• 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; 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.
    • 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.
    • SYNERGISTIC EFFECTS OF THE COMBINATION OF ERLOTINIB & EXO2 ON HEAD AND NECK CANCER

      Thakkar, Parth; Department of Biological Sciences; Department of Oral Biology; Teng, Yong; Augusta University (2019-02-13)
      More than 90% of head and neck cancer is head and neck squamous cell carcinoma1 (HNSCC). Currently, the treatment involves modern surgery, conventional chemotherapy, and radiation. However, targeting, the epidermal growth factor receptor (EGFR) has been shown to prove advantageous for patient survival. EGFR activation leads to cell cycle progression. Blocking the EGFR by an antibody results in the inhibition of the receptor, therefore inhibition of cell proliferation. This makes EGFR a prime target for anticancer therapy, specifically with tyrosine kinase inhibitors being looked at as a possible form of inhibition. The goal of this project was to hopefully use small molecule inhibitor EXO2 and an EGFR specific tyrosine kinase inhibitor, Erlotinib, in a synergistic manner to fight against HNSCC. This study was done using cell cultures, MTT assay�s and western blot techniques, with cell cultures being done using the H6 cell line. The results from this study were found to be a preliminary success and will pave the way for future experiments in this area.
    • SERUM-C TERMINAL CROSSLINKING TELOPEPTIDE (CTX) AS A PREDICTIVE BIOMARKER OF BISPHOSPHONATE-RELATED OSTEONECROSIS OF JAW (BRONJ): SYSTEMATIC REVIEW AND META-ANALYSIS

      Sun, Christina; Awad, Mohamed E; Jernigan, Joshua; College of Science and Mathematics; Department of Oral Biology; Dental College of Georgia; Elsalanty, Mohammed; Augusta University (2019-02-13)
      The aim of this systematic review was to evaluate the validity of using preoperative serum C-terminal crosslinking telopeptide (CTX) levels as predictive factor of increased risk of developing medication-related osteonecrosis of the jaw (MRONJ) in patients on bisphosphonate (BP) therapy who undergo invasive dental procedures. A search was conducted through PubMed, MEDLINE, and Web of Science, following PRISMA guidelines and the Cochrane Handbook for Systematic Reviews of Interventions. Meta-analysis was conducted on the risk ratio. The methodological index for nonrandomized studies (MINORS) and Quality Appraisal of Reliability Studies (QAREL) checklist were used to assess quality. Eighteen clinical trials, involving 2301 patients were included. Most patients received Alendronate or Risedronate for an average of 62.14 months. The average serum CTX level in BP-treated patients before surgery was 217.67 pg/ml. Meta-analysis demonstrated that the cutoff in CTX level (150 pg/ml) was not predictive of BRONJ risk. The sensitivity of CTX value <150 pg/ml was 34.26% and the specificity was 77.08%. The use of CTX to diagnose BRONJ risk following dental procedures in bisphosphonate-treated patients is not justified. Further studies are needed to develop other reliable biomarkers.
    • Histology of the Dental Extraction Sites of Bisphosphonate Treated Rats

      Ferguson, Alisa; Department of Oral Biology (Augusta University, 2018-12)
      Bisphosphonate is a drug given to both men and women who are experiencing decreasing bone density and strength. When patients taking bisphosphonate undergo some sort of jaw trauma (i.e. tooth extraction, accident), they can experience necrosis or cell death of the jawbone. Our hypothesis is that bisphosphonate molecules bound to the bone matrix contribute to bone necrosis. For my thesis, a histological analysis of the mandibles from bisphosphonate treated rats after dental extraction with and without removal of bisphosphonates from the extraction site of the bone was done. Histological sections of the jaw from bisphosphonate treated rats after bilateral extraction of the first and second molar teeth were taken. On one side, the extraction site was treated with EDTA to chelate bisphosphonates from the bony wall of the tooth socket. The other side of the rat’s jaw was treated with Saline. I then evaluated the vitality of alveolar bone by counting the number of dead versus live osteocytes around the extraction site and comparing the ratios between the chelated and un-chelated sides from each rat. The study determined whether removal of localized bisphosphonates is beneficial to preserve bone vitality after dental extraction. As expected, the percentage of live osteocytes decreased in the alveolar bone of animals treated with Zoledronate (ZA), a strong dose of bisphosphonate. Furthermore, there was a trend of increased percentage of live cells when EDTA was used, although the differences were not statistically significant. These results support other studies in our laboratory that have shown that localized bisphosphonates play a role in the osteonecrosis associated with ZA treatment. It, therefore, provides evidence that localized bisphosphonates contribute to the etiology of bone necrosis in patients undergoing bisphosphonate treatment.
    • 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)
    • Novel Therapeutic Approaches to Leishmania Infection

      Makala, Levi HC; Baban, Babak; Department of Pediatrics; Department of Oral Biology (InTech, 2014-03-19)
      Leishmaniasis is a parasitic disease transmitted by phlebotomine sandflies. Approximately 1.2 million cases of cutaneous leishmaniasis (CL) and 500,000 cases of visceral leishmaniasis (VL), which is lethal if untreated, occur annually across the globe as per world health organization (WHO) estimates [1-3]. Current statistics and information relevant to leishmaniasis are summarized in Table 1. Leishmaniasis currently affects about 12 million people and it is estimated that approximately 350 million people live in risk of infection [1-3].The number of cases of leishmaniasis is probably underestimated because only 40 of the 88 countries where diseases frequently occur report them on a regular basis [4]. Leishmaniasis, is caused by several leishmania spp., that are obligate intracellular and unicellular kinetoplastid protozoan flagellate that establish themselves within the phagolysosome of host immune competent cells, especially macrophages and dendritic cells (DCs). In 1903, W.B. Leishman and C. Donovan reported this new parasite at the turn of the century [5,6]. Ronald Ross christened the new genus leishmania and the new species donovani in year 1903 [7]. L. major infection (leishmaniasis) in mice is a widely used model of human infection that has yielded critical insights into the immunobiology of leishmaniasis [8-10]. Leishmaniasis as a parasitic disease manifests itself mainly in 3 clinical forms; visceral leishmaniasis (VL), cutaneous leishmaniasis (CL) and mucocutaneous leishmaniasis (MCL), of which VL is the most severe form of the disease. VL is lethal if untreated and spontaneous cure is extremely rare. Cutaneous leishmaniasis usually has milder course and often results into a self-healing of ulcers. Resolution of leishmanial infection is dependent on the coordinated interactions between components of cell mediated immune response, specifically the activation of targeted T-cell populations for appropriate cytokine production and activation of macrophages. L. major infection of B6 and BALB/c mouse strains drives predominantly TH1 and TH2 responses, respectively [11-14]. In murine model, the development of Th1 response is associated with control of infection, and Th2 response is associated with disease progression. However, Th1 and Th2 dichotomy in the human system is not as distinct as in mice and the murine model does not strictly apply to human leishmaniasis.
    • 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.