BACKGROUND: In clinical, the research on the method and the material of the soft tissue defect of the operation area has been in depth. It wil have a positive impact on our exploration and research in this field through the establishment of reliable experimental animal oral soft tissue defect model. OBJECTIVE: To establish a rabbit model of oral soft tissue defects for oral treatment of soft tissue defects in-depth study. METHODS: Eighteen 3-month-old male New Zealand rabbits were enrol ed. A tissue ring cutting dril of 5 mm diameter was used to prepare round ful -thickness soft tissue defects in the front part of the hard palate and, respectively, from the back of the maxil ary incisors, about 2 mm from the hard palate mucosal edge. Morphology and histology were observed at 3, 7, 14, 21, 28 and 56 days after model establishment. RESULTS AND CONCLUSION: (1) Morphological observation: After 3 and 7 days, the wound’s inflammatory reaction was obvious. As the time goes, the inflammatory response subsided, the wound gradual y healed. Scar formation was observed at 21, 28 and 56 days after surgery. (2) Histological observation: 3 and 7 days after injury, many inflammatory cel s were infiltrating, and tissue necrosis area was larger. At 7 days after surgery, with the extensive formation of connective tissue proliferation and new blood capil aries, the wound gradual y shaping completely. (3) Results indicated that a rabbit model of oral soft tissue defects was successful y established, which was in line with the physical laws of wound healing and the characteristics of human oral soft tissue defects healing.

BACKGROUND:Previous studies have found that platelet-rich fibrin has a good ability to induce gingival soft tissue repair and regeneration.
OBJECTIVE:To observe the effects of platelet-rich fibrinversus colagen membrane on gingival soft tissue healing, and to evaluate the ability of platelet-rich fibrin to repair gingival defects.
METHODS:Twenty-two patients (2 premolar teeth and 20 molars) scheduled for premolar or molar removal or ridge preservation due to various reasons were selected and randomized into two groups. Bio-Oss was implanted into the extraction socket folowed by covering with platelet-rich fibrin or colagen membrane. Healing time and healing rate of gingival defects were detected to evaluate the ability of platelet-rich fibrin to promote gingival tissue healing at 1-2 weeks after Bio-Oss implantation.
RESULTS AND CONCLUSION:The healing time was (12.17±2.25) days in the platelet-rich fibrin group and (17.30±2.58) days in the colagen group. The healing rate of the platelet-rich fibrin group was notably higher than that in the colagen membrane group at 1 and 2 weeks after Bio-Oss implantation. These findings indicate that platelet-rich fibrin is better than colagen membrane to improve the healing of gingival soft tissues with a shorter healing time.

BACKGROUND:Insufficient oral soft tissues in the implant zone may have a negative effect on the wound healing and the aesthetic restoration in the late stage. Platelet-rich fibrin can promote the wound healing of soft tissue defects. But there is stil a lack of in-depth studies on the promotion of oral soft tissue defects in animal experiments.
OBJECTIVE: To compare the repairing effects of platelet-rich fibrin and colagen membrane on soft tissue defects of the hard palate in New Zealand rabbits.
METHODS:Fifty-four New Zealand rabbits were randomly divided into three groups (n=14 per group): platelet-rich fibrin group, colagen membrane group and blank control group. A 5 mm-diameter circular ful-thickness soft tissue defect was made in the front of the hard palate, 2 mm distant to the rear maxilary incisors and mucosal edge of the bilateral hard palates. Autologous platelet-rich fibrin membrane or colagen membrane were implanted into the defect in the platelet-rich fibrin group and colagen membrane group, respectively. No treatment was given in the blank control group. General observation of the wound and wound healing analysis were performed at days 3, 7, 14, 21, 28, 56 post operation. Hematoxylin-eosin staining, CD31 immunohistochemical staining and Masson staining were used to observe inflammatory reaction, angiogenesis and colagen formation in the surgical site.
RESULTS AND CONCLUSION:The wound healing rate was fastest in the platelet-rich fibrin group, and no obvious scar formed. At 3 days post operation, there was no difference in the wound healing rates among the three groups; at 7 days, the wound healing rate in the platelet-rich fibrin group was significantly higher than that in the colagen membrane group and blank control group (P < 0.05). At 3 and 7 days after operation, the inflammatory reaction in the platelet-rich fibrin group was less than that in the colagen membrane and blank control groups (P < 0.05); at 14, 21, 28 and 56 days, there was no significant difference between the three groups. At 7, 14, 21 days after operation, the average absorbance value of CD31 in the platelet-rich fibrin group was significantly higher than that in the colagen membrane and blank control groups (P < 0.05). The average absorbance value of colagen formation in the platelet-rich fibrin group was significantly higher than that in the colagen membrane and blank control groups at 7 days after operation (P < 0.05), significantly higher than that in the blank control group at 14 days (P < 0.05), but lower than that in the colagen membrane and blank control groups at 21, 28 and 56 days after operation (P < 0.05). These findings show that platelet-rich fibrin can reduce inflammatory reactions in the process of wound healing, accelerate the angiogenesis, regulate the metabolism of colagen, reduce the formation of scar and improve the quality of wound healing, thereby promoting the repair of oral soft tissue defects.

BACKGROUND:In previous experiments, we have confirmed that platelet rich fibrin has the ability of osteoinduction, and have conducted a preliminary study on its microstructure and biomechanics. However, little is reported on its histology research.
OBJECTIVE:To compare the histological changes after implanting platelet-rich fibrin, Bio-Oss and autologous bone and to analyze the pros and cons of platelet-rich fibrin implantation for repair of bone defects.
METHODS: As previously reported, animal models of critical bone defects were established respectively on the bilateral femoral condyles of 12 beagle dogs. Then, platelet-rich fibrin, Bio-Oss+colagen membrane (Bio-Oss group) and autologous bone (autologous bone group)+colagen membrane were respectively implanted. At 3, 6, 8 and 12 months, one experimental dog from each group was kiled, respectively, and histological observation was performed. Another beagle dog as blank control was enroled to establish the animal model of critical bone defects, with no implantation.
RESULTS AND CONCLUSION:At 3, 6, 8 and 12 months after implantation, there were significant differences in the new bone formation speed and amount between the platelet-rich fibrin group, Bio-Oss group and autologous bone group. These three kinds of bone grafts al had osteoinductive ability to different extents. In the platelet-rich fibrin group, the osteogenic effects were better at 3 and 6 months, and the new bone was similar to natural one; in the autologuos bone group, bone necrosis was noticeable at 3 and 6 months, but the osteogenic effects became better at 8 months, and the new bone was similar to natural one at 12 months; in the Bio-oss group, the osteogenic effects were similar to those in the platelet-rich fibrin group, but the residual of Bio-oss was visible at 12 months; in the blank control group, no bone formed at 3 months, indicating the animal model of critical bone defects was made successfuly. In brief, the platelet-rich fibrin has good osteoinductive ability, with shorter time and better quality.

BACKGROUND:Anterior subtotal corpectomy,decompression and fusion is a conventional method to treat cervical degenerative diseases.A titanium cage is an important implant to maintain the stability of the cervical spine after subtotal corpectomy.In recent years,many patients have complications such as titanium cage sinking,which are highly controversial. OBJECTIVE:To investigate the internal biomechanical relationship between the tilt angle of the titanium cage and postoperative titanium cage subsidence after anterior subtotal cervical corpectomy,decompression and fusion. METHODS:A three-dimensional finite element model of the C4-C6 segment was established by CT images of a normal human cervical spine,in which the anterior subtotal resection,decompression and fusion of the C5 vertebral body were simulated,and titanium cages with different tilt angles(-6° to-1° negative angle,that is,the front edge of titanium cage is shorter than the rear edge of titanium cage;1° to 6° positive angle,that is,the front edge of titanium cage is longer than the rear edge of titanium cage)were placed.After setting the boundary conditions,preloads of 50,100 and 150 N were applied respectively on the C4 vertebral body.The stress value of each contact point between the titanium cage and C4 lower-end plate and C6 lower-end plate(seven stress contact points on the contact surface of titanium mesh)was recorded and statistical analysis was conducted. RESULTS AND CONCLUSION:(1)The tilt angles of the titanium cage of the positive angle group and negative angle group under 50,100 and 150 N stress respectively were found by Mann Whitn test,with P<0.05,which was statistically significant.The dispersion coefficients of the positive angle group were smaller than those of the negative angle group under 50,100 and 150 N stress conditions.(2)Under 50,100 and 150 N stress conditions,the Wilcoxon sign rank test in the positive angle group of titanium cage tilt angle found that when the angle was set to 1° to 5°,the difference was not statistically significant(P>0.05).However,when the tilt angle of the titanium cage was set to 6°,the difference was statistically significant(P<0.05).(3)Under 50,100 and 150 N stress conditions,the Wilcoxon sign rank test in the negative angle group of titanium cage tilt angle found that when the tilt angle was set to-1° to-6°,the difference was not statistically significant(P>0.05).(4)It is concluded that in the sagittal position,the titanium cage with a positive tilt angle is more stable than with a negative tilt angle,which is more suitable for clinical use.The tilt angle of the titanium cage is relatively stable in the range of 1° to 5°.When the tilt angle is 6°,the stability starts to decline,which is easy to cause complications of titanium cage sinking after surgery.It is more suitable to select the titanium cage with a tilt angle of 1° to 5° according to the clinical situation during surgery to improve the efficacy.