Faculty Bibliography

BACKGROUND: Although different cranioplasty storage methods are currently in use, no study has prospectively compared these methods. The authors compare freezing and subcutaneous storage methods in a rat model. METHODS: Trephine defects (10 mm) were created in 45 Sprague-Dawley rats. The cranial bone grafts were stored in an autologous subcutaneous pocket (n = 15), frozen at -80 degrees C (n = 15), immediately analyzed (n = 12), or immediately replanted into the defect (n = 3). After 10 days of storage, the subcutaneous or frozen grafts were either replanted (subcutaneous, n = 3; frozen, n = 3) or analyzed (subcutaneous, n = 12; frozen, n = 12). Grafts underwent histologic analysis, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, alkaline phosphatase assay, mechanical testing, and micro-computed tomographic imaging. RESULTS: After 10 days of storage, physiologic assays demonstrated a significant decrease in cellular functionality (e.g., alkaline phosphatase assay concentration: fresh, 18.8 +/- 0.77 mM/mg; subcutaneous, 12.2 +/- 0.63 mM/mg; frozen, 8.07 +/- 1.1 mM/mg; p < 0.012 for all comparisons). Mechanical integrity (maximal load) of fresh grafts was greatest (fresh, 9.26 +/- 0.29 N; subcutaneous, 6.27 +/- 0.64 N; frozen, 4.65 +/- 0.29 N; fresh compared with frozen, p < 0.001; fresh compared with subcutaneous, p = 0.006). Replantation of subcutaneously stored and frozen grafts resulted in limited bony union and considerable resorption after 12 weeks; in contrast, replanted fresh grafts demonstrated bony union and little resorption. CONCLUSIONS: Current preservation methods for interval cranioplasty do not maintain bone graft viability. Subcutaneous storage appears to provide a small advantage compared with freezing.

Deep bone defects are caused by the progression of periodontal disease, which breaks down bone and connective tissue that hold teeth in place. In this case, a 37-year-old male patient presented a deep bone defect with advanced periodontal disease around an upper canine. Medical-grade calcium sulfate was mixed with demineralized freeze-dried bone allograft and used to repair and regenerate the defect. Analysis of the radiographs at the 5-month time point showed the bone had completely regenerated.

INTRODUCTION/BACKGROUND:Solubility of root filling materials is heavily influenced by the environment they are in contact with. This study compared the solubility of ProRoot MTA in deionized water and synthetic tissue fluid. MATERIALS AND METHODS/METHODS:Forty specimens of prepared MTA were immersed in deionized water and synthetic tissue fluid (20 samples each). The solubility was assessed after 7 and 28 days. Scanning electron microscope observation was also performed. The mean weight loss was evaluated using a digital scale. Data were analyzed using one-way ANOVA. Tukey test was performed for multiple comparisons. RESULTS:MTA solubility in synthetic tissue fluid was significantly lower than deionized water after 7 and 28 days (P<0.05). Secondary electron detectors revealed the presence of lumps and platelets on the surfaces of both specimens. Also, more voids were observed in specimen stored in deionized water. CONCLUSION/CONCLUSIONS:MTA dissolved faster in deionized water than synthetic tissue fluid. Despite this, the solubility of this material in both media was acceptable.

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: Primary alveolar cleft repair has a 41 to 73 percent success rate. Patients with persistent alveolar defects require secondary bone grafting. The authors investigated scaffold-based therapies designed to augment the success of alveolar repair. METHODS: Critical-size, 7 x 4 x 3-mm alveolar defects were created surgically in 60 Sprague-Dawley rats. Four scaffold treatment arms were tested: absorbable collagen sponge, absorbable collagen sponge plus recombinant human bone morphogenetic protein-2 (rhBMP-2), hydroxyapatite-tricalcium phosphate, hydroxyapatite-tricalcium phosphate plus rhBMP-2, and no scaffold. New bone formation was assessed radiomorphometrically and histomorphometrically at 4, 8, and 12 weeks. RESULTS: Radiomorphometrically, untreated animals formed 43 +/- 6 percent, 53 +/- 8 percent, and 48 +/- 3 percent new bone at 4, 8, and 12 weeks, respectively. Animals treated with absorbable collagen sponge formed 50 +/- 6 percent, 79 +/- 9 percent, and 69 +/- 7 percent new bone, respectively. Absorbable collagen sponge plus rhBMP-2-treated animals formed 49 +/- 2 percent, 71 +/- 6 percent, and 66 +/- 7 percent new bone, respectively. Hydroxyapatite-tricalcium phosphate treatment stimulated 69 +/- 12 percent, 86 +/- 3 percent (p < 0.05), and 87 +/- 14 percent new bone, respectively. Histomorphometry demonstrated an increase in bone formation in animals treated with hydroxyapatite-tricalcium phosphate plus rhBMP-2 (p < 0.05; 4 weeks) compared with empty scaffold. CONCLUSIONS: Radiomorphometrically, absorbable collagen sponge and hydroxyapatite-tricalcium phosphate scaffolds induced more bone formation than untreated controls. The rhBMP-2 added a small but significant histomorphometric osteogenic advantage to the hydroxyapatite-tricalcium phosphate scaffold.

Here we present a case of successful non-operative management of an iatrogenic recto-urethral fistula in a 13-year-old boy. The fistula was created when urethroscopic repair of a urethral stricture was attempted. Due to the anatomy of the lesion and previous urinary diversion, it was deemed possible to spare this patient diverting colostomy or surgical repair of the fistula. The result was successful closure of the fistula, which was confirmed on retrograde urethrogram. While we do not support the routine use of non-operative management for recto-urethral fistulas we have demonstrated that there are circumstances where it can be safely applied

BACKGROUND: Despite technical advancement, treatment of congenital alveolar clefts has remained controversial. Currently, primary alveolar cleft repair (i.e., gingivoperiosteoplasty) has a 41 to 73 percent success rate. However, the remaining patients have persistent alveolar bone defects requiring secondary grafting procedures. Morbidity of secondary procedures includes pain, graft resorption, extrusion or infection, and graft or tooth loss. The authors present a novel rat alveolar defect model designed to facilitate investigation of therapeutics aimed at improving bone formation following primary alveolar cleft repair in humans. METHODS: Sixteen 8-week-old Sprague-Dawley rats underwent creation of a 7 x 4 x 3-mm complete alveolar defect from the maxillary incisors to the zygomatic arch. Four animals were humanely killed at each of the following time points: 0, 4, 8, and 12 weeks. Morphometric analysis of the alveolar defect was determined by means of micro-computed tomography and histology. RESULTS: Micro-computed tomography demonstrated that new bone filled 43 +/- 5.6 percent of the alveolar defect at 4 weeks, 53 +/- 8.3 percent at 8 weeks, and 48 +/- 3.5 percent at 12 weeks. Histologically, at 4 weeks, proliferating fibroblasts and polymorphonuclear cells were scattered throughout the disorganized collagen in the intercalary gap. By 8 weeks, nascent woven bone spicules extended from the edges of the defect. At 12 weeks, the woven spicules had remodeled, with scant additional bone deposition. CONCLUSION: This model creates a critical-size alveolar defect that is similar in size and location to human alveolar defects and is suitable for studying proposed therapeutics.