We used two-dimensional finite element analysis to compare the mechanical reaction in tissues surrounding the mandibular central incisors for cases where force was applied to the lingual and labial sides of the teeth. Using preoperative and postoperative cephalograms, movements of the mandibular central incisors during orthodontic treatment with lingual fixed appliances were compared to movements with labial fixed appliances during leveling of the mandible in non-extraction cases. Both studies indicated that reactive flare-out movements of mandibular central incisors were less with lingual fixed appliances than with labial fixed appliances. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 1-8.

View full abstract

We evaluated early healing at the dentin-gingival tissue interface in rat periodontal defects after the application of enamel matrix derivative (EMD). Palatal dehiscence defects were surgically created on the bilateral maxillary first molars in fifty rats. EMD was applied to cover both sides of the denuded dentin surfaces in the experimental group, and none was applied in the control group. Rats were sacrificed at 1, 3, 5, 7 and 14 days after surgery, and biopsies of the tooth, gingiva and bone were examined with light and electron microscopy.
After one day numerous neutrophils had infiltrated around the EMD. By three days macrophages were prominent and fibroblasts could be identified in the vicinity of the macrophages. At 7 and 14 days the granulation tissue adjoining the dentin surface was more cell-rich than in the control group. Furthermore, odontoclasts were observed in all of the specimens at 14 days in the experimental group. These findings indicate that macrophages, which appear in the very initial stage of healing following the application of EMD, play an essential role in the proliferation of fibroblasts and the appearance of odontoclasts. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 9-24.

View full abstract

We investigated the effect of hyaluronic acid on the healing process in rat tooth extraction sockets. Hyaluronic acid was placed in the socket of the experimental group after extraction of the mandibular first molar. Distilled water was applied in the control group. At 3, 7, and 12 days after extraction, the rats were euthanized and perfused with 10% formalin. Histological slide specimens were then decalcified and stained with hematoxylin-eosin. Twelve days after extraction, the border between the basal cell layer of the epithelium and the lamina propria in the experimental group was more irregular than that of the control group. We concluded that application of hyaluronic acid promoted the healing process in tooth extraction sockets. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 25-31.

View full abstract

We investigated changes in the cell-cycle regulatory proteins in malignant cells from rat tongue carcinoma that had been chemically induced by 4-nitroquinoline 1-oxide. We found a decreased expression of p 27^Kip1 in carcinoma using immunohistochemistry and immunoblotting. Lysate from carcinoma cells showed an induced expression of cyclin E, cyclin D₁ and CDK 4 compared with lysate from normal cells. We found that fragments of 22 kD were produced by breakdown of p 27^Kip1 at the N-terminus when we used immunoblotting with two types of polyclonal anti-p 27^Kip1 antibodies, C-19 and N-20, which recognize the C-terminus and the N-terminus, respectively. In order to demonstrate the involvement of ubiquitin-dependent proteolysis, we incubated tumor cells with ubiquitin and proteasome inhibitors and examined the lysates by immunoblotting. We found a ladder pattern of multiple C-19 positive bands, which indicates polyubiquitination. Since these multibands were not seen in the samples incubated without proteasome inhibitors, we concluded that the ubiquitin-proteasome proteolytic system contributes to the breakdown of p 27^Kip1 in this carcinoma model. A decrease of p 27^Kip1 and an increase of cyclin E, cyclin D₁, and CDK 4 in the cells may contribute to the transformation from cellular quiescence that could result in carcinogenesis. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 32-38.

View full abstract

Periodontitis is a chronic inflammatory disease with the complication of bone resorption in its advanced stage. I investigated the possible involvement of two molecules, fractalkine and RANKL, in the development of periodontitis. Fractalkine is a membrane-bound chemokine with a CX₃C motif. In addition to being a chemokine, fractalkine has the properties of an adhesion molecule. Receptor activator of NF-κB ligand (RANKL), originally reported as osteoclast differentiation factor, plays a pivotal role in differentiation of osteoclast precursor cells to osteoclasts, and is considered a key molecule in the process of bone resorption. I carried out immunohistochemical studies of fractalkine and RANKL in human gingiva and in lipopolysacchride (LPS)-injected mice.
Although positive immunoreactivities to fractalkine and RANKL have been identified in submucosal vessels of both normal and inflammatory human gingiva, inflammatory gingival tissue is stained more strongly. In contrast, anti-fractalkine antibody did not stain tissues from the heart, liver or kidney of either control or LPS-injected mice.
The results suggest that fractalkine and RANKL are important molecules in the pathogenesis and progression of human periodontitis. However, they were not identified in various visceral organs under conditions of acute inflammation produced by an experimental model in mice. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 39-47.

View full abstract

We investigated how providing the patient with detailed information about his dental treatment and multiple dental treatment visits reduced stress. Eighteen healthy subjects were divided into two groups, one was given detailed informed consent and the other was not. Saliva samples were collected repeatedly during the experimental dental treatment procedures. The treatment procedures were oral examination, dental anesthesia, dental scaling, and impression taking. We recorded the state-trait anxiety inventory, and the visual analogue scale relating to anxiety and pain. The procedures were administered over a two day period. Salivary hormone concentrations were measured by the enzyme immunoassay method, and all data were compared by the analysis of variance and multiple comparison. We found that when the patient was provided with detailed information about the treatment, and when he acquired adaptation by multiple visits, the stress of dental treatment was reduced. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 48-54.

View full abstract

We observed change in the bone with autologous or heterologous transplantation of teeth in bone defects of dogs. Three openings were made in each side of the femora in three adult male beagle dogs. An opening that did not receive a transplant was used as a control, and autologous transplanted dog teeth or heterologous transplanted rat teeth marked with alizarin red were transplanted in the other defects. Calcein was injected three weeks later, and the dogs were sacrificed one week after that. The bone was then removed from the animals, and all defects were divided through the center to make two samples. One group was observed with a confocal laser scanning microscope, and the other with a light microscope.
Both compact bone and bone marrow were regenerated in the bone defect that did not receive the transplant. In the case of the autologous transplanted teeth, there was bone resorption, some repair of the bone defect and growth of new bone. In the case of the heterologous transplanted teeth, there was no tooth resorption, granulation was seen around the tooth, and there was little bone growth. The autologous transplanted tooth induced bone regeneration and resorption. Although immunological rejection was pronounced in the heterologous transplanted teeth, there was little tooth resorption or bone regeneration. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 55-62.

View full abstract

We attempted to determine if there is a relation between occlusal status and bone mineral density (BMD) in the calcaneus. The subjects were 100 women, between 34 and 87 years of age, who visited the Department of Prosthodontics Clinic of Osaka Dental University Hospital. Premenopausal women and those with prior use of hormone replacement therapy were not included. BMD was evaluated by ultrasonic measurements of the calcaneus using the Achilles system and the subjects were divided into three groups based on their BMD (<70.1, 70.1-78.8, >78.8). The occlusal status at the first visit was retrospectively assessed based on hospital records, and categorized according to Eichner's classification. The covariates simultaneously considered in the analysis by the logistic regression model were : age at first visit, years since first visit, loss of occlusal support, use of removable dental prostheses, age at menopause, history of hysterectomy and ovariectomy, oral conditions, body mass index, and tobacco use. A poor occlusal status at the first visit was significantly associated with decreased BMD, The multivariate odds ratio (mul-OR) and 95% confidence intervals (95% Cl) calculated with the proportional odds model were 3.17 (0.93-10.85) and 5.11 (1.02-25.62) for class B and C versus class A, respectively, in model-I. There was a significant dose-response relation (Trend p=0.030). Mul-OR and 95% Cl were 2.49 (0.73-8.47) and 8.75 (1.77-43.31) for class B1-B3 and B4+C versus class A, respectively, in model-II. There was a significant dose-response relation (Trend p=0.008). We found that there was a strong association between poor occlusal support in the molar region and bone loss in the calcaneus.

View full abstract

The cytokeratin 19 (CK 19) gene tends to reflect the degree of tumor differentiation. We used the reverse transcription polymerase chain reaction (RT-PCR) and Northern blotting to investigate the expression of the CK 19 gene during carcinogenesis of the mouse tongue induced by 4-nitroquinoline-1-oxide (4 NQO). We also examined the influence of 4 NQO on the mouse tongue with the specific objective of determining the carcinogenicity of that substance in this model system. In addition, we analyzed MMP3 and ETS-1 using RT-PCR and immunohistochemisty. CK 19 mRNA was expressed weakly in normal epithelium, moderately in dysplasia, and strongly in verrucous carcinoma. However CK 19 mRNA expression was weak in the invasive carcinoma. These results indicate that the CK 19 gene is more actively transcripted in epithelial dysplasia and cancer cells than in normal epithelial cells. Futhermore, CK 19 is an important determinant of cell conformation. Its overexpression in oral SCCs decreases their invasive potential by diminishing migratory capability. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 72-79.

View full abstract

The beneficial properties of green tea and its components are increasingly being reported in scientific literature. Green tea and its components inhibit carcinogenesis, tumor proliferation, invasion, metastasis and angiogenesis. Although epigallocatechin-3-gallate (EGCG) and epicatechin (EC) are major components of green tea flavanol, their on cellular signal transduction is not well understood. We investigated how EGCG and EC affect proliferation, telomerase activity, multidrug resistance 1 (MDR 1) mRNA expression, and topoisomerase (TOPO) mRNA expression in HSC 4 cells.
We found that EGCG inhibited proliferation of HSC 4 cells, while EC seemed to enhance the growth inhibition that was induced by EGCG in HSC 4 cells. In addition, telomerase activity was inhibited in both the EGCG and EC treated groups. There was no difference between the controls and either the group treated with EGCG or the one treated with EC. Also, there was no significant difference between MDR 1 mRNA and TOPO mRNA expression in the groups treated with EGCG or EC. We found that the expression of MDR 1 and TOPO mRNA was inhibited in both the EGCG and EC treated groups. These results indicate that EGCG might be beneficial as a new antitumor agent. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 80-85.

View full abstract

We attempted to determine whether occlusal contacts of the maxillary premolars and molars changed with age. Silicone occlusal registration was taken for five subjects each in three age groups, young, middle-aged and elderly. The subjects had no restorations with full occlusal coverage. All readings were taken at 30% of maximum voluntary clenching in the intercuspal position. A non-contact three-dimensional form measuring device (Surflacer VMS-250 R, Unisn Inc., Osaka, Japan) digitized the silicone occlusal registration. The three-dimensional data were analyzed by CAD software (Surfacer, Imageware Inc., Michigan, USA) with a personal computer.
The occlusal surfaces of the maxillary premolars were divided into four regions : the buccal cusp, lingual cusp, mesial marginal ridge, and distal marginal ridge. The occlusal surfaces of the maxillary molars were divided into six regions : the mesiobuccal cusp, distobuccal cusp, mesiolingual cusp, distolingual cusp, mesial marginal ridge, and distal marginal ridge. We evaluated the occlusal contacts, which were defined as less than 60μm of silicone thickness between opposing teeth, and analyzed their number, rate, area, and orientation.
We found that occlusal contacts on the functional cusps were significantly different between the young and middle-aged, and between the young and elderly. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 86-96.

View full abstract

We evaluated masticatory function by simultaneously recording masseter muscle activity, lower-jaw movement, and changes of pressure in the temporomandibular joint (TMJ). Intra-articular pressure (IAP) was measured in 10 temporomandibular joints of 10 subjects who did not exhibit any history of functional disturbances, subjective signs or objective symptoms. The IAP pressure transducer needle was inserted into the upper compartment of the TMJ to record IAP during mastication of rice. During mastication, we simultaneously recorded IAP, and myoelectric signals from both the left and right masseter muscles. In addition, incisal point movement was tracked by a mandibular kinesiograph. In order to determine the parameters for opening-and-closing of the mouth, masticatory muscle activity, and changes in joint pressure, we measured four parameters : the duration from the start of masseter muscle activity to the start of mouth closing, the time from the start of intercuspation to the start of pressure development in the joint, the time from the end of masseter muscle activity to the start of opening of the mouth, and the time from the start of opening of the mouth to the start of pressure decrease in the joint.
We found significant differences for each cycle. We observed that mouth closing begins simultaneously with masseter muscle activity, and IAP increases along with chewing. Furthermore, opening of the mouth begins simultaneously with a decrease in masseter muscle activity, resulting in decreased IAP. These results suggest that masticatory movement is performed by the coordinated movement of the mouth, masticatory muscles, and TMJ. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 97-104.

View full abstract

Green tea has been reported to have various biological effects, such as inhibition of tumor invasion, inhibition of cell proliferation, and induction of apoptosis. Epigallocatechin-3-gallate (EGCG) and epicatechin (EC) are major components of green tea flavanol. However, the effect of EGCG/EC on intracellular signal transduction is unknown. Interleukin-6 (IL-6) is a cytokine that has various effects on cellular activation. To determine the influence of IL-6 and EGCG/EC on cellular signal transduction, we investigated tyrosin phosphorylation of Janus Kinase (JAK) /Signal-transducer and activator of transcription (STAT) on HSC 4 cells treated with IL-6 and/or EGCG/EC.
We found that IL-6 induced upregulation of JAK/STAT tyrosine phosphorylation, while EGCG/EC inhibited upregulation of JAK/STAT tyrosine phosphorylation induced by IL-6. In addition, EGCG/EC induced apoptosis of HSC 4 cells. These findings indicate that EGCG is useful as an antitumor agent. Shika Igaku (J Osaka Odontol Soc) 2003 Mar; 66(1): 105-111.

View full abstract

To elucidate the fluctuation of decorin mRNA during the process of inflammation, we examined its expression incultured human gingival fibroblasts stimulated by interleukin (IL)-1β using a real time polymerase chain reaction detection system. Transforming growth factor (TGF)-β, type I collagen, matrix metalloproteinase (MMP)-3 and IL-6 mRNA expression were also investigated. Decorin mRNA in fibroblasts stimulated by IL-1β was expressed weakly at 3 h, and increased significantly at 24 h. These results indicate that gingival fibroblasts stimulated by IL-1β actively express IL-6 mRNA as an early event of inflammation, followed by decorin, collagen, TGF-β and MMP-3 as later events coexisting with destruction and repair.

View full abstract

We investigated the effect of hyaluronic acid on the healing process in rat tooth extraction sockets. In the experimental group, hyaluronic acid was placed in the socket after extraction of the mandibular first molar. Distilled water was applied in the control group. At 3, 7, and 12 days after extraction, the rats were euthanized and perfused with 10% formalin. Histological slide specimens were then decalcified and stained with hematoxylin-eosin. Twelve days after extraction, the border between the basal cell layer of the epithelium and the lamina propria in the experimental group was more irregular than that of the control group. We concluded that application of hyaluronic acid promoted the healing process in tooth extraction sockets.

View full abstract

We investigated failure of the blood-nerve barrier (BNB) using a complete Freund's adjuvant (CFA) model, a Hashimoto model, an axotomy model, and a chronic constriction nerve injury (CCI) model. We also investigated whether thalidomide inhibited BNB failure. The CFA model did not show BNB failure, although the other three did. We found that administration of thalidomide to the CCI model inhibited failure of the BNB.

View full abstract

Fractalkine is a chemokine involved in the formation of inflammatory lesions and RANKL is a molecule that plays a pivotal role in bone resorption. Periodontitis is a chronic inflammatory disease that can cause alveolar bone resorption in its advanced stages. We carried out immunohistochemical studies of fractalkine and RANKL in human gingival tissue to see how they are involved in this process. Immunoreactivity for both fractalkine and RANKL were found in endothelial cells of human gingival submucosal vessels. These results suggest that fractalkine and RANKL are important molecules in the pathogenesis and progression of human periodontitis.

View full abstract

The purpose of this study was to evaluate early healing at the dentin-gingival tissue interface in rat periodontal defects after the application of EMD. At one day, numerous neutrophils had infiltrated around the EMD. At three days, macrophages were prominent, and fibroblasts could be identified in the vicinity of macrophages. At 7 and 14 days, the granulation tissue adjoining the dentin surface was more cell-rich than in the control group. Furthermore, odontoclasts were observed in all of the specimens at 14 days in the experimental group. These findings indicate that macrophages, which appear in the very early stage of healing following the application of EMD, play an essential role in the proliferation of fibroblasts and the appearance of odontoclasts.

View full abstract

We evaluated the effect of various periodontal treatments, which included scaling alone, scaling before and after treatment with YAG and CO_2 lasers, root planing alone and root planing before and after treatment using YAG and CO_2 lasers. Evaluations were carried out using an X-ray microanalyzer (XMA), by scanning electron microscopy (SEM), by X-ray photoelectron spectroscopy (ESCA), and by measuring the contact angles in vitro. There was little difference whether irradiation was done before or after treatment, regardless of the method of evaluation.

View full abstract

I measured lip and tongue forces against the central incisors in open bite patients who had a tongue thrust habit to investigate the relationship between these forces and craniofacial morphology. In open bite patients, only the tongue forces were abnormal. Forces on the cervix of the maxillary central incisors were smaller than normal while those on the cervix of the mandibular were larger. I compared craniofacial morphology and the tongue forces against the mandibular central incisors of open bite patients on swallowing. A high correlation was seen between tongue force and occlusal plane angle, interincisal angle, and L 1 to the mandibular plane angle. The results suggest that as the tongue position on swallowing becomes lower, the occlusal plane angle and L 1 to the mandibular plane angle become larger. However, the interincisal angle becomes smaller.

View full abstract

Pressure is exerted against the violinist's mandible when he plays the instrument. I compared the craniofacial morphology of violinists with that of patients with mandibular deformities using standardized frontal cephalograms. The subjects included 10 violinists and 15 patients with mandibular deformities. I collected data for the zygoma line, mastoidate line, anterior nasal spine to menton line, condylion line, antegonion notch line and the maxillary molar line. Correlation analysis was done on all of these lines. Among violin players, a significant correlation (p<0.01) was found between the antegonion notch line and the zygoma line. A significant correlation (p<0.05) was also found between the antegonion notch line and the anterior nasal spine to menton line. The same was true for the antegonion notch line and condylon line. Among mandibular deformity patients, a significant correlation (p<0.01) was found between the antegonion notchline and the anterior nasal spine to menton line. The condylon line and zygoma line had the same significant correlation. A significant correlation (p<0.05) was found between the antegonion notch line and maxillary molar line. I found that the temporal bone and mandible were deformed in a similar manner.

View full abstract

We investigated the effect of the light exposure conditions for three common curing-lights : the halogen lamp, the xenon lamp and the light emitting diode (LED). We studied the light spectrum, shrinkage of the resin, Knoop hardness of the resin, tensile bond strength to dentin, and the contraction gap between the resin and dentin. We found that rapid curing generated a high rate of contraction gaps. However, there was no significant difference in resin curing or tensile bond strength to dentin between the three types of lights.

View full abstract

I investigated the operating postures of 101 dentists during cavity preparation in order to determine the optimal position for reduction of physical stress to the waist. The dentists did disto ・ occlusal cavity preparations in the right and left maxillary first molars, and a mesial class III cavity preparation in the maxillary left central incisor of a mannequin head using their habitual posture. Increasing the height of the position of the mannequin head (MP) increased the operator's eye position (EP). The greatest MP and greatest EP were recorded with the operator at the 12 o'clock position, using a mirror. No relation ship was found between the height of the stool and EP. The findings suggest that the higher the position of patient's oral cavity, the lower was the operator's physical stress.

View full abstract

We measured dopamine release from the prefrontal cortex of rats with occlusal interferences to clarify the relationship of the interferences with psychiatry stress responses, and used diazepam to show whether increased dopamine release was caused by anxiety. Dopamine release was measured using the microdialysis method. We measured it before and after the animals were given food pellets. The amount of dopamine released was significantly increased in the occlusal interference group. When the diazepam was intraperitoneally administered before the rats were fed, the amount of dopamine release was not increased in either the interference group or the controls. The amount of dopamine release was increased in the rats with occlusal interferences when they were fed, and diazepam suppressed this increase. These findings suggest that occlusal interferences induce anxiety in rats when they are fed.

View full abstract

We investigated how providing the patient with detailed information about his dental treatment and multiple dental treatment visits reduced stress. Eighteen healthy subjects were divided into two groups, one was given detailed in formed consent and the other was not. Saliva samples were collected repeatedly during the experimental dental treatment. We recorded the state-trait anxiety inventory, and the visual analogue scale about anxiety and pain. The procedures were administered over a two day period. Salivary hormone concentrations were measured by the enzyme immunoassay method, and all data were compared by the analysis of variance. We found that when the patient was provided with detailed information about the treatment, and when he acquired adaptation by multiple visits, the stress of dental treatment was reduced.

View full abstract

Hepatocyte growth factor (HGF), a multifunctional cytokine, mediates the interaction between mesenchymal cells and epithelial cells. We investigated mRNA expression of type I collagen and decorin in human gingival fibroblasts stimulated by HGF. We quantitatively analyzed mRNA expression using a real-time reverse trancriptase-polymerase chain reaction (RT-PCR) detection system. The mRNA expression of decorin increased significantly 12 hours after HGF stimulation, while that of collagen increased markedly at 24 hours. There was trace expression of IL-6 mRNA in both the experimental group and the controls. These results indicate that HGF may induce synthesis in the gingival fibroblasts of the extracellular matrix by an autocrine effect.

View full abstract

Analysis of malodorous components of the breath requires a large experimental facility. We recently developed breath detection equipment that had ammonia, not methyl mercaptan, as its target. We found that the amount of ammonia in a healthy subject was less than 16 ppm. There was a significant positive correlation between the amount of ammonia measured by the breath inspection equipment and that of methyl mercaptan detected by gaschromatography in 12 patients with periodontal disease who had halitosis. Also there was a positive correlation between the amount of ammonia, clinical findings, and the bacteria count indicated by a phase contrast microscope. We found that the amount of ammonia decreased after initial preparation for periodontal therapy.

View full abstract

We studied differences in the amount and direction of mandibular displacement between healthy adults and volunteers with temporomandibular joint (TMJ) noise. Two silicone occlusal registrations were taken for each of six healthy adults and six volunteers with TMJ noise. The mandibular displacement was estimated by the relationship of the maxillary and mandibular occlusal surfaces. Mandibular displacement in the volunteers with TMJ noise was larger than that in the healthy adults. Displacement of the mandibular dentition was upward, while displacement of the condyle was to the posterior in all of the volunteers with TMJ noise. These results suggest that mandibular displacement from habitual occlusal position to intercuspal position is associated with noise in the joint.

View full abstract

We studied differences in the amount and direction of mandibular displacement between healthy adults and volunteers with temporomandibular joint (TMJ) noise. Two silicone occlusal registrations were taken for each of six healthy adults and six volunteers with TMJ noise. The mandibular displacement was estimated by the relationship of the maxillary and mandibular occlusal surfaces. Mandibular displacement in the volunteers with TMJ noise was larger than that in the healthy adults. Displacement of the mandibular dentition was upward, while displacement of the condyle was to the posterior in all of the volunteers with TMJ noise. These results suggest that mandibular displacement from habitual occlusal position to intercuspal position is associated with noise in the joint.

View full abstract