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Purpose The purpose of this study was to evaluate the effect of differences in the retainer design on load on abutment teeth and displacement of the denture base in mandibular unilateral extension base partial removable dental prosthesis to determine the optimum design for a mechanically appropriate retainer. Methods Three models were used. Each incorporating a removable denture with different designs of retainer positioned. In design A, Akers clasps were positioned over the first and second premolars. In design B, embrasure clasp was positioned over the first and second premolars. In design C, rest and back-action clasps were positioned over the first and second premolars, respectively. Loading on the occlusal surface of the dentures was performed in the vertical, oblique lingual and buccal directions. Load on the abutment teeth and displacement of the denture base were determined by the three-dimensional finite element method analysis. Results Vertical and buccolingual load on the abutment teeth by lingual and buccal direction loading on the denture were smaller in designs B and C than in design A. However, the superioinferior and buccolingual displacement of the denture base by buccal direction loading on the denture were largest in design A. Superioinferior and buccolingual displacement of the denture base by the lingual direction loading on the denture were largest in design C. Conclusions Under the conditions set in this study, the stability of design A was greater than that of design B or C, but load on the abutment teeth was larger.

Purpose The purpose of this study was to develop design criteria for palatal straps according to palatal shape. Methods The palatal shapes of 60 dentate maxillary stone casts were measured using a contact-type three-dimensional measuring instrument. Based on the average of the 60 palatal shapes, 5 three-dimensional finite element models (FE models) were constructed: a basic FE model, a wide palatal FE model, a narrow palatal FE model, a deep palatal FE model and a shallow palatal FE model. The FE models were simulated unilateral free-end saddle dentures with the maxillary left second premolar and first and second molars missing. The FE models included a denture base, two rests and a palatal strap. The mechanical properties of Co–Cr alloy, Ti–6Al–7Nb alloy and type IV gold alloy were given to the FE models. A vertical load of 50N was loaded onto the occlusal surface of the left first molar. Vertical displacement of the distal edge of the denture base was then compared between models. Results Compared to the basic FE model, displacement in the wide FE palatal model and shallow palatal FE model was larger, and displacement in the narrow palatal FE model was smaller. The difference in displacement between the deep palatal FE model and basic FE model was small. Conclusions With a wide and shallow palate, it is necessary to design a reinforced palatal strap. With a narrow palate, the anteroposterior width of the palatal strap can be narrower. With a deep palate, it is not necessary to change the palatal strap design according to the palatal shape.

Purpose: The objective of this study was to clarify the effect of mechanical loading on the trabecular structure of peri-implant bone and determine its correlation with the implant stability quotient (ISQ) value.Methods: This study used 3 immunologically mature male dogs. Three months after bilateral extraction of the mandibular premolars of the dogs, 4 implants were placed in these sites for each dog. After 3 months to allow healing of the implant sites, superstructures were prepared on the right side (loaded side). The implants on the left side were covered with mucosa (non-loaded side). The ISQ values of all implants were measured 3 months after placing the superstructures; subsequently, the animals were sacrificed. After the mandible was excised and fixed, micro-CT images were acquired and three-dimensional analysis, performed.Results: The means and S.D. of the ISQ value for the 12 implants were 69.6±6.2 and 62.9±13.8 for the loaded and non-loaded sides, respectively. No significant difference was noted between the 2 sides. Mean and S.D. of bone volume fraction (BV/TV) were 13.0±6.6 and 9.3±3.8; trabecular thickness (Tb.Th), 97.7±27.7 µm and 91.0 ± 24.0 µm; and trabecular number (Tb.N), 1.24±0.30/mm and 0.99±0.20/mm for the loaded and non-loaded sides, respectively. BV/TV and Tb.N values were higher for the loaded side.Conclusion: Morphological changes occurred in response to functional loading. However, lamellar bone was observed around the implants on both sides. These findings revealed that changes in the bone structure due to functional loading of implants had negligible or no effect on the ISQ value.

Objectives: This study is to show the usefulness of the endoscopic endonasal approach in the surgical treatment of isolated blowout fractures of the orbital floor. Methods: Between 1997 and 2003 we operated on 65 patients complaining of diplopia due to isolated blowout fractures of the orbital floor, including 4 patients accompanied with enophthalmos. In 62 of the 65, only the endonasal approach with endoscope was used, while in the remaining 3 patients, we used the combined endonasal and transantral approach. To do the endonasal repair surgery smoothly under the endoscope, via the middle nasal meatus, septoplasty was supplemented in 13 patients and submucous conchotomy in 57. The bone fragments trapping the orbital content herniated into the maxillary sinus were carefully removed so as to keep the periorbita intact. Tampon gauzes or a balloon catheter for temporal fixation was placed in the maxillary sinus through the middle nasal meatus to support the orbital floor for 2 to 7 days. No permanent supporting material was used. Immediately following the repair and the fixation the eye traction test was respectively performed to confirm that the eyeball was freely moving. Results: Postoperatively diplopia disappeared in 50 of the 57 patients using only the endonasal approach, (87.7%) and enophthalmos improved 3 of 4 followed over 6 months. Conclusions: From this high success rate with respect especially to diplopia we conclude that the endoscopic endonasal approach is alternative to extranasal methods in view of cosmetics and the improvement of eye movement.

In this study, we confirmed the reappearance of the somatosensory-evoked field (SEF) responses following periodontal mechanical stimulation of the upper and lower teeth. And the equivalent current dipole (ECD) locations activated by the stimulation of the upper tooth were compared with those of the lower tooth. In addition, we investigated the influences of lack of periodontal pressoreceptive information under anesthetized conditions at the periodontal tissue of the upper tooth. For mechanical stimulation to the periodontal ligament, we used a nitrogen gas pressure-driven tactile stimulator. SEFs were recorded using 306-channel whole-head DC-SQUID neuromagnetmeter when the tactile stimulation was applied to the tooth. The SEFs were recorded following tactile stimulation of the tooth. Three peaks were observed in the SEF response. Although the ECDs of their peak latencies for upper and lower teeth were identified. There was no significant difference (p

The objective of this report was to review 365 cases of Brånemark Implant Bridge including 1,444 fixtures in patients of Tokyo Dental College Chiba Hospital. The term of implantation was divided into several phases; less than 1 year, from 1 year to 3 years, from 3 years to 5 years, from 5 years to 7 years, from 7 years to 10 years, more than 10 years, and the survival rate was calculated for each phase. The removal rate of fixture after connecting the superstructure was 13% in maxillary cases and 2% in mandibular cases. The functioning survival rate in maxillary cases slightly decreased from 91% in less than 1 year to 87% after more than 10 years; however, the functioning survival rate in mandibular cases was about 99% in all periods. The removal rate of fixtures per patient was 23% in maxillary cases and 6% in mandibular ones. The average removal number of fixtures was 1.8 in maxillary cases and 1.2 in mandibular ones. The removal of the fixture occurred most frequently at less than 1 year in maxillary cases, but there was no tendency for a pattern of removal of fixture in mandibular cases.

35 patients with blowout fracture were surgically treated between 1997 and 1999. We applied the endonasal approach to 29 of the 35 cases (medial fracture 11 and inferior fracture 18) using endoscope. Septoplasty on four and submucous conchotomy was complemented on 24 cases during surgery because of allergic rhinitis and acute/or chronic sinusitis. Bone fragments adhesive to the orbital contents protruded into the sinus were carefully removed. The periorbita was preserved as much as possible. Intraoperative traction test both after the repair as above mentioned and the temporary fixation using tampon gauze or balloon catheter was performed on all the patients to confirm the improvement of mobility of the eyeball. The result of the traction test related to the prognosis. Only three cases still showed slight diplopia postoperatively. This result indicates that endoscopic sinus surgery can be applied even to the orbital floor fracture.

Recently, finite element analysis (FEA) has been use frequently to determine the biomechanical movement of teeth. However, the condition of the jaw bone and periodontal ligament varies in the reports, and it has not been clarified.The purpose of this study was to clarify the differences between actual displacement of human teeth obtained by loading experiment and numerical values of the FEA model. Then the influence of the condition of the jaw bone, periodontal ligament and a fixed condition exert on the analysis value was evaluated using a mandibular premolar FEA model of the buccolingual section.As a result, it was one of the effective means to control horizontal displacement of compact bone and to gradually increase Young's modulus of periodontal ligament from tip to cervical margin, causing displacement under pressure of the two-dimensional FEA model to approximate actual values.

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.

PURPOSE To determine the density of corneal stromal cells in wearers of soft contact lenses (SCLs) and rigid gas-permeable (RGP) contact lenses (CLs). METHODS The keratocyte density (KD) was measured at different depths of the stroma by confocal microscopy. In study 1, 32 wearers of rigid gas-permeable (RGP) lenses and 30 wearers of SCLs were studied. Forty volunteers with no history of CL wear were studied as controls. In study 2, 16 volunteers with no history of CL wear were divided into 2 groups; 7 subjects wore RGP lenses (oxygen transmissibility, Dk/L, 35) and 9 subjects wore SCLs (Dk/L, 34). All subjects were asked to wear the CLs daily for 6 months. RESULTS In study 1, the KDs in the anterior stroma (AST) and the posterior stroma (PST) of the cornea were significantly lower in the RGP lens group than in the control group. The KD in the SCL group was significantly lower at all depths of the cornea than that of the control group. In study 2, the KD in the AST of the RGP lens group was significantly lower after 1 month of CL wear. The KD in the AST and PST of the SCL group was decreased significantly at 1 month, and all layers were decreased by 10% to 20% 6 months after wearing CLs. At 5 weeks after discontinuation of SCL wear, the KD in all layers was not significantly different from that at the baseline. CONCLUSIONS The change in the KD was greater in CL wearers than in volunteers with no history of CL wear and also greater in SCL wearers than in RGP lens wearers. Analysis of the KD by confocal microscopy may be a useful method for evaluating the effect of CL wear.

Purpose To indentify buccal design criteria for retainer on polyamide resin removable partial dentures. Methods A left upper distal extension model was used for this study. Undercut was given on the buccal side of first and second premolars. Four different retainer designs were created. Undercuts of 0.5 and 0.75mm were used. All 4 retainer designs started from distal surface of second premolar. The retainer extended to Design 1: covering to the mesial surface of second premolar; Design 2: covering to the distal surface of first premolar; Design 3: covering to the mesial surface of first premolar; and Design 4: covering to the distal surface of canine. For the 0.75mm undercut experiment, only Design 1 and Design 3 were used. Each experimental denture was pulled and the force maximum required to remove the denture measured. Results On 0.5mm undercut, no significant difference was found between Designs 1 and 2 or between Designs 3 and 4. Significant differences were found between all other combinations, however. On 0.75mm undercut, a significant difference was found between the two. Conclusion The retentive force of a design for the buccal part of retainers in polyamide resin using large undercut was more effective than that of a design covering to the anterior abutment tooth.

Purpose The All-on-4 is used in the therapy of edentulous mandibles. However, few studies have investigated the effect of such implants on supporting bone. To clarify differences in stress in peri-implant cortical bone between 2-patterns of 6 implants and 8-patterns of 4 implants with change in inclination angle based on the All-on-4. Methods Three-dimensional finite element analysis models based on the mean value of the Japanese edentulous mandible were constructed. Implants 13 or 15 mm in length were inserted between the mental foramina. In the 6-implant model, implants were inserted in parallel. In the 4-implant model, the 2 anterior implants were inserted in parallel and the 2 posterior implants in parallel or on a slant. Implants were splinted with a superstructure. A 50 N load was applied to the occlusal surface under condition A, at 2 mm distal from the distal implant, or condition B, at the distal end of the superstructure. Maximum von Mises stress on cortical bone was measured. Results Stress was concentrated around the posterior-most implant on the right side. Under condition A, stress increased with 4 implants and increase in angulation. At 45°, stress increased by 23% of that in the 6-implant model. Under condition B, stress increased with 4 implants, although stress decreased with increase in angulation. At 45°, stress decreased by 45% of that in the 6 implants. Conclusions The use of 4 implants or inclined implants increased stress on peri-implant cortical bone. However, when used in conjunction with a short cantilever, inclined implants decreased stress on peri-implant cortical bone.

With thin and thick section Multi-slice CT images at lung cancer screening, we have statistically and quantitatively shown and evaluated the diagnostic capabilities of these slice thicknesses on physicians' pulmonary nodule diagnosis. To comparatively evaluate the 2 mm and 10 mm slice thicknesses, MSCT images of 360 people were read by six physicians. The reading criteria consisted of nodule for further examination (NFE), nodule for no further examination (NNFE) and no abnormality (NA) case. For reading results evaluation; firstly, cross-tabulation was carried out to roughly analyze the diagnoses based on whole lung field and each lung lobes. Secondly, from semi-automated extraction result of the nodule, detailed quantitative analysis was carried out to determine the diagnostic capabilities of two slice thicknesses. Finally, using the reading results of 2 mm thick image as the gold standard, the diagnostic capabilities were analyzed through the features and locations of pulmonary nodules. The study revealed that both slice thicknesses can depict lung cancer. Thin section may not be effective to diagnose nodules of ≤3 mm in size and nodules of ≤ 5mm in size for thick section. Though thick section is less tiring for reading physicians, it is not good at depicting nodules located at the border of lung upper lobe and which have a pixel size distance of ≤5 from the chest wall. The information presented may serve as a useful reference to determine in which particular pulmonary nodule condition the two slice thicknesses can be effectively used for early detection of lung cancer.

The position, depth and direction of implant placement are often planned based on evaluation of radiographs and study casts. Insertion planned in such a manner may not be adequate for precise and safe surgery in some cases due to inadequate working clearance in the oral cavity. In order to obtain high initial stability and ensure osseointegration at the implant-bone interface, careful and precise drilling must be performed at the implant placement site. Therefore, we propose the necessity of evaluating the operability of implant treatment-devices prior to surgery. The amount of handling space needed during implant placement surgery was determined. The results showed that for implants with a length of 7-18 mm, a vertical distance of as much as 50-60 mm was required, depending on the implant platform. These results suggest the necessity of pre-operative drilling simulation in each individual. Handling space was measured with angled heads and probes fabricated on a trial basis for pre-surgical drilling simulation in the oral cavity. We believe that these instruments may be clinically useful in estimating the amount of handling space required prior to surgery and ensuring precise implant placement. Evaluation of the intra-oral environment for handling of treatment devices should be included in the pre-surgical intra-oral evaluation of dental implant cases to avoid changes in treatment planning due to intra-oral interference during the course of surgery.

The aim of this study was to observe the influence of prosthesis design and loading condition on the stress distributions of tooth-implant supported prostheses. Six 2D finite element models, two reference models, and four experimental models were computed to simulate different prosthesis designs. Six different loading conditions were applied to investigate the stress distributions of tooth and implant, respectively. The stresses of reference models were considered as 100%; the stresses of experimental models at the same locations were compared with those of reference models. The stresses around implants were higher than those around teeth. When vertical loading was applied only on the implant, the stresses to both the implant and teeth were at their lowest. The highest stress to the tooth was in the model TTPF and the lowest in the model TPFF. The highest stress to the implant was in the model TPPF and the lowest in the model TPFF. These data indicated that the loading on the tooth-implant supported prosthesis was mainly supported by the implant. Minimizing the loading on the tooth decreased the stress to both the tooth and the implant. Adding fixtures as abutment was more effective in decreasing the stress than adding tooth as abutment in tooth-implant supported prosthesis.

Two types of bacteriophage specific to Pseudomonas plecoglossicida , the causative agent of bacterial hemorrhagic ascites disease in cultured ayu fish ( Plecoglossus altivelis ), were isolated from diseased ayu and the rearing pond water. One type of phage, which formed small plaques, was tentatively classified as a member of the family Myoviridae , and the other type, which formed large plaques, was classified as a member of the family Podoviridae . All 27 strains of P. plecoglossicida examined, which were isolated from diseased ayu from geographically different areas in 1991 to 1999, exhibited quite similar sensitivities to either type of phage. One strain of P. plecoglossicida was highly virulent for ayu, and the 50% lethal dose (LD 50 ) when intramuscular injection was used was 10 1.2 CFU fish −1 ; in contrast, phage-resistant variants of this organism were less virulent (LD 50 , >10 4 CFU fish −1 ). Oral administration of phage-impregnated feed to ayu resulted in protection against experimental infection with P. plecoglossicida . After oral administration of P. plecoglossicida cells of this bacterium were always detected in the kidneys of control fish that did not receive the phage treatment, while the cells quickly disappeared from the phage-treated fish. Bacterial growth in freshwater was lower in the presence of phage, and the number of phage PFU increased rapidly. These results suggest that it may be possible to use phage to control the disease caused by P. plecoglossicida .

Purpose Preserved human amniotic membrane has been used in reconstruction of the ocular surface. In this paper, we report our method of amniotic membrane transplantation (AMT) for recurrent pterygium. Methods Twenty-six eyes of 26 patients with recurrent pterygium are reported. All subjects were operated on with an extensive excision of the subconjunctival fibrous tissues followed by application of mitomycin C(0.04%, 3∼5 min) during the operation. Amniotic membrane transplantation was performed with implantation of conjunctival autograft in cases with a large excision. Results The mean follow-up time was 17.3±9.3 (mean±standard deviation) months. Twelve eyes showed severe symblepharon and 14 patients had suffered from double vision before the operation. There were only three mild recurrences (12%), 11 patients recovered from double vision, and no major complications such as sclermalacia performans were noted during the follow-up period. Conclusion AMT with application of mitomycin C is effective in preventing pterygium recurrence and for improved ocular movement. The cosmetic outcome of our methods has also been satisfactory.

1999年4月に徳島県下のアユ養殖場で出血性の腹水症状を呈する病魚から、水溶性の褐色色素を産生するグラム陰性、好気性、非運動性の桿菌が分離された。形態学的、生化学的性状および抗 -P. plecoglossicida 血清との凝集試験結果に基づいて、分離株は細菌性出血性腹水病の原因菌である P. plecoglossicida に同定された。分離株のアユに対する病原性は強く、そのLD50値は 7×100 CFU (筋肉内注射)であった。本病の原因菌に褐色色素産生株も存在することが判明した。