Biomedical subjects

Kazutaka Kasai

Publications and source records attributed to Kazutaka Kasai.

At least 19 recordsLinked to original sources

PubMed2006

Low-energy irradiation stimulates formation of osteoclast-like cells via RANK expression in vitro.

Low-energy laser irradiation (Ga-Al-As semiconductor laser, output 50 mW) was applied to rat osteoclast precursor cells for 1, 3, 6, or 10 min at 24-h intervals during the culture period. The number of tartrate-resistant acid phosphatase positive multinucleate cells was increased by approximately 1.3-fold in the 3- and 6-min irradiation groups. Further, osteoclasts appeared on day 2 in the laser irradiation groups but not until day 3 in the control groups. In immunohistochemical staining for receptor activator of NF-kappaB (RANK), the laser irradiation groups showed significantly greater amounts of staining in comparison with the control group on days 2 and 3. Reverse transcription-polymerase chain reaction results also showed that the expressions of RANK were upregulated. In the pit formation assay, resorption pits were significantly more abundant in the laser irradiation groups than in the controls. The present results suggest that low-energy laser irradiation facilitates differentiation and activation of osteoclasts via RANK expression.

Animals↗

PubMed2006

Shear bond strength of calcium phosphate ceramic brackets to human enamel.

The aim of this study was to examine the shear bond strength between Hyaline brackets, a new type of calcium phosphate ceramic bracket, and human enamel using various types of adhesive resin and to investigate the effectiveness of a silane-coupling agent to bond Hyaline to human enamel. Kurasper F, Light Bond, Super Bond C&B, and Transbond XT were used as adhesive resins, and Porcelain Liner M was used as the silane-coupling agent. The Hyaline bracket was bonded to human enamel using one of the above adhesive resins according to the manufacturer's instructions. After applying the Porcelain Liner M to Hyaline, the Hyaline bracket was also bonded to enamel using one of the above adhesive resins according to the manufacturer's instructions. The shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours. Three types of adhesive resin, Kurasper F, Light Bond, and Super Bond C&B, produced clinically acceptable shear bond strength with and without Porcelain Liner M. Transbond XT produced significantly lower bond strength to enamel with or without Porcelain Liner M (P < .05). The application of Porcelain Liner M was not useful for improving the bond strength of Hyaline to enamel. The adhesive remnant indices were not significantly different among four adhesive resins. In conclusion, adhesive resins such as Kurasper F, Light bond, and Super Bond C&B are useful for bonding esthetic Hyaline brackets to human enamel.

Analysis of Variance↗

PubMed2006

Modification of 4-META/MMA-TBB resin for safe debonding of orthodontic brackets--influence of the addition of degradable additives or fluoride compound.

The purpose of this study was to evaluate the performance of modified 4-META/MMA-TBB resin cements (Superbond C&B) in terms of debonding orthodontic brackets easily and safely from enamel without the loss of proper bracket bond strength. Poly (DL-lactide-co-glycolide) (PLGA), calcium fluoride (CaF2), or alpha-tricalcium phosphate (alpha-TCP) was added to the polymer powder of 4-META/MMA-TBB resin, and the shear bond strength of orthodontic brackets to human enamel using modified resins was measured before and after 10,000-cycle thermal cycling test between 5 degrees C and 55 degrees C. The modified resins tended to provide lower bond strength compared with the original 4-META/MMA-TBB resin. However, alpha-TCP- or CaF2-modified resin showed no significant differences in bond strength before and after thermal cycling. Moreover, there was a tendency of more residual resin remaining on the tooth surface after debonding, thereby suggesting a lower risk of enamel fracture. In conclusion, alpha-TCP- or CaF2-modified 4-META/MMA-TBB resin seemed to allow easy and safe debonding of orthodontic brackets without loss of proper bracket bond strength.

Acid Etching, Dental↗

PubMed2005

Relationship between substance P and interleukin-1beta in gingival crevicular fluid during orthodontic tooth movement in adults.

Metabolism by peptidases plays an important role in modulating the levels of biologically-active neuropeptides, while that of substance P (SP), a component of gingival crevicular fluid (GCF), may potentiate the inflammatory process in orthodontic tooth movement. The aim of this study was two-fold: (1) to investigate GCF levels of SP and interleukin-1beta (IL-1beta) during human orthodontic tooth movement, and (2) to determine the correlation coefficients between SP and IL-1beta levels in the GCF. The subjects were 3 males, with a mean age of 21.3 +/- 2.8 years old, and 6 females, with a mean age of 23.1 +/- 2.4 years, undergoing orthodontic movement of a single tooth, with the contralateral tooth used as the control. GCF was sampled at the control and treatment (compression) sites before and 1, 4, 8, 24, 72, 120, and 168 hours after initiation of orthodontic treatment. Prevention of plaque-induced inflammation allowed assessment of the dynamics of mechanically stimulated SP and IL-1beta levels in the GCF, which were determined using enzyme-linked immunosorbent assay (ELISA) kits. GCF levels of SP and IL-1beta for the treated teeth were significantly higher (P < 0.001) than for the corresponding control teeth from 8 to 72 hours, and peaked at 24 hours. These results show that the amounts of SP and IL-1beta in GCF increase with orthodontic tooth movement, and indicate that such increases may be involved in inflammation in response to mechanical stress.

Adult↗

PubMed2005

Relationship between masticatory function and internal structure of the mandible based on computed tomography findings.

INTRODUCTION: The purposes of this study were to investigate bone mineral density as a part of bone construction in human skulls and to examine the relationship between dentofacial morphology and masticatory function by using computed tomography (CT) findings. Changes in bone mineral density in the mandible because of loss of masticatory function were tested in rats by experimentally producing an environment that inhibited mastication by the molars. METHODS: Data for the human study were obtained from 27 modern male Japanese skulls (mean age, 28 years) from the University of Tokyo. Cortical bone thickness (CBT) and CT value (CV) were measured by each CT scan of the first and molars. For the animal study, a metal cap was inserted between the maxillary and mandibular incisors to prevent the molars from biting in 6-week-old male Wistar rats. The rats were killed after 2, 4, or 6 weeks, and bone mineral density was measured in cancellous and cortical bone equivalent to the first molar region by using peripheral quantitative computed tomography. RESULTS: In the human skull study, significant negative correlations were observed between CV in the regions of the buccal side of the second molar and the angle between the Frankfort horizontal and mandibular planes. Significant negative correlations were also observed between the gonial angle and CV in the buccal and basal sides. In the animal study, cancellous bone mineral density began to decline 4 weeks after the start of the experiment in the masticatory hypofunction group compared with the control group. By week 6, cancellous bone density had declined by 11.6% on the buccal side, 16.7% on the lingual side, 12.3% at the bifurcation of the root, and 38.1% at the root apex. Cortical bone density declined by 8% to 12% on the lingual side. CONCLUSIONS: The results support our hypothesis that a functional adaptive response by the mandible to mechanical stress resulting from mastication occurs not only in the muscle insertion area, but also in mandibular alveolar bone in the molar region.

Adaptation, Physiological↗

PubMed2005

Bonding durability of using self-etching primer with 4-META/ MMA-TBB resin cement to bond orthodontic brackets.

This study determines the bonding durability when a self-etching primer is used with Superbond C&B (a 4-methacryloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butyl borane resin) to bond orthodontic brackets to enamel. Thermocycling test was used to assess bonding durability. Metal brackets were bonded to the phosphoric acid-etched or Megabond self-etching primer-treated enamel surface of human premolars using Superbond C&B. The shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours or after 2000 or 5000 cycles of thermocycling between 5 degrees C and 55 degrees C. Data were analyzed using 2-way analysis of variance and Fisher's protected least significant difference test for multiple comparisons. There was no significant difference in shear bond strength between phosphoric acid and Megabond self-etching primer treatment before the thermocycling test. After 2000 and 5000 thermal cycles, significant decreases in shear bond strength were observed with phosphoric acid etching. On the contrary, no significant differences in shear bond strength were observed after 2000 and 5000 thermal cycles with Megabond self-etching primer. The adhesive remnant indices were not significantly different between phosphoric acid etching and Megabond self-etching primer treatment either before or after thermal cycles. This study suggested that when used with Superbond C&B in bonding orthodontic brackets, Megabond self-etching primer is superior to phosphoric acid as an enamel preparation agent in providing durable bond strength.

Acid Etching, Dental↗

PubMed2005

Effect of thermal cycling on shear bond strength with different types of self-etching primer for bonding orthodontic brackets using a MMA-based resin.

The purpose of this study was to determine the bonding durability when orthodontic bracket was bonded to human enamel using a MMA-based resin (Multibond) with two types of commercially available self-etching primer - Multibond and Megabond. Multibond primer contained a polymerization initiator, but Megabond primer did not. No significant differences in shear bond strength were observed between Multibond and Megabond primers after immersion in water at 37 degrees C for 24 hours (before thermal cycling). Multibond primer produced no significant decrease in shear bond strength after 2000 and 5000 thermo-cycles between 5 degrees C and 55 degrees C. On the contrary, Megabond primer showed significant decrease in shear bond strength after thermal cycling. The present study suggested that if Multibond resin were to be used for bonding orthodontic brackets, difference in self-etching primer's components would influence shear bond strength after thermal cycling.

Acid Etching, Dental↗

PubMed2005

Levels of t-PA and PAI-2 in gingival crevicular fluid during orthodontic tooth movement in adults.

BACKGROUND: The regulation of plasminogen activation is a key element in controlling proteolytic events in the extracellular matrix. OBJECTIVE: The aim of this study was to investigate gingival crevicular fluid (GCF) levels of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI -2) during orthodontic tooth movement in adults. METHODS: Five male subjects (Mean age: 22.5 +/- 2.8 years) and five female subjects (Mean age: 23.4 +/- 3.9 years) were used. Each subject had one upper canine retracted into an extraction space. The contralateral and opposing canines, which were not moved, served as controls. GCF was collected at the distal cervical margins of the experimental and control teeth 0, 1, 24, and 168 hours after a retracting force was placed. GCF levels of t-PA and PAI-2 were determined by commercially available ELISA kits. RESULTS: After 24 hours of tooth movement the levels of t-PA and PAI-2 in the GCF were significantly higher from the experimental canines compared with the control teeth. There were no significant experimental-control differences at 0, 1, and 168 hours. There were no differences in the total protein levels up to 168 hours after orthodontic tooth movement. CONCLUSIONS: These results indicate that the amounts of t-PA and PAI-2 in the GCF increase with orthodontic tooth movement, and suggest that such increases may be involved in extracellular matrix degradation in response to mechanical stress. Failure to detect elevated levels of t-PA and PAI-2 at 168 hours was attributed to decay of the force retracting the canines.

Adult↗

PubMed2004

Genetic contribution to dental arch size variation in Australian twins.

The aim of this study was to quantify the relative contributions of genetic and environmental factors to variations in dental arch breadth, length and palatal height in a sample of Australian twins, and to estimate heritabilities using modern model-fitting methods. Dental casts of 20 male and 24 female monozygous (MZ) twin pairs, 17 male and 8 female dizygous (DZ) twin pairs, and 9 opposite-sexed DZ twin pairs were selected from the collection of records of twins housed at the Adelaide Dental School. The mean ages of subjects were 15.8 +/- 3.5 years (MZ) and 17.0 +/- 4.7 years (DZ). Dental casts were scanned using a contact-type 3D scanner, PICZA interfaced to a personal computer running 3D-Rugle3 software. Data were subjected to univariate genetic analysis with the structural equation modelling package, Mx, using the normal assumptions of the twin model. A model incorporating additive genetic (A) and unique environmental (E) variation was found to be the most parsimonious for dental arch breadth and length, and palatal height. Estimates of heritability for dental arch breadth ranged from 0.49 to 0.92, those for arch length from 0.86 to 0.94, and those for palatal height were 0.80 and 0.81, respectively. These results indicate a high genetic contribution to the variation in dental arch dimensions in mainly teenage twins.

Adolescent↗

PubMed2004

Efficacy of using self-etching primer with a 4-META/MMA-TBB resin cement in bonding orthodontic brackets to human enamel and effect of saliva contamination on shear bond strength.

The objective of this study was (1) to evaluate the effectiveness of Megabond when used with Superbond C&B, a 4-methacryloloxyethyl trimellitate anhydride (4-META)/methyl methacrylate (MMA)-tri-n-butyl borane (TBB) resin, to bond orthodontic metal brackets to human enamel and (2) to examine the influence of saliva contamination on shear bond strength. Metal brackets were bonded to phosphoric acid-etched or Megabond-treated human premolars using Superbond C&B resin cement. The effects of saliva contamination after acid etching or self-etch priming, and the effect of re-etching or self-etch priming after saliva contamination on shear bond strength were also assessed. The shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours. Data were analyzed using two-way analysis of variance and Fisher's protected least significant difference test for multiple comparisons. There were no significant differences in shear bond strength between phosphoric acid etching and self-etch priming for no contamination, saliva contamination, and repeat treatment (etching or priming) after saliva contamination. With phosphoric acid etching, saliva contamination significantly decreased the shear bond strength. Repeat phosphoric acid etching after saliva contamination did not significantly improve the bond strengths. With self-etching primer treatment, however, saliva contamination did not cause any decrease of bond strength. Phosphoric acid etching produced more enamel fracture than self-etching primer treatment. Field-emission scanning microscopy revealed less dissolution of enamel surface resulted from self-etching primer compared with phosphoric acid. These results suggest that Megabond when used with Superbond C&B resin cement may be a good candidate for bonding orthodontic brackets to human enamel.

Acid Etching, Dental↗

PubMed2004

Cathepsins B and L increased during response of periodontal ligament cells to mechanical stress in vitro.

Cathepsin is a typical and well-characterized lysosomal cysteine protease that, under pathological conditions, is involved in tissue destruction. A recent immunocytochemical study demonstrated that cathepsins B (CAB) and L (CAL) were localized in the periodontal ligament (PDL) of the rat molar, and they were expressed in compressed sites during experimental tooth movement. Further, we demonstrated previously that the levels of CAB and CAL in gingival crevicular fluid increased during orthodontic tooth movement. Therefore, CAB and CAL may play important roles in the process of collagen degradation during orthodontic tooth movement, and our in vitro study examined the secretion of CAB and CAL in PDL cells following mechanical stress. PDL cells were subjected to 0.5, 1.0, 2.0, or 3.0 g/cm2 of compression force or an increase in surface area by tension force of 0.28%, 0.95%, 1.72%, or 2.50% for 24 hr. For detection of CAB and CAL in conditioned medium, commercially available ELISA kits were used. We found compression and tension significantly increased the secretions of both CAB and CAL in PDL cells, which were exhibited in a time- and force magnitude-dependent manner. The compression-stimulated secretion of CAB was increased approximately 3-fold and that of CAL 4-fold, as compared with the control. Further, tension-stimulated secretion of CAB was increased by 1.5-fold and that of CAL 2-fold compared with the control. When analyzed using a semiquantitative polymerase chain reaction assay, CAB and CAL mRNA were increased in response to both compression and tension forces. These findings demonstrated that mechanical stress (compression and tension forces) causes an increase in secretion of CAB and CAL in PDL cells in vitro.

Adolescent↗

PubMed2004

Bonding durability between orthodontic brackets and human enamel treated with megabond self-etching primer using 4-META/MMA-TBB resin cement.

The purpose of this study was to determine the bonding durability when a Megabond self-etching primer is used with 4-META/MMA-TBB resin to bond metal orthodontic brackets to human premolar enamel. Three conditions of enamel were prepared: Megabond self-etching primer without saliva contamination, Megabond self-etching primer with saliva contamination, and repeat Megabond self-etching priming after saliva contamination. Shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours, or after 2000 or 5000 cycles of thermal cycling between 5 degrees C and 55 degrees C. There were no significant differences in shear bond strength among the three groups not only before thermal cycling, but also after thermal cycling. FE-SEM observation revealed the presence of saliva and reduced amount of resin tag formation after saliva contamination. The present study provided the evidence in human teeth that when using 4-META/MMA-TBB resin, Megabond self-etching primer treatment produced tight bonding even when surface was contaminated with saliva.

Acid Etching, Dental↗

PubMed2004

Prediction and causes of open gingival embrasure spaces between the mandibular central incisors following orthodontic treatment.

BACKGROUND: An open gingival embrasure space (OGES) between the mandibular incisors, also known as a "black triangle" (BT), can be an undesirable outcome of adult orthodontic treatment. OBJECTIVES: The purpose of this study was to determine the parameters that contributed most to the occurrence of an OGES between the mandibular central incisors, the area with the highest incidence of BT in the lower arch following orthodontic treatment. METHODS: A stepwise regression model was used to identify the variables (age, crowding, treatment duration, alveolar bone height, and six variables describing crown morphology) related independently to OGES score. Intra-oral photographs taken before and after orthodontic treatment, study models and intra-oral radiographs of 60 patients were used. Embrasures between the mandibular central incisors were measured and classified into three types: papilla filling, pinpoint, and BT. RESULTS: Age at the first consultation, length of active treatment and maximum crown width were larger in the BT group than in the normal group. In contrast, incisal edge - centre of the contact point, upper contact point - lower contact point, mesial CEJ - distal CEJ, and mesial CEJ - distal CEJ / maximum crown width were smaller in the BT group than in the normal group. Variation in OGES score was explained by the independent contributions of age at the first consultation, duration of active treatment, maximum crown width, and mesial CEJ - distal CEJ width. The multiple regression coefficient was 0.98, and the regression coefficient square was 96 per cent. CONCLUSION: We conclude that age at the first consultation, duration of active treatment, and crown morphology are involved in OGES manifestation. We suggest also that BT occurrence may be predictable prior to treatment.

Adolescent↗

PubMed2003

Tooth wear and the "design" of the human dentition: a perspective from evolutionary medicine.

Worn, flat occlusal surfaces and anterior edge-to-edge occlusion are ubiquitous among the dentitions of prehistoric humans. The concept of attritional occlusion was proposed in the 1950s as a hypothesis to explain these characteristics. The main aspects of this hypothesis are: 1) the dentitions of ancient populations in heavy-wear environments were continuously and dynamically changing owing to life-long attritional tooth reduction and compensatory tooth migration, 2) all contemporary humans inherit these compensatory mechanisms, and recent reduction in wear severity has resulted in failure to develop attritional occlusion, and 3) this failure leads to an increased frequency of various dental problems in modern societies. Because of the potential significance of this concept, we review and synthesize relevant works and discuss attritional occlusion in the light of current knowledge. Available evidence, on balance, supports the first and second points of the hypothesis. As noted by many workers, the human dentition is basically "designed" on the premise that extensive wear will occur, a conclusion that seems reasonable when one realizes that humans evolved in heavy-wear environments until relatively recently. Some dental problems in contemporary societies appear to reflect the disparity between the original design of our dentition and our present environment, in which extensive wear no longer occurs, but this possibility still needs further investigation.

Adaptation, Physiological↗

PubMed2003

Assessing the performance of a methyl methacrylate-based resin cement with self-etching primer for bonding orthodontic brackets.

Questions over the usefulness of a self-etching primer with resin adhesive in the bonding of orthodontic brackets remain unsolved. The purpose of this study was to determine the effects of using Multibond, a new methyl methacrylate (MMA)-based resin cement with self-etching primer, on the shear bond strength of orthodontic brackets compared with Superbond C&B, which is a well-known MMA-based resin cement containing phosphoric acid etching. Metal or plastic brackets were bonded to etched or self-etching primed bovine teeth using Superbond C&B or Multibond. The shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours. Data were analyzed by two-way analysis of variance and Scheffe's test. The surface appearances of the teeth after phosphoric acid etching or self-etching priming were observed by field-emission scanning electron microscopy (FE-SEM). Metal brackets bonded with Multibond had a significantly lower shear bond strength than metal brackets bonded with Superbond C&B. No significant differences in shear bond strength were observed between Multibond and Superbond C&B when plastic brackets were bonded to the enamel. The shear bond strength of metal brackets bonded with Multibond was comparable with that of plastic brackets bonded with Superbond C&B. Adhesive remnant index score showed a tendency of more residual resin cement remaining on the teeth when metal brackets were bonded with Multibond. FE-SEM observation revealed less dissolution of the enamel surface resulting from treatment with Multibond self-etching primer as compared with phosphoric acid. Thus, the Multibond system may be a candidate for bonding orthodontic brackets with the advantage of minimizing enamel loss.

Acid Etching, Dental↗

PubMed2003

Magnetic resonance imaging diagnosis of the temporomandibular joint in patients with orthodontic appliances.

OBJECTIVE: The purpose of this study was to investigate the accuracy of magnetic resonance imaging diagnosis of the temporomandibular joint in those with orthodontic appliances by comparing magnetic resonance images of the temporomandibular joints with and without orthodontic appliances. STUDY DESIGN: Magnetic resonance imaging was performed in a total of 20 temporomandibular joints before and after the insertion of 6 kinds of orthodontic appliances (types 1-6), and the magnetic resonance images were compared. RESULTS: With respect to disk position, the diagnostic accuracy was 80%, 75%, 70%, 70%, 65%, and 60% in order from type 1 through type 6. The distribution of stages for the assessment of condylar configurations was 80%, 55%, 40%, 40%, 20%, and 10% in order from type 1 through type 6. No significant changes were found in the condylar head marrow signals. CONCLUSION: Magnetic resonance imaging is performed in orthodontic patients preferably by using ceramic brackets in the front teeth and direct bonding tubes in the molar teeth while removing arch wires.

Adult↗

PubMed2003

The level of cathepsin B in gingival crevicular fluid during human orthodontic tooth movement.

This investigation examined gingival crevicular fluid (GCF) levels of lysosomal cystein protease, cathepsin B (CAB), during human orthodontic tooth movement. The study included 10 patients (five males, mean age 22.5 +/- 2.8 years and five females, mean age 23.4 +/- 3.9 years), each having one tooth undergoing orthodontic movement, while the contralateral and antagonist teeth were used as the controls. The GCF was sampled at the control and treatment (compression) sites before activation and at 1, 24, and 168 hours. Prevention of plaque-induced inflammation allowed this study to focus on the dynamics of mechanically stimulated CAB levels in GCF. The CAB levels in GCF were determined by fluorospectrometry, using Z-Arg-Arg-MCA as the substrate and by Western blotting analysis. The GCF levels of CAB for the treated teeth were significantly (P< 0.001) higher than those of the control teeth at 24 hours. At the control sites, CAB levels at 24 hours did not change significantly with time. At the experimental site where orthodontic forces were applied, Western blot analysis demonstrated that the molecular forms were 29 kDa mature enzymes. These results indicate that the amount of CAB in GCF is increased by orthodontic tooth movement. This increased CAB may be involved in extracellular matrix degradation in response to mechanical stress.

Adult↗

PubMed2003

Some factors associated with open gingival embrasures following orthodontic treatment.

Open gingival embrasures or "black triangles" can be an undesirable outcome of adult orthodontic treatment. The aims of the present study were to determine the prevalence of open gingival embrasures in a group of orthodontic patients, and to determine if open gingival embrasures were related to: age at the start of treatment, the severity of pretreatment crowding of the mandibular incisors, the duration of treatment or changes in alveolar bone height. The subjects were 80 orthodontic patients (33 males, 47 females) between 15 and 31 years of age. Open gingival embrasures were found in 43.7 per cent of all subjects, while in subjects over 20 years of age the prevalence was 66.7 per cent. In relation to the amount of crowding 42.8 per cent of the subjects with less than 4 mm crowding had open gingival embrasures, 41.2 per cent of those with between 4 and 8 mm crowding had open gingival embrasures, and 50 per cent of those with more than 8 mm crowding had open gingival embrasures. The groups were not significantly different. Approximately 42 per cent of the subjects in the shorter treatment group had open gingival embrasures, and 44.4 per cent of those whose treatment took longer than 3 years had open gingival embrasures. This difference was not statistically significant. Cephalometric measurements of mandibular alveolar bone height indicate that open gingival embrasures were more likely to be due to resorption of the alveolar crest rather than extrusion of the mandibular incisors. In conclusion, open gingival embrasures were more frequently found in patients over 20 years of age than in younger patients, and were associated with resorption of the alveolar crest.

Adolescent↗