Faculty Bibliography

Introduction: Bioengineering osseous tissue requires recapitulating the cellular, matrix, and lacunocanalicular components of bone. A construct must have a microvascular network which requires simultaneous co-culture of endothelial and osteogenic cells. Recreation of the matrix requires optimization of composition and microarchitecture. Engineering of constructs large enough to solve actual clinical problems requires novel strategies that address chemotransportative requirements by replicating lacunocanalicular flow. Methods: Cells: Adipose-derived mesenchymal stem cells (MSCs) were isolated and expanded from human lipoaspirate and differentiated into osteoprogenitor-rich (OPC) and endothelioprogenitor-rich (EPC), confirmed by RT-PCR. Normal human osteoblasts (NHOst) and human umbilical vein endothelial cells (HUVEC) served as terminally differentiated cell lines. The effects of coculture (e.g OPC + HUVEC, OPC + EPC etc) on capacity for bone formation was evaluated by von Kossa assay. Matrix: Murine alveolar defects were created. Scaffolds composed of either absorbable collagen sponge (ACS) or biphasic hydroxyapatite/tri-calcium phosphate (HA-TCP) in a 15/85 ratio were constructed and implanted. HA-TCP scaffolds were further investigated, comparing 15/85 and 60/40 HA/TCP in a rabbit calvarial model. Scaffold pore size (380/180 microns) and strut size (250/180 microns) were also investigated. New bone formation was analyzed histomorphometrically using micro-CT. Lacunocanalicular flow: We have developed a novel flow perfusion bioreactor designed to mimic lacunocanalicular flow. To validate, murine femurs were explanted to the bioreactor for 14 days. Viability and function were evaluated using thiazolyl blue tetrazolium bromide (MTT), DNA quantification, alkaline phosphatase (ALP) assay, and tetracycline labelling. Furthermore, optimal culture conditions were tested with MSC-seeded custom thick 3D HA-TCP scaffolds cultured in static conditions or in flow perfusion. Cellularity was assessed by SEM,!

BACKGROUND: Mandibular distraction has evolved from the use of external to the use of intraoral and semiburied devices. The authors highlight the evolution of the semiburied technique. The authors evaluate advantages and limitations, and report perioperative events for external and semiburied techniques to establish the indications for selection of the different devices. METHODS: A retrospective review was conducted of patients undergoing mandibular distraction at the New York University Langone Medical Center from the authors' introduction of mandibular distraction in May of 1989 to June 30, 2009. Perioperative events were stratified into three groups: minor incidents, moderate incidents, and major incidents. RESULTS: A total of 211 mandibular distraction procedures were performed: 129 external procedures on native bone, 37 external procedures on grafted bone, and 45 semiburied procedures on native bone. Minor incidents were more common with the semiburied device (62 percent) compared with external devices on native (26 percent) and grafted (38 percent) bone. There were fewer moderate incidents with the semiburied device (18 percent) than with the external device on native (22 percent) and grafted (30 percent) bone. In contrast to the external technique, no major incidents were seen with semiburied distraction. CONCLUSIONS: The semiburied device reduces scarring and has the mechanical advantages of being applied directly to the bone, less vulnerable to dislodgment, and more favorable for a vertical vector. However, its use requires more bone stock and it has the disadvantage of requiring a second operation for removal. Semiburied distraction is safe, reliable, and indicated for lengthening of the hypoplastic mandible where there is adequate bone stock for its attachment