Venous anastomoses using microvascular coupler in free flap head and neck reconstruction.

PURPOSE: This study is a retrospective review of the experience using the venous coupler for head and neck reconstruction over a 3-year period at the University of Maryland Medical Center, Department of Oral and Maxillofacial Surgery. MATERIALS AND METHODS: One hundred seventy-eight consecutive cases of microvascular free flaps between May 2007 and September 2010 were retrospectively reviewed. Data were collected by demographic information, flap type, recipient vessels, method of anastomosis, coupler size, coupler orientation, complications associated with coupler, and reconstruction results. Fisher exact test was used for statistical analysis. RESULTS: There were 294 anastomotic coupler devices used in 173 flaps, with hand-sewn venous anastomoses performed in 5 patients. The overall flap success rate was 94.9% (169/178). Success rate among cases in which the coupler was used was 95.4% (8/173). Total coupler venous thrombosis rate was 4.0% (7/173), with a statistically significant difference (P < .05) in reference to the number of venous anastomoses performed: 58 cases had a single vein anastomosed, 5 cases developed thrombosis; while the 115 flaps with 2 venous anastomoses, only 2 cases had thrombosis. CONCLUSIONS: The microvascular coupler is reliable for venous anastomosis in free flap head and neck reconstruction; dual-vein anastomoses appear to have better results than single-vein anastomoses. Flow coupler has a promising utility in monitoring buried flaps and flaps that are difficult to observe. The microvascular coupler deserves to be more commonly used in free flap head and neck reconstruction.

Challenges associated with regeneration of orbital floor bone.

Orbital floor fractures are a serious consequence of craniofacial trauma and account for ∼60%-70% of all orbital fractures. Unfortunately, the body's natural response to orbital floor defects generally may not restore proper function and facial aesthetics, which is complicated by the thin bone and adjacent sinuses. Current clinical treatments include alloplastic implants and autologous grafts; however, each has associated disadvantages and sequelae. This review has outlined necessary components for a successful tissue-engineered construct for orbital floor repair. In addition, current successes and progress in the literature specific to orbital floors and craniofacial research have been reviewed. Finally, challenges and future directions have been described.

Macroporous hydrogels upregulate osteogenic signal expression and promote bone regeneration.

The objective of this work was to investigate the effects of macroporous hydrogel architecture on the osteogenic signal expression and differentiation of human mesenchymal stem cells (hMSCs). In particular, we have proposed a tissue engineering approach for orbital bone repair based on a cyclic acetal biomaterial formed from 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD) and poly(ethylene glycol) diacrylate (PEGDA). The EHD monomer and PEGDA polymer may be fabricated into macroporous EH-PEG hydrogels by radical polymerization and subsequent porogen leaching, a novel technique for hydrophilic gels. We hypothesized that EH-PEG hydrogel macroporosity facilitates intercellular signaling among hMSCs. To investigate this phenomenon, hMSCs were loaded into EH-PEG hydrogels with varying pore size and porosity. The viability of hMSCs, the expression of bone morphogenetic protein-2 (BMP-2), BMP receptor type 1A, and BMP receptor type 2 by hMSCs, and the differentiation of hMSCs were then assessed. Results demonstrate that macroporous EH-PEG hydrogels support hMSCs and that this macroporous environment promotes a dramatic increase in BMP-2 expression by hMSCs. This upregulation of BMP-2 expression is associated by a more rapid hMSC differentiation, as measured by alkaline phosphatase expression. Altering hMSC interactions with the EH-PEG hydrogel surface, by the addition of fibronectin, did not appear to augment BMP-2 expression. We therefore speculate that EH-PEG hydrogel macroporosity facilitates autocrine and paracrine signaling by localizing endogenously expressed factors within the hydrogel's pores and thus promotes hMSC osteoblastic differentiation and bone regeneration.

Characterization of cyclic acetal hydroxyapatite nanocomposites for craniofacial tissue engineering.

Cyclic acetal hydrogels are a novel group of biomaterials which may facilitate osteogenic differentiation of encapsulated bone marrow stromal cells (BMSCs) because of their neutral degradation products. Here, we have incorporated hydroxyapatite nanoparticles within cyclic acetal hydrogels to create cyclic acetal nanocomposites for craniofacial tissue engineering applications. We hypothesized that inclusion of nanosized hydroxyapatite particles within cyclic acetal hydrogels would upregulate osteogenic signal expression of encapsulated BMSCs, due to enhanced cell adhesion, and therefore promote osteodifferentiation. Experimental nanocomposite groups consisted of lower (5 ng/mL) and higher (50 ng/mL) concentrations of nanoparticles. The nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. Swelling parameters of hydrogels in the presence of nanoparticles was studied. Osteoblastic differentiation was characterized by alkaline phosphatase (ALP) and osteocalcin (OC) expression, whereas endogenous osteogenic signal expression was characterized by morphogenetic protein-2 (BMP-2) expression. Finally, immunohistochemistry was performed to detect the presence of OC at the protein level. Results indicated that hydroxyapatite nanoparticles were uniformly distributed throughout the hydrogels and did not affect material properties of the gels. Viability of cells was not affected by nanoparticle concentration, and BMP-2 and OC mRNA expression was enhanced in the presence of nanoparticles. However, a difference in BMP-2, ALP, and OC mRNA expression was not noted between the lower and higher concentrations of nanoparticles. This work demonstrates that inclusion of hydroxyapatite nanoparticles within a cyclic acetal nanocomposite hydrogel may enhance BMSC differentiation by promoting endogenous osteogenic signal expression.

Cyclic acetal hydroxyapatite nanocomposites for orbital bone regeneration.

We have incorporated hydroxyapatite nanoparticles within cyclic acetal hydrogels to create nanocomposites that can be used to repair surgically created orbital floor defects in a rabbit animal model. Nanosized hydroxyapatite particles may improve tissue engineering scaffold properties because they have similar length scale of many cellular and molecular components and therefore can enhance cellular adhesion and migration. We hypothesize that inclusion of nanosized hydroxyapatite particles (20-70 nm) within cyclic acetal hydrogels would support bone defect repair. The objectives of our study include (1) characterization of nanocomposites in vitro, (2) investigation of tissue response and capsule tissue surrounding nanocomposites in vivo, and (3) investigation of the potential of nanocomposites to facilitate bone formation at 7- and 28-day time points in vivo. Experimental nanocomposite groups consisted of 0, 10, and 50 ng/mL nanosized hydroxyapatite. In vitro results indicated uniform dispersion of nanoparticles within nanocomposites and increased compressive moduli of nanocomposites with increase in nanoparticle concentration and bone marrow stromal cell viability within nanocomposites. In vivo results at day 7 indicated a tissue response of mild to increased inflammatory cells and presence of immature fibrous tissue. At day 28, tissue response consisted of mild inflammatory response and mature tissue. Quantitative results at day 7 indicated no difference in total bone percentage area between groups. The results also indicated that the tissue capsule surrounding the 0, 10, and 50 ng group implants had no clear organization. Quantitative results at day 28 indicated that the tissue capsule surrounding the 0, 10, and 50 ng group implants was an organized layer and the bone percentage for the 50 ng group was significantly higher than that of the remaining groups. Initial results indicated that our nanocomposites initiate a positive in vivo response in terms of bone growth. However, the percentage of bone area compared with the total area was low at both time points. Thus, in our study, even after addition of nanoparticles to cyclic acetal hydrogels, their biocompatible properties were maintained. On the other hand, addition of nanoparticles to cyclic acetal hydrogels did not lead to complete restoration of orbital floor defects.

Tissue response and orbital floor regeneration using cyclic acetal hydrogels.

Orbital floor injuries are a common form of traumatic craniofacial injury that may not heal properly through the body's endogenous response. Reconstruction is often necessary, and an optimal method does not exist. We propose a tissue engineering approach for orbital bone repair based upon a cyclic acetal biomaterial formed from 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD) and poly(ethylene glycol) diacrylate (PEGDA). The EHD monomer and PEGDA polymer may be fabricated into an EH-PEG hydrogel by radical polymerization. The objectives of this work were to study (1) the tissue response to EH-PEG hydrogels in an orbital bone defect and (2) the induction of bone formation by delivery of bone morphogenetic protein-2 (BMP-2) from EH-PEG hydrogels. EH-PEG hydrogels were fabricated and implanted into an 8-mm rabbit orbital floor defect. Experimental groups included unloaded EH-PEG hydrogels, and EH-PEG hydrogels containing 0.25 microg and 2.5 microg BMP-2/implant. Results demonstrated that the unloaded hydrogel was initially bordered by a fibrin clot and then by fibrous encapsulation. BMP-2 loaded EH-PEG hydrogels, independent of concentration, were surrounded by fibroblasts at both time points. Histological analysis also demonstrated that significant bone growth was present at the 2.5 microg BMP-2/implant group at 28 days. This work demonstrates that the EH-PEG construct is a viable option for use and delivery of BMP-2 in vivo.

Deep neck infections: clinical considerations in aggressive disease.

Deep neck infections are common and occur as a consequence of several etiologies. Antibiotic therapy, interventional radiology, and patient support modalities have become increasingly sophisticated, although surgery continues to be the mainstay of treatment for most patients. Today, neck infections are rarely life threatening when sound and timely management is applied.

Bisphosphonate related osteonecrosis of the palate: report of a case managed with free tissue transfer.

The management of patients with established bisphosphonate-related osteonecrosis of the jaws (BRONJ) remains unclear. The patient discussed here presented with spontaneous BRONJ of the palate after taking an oral bisphosphonate for osteoporosis. Conservative management resulted in progression of the osteonecrosis. Surgical debridement and immediate reconstruction with free tissue transfer was undertaken and resulted in complete resolution of her condition. The case is presented here.

Cyclic acetal hydrogel system for bone marrow stromal cell encapsulation and osteodifferentiation.

Many systems have been proposed for the encapsulation of bone marrow stromal cells (BMSCs) within degradable hydrogels. Here, we use a novel cyclic acetal-based biomaterial formed from 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD) and poly(ethylene glycol) diacrylate (PEGDA). A cyclic acetal-based hydrogel may be preferred as cyclic acetals hydrolytically degraded into diols and carbonyls as primary degradation products, which may not affect local acidity, unlike other widely investigated polymers. The EHD monomer and PEGDA polymer may be fabricated into a EH-PEG hydrogel by radical polymerization initiated by the ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED) system. The objective of this work is to determine whether the components utilized in the fabrication of EH-PEG hydrogels as well as the EH-PEG hydrogels permit BMSC viability, metabolic activity, and osteodifferentiation. Cell viability and metabolic activity were assessed after 30 min, 1 h, and 3 h of exposure to pertinent concentrations of the initiator system (10-20 mM). Osteodifferentiation was assessed by alkaline phosphatase and osteocalcin expression after a short exposure to the initiator system to simulate the encapsulation process. Lastly, cell viability was assessed immediately after encapsulation and after 7 days of culture within the EH-PEG hydrogels. Results indicate that the metabolic activity and viability of BMSCs are minimally affected, and that osteodifferentiation is not significantly affected by the APS-TEMED initiator system. Also, encapsulated BMSCs maintained viability within EH-PEG hydrogels for 7 days. This work demonstrates that the EH-PEG hydrogel is a viable option for the encapsulation and osteodifferentiation of BMSCs.

Application of intermaxillary fixation screws in maxillofacial trauma.

PURPOSE: The use of intermaxillary fixation (IMF) in the treatment of maxillofacial trauma represents the cornerstone of fracture reduction and immobilization. Many modalities of IMF have been described; recently IMF screws have been introduced into clinical practice, however, hardware failure can occur. We performed a retrospective study evaluating hardware-associated complications for self-drilling/tapping IMF screws. MATERIALS AND METHODS: A retrospective study on 49 patients requiring IMF was performed. The diagnosis, duration of IMF, screw site, use of elastic or wire fixation, and associated complications were recorded. IMF screws were used to adjunct open reduction techniques, for definitive closed reduction, or fracture prevention following dentoalveolar surgery. Follow-up examinations were performed until fracture healing was complete (6 to 8 weeks). RESULTS: A single adverse event occurred in 19 patients (39%) while 4 patients (8%) had more than 1 complication. The most common event was screw loosening; 29% of patients had at least 1 screw dislodged in the treatment period. Of the total number of screws placed (229), 15 (6.5%) became loose, and were equally distributed among the mandible and maxilla. The remaining complications noted were root fracture, 4% (2 of 49); loosened wires, 6% (3 of 49); screw shear, 2% (1 of 49); malocclusion, 2% (1 of 49); and ingested hardware, 2% (1 of 49). CONCLUSIONS: Overall the IMF self-drilling/tapping screws have been shown to be a useful modality to establish maxillomandibular fixation. It is a safe, and time-sparing technique; however, it is not without limitations or potential consequences which the surgeon must be aware of in order to provide safe and effective treatment.

Management of the dental patient with renal disease.

The kidneys are essential organs responsible for a multitude of bodily functions. One of the most important roles involves the regulations of intravascular volume and concentration of fluids in the body by producing urine. In addition, the kidneys are involved in regulation of blood pressure, detoxification of harmful substances, secretion of hormones, the control of acid/base balance and concentration of several electrolytes, and many other functions. This article provides the dental practitioner with a review of the renal system, associated pathology, and how one must alter their management to provide effective and safe treatment.

Primary intraosseous odontogenic carcinoma arising in an odontogenic cyst or de novo: a clinicopathologic study of six new cases.

The term primary intraosseous odontogenic carcinoma (PIOC) has been primarily used to describe a squamous cell carcinoma within the jaws arising either from a previous odontogenic cyst or de novo. Here, we report 6 new cases of PIOC, affecting 4 female and 2 male patients with a mean age of 56.2 years. Two cases involved the maxilla and 4 cases occurred in the mandible. The typical radiographic presentation was that of a radiolucent lesion with well or ill defined margins. Histopathologically, 4 cases were diagnosed as well differentiated keratinizing PIOC arising from previous odontogenic cysts (2 odontogenic keratocysts and 2 periapical cysts). The remaining 2 cases were poorly differentiated nonkeratinizing PIOC, which appeared to arise de novo. Treatment consisted of surgical removal, with postoperative radiotherapy in 5 cases, and to date neither recurrence nor metastasis have occurred. Knowledge of the clinical, radiographic, and histopathologic features of PIOC allows accurate diagnosis and appropriate treatment of this rare malignancy.