• Accelerated Calvarial Healing in Mice Lacking Toll-Like Receptor 4

      Wang, Dan; Gilbert, James R.; Cray, James J. Jr; Kubala, Adam A.; Shaw, Melissa A.; Billiar, Timothy R.; Cooper, Gregory M.; Department of Oral Biology; Department of Orthodontics (2012-10-10)
      The bone and immune systems are closely interconnected. The immediate inflammatory response after fracture is known to trigger a healing cascade which plays an important role in bone repair. Toll-like receptor 4 (TLR4) is a member of a highly conserved receptor family and is a critical activator of the innate immune response after tissue injury. TLR4 signaling has been shown to regulate the systemic inflammatory response induced by exposed bone components during long-bone fracture. Here we tested the hypothesis that TLR4 activation affects the healing of calvarial defects. A 1.8 mm diameter calvarial defect was created in wild-type (WT) and TLR4 knockout (TLR4-/-) mice. Bone healing was tested using radiographic, histologic and gene expression analyses. Radiographic and histomorphometric analyses revealed that calvarial healing was accelerated in TLR4-/- mice. More bone was observed in TLR4-/- mice compared to WT mice at postoperative days 7 and 14, although comparable healing was achieved in both groups by day 21. Bone remodeling was detected in both groups on postoperative day 28. In TLR4-/- mice compared to WT mice, gene expression analysis revealed that higher expression levels of IL-1b, IL-6, TNF-a,TGF-b1, TGF-b3, PDGF and RANKL and lower expression level of RANK were detected at earlier time points (# postoperative 4 days); while higher expression levels of IL-1b and lower expression levels of VEGF, RANK, RANKL and OPG were detected at late time points (. postoperative 4 days). This study provides evidence of accelerated bone healing in TLR4-/- mice with earlier and higher expression of inflammatory cytokines and with increased osteoclastic activity. Further work is required to determine if this is due to inflammation driven by TLR4 activation.
    • Alterations in Articular Cartilage of the Rabbit Mandibular Condyle Following Surgical Induction of Anterior Disc Displacement: Light and Electron Microscopic Immunocytochemistry Using Colloidal Gold Conjugates

      Choi, Won-Seok; Department of Oral Biology (1996-05)
      The purpose of this study was to test the hypothesis that surgical induction of anterior disc displacement (ADD) in the rabbit craniomandibular joints (CMJ) will lead to degenerative osteoarthritic changes detectable a t the molecular, subcellular and cellular levels in the articular cartilage of the rabbit mandibular condyle. Ultrastructural features of the normal rabbit mandibular condyle were compared to those of experimental condyles a t two weeks following induction of ADD. The quantities of type-VI and -IX collagens, as well as the components of proteoglycans, such as chondroitin-4-sulfate (C4S), chondroitin-6-sulfate (C6S), k e ra tan sulfate (KS) and link protein (LP) were measured using immunogold labeling technique at the light and the electron microscopic levels. The right joint of each of 20 rabbits was exposed surgically, and all discal attachments were severed except for th e posterior attachment. The disc was then displaced anteriorly and sutured to the zygomatic arch. The left joint served as a sham -operated control. Ten additional joints were used as non­ operated controls. Deeply anesthetized rabbits were perfused with 2% buffered formalin two weeks after surgery. The mandibular condyles were excised and decalcified in ethylenediam inetetraacetic acid (EDTA). Paraffin embedded tissues were sectioned a t 5 (im for light microscopic study, while water-soluble plastic embedded sections were used for electron microscopy. Sections were incubated in monoclonal antibodies directed against C4S, C6S, KS and LP, and in polyclonal antibodies against type-VI and -IX collagens. After incubation in the appropriate colloidal gold conjugated secondary antibodies, tissue sections were studied with light and electron microscopes. In addition, immunostaining for proliferating cell nuclear antigen (PCNA) was performed using paraffin sections, and the PCNA indices of control and experimental condyles were determined. Pathological alterations were obvious in the experimental condyles, and appeared to be characteristic osteoarthritic changes. These include cartilage neovascularization, chondrocyte clustering, vacuolation, loss of extracellular matrix next to the membranes of chondrocytes, and an increase in num ber of apoptotic chondrocytes. Increased num bers of PCNA-positive cells in the osteoarthritic cartilage of the experimental group indicated a n active chondrocytic proliferation. Ultrastructural changes in injured chondrocytes included increased amounts of RER and Golgi, suggesting an increase in the synthesis and secretion of possibly degradative enzymes with a decrease in the normal secretory products. The results of th e immunocytochemistry using colloidal gold conjugates both a t the light and electron microscopic levels showed statistically significant depletion of C4S, C6S, KS, LP, type-VI collagen and type-IX collagen in the osteoarthritic cartilage (P < 0.05). The reduction of binding molecules such as LP, type-VI and type-IX collagens suggest a possible mechanism for the observed loss of integrity of the extracellular matrix. It is concluded that surgical induction of ADD in the rabbit CMJ leads to molecular, cellular and extracellular alterations in the articular cartilage of the mandibular condyle similar to those described previously in hum an ADD and in osteoarthritis of other synovial joints. The results of this study provide evidence that the loss of the shock absorber function of the disc, and the exposure of the condyles to overloading may cause the injured chondrocytes to secrete degenerative cytokines as indicated by the loss of proteoglycans, binding collagens and LP. These molecular changes are expressed a t the subcellular and cellular levels as osteoarthritis or degenerative joint disease.
    • 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.
    • Caspase-14: A novel caspase in the retina with a potential role in diabetic retinopathy

      Al-Shabrawey, Mohamed; Ahmad, Saif; Megyerdi, Sylvia; Othman, Amira; Baban, Babak; Palenski, Tammy L.; Shin, Eui Seok; Gurel, Zafer; Hsu, Stephen; Sheibani, Nader; et al. (2012-07-14)
      Purpose: The purpose of this study was to evaluate caspase-14 expression in the retina under normal and diabetic conditions, and to determine whether caspase-14 contributes to retinal microvascular cell death under high glucose conditions.
    • Cellular and Immunocytochemical Response to Mandibular Distraction Using an Implanted Lengthening Device

      Elbokle, Nadar N; Department of Oral Biology (2004)
      Distraction osteogenesis (DO) is a biologic process that generates new bone between surfaces of bone segments, which are gradually separated by traction forces. It is a uniquely effective method with multiple applications in the craniofacial region. This concept has been the basis of all bone-lengthening operations; it involved an osteotomy of the shortened bone and an external/internal fixator device, which slowly elongates the bone to its new dimension while a bony callus is being formed at the side to distraction. The biology of DO is similar to callus fracture healing. The bony regenerate passes through the same phases: formation of a collagen fibril template, mineralization, bony union and finally remodeling. The mechanisms by which the mechanical stresses applied to the bone tissue cause the cells to proliferate and form new bone are not well understood. More studies are needed to understand the cellular events underlying DO and the effects of the strains applied during DO on cellular proliferation and mineral apposition.
    • 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.
    • Dentin Sialophosphoprotein (DSPP) Gene-Silencing Inhibits Key Tumorigenic Activities in Human Oral Cancer Cell Line, OSC2

      Joshi, Rajeshree; Tawfik, Amany; Edeh, Nneka; McCloud, Veronica; Looney, Stephen W.; Lewis, Jill; Hsu, Stephen; Ogbureke, Kalu U.E.; Department of Oral Biology; Department of Pathology; et al. (2010-11-12)
      Background: We determined recently that dentin sialophosphoprotein (DSPP), a member of the SIBLING (Small integrin-binding ligand N-linked glycoproteins) family of phosphoglycoproteins, is highly upregulated in human oral squamous cell carcinomas (OSCCs) where upregulation is associated with tumor aggressiveness. To investigate the effects of DSPP-silencing on the tumorigenic profiles of the oral cancer cell line, OSC2, short-hairpin RNA (shRNA) interference was employed to silence DSPP in OSC2 cells.
    • Differential effects of taurine treatment and taurine deficiency on the outcome of renal ischemia reperfusion injury

      Mozaffari, Mahmood S.; Abdelsayed, Rafik; Patel, Champa; Wimborne, Hereward J. C.; Liu, Jun Yao; Schaffer, Stephen W; Department of Oral Biology; Department of Oral Health and Diagnostic Sciences (2010-08-24)
      Taurine possesses membrane stabilization, osmoregulatory and antioxidant properties, aspects of relevance to ischemic injury. We tested the hypothesis that body taurine status is a determinant of renal ischemic injury. Accordingly, renal function and structure were examined in control (C), taurine-treated (TT) and taurine deficient (TD) rats that were subjected to bilateral renal ischemia (60 min) followed by reperfusion (IR); sham operated rats served as controls. Baseline urine osmolality was greater in the TD group than in the control and the TT groups, an effect associated with increased renal aquaporin 2 level. The IR insult reduced urine osmolality (i.e., day-1 post insult); the TD/IR group displayed a more marked recovery in urine osmolality by day-6 post insult than the other two groups. Fluid and sodium excretions were lower in the TD/IR group, suggesting propensity to retention. Histopathological examination revealed the presence of tubular necrotic foci in the C/IR group than sham controls. While renal architecture of the TD/IR group showed features resembling sham controls, the TT/IR group showed dilated tubules, which lacked immunostaining for aquaporin 2, but not 1, suggestive of proximal tubule origin. Finally, assessment of cell proliferation and apoptosis revealed lower proliferation but higher apoptotic foci in the TT/IR group than other IR groups. Collectively, the results indicate that body taurine status is a major determinant of renal IR injury.
    • 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.
    • Effect of b-alanine treatment on mitochondrial taurine level and 5-taurinomethyluridine content

      Jong, Chian Ju; Ito, Takashi; Mozaffari, Mahmood S.; Azuma, Junichi; Schaffer, Stephen W; Department of Oral Biology (2010-08-24)
      Background: The b-amino acid, taurine, is a nutritional requirement in some species. In these species, the depletion of intracellular stores of taurine leads to the development of severe organ dysfunction. The basis underlying these defects is poorly understood, although there is some suggestion that oxidative stress may contribute to the abnormalities. Recent studies indicate that taurine is required for normal mitochondrial protein synthesis and normal electron transport chain activity; it is known that defects in these events can lead to severe mitochondrial oxidative stress. The present study examines the effect of taurine deficiency on the first step of mitochondrial protein synthesis regulation by taurine, namely, the formation of taurinomethyluridine containing tRNA.

      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.
    • Effect of Metformin on Oral Implant Healing in Type 2 Diabetic Rats

      Inouye, Kimberly Ann; Department of Oral Biology (2011-04)
      In dentistry today, endosseous implants have become a generally favorable treatment option for edentulous spaces in the oral cavity because of proven biocompatibility, potential for esthetics, and good long term prognosis.(1) However, there are risk factors to consider that may affect and impair the osseointegration of an implant. A possible risk factor is type 2 diabetes mellitus (T2DM), a metabolic disorder characterized by insulin resistance at the target tissue site and progressive destruction of the pancreatic beta cells that ultimately results in prolonged periods of hyperglycemia.(2) When the serum glucose levels were persistently high, it was shown to impair bone metabolism and thus, has the potential to impair implant osseointegration.(3)
    • The Effect of Nrf2 on Inflammatory Responses of Human Monocytic Cells After Blue Light Exposure

      Trotter, Leigh Ann; Trotter, Leigh Ann; Department of Oral Biology (12-Apr)
      Blue light treatment alters cellular signaling and affects intracellular biochemical processes in tissues. PURPOSE: This study determined the ability of blue light to modulate Nrf2 and decrease LPS-induced secretion of pro-inflammatory cytokines from cultured, human monocytic cells. METHODS: Cultured THP-1 human monocytic cells were exposed to LPS and blue light treatment. Western Blot analyses, EMSA, and ELISA were used to evaluate NF?B, Nrf2, HO-1, TNF-?, IL-6 and IL-8 production. RESULTS: Light treatment increased nuclear Nrf2 and increased HO-1. Cells pretreated with light had no detectable NF?B-DNA binding. LPS treatment increased nuclear NF?B, and had little effect on Nrf2. Light pre-treatment significantly decreased the amount of TNF-? by 63% and IL-8 by 55%. CONCLUSIONS: Blue light increases the production of Nrf2 and HO-1, decreases the ability of Nf?B to bind in the nucleus, and leads to a decrease in the secretion of pro-inflammatory proteins in human monocytic cells.
    • 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.
    • The Effect of Solvent Type and Content on Monomer Conversion of a Model Resin System and 5th Generation Dentin Bonding Agents

      Holmes, Robert G.; Department of Oral Biology (2006-05)
      Fifth generation dentin bonding agents contain a variety of solvents. These solvents have a range of evaporation rates, which leads to differing amounts of residual solvent remaining at time of cure. Residual solvent could affect resin polymerization, and thus resultant properties of the bonded resin/dentin interface.
    • The effects of altered salivary viscosity on the incidence and extent of dental caries in rats

      Biesbrock, Aaron Reed; Department of Oral Pathology (Augusta University, 1989-05-02)
      The research was intended to determine whether alterations in salivary viscosity brought about by altering dietary components affected the incidence and extent of dental caries in rats.