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BackgroundVelopharyngeal structure augmentation methods are used as alternatives to pharyngeal flap operations. Recently, we investigated the sites of velopharyngeal structure augmentation in dogs and reported that the most effective injection location is the soft palate. However, there have been no reports regarding the optimal materials for implantation or injection. In this study, we aimed to investigate the injectable materials used in soft palate augmentation in dogs to ameliorate velopharyngeal insufficiency (VPI).MethodsEndoscopic soft palate augmentation (ESPA) was performed in dogs using purified sodium hyaluronate, atelocollagen, or autogenic fat tissue. ESPA is an original technique developed by our group, and this is the first report of its performance. Moreover, we assessed the amount of nasal air leakage during inspiration at rest and during expiration under the rebreathing system at 1, 2, 3, 4, 5, and 6 months after injection of these materials.ResultsThe amount of nasal air leakage during expiration under the rebreathing system was significantly decreased in all dogs injected with the ESPA materials, but neither apnea nor hypopnea was observed.ConclusionsWe investigated the optimal materials for use in ESPA, such as purified sodium hyaluronate, atelocollagen, or autogenic fat tissue. We found that all of them reduced nasal air leakage and only autogenic fat tissue showed significant histologic differences in dogs at 6 months. This technique may also be useful for the treatment of patients with VPI.

BackgroundVelopharyngeal structure augmentation methods are used as alternatives to velopharyngeal plasty. Anatomic sites of implantation/injection vary widely due to a lack of standardized criteria. Here, we experimentally investigated optimal sites of velopharyngeal structure augmentation via saline injection in dogs as they naturally exhibit velopharyngeal insufficiency (VPI).MethodsVelopharyngeal structure augmentation was performed on 10 beagles (age range: 20-24 months; weight range: 9-12 kg). Saline containing 1/80,000 epinephrine was injected intraorally in 1-mL increments into the nasal mucosa of the soft palate (n = 4), posterior pharyngeal wall (n = 3), or bilateral pharyngeal walls (n = 3) of each dog. Nasal air leakage was measured under rebreathing until velopharyngeal closure was achieved; the measurement was performed using flow meter sensors on both nasal apertures, and the oral cavity was filled with alginate impression material to prevent oral air leakage.ResultsPre-injection, the dogs exhibited an average of 0.455 L/s air leakage from the nasal cavity. The dogs with saline injected into the nasal mucosa of the soft palate achieved steady augmentation, and nasal air leakage disappeared under rebreathing following 6-mL saline injection. Conversely, nasal air leakage remained in the dogs with saline injected in the posterior pharyngeal wall or bilateral pharyngeal walls.ConclusionsDuring VPI treatment in dogs, augmentation was most effective at the nasal mucosa of the soft palate. Improvement in nasal air leakage was highly dependent on the saline injection volume. Although velopharyngeal structures vary between dogs and humans, velopharyngeal closure style is similar. Thus, our results may aid in the treatment of VPI patients.

BACKGROUND: Bifocal distraction osteogenesis has been shown to be a reliable method for reconstructing segmental mandibular defects. However, there are few reports regarding the occurrence of inferior alveolar nerve regeneration during the process of distraction. Previously, we reported inferior alveolar nerve regeneration after distraction, and evaluated the regenerated nerve using histological and electrophysiological methods. In the present study, we investigated axons regenerated by bifocal distraction osteogenesis using retrograde transportation of horseradish peroxidase in the mandibles of dogs to determine their type and function. METHODS AND FINDINGS: Using a bifocal distraction osteogenesis method, we produced a 10-mm mandibular defect, including a nerve defect, in 11 dogs and distracted using a transport disk at a rate of 1 mm/day. The regenerated inferior alveolar nerve was evaluated by retrograde transportation of HRP in all dogs at 3 and 6 months after the first operation. At 3 and 6 months, HRP-labeled neurons were observed in the trigeminal ganglion. The number of HRP-labeled neurons in each section increased, while the cell body diameter of HRP-labeled neurons was reduced over time. CONCLUSIONS: We found that the inferior alveolar nerve after bifocal distraction osteogenesis successfully recovered until peripheral tissue began to function. Although our research is still at the stage of animal experiments, it is considered that it will be possible to apply this method in the future to humans who have the mandibular defects.