• The Effect of Processing Techniques for rhBMP-2 Coated Titanium Implants on Alveolar Augmentation and Osseointegration in the Canine Supraalveolar Peri-Implant Defect Model

      Decker, John; Department of Oral Biology (9/5/2014)
      A current paradigm-shift in implant dentistry places restorative factors associated with esthetics and function in front of implant site selection based on bone quantity and quality. Marginal bone loss after implant placement, resorption of the edentulous alveolar ridge, bone defects from periodontal disease, and ridge aberrations due to trauma all challenge implant treatment driven by esthetics and function. Clinicians compensate for bone loss using bone augmentation procedures including bone grafts, bone materials, biologic mediators, barrier devices, or combinations thereof. The search for treatment modalities to address implant placement into compromised sites has lead to the development of a variety of products designed to replace or induce bone formation. Some believe an ideal material could be coated onto implants, to promote osseointegration, induce local bone formation, while not requiring adjunctive biomaterials, or procedures including placement of allogeneic and xenogeneic biomaterials, or autograft bone.
    • Evaluation of a Novel Compression Resistant Matrix for Recombinant Human Bone Morphogenetic Protein-2 (RHBMO-2) for Onlay Graft Indications

      Lu, Sheldon; Department of Oral Biology (6/4/2014)
      The discovery and subsequent characterization of endogenous signaling peptides known as bone morphogenetic proteins (BMPs) capable of inducing de novo bone formation in postfetal life represents a critical advancement in the understanding of tissue morphogenesis and has become an incentive to develop additional growth factor based tissue engineering strategies (Wozney & Seeherman 2004). Because BMPs act locally, a suitable carrier system must be used to ensure effective presentation of an adequate dose to a target site (Mont et al. 2004). A number of candidate biomaterials have thus been tested as potential carrier technologies (Huang et al. 2008). Currently, recombinant human BMP-2 (rhBMP-2) coupled with an absorbable collagen sponge (ACS) manufactured from bovine Achilles tendon Type 1 collagen is the only FDA approved device for orthopedic and craniofacial indications. Although the rhBMP-2/ACS construct has demonstrated clinical efficacy for indications including spine fusion, long bone fracture healing, sinus and alveolar augmentation, the ACS’s inability to resist tissue compression limits its use for onlay indications (Wikesjö et al. 2007).
    • EFFECT OF MATRIX-BOUND BISPHOSPHONATES ON MONOCYTE DIFFERENTIATION AND OSTEOCLAST FUNCTION

      Abraham, Pheba; Abraham, Pheba; Department of Oral Biology (5/1/2017)
      This study was to explore the effect of local, matrix-bound bisphosphonates to monocytedifferentiation and osteoclast function in vitro. Experiments were designed using osteoassay plates. Cell-viability, differentiation, resorption pits and gene expression were analyzed to see the effect of matrix-bound BPs on monocyte differentiation and osteoclast function. EDTA was used as a chelating agent to remove the bound BPs. There was a dose dependent response in the differentiation and resorption pits. With chelation, there was increase in differentiation, resorption pits and increase in the calcium and PYD in the supernatant. Thus, matrix-bound Bisphosphonatesare biologically active and they inhibit monocyte differentiation and osteoclast function. Thereby removal of this matrix-bound drug can rescue osteoclast differentiation and function.
    • Inherent Gene Expression and Protein Profile Differences Between Alveolar and Basal Bone

      Alotaibi, Fawwaz; Department of Oral Biology (5/1/2015)
      The mandible is composed to two bone types: alveolar and basal. Previous studies on the mandible have shown that the alveolar bone resorbs more than the basal bone after tooth extraction or as a result of tooth movement. Reasons for why the resorption rates are different is not well understood. This research begins exploring the differences of the alveolar and basal bone by using comparison characteristics such as bone mineral density (BMD), gene expression, protein profiles, and number of osteocytes. The research investigates these characteristics by using Real time RCR to study the differences in gene expression and protein profiles of the alveolar and basal bone. Micro-CT was used in comparing density and bone architecture characteristics of the alveolar and basal bone. Immunohistochemistry was used to better understand how osteocytes are different between the two bone types in hopes of later being able to understand the differences in resorption rates. The real time PCR showed that four genes are expressed significantly higher in basal bone than alveolar bone: SOST, E-11, DMP-1, MEPE. Three of which are associated with mature osteocytes indicating that basal bone has more mature osteocyte phenotypes. Micro-CT data indicated that the basal bone is denser and less porous than alveolar bone. There was no significant difference in immunohistochemistry and further quantitative testing is needed to draw and significant correlation.
    • Marker Co-Expression Analysis of Initial Cellular Events in the Critical-Size Rat Calvarial Defect Model and the Effect of Bone Morphogenetic Protein-2 (rhBMP-2)

      Capetillo, Joseph F.; Department of Oral Biology (4/15/2016)
      Craniofacial defects can result from congenital malformations, trauma, tumor resection,periodontal disease, post-extraction ridge remodeling, and peri-implantitis. Regenerationof bone is critical to achieving functional and esthetic outcomes in the rehabilitation ofsuch defects. Traditional strategies for osseous regeneration include a multiple ofsurgical techniques utilizing autologous bone, cadaver-sourced allogeneic or xenogeneicbone, synthetic bone biomaterials, barrier membranes, or combinations thereof(Wikesjö, Qahash 2009). The need to enhance the predictability of regeneration inespecially large defects that cannot heal adequately without intervention (critical-sizedefects) has led to recent development of protein- and cell-based technologies.[Introduction, first paragraph]
    • The role of Toll-like receptor (TLR) 2 in the systemic immune response profile of mice induced to develop squamous cell carcinoma of the upper aerodigestive tract

      El-Shafey, Sally; El-Shafey, Sally; Department of Oral Biology (4/1/2017)
      Background Head and necksquamous cell carcinomais associated with immunosuppression, a state in which the progression of cancer is associated with disturbances in the immune system functions. Emerging studies suggest a fundamental role for the innate immune system, particularly Toll-like receptor 2 (TLR2), in this process.QuestionsIn this study, we investigated the potential roles of TLR2 on systemic immune profile in a mouse model of headand necksquamous cell carcinoma.MethodsTwo different protocols of a mouse model of 4-nitroquinoline 1-oxide and ethanol-induced carcinogenesis to induce head and neck squamous cell carcinoma were used. To evaluate the systemic immune profiles, total RNA wasisolated from the spleens of four groups of animals, including carcinogen-treated and control untreated wild-type and toll-like receptor 2-deficient animals. Quantitative real-time PCR was performed forgenesrepresentative of house-keeping genes, type 1 and type 2 immune responses, regulatory T and B cells, and adenosine receptors.Results and ConclusionIn the standard protocol of 4-nitroquinoline 1-oxide and ethanol-induced carcinogenesis, there was asignificant upregulation of adenosine receptor A2a in the spleens of wild type iiimice treatedwith4-nitroquinoline 1-oxide and ethanolrelative to wild type untreatedanimals. In the standard protocol of carcinogenesis, there was a significant upregulation of CD39 in the spleens of TLR2-koanimalstreated with 4-nitroquinoline 1-oxide and ethanol relative to untreated TLR2-ko mice. These results suggest that carcinogenesis in the upper aerodigestive tract is associated with alterations in the systemic immune profile reflected in the spleen. However, the specific impact on the immune profiles appears to be affected by the presence or absence of TLR2.
    • Changes in the RANK/RANKL/OPG Signaling System as a Mechanism of Zoledronate-Induced Osteonecrosis of the Jaw

      Lane, Jonathan; Department of Oral Biology (3/22/2016)
      Bisphosphonates (BPs) are widely used for the treatment of osteoporosis, hypercalcemia of malignancy, skeletal-related events associated with bone metastases, and for managing lytic lesions of multiple myeloma. A serious risk associated with the use of BPs is the development of Bisphosphonate Related Osteonecrosis of the Jaw (BRONJ), a painful and inflamed area of exposed bone in the oral cavity that fails to heal after 6-8 weeks. The cause of BRONJ is unknown, but it is believed to be due primarily to a longterm suppression of bone remodeling, caused by BP’s potent inhibition of osteoclastic activity. At the cellular level, it is generally accepted that bisphosphonates are taken in by osteoclasts at sites of relatively greater bone remodeling, owing to the strong affinity of bisphosphonates for the mineralized matrix and the increased activity of osteoclasts at active sites of resorption. The accumulation of intracellular bisphosphonates ultimately leads to osteoclast dysfunction or apoptosis through the formation of nonhydrolyzable ATP-analogues, or due to inhibition of the mevalonate pathway responsible for synthesis of sterols and lipids necessary for proper cellular membrane structure. However, the refined details of the pathophysiology of BRONJ remain elusive. The RANK/RANKL/OPG system is a well-known signaling pathway for the recruitment and differentiation of osteoclasts. RANK is a surface-bound receptor on osteoclasts, and requires binding of its ligand, RANKL, for cell activation and ultimately resorption of bone. On the other hand, OPG is a soluble decoy receptor for RANKL. Therefore, osteoclastic activity is effectively regulated by the ratio of RANKL to OPG. For years, it has been generally accepted that osteoblasts are the primary source of both RANKL and OPG. However, it is now recognized that the master orchestrator of bone activity, the osteocyte, contributes to the pathway. Furthermore, it has been shown that in localized tissue damage or hypoxia, such as in a dental extraction, immediately adjacent surviving nonapoptotic osteocytes upregulate RANKL and downregulate OPG. It is unknown to what extent BPs may alter the normal osteocyte response to injury and hypoxia or, ultimately, the dynamics of the RANK/RANKL/OPG system. Furthermore, the extent to which this could contribute to the development of BRONJ is unexplored.There is a paucity of studies concerning how the fundamental system responsible for bone remodeling, RANK/RANKL/OPG, is effected by BPs. It may be that changes in this system, especially in signals derived from the osteocyte, contribute to the pathophysiology of BRONJ.
    • Efficacy of Epigallocatechin-3-gallate-palmitate as a Virucidal Compound Against Norovirus

      Widjaja, Nicole; Department of Oral Biology and Diagnostic Sciences (Augusta University, 2020-05)
      Norovirus is a highly infectious, non-enveloped virus found to be the leading cause of global gastroenteritis outbreaks. Every year within the United States, this virus is responsible for an average of 19-21 million cases of acute gastroenteritis, approximately 570-800 deaths, and has been the cause of 1.7 to 1.9 million outpatient visits. On a global scale, healthcare costs and lost productivity are estimated to $60 billion due to illnesses and outbreaks caused by the burden of norovirus. Unfortunately, current measures to prevent the transmission of norovirus remain insufficient as the Center for Disease Control and Prevention (CDC) can only recommend hand washing with soap and water as the best preventative measure. The only other hand hygiene method available is alcohol-based hand sanitizers, but the CDC states that they are not effective in inactivating norovirus particles and warns that it should not be considered a substitute to hand washing. Recently, epigallocatecin-3-gallate (EGCG) a major component extracted from the leaves of Camellia sinensis, also commonly known as tea plant, has shown potential to be the next viable candidate as an antiviral solution. Lipid derivatives of EGCG, most notably EGCGpalmitate, has shown to express potent antiviral properties and has showed to play a crucial role in the fight against other non-enveloped viruses such as poliovirus and adenovirus. In this study, we determined the efficacy of EGCG-palmitate in novel formulations against human norovirus surrogates by utilizing the EU international standards for hand hygiene in vitro studies against norovirus. Evidence is provided determining the virucidal activity of alcohol-based ProtecTeaV formulations containing EGCG-palmitate as well as the potential for EGCG-palmitate as a persistent residual virucidal activity against norovirus surrogates, feline calicivirus (FCV) and murine norovirus-1 (MNV-1). By creating an effective, environmentally friendly, non-toxic and long lasting solution composed of EGCG-palmitate, the results of this innovative approach would expand the options available to reduce the transmission of norovirus essentially bridging the gap for a new preventative hand hygiene and ultimately impacting the spread of norovirus on a worldwide scale.
    • Biocompatibility and mechanical/physical properties of 3D printed, milled, and conventionally processed denture base materials

      Ulmer, Mallory; Biomedical Sciences (Augusta University, 2019-12)
      According to the American College of Prosthodontists, over 36 million people in the USA are edentulous with a 2:1 predilection for geriatric patients1. Each year, an estimated 15% of edentulous Americans will seek denture treatment1. Conventional dentures require multiple visits and lab processing time. 3D printing technology offers the potential to reduce the number of appointments and speed up the time until patient rehabilitation. However, the newly FDA-certified 3D printer denture resins, featuring secretive and proprietary formulae, lack studies concerning their biocompatibility/safety and mechanical strength. This study aims to investigate the biocompatibility and physical properties of one such 3D printer resin, NextDent® Base (Vertex, Soesterberg, The Netherlands), and compare it to pre-existing conventional polymethyl methacrylate (PMMA) denture base (Lucitone 199, Dentsply Sirona, York, Pennsylvania) and milled PMMA denture base (IvoBase CAD®, Ivoclar Vivadent AG, Schaan, Liechtenstein). The cytotoxicity was examined using of 12 discs: conventional PMMA, milled PMMA, as-printed 3D printer resin, post-cured 3D printer resin, and Teflon controls. An MTT assay using human periodontal ligament (900L) cells was employed, and specimens were aged for 1, 3, 7, 10, and 14 days. After day 7, there were no statistically significant differences among the groups, excluding the Teflon control, which showed significantly less cell viability on day 14. Bars of conventional PMMA, milled PMMA, as-printed 3D printer resin, and post-cured 3D printer resin were subjected to a 3-point bend test to examine flexural strength and moduli differences. The mean flexural strength was 63.8 ± 3.06, 82.6 ± 1.9, 5.1 ± 0.4, and 22.1 ± 6.4 MPa, respectively, while the flexural moduli were 1757.3 ± 109.5, 2226.7 ± 76.3, 110.3 ± 20.3, and 537.0 ± 210.6 MPa, respectively. The flexural strength and modulus were significantly different among all groups. Weibull analyses for conventional PMMA, milled PMMA, as-printed 3D printer resin, and post-cured 3D printer resin revealed a Weibull modulus of 23.5, 42.8, 16.6, and 3.7, respectively, and a characteristic strength of 65.2, 83.5, 5.3, and 24.5 MPa, respectively. The characteristic strength was significantly different among all groups as well. The Weibull modulus was significantly different between all groups, except for conventional vs. as-printed, which were not significantly different. In summary, milled PMMA featured significantly greater mechanical properties. Both 3D printed groups proved to be very weak, with the as-printed group being the weakest of all. The differences between the as-printed and post-cured groups highlight the importance of properly post-curing the resin. While the biocompatibility results showed promise, the mechanical testing results were disappointing. Unfortunately, the findings suggest that 3D-printed denture base resin is not yet ready for clinical use.
    • Effect of an Er,Cr:YSGG Laser on P. Gingivalis-Contaminated Titanium Alloy Dental Implant Surfaces In Vitro

      Strever, Jason; Department of Oral Biology (2016-04)
      Implant dentistry has become a widely accepted modality to replace missing teeth. However, dental implants are susceptible to biofilm-mediated inflammatory lesions (peri-implant mucositis / peri-implantitis), similar to that seen around natural teeth (gingivitis / periodontitis). These lesions, in turn, threaten the longevity of implants as anchors for dental prostheses. Because of the similarity in etiology and presentation, comparable treatment modalities are applied to resolve peri-implant and periodontal inflammatory lesions. Such a shared treatment includes mechanical debridement, with or without surgical repositioning of the soft tissue complex. However, most contemporary dental implants feature threads to engage the alveolar bone and a micro/nano-textured surface to stimulate bone-implant contact (osseointegration). Therefore, when the implant threads become exposed and contaminated by biofilm, subsequent surface debridement / decontamination becomes considerably more complex than with that of a natural tooth, which is usually debrided using a metal curette or ultrasonic device. The micro/nano-textured surface of a dental implant is easily damaged by instrumentation using a metal curette. If an efficient method of dental implant surface decontamination could be established, then clinical protocols may be developed that effectively clean the implant surface to achieve peri-implant tissue health. To this end, lasers have been introduced; however, directly applied laser energy may also affect implant surface characteristics, including micro/nano-structure and composition, essential to osseointegration. Therefore, lasers may have disadvantageous clinical effects, in turn compromising peri-implant tissue consolidation and health: the very aspects its use is attempting to provide. Commercially available Er,Cr:YSGG lasers have been used to remove such implant-attached deposits, however the efficacy in removal of bacteria and the safety to the implant surface integrity have yet to be demonstrated quantitatively.
    • Effects of vitamin D supplementation on untreated chronic periodontitis

      Mogrovejo, Fernando; Master of Oral Biology (2016)
    • Porphyromonas gingivalis Escape-from Autophagy in Human Myeloid Dendritic Cells via Minor Mfa-1 Fimbra-DC-Sign Interactions

      El-Awady, Ahmed; Department of Oral Biology (2014-03)
      In professional phagocytes, early receptor recognition is crucial to determine the fate of engulfed microorganisms. Among the many pattern recognition receptors (PRRs) expressed by dendritic cells (DCs), the C-type lectin DC-SIGN is of particular interest as it has been associated with immunosuppression by infecting pathogens. While autophagy has emerged as a major immune mechanism against microbes, very little is presently understood about its role in elimination o f intracellular pathogens; especially in the context o f the PRR diversity expressed by DCs. Hence, the study aimed to investigate the role of DC-SIGN targeting by the anaerobic pathogen Porphyromonas gingivalis in its intracellular survival within myeloid DCs and how intracellular routing through early and late endosomes, autophagosomes and lysosomes relate to this survival. Employed in this investigation were human monocyte derived DCs and a panel of isogenic fimbriae deficient mutant strains of P. gingivalis that express the DC-SIGN ligand (Mfa-1 fimbriae) and/or the TLR2 ligand (FimA fimbriae). The results show that uptake of P. gingivalis by the nonDC-SIGN dependent route resulted in intracellular killing and elimination of intracellular content of P. gingivalis. This route was associated with early endosomal routing through Rab5, increased LC3-II and LAMP-1, as well as the formation of double membrane intracellular phagophores. In contrast, DC-SIGN dependent uptake did not induce significant levels of Rab5, LC3- II, and LAMP1. Moreover, P. gingivalis was mostly contained within single membrane vesicles where it survived intracellularly. Survival was ameliorated by forced autophagy. These results suggest that myeloid DCs are fully capable of eliminating intracellular pathogens by autophagy but that selective engagement of DC-SIGN is a microbial tactic for evasion of antibacterial autophagy leading to intracellular survival.
    • Sustained Release Formulation for Vascular Endothelial Growth Factor

      Elzinga, Jennifer Lynn; Department of Oral Biology (2013-03)
      Necrosis of tissue due to trauma or a surgical procedure is a complication of wound healing. This necrosis, or tissue death, occurs when the vasculature is unable to perfuse involved tissue with the oxygen and nutrients necessary to maintain viability. To provide adequate access, reflecting a flap of tissue is often necessary in a variety of surgical procedures, including periodontal surgeries. The success of these procedures is limited by the development of tissue flap necrosis. The survival of these tissue flaps is dependent upon adequate perfusion by the blood vessel supply at the base of the flap, followed by the growth of new vascular channels from the recipient site. However, if angiogenesis does not promptly reach the distal extent of the flap, this portion becomes ischemic, leading to necrosis. Loss of the protective flap delays healing and increases the risk of scarring and infection. Necrosis of this distal region of a tissue flap begins as early as 24 hours following the surgical procedure and progresses rapidly until day 3 when the unaffected tissue begins to stabilize.1 A variety of pharmacological strategies to enhance tissue flap perfusion have been tested in an attempt to prevent necrosis. One such strategy is the administration of angiogenic growth factors such as vascular endothelial growth factor (VEGF). VEGF is known to stimulate the proliferation of endothelial cells from existing vasculature to create new blood vessels, thus enhancing 8 tissue survival.2-7 In addition, VEGF contributes to other aspects of wound healing, including inflammation, granulation tissue formation, reepithelialization, matrix formation, and remodeling.2 Administration of VEGF to wound healing models has shown promising results by increasing vascular formation, leading to enhanced tissue perfusion. However, its short duration of action and rapid dissipation from the target site reduces its effectiveness.8 Maintaining therapeutic concentrations of VEGF at the target site to maximize new vessel growth and reduce necrosis, either multiple applications or an extended-release delivery system is required. An ideal system would provide ease of use and delivery kinetics for sustained therapeutic dosing of VEGF to the wound environment for the duration of healing, thereby minimizing tissue necrosis. A variety of application methods and delivery systems are under investigation in the search to develop one that provides utility as well as improved clinical outcome.
    • Primary versus secondary reconstruction of mandibular critical size defects using recombinant human bone morphogenetic protein 2: an experimental study in dogs

      Hussein, Khaled A.; Department of Oral Biology (2012-12)
      Very often, delayed reconstruction becomes the setting of choice in the reconstruction of large segmental defects in the mandible. Our hypothesis is that rhBMP2 delivery would elicit endogenous expression of BMP2 and VEGF in the soft tissue bed of the defect. Such response is expected to be more pronounced in the immediate than the delayed reconstruction, which will correlate with the quantity and quality of bone formation in the two settings. We also hypothesized that vascular endothelial cells (ECs) of the surrounding soft tissue contribute to the endogenous production of BMP2. In this study we used a mandibular canine segmental defect model (35 mm), periosteum was excised and also the delayed reconstruction group was included in this study in addition to the control group. We investigated the effect of different reconstruction settings on the quantity and quality of bony regenerates; on the production of endogenous BMP2 from the soft tissue bed of the defects and finally we tried to explore the source of this rhBMP2- induced endogenous BMP2 production both in vivo and in vitro. This study demonstrated that rhBMP2 delivery is more effective in immediate reconstruction of large mandibular segmental defects. Immediate delivery of rhBMP2 yielded more adequate reconstruction of the defect after 12 weeks, evident by the quantity and quality of the bone regenerate. Only in the immediate reconstruction group, the advantageous bone parameters were associated with significant up-regulation of BMP2 mRNA and protein in the soft tissue bed of the defect. This suggests that endogenous-BMP2 is important in maintaining the short-acting effect of the delivered rhBMP2. Regarding the source of the endogenous-BMP2, protein co-localization with ECs marker suggested that these cells could be the source for the endogenous BMP2 secretion in response to rhBMP2 treatment. This was confirmed by the in-vitro results on both the mRNA and protein levels. The gradual increase in expression of BMP2 mRNA and the significant upregulation of secreted BMP2 protein upon stimulation of human umbilical vein endothelial cells with 100-ng/ml rhBMP2 recognized a new mechanism of positive feed back response of ECs in response to BMP2 treatment.