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BACKGROUND: Several sinus floor elevation procedures for implant placement have been introduced. The present study aimed to evaluate the implants placed with Platelet-rich fibrin (PRF) alone in atrophic posterior maxillae and survival rates and the potential factors associated with implant loss. MATERIAL AND METHODS: This retrospective study evaluated 71 implants in 34 patients after 1-7 years' follow-up time. Statistical models were used to determine the implant survival and the potential factors associated with loss. RESULTS: Overall, 7 implants were lost, and the cumulative survival rate at 7 years by implant-based and patient-bases analyses were 85.5% and 85.7%, respectively. The mean residual bone height (RBH) was 4.26 mm. The implant survival rate was significantly lower at RBH < 4 mm than RBH ≥ 4 mm. CONCLUSIONS: This retrospective study showed that sinus floor elevation with PRF alone could be applied in cases of lower RBH. However, it should be carefully performed in cases of RBH < 4 mm before surgery. Key words:Platelet-rich fibrin, dental implant, sinus augmentation, retrospective study.

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OBJECTIVE: Few studies evaluate condylar movement following mandibular reconstruction. The main objective of this study was to show that axial four-dimensional computed tomography (4DCT) could visualize bilateral protrusive condylar movement directly. We used axial 4DCT images to assess condylar protrusion in patients who underwent mandibular reconstruction. METHODS: We enrolled seven healthy volunteers (median age 30 years, range 27-38 years) and seven patients (median age 65 years, range 52-80 years), who underwent mandibulectomy (segmental in five, hemi in one, marginal in one) and free flap reconstruction (using the fibula in six and the radial forearm in one). Six study subjects were instructed to masticate a cookie during the 4DCT scan (the seventh made chewing motions). The distance between the most anterior and posterior positions of the bilateral condyles on 4DCT (axial view) images was then measured and compared between controls and patients using the Mann-Whitney U-test. RESULTS: The crosswise difference in the distances of condylar protrusion was significantly greater in patients than in the controls. CONCLUSION: Axial 4DCT images can visualize a bilateral condylar protrusive path. Axial 4DCT images for patients who have undergone mandibulectomy and reconstruction may be useful for evaluation of functional movement of condyles.

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The purpose of this study was to retrospectively investigate the multivariate relationships between specific risk factors and postoperative hemorrhage after tooth extraction in patients who were prescribed oral antithrombotic therapy. Risk factors for postoperative hemorrhage after tooth extraction were evaluated using univariate and multivariate analyses. Patient characteristics such as age and gender; the presence or absence of known comorbidities such as diabetes mellitus, hypertension, cerebral infarction, and alcohol consumption; and perioperative diarrhea were assessed. The drug used for antithrombotic therapy, preoperative blood test results, the presence or absence of preoperative antibiotics or nonsteroidal anti-inflammatory drug (NSAID) administration, the total number of extracted teeth, and the type of surgical procedures were also evaluated. We found that the preoperative administration of antibiotics (odds ratio (OR) = 2.52), an increased prothrombin time international normalized ratio (PT-INR) value (OR = 1.94), and the extraction of multiple teeth (OR = 2.10) were significantly associated with postoperative hemorrhage. There was no significant association between postoperative hemorrhage and any other demographic factors or comorbidities, including concomitant alcohol use. We demonstrated the multivariate relationship between the risk factors and postoperative hemorrhage after tooth extraction in patients receiving oral antithrombotic therapy. Surgeons should be aware of these risks and monitor the PT-INR of anticoagulated patients.

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In sinus floor augmentation of an atrophic posterior maxilla, platelet-rich fibrin (PRF) has been used as a graft material. We herein report two cases with histological evaluations of PRF after the surgery. The first case was a 28-year-old female with an atrophic right posterior maxilla who was treated with sinus floor augmentation and simultaneous implant placement using PRF as the sole graft material in our hospital. Twenty-four months after surgery, the implant was unfortunately removed because of occlusal overloading by parafunctional habits. During implant replacement, a tissue sample was obtained from the site of augmentation with PRF and was evaluated histologically. The second case was a 58-year-old man with severe alveolar atrophy of the right maxilla who underwent lateral sinus augmentation using only PRF in a two-stage procedure in our hospital. Samples were obtained at the second-stage surgery and histological examinations were performed. As a result, new bone formation was confirmed histologically in both cases. Our findings show that the use of PRF as a graft material during sinus floor augmentation induces natural bone regeneration.