In severe edentulous cases, it is often very difficult to detect premature contact areas by conventional methods in occlusal adjustment because of easy denture displacements and movements. We have developed an occlusal adjustment device utilizing the magnet repulsive force based on Coble intra-oral balancer. This device can stabilize denture bases without displacement and movement and enables us to detect premature contact areas exactly at centric occlusion, because the magnet repulsive force is maximal near the centric occlusion, by which the upper and lower denture bases can be pressed firmly to residual ridge mucosae inside the oral cavity. However, how the magnet repulsive force affects the mandibular position or displacement of denture is not clear, and it is also possible that the repulsive force inverts to be attractive. To clarify these matters, two magnets were placed pole-to-pole, and how the repulsive force is changed in strength and direction by the vertical and horizontal movements of the two magnets and by simulated mandibular movements was analyzed using the finite element method. When two magnets were vertically separated keeping in parallel, the repulsive force decreased in inverse proportion to the square of inter-magnet distance. When each magnet was placed at the center of upper and lower dentures, it was necessary to keep the inter-magnet distance to be 5 mm minimum for mandibular movements without magnet contact, and the vertical repulsive force was 974 gf at this minimum inter-magnet distance. When one of the magnets was moved keeping the vertical inter-magnet distance to be 5 mm, the horizontal repulsive force became greater than the vertical repulsive force at 10 mm horizontal movement.
In simulated mandibular movements, the larger jaw opening was, the smaller was the vertical repulsive force and the greater was the horizontal repulsive force. At 40 mm jaw opening, the vertical repulsive force was smaller than the horizontal repulsive force. In protrusive and lateral magnet movements, the horizontal repulsive force increased and the vertical repulsive force decreased as the distance moved increased, and this decrease became greater as the angle of horizontal condylar indication increased. It was found finally that the jaw opening should be kept within 30 mm, protrusive movements within 8 mm and lateral movements within 16 mm taking the displacement and movement of dentures into consideration for achieving stable occlusal adjustment. With these movement ranges, this method can practically be applied to clinical occlusal adjustments.

View full abstract

In order to control cross-contamination of blood-born pathogens through air turbine handpieces, an oil-heating bath “Oilizer®” was developed and tested its bactericidal effect. The apparatus uses either silicon oil or liquid paraffin as heating medium and could kill the cells of Staphylococcus aureus and Escherichia coli strains effectively by the treatment for two or four min at 140 or 130°C, respectively. The apparatus was also suggested to inactivate hepatitis B virus effectively as well

View full abstract

For exploring the dental application of ozone gel, the bactericidal potency was compared between the freshly purified ozone gel containing 3 different ozone concentrations and the electrolyzed gel hard-type, and between the ozone gel immediately after purification and the ozone gel storaged for 2 months after purification at room temperature.
The ozone gel containing 10 ppm ozone showed a bactericidal effect on E. coli, aeruginosa, S. mutans, B. subtilis, C. albicans all about 5 bacterial strains immediately after addition and, among them, only C. albicans was decreased to be lower than the detection limit, and even after 6 h of reaction, only E. coli, K. pneumoniae, P. aeruginosa, S. mutans, S. aureus, C. albicans all about 6 strains became lower than the detection limit. This bactericidal potency was slightly stronger than that of electrolyzed gel hard-type. The gel containing 100 ppm ozone showed a greater bactericidal effect than the 10 ppm ozone gel, and the 1000 ppm ozone gel reduced E. coli, K. pneumoniae, P. aeruginosa, S. mutans, S. aureus, MRSA, S. epidermidis, C. albicans all about 8 bacterial strains to be lower than the detection limit immediately after addition, except for B. subtilis. The ozone gel immediately after purification and the ozone gel storaged at room temperature for 2 months after purification showed similar bactericidal effects on E. coli and S. aureus regardless of reaction time.
These results suggest that the ozone gel can be used widely and is clinically useful as well, because it has instantaneous and persistent bactericidal effects.

View full abstract

Recently, the sterilization and disinfection of dental impressions and models are increasingly calling attention as one of preventive measures to avoid infections to dental health-care workers. Since acidic electrolyzed water shows the bactericidal and disinfectant effects that are not inferior to conventional disinfectants, acidic electrolyzed water has been reported to be an effective bactericide and disinfectant for alginate impressions and very effective particularly when it is used as a mixing solution for alginate impressions. However, the influence of the use of acidic electrolyzed water as a mixing solution to the biomaterial quality of alginate impression has not yet been investigated.
Thus, we investigated comparatively on changes in the hardening time, permanent strain, elastic strain and dimensional stability of the alginate impression prepared by using acidic electrolyzed water as a mixing solution.
The hardening time of the alginate impression mixed with acidic electrolyzed water tended to become shorter. Both the elastic and permanent strains of the alginate impression mixed with acidic electrolyzed water were within the range of JIS specifications and nearly identical to those of the alginate impressions mixed with tap water. The dimensional stability was also unchanged compared with tap water-mixed alginate impressions (p < 0.05).

View full abstract

We have recently been advancing our research for the purpose of reconstructing maxillary bones and compensating osseous tissues using polymer electrolyte complexes (PECs). In this study, we prepared the PEC-hydroxyapatite hybrid (HAPEC ball) using newly developed PEC and hydroxyapatite particles (HAPs) with different particle diameters (200-500, 1000 μm, porosity : about 35%), and performed animal experiments to investigate the bio-affinity and biocompatibility of the HAP particles, PEC and HAPEC ball, and their potentials to be bone filling matrixes. The HAPEC ball was found to strongly facilitate the migration of cells compared with HAP particles alone. Inflammatory reactions also decreased with time, and, in particular, little inflammatory cellular infiltration was observed in 8-week cases. Moreover, there was neither diffusion nor outflow of HAP particles from the HAPEC ball. Comparison based on particle sizes showed that 200-500 μm HAPEC particles maintained the morphology upon embedding better than those with other particles diameters, and HAP particles with the largest diameter (1000 μm) showed the greatest foreign-body reaction.
The PEC newly developed not only possessed bio-affinity and biocompatibility but also facilitated potently the migration of cells. The maintenance of the HAPEC ball morphology was greatly improved by the use of HAP particles with 200-500, μm diameters. These results suggest the usefulness of the HAPEC ball as a biomaterial.

View full abstract

Periodontal tissues play a key role in success in tooth transplantation and replantation. We have previously realized the long-term preservation of the activity of periodontal tissues by using the UW solution, a conventional solution for preservation of organs. To establish a longer-term preservation method, we investigated the biological activity of human-periodontal ligament cells stored in solutions containing trehalose. Both the cell adhesion and growth of periodontal ligament cells were better in the UW solution than in physiological saline. Storing controlled-freezing point was better than storing frozen, and cellular functions could be preserved more nicely for a long time by storing controlled-freezing point than by storing frozen. Although the adhesiveness and growth of periodontal ligament cells could not be significantly improved by the addition of trehalose, the usefulness of trehalose was suggested.

View full abstract

Recently, castable ceramic crowns are being utilized clinically, but their strength has been raised as a problem. Thus, for the purpose of clarifying whether the hardness of adhesive resin cement affects the strength of CASMIC crown, we luted CASMIC crowns with adhesive resin cement with different Young's moduli, then varied loading directions and loading points and investigated comparatively the internal stresses induced in the CASMIC crown, anchor tooth and peripheral tissues, using the three-dimensional finite element stress analysis.
As a result, the effects of different Young's moduli of the resin cement on the tensile stress induced in CASMIC crown changed when the loading point, measuring point and loading direction were changed. In addition, under such a loading condition as causing a strong tensile stress in CASMIC crown, the greater was Young's modulus, the smaller was the tensile stress, suggesting that the CASMIC crown would clinically have a smaller risk of fracturing when the Young's modulus of luting cement is large. In addition, the greater was the Young's modulus of the cement, the smaller was the effects to the dentin around the pulp. The magnitude of the Young's modulus of the cement little effects the periodontal ligament.

View full abstract

Recently, electrolyzed acidic jell was developed by the electrolysis of glycerin aqueous solution containing sodium chloride using a special device. This jell has a wound-healing activity and a strong bactericidal effect on anaerobic gram-negative obligate rods on one hand, it is reported to induce no resistant bacteria on the other hand. In the present study, for the purpose of clinically applying electrolyzed acidic jell to local delivery into periodontal pockets for treating periodontal diseases, we investigated its bactericidal potency in vitro in the four strains of the two species of gram-negative obligate anaerobic rods, Porphomonas gingivalis and Fusobacterium nucleatum, known to have strong periodontal pathogenicity, and administered the jell into periodontal pockets and investigated effects on clinical symptoms and bacteria and black pigment-producing anaerobic rods in periodontal pockets. In vitro, soft-type electrolyzed acidic jell (without grape) showed a bactericidal in vivo effect on all the four bacterial strains tested immediately after application, whereas hard-type electrolyzed acid jell (with grape) began to show a bactericidal effect on two standard bacterial strains 10 min after application and on clinically isolated two bacterial strains immediately after application. Hard-type electrolyzed acid jell (without grape) was bactericidal immediately after application to the clinically isolated P. gingivalis and began to show a bactericidal effect on other three bacterial strains 10 min after application. In vivo, soft-type electrolyzed acidic jell (without grape) significantly reduced the number of bacteria 1, 3 and 7 days after administration into periodontal pockets compared with immediately before administration, and this effect was nearly equipotent to that of Periofeel®. The number of bacteria was also decreased by other three types of jell, though not significantly. No significant change was observed in clinical symptoms before and after jell administration.
These results demonstrate that electrolyzed acidic jell has a potent bactericidal activity to gram-negative obligate anaerobic rods and reduces bacteria inside periodontal pockets.

View full abstract

For investigating material influences on the retentive force of Konus·Krone, the outer crown of Konus·Krone was prepared using the alloys with different hardness (gold-platinum alloy : Degulor M, and Co-Cr alloy containing titanium : Dentitan) with varied thickness (0.4, 0.6, 0.8 mm). Using these outer crowns, the influences of combinations of varied Konus angles (4, 6, 8°), inner crown heights (2, 4, 6, 8, 10 mm) and loads (5, 10, 15 kgf) on Konus·Krone were investigated basically. Under all the Konus angle and load conditions tested, Degulor M showed the tendency that the retentive force decreased as the outer crown became thicker, and the rate of these decreases became constant as the load increased at any Konus angle. In addition, at any outer crown thickness, the mean retentive force and its standard deviation tended to decrease as Konus angle became larger, and increased as the load increased. The retentive force of Dentitan tended to increase as Konus angle decreased and as the inner crown height increased in a manner similar to Degulor M. However, the decreases in retentive force due to changes in Konus angles and inner crown heights were small, and the retentive force was kept high even at low inner crown heights and large Konus angles. All the outer crowns tested showed positive load dependence; the heavier the load, the greater the retentive force. Dentitan showed strong load dependence at all the inner crown heights tested, compared with Degulor M. Different alloys showed different onset trends in retentive force, that is, Dentitan was largely affected by the load which is relating to strains themselves, but not so directly influenced by such factors as Konus angle and inner crown height, compared with Degulor M.

View full abstract

Titanium is equipped with desirable properties as a dental metal owing to its superior corrosion resistance and bio-affinity and to similar mechanical properties to the type IV gold alloy. It is pointed out, however, that titanium is difficult to cast because of its high melting point and high chemical activities at high temperatures and to polish due to its high hardness. Although the dental CAD/CAM system is being used for manufacturing prosthetic dental crowns rationally and precisely, a problem still remains as to the fitting accuracy of prosthetic titanium crowns. In the present study, we thus enlarged the cutting passes determined from the data obtained by using a pattern model by 0.3%, 0.5% and 1.0% along the X-, Y-and Z-axes, and comparatively investigated the inner surface fitness of titanium crowns. As a result, the cement capsules of the pure titanium crowns manufactured at 1.0% enlargement of cutting pass had a thickness of 51.6 ±28.1, um (mean ±SD) at their margins and a thickness of 35.9±14.7 pm throughout the inner surface. These results suggest that the pure titanium crowns manufactured by 1.0% enlargement of the cutting pass can be applied clinically.

View full abstract

Bone morphogenetic protein-2 (BMP-2) stimulates osteoblastic differentiation in human periodontal ligament cells (HPDL cells). This action of BMP-2 is modulated by prostaglandin E₂ (PGE₂), which is local regulatory factor in bone metabolism. In the present study, we investigated mechanisms involved in enhancement by PGE₂ of BMP-2-stimulated osteoblastic differentiation in HPDL cells. PGE receptor (EP) 2 agonist and EP4 agonist as well as PGE₂ enhanced the BMP-2-stimulated Alkaline phosphatase (ALP) activity. PGE₂, EP2 agonist and EP 4 agonist, but not BMP-2, stimulated cyclic AMP (cAMP) accumulation, and cAMP-elevating agents such as forskolin, dibutyryl cAMP (db-cAMP) and 3- (isobutyl) -1- methylxantine (IBMX) were enhanced the BMP-2-stimulated ALP activity. The PGE₂-enhanced ALP activity in HPDL cells treated with BMP-2 was inhibited by adding a protein kinase (PK) A inhibitor H89, whereas, a PKC inhibitor GF109203X had no effect on it. H89 also inhibited the enhancement by EP2 agonist or EP4 agonist of BMP-2-stimulated ALP activity. EP2 agonist, EP4 agonist, forskolin and db-cAMP stimulated phosphorylation of CREB, whereas, BMP-2 had no effect on it. On the other hand, BMP-2, but not EP2 agonist, EP4 agonist, forskolin or db-cAMP, stimulated phosphorylation of Smad 1. These results suggest that PGE₂ enhances BMP-2-stimulated osteoblastic differentiation in human periodontal ligament cells via EP2/4-cAMP/PKA signaling cascade.

View full abstract

The purpose of this study was detect the presence of four putative periodontopathic bacteria Porphyromonas gingivalis (P. g.), Actinobacillus actinomycetemcomitans (A. a.), Prevotella intermedia (P. i.), and Bacteroides forsythus (B. f) using PCR in the oral cavities of children, then investigated relationships between bacterial species and various clinical parameters.
The subject of 37 children were enrolled the pediatric dental clinic at the Showa University Dental Hospital in Japan. Children with systematic diseases were not excluded, although no subjects who had taken antibiotics within the past 3 month were included. A supragingival plaque sample was collected from the mesiobuccal and labial surfaces of the right maxillary central incisor (FDI 11) and the right maxillary first molar (FDI 16). Extracted DNA from plaque samples was used for PCR in this study. The amplification products were photographed under UV illumination. The following clinical parameters were also assessed : intraoral examination, probing depth (PD) and Bleeding On Probing (BOP).
In this study, detection rate for P. g. was 21.6% and A. a., P. i. and B. f were detected from 55% to 58% in supragingival plaque. All subjects were not periodontitis. In addition, detection rates for A. a., P. i. and B. f were high in children with mixed dentition, but low in those with permanent dentition. Furthermore, regarding the relationship between bacterial species and BOP, it was not regarded between P. g. and BOP. Detection rates of A. a., P. i. and B. f were higher for BOP (+) than for BOP (-).
Detection rates of putative periodontopathic bacteria from healthy children 6-18 years of age was higher in this study. The result suggest that it was need searching of children had a high risk facter for periodontal disease in childhood.

View full abstract

Vascular endothelial growth factor (VEGF) is a factor that induces angiogenesis and lymphangiogenesis and increases vascular permeability. VEGF is important in solid cancers for their growth, and its significance as a prognostic factor in cancer patients was also found in clinical studies. c-jun N-terminal kinase (JNK) plays a large role in the regulation of VEGF expression. A human oral squamous cell carcinoma cell line that constitutively expresses VEGF-A and VEGF-C was established. This cell line was treated with an inhibitor of JNK (SP600125), and the relationship between JNK and VEGF-A/VEGF-C expression was studied by real-time reverse transcription-polymerase chain reaction and Western blotting. We found that upon the addition of SP600125, the level of VEGF-A mRNA was elevated up through 12 h in comparison with that in the untreated group, but the level of VEGF-C mRNA was elevated only at 6 h. As to the effect of SP600125 on the protein levels of VEGF-A and VEGF-C, there were reduced levels of VEGF-A and VEGF-C at 3 h and increased levels of these proteins at 6 h. These results indicate that JNK plays a large role in regulating VEGF-A expression at the transcriptional level. As to VEGF-C expression, our results suggested that a molecule (s) other than JNK regulates VEGF-C expression. It was found that SP600125 did not affect the mRNA level and protein level of VEGF-A or VEGF-C in a similar manner, and the possibilities of posttranscriptional control of these proteins and increase in secretory capacity into the culture medium were considered. It is suggested that the levels of c-jun and p-c-jun affect the expression of VEGF-A and VEGF-C in vivo. The present results showed that JNK is involved in the regulation of VEGF-A and VEGF-C expression in oral squamous cell carcinomas.

View full abstract

The indication criteria for surgical orthodontic treatment have not been established due to various factors, and there are no clear criteria for judging whether treatment only by orthodontic treatment is possible.
This case was skeletal mandibular protrusion due to mandibular overgrowth with anterior cross-bite (overjet-5mm, overbite+3.5 mm). Since the frontal facial view showed mandibular deviation in the right direction, surgical orthodontic treatment was indicated. However, the patient did not consent to surgical orthodontic treatment, unusual extraction of 9 teeth including supernumerary teeth was performed, and treatment was performed only by orthodontic treatment.
Since surgical orthodontic treatment was not performed, the following problems remained :
1. Facila asymmetry was not improved.
2. The maxillary median line was not accordant with the mandibular median line.
3. Differences in overjet between the right and left sides were noted.
4. Bucco-lingual torque in the right molar area differed from that in the left molar area.
Furthermore, slightly unstable morphological conditions were found after retention. In performing occlusal reconstruction in cases with remaining skeletal distortion, it was necessary not only to understand the three-dimensional maxillo-facial morphology and stablish treatment goal analyzing further information regarding the relationship with function around the oral cavity, but also to reconsider conventional goal that is the establishment of intercuspation.

View full abstract

The Brånemark System^® Novum is an immediate loading implant system for edentulous mandible. It has some drills and templates that make three fixtures install to 3-dimensional precise positions and direction. A prefabricated lower bar is connected on the three implants. An upper bar, combined with artificial teeth, can settle on the lower bar without casting process. Patients can wear the superstructure at the same or next day of the surgery because the prosthetic procedure has been very simplified.
We apply this system to a 62 years old male patient with periodontally hopeless mandibular dentition because he strongly asked for a treatment schedule with short time period. After one year, he has no trouble and extermetly satisfied with the treatment result.
This report describes the clinical course of the patient and discusses the diagnostic process for the application of the system.

View full abstract