Primary stability of different implant macrodesigns in a sinus floor elevation simulated model: an ex vivo study.

BACKGROUND: A novel type of implant (Straumann® BLX implant) has been developed for certain stability from the mechanical and biological aspects and is expected for the implant placement in atrophic maxilla with sinus floor elevation (SFE). PURPOSE: The aim of this study was to evaluate the primary stability in the implants with different macrodesigns in an SFE simulated model. Primary stabilities defined as maximum insertion torque (MIT) and implant stability quotient (ISQ) were compared between this novel type of implant and other types. MATERIALS AND METHODS: Five types of Straumann® 10 mm length implants (Standard Plus; SP, Tapered Effect; TE, Bone Level; BL, Bone Level Tapered; BLT and BLX) and two types of Straumann® 6 mm length implants (SP short, BLX short) were used in this study. Each implant was inserted through 5 mm-thick porcine iliac crest blocks (an SFE simulated model). Primary stability was evaluated by using MIT and ISQ. RESULTS: The mean value of MIT for BLX group showed significantly higher values than SP, BL (p < 0.01), and TE (p < 0.05) groups. The mean value of ISQ for BLX group was significantly higher than the other groups (p < 0.01). The mean value of MIT and ISQ for BLX and BLX short group were significantly higher than those for SP and SP short group (p < 0.01). CONCLUSIONS: In an SFE simulated ex vivo model, BLX group showed the highest values. These results suggest that implant selection can play a crucial role in the achievement of primary stability during SFE and simultaneous implant placement.

A retrospective cross-sectional analysis of swallowing and tongue functions in maxillectomy patients.

PURPOSE: To investigate the profiles of swallowing and tongue functions, and to identify factors influencing swallowing in maxillectomy patients. METHODS: Maxillectomy patients whose swallowing function defined by Eating Assessment Tool (EAT-10) score and tongue functions (oral diadochokinesis: ODK, maximum tongue pressure: MTP) with or without obturator prostheses had been evaluated were enrolled in this study. The effects of the history of radiotherapy and soft palate defect on swallowing function were evaluated. The effect of radiotherapy on oral dryness was also evaluated. To examine correlations of swallowing function with continuous variables, Spearman correlation coefficients were calculated. RESULTS: A total of 47 maxillectomy patients (23 males and 24 females, median age: 71 [IQR: 63-76]) were registered. The median value of EAT-10 scores was 3 [IQR: 0-14]. Patients with the history of radiotherapy, but not with soft palate defect, showed significantly declined swallowing function. ODK and MTP of patients wearing obturator prostheses were significantly improved. No significant effect of radiotherapy on oral dryness was found. A significant correlation was found between EAT-10 score and MTP (P = 0.04). CONCLUSIONS: Swallowing function in maxillectomy patients was relatively impaired and the patients with the history of radiotherapy showed lower swallowing function. Obturator prostheses could contribute to the improvement of MTP and ODK (/ta/). MTP may play a crucial role in swallowing in maxillectomy patients.

IL-1ß Induces Pathologically Activated Osteoclasts Bearing Extremely High Levels of Resorbing Activity: A Possible Pathological Subpopulation of Osteoclasts, Accompanied by Suppressed Expression of Kindlin-3 and Talin-1.

As osteoclasts have the central roles in normal bone remodeling, it is ideal to regulate only the osteoclasts performing pathological bone destruction without affecting normal osteoclasts. Based on a hypothesis that pathological osteoclasts form under the pathological microenvironment of the bone tissues, we here set up optimum culture conditions to examine the entity of pathologically activated osteoclasts (PAOCs). Through searching various inflammatory cytokines and their combinations, we found the highest resorbing activity of osteoclasts when osteoclasts were formed in the presence of M-CSF, receptor activator of NF-κB ligand, and IL-1ß. We have postulated that these osteoclasts are PAOCs. Analysis using confocal laser microscopy revealed that PAOCs showed extremely high proton secretion detected by the acid-sensitive fluorescence probe Rh-PM and bone resorption activity compared with normal osteoclasts. PAOCs showed unique morphology bearing high thickness and high motility with motile cellular processes in comparison with normal osteoclasts. We further examined the expression of Kindlin-3 and Talin-1, essential molecules for activating integrin ß-chains. Although normal osteoclasts express high levels of Kindlin-3 and Talin-1, expression of these molecules was markedly suppressed in PAOCs, suggesting the abnormality in the adhesion property. When whole membrane surface of mature osteoclasts was biotinylated and analyzed, the IL-1ß-induced cell surface protein was detected. PAOCs could form a subpopulation of osteoclasts possibly different from normal osteoclasts. PAOC-specific molecules could be an ideal target for regulating pathological bone destruction.

The impact of surface alteration on epithelial tissue attachment after the mechanical cleaning of titanium or zirconia surface.

OBJECTIVE: Mechanical plaque removal may alter the surface morphology of the gingival penetration part of the implant. We applied an air-powered abrasive system (AP), titanium curette (TC), stainless curette (SC), ultrasound scaler (US), and titanium brush (TB) which are commonly used to remove plaque, to titanium or zirconia and the changes in surface morphology and the epithelial attach against substrata. MATERIALS AND METHODS: (a) The morphological changes of titanium and zirconia after mechanical cleaning were assessed by scanning electron microscopy and a roughness analyser. (b) Oral epithelial cells of rats were inoculated on the surface of the materials after mechanical cleaning, and the adherence of epithelial cells was observed. (c) The maxillary first molars were extracted from the rats and replaced by experimental titanium or zirconia implants. The length of the immunoreactive laminin-332 band was observed at the implant-peri-implant epithelium interface. RESULTS: (a) The surface roughness increased in experimental groups except the AP group. (b) Among the experimental groups, the AP group showed the highest number of attached cells. (c) The length of the immunoreactive laminin-332 band was longer in the control group than those in all five experimental groups. Among the experimental groups, the AP group showed the longest band. CONCLUSION: All mechanical cleaning methods increased the surface roughness of the materials except AP. AP did not cause distinct implant surface alterations. Surface alteration caused by mechanical cleaning may evoke inferior for epithelial attachment and reduce resistance against foreign infiltration.

Relationship between Maximum Tongue Pressure Value and Age, Occlusal Status, or Body Mass Index among the Community-Dwelling Elderly.

Background and objectives: In an aging society, the maintenance of the oral function of the elderly is of importance for the delay or prevention of frailty and long-term care. In the present study, we focused on the maximum tongue pressure (MTP) value and analyzed the relationship between MTP and age, occlusal status, or body mass index (BMI). Materials and Methods: This one-center observatory study was conducted using a cohort consisting of 205 community-dwelling outpatients over 65 years old. The MTP values of all subjects were measured using a commercially available tongue pressure measurement device and statistically analyzed. In addition, the correlation between MTP value and BMI was analyzed. Results: The MTP value decreased with age, especially in subjects classified as Eichner B and C. The difference in occlusal status did not show any statistically significant influence on MTP value. The correlation between BMI and MTP value was indicated in the tested groups other than an age of 65-74 and Eichner A groups. Conclusions: Although MTP value decreased with age, the difference in occlusal status did not have an impact on MTP value. The correlation between BMI and MTP value was not shown in the youngest group or a group with sufficient occlusal units. The results presented in the present study may imply that, even if MTP is low, younger age and/or better occlusal status compensate for the inferior MTP value in the cohort studied.

Maxillary Sinus Floor Augmentation Using Low-Crystalline Carbonate Apatite Granules With Simultaneous Implant Installation: First-in-Human Clinical Trial.

PURPOSE: Carbonate apatite (CO3Ap), an inorganic component of human bone, can be fabricated in chemically pure form from calcium carbonate block via a dissolution-precipitation reaction. A first-in-human clinical trial was conducted in which low-crystalline CO3Ap granules were evaluated for safety and efficacy in sinus floor augmentation and simultaneous implant installation. MATERIALS AND METHODS: Procedures were performed in 8 patients (9 implants) with 2 granule sizes: small (300 to 600 µm) and medium (600 to 1,000 µm). Panoramic radiographic assessment was performed immediately after augmentation, 7 ± 2 months after augmentation, 6 ± 2 months after prosthetic loading, and 12 ± 2 months after prosthetic loading. RESULTS: Postoperative healing was uniformly uneventful, with no abnormal bleeding, pain, or swelling, and all implants achieved successful osseointegration. The mean residual maxillary molar bone height was 5.2 ± 0.8 mm preoperatively and increased to 14.0 ± 1.9 mm after augmentation. Implants 9.0 to 11.5 mm in length were placed. The post-augmentation height decreased to 12.4 ± 1.3 mm at 7 ± 2 months; after prosthetic loading, it decreased to 11.9 ± 0.8 mm at 6 ± 2 months and 11.7 ± 0.6 mm at 12 ± 2 months. No abnormal bone resorption of the augmented areas was observed, and bone height supporting the implants was maintained. The overall implant survival rate was 100%, with no implant failures or complications during the first year. CONCLUSIONS: Low-crystalline CO3Ap granules were useful and safe for sinus floor augmentation and simultaneous implant installation, providing a promising bone substitute for dental implant surgery.

Generation and histomorphometric evaluation of a novel fluvastatin-containing poly(lactic-co-glycolic acid) membrane for guided bone regeneration.

The purpose of this study was to evaluate the effects of a poly(lactic-co-glycolic acid) (PLGA) membrane containing fluvastatin on bone regeneration at bone defects in rat calvaria and tibia for possible use as a guided bone regeneration (GBR) membrane. PLGA and fluvastatin-containing PLGA (PLGA-fluvastatin) membranes were prepared and mechanical properties were evaluated. Standardized bony defects were created in rat calvaria and the right tibia, and covered with a PLGA or PLGA-fluvastatin membrane. Bone regeneration was evaluated using image analysis based on histologic examination. At 4 and 8 weeks after membrane implantation, the PLGA-fluvastatin group displayed enhanced new bone formation around the edge of the defect compared with the PLGA membrane group in the calvarial model. Thick bone regeneration was observed in tibia-defect sites in the PLGA-fluvastatin membrane group. These results suggest that the PLGA-containing fluvastatin membrane prepared in this study may potentially be used as a GBR membrane.

A peptide that blocks the interaction of NF-κB p65 subunit with Smad4 enhances BMP2-induced osteogenesis.

Bone morphogenetic protein (BMP) potentiates bone formation through the Smad signaling pathway in vitro and in vivo. The transcription factor nuclear factor κB (NF-κB) suppresses BMP-induced osteoblast differentiation. Recently, we identified that the transactivation (TA) 2 domain of p65, a main subunit of NF-κB, interacts with the mad homology (MH) 1 domain of Smad4 to inhibit BMP signaling. Therefore, we further attempted to identify the interacting regions of these two molecules at the amino acid level. We identified a region that we term the Smad4-binding domain (SBD), an amino-terminal region of TA2 that associates with the MH1 domain of Smad4. Cell-permeable SBD peptide blocked the association of p65 with Smad4 and enhanced BMP2-induced osteoblast differentiation and mineralization without affecting the phosphorylation of Smad1/5 or the activation of NF-κB signaling. SBD peptide enhanced the binding of the BMP2-inudced phosphorylated Smad1/5 on the promoter region of inhibitor of DNA binding 1 (Id-1) compared with control peptide. Although SBD peptide did not affect BMP2-induced chondrogenesis during ectopic bone formation, the peptide enhanced BMP2-induced ectopic bone formation in subcortical bone. Thus, the SBD peptide is useful for enabling BMP2-induced bone regeneration without inhibiting NF-κB activity.

A stepwise under-prepared osteotomy technique improves primary stability in shallow-placed implants: a preliminary study for simultaneous vertical ridge augmentation.

Simultaneous vertical ridge augmentation (VRA) can reduce treatment procedures and surgery time, but the concomitant reduction in primary stability (PS) of a shallow-placed implant imparts risk to its prognosis. Although several studies have reported improvements in PS, there is little information from any simultaneous VRA model. This study aimed to evaluate whether tapered implants with stepwise under-prepared osteotomy could improve the PS of shallow-placed implants in an in vitro model of simultaneous VRA. Tapered implants (Straumann® Bone Level Tapered implant; BLT) and hybrid implants (Straumann® Bone Level implant; BL) were investigated in this study. A total of 80 osteotomies of different depths (4, 6, 8, 10 mm) were created in rigid polyurethane foam blocks, and each BLT and BL was inserted by either standard (BLT-S, BL-S) or a stepwise under-prepared (BLT-U, BL-U) osteotomy protocol. The PS was evaluated by measuring maximum insertion torque (IT), implant stability quotient (ISQ), and removal torque (RT). The significance level was set at P < 0.05. There were no significant differences in IT, ISQ or RT when comparing BLT-S and BL-S or BLT-U and BL-U at placement depths of 6 and 8 mm. When comparison was made between osteotomy protocols, IT was significantly greater in BLT-U than in BLT-S at all placement depths. A stepwise under-prepared osteotomy protocol improves initial stability of a tapered implant even in a shallow-placed implant model. BLT-U could be a useful protocol for simultaneous VRA.

Histopathological comparison of the onset of peri-implantitis and periodontitis in rats.

BACKGROUND AND OBJECTIVE: There are a few experimental models that clearly describe the pathological differences in tissue destruction between periodontitis and peri-implantitis. We recently reported that the formation of immune complexes accelerates site-specific loss of attachment and alveolar bone resorption when an antigen is topically applied in the gingival sulcus of an immunized rat. We applied this model to the peri-implant tissues and compared peri-implant destruction to periodontitis without using a ligature. MATERIAL AND METHODS: Twenty-five rats were used in this study and were divided into five groups. Implantation was performed immediately after extraction of right first molars in rats. The left first molars were left untreated to be examined as natural teeth. The immunized group consisted of rats that had received intraperitoneal lipopolysaccharide (LPS), whereas the nonimmunized group received only phosphate-buffered saline (PBS). The untreated baseline group received only implantation. After intraperitoneal booster injection, half of each group received topical application of LPS in the palatal gingival sulcus daily for 3 days. The other half of the groups received PBS. Histopathological and histometrical findings were observed with hematoxylin and eosin staining, collagen fibers were observed with Azan staining, and formation of immune complexes was immunohistologically evaluated by C1qB expression. RESULT: Peri-implant tissue destruction was greater in the immunized and LPS-applied groups than in the other groups. No periodontal destruction was observed. Formation of immune complexes was observed in the junctional epithelium and adjacent connective tissue in the immunized groups. CONCLUSION: Antigen-induced peri-implant tissue destruction occurs faster than periodontal tissue destruction.

Micro-computed tomography analysis of early stage bone healing using micro-porous titanium mesh for guided bone regeneration: preliminary experiment in a canine model.

The aim of this study was to evaluate the amount of bone formation beneath a defect area after treatment with titanium mesh membranes with different thicknesses and pore sizes alone or in combination with bone graft to induce bone formation during the early stage of healing time. The mandibular premolars were extracted bilaterally from three adult beagle dogs, and 8-mm-diameter bone defects were created on the buccal site of the premolar regions. Hydroxyapatite bone graft substitute was applied in the defect site unilaterally, and other site was left empty. Then, a novel micro-porous mesh (50 µm in pore diameter) or commercially available macro-porous titanium mesh (1700 µm in pore diameter) was placed on the defect and secured with screws. After 4 weeks, the mandibles were harvested, imaged using micro-computed tomography, and prepared for histological and morphometric evaluation. Higher new bone volumes (mm3), percentage of new bone volumes in the total defect volumes (bone ratio: %), and new bone area (mm2) through morphometric evaluation were found on the novel membranes with 50-µm-diameter pores compared to the commercial titanium mesh. Moreover, experiment sites without bone graft were observed with higher new bone volume and bone ratio compared with sites with bone graft. However, bone mineral density of novel mesh was observed to be lower compared with other experimental sites. Under the experimental condition, the result of this study suggests that titanium meshes with 50-µm-diameter pores were effective for guided bone regeneration in the early stage of healing.

RhoA-Mediated Functions in C3H10T1/2 Osteoprogenitors Are Substrate Topography Dependent.

Surface topography broadly influences cellular responses. Adherent cell activities are regulated, in part, by RhoA, a member of the Rho-family of GTPases. In this study, we evaluated the influence of surface topography on RhoA activity and associated cellular functions. The murine mesenchymal stem cell line C3H10T1/2 cells (osteoprogenitor cells) were cultured on titanium substrates with smooth topography (S), microtopography (M), and nanotopography (N) to evaluate the effect of surface topography on RhoA-mediated functions (cell spreading, adhesion, migration, and osteogenic differentiation). The influence of RhoA activity in the context of surface topography was also elucidated using RhoA pharmacologic inhibitor. Following adhesion, M and N adherent cells developed multiple projections, while S adherent cells had flattened and widespread morphology. RhoA inhibitor induced remarkable longer and thinner cytoplasmic projections on all surfaces. Cell adhesion and osteogenic differentiation was topography dependent with S < M and N surfaces. RhoA inhibition increased adhesion on S and M surfaces, but not N surfaces. Cell migration in a wound healing assay was greater on S versus M versus N surfaces and RhoA inhibitor increased S adherent cell migration, but not N adherent cell migration. RhoA inhibitor enhanced osteogenic differentiation in S adherent cells, but not M or N adherent cells. RhoA activity was surface topography roughness dependent (S < M, N). RhoA activity and -mediated functions are influenced by surface topography. Smooth surface adherent cells appear highly sensitive to RhoA function, while nano-scale topography adherent cell may utilize alternative cellular signaling pathway(s) to influence adherent cellular functions regardless of RhoA activity.

Tissue Reaction to a Novel Bone Substitute Material Fabricated With Biodegradable Polymer-Calcium Phosphate Nanoparticle Composite.

PURPOSE: The aim of this study was to evaluate the effectiveness of a novel bone substitute material fabricated using a biodegradable polymer-calcium phosphate nanoparticle composite. METHODS: Porous structured poly-L-lactic acid (PLLA) and hydroxyapatite (HA) nanoparticle composite, which was fabricated using solid-liquid phase separation and freeze-drying methods, was grafted into bone defects created in rat calvarium or tibia. Rats were killed 4 weeks after surgery, and histological analyses were performed to evaluate new bone formation. RESULTS: Scanning electron microscopic observation showed the interconnecting pores within the material and the pore diameter was approximately 100 to 300 µm. HA nanoparticles were observed to be embedded into the PLLA beams. In the calvarial implantation model, abundant blood vessels and fibroblastic cells were observed penetrating into pores, and in the tibia model, newly formed bone was present around and within the composite. CONCLUSIONS: The PLLA-HA nanoparticle composite bone substitute developed in this study showed biocompatibility, elasticity, and operability and thus has potential as a novel bone substitute.

Technique for identifying keratinized gingival tissue and soft tissue morphology on 3-dimensional implant-planning software images.

Preoperative 3-dimensional (3D) planning using cone beam computed tomography (CBCT) and 3D implant-planning software is used routinely for implant placement. However, despite its importance in planning surgical technique (conventional or flapless surgery) and prognosis, the distribution of keratinized gingival tissues (KGT) and soft tissue morphology cannot be identified with CBCT or planning software images. This report introduces a technique for identifying the distribution of KGT and soft tissue morphology during preoperative 3D planning.

Facial bone alterations on maxillary anterior single implants for immediate placement and provisionalization following tooth extraction: a superimposed cone beam computed tomography study.

OBJECTIVES: The purpose of this cone beam computed tomography (CBCT) study was to describe the facial bone changes around single implants for immediate placement and provisionalization following tooth extraction in the maxillary anterior. MATERIAL AND METHODS: The data between 2008 and 2013 were collected retrospectively. Superimposed facio-palatal cross-sectional CBCT images for the implants were derived from preoperative and postoperative radiographs via standardized CBCT processes. Horizontal and vertical facial measurements on the implants were identified at preoperative and approximately 1-year postoperative follow-ups. Correlation coefficient for those parameters was evaluated. RESULTS: A total of 12 single implants in 12 patients were included in this study. The mean loading period was 13.3 months (range 12-15 months). The median data of preoperative bone thickness 0.54 mm (A), preoperative vertical bone level 1.46 mm (B), postoperative bone thickness 1.77 mm (C), postoperative vertical bone level 1.08 mm (D), horizontal distance from outer surface of preoperative facial bone to implant surface 2.08 mm (E), horizontal gap distance 1.41 mm (E-A), horizontal bone resorption -0.26 mm (E-C), and vertical bone resorption -0.25 mm (B-D) were obtained. The data at the implant platform level (IPL) were selected for the horizontal measurements. Spearman's analysis demonstrated statistically significant correlations between B and D, C and E, E and E-A, and B and E-C (P < 0.01). Significant correlations between C and B, D, and E-A were also found, respectively (P < 0.05). CONCLUSIONS: Immediate placement and provisionalization of single implants procedure in the maxillary anterior showed excellent outcomes with the small facial bone alterations around the implants. Neither preoperative facial bone thickness nor horizontal gap distance influenced the amount of facial bone resorptions.

Fibroblast attachment onto novel titanium mesh membranes for guided bone regeneration.

Titanium mesh is used in orthopedic surgery as a barrier membrane, as it offers suitable characteristics, which allow mechanical support during the formation of new bone. An ideal membrane would facilitate cell attachment onto its surface, thereby helping to stabilize the blood clot and integrate the membrane into the tissue. However, currently available titanium mesh has millimeter-level pore sizes, which lead to soft tissue ingrowth through the pores. Therefore, the aim of this study was to investigate the fibroblast attachment and migration on different designs of novel titanium mesh with micrometer pore size for guided bone regeneration treatment. Six types of novel titanium mesh membrane and three groups of commercially available membranes were used in this study. Fibroblasts were isolated from 4-day-old green fluorescence protein rats and seeded onto membrane surfaces. At 24 h, the cells attached to the membrane surfaces were fixed and stained with DAPI. The blue-stained nuclei on membrane surfaces, and both upper and lower sides were counted. It was shown that different membrane materials, structure and design differ considerably in their capacity for cell attachment to the membrane surface. The novel membranes, especially mesh with 12 pores compared with mesh with multi-pores, allowed the fibroblast attachment on the membrane surface, but hindered the fibroblast migration through the pores into the lower side of the membrane, which is associated with the defect area in the clinical condition.

Additional Effects of Platelet-Rich Fibrin on Bone Regeneration in Sinus Augmentation With Deproteinized Bovine Bone Mineral: Preliminary Results.

PURPOSE: Platelet-rich fibrin (PRF) has been reported to contribute to bone regeneration; however, little is known about details with deproteinized bovine bone mineral (DBBM). This study aims to evaluate additional effects of PRF on bone regeneration in sinus augmentation with DBBM. MATERIALS AND METHODS: Sinus augmentations were made with DBBM/PRF mixture as lateral approach for 4 sinuses from 4 patients. Bone biopsies were obtained from posterior maxilla at the implant placements 7 or 10 months after sinus augmentations. Histological observations and histomorphometric analyses from augmented areas were performed. RESULTS: The new bone formation was found around the DBBMs with very good contact while surfaces of DBBMs were partly resorbed. Osteoclasts recognized the DBBMs for remodeling, followed by new bone running. The histomorphometric analyses revealed that mean percentages of newly formed bone were 31.7 ± 1.2%, 21.0 ± 1.0%, 38.0 ± 0.6%, and 47.0 ± 0.6%, respectively (mean 34.5 ± 5.7%). CONCLUSIONS: Additional effects of PRF could be found because of higher percentages of newly bone formation by DBBM/PRF mixture than those by DBBM individual in previous reports.

Mesenchymal stem cells markedly suppress inflammatory bone destruction in rats with adjuvant-induced arthritis.

Mesenchymal stem cells (MSCs) have potential to differentiate into multiple cell lineages. Recently, it was shown that MSCs also have anti-inflammatory and immunomodulatory functions. In this report, we investigated the regulatory function of MSCs in the development of inflammatory bone destruction in rats with adjuvant-induced arthritis (AA rats). MSCs were isolated from rat bone marrow tissues, expanded in the presence of basic FGF, and intraperitoneally injected into AA rats. MSC administration significantly suppressed inflammatory parameters: swelling score, swelling width, and thickness of hind paw. Radiographic evaluation indicated that MSC significantly suppressed bone destruction. Histological analysis showed that administration of MSCs markedly suppressed osteoclastogenesis in AA rats. To further delineate their effects on osteoclastogenesis, MSCs were added to in vitro bone marrow cultures undergoing osteoclastogenesis. MSCs significantly suppressed osteoclastogenesis in this system. Chemokine receptor expression in MSCs was assessed by RT-PCR, and a chemotactic assay was performed using a transwell culture system. MSCs showed significant chemotaxis to MIP-1α (CCL3) and SDF-1α (CXCL12), chemokines preferentially expressed in the area of inflammatory bone destruction. Furthermore, MSCs expressed IL-10 and osteoprotegerin, cytokines that suppress osteoclastogenesis. These data suggest that recruitment of MSC to the area of bone destruction in AA rats could suppress inflammatory bone destruction and raise the possibility that MSCs may have potential for the treatment of inflammatory bone destruction in arthritis.

Comparison of attitudes towards dental education among dental students in Japan and China.

The aim of this study was to identify and compare the attitudes of dental students towards dental education in Japan and China. Fifty-four dental students from the Stomatology School of China Medical University and 51 dental students from the Dental Faculty of Kyushu University, Japan, participated in this study. Information was derived from a self-answered questionnaire consisting of 11 items. Significant differences in the responses of the participants from the two countries were detected for 10 of the questionnaire items (P < 0.05). Nearly three-quarters of the Japanese students were satisfied with the teaching faculties of their schools, while only a quarter of the Chinese students indicated satisfaction. A total of 69% of Chinese students thought that learning a foreign language wasted too much time compared with none of the Japanese students. A student-oriented teaching mode was not well accepted by either of the groups, and 62% of Chinese students and 53% of Japanese students wanted to increase the duration of the clinical practice stage of education. The findings from this study enhance our understanding of differences and/or similarities among dental students in the two nations. This information may help to define strategies to improve the quality of dental education, and especially exchange programmes of international students.

Career choice and future design of dental students in China and Japan.

The purpose of this study was to compare career choice and future plans of dental students in China and Japan. Information was derived from a self-answered questionnaire. Significant differences were detected for eight items between the two countries. Regarding motivation towards career choice, 41% of Japanese students indicated positive motives related to helping others, achieving self-worth and health-care related interests, whereas Chinese students indicated that their choice was mainly for financial and prestige reasons, and for 32% of them, dentistry was a passive choice. More Chinese dental students (74%) wanted further education compared with Japanese students (22%). The majority of Japanese students (56.9%) planned to work as general dentists. Conversely, Chinese students were more likely to specialise (50%). More than 50% of Japanese students wanted to work in dental offices, but the majority of Chinese students (65%) preferred university hospital. We found it is strange that nearly one-fourth of the Chinese students did not want to be a clinical dentist mainly because of the poor health-care environment. This study provides a description of the perspectives of Japanese and Chinese dental students and enables a better understanding of career choices and future course design issues.