Identifying the critical areas and primary sources for agricultural non-point source pollution management of an emigrant town within the Three Gorges reservoir area.

Agricultural non-point source pollution is threatening water environmental health of the Three Gorges reservoir. However, current studies for precision management of the agricultural non-point source pollution within this area are still limited. The objective of this study was identifying the critical areas and primary sources of agricultural non-point source pollution for precision management. Firstly, the inventory analysis approach was used to estimate the discharge amount of total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) from farmland fertilizer, crop residues, livestock breeding, and daily activities. Afterwards, the deviation standardization method was applied to evaluate the emission intensity of TN, TP, and COD, as well as calculating the comprehensive pollution index (CPI) of each village, based on which the critical areas for agricultural non-point source pollution management could be distinguished. Moreover, the equivalence pollution load method was conducted to identify the primary pollution sources within each critical zone. The above methods were implemented to an emigrant town within the Three Gorges reservoir area named Gufu. Results showed that agricultural non-point source pollution in Gufu town has been alleviated to a certain extent since 2016. Nevertheless, in four areas of the town (i.e., Longzhu, Fuzi, Shendu, and Maicang), the agricultural non-point source pollution still deserved attention and improvement. For the mentioned critical areas, farmland fertilizer and livestock breeding were the primary sources causing agricultural non-point source pollution. The emission amount of TN and TP from farmland fertilizer accounted for 60% and 48% of the total, respectively. And those from livestock breeding were 29% and 46%. Our research could provide definite targets to relieve agricultural non-point source pollution, which had great significance to protect water environment while coordinating regional economic growth after emigrant resettlement.

Platelet-enriched fibrin glue and platelet-rich plasma in the repair of bone defects adjacent to titanium dental implants.

PURPOSE: The aim of this study was to compare the effects of platelet-enriched fibrin glue and platelet-rich plasma (PRP) on the repair of bone defects adjacent to titanium dental implants. MATERIALS AND METHODS: In 6 mongrel dogs, 3 screw-shaped titanium dental implants per dog were placed into the osteotomy sites in the tibia. Before implantation, a standardized gap (2.0 mm) was created between the implant surface and the surrounding bone walls. Six gaps were left empty (control group), 6 gaps were filled with autogenous particulate bone mixed with PRP (PRP group), and 6 gaps were filled with autogenous particulate bone mixed with platelet-enriched fibrin glue (fibrin glue group). RESULTS: After 6 weeks, the bone-implant contact was 59.7% in the fibrin glue group, 29.2% in the PRP group, and 10.2% in the control defects; this difference was statistically significant (P < .05). DISCUSSION AND CONCLUSION: Greater bone-implant contact was achieved with platelet-enriched fibrin glue than with PRP. The results indicate that platelet-enriched fibrin glue can induce a stronger peri-implant bone reaction than PRP in the treatment of bone defects adjacent to titanium dental implants.

Nerve regeneration with the use of a poly(l-lactide-co-glycolic acid)-coated collagen tube filled with collagen gel.

AIM: The aim of this study was to develop a novel artificial nerve conduit and to evaluate its efficiency based on the promotion of peripheral nerve regeneration in rabbits. MATERIAL AND METHODS: The nerve conduit was made of a poly (l-lactide-co-glycolic acid)-coated collagen tube filled with collagen gel. The conduits were implanted into a 15 mm gap in the peroneal nerves of five rabbits. On the contralateral side, the defects were bridged with collagen-filled vein grafts. RESULTS: Twelve weeks postoperatively nerve regeneration was superior to the vein graft in the PLGA-coated collagen tube, both morphologically and electrophysiologically. CONCLUSION: The results indicate the superiority of the PLGA-coated collagen tube over vein grafts. Furthermore, they show that entubulation repair with this type of tube can support nerve regeneration over a nerve gap distance of at least 15 mm.

Cyanoacrylate adhesive for closing sinus membrane perforations during sinus lifts.

INTRODUCTION: Sinus lift procedures depend greatly on fragile structures and anatomical variations. The procedure may cause sinus membrane perforations, which can lead to graft infection and early failure. AIM: To assess the efficacy of cyanoacrylate adhesive in the management of large perforations of the maxillary sinus membrane during sinus lifts. MATERIAL AND METHODS: Six rabbits were used in the study. Sinus membrane perforations (about 1.5 cm in length) were repaired with cyanoacrylate adhesive on one side of the maxillary sinus. On the contralateral side, an identical laceration was not repaired. Histological evaluation was performed 2 weeks after the operation. RESULTS: Wounds repaired with cyanoacrylate adhesive showed newly formed continuous epithelium across the previous perforation site and there was sinusitis on the contralateral side. CONCLUSION: These results support the clinical use of cyanoacrylate adhesive for repairing sinus membrane perforations.

Injectable bone using chitosan-alginate gel/mesenchymal stem cells/BMP-2 composites.

AIM: Several injectable materials have been used as osteogenic bone substitutes. However, none has gained universal acceptance. This study was performed to investigate whether or not chitosan-alginate gel/mesenchymal stem cells/bone morphogenetic protein-2 composites are potentially injectable materials for new bone formation. MATERIAL AND METHODS: The composites were injected into the subcutaneous space on the dorsum of nude mice to investigate new bone tissue formation. The composites were examined histologically over a 12-week period. RESULTS: The composites injected into the mouse were able to stimulate new bone formation, which was trabecular in type. CONCLUSIONS: This study showed that chitosan-alginate gel/MSCs/BMP-2 composites could become clinically useful injectable materials to generate new bone.

Vertical alveolar ridge augmentation using autogenous bone grafts and platelet-enriched fibrin glue with simultaneous implant placement.

OBJECTIVE: The aim of this study was to evaluate the combined use of autogenous bone and platelet-enriched fibrin glue as grafting material for vertical alveolar ridge augmentation with simultaneous implant placement in a canine alveolar ridge defect model. STUDY DESIGN: In 6 mongrel dogs, bilateral vertical alveolar ridge defects were created in the mandible. After 3 months of healing, 2 dental implants were placed in each defect of the mandible, creating 6-mm supra-alveolar peri-implant defects. The 2 implants per defect were subjected to surgical treatments involving either a combination of autogenous bone grafts and platelet-enriched fibrin glue, or a conventional flap procedure only (control). After a healing period of 6 months, the dogs were humanely killed for histological and histometric analyses. RESULTS: Implant placement alone produced limited vertical alveolar height (0.6 +/- 0.4 mm). However, alveolar augmentation including a combination of autogenous bone grafts and platelet-enriched fibrin glue with simultaneous implant placement resulted in alveolar ridge augmentation amounting to 4.2 +/- 1.0 mm, comprising 63% of the defect height. New bone-implant contact was 40.5% in the defects treated with combined autogenous bone grafts and platelet-enriched fibrin glue, and was 48.4% in the resident bone; this difference was not statistically significant. CONCLUSION: The present study demonstrates that vertical alveolar ridge augmentation using autogenous bone grafts and platelet-enriched fibrin glue with simultaneous implant placement might effectively increase vertical alveolar ridge height and allow for an acceptable level of osseointegration.

Maxillary sinus floor augmentation using autogenous bone grafts and platelet-enriched fibrin glue with simultaneous implant placement.

OBJECTIVE: The aim of this study was to evaluate the use of autogenous bone in combination with platelet-enriched fibrin glue as a grafting material for maxillary sinus augmentation with simultaneous implant placement in dogs. STUDY DESIGN: The mucous membranes of 12 sinuses in 6 dogs were elevated bilaterally. In the right sinus, autogenous bone mixed with platelet-enriched fibrin glue was grafted into the space between the membrane and the sinus wall. In the left sinus, autogenous bone alone was grafted as a control. At the same time, 2 dental implants were inserted into the grafting material through the maxillary sinus floor. The animals were killed 6 months after surgery. RESULTS: The mean bone-implant contact was 40.5% on the fibrin glue side and 32.3% on the control side (P < .05). The mean height of newly formed bone in the augmented area was 12.2 mm on the fibrin glue side and 10.7 mm on the control side (P < .05). CONCLUSION: The results indicate that the use of autogenous bone mixed with platelet-enriched fibrin glue can achieve results superior to those for grafts of autogenous bone alone. The specific improvements of this technique include enhanced osseointegration of dental implants and increased height of new bone.

Treatment of experimental peri-implantitis using autogenous bone grafts and platelet-enriched fibrin glue in dogs.

OBJECTIVE: The purpose of this study was to evaluate the effects of autogenous bone grafts and platelet-enriched fibrin glue in the treatment of peri-implantitis. STUDY DESIGN: Thirty-six screw-type commercially pure titanium implants with rough acid-etched surfaces were inserted into 6 mongrel dogs 3 months after extraction of mandibular premolars. After 3 months of healing, peri-implantitis was induced by placing gauze and wire around the implants. Once peri-implantitis was created, surgical treatments involving a combination of autogenous bone grafts and platelet-enriched fibrin glue, autogenous bone grafts alone, or a conventional flap procedure only (control) were carried out. Six months later, biopsies of the implant sites were taken and prepared for ground sectioning and analysis. RESULTS: The amount of reosseointegration was significantly higher in peri-implantitis defects treated with combined autogenous bone grafts and platelet-enriched fibrin glue as compared with the other 2 treatment procedures. A mean bone-to-implant contact of 50.1% was obtained in the peri-implantitis lesions treated with combined autogenous bone grafts and platelet-enriched fibrin glue. The corresponding values for the autogenous bone grafts and control groups were 19.3% and 6.5%, respectively. CONCLUSION: The present study demonstrates that surgical treatment involving the combined use of autogenous bone grafts and platelet-enriched fibrin glue might effectively promote reosseointegration in lesions resulting from peri-implantitis.

The use of autologous fibrin glue for closing sinus membrane perforations during sinus lifts.

Sinus lift procedures depend greatly on fragile structures and anatomical variations. These procedures may cause sinus membrane perforations, which can lead to graft infection and early failure. The aim of this study was to assess the efficacy of autologous fibrin glue in the management of large perforations of the maxillary sinus membrane occurring during sinus lifts. After elevating the sinus membrane in the bilateral maxillary sinuses of 6 adult female mongrel dogs, a laceration (about 2.0 cm in length) was made in the membrane and either repaired with autologous fibrin glue or covered with a bioabsorbable collagen membrane as a control. Wounded areas were biopsied 2 weeks after the operation. Wounds repaired with autologous fibrin glue showed newly formed continuous epithelium across the previous perforation site. However, extensive fibrosis, inflammatory infiltration, and absent epithelium were observed in wounds treated with the collagen membrane control. Our results support the clinical use of autologous fibrin glue for repairing sinus membrane perforations.

The effect of platelet-enriched fibrin glue on bone regeneration in autogenous bone grafts.

OBJECTIVE: The aim of this study was to examine the ability of platelet-enriched fibrin glue to enhance bone formation in critically sized defects in the dog mandible. STUDY DESIGN: Seven adult female mongrel dogs underwent continuity resections on both sides of the mandible; 1 defect was reconstructed with the original particulate bone mixed with platelet-enriched fibrin glue, and as a control the contralateral defect was reconstructed with the original particulate bone alone. RESULTS: Biopsies after 6 weeks showed that the addition of platelet-enriched fibrin glue enhanced new bone formation in the autogenous bone grafts. CONCLUSION: Our data suggest that fibrin nets formed by fibrinogen, in combination with growth factors present in platelet-enriched fibrin glue, might effectively promote bone healing at bone graft sites.

A comparative qualitative histological analysis of tissue-engineered bone using bone marrow mesenchymal stem cells, alveolar bone cells, and periosteal cells.

For tissue-engineered bone formation, autogenous osteogenic cells are of paramount importance for successful bone formation. In order to investigate the donor cell-related differences in tissue-engineered bone, cultured bone marrow mesenchymal stem cells, cultured alveolar bone cells, and cultured periosteal cells were examined for their in vivo potential to form bone. These cells were isolated from dogs, expanded in vitro, mixed with autologous fibrin glue and BMP-2, and then injected into the subcutaneous space on the dorsum of nude mice. Bone formation was evaluated at 12 weeks. Histomorphometric analysis demonstrated that the subcutaneous nodules formed in nude mice contained 26.9% newly formed bone when using the bone marrow mesenchymal stem cells, 41.1% newly formed bone when using the alveolar bone cells, and 58.2% newly formed bone when using the periosteal cells. The results suggest that periosteal cells are the best choice for enhancing bone formation in tissue engineering of bone regeneration.

A comparative histologic analysis of tissue-engineered bone using platelet-rich plasma and platelet-enriched fibrin glue.

OBJECTIVE: The aim of this study was to compare the effects of platelet-rich plasma (PRP) and platelet-enriched fibrin glue on bone formation in bone tissue engineering. STUDY DESIGN: PRP was mixed with bone marrow mesenchymal stem cells and bone morphogenetic protein-2 (BMP-2), and the composites were injected into the subcutaneous space on the dorsum of nude mice. On the contralateral side of the dorsum, platelet-enriched fibrin glue/bone marrow mesenchymal stem cells/BMP-2 composites were injected. Bone formation was evaluated after 12 weeks. RESULTS: The volumes of subcutaneous nodules formed in nude mice were 55 +/- 18 microL at the PRP/bone marrow mesenchymal stem cells/BMP-2 sites and 135 +/- 27 microL at the platelet-enriched fibrin glue/bone marrow mesenchymal stem cells/BMP-2 sites. Histomorphometric analysis demonstrated that the nodules contained 14.9 +/- 4.1% newly formed bone when using PRP and 19.8 +/- 3.6% newly formed bone when using platelet-enriched fibrin glue. CONCLUSION: The results indicated that the osteogenic characteristics of platelet-enriched fibrin glue are superior to PRP in bone tissue engineering.

Bridging mandibular continuity defects with miniplates: an experimental study.

Various miniplate fixation techniques were studied in dogs to determine whether the use of miniplate fixation provides sufficient stability in mandibular continuity defects. Continuity resections measuring 15 mm were made on the mandibles of 16 dogs and were bridged using 4 miniplate fixation techniques, each replicated 4 times. All dogs were placed on a normal diet throughout the postoperative period. Clinical and radiological examinations were carried out 6 weeks later. We found that the group with both double miniplates and bicortical screws was stable, whereas the groups utilizing either a single miniplate or monocortical screws were not. The results of this study indicate that using a combination of double miniplates and bicortical screws to bridge defects after mandibular resection produces stable and predictable results.

The effects of exposing dental implants to the maxillary sinus cavity on sinus complications.

OBJECTIVE: The aim of this study was to investigate whether dental implant exposure to the maxillary sinus cavity increases the risk of maxillary sinus complications. STUDY DESIGN: An implant was placed bilaterally in the maxillary sinus of 8 adult female mongrel dogs in a way that it penetrated the bone and mucous membrane of the maxillary sinus floor to the extent of 2 mm, 4 mm, or 8 mm. The implants were left in place for 6 months. RESULTS: Radiographic and histologic examinations did not show any signs of pathologic findings in the maxillary sinus of the 8 dogs. CONCLUSION: This study indicates that implant protrusion into the maxillary sinus cavity is not related to the development of sinus complications in canines.

A clinical evaluation of titanium miniplates as anchors for orthodontic treatment.

INTRODUCTION: The purpose of this clinical study was to evaluate the stability of titanium miniplates used as anchorage for orthodontic treatment. METHODS: Seventeen patients with a total of 68 miniplates were enrolled. The miniplate placement sites were evenly divided between the maxilla and mandible. The patients underwent distal movements of the molars with miniplate anchorage to correct anterior crossbite or crowding without extracting the premolars. RESULTS: The posttreatment clinical examination showed that 5 miniplates, all in the mandible, failed before the end of treatment-a 7% failure rate. CONCLUSIONS: Further studies, perhaps with titanium miniplates of a different design, might be necessary to identify important factors for decreasing the incidence of complications when miniplates are used for orthodontic anchorage.

The need for intermaxillary fixation in sagittal split osteotomy setbacks with bicortical screw fixation.

OBJECTIVE: The aim of this study was to decide whether use of bicortical screw fixation provides sufficient stability to dispense with intermaxillary fixation (IMF). STUDY DESIGN: Eighty-six patients who had undergone surgical setback of the mandible using bilateral sagittal split ramus osteotomies were examined. Group 1 (15 patients) received miniplate fixation with IMF for 6 weeks, and group 2 (71 patients) received bicortical screw fixation and immediate postoperative function. The 2 groups were evaluated radiographically for postsurgical changes of the pogonion 24 months postoperatively. RESULTS: There was no significant difference in the magnitude of the relapse between the 2 groups over the 24-month postoperative period. CONCLUSION: The use of bicortical screw fixation after sagittal split setback of the mandible provides sufficient stability to dispense with IMF.

Critical size defect in the canine mandible.

OBJECTIVE: The purpose of this study was to determine the minimum size defect in a canine mandible that would not spontaneously heal during the dog's natural life (the critical size defect). STUDY DESIGN: Sixteen adult female mongrel dogs underwent continuity resection on both sides of the mandible to create bilateral defects. In 8 dogs, mandibular defects ranging from 5 to 20 mm were created with periosteal resection. In the other 8 dogs, mandibular defects ranging from 30 to 60 mm were created preserving the periosteum. The dogs were then killed at 6 months and the defects examined using radiographs and histologic analysis. RESULTS: When the periosteum was removed, mandibular defects greater than 15 mm failed to heal across the entire defect. However, when the periosteum was preserved, mandibular defects needed to be greater than 50 mm in order to fail to heal. CONCLUSION: The critical size defect in a canine mandible model is 15 mm when the periosteum is removed and 50 mm when the periosteum is preserved.

Nerve repair using a vein graft filled with collagen gel.

It has been shown that a vein graft provides a good environment for axon regeneration in short nerve gaps. But the use of a vein graft for long nerve gaps is controversial because veins may collapse, due to their thin walls, and the surrounding scar tissue can cause constriction. In an attempt to improve results using the vein graft, the authors conducted the reported experiment by filling the lumen of the vein with collagen gel. A 15-mm rabbit peroneal nerve defect was bridged with a collagen-filled vein graft. On the contralateral side, the defect was bridged with the vein alone. When the regenerated tissue was examined 4 weeks, 8 weeks, and 12 weeks after grafting, the number and diameter of myelinated fibers were significantly increased, compared with the control group without collagen gel. This study found that in order to increase the efficacy of a vein graft for axonal regeneration, collagen gel might be an appropriate matrix material with which to fill the vein graft.

Autologous fibrin glue in peripheral nerve regeneration in vivo.

The activity of several growth factors on peripheral nerve regeneration is reported. Autologous fibrin glue contains a large number of platelets, which release significant quantities of growth factors. In order to understand the role of autologous fibrin glue in peripheral nerve regeneration, a 15-mm rabbit peroneal nerve defect was repaired using a vein graft filled with autologous fibrin glue. Axonal regeneration was examined using histological and electrophysiological methods. The extent of axonal regeneration was superior when treated with autologous fibrin glue. Our data suggest that fibrin nets formed by fibrinogen, in combination with growth factors present in autologous fibrin glue, might effectively promote peripheral nerve regeneration in nerve defects.

Microvascular anastomosis using cyanoacrylate adhesives.

This paper describes a new technique for microvascular anastomosis, which involves the overlapping of the adventitias of the two ends of a severed blood vessel, and then painting a cyanoacrylate adhesive on the outer surface of the vessel around the anastomosed part. Sixteen anastomoses were performed in both radial arteries and cephalic veins in eight dogs. All vessels were patent without thrombus. The described method of anastomosis was faster and easier to perform than the conventional suture anastomosis. Histologic studies revealed that the adhesive did not flow into the lumen, and that normal healing of the endothelium and of the internal elastic lamina occurred across the anastomotic site, even though the adhesive remained on the adventitial side of the vessel at 4 weeks. This technique deserves to be considered as an alternative to conventional suture anastomosis.