Eric C. Sung

The effect of chitosan (poly-N-acetyl glucosamine) on lingual hemostasis in heparinized rabbits☆

PURPOSE The purpose of this study was to evaluate the effect of chitosan on lingual hemostasis in rabbits whose coagulation pathway had been impaired by administration of intravenous heparin. MATERIALS AND METHODS Bleeding times were measured for bilateral (15 mm x 2 mm) tongue incisions in 10 New Zealand white rabbits. Using a randomized, blinded experimental design, one incision in each animal was treated with chitosan, and the other was treated with the control vehicle without chitosan. Activated coagulation times and extraoral bleeding times were measured for each animal before, during, and after heparinization. RESULTS Intravenous infusion of heparin more than tripled the mean activated coagulation time and increased mean systemic bleeding time by 40%. In this heparinized animal model, lingual incisions receiving the experimental substance showed a 43% improvement in bleeding time as compared with lingual incisions receiving the control solution (P< or =.001). Chitosan treatment brought bleeding time of the lingual incision for heparinized animals within the normal range. Scanning electron microscopic evaluation of the incisions treated with chitosan showed an altered red blood cell morphology and an unusual affinity between erythrocytes. CONCLUSIONS Topical application of chitosan to lingual incisions effectively decreased intraoral bleeding time in a therapeutically anticoagulated (heparinized) rabbit model. Chitosan facilitated lingual hemostasis, possibly through interaction with erythrocytes, linking them together to establish a cellular clot or hemostatic plug.

Effect of carbamide peroxide bleaching on the shear bond strength of composite to dental bonding agent enhanced enamel

STATEMENT OF PROBLEM Carbamide peroxide bleaching has been implicated in adversely affecting the bond strength of composite to enamel. PURPOSE This in vitro study evaluated the effect of 3 dental bonding agents (OptiBond, All-Bond 2, One-Step) on the shear bond strength of a hybrid composite to enamel which was treated by a 10% carbamide peroxide bleaching system. MATERIAL AND METHODS Cylinders of composite were bonded to carbamide peroxide-treated enamel on extracted human teeth using 3 dental bonding agents. After thermocycling, shear bond strengths were determined with a universal testing machine. RESULTS OptiBond aided bond strengths were 23.7 +/- 5.6 MPa to bleached and 19.6 +/- 2.9 MPa to unbleached enamel. For All-Bond 2, bleached enamel exhibited bond strengths of 14.9 +/- 4.0 MPa and unbleached enamel exhibited a bond strength value of 20. 4 +/- 2.3 MPa. The composite bond strength for One-Step was 13.6 +/- 5.9 MPa to bleached and 23.0 +/- 3.9 MPa to unbleached enamel. There was no statistical difference between OptiBond (alcohol base) aided bond strengths for bleached and unbleached enamel; however, the bond strength of composite to bleached enamel with All-Bond 2 or One-Step (acetone base) was significantly lower than unbleached controls. CONCLUSION The effect of bonding agent usage on composite bond strength to enamel bleached with a particular carbamide peroxide was dependent on the bonding agent used.

Periodontal disease and bisphosphonates induce osteonecrosis of the jaws in the rat

Bisphosphonates (BPs) are medications used commonly to treat primary and metastatic bone cancer, as well as osteoporosis. Although BPs improve bone mineral density, reduce fracture risk, and reduce hypercalcemia of malignancy, some patients develop BP‐related osteonecrosis of the jaws (BRONJ). This devastating complication is defined as clinically exposed bone in the maxillofacial region for more than 8 weeks. Despite an increasing number of BRONJ cases since first reported, the disease pathophysiology remains largely unknown. Since published studies suggest a significant role for dental disease in the pathophysiology of BRONJ, we developed a BRONJ animal model where aggressive periodontal disease is induced by ligature placement around the crown of the right maxillary first molar in the presence of vehicle (veh) or zoledronic acid (ZA), a potent BP. Ligature placement induced significant alveolar bone loss, which was attenuated by ZA treatment. Osteonecrosis was observed associated with ligature‐induced periodontitis in the ZA‐treated group. This was seen as sequestration and extensive periosteal alveolar bone formation on micro–computed tomography (µCT) in the ligated site of BP‐treated animals. Histologic examination confirmed these findings, seen as necrotic bone with diffuse loss of osteocytes and empty lacunae, rimming of the necrotic bone by squamous epithelium and inflammation, and exposure to the oral cavity. Importantly, the rat lesions were strikingly similar to those of BRONJ patients. Our data suggest that dental disease and potent BP therapy are sufficient for BRONJ development in the rat.

Increased prevalence of bisphosphonate-related osteonecrosis of the jaw with vitamin D deficiency in rats.

Necrotic bone exposure in the oral cavity has recently been reported in patients treated with nitrogen‐containing bisphosphonates as part of their therapeutic regimen for multiple myeloma or metastatic cancers to bone. It has been postulated that systemic conditions associated with cancer patients combined with tooth extraction may increase the risk of osteonecrosis of the jaw (ONJ). The objective of this study was to establish an animal model of bisphosphonate‐related ONJ by testing the combination of these risk factors. The generation of ONJ lesions in rats resembling human disease was achieved under the confluence of intravenous injection of zoledronate (ZOL; 35 µg/kg every 2 weeks), maxillary molar extraction, and vitamin D deficiency [VitD(−)]. The prevalence of ONJ in the VitD(−)/ZOL group was 66.7%, which was significantly higher (p < .05, Fisher exact test) than the control (0%), VitD(−) (0%), and ZOL alone (14.3%) groups. Similar to human patients, rat ONJ lesions prolonged the oral exposure of necrotic bone sequestra and were uniquely associated with pseudoepitheliomatous hyperplasia. The number of terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate–biotin nick‐end label–positive (TUNEL+) osteoclasts significantly increased on the surface of post–tooth extraction alveolar bone of the VitD(−)/ZOL group, where sustained inflammation was depicted by [18F]fluorodeoxyglucose micro‐positron emission tomography (µPET). ONJ lesions were found to be associated with dense accumulation of mixed inflammatory/immune cells. These cells, composed of neutrophils and lymphocytes, appeared to juxtapose apoptotic osteoclasts. It is suggested that the pathophysiologic mechanism(s) underpinning ONJ may involve the interaction between bisphosphonates and compromised vitamin D functions in the realm of skeletal homeostasis and innate immunity.

Mouse mtDNA mutant model of Leber hereditary optic neuropathy

An animal model of Leber hereditary optic neuropathy (LHON) was produced by introducing the human optic atrophy mtDNA ND6 P25L mutation into the mouse. Mice with this mutation exhibited reduction in retinal function by elecroretinogram (ERG), age-related decline in central smaller caliber optic nerve fibers with sparing of larger peripheral fibers, neuronal accumulation of abnormal mitochondria, axonal swelling, and demyelination. Mitochondrial analysis revealed partial complex I and respiration defects and increased reactive oxygen species (ROS) production, whereas synaptosome analysis revealed decreased complex I activity and increased ROS but no diminution of ATP production. Thus, LHON pathophysiology may result from oxidative stress.

Resolution of pain and complete healing of mandibular osteoradionecrosis using pentoxifylline and tocopherol: a case report

The radiation-induced fibroatrophic process (RIF) is a time-dependent adverse sequela to high-dose radiotherapy that can result in irreversible tissue death and bone exposure in the irradiated tissue. Osteoradionecrosis (ORN) is a late effect of RIF, described as bony exposure present for more than 3 months that can occur in 20% of patients irradiated for head and neck cancer. The intractable characteristics of ORN make both management and resolution of the disease process challenging, with 25% of cases recurring despite aggressive treatment with resection and reconstruction of the necrotic bone. In this article, we present a case of a 66-year-old man with unevoked ORN of the left posterior lingual mandibular cortex that was successfully treated and resolved with 6 months of pentoxifylline 400 mg twice a day and tocopherol 1000 IU every day.

Retinal pigment epithelial cell death by the alternative complement cascade: role of membrane regulatory proteins, calcium, PKC, and oxidative stress.

PURPOSE Retinal pigment epithelial (RPE) cell death is an important feature of the advanced forms of AMD. Complement alternative pathway (AP) activation is associated with RPE cell death in AMD. In this study, we developed a new model to initiate AP activation on RPE cells and investigated the cellular mechanisms modulating AP activation-mediated RPE cell death. METHODS An anti-RPE antibody was developed. A spontaneously arising human RPE cell line (ARPE-19) and donor RPE cells were primed with this antibody followed by stimulation with 6% C1q-depleted human serum (C1q-Dep) to activate AP. Complement activation was evaluated by flow cytometry and immunofluorescent staining. Cellular response to complement activation was examined by measurement of intracellular calcium and adenosine triphosphate (ATP) release. Cell viability was assessed by Sytox orange, tetrazolium salt, and lactate dehydrogenase release assays. RESULTS Alternative pathway complement-mediated RPE cell death was associated with membrane attack complex formation and a rapid rise in intracellular calcium followed by release of ATP. Downregulation of membrane complement regulatory proteins and protein kinase C (PKC) inhibition increased cell susceptibility to complement attack. Pretreatment of RPE cells with either hydrogen peroxide or hydroquinone enhanced cell death. Chronic repetitive treatment of RPE cells with low levels of oxidants also enhanced complement-mediated cell death. CONCLUSIONS Activation of complement through the alternative pathway induces sublytic and lytic phases of complement attack on RPE cells, leading to cell death modulated by extracellular calcium, membrane complement regulatory proteins, and intracellular signaling mechanisms. Single-dose oxidant exposure and low-dose repetitive oxidant exposure rendered RPE cells more susceptible to complement-mediated death.

Clinical validation of a nanodiamond-embedded thermoplastic biomaterial

Significance There is a continued need to advance novel nanomedicine platforms into the clinic to address treatment challenges in oncology, infection, and regenerative medicine, among other areas. As such, this work demonstrates the in-human validation of nanodiamonds through their incorporation into gutta percha [nanodiamond-embedded gutta percha (NDGP)], a polymer that repairs root canal treatment sites following tissue disinfection. A randomized, dual-arm clinical trial was implemented, and study endpoints included confirmation of lesion healing, postoperative pain reduction, and the absence of reinfection. To date, the NDGP-treated patients successfully met the study endpoints. Therefore, these findings support the potential expansion of nanodiamonds, and the broader nanomedicine field, into other disease indications. Detonation nanodiamonds (NDs) are promising drug delivery and imaging agents due to their uniquely faceted surfaces with diverse chemical groups, electrostatic properties, and biocompatibility. Based on the potential to harness ND properties to clinically address a broad range of disease indications, this work reports the in-human administration of NDs through the development of ND-embedded gutta percha (NDGP), a thermoplastic biomaterial that addresses reinfection and bone loss following root canal therapy (RCT). RCT served as the first clinical indication for NDs since the procedure sites involved nearby circulation, localized administration, and image-guided treatment progress monitoring, which are analogous to many clinical indications. This randomized, single-blind interventional treatment study evaluated NDGP equivalence with unmodified GP. This progress report assessed one control-arm and three treatment-arm patients. At 3-mo and 6-mo follow-up appointments, no adverse events were observed, and lesion healing was confirmed in the NDGP-treated patients. Therefore, this study is a foundation for the continued clinical translation of NDs and other nanomaterials for a broad spectrum of applications.

The efficacy of pentoxifylline/tocopherol combination in the treatment of osteoradionecrosis.

BACKGROUND Osteoradionecrosis (ORN) is an unfortunate complication of radiation therapy to the head and neck. Treatment has historically centered around hyperbaric oxygen therapy and surgical removal of necrotic bone. Recently, a new theory on the pathogenesis of ORN has proposed treatment with pentoxifylline (PTX) and tocopherol/vitamin E. The aim of this retrospective analysis was to evaluate the effectiveness of pentoxifylline and tocopherol in the management of patients with ORN. METHODS The hospital dentistry group managed 13 patients that presented to our service with exposed bone after cancercidal doses of radiation to the head and neck. The patients were prescribed PTX 400 mg bid and tocopherol 1,000 IU QD. RESULTS Eleven of the 13 patients exhibited improvement and resolution. No adverse events were noted during treatment. CONCLUSION This medical modality of treating ORN appears safe and effective, inducing bone and mucosal healing.

Dental treatment in the cardiothoracic intensive care unit for patients with ventricular assist devices awaiting heart transplant: a case series

OBJECTIVE This report aims to describe the dental protocol for treating in the intensive care unit patients with end-stage heart failure who have had ventricular assist devices (VADs) emergently implanted as a bridge to heart transplant. This protocol permitted the rendering of safe and effective dental care in this setting and did not result in near-term (1-30 days) excessive hemorrhage, local and systemic infection, or contamination of the VAD. STUDY DESIGN This descriptive cross-sectional study by the University of California, Los Angeles, Hospital Dental Service examined the dental care of 9 patients (mean age, 50 ± 12.9 years) with class IV stage D heart failure. RESULTS Nine patients, 22 days (mean) after VAD placement, received dental treatment after intravenous prophylactic antibiotics and maintenance of prior anticoagulation, antiplatelet, or antithrombin regimen. Eight patients had extractions (mean, 4; range, 1-12), and one of them also required scaling and root planing (SRP) of the remaining teeth. A ninth individual only required SRP of 4 quadrants. No adverse outcomes developed. CONCLUSIONS Emergent removal of active dental disease in patients with VAD awaiting heart transplant can be safely accomplished using established protocols with extended vigilance.