Kazutaka Kasai

RANKL Increase in Compressed Periodontal Ligament Cells from Root Resorption

The ligand receptor activator of NFκB (RANKL) plays an important role in osteoclast formation. However, very little is known about the relationship between external apical root resorption during orthodontic treatment and RANKL. We hypothesized that compressive force is responsible for RANKL formation and up-regulation of osteoclastogenesis in periodontal ligament (PDL) cells from patients with severe orthodontically induced external apical root resorption. RANKL and osteoprotegerin (OPG) production, TRAP-positive cells, and resorptive pits were determined. The increase of RANKL and the decrease of OPG were greater in the severe root resorption group than in the non-resorption group. The numbers of TRAP-positive cells and resorptive pits were also increased in the severe root resorption group than in the non-resorption group. These results support the hypothesis that the compressed PDL cells obtained from tissues with severe external apical root resorption may produce a large amount of RANKL and up-regulate osteoclastogenesis.

Relationship between facial types and tooth and bone characteristics of the mandible obtained by CT scanning

The purpose of this study was to evaluate relationships between morphological characteristics of vertical sections of the mandibular body and facial type. Of the correlation coefficients between tooth and bone inclination and facial type parameters, facial height index (FHI) was negatively associated with second premolar (P2), first molar (M1), and second molar (M2) inclinations. The angle represented by Frankfort horizontal plane to mandibular plane (FMA) was negatively associated with bone inclination of the M2 section. The buccal cortical bone was thicker in short-faced individuals than in the average and long-faced groups, while lingual cortical bone thickness of the M1 and M2 sections was greater. The basal cortical bone thickness of the L1 section was greater in the short-faced group, and the inclinations of the P2, M1, and M2 axes were significantly smaller. Teeth in the short-faced group inclined more lingually than in the average- and long-faced groups. The results of this study provide evidence that a significant but complex relationship exists between structures of the mandibular body and facial types. The morphological features that relate to masticatory function and facial types are associated with cortical bone thickness of the mandibular body and the buccolingual inclination of the first and second molars.

Low-energy laser stimulates tooth movement velocity via expression of RANK and RANKL

OBJECTIVE Recent studies have demonstrated that low-energy laser irradiation stimulates bone formation in vitro and in vivo. However, very little is known about the effects of laser irradiation on osteoclastogenesis. The receptor activator of the nuclear factor-kB (RANK) / RANK ligand (RANKL) / osteoprotegerin (OPG) system is essential and sufficient for osteoclastogenesis. The present study was designed to examine the effects of low-energy laser irradiation on expressions of RANK, RANKL, and OPG during experimental tooth movement. DESIGN To induce experimental tooth movement in rats, 10 g of orthodontic force was applied to the molars. Next, a Ga-Al-As diode laser was used to irradiate the area around the moved tooth and the amount of tooth movement was measured for 7 days. Immunohistochemical staining with RANK, RANKL, and OPG was performed. Real time PCR was also performed to elucidate the expression of RANK in irradiated rat osteoclast precursor cells in vitro. RESULTS In the irradiation group, the amount of tooth movement was significantly greater than in the non-irradiation group by the end of the experimental period. Cells that showed positive immunoreactions to the primary antibodies of RANKL and RANK were significantly increased in the irradiation group on day 2 and 3, compared with the non-irradiation group. In contrast, the expression of OPG was not changed. Further, RANK expression in osteoclast precursor cells was detected at an early stage (day 2 and 3) in the irradiation group. CONCLUSION These findings suggest that low-energy laser irradiation stimulates the velocity of tooth movement via induction of RANK and RANKL.

Soft tissue adaptability to hard tissues in facial profiles

The purpose of this study was to investigate soft tissue adaptability to hard tissue. A canonical correlation analysis was performed in an attempt to assess the relationships between hard tissue structure and soft tissue profile in the static state. For the dynamic study, multiple-regression analysis was performed to identify the changes of soft tissue profiles associated with the retraction of upper and lower incisors. The samples comprised lateral cephalograms from 297 Japanese women for the static canonical correlation analysis and 32 sets of lateral cephalograms of pre- and posttreatment adult orthodontic patients for the dynamic multiple-regression analysis. In the static state, the vertical dimension of lower facial height and the position of the lower incisors were associated with the thickness of the upper-lip vermilion and soft tissue B, and the horizontal relationships between upper- and lower-jaw positions were associated with the thickness of upper lips and of pogonion (soft tissue chin). In the dynamic state, the results indicated that the changes of stomion and lower lip could be predicted and strongly reflected the changes of the hard tissue. On the contrary, the change of the upper lip showed a weaker association with the hard tissue changes. Predictions of chin form described by the soft tissue B and soft tissue pogonion were less accurate than estimates of upper- and lower-lip form. Chin form was influenced by the hard tissue structures such as ANB angle and lower-facial height rather than by changes in lower- and upper-incisor retraction.

Effect of Using Self-Etching Primer for Bonding Orthodontic Brackets

Questions over the use of self-etching primers with composite resin adhesives in the bonding of orthodontic brackets remain unsolved. In addition, there are no previous reports on the efficacy of self-etching primers with resin-modified glass ionomer cements for bonding orthodontic brackets in orthodontic dentistry. The purpose of this study was to determine the shear bond strengths of orthodontic brackets bonded with one of four protocols: (1) a composite resin adhesive used with 40% phosphoric acid, (2) the same composite resin used with Megabond self-etching primer, (3) a resin-modified glass ionomer cement adhesive used with 10% polyacrylic acid enamel conditioner, and (4) the same resin-modified glass ionomer cement used with Megabond self-etching primer. The appearance of the tooth surfaces after acid etching or priming was observed with a field-emission scanning electron microscope (FE-SEM). When used with resin-modified glass ionomer cement, Megabond self-etching primer gave no significantly different shear bond strength compared with polyacrylic acid etching. But when used with composite resin adhesive, Megabond self-etching primer gave significantly lower shear bond strength than phosphoric acid etching. However, the shear bond strength of orthodontic brackets bonded with composite resin adhesive after Megabond priming was almost the same as that of brackets bonded with resin-modified glass ionomer cement after polyacrylic acid etching. FE-SEM observation revealed that Megabond self-etching primer produced less dissolution of enamel surface than did phosphoric acid and polyacrylic acid etching. Megabond self-etching primer may be a candidate for bonding orthodontic brackets using the resin-modified glass ionomer cement for minimizing the amount of enamel loss.

Neuropeptides stimulate production of interleukin-1β, interleukin-6, and tumor necrosis factor-α in human dental pulp cells

AbstractObjective:Orthodontic tooth movement causes inflammatory reactions in the periodontal membrane and dental pulp. It has been reported that substance P (SP) and calcitonin gene-related peptide (CGRP), both sensory neuropeptides, are manifested in the dental pulp of rats during experimental tooth movement, suggesting that they might be involved in the dental pulp inflammation during orthodontic tooth movement. However, the relationships between neuropeptides and pro-inflammatory cytokines have not been fully elucidated. Materials and methods:Human dental pulp (HDP) fibroblasts were prepared from 6 healthy young volunteers (3 males, 3 females; 15–25 years old) during the course of orthodontic treatment. HDP cells were incubated for 24 h in fresh medium containing 2% FCS in the presence of various concentrations of CGRP (10–12 to 10–4 M) and SP (10–12 to 10–4 M), and the levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α present in the media were determined using commercially available high-sensitivity enzyme-linked immunosorbent assay kit. Results:We examined the effects of stimulation by these neuropeptides on the production of inflammatory cytokines in HDP fibroblasts, and found that the levels of IL-1β, IL-6, and TNF-α increased in a time- and concentration-dependent manner. However, the neuropeptides did not act synergistically to increase cytokine secretion in HDP cells or significantly modify LPS-induced cytokine production by HDP cells. Conclusions:Our results suggest that human pulp fibroblasts may be involved in the progress of inflammation in pulp tissue during orthodontic tooth movement, as they produced large amounts of IL-1β, IL-6, and TNF-α following stimulation with neuropeptides.

Low-energy laser irradiation facilitates the velocity of tooth movement and the expressions of matrix metalloproteinase-9, cathepsin K, and alpha(v) beta(3) integrin in rats

It has previously been reported that low-energy laser irradiation stimulated the velocity of tooth movement via the receptor activator of nuclear factor kappa B (RANK)/RANK ligand and the macrophage colony-stimulating factor/its receptor (c-Fms) systems. Matrix metalloproteinase (MMP)-9, cathepsin K, and alpha(v) beta(3) [alpha(v)beta3] integrin are essential for osteoclastogenesis; therefore, the present study was designed to examine the effects of low-energy laser irradiation on the expression of MMP-9, cathepsin K, and alpha(v)beta3 integrin during experimental tooth movement. Fifty male, 6-week-old Wistar strain rats were used in the experiment. A total force of 10g was applied to the rat molars to induce tooth movement. A Ga-Al-As diode laser was used to irradiate the area around the moving tooth and, after 7 days, the amount of tooth movement was measured. To determine the amount of tooth movement, plaster models of the maxillae were made using a silicone impression material before (day 0) and after tooth movement (days 1, 2, 3, 4, and 7). The models were scanned using a contact-type three-dimensional (3-D) measurement apparatus. Immunohistochemical staining for MMP-9, cathepsin K, and integrin subunits of alpha(v)beta3 was performed. Intergroup comparisons of the average values were conducted with a Mann-Whitney U-test for tooth movement and the number of tartrate-resistant acid phosphatase (TRAP), MMP-9, cathepsin K, and integrin subunits of alpha(v)beta3-positive cells. In the laser-irradiated group, the amount of tooth movement was significantly greater than that in the non-irradiated group at the end of the experiment (P < 0.05). Cells positively stained with TRAP, MMP-9, cathepsin K, and integrin subunits of alpha(v)beta3 were found to be significantly increased in the irradiated group on days 2-7 compared with those in the non-irradiated group (P < 0.05). These findings suggest that low-energy laser irradiation facilitates the velocity of tooth movement and MMP-9, cathepsin K, and integrin subunits of alpha(v)beta3 expression in rats.

Low-energy laser irradiation accelerates the velocity of tooth movement via stimulation of the alveolar bone remodeling

INTRODUCTION Previously, the authors have reported the acceleration of tooth movement and osteoclastogenesis on the pressure site in an experimental tooth movement model by low-energy laser irradiation (LELI), which stimulated the RANK/RANKL system and c-fms/macrophage colony-stimulating factor system. However, the effect of LELI on osteogenesis on the tension site is not known clearly. Moreover, the temporal changes in alveolar bone during tooth movement have not been investigated as yet. Therefore, the present study was designed to examine the effects of LELI on alveolar bone remodeling during experimental tooth movement, and observe the temporal bone mineral density (BMD) using micro-computed tomography (muCT). MATERIALS AND METHODS To induce experimental tooth movement in rats, 10 g force was applied to the upper right first molar with Nickel titanium closed-coil. Next, a gallium-aluminum-arsenide (Ga-Al-As) diode laser was used to irradiate the area around the moved tooth, and BMD and the amount of tooth movement were measured by muCT scanning for 21 days. Histopathological examination was also performed. RESULTS The amount of tooth movement in the LELI group was significantly greater than in the non-irradiation group by the end of the experimental period. Further, compared with the non-irradiation group, the fall of BMD was less in the LELI group. CONCLUSION These findings suggest that LELI accelerates the velocity of tooth movement via stimulation of the alveolar bone remodeling.

Expressions of RANKL/RANK and M-CSF/c-fms in root resorption lacunae in rat molar by heavy orthodontic force

The differentiation and functions of osteoclasts are regulated by receptor activator of nuclear factor-κB (RANK)/receptor activator of nuclear factor-κB ligand (RANKL) system that stimulates osteoclasts formation. Macrophage colony-stimulating factor (M-CSF) is also essential for osteoclastogenesis. A recent immunocytochemical study reported that RANKL/RANK and M-CSF/c-fms were localized in the periodontal ligament of rat molars during experimental orthodontic tooth movement. The present study focused on the expressions of RANKL/RANK and M-CSF/c-fms in root resorption area during experimental tooth movement in rats. Forty 6-week-old male Wistar rats were subjected to an orthodontic force of 10 or 50 g with a closed coil spring (wire size: 0.005 inch, diameter: 1/12 inch) ligated to the maxillary first molar cleat by a 0.008 inch stainless steel ligature wire to induce a mesial tipping movement of the upper first molars. Experimental tooth movement was undertaken for 10 days. Each sample was sliced into 6 μm continuous sections in a horizontal direction and prepared for haematoxylin and eosin (H and E) and immunohistochemistry staining for tartrate-resistant acid phosphatase (TRAP), RANK, RANKL M-CSF, and c-fms in root resorption area. Statistical analysis was carried out using a Mann-Whitney U-test with a significance level of P<0.01. On days 7 and 10, immunoreactivity for RANKL/RANK and M-CSF/c-fms was detected in odontoclasts with an orthodontic force of 50 g, but not 10 g. Therefore, RANKL/RANK and M-CSF/c-fms systems may be involved in the process of root resorption by heavy orthodontic force.

Substance P stimulates release of RANKL via COX-2 expression in human dental pulp cells.

Abstract.Objective: Our previous study found that substance P (SP), a sensory neuropeptide, was expressed in the dental pulp of rats during experimental tooth movement. We examined the effects of SP on the production of prostaglandin (PG) E2 and the receptor activator of nuclear factor- B ligand (RANKL) by human dental pulp fi broblast-like (HDPF) cells. Materials and methods: SP was added to cultured HDPF cells at concentrations ranging from of 10−4 to 10−12 mol/L. PGE2 and soluble RANKL (sRANKL) levels were determined using enzyme-linked immunosorbent assay kits. Gene expression was confi rmed by RT-PCR analysis. Pit formation assays using dentin slices were carried out to examine the effect of SP on osteoclastogenesis. Results: The levels of PGE2 and sRANKL increased in the presence of SP, though the increases were greater in the experimental groups in both a time- and concentration-dependent manner, and the increase of RANKL was partially mediated by PGE2 . The gene expression of cyclooxygenase (COX)-2 and RANKL was up-regulated, and conditioned medium samples obtained from HDPF cells treated with SP induced bone resorption. Conclusions: SP stimulated the production of PGE2 and RANKL, and promoted bone resorption. Therefore, SP may be involved in pulpal inflammation and root resorption during orthodontic tooth movement.