Language：English   Publisher：(公社)日本補綴歯科学会  

インプラント部位へドリルプレパレーション処置を行う場合、特に同部位の骨密度が低い症例では、プレパレーション寸法を小さめにとることがある(underpreparation;アンダー処置)。こうしたドリルプレパレーションのアンダー処置と通常の処置の違いが臨床成功率に及ぼす影響を、骨密度の点で区別しつつ調査する系統的レビューとメタアナリシスを施行した。3種のデータベースの全登録文献を対象に関連キーワードでの検索を行った。適格とする研究は、少なくとも症例10名の転帰を評価していたランダム化または非ランダム化での臨床試験、および後方視的コホート研究とした。最終的に14報をメタ回帰分析に組み入れた。算出された骨吸収量は、ドリルプレパレーションの通常処置群では平均-0.43±0.28mm、アンダー処置群では平均-0.80±0.37mmとなった。骨密度が高い群から低い群まで4群に分けてインプラント周囲骨レベル(MBL)を比較した本メタ回帰分析から、MBLはドリルプレパレーションの種類および骨密度によって影響されることが示された。特に骨密度が最も高い群では、アンダー処置群よりも通常処置群の方がMBLは低くなっていた。骨密度が最も低い群を除いた3群においては、骨削除部位に対しインプラントがより大きくミスマッチであることがMBL上昇と正に関連していた。

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Prosthodontic Society  

<p><b>Purpose:</b> There is no clinical consensus to determine the right balance between underpreparation and marginal bone level changes. The purpose of this systematic review and meta-regression was to investigate the influence of the type of drilling preparation of the implant site in relation to the bone mineral density on the clinical success, expressed in terms of the MBL and implant failure rate.</p><p><b>Study Selection:</b> A thorough search was performed using the digital databases MEDLINE PubMed, EMBASE, and Cochrane Central Register of Controlled Trials by entering research lines or various combinations of free words. The main keywords used were “dental implants”, “bone density”, and “torque”.</p><p><b>Results:</b> The mean bone resorption in the conventional preparation group was -0.43 (± 0.28) mm, whereas it was -0.80 (± 0.37) mm in the underprepared group. For the D1/D2/D3 bone group, the slope was significantly different from zero and linearity; the D4 bone group slope was not significantly different from zero and was almost parallel, although it was significantly different from linearity. The box and whiskers plot shows that the MBL in underprepared sites tended to be significantly higher with a higher variation than that in conventionally prepared sites.</p><p><b>Conclusions:</b> Within its limits, our meta-regression analysis showed that MBL is influenced by the type of drilling preparation and bone mineral density. In particular, a lower MBL was observed in the D1 bone with conventional preparation than with underpreparation. Moreover, a greater implant-to-osteotomy site mismatch was positively associated with greater MBLs in the bone densities of D1/D2/D3.</p>

DOI： 10.2186/jpr.jpr_d_21_00275

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Materials  

Bone augmentation using artificial bone is an important option in dental defect prostheses. A bone substitute using carbonate apatite (CO3Ap), an inorganic component of bone, was reported to have promising bone formation and bone replacement ability. However, the osteoinductivity of artificial bone is less than autogenous bone (AB). In this study, CO3Ap with AB is demonstrated as a clinically effective bone substitute. For in vitro experiments, an osteoclast-like cell (RAW-D) was cultured in the presence of AB, CO3Ap, or both (Mix), and the number of osteoclasts was evaluated. Osteoblasts were also cultured under the same conditions, and the number of adherent cells was evaluated. For in vivo experiments, a few holes were created in the rat tibia and AB, CO3Ap, or Mix were added. At 0, 14, and 21 days, the tissue morphology of the wound area was observed, and the thickness of the cortical bone was measured. In vitro, Mix did not increase the number of osteoclasts or osteoblasts. However, in vivo, the rate of bone replacement remarkably increased with Mix on dome-shape. A bone-grafting material combining osteoinductive AB with abundant artificial bone is expected to be clinically easy to use and able to form bone.

DOI： 10.3390/ma15228100

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Language：English   Publishing type：Research paper (scientific journal)  

Currently, along with titanium (Ti), zirconia is widely used as an abutment material for dental implants because it makes it possible to avoid gingival discoloration; however, the epithelial sealing capability of zirconia remains unknown. The purpose of the present study is to elucidate the localization of integrin β4 subunit (Inβ4), one of the main proteins in the attachment structure between gingival junctional epithelial (JE) cells and substrata. Maxillary first molars were extracted from rats, and implants were placed with Ti or zirconia transgingival parts; then, the localization of Inβ4 was observed. Morphological and functional changes in rat oral epithelial cells (OECs) cultured on a culture dish (Dish) and Ti and zirconia plates were also evaluated with Inβ4 immunofluorescence histochemistry and Western blotting. After four weeks of implant placement, the morphology of the peri-implant epithelium (PIE) and the localization of Inβ4 around the Ti and zirconia transgingival parts were similar. However, both exhibited markedly shorter Inβ4-positive bands in the PIE than in the JE around natural teeth. Decreased expression levels of Inβ4 were observed in OECs cultured on Ti and zirconia plates compared with those cultured on Dish. In conclusion, although inferior to natural teeth, zirconia implants are thought to have epithelial sealing properties comparable to those of titanium.

DOI： 10.3390/jcm9103331

Language：English   Publishing type：Research paper (scientific journal)  

This study aimed to evaluate the effect of surface hydrophilicity on the biomechanical aspects of osseointegration of dental implants in the tibia and femur of rabbits. Forty-eight mature female New Zealand White rabbits were included, and 96 commercially pure, Grade 4, titanium dental implants (control group), and 96 implants of same macro geometry with the hydrophilic surface (test group) were used in this study. One osteotomy was performed in each tibia and femur on both sides of the rabbit, and four implants were placed in each rabbit. Control and test groups were randomly allocated on the left and right sides. During surgery, insertion torque (ITQ) value of the complete implant placement was recorded. After healing periods of 0, 2, 4, and 8 weeks after surgery, Implant Stability Quotient (ISQ) value, and removal torque (RTQ) values were measured. No statistical difference was observed for ITQ, for ISQ and for RTQ between the control group and test group in tibia/femur for all time periods. The effect of hydrophilic properties on moderately roughened surfaces has no impact in terms of biomechanical outcomes (ISQ values and RTQ values) after a healing period of 2 to 8 weeks in rabbit tibias /femurs.

DOI： 10.1563/aaid-joi-d-19-00217

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

PURPOSE: The aim of this multi-scale in silico study was to evaluate the influence of resorption cavities on the mechanical properties and load distribution in cortical bone after implant placement with two different drilling protocols. MATERIAL AND METHODS: Two different micro-scale bone structures were assessed: cortical bone models with cavities (test) and without cavities (control) were designed from μCT data. In a macro-scale model, representing a mandibular ridge, oblique load of 150 N was applied on the implant-abutment. Maximum principal stress/strain, and shear stress/strain were calculated in the macro- and micro-scale models. RESULTS: Test presented anisotropic material properties. In tests, significantly greater maximum values of Maximum principal stress/strain were calculated in micro-scale model. These values were located at the implant neck area in the macro-scale model and in the proximity of cavities in the micro-scale model respectively. Greater values of shear stress/strain were found in the test along the mandibular horizontal plane. CONCLUSIONS: Cortical bone with resorption cavities following undersized drilling showed an impaired load distribution compared with bone without cavities. Subsequently, stress/strain distribution suggests that this bone model is more prone to microdamage, thus delaying the healing process.

DOI： 10.1016/j.jmbbm.2019.103598

Language：English   Publishing type：Research paper (scientific journal)  

Our aim was to investigate the possible impact of contamination with saliva on osseointegration during placement of implants with simultaneous bone augmentation. Six hemispheric shape bone defects (8mm in diameter×4mm deep) were prepared in each iliac bone of six sheep. A dental implant (2.9mm in diameter×10mm long) was placed in the centre of each defect, and then pairs of defects were filled with one of the following bone augmentation materials: autogenous bone, autogenous bone plus bovine bone, or resorbable biphasic ceramic bone substitute. One site in each augmentation group was impregnated with saliva (contaminated group), while the other was not (non-contaminated group). Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) within implant threads were measured after a healing period of five weeks, both in respect of the implant inserted in the augmented bone and in that inserted in the residual bone. Overall results showed that there was a significant difference between the contaminated and non-contaminated group for BIC in the augmented implant (p=0.028), while there were no significant differences in the implant in residual bone (p=0.722). For BAFO, there were no significant differences between the contaminated and non-contaminated groups among the different augmentation materials. The results showed that contamination with saliva during placement of an implant with simultaneous bone augmentation had a serious deleterious effect on osseointegration of the aspect of the implant within the augmented defect. Contamination with saliva during placement of an implant with simultaneous bone augmentation should therefore be avoided.

DOI： 10.1016/j.bjoms.2019.10.302

Language：English   Publishing type：Research paper (scientific journal)  

We previously reported that CaCl2 hydrothermal-treated (Ca-HT) titanium (Ti) implants induced a tight sealing at the interface between the implant and peri-implant epithelium (PIE) after implantation. However, it is not clear how long this improved epithelium sealing can be maintained. We subsequently investigated whether the positive effect of Ca-HT to promote sealing between the PIE and implant was sustained longer term. Maxillary molars were extracted from rats and replaced with either Ca-HT implants (Ca-HT group), distilled water-HT implants (DW-HT group) or non-treated implants (control group). After 16 weeks, the majority of implants in the Ca-HT group remained at the maxillary with no apical extension of the PIE. Conversely, half the number of control implants was lost following down-growth of the PIE. The effect of Ca-HT on migration and proliferation of rat oral epithelial cells (OECs) was also investigated. In OECs cultured on Ca-HT Ti plates, protein expression in relation to cell migration decreased, and proliferation was higher than other groups. Surface analysis indicated HT enhanced the formation of surface TiO2 layer without altering surface topography. Consequently, Ca-HT of Ti reduced PIE down-growth via tight epithelial attachment to the surface, which may enhance implant capability for a longer time post-implantation.

DOI： 10.3390/jcm8101560

Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: The intraosseous temperature during implant installation has never been evaluated in an in vivo controlled setup. The aims were to investigate the influence of a drilling protocol and implant surface on the intraosseous temperature during implant installation, to evaluate the influence of temperature increase on osseointegration and to calculate the heat distribution in cortical bone. METHODS: Forty Brånemark implants were installed into the metatarsal bone of Finnish Dorset crossbred sheep according to two different drilling protocols (undersized/non-undersized) and two surfaces (moderately rough/turned). The intraosseous temperature was recorded, and Finite Element Model (FEM) was generated to understand the thermal behavior. Non-decalcified histology was carried out after five weeks of healing. The following osseointegration parameters were calculated: Bone-to-implant contact (BIC), Bone Area Fraction Occupancy (BAFO), and Bone Area Fraction Occupancy up to 1.5 mm (BA1.5). A multiple regression model was used to identify the influencing variables on the histomorphometric parameters. RESULTS: The temperature was affected by the drilling protocol, while no influence was demonstrated by the implant surface. BIC was positively influenced by the undersized drilling protocol and rough surface, BAFO was negatively influenced by the temperature rise, and BA1.5 was negatively influenced by the undersized drilling protocol. FEM showed that the temperature at the implant interface might exceed the limit for bone necrosis. CONCLUSION: The intraosseous temperature is greatly increased by an undersized drilling protocol but not from the implant surface. The temperature increase negatively affects the bone healing in the proximity of the implant. The undersized drilling protocol for Brånemark implant systems increases the amount of bone at the interface, but it negatively impacts the bone far from the implant.

DOI： 10.3390/jcm8081198

Language：English   Publishing type：Research paper (scientific journal)  

© 2019 by Quintessence Publishing Co Inc. This study investigated the level of magnetic energy around implants possessing a static magnetic field (SMF) and assessed the in vivo influence of SMF on bone regeneration. Implants possessing a sintered neodymium magnet internally were placed in a rabbit femur. An implant without SMF was placed as control. After 12 weeks of healing in vivo, the bone samples were subjected to histologic/histomorphometric evaluation. The bone-toimplant contact for the test group and the control group were 32.4 ± 13.6&#37; and 17.1 ± 4.5&#37;, respectively, and the differences were statistically significant (P < .05). The results suggested that the SMF promoted new bone apposition.

DOI： 10.11607/prd.3220

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© 2019 by Quintessence Publishing Co Inc. Purpose: To evaluate the effect of misfit at implant-level fixed partial dentures (ILFPDs) and marginal bone support on the generation of implant cracks. Materials and Methods: This in vitro study included a mechanical fatigue test and finite element analysis. A mechanical cycling loading test was performed using 16 experimental models, each consisting of two parallel implants subdivided into four groups based on the misfit and the supporting bone condition. The framework, firmly seated at implants, was dynamically loaded vertically with a force of 1,600/160 N and 15 Hz for 1 × 10 6 cycles. Optical microscope, scanning electron microscope (SEM), and computed tomography three-dimensional (CT-3D) analyses were performed to detect impairments. Finite element models, representing the setups in the mechanical fatigue test, were used to represent the fatigue life. Results: None of the mechanical components presented distortion or fracture at the macroscopic level during the test. In a microscopy evaluation, the fatigue test revealed scratches visible in the inner part of the conical portion of the implants regardless of the groups. SEM and CT-3D analysis revealed one implant from the misfit/no bone loss group with a microfracture in the inner part of the conical interface. The simulated effective stress levels in the coronal body were higher in the misfit groups compared with the no misfit groups. The misfit groups presented effective stress levels, above 375 MPa, that penetrated the entire wall thickness. The no bone loss group presented an effective stress level above 375 MPa along its axial direction. In the no misfit group, the area presenting effective stress levels above 375 MPa in the conical connection was larger for the bone loss group compared with the no bone loss group. Conclusion: This study confirmed that implant fracture is an unlikely adverse event. A clear pattern of effective distribution greater than fatigue limit stresses could be noticed when the misfit was present. The dynamic load simulation demonstrated that the crack is more likely to occur when implants are fully supported by marginal bone compared with a bone loss scenario. Within the limitations of this study, it is speculated that marginal bone loss might follow the appearance of an undetected crack. Further research is needed to develop safe clinical protocols with regard to ILFPD.

DOI： 10.11607/jomi.6965

Language：English   Publishing type：Research paper (scientific journal)  

Our aim was to try and find out whether contamination with saliva during insertion of dental implants affects osseointegration in bone that has been augmented with different grafts. Six bony defects were created in each of the calvaria of six sheep, and then augmented with three different materials (autogenous bone, bovine bone, and resorbable biphasic ceramic bone substitute) After five weeks of healing, three implants contaminated with saliva (contaminated group) and three not contaminated (uncontaminated group) were placed in the centre of the augmented areas. For histomorphometric analysis, bone implant contact, bone area fraction occupancy, bone and material area, and bony area were measured after a healing period of five weeks. There was a significant difference between the contaminated and uncontaminated groups (p=0.036) for bone implant contact only in the augmented areas, but there were no significant differences in bone area fraction occupancy, bone and material area, and bony area. We conclude that contamination with saliva during placement of dental implants can significantly compromise bone implant contact in augmented areas, but had no significant effect on the formation of bone in areas more distant from the surface of the implant. We suggest that salivary contamination should be avoided during placement of dental implants in augmented areas.

DOI： 10.1016/j.bjoms.2018.11.014

Language：English   Publishing type：Research paper (scientific journal)  

This study evaluated the sustained release effect of clarithromycin-loaded in PLGA microspheres in a rabbit calvaria defect model. Four bone defects (ø5.0) were created in the calvaria of New Zealand White rabbits (n = 21, n = 7/time point). The defects were randomly designated to four groups. Group 1: No augmentation (sham), Group 2: beta-tricalcium phosphate (β-TCP), Group 3: β-TCP with 0.12 µg clarithromycin, and Group 4: β-TCP with 6.12 µg PLGA microspheres loaded with 0.12 µg Clarithromycin. After 2, 4, and 12 weeks of healing, bone regeneration was evaluated using micro-computed tomography (µCT) and histology. Clarithromycin release from PLGA microspheres revealed sustained release for around 4 weeks with ∼50&#37; release during the first week. Histologically, new bone formation was evident at 2 and 4 weeks of healing in all groups and bone formation increased as a function of healing time. At 12 weeks, Group 4 showed significantly higher amount of newly formed bone compared to Group 1. The µCT showed that Group 4 expressed significantly higher bone formation compared to Group 1 at all time points. The in vivo findings showed that β-TCP with clarithromycin-loaded microspheres can enhance bone formation in bone defects. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 201-208, 2018.

DOI： 10.1002/jbm.b.33844

Language：English   Publishing type：Research paper (scientific journal)  

OBJECTIVE: The aim of this study was to investigate the extent of cortical bone remodeling between two different drilling protocols by means of histomorphometric, µ-CT, and biomechanical analyses. MATERIAL AND METHODS: A total of 48 implants were inserted into the mandible of six sheep following two drilling protocols: Group A (Test, n = 24), undersized preparation; Group B (Control, n = 24), non-undersized preparation. The animals were euthanatized to obtain 5 and 10 weeks of implantation time. Removal torque (RTQ) was measured on 12 implants of each group and the peri-implant bone was µ-CT scanned. Bone volume density (BV/TV) was calculated in pre-determined cylindrical volumes, up to 1.5 mm from implant surface. Non-decalcified histology was prepared on the remaining 12 implants from each group, where total bone-to-implant contact (totBIC) and newly-formed BIC (newBIC) was measured. Bone Area Fraction Occupancy (BAFO) was determined in pre-determined areas up to 1.5 mm from implant surface. Paired sample t test or Wilcoxon signed-rank test was used to investigate differences between the groups. RESULTS: Group A presented significantly increased RTQ value at 5 weeks, while no difference was observed at 10 weeks. Group B presented increased BV/TV value at 5 weeks. Both groups showed comparable values for totBIC at both time-points. However, Group A presented significantly lower newBIC at 5 weeks. Higher BAFO was observed in Group B at 5 weeks. CONCLUSIONS: Implants inserted into undersized sites has an increased biomechanical performance, but provoked major remodeling of the cortical bone during the early healing period compared to non-undersized preparations. After 10 weeks, no difference was observed.

DOI： 10.1111/clr.13262

Language：English   Publishing type：Research paper (scientific journal)  

© 2018 by Quintessence Publishing Co Inc. Purpose: The purpose of this study was to examine the volumetric alterations and osseointegration properties in the augmented area of the ring technique using different types of bone graft material in sheep mandible bone. Materials and Methods: Three different materials (columnar forms, 7-mm diameter, 3-mm height) were stabilized using dental implants with a turned surface in the mandible bone of Finnish Dorset cross-bred sheep: group A, autogenous bone; group B, bovine bone; group C, biphasic bone substitute. Animals were euthanized after 5 weeks (N = 6). Three-dimensional image data by digital oral scanner were taken at the surgery and sacrifice, and the volume alteration of the material was calculated. The bone samples were fixed in formalin and dehydrated in ethanol. Resin-embedded samples were subjected to non-decalcified ground sectioning, and histologic and histomorphometric analysis (bone and material area alteration, bone-to-implant contact [BIC]) were done. Results: In three-dimensional (3D) image analysis, group A showed a statistically higher percentage of remaining materials compared with groups B and C. The histologic observation showed no new bone formations around the implants in all groups, especially at the maxillary site of the implant in the augmented area. In histomorphometric analysis, group A showed a statistically higher percentage of bone area (BA) compared with groups B and C; however, in all groups, bone-to-implant contact (BIC) showed low values, and there were no statistical differences between groups. Conclusion: The results of this study suggested that the autogenous bone maintained bone volume around the dental implant using the ring technique, and the impact of surface properties was of some importance; osseointegration with the turned surface in the augmented area showed low BIC values in all groups.

DOI： 10.11607/jomi.6278

Language：English   Publishing type：Research paper (scientific journal)  

OBJECTIVES: The release of magnesium ions (Mg2+ ) from titanium surfaces has been shown to boost the initial biological response of peri-implant bone and to increase the biomechanical strength of osseointegration. The objective of the present paper was to investigate if the initial improvement in osseointegration would influence the bone remodeling also during the maturation stage of bone healing. METHODS: Titanium implants were coated with mesoporous titania layers and either loaded with Mg2+ (test group) or left untreated (control group). The implants were inserted in the tibiae of 10 New Zealand White rabbits. Osseointegration was assessed after 6 weeks by means of biomechanical testing (RTQ), non-decalcified histology and histomorphometry (BIC&#37;, BA&#37;, NBA&#37;). The expression of genes involved in the bone formation and remodeling was quantified using qPCR. RESULTS: Mg2+ releasing mesoporous titania coatings showed, on average, higher removal torques and histomorphometrical outcomes (RTQ: 17.2 Ncm vs. 15 Ncm; BIC: 38.8&#37; vs. 32.1&#37;; BA&#37;: 71.6&#37; vs. 64&#37;; NBA&#37; 62.5&#37; vs. 54&#37; for the tests vs the controls); however, the differences were not statistically significant. Three osteogenic markers, osteocalcin (OC), collagen 1 alpha 1 (COL1A1), and alkalin phosphatase (ALPL), were respectively 2-fold, 1.53-fold, and 1.13-fold up-regulated in the control group compared to the test. The expression of COL1A1 was particularly high in both groups, while the biomarkers for remodeling and inflammation showed a low expression in both groups. SIGNIFICANCE: The results suggested that the initial enhancement in osseointegration induced by magnesium release from mesoporous titania coatings has no detrimental effects during bone maturation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2118-2125, 2017.

DOI： 10.1002/jbm.b.33752

Language：English   Publishing type：Research paper (scientific journal)  

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: &#37;), 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.

DOI： 10.1007/s10266-017-0298-1

Language：English   Publishing type：Research paper (scientific journal)  

PURPOSE: Based on the current evidence, the effect of implant macrogeometry has a significant influence on osseointegration. Thus, this study evaluated histomorphometrically and histologically the bone response to acid-etched in comparison to grit-blasted/acid-etched (GB) and machined control (C) surfaced implants possessing identical macrogeometry placed in high-density bone. MATERIALS AND METHODS: Implant surface topography of the 3 different surfaced implants has previously been characterized. The macrogeometry of the implants were conical, and healing chambers were created in the cortical regions. The 3 groups were placed in the external mandibular body of adult male sheep (n = 5). After 6 weeks in vivo, all samples were retrieved for histologic observation and histomorphometry (eg, bone-to-implant contact [BIC] and bone area fraction occupancy [BAFO]). RESULTS: No statistical difference was observed for BIC and for BAFO, although there was a tendency that the mean values for BAFO was higher for the textured surface groups. CONCLUSIONS: It is suggested that the effect of surface topography is minimal in high-density bone and osseointegration seemed to be macrogeometry dependent.

DOI： 10.1097/ID.0000000000000672

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.5037/jomr.2016.7402

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1097/ID.0000000000000447

Language：English   Publishing type：Research paper (scientific journal)  

PURPOSE: To investigate the causes for internal implant fractures, which is suggested to be one of the reasons for marginal bone loss. MATERIALS AND METHODS: From a 14-year database of 6051 implants, 10 single implant vertical fractures were identified and the abutments were all castable abutments. The abutments presented contamination and irregularities at the internal connecting areas. The hypothesis was that perfect fit was disturbed by laboratory polishing procedures, and finite element analysis (FEA) using overcorrected and undercorrected castable abutment models were created and tested against a perfect fit model. RESULTS: The results from the FEA presented that both overcorrected and undercorrected models presented nonuniform excessive plastic strain distribution in the neck portion of the implants where clinically an implant fracture was noted. CONCLUSIONS: The results suggested that laboratory procedures could induce plastic strain of the implant-abutment complex, which increases the risk of fracture.

DOI： 10.1097/ID.0000000000000392

Language：English   Publishing type：Research paper (scientific journal)  

OBJECTIVES: When implants are inserted, the initial implant stability is dependent on the mechanical stability. To increase the initial stability, it was hypothesized that bone condensation implants will enhance the mechanical stability initially and that the moderately rough surface will further contribute to the secondary stability by enhanced osseointegration. It was further hypothesized that as the healing progresses the difference in removal torque will diminish. In addition, a 3D model was developed to simulate the interfacial shear strength. This was converted to a theoretical removal torque that was compared to the removal torque obtained in vivo. MATERIAL AND METHODS: Condensation implants, inducing bone strains of 0.015, were installed into the left tibia of 24 rabbits. Non-condensation implants were installed into the right tibia. All implants had a moderately rough surface. The implants had an implantation time of 7, 28, or 84 days before the removal torque was measured. The interfacial shear strength at different healing time was estimated by the means of finite element method. RESULTS: At 7 days of healing, the condensation implant had an increased removal torque compared to the non-bone-condensation implant. At 28 and 84 days of healing, there was no difference in removal torque. The simulated interfacial shear strength ratios of bone condensation implants at different implantation time were in line with the in vivo data. CONCLUSIONS: Moderately rough implants that initially induce bone strain during installation have increased stability during the early healing period. In addition, the finite element method may be used to evaluate differences in interlocking capacity.

DOI： 10.1111/clr.12748

Language：English   Publishing type：Research paper (scientific journal)  

© 2016, International Journal of Clinical and Experimental Medicine. All rights reserved. Objective: To compare the comprehensive quality between eight-year Stomatology Medical Doctor (S.M.D) Program students of China and doctoral dental students of Japan, hoping to provide some references for improving dental education in China. Methods and materials: Data were collected from self-answered scoring questionnaires, answered by participants from China and Japan. Results: The study showed Chinese student got higher scores in fields of basic knowledge, basic medical knowledge and basic legal knowledge, although their knowledge still needed improving. Chinese students also got higher scores in dental professional quality items, except for teaching capability. They should improve scientific research ability and teaching capability as well. Japanese students got lower scores in items of oral professional diagnosis, treatment level and professional foreign language proficiency. Conclusion: For general quality, Chinese students got higher scores except for social acceptability. Innovation capability and international communication skills were shortcomings for both Chinese and Japanese students. The comparison provides insight of this new dental education program and the program requires further reform in the future.

Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: The purpose of this study was to compare the study conditions of dental students towards dental education in China and Japan. METHODS: 60 students from the Stomatology School of China Medical University and 51 students from the Dental Faculty of Kyushu University, Japan, participated in this study. Information was derived from a self-answered questionnaire consisting of 10 items. RESULTS: More Japanese students (60&#37;) compared to Chinese students (28&#37;) were satisfied with their lives in dental school. For the main reason of discontent, 23.5&#37; of the Japanese students attributed to busy study and lacking of spare time, while 38.3&#37; of the Chinese students indicated small campus lacking of infrastructure. CONCLUSIONS: Both students of two countries think they were in big pressure. The main stressor of Japanese students was the examination, but that of Chinese students was anxiety of their future and obtains employment. The main source of tuition and maintenance was family in the both countries, but more Japanese students (25.5&#37;) were dependent on scholarship compared with Chinese students (3.3&#37;). CLINICAL IMPLICATIONS: The findings from this study enhance our understanding of study conditions among dental students and help to define strategies to improve student management in both Japan and China.

Language：Others   Publishing type：Research paper (scientific journal)  

© Springer-Verlag Berlin Heidelberg 2015. Many implant surfaces and surface-modification techniques have been examined, and anodized surface on dental implant has been in continued clinical use and has demonstrated good stability during the healing phase. This proof has provided the basis for treatment modality of immediate function. In this chapter, the evidences based on the clinical and basic study reporting the success of osseointegrated implants regarding anodized surface will be reviewed. An understanding of the current evidence may facilitate the most appropriate utilization of this important dental resource.

DOI： 10.1007/978-3-662-45379-7_10

Language：English   Publishing type：Research paper (scientific journal)  

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&#37; 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&#37; of Chinese students and 53&#37; 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.

DOI： 10.1111/idj.12065

Language：English   Publishing type：Research paper (scientific journal)  

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&#37; 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&#37; of them, dentistry was a passive choice. More Chinese dental students (74&#37;) wanted further education compared with Japanese students (22&#37;). The majority of Japanese students (56.9&#37;) planned to work as general dentists. Conversely, Chinese students were more likely to specialise (50&#37;). More than 50&#37; of Japanese students wanted to work in dental offices, but the majority of Chinese students (65&#37;) 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.

DOI： 10.1111/idj.12064

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OBJECTIVE: Implant designs that can stimulate and integrate with an epithelial wound-healing process may significantly enhance the efficacy of dental implants. Here, we evaluated the potential of "step-type" implant systems to improve the sealing between the peri-implant epithelium (PIE) and the implant surface, and investigated the effect of implant structure on PIE down-growth. MATERIALS AND METHODS: Right maxillary first molars were extirpated from rats and implanted with either a straight-type or a step-type implant varying in step height and/or width (N(s): 0.8 mm height, 0.1 mm width; W(s): 0.8 mm height, 0.2 mm width; H(s): 0.4 mm height, 0.1 mm width). Maxillae were harvested at various time points over 16 weeks to evaluate laminin-5 distribution as an indicator of wound healing and PIE formation, horse-radish peroxidase (HRP) penetration as a measurement of epithelial sealing, and PIE down-growth formation. RESULTS: In all implant models, the PIE formed from the oral sulcular epithelium and spread apically along the implant surface. In the W(s) group, HRP penetration was detected only in the coronal region of the PIE at 4 weeks, whereas in the straight-type, it was observed in the apical region and the connective tissue. At 16 weeks, the W(s) implants exhibited markedly less PIE down-growth than the Con, N(s) or H(s) implants, and were equivalent to that observed in natural teeth. CONCLUSION: The step-type implant system may have the potential for improving epithelial sealing at the tissue-implant interface, as well as reducing apical PIE down-growth, thus enhancing dental implant efficacy.

DOI： 10.1111/j.1600-0501.2011.02163.x

Language：English   Publishing type：Research paper (scientific journal)  

Statins are cholesterol-lowering drugs that have been reported to promote bone formation. The purpose of this study was to investigate the effect of simvastatin on the enhancement of bone formation around titanium implants. Thirty-week-old female rats received pure titanium implants in both tibiae. The animals were intra-peritoneally administered 0, 0.125, 1, 5 or 10 mg kg(-1) of simvastatin daily. After 30 days, the animals were sacrificed, and specimens were prepared. The bone contact ratio of the implant, bone density in the medullary canal and percentage of cortical bone were obtained. Markers for bone turnover were also measured using sera collected at the time of euthanasia. In the medullary canal, a scanty amount of bone was observed in the 0, 0.125 and 1 mg kg(-1) groups. In contrast, in both the 5 and 10 mg kg(-1) groups, thicker bone trabeculae were abundant. Histometric observations showed that the bone contact ratio and the bone density of both groups were significantly greater than those of the other groups (anova, P < 0.01). However, no significant difference in the percentage of cortical bone was found between groups. Serum chemistry showed that statin increased bone formation markers and decreased bone resorption markers. In conclusion, although the dose equivalent to that used in human patients with hypercholesterolemia was not effective, a simvastatin dose of 5 mg kg(-1) or higher increased medullary bone formation around the titanium. In contrast, no effect of simvastatin on pre-existing cortical bone was indicated.

DOI： 10.1111/j.1365-2842.2009.02011.x

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Language：English   Publishing type：Research paper (scientific journal)  

The aim of this study was to evaluate the effects of newly developed injectable poly (lactic-co-glycolic acid) (PLGA) microspheres containing fluvastatin on osteogenesis around titanium implants in the rat tibia. After confirmation of the sustained-release profile of fluvastatin from the microspheres by an in vitro assay, the microspheres were administered to the back skin of the rats by a single transdermal injection. At 2 and 4 weeks after the implant surgery, the fluvastatin groups showed enhanced new bone formation around the titanium implants without any influence on the serum biochemistry. In addition, the fluvastatin groups showed increased three-point bending strengths of their femurs. The results of this study indicate that a single remote injection of PLGA/fluvastatin microspheres safely and successfully stimulated bone formation around titanium implants and increased the mechanical properties of bone.

DOI： 10.1016/j.biomaterials.2010.01.016

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

OBJECTIVES: HMG-CoA reductase inhibitors (statins) are widely used for hyperlipidemia. Previous studies demonstrate that statins stimulate bone morphogenetic protein-2 (BMP-2) expression and lead to bone formation. The aim of this study was to evaluate whether percutaneously injected statin with a novel statin delivery system achieved vertical bone augmentation. MATERIAL AND METHODS: As experimental groups, atelocollagen-alpha-tricalcium phosphate (alphaTCP) composites containing 3.3 mg (low dose) or 6.7 mg (high dose) of fluvastatin were injected (one shot) subcutaneously over the calvarial periosteum of rats. The animals were then sacrificed 1, 2, and 4 weeks after injection. Vertically augmented bone was assessed by histomorphometric procedures, i.e., by measuring new bone thickness (NBT) and bone density (BD). RESULTS: In control groups, no newly formed bone could be seen over the calvarial bone. In the experimental groups, in contrast, a large amount of newly formed bone could be seen over the preexisting calvarial bone. The newly formed bone was seen to be in direct contact with the preexisting bone. During the entire observation, significant NBT was observed in the experimental groups (P<0.05). At the final stage of observation (4 weeks), NBT was 66.7&#37; (low-dose group) and 59.7&#37; (high-dose group), while they were from 1&#37; to 16.3&#37; in the control groups. In the experimental groups, BD significantly increased in a time-dependent manner. CONCLUSION: Percutaneously applied fluvastatin (one shot) with a composite of alphaTCP and collagen has great potential to augment the height of the bone.

DOI： 10.1111/j.1600-0501.2008.01665.x

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Language：Japanese   Publisher：医歯薬出版(株)  

Language：Japanese   Publisher：医歯薬出版(株)  

Language：Japanese   Publisher：医歯薬出版(株)  

Language：Japanese   Publisher：医歯薬出版(株)  

Language：Japanese   Publisher：医歯薬出版(株)  

Language：Japanese   Publisher：医歯薬出版(株)  

Language：Japanese   Publisher：(株)ヒョーロン・パブリッシャーズ  

Language：Japanese   Publisher：(公社)日本口腔インプラント学会  

インプラント体周囲硬組織の評価は,治療計画の立案から経過観察に至るまでのすべてのタイミングにおいて治療の成功・失敗に直結する重要事項である.臨床現場における主な硬組織評価法はエックス線診断・埋入トルク値の計測・共振周波数解析であり,非常に有効な評価方法であることがすでに多くの基礎研究・臨床研究で示されている.さらなるインプラント治療の高い成功率の達成のためには,これらの硬組織評価方法では評価できない骨内変化を理解することが必要であると考えている.本論文では主に埋入術式の違い,荷重負荷の有無による骨内変化に焦点を当てて解説する.研究データの積み重ねにより,解剖学的なリスクの回避,適切な部位への埋入といった従来の評価基準に加え,適切な埋入術式,適切な荷重負荷開始時期,さらには周囲骨吸収の予測などが術前に評価可能となるオーダーメイド型の硬組織評価法が構築されていくことを期待している.(著者抄録)

Language：English   Publisher：(公社)日本補綴歯科学会  

Publishing type：Book review, literature introduction, etc.  

Purpose: The aim of this study was to review the literature on current surface modification strategies used to improve the binding efficiency of an emerging biological material, polyetheretherketone (PEEK), with bone and soft tissues. Study selection: This review was based on articles retrieved from PubMed, Google Scholar, Web of Science, and Scien-ceDirect databases. The main keywords used during the search were “polyetheretherketone (PEEK),” “implant,” “surface modification,” “biomaterials,” “bone,” “osseointegration,” and “soft tissue.” Results: The suitability of PEEK surface modification strategies has been critically analyzed and summarized here. Many cell and in vivo experiments in small animals have shown that the use of advanced modification technologies with appropriate surface modification strategies can effectively improve the surface inertness of PEEK, thereby improving its binding efficiency with bone and soft tissues. Conclusions: Surface modifications of PEEK have revealed new possibilities for implant treatment; however, most results are based on in vitro or short-term in vivo evaluations in small animals. To achieve a broad application of PEEK in the field of oral implantology, more in vivo experiments and long-term clinical evaluations are needed to investigate the effects of various surface modifications on the tissue integration ability of PEEK to develop an ideal implant material.

DOI： 10.2186/jpr.JPR_D_22_00138

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インプラント治療は,口腔内欠損補綴治療になくてはならない治療オプションの一つである.初期固定はオッセオインテグレーション獲得の必要条件であり,即時負荷・早期負荷が一般的な術式になるに従い,より安定した初期固定が要求されるようになってきた.高い初期固定値獲得のため,インプラント体のマクロ・マイクロレベルのデザインの変更,新しい術式など多くの工夫が紹介されてきた.アンダーサイズドリリングテクニックは最も一般的に臨床採用されているインプラント外科手技である.埋入するインプラント体の直径より小さな径の埋入窩を形成することにより,インプラント体と骨の界面で生じる圧縮応力に期待し初期固定を得る術式である.外科医は,埋入トルク値としてその効果を感じることができる.アンダーサイズドリリングは広く普及した術式であるが,まだまだ解明されていない側面も多い.インプラント体埋入時の大きな圧縮力が周囲骨組織の微小損傷を惹起し,治癒期間中にネガティブな影響を与える.すなわち骨の材料特性の低下・インプラント体の安定の低下・周囲骨の吸収・そして最悪の場合インプラント体の喪失につながる可能性があるという仮説のもと,アンダーサイズドリリングテクニックについてさらなる理解を深めることが本論文の目的である.われわれの研究の着想に至った背景および,第48回日本口腔インプラント学会学術大会・シンポジウム10で発表した研究結果を紹介する.(著者抄録)

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インプラントの表面性状に関する研究は過去20年間活発に行われている。開発当初のインプラント体表面は滑面であったが、治療期間の短縮と、より強固なオッセオインテグレーション獲得を目指して、様々な粗面性状の研究がなされてきた。これまでのインプラント表面改質に関する研究の変遷と現状、さらに今後の展望について解説した。

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症例の概要:患者は初診時61歳の男性。悪性リンパ腫に対する放射線治療後の部分無歯顎に対する補綴治療の症例である。右下顎歯7、6、5部にインプラントを埋入し、コーヌス型オーバーデンチャーで補綴を行った。考察:インプラント体埋入位置が限定され、最終補綴装置の設計も力学的に問題のある設計となった。しかし、最終補綴装置装着後の定期的なメインテナンスによりインプラント体自体に大きな問題は生じていない。今後さらに経過を観察していく必要がある。結論:放射線治療後の下顎部分無歯顎症例に対し、インプラントを用いたコーヌス型オーバーデンチャーで咬合支持を再建することができた。(著者抄録)

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インプラント治療において、骨量不足症例への挑戦が増加し、骨増生の重要性が高まっている。骨増生に関する我々の研究を紹介する。(1)骨増生の簡便化を目指し新術式の開発を行っている。単回のスタチン注射投与による無切開・非侵襲的骨増生を提案する。スタチンの骨形成作用に関する研究から、今回の開発に至った経緯について解説する。(2)"骨を模倣する"というコンセプトで骨補填材料の開発を行っている。組織再生に必要な要素として、細胞、成長因子、足場、血流が知られており、骨とりわけ海綿骨はすべての要素を含んでいる。合成高分子化合物をスタート材料とした、海綿骨を模倣した自己細胞侵入型骨補填材を紹介する。(著者抄録)

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咀嚼能力はその評価すべき特性の多面性からこれまでに直接的及び間接的な評価法が多数検討されており、グミゼリーを被験食品とした研究では、成分の溶出計測や粉砕状況に応じたスコア化など種々の評価法を用いた報告がなされている。しかし、グミゼリー食塊粒子の詳細な粒度解析と成分溶出との関係についてはいまだ明らかになっていない。そこで本研究は、検査用グミゼリーを被験食品として含有β-カロチンの溶出量と、視覚判定による咀嚼能率スコアならびに画像解析による粒度解析との比較を行うことを目的とした。被験者は、成人健常有歯顎者17名(男性9名、女性8名、25～53歳、平均30.8±6.9歳)とした。粒度計測はデジタル画像解析にて行い、β-カロチンは35℃の水に対する規定条件下での溶出量を評価した。咀嚼能率スコアは標準画像との比較により視覚的に決定した。咀嚼能率スコアと被験食塊中の最大粒子面積との間には有意の負の相関関係(p<0.001)が認められた。また1mm2～50mm2の面積をもつ粒子の合計面積が咀嚼塊総面積に占める比率と溶出評価用センサ出力電圧との間に有意の負の相関関係(p<0.001)が認められた。以上の結果より、検査用グミゼリーからのβ-カロチン溶出量、目視による咀嚼能率スコアならびに粒度解析の結果は互いに相関関係が認められることが示された。(著者抄録)

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The Adhesion of Oral Epithelial Cells to the Titanium Implant : The Role of Phosphatidylinositol 3-Kinase

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Comparative Studies of the Peri-implant Epithelium of Rat Gingivae between "Step-type" and "Straight-type" Implant System

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