A novel dual material mouthguard for patients with dental implants.

AIM: Dental implant-supported reconstructions demonstrate significantly less physiological flexibility for loading and traumatic forces compared with a normal dentition because of their rigid integration with the adjacent bone. Ethylene vinyl acetate (EVA) material has become widely accepted as a mouthguard material; however, many studies indicate the necessity of improving the impact absorption ability by considering the design and developing new materials. The aim of this study was to compare the shock-absorbing ability of a novel dual component material comprising EVA and porous rubber with that of EVA alone. MATERIALS AND METHODS: Three groups of samples were tested: Group 1 = EVA (thickness, 4 mm), Group 2 = type 1 material (2-mm thick porous rubber sheet sandwiched between two sheets of 1-mm thick EVA sheets), and Group 3 = type 2 material (1-mm thick porous rubber sheet sandwiched between EVA sheets with 1 and 2-mm thickness, respectively). Shock absorption was determined by means of a hammer impact testing device equipped with strain gauge, accelerator, and load cell. RESULTS: The value of shock-absorbing ability of group 2 (40.6 ± 12.5%) was significantly higher than those of group 1 (15.6 ± 2.1%) and group 3 (21.2 ± 9.2%). The material with thicker rubber sheet showed significantly higher shock-absorbing ability compared with that of the material with thinner rubber sheet. CONCLUSIONS: The novel dual material was superior to conventional EVA material in shock-absorbing ability depending on the thickness of porous rubber, and it may be potentially effective as mouthguard material, in particular, for patients wearing implant-supported constructions.

Vertical ridge augmentation using a porous composite of uncalcined hydroxyapatite and poly-DL-lactide enriched with types 1 and 3 collagen.

BACKGROUND: Previous studies have shown that porous composite blocks containing uncalcined hydroxyapatite (u-HA; 70 wt%) with a scaffold of poly-DL-lactide (PDLLA, 30 wt%) are biodegradable, encourage appropriate bone formation, and are suitable for use as a bone substitute in vertical ridge augmentation. The present study aimed to accelerate osteogenesis in vertical ridge formation by adding types 1 and 3 collagen to the u-HA/PDLLA blocks and assessing the effect. MATERIAL AND METHODS: The bone substitute in the present study comprised porous composite blocks of u-HA (70 wt%) with a PDLLA (27-29 wt%) scaffold and enriched with types 1 and 3 collagen (1.7 ~ 3.4 wt%). The control blocks were composed of u-HA (70 wt%) and PDLLA (30 wt%). The materials were formed into 8-mm diameter, 2-mm high discs and implanted onto the cranial bones of six rabbits. The animals were sacrificed 4 weeks after implantation, and histological and histomorphometrical analyses were performed to quantitatively evaluate newly formed bone. RESULTS: New bone formation occurred with both block types, showing direct contact with the original bone. Mean ± standard deviation bone formation was significantly greater in the experimental blocks (25.6% ± 4.8%) than in the control blocks (17.0% ± 4.7%). CONCLUSIONS: Histological and histomorphometrical observations indicated that new bone was formed with both block types. The u-HA/PDLLA block with types 1 and 3 collagen is a more promising candidate for vertical ridge augmentation than the u-HA/PDLLA alone block.

Guided bone regeneration using a hydrophilic membrane made of unsintered hydroxyapatite and poly(L-lactic acid) in a rat bone-defect model.

The effectiveness of a previously developed unsintered hydroxyapatite (uHA) and poly(L-lactic acid) (PLLA) hydrophilic membrane as a resorbable barrier for guided bone regeneration (GBR) was evaluated. Critical-size 8-mm diameter bone defects were surgically generated in the parietal bones of 24 12-week-old male Wistar rats, which were then divided into three groups in which either a uHA/PLLA or a collagen membrane or no membrane (control) was placed onto the bone defect. Following sacrifice of the animals 2 or 4 weeks after surgery, bone defects were examined using microcomputed tomography and histological analysis. Bone mineral density, bone mineral content, and relative bone growth area values 2 or 4 weeks after surgery were highest in the uHA/PLLA group. Four weeks after surgery, the relative bone growth area in the uHA/PLLA group was larger than that in the collagen group. The resorbable uHA/PLLA membrane is thus potentially effective for GBR.

Effects of a polysaccharide nanogel-crosslinked membrane on wound healing.

INTRODUCTION: Wound-dressing materials that promote wound healing while protecting wounds from infections are advantageous for clinical applications. Hence, we developed a cholesterol-bearing pullulan (CHP) nanogel that stimulated wound healing; however, it was mechanically weak and difficult to handle. Thus, the purpose of this study was to examine precisely the effects of a mechanically reinforced nanogel-crosslinked (NanoClik) membrane on wound healing. MATERIALS AND METHODS: NanoClik was prepared by mixing a thiol-terminated polyethylene glycol solution and an acryloyl group-modified CHP nanogel solution. A thin silicone sheet membrane, which was combined with NanoClik, was prepared. The NanoClick membranes and both positive and negative control membranes (collagen combined with silicone membrane and silicone membrane alone, respectively) were tested in vivo using a dorsal skin defect rat model. The rate and extent of wound healing was compared between groups after 7 and 14 days of implantation. RESULTS: In the NanoClik membrane group, the wound area was significantly reduced and neoepithelialization was promoted, compared with that observed in the other groups. In addition, extension and accumulation of collagen fibers were evident in the NanoClik membrane group. CONCLUSION: The NanoClik membrane is a strong candidate for use as an effective and safe wound-dressing material. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 544-550, 2017.

Lateral Bone Window Closing Technique with Poly-L-Lactic Acid (PLLA) Membrane in the Augmentation of the Maxillary Sinus without Grafting Material: Evaluation of Bone Healing in a Rabbit Model.

BACKGROUND: When augmenting the maxillary sinus without grafting material, the method used to cover the bony window is a subject of debate. PURPOSE: The purpose of this study was to evaluate the poly-L-lactic acid (PLLA) membrane as closing material of the lateral window in a maxillary sinus augmentation without bone grafting. MATERIALS AND METHODS: Augmentation of the maxillary sinus without grafting material and installation of titanium screws that fix the Schneiderian membrane were performed in 18 Japanese male white rabbits. The bony window was covered with a collagen membrane or PLLA membrane or no membrane. The animals were sacrificed at 4 or 8 weeks. New bone volume was calculated radiologically using microcomputed tomography (micro-CT). The samples were analyzed histologically after toluidine blue staining. RESULTS: No significant differences were observed in the new bone volume, as measured by micro-CT. However, histomorphometric analysis demonstrated the superiority of the PLLA membrane in new bone formation compared with the collagen membrane. CONCLUSION: The PLLA membrane is a suitable material to be applied for tissue regeneration in this animal model.

Decontamination of Anodized Implant Surface With Different Modalities for Peri-Implantitis Treatment: Lasers and Mechanical Debridement With Citric Acid.

BACKGROUND: Although oral rehabilitation with dental implants is a very promising and effective procedure, peri-implantitis is an emerging concern. Surgical and non-surgical methods have been applied to treat peri-implantitis together with various implant surface decontamination methods. However, there is no consensus concerning the most effective treatment for peri-implantitis. The aim of the present study is to evaluate the effects of erbium-doped:yttrium, aluminum, and garnet (Er:YAG) laser, photodynamic therapy (PDT), and titanium bur with and without citric acid on ligature-induced peri-implantitis around an anodized implant surface. METHODS: Thirty dental implants with anodized surface (3.3 × 10 mm) were installed in the mandibles of five beagle dogs. After 3 months, peri-implantitis was induced by applying cotton ligatures subgingivally. After ligature removal (baseline), the implants were divided into the following treatment groups: 1) Er:YAG laser, 2) PDT, 3) titanium bur alone, and 4) titanium bur with citric acid. Animals were sacrificed after 3 months, and clinical, radiologic, histologic, and histomorphometric evaluations were conducted for all treatment modalities. The data were analyzed using one-way analysis of variance and Tukey test. A value of P <0.05 was considered statistically significant. RESULTS: The titanium bur with citric acid group exhibited statistically significantly greater improvement in vertical bone height than the Er:YAG laser group and significantly better bone-to-implant contact than the PDT group and the bur-alone group. CONCLUSION: Within the limits of the study, the combination of mechanical and chemical treatment proved to be the most effective treatment for disinfection of the anodized implant surface.

Accelerated and enhanced bone formation on novel simvastatin-loaded porous titanium oxide surfaces.

BACKGROUND: With increasing application of dental implants in poor-quality bones, the need for implant surfaces ensuring accelerated osseointegration and enhanced peri-implant bone regeneration is increased. PURPOSE: A study was performed to evaluate the osseointegration and bone formation on novel simvastatin-loaded porous titanium oxide surface. MATERIALS AND METHODS: Titanium screws were treated by micro-arc oxidation to form porous oxide surface and 25 or 50 µg of simvastatin was loaded. The nontreated control, micro-arc oxidized, and simvastatin-loaded titanium screws were surgically implanted into the proximal tibia of 16-week-old male Wistar rats (n = 36). Peri-implant bone volume, bone-implant contact, and mineral apposition rates were measured at 2 and 4 weeks. Data were analyzed by one-way analysis of variance followed by Tukey's post hoc test. RESULTS: New bone was formed directly on the implant surface in the bone marrow cavity in simvastatin-loaded groups since 2 weeks. Bone-implant contact values were significantly higher in simvastatin-loaded groups than control and micro-arc oxidized groups at both time points (p < .05). Peri-implant bone volume and mineral apposition rate of simvastatin-loaded groups were significantly higher than control and micro-arc oxidized groups at 2 weeks (p < .05). CONCLUSIONS: These data suggested that simvastatin-loaded porous titanium oxide surface provides faster osseointegration and peri-implant bone formation and it would be potentially applicable in poor-quality bones.

Feasibility of alpha tricalcium phosphate for vertical bone augmentation.

AIM: Inadequate vertical bone compromises dental implant positioning and subsequent restoration. This study was carried out to investigate the feasibility of alpha tricalcium phosphate (α-TCP) for vertical bone augmentation. METHODS: Nine cortical perforations were made on each side of the parietal bone of rat calvaria under continuous saline coolant. Polytetrafluoroethylene cylinders were placed under the periosteum and α-TCP particles were applied in the cylinders in the TCP group while the cylinders were left empty in the control group. The animals were sacrificed at 4 and 8 weeks after surgery and analyzed radiologically and histologically. RESULTS: The augmented bone volumes in the control and TCP groups were 91.5 ± 25.6% and 76.5 ± 49.8% (mean ± SD) of the original bone at 4 weeks, and 136.3 ± 59.7% and 139 ± 62.4% at 8 weeks respectively. There was no significant difference between control and test groups. At 4 weeks the bone height was augmented by 168.8 ± 26.7% and 128.8 ± 62% in the control and TCP groups respectively (not significant), whereas significantly higher vertical bone was achieved in the TCP group than in the control group at 8 weeks (251 ± 32% vs 179.2 ± 30.3%, P < 0.05). CONCLUSION: After 8 weeks α-TCP is effective in maintaining space under periosteum and potentially would be applicable in vertical bone augmentation.

Exploitation of a novel polysaccharide nanogel cross-linking membrane for guided bone regeneration (GBR).

Cholesterol-bearing pullulan (CHP) nanogel is a synthetic degradable biomaterial for drug delivery with high biocompatibility. Guided bone regeneration (GBR) is a bone augmentation technique in which a membrane is used to create and keep a secluded regenerative space. The purpose of the present study was to evaluate the effects of the novel CHP nanogel membrane in GBR. Thirty-six adult Wistar rats were used and bilaterally symmetrical full-thickness parietal bone defects of 5 mm diameter were created with a bone trephine burr. Each defect was covered with the collagen membrane or the CHP nanogel membrane or untreated without any membrane. The animals were sacrificed at 2, 4 and 8 weeks and analysed radiologically and histologically. Furthermore, after incubating human serum with CHP nanogel or collagen, the amount of PDGF in the serum was measured using ELISA. New bone formation in terms of bone volume was higher in the nanogel group than in the control or collagen groups at 2 and 4 weeks. At 8 weeks, both membrane groups showed higher bone volumes than the control group. Notably, the newly-formed bone in the bone defect in the nanogel group was uniform and histologically indistinguishable from the original bone, whereas in the collagen group the new bone showed an irregular structure that was completely different from the original bone. After incubating with CHP nanogel, the amount of PDGF in the serum decreased significantly. CHP nanogel GBR membrane favourably stimulated bone regeneration, in which a unique characteristic of CHP nanogel, the storage of endogenous growth factors, was likely implicated.

Implantation of green tea catechin α-tricalcium phosphate combination enhances bone repair in rat skull defects.

UNLABELLED: The purpose of the present study is to investigate effects of the combination of epigallocatechin-3-gallate (EGCG) and α-tricalcium phosphate (α-TCP) on bone regenerative capacity in a bilateral rat calvarial bone defect model. MATERIALS AND METHODS: Bilateral 5-mm-diameter calvarial defects were created in adult male Wistar rats and filled with preparations of EGCG (0, 0.1, 0.2, 0.4 mg) combined with α-TCP particles. This was done by dissolving EGCG in 100% ethanol (50 µL/14 mg) and dropping under sterile condition. The control group was left unfilled (n = 8). The animals were sacrificed at 2 and 4 weeks. Radiological images were taken, and histological analysis was done. Six animals from control (0 mg EGCG + α-TCP) group and (0.2 mg EGCG+ α-TCP) group were labeled with fluorescent dyes and histomorphometrically analyzed (n = 6) at 2 and 4 weeks. RESULTS: Histomorphometric analysis revealed that the combination of EGCG and α-TCP at doses of 0.1 and 0.2 mg yielded significantly more new bone formation than untreated control group at 2 and 4 weeks (p > 0.05). Mineral apposition rate at 0.2-TCP group was enhanced compared with the one of the positive control α-TCP group at 4 weeks (p > 0.05). CONCLUSION: The combination of α-TCP particles and 0.2 mg EGCG stimulates maximum bone regeneration in rat calvarial defects, and this combination would be potentially effective as bone graft material.

Molecular and tissue responses in the healing of rat calvarial defects after local application of simvastatin combined with alpha tricalcium phosphate.

We have previously reported that healing of rat calvarial defects was enhanced by application of alpha tricalcium phosphate (alphaTCP) combined with simvastatin, a cholesterol synthesis inhibitor. The purpose of the present study was to investigate the cellular and molecular mechanisms in this phenomenon. Rat calvarial defects were grafted with alphaTCP with or without simvastatin or left untreated. Animals were sacrificed on 3, 7, 10, 14, and 21 days postoperatively and histological changes in the defect region were assessed. Gene expression patterns were examined by RT-PCR. Proliferation and migration of osteoprogenitor cells from the dura mater were increased in simvastatin group from day 3 to day 10 (p < 0.01). New bone formation was significantly increased in simvastatin group on day 14 and day 21 (p < 0.01). BMP-2 expression was significantly higher in simvastatin group on day 3 and day 14 (p < 0.05) and maintained until day 21. Increased upregulation of TGF-beta1 was also observed in the simvastatin group on day 7 (p < 0.05) which was maintained until day 14. These findings suggest that the proliferation and recruitment of osteoprogenitor cells were critical steps in early stage of bone healing and that these steps were enhanced by TGF-beta1 and BMP-2, which were stimulated by simvastatin.

Cellular distribution of Mr 25,000 protein, a protein partially overlapping phosvitin and lipovitellin 2 in vitellogenin B1, and yolk proteins in Xenopus laevis oocytes and embryos.

A phosphorylated protein with molecular mass of 25,000 (pp25) can be derived from Xenopus laevis vitellogenin B1. In order to clarify the distribution of pp25, the changes in the concentration and localization of this protein in oocytes and embryos were examined by immunoblotting and immunohistochemistry using anti-pp25 antibodies, and compared with those of yolk proteins. In oocytes, pp25 was shown to localize characteristically at the surface just below the plasma membrane by immunohistochemical analysis. Interestingly, during embryogenesis, immunocytochemical staining revealed a transition of the pp25 distribution from beneath the outer surface of each germ layers to endoderm during tailbudding. In contrast, yolk proteins were localized in endoderm constantly throughout the developmental stages. However, the level of pp25 in the cytoplasm gradually decreased following the growth of embryos at the tailbud stage and disappeared at the tadpole stage, as shown by immunoblot analysis. These results suggest that pp25 could play different roles from those of yolk proteins such as lipovitellin and phosvitin in X. laevis oocytes and developing embryos.