title: Minimally traumatic alveolar ridge augmentation with a tunnel injectable thermo-sensitive alginate scaffold.
abstract: Injectable bone substitutes and techniques have been developed for use in minimally invasive procedures for bone augmentation.
  
  
  OBJECTIVE
  To develop a novel injectable thermo-sensitive alginate hydrogel (TSAH) as a scaffold to induce bone regeneration, using a minimally invasive tunnelling technique.
  
  
  METHODS
  An injectable TSAH was prepared from a copolymer solution of 8.0 wt% Poly(N-isopropylacrylamide) (PNIPAAm) and 8.0 wt% AAlg-g-PNIPAAm. In vitro properties of the material, such as its microstructure and the sustained release of recombinant human bone morphogenetic protein-2 (rhBMP-2), were investigated. Then, with the subperiosteal tunnelling technique, this material, carrying rhBMP-2, was injected under the labial periosteum of the maxillary anterior alveolar ridge in a rabbit model. New bone formation was evaluated by means of X-ray, micro-computed tomography (micro-CT), fluorescence labelling, histological study, and immunohistochemistry study.
  
  
  RESULTS
  The material exhibited good injectability and thermo-irreversible properties. SEM showed an interconnected porous microstructure of the TSAH. The result of ALP activity indicated sustained delivery of BMP-2 from the TSAH from days 3 to 15. In a rabbit model, both TSAH and TSAH/rhBMP-2 induced alveolar ridge augmentation. The percentage of mineralised tissue in the TSAH/rhBMP-2 group (41.6 ± 3.79%) was significantly higher than in the TSAH group (31.3 ± 7.21%; p < 0.05). The density of the regenerating tissue was higher in the TSAH/rhBMP-2 group than in the other groups (TSAH group, positive control, blank control; p < 0.05).
  
  
  CONCLUSIONS
  The TSAH provided convenient handling properties for clinical application. To some extent, TSAH could induce ridge augmentation and mineral deposition, which can be enhanced when combined with rhBMP-2 for a minimally invasive tunnelling injection.
authors.affiliation: Department of Prosthodontics, Hospital of Stomatology, Peking University School, Beijing, China.
authors.forename: Yifen
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Prosthodontics, Hospital of Stomatology, Peking University School, Beijing, China.
authors.forename: Xiaoqian
authors.initials: X
authors.lastname: Fang
authors.affiliation: Department of Prosthodontics, Hospital of Stomatology, Peking University School, Beijing, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Jiang
mesh_terms: D000464:Alginates / Q000008:administration & dosage*; D000539:Alveolar Process / Q000000981:diagnostic imaging / Q000187:drug effects / Q000601:surgery*; D000540:Alveolar Ridge Augmentation / Q000379:methods*; D000818:Animals; D001672:Biocompatible Materials / Q000008:administration & dosage; D015519:Bone Density / Q000187:drug effects; D055396:Bone Morphogenetic Protein 2 / Q000008:administration & dosage; D001861:Bone Regeneration / Q000187:drug effects*; D018786:Bone Substitutes / Q000008:administration & dosage*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000008:administration & dosage*; D007150:Immunohistochemistry; D007267:Injections / Q000379:methods; D008297:Male; D008855:Microscopy, Electron, Scanning; D019060:Minimally Invasive Surgical Procedures / Q000379:methods; D023421:Models, Animal; D015675:Osteocalcin / Q000032:analysis; D053495:Osteopontin / Q000032:analysis; D011817:Rabbits; D011897:Random Allocation; D011994:Recombinant Proteins / Q000008:administration & dosage; D015203:Reproducibility of Results; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000008:administration & dosage; D016896:Treatment Outcome; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D000464:Alginates; D001672:Biocompatible Materials; D055396:Bone Morphogenetic Protein 2; D018786:Bone Substitutes; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D015675:Osteocalcin; D053495:Osteopontin; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate