed as volume loss (mm³) at 5 kgf (grinding force) after 50, 000 strokes. The results (n=5) were analyzed by ANOVA/Scheffé's test (α=0.05).
Results: The gold alloy showed the best wear resistance of all the metals tested. Of all the titanium specimens tested, the modified surface indicated significantly greater wear resistance than did conventional titanium teeth without surface modification (p<0.05).
Conclusions: Wear resistance was increased by modification of the surface using a laser. If severe wear of titanium teeth was observed clinically, little wear occurred when the occlusal facets were irradiated using a laser.

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Purpose: The present investigation evaluated the relation between the dynamic properties of the bilateral condyle in habitual maximum opening and closing movement and the occlusal force balance with clenching force.
Methods: Nine normal adults participated in this study. The translation of bilateral condyle and the rotation of intercondylar axis in habitual maximum opening and closing movement was measured using Cadiax^®, (ver. 3.0). The amount of translation and the rotation were converted into percentages and plotted on a graph using the translation-rotation relative chart. The maximun difference (d) between right condyle and left condyle of translation in rotation was calculated. The maximum clenching force was measured using Dental prescale^® 50 H, type R and Occluzer^® FPD-703 (Fujifilm Co., Ltd.) and the center of gravity of the occlusal force was plotted on the drawings in two dimensions (anterior-posterior, right-left).
Results: 1. The reproducibility of the dynamic properties of bilateral condyle in habitual maximum opening and closing movement and (d) were shown on the translation-rotation relative chart. 2. It was observed that the center of gravity of the occlusal force of a number of subjects was almost localized on the median line with right-left dimension and was localized on the molar tooth area with anterior-posterior dimension. 3. The correlation coefficient was 0.33 between the coordinate value of the center of gravity of the occlusal force with right-left dimension and the path of opening's (d). The coefficient was 0.71 between the coordinate value of the center of gravity of the occlusal force with right-left dimension and the path of closing's (d).
Conclusions: The present study showed the correlation between the dynamic properties of the bilateral condyle in habitual maximum opening and closing movement and the occlusal force balance with maximum clenching force.

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Purpose: This experiment aimed to clarify the relationship between masticatory path pattern and masticatory efficiency in gumi-jelly chewing.
Methods: For 65 healthy subjects, the frequency of the masticatory path patternwas investigated. Glucose extraction was measured as an indicator representing the masticatory efficiency and was compared between both patterns. Furthermore, the relationship between path stability and masticatory efficiency was investigated.
Results: As for the frequency of masticatory path pattern, pattern I (opened toward working side and then closed convexly) was the highest, followed in order of decreasing frequency by pattern III (opened toward non-working side initially and later toward working side and then closed convexly), pattern II (similar to pattern I but closed concavely), pattern VII (opening and closing paths crossed each other), pattern IV (similar to pattern III but closed concavely) and pattern V (both opening and closing paths were convex), pattern VI (a reverse pattern of the usual path), and pattern VIII (opening and closing path were a straight line). Regarding the amount of glucose extraction, pattern I was the highest, followed by pattern III, V, II, VII, IV, VI, and pattern VIII. Statistically significant differences were found between pattern I and all the other patterns, between II and III, III and IV, VI, VII, V and VI, VI and VII respectively. As the stability of the pattern increased the masticatory efficiency increased also, and a highly significant correlation was found between the two.
Conclusions: It was concluded that there was a close relation between masticatory efficiency and masticatory path pattern, that pattern I gave the best masticatory function, and that by quantitatively analyzing masticatory path pattern it may be possible to objectively evaluate masticatory function.

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Purpose: To determine the importance of margin design on fracture strength and pattern of endodontically-treated teeth with 0 mm of coronal tooth structure.
Methods: Using the CELAY system (MIKRONA, Switzerland), 168 human maxillary central incisors, identical in size and shape, were replicated from bovine teeth. The fracture strength and pattern of 5 types of margin design, three core materials and two levels of remaining coronal tooth structure were examined after 24 hours of water immersion (37°C) under 16 conditions and 83 hours under 6 conditions without cyclic loading, as well as after 83 hours of water immersion with 300, 000 cyclic loading under 6 conditions.
Results: In the case of cast metal post-and-cores with 0 mm of coronal tooth structure, both beveled and shouldered shoulder margin designs resulted in a higher fracture strength than chamfer and shoulder ones, achieving almost the same strength of chamfer margin design with 1 mm of coronal tooth structure. In addition, pinhole preparation on the root surface increased the fracture strength of chamfer margin design to the level of those of the above-mentioned two desirable margin designs. From a fracture pattern viewpoint, however, all margin designs were unsuitable for re-restoration of the tooth.
Conclusions: Both beveled and shouldered shoulder margin designs improve fracture strength of endodontically-treated teeth with 0 mm of remaining coronal tooth structure.

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Purpose: Intraoral views of teeth with dowel and post hole taken by small three-dimensional X-ray CT (3 DX) were compared with three-dimensional images from specimen sections of the same extracted teeth. This comparison shows the usefulness of 3 DX for examination of cracked teeth in the oral cavity.
Materials and methods: After taking dental tomographic images using 3 DX for fractured teeth in the oral cavity, the fractured teeth were extracted and three-dimensional images for them and their cracks were obtained from a set of photographed sections. Then both sets of three-dimensional images for the fractured teeth were compared in terms of the form and region of the cracks.
Discussion: The tooth cracks were observed at the root face region in the intraoral view. Also, in the extracted teeth, fracture lines were recognized from the three-dimensional images. Moreover, a discontinuous image was obtained in teeth from the dental tomographic image using 3 DX. This discontinuous image in teeth was observed in the same region and direction as the cracks of the three dimensional image from specimen sections of the extracted teeth.
Conclusions: The discontinuous images of teeth in the dental tomographic images from 3 DX were observed in the same region and direction as the cracks of teeth in the three-dimensional images from specimen sections of the extracted teeth. It was confirmed that dental tomographic images from 3 DX are useful for finding cracks in living teeth. However, dental tomographic images from small threedimensional X-ray CT are not perfectly reliable because the discontinuous image is not found in some teeth where the cracks are recognized by images from specimen sections after extraction.

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Patient: An implant prosthesis with O-ring attachments had been fabricated for edentulous mandible. The patient complained of decreasing retention of the denture and frequent loosening of implant abutments. In order to resolve these problems, an implant overdenture prosthesis with magnetic and bar attachments was planned.
Discussion: The patient has been satisfied for 4 years and 9 months after treatment, and poor retention of the denture and loosening of implant abutments have not occurred. The reasons might be consistently good retention of the denture with magnetic attachments, proper load distribution by connecting implants and improved oral care of the patient.
Conclusion: Periodical recall and adequate oral care are necessary.

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Patient: A 55-year-old female patient was treated with a removable partial denture for the mandibular bilateral free-end space.Since the patient did not wear the removable partial denture because of discomfort, the remaining teeth were mobile. She also complained of temporomandibular joint pain on both sides. Implant therapy was planned for the mandibular bilateral free-end space to reestablish the proper occlusal support.
Discussion: After setting the implant restorations for the mandibular bilateral free-end space, mobility of the remaining teeth and temporomandibular joint pain disappeared. During the observation period after treatment, no biological and biomechanical problems appeared.
Conclusion: Implant therapy is effective not only for establishing the occlusal support but also for reestablishing the stability of remaining teeth.

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Patient: A 45-year-old female presented with the chief complaint of masticatory disturbance and spontaneous pain at the mandibular left second molar. Her maxillary left first and second molars, and mandibular right first and second molars were missing and the edentulous arches had been left untreated for a long period.
Discussion: In this patient who lacked occlusal support, occlusal reconstruction was done using a temporary prosthesis. Prosthodontic treatment with minimum tooth extraction required several years. Taking aesthetics into consideration, the maxillary right lateral incisor was used as a support for a removable partial denture. The small perforation was sealed successfully with an adhesive resin (4-META/MMA-TBB resin) in order to restore the mandibular left first molar.
Conclusion: The occlusal reconstruction for partially edentulous arches without occlusal support took several years. Informed consent and cooperation between patient and dentist were indispensable for the satisfactory results in this case.

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Patient: The patient was a 51-year-old male with a chief complaint of masticatory disturbance and anesthetic problem for the upper partially edentulous region. The cone-crown retained denture was selected as a first treatment plan. However, sufficient satisfaction was not achieved because of oral discomfort, such as bulkiness of the denture and gustatory sensation. Therefore, the treatment plan had to be changed to improve these problems. A second plan using hybrid prostheses was selected, i. e. implant prosthesis for the premolar and molar edentulous region and removable bridge for the incisor and canine region.
Discussion: This case suggests the difficulty of selecting a treatment plan matching the patient's demands.
Conclusion: Remarkable improvement for the oral discomfort was observed and the patient's QOL was improved by careful planning of the prosthetic treatment. No problem has been observed for three years after the second prosthetic intervention.

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