Now showing items 21-40 of 609

    • Use of a Functional Chewing Gum in Reduction of Gingival Inflammation

      Merati, Arash; Shiau, Harlan (2020)
      Control of plaque biofilm is central to prevention of gingivitis. In addition to professional care, effective oral hygiene measures are known to improve gingival health. The objective of this study was to investigate the effect of chitosan/blackberry-extract, delivered in a chewing gum, as an adjunct to oral hygiene, on gingival inflammation and plaque biofilm accumulation. In this 12-week randomized controlled study, the use of chitosan/blackberry-extract gum was compared to placebo in 34 subjects (17/17). Plaque index(mPI) and gingival index(mGI) were the main outcome measures followed at baseline, week 2, 4, 8, and 12. Measured patient compliance and mPI had no significant difference between experimental and control at any interval during the study. mGI was significantly lower for the experimental group compared to control at 12 weeks(P<0.005). Chitosan/blackberry-extract chewing gum may be beneficial in reduction of clinical signs of gingival inflammation and has potential as an adjunct to routine oral hygiene.
    • The Accuracy and Efficiency of a Dynamic 3D Navigation System for Negotiating Calcified Canals

      dianat, omid; Chand, Priya (2020)
      The purpose of this study is to compare the use of a dynamic navigation system (DNS) to a freehand (FH) method for locating calcified canals. Sixty single-rooted teeth with obliterations were selected. In the DNS group, access preparation was made under navigation and in the FH group without any guidance. Linear and angular deviations and reduced dentin thickness were measured. Furthermore, efficiency was evaluated. The mean linear and angular measurements showed significantly less deviations in the DNS group compared to the FH group. Reduced dentin thickness, at both levels, was significantly less in the DNS group. Furthermore, DNS was faster and more successful than FH method. The DNS group showed only one unsuccessful attempt, compared to five perforations and three large transportations in the FH group. Within the limitation of this study, the dynamic navigation system allowed for more accurate and efficient negotiation of the calcified root canal system.
    • Tongue Position in Glossectomy Patients vs. Controls in /s/ during Speech with consideration for the effects of Palatal Features

      Rezaei Boroun, Atefeh; Stone, Maureen L. (2020)
      Purpose: This study examines the tongue behavior of glossectomy (N = 8) and control (N =12) speakers using a combination of high-resolution and cine- MRI. The speech task “a geese” phonetically spelled /əgis/, was used to measure anterior tongue displacement, termed “anteriority”, for the /ə/, a neutral vowel, and the /s/. Effects on anteriority due to palate height, arch perimeter, inter-canine width and /s/ type were measured on controls and patients. There are two variants of /s/ in English: apical and laminal. The apical /s/ elevates the tongue tip to contact the palate, create a narrow, grooved constriction, and focus the jet stream of air onto the incisors. The laminal /s/ uses the tongue blade, just behind the tip, to create the grooved constriction, and the tip is kept lower in the mouth.[1, 2]
    • Variation in Accessory Branches of the Mylohyoid Nerve in the Posterior Mandible: An Anatomic Study

      Ottey, Elizabeth Alston; Stone, Maureen L. (2020)
      Purpose: To examine the courses and branching patterns of the mylohyoid nerve in adult cadavers in order to determine if there are accessory branches, which insert on the posterior mandible. Materials and Methods: 25 cadavers preserved in 10% formalin were dissected in the gross anatomy dissection lab. The mylohyoid and any varying branches were dissected and preserved as far as possible. The dissected cadaver’s data sets were analyzed using Image J software. Results: 12 out 25 (48%) cadavers had at least one accessory branch present that attached to the posterior mandible. The accessory branch identified was located an average of 2.3 cm from the posterior mandible. Conclusion: Accessory branches of the mylohyoid exist in the posterior mandible. Our next step is testing the identified branches to confirm if they are nerve fibers.
    • Accuracy of Dynamic Virtual Articulation: Trueness and Precision

      Hsu, Michael; Masri, Radi, 1975- (2020)
      Purpose: To study the effects of altering condylar settings and pin openings on the trueness and precision of virtual articulators versus mechanical articulators. Materials and Methods: Maxillary and mandibular typodonts with fiducial markers were mounted on a mechanical Artex-CR articulator and the mandibular teeth were prepared to allow guidance solely by the posterior determinants of the articulator and the incisal table. The relationship of the mounted typodonts was preserved digitally by scanning using manufacturer transfer plate adaptors. On the mechanical articulator, pattern resin was allowed to set between the maxillary and mandibular occlusal surfaces (area #25-30) at the endpoints of dynamic movements at three different condylar inclinations (SCI): 10°, 30°, and 45°, n=12/inclination, or at three different incisal pin openings (2, 5, and 10 mm, n=12/opening). All other articulator settings were kept constant. Resin specimens attached to the typodonts were scanned within five minutes of setting, then removed and the articulated typodonts rescanned. FDPs #25-30 were designed on the virtual articulator using identical parameters to the mechanical articulator. Dynamic virtual movements were used to sculpt the design and a file of the design was saved. The files of both types of samples were aligned and overlaid. Interocclusal separation was measured in triplicate at the indentation created by the mesiolabioincisal point angle on the incisal edge of #8 and the mesiobucco-occlusal point angle of #3. Trueness and precision of both types of articulators were calculated and compared using one-way ANOVA, followed by the Tukey HSD test (α=.05). Results: There was no statistically significant difference at altered pin openings in either trueness (F<.202, p>.37) or precision (F<3.134, p>.09) for the majority of measurements. The only significant difference was in the precision between the two types of articulators at 5mm incisal opening, and only at the anterior measurement point (F=15.134, p=.0008). However, these differences were less than 100 μm. When the SCI was altered, there was no statistically significant difference (F< 3.624, p>.05) between the virtual and mechanical articulators in trueness for 5 of the 6 measurements obtained (F<3.624, p>.07) or for all of the precision measurements (F<3.529, p>.07). The one trueness measurement that was significantly different (F=9.237, p=.006 ) occurs at SCI of 10º, and it was less than 100 μm. Conclusions: Dynamic movements on the virtual articulator were shown to be as true and precise as to the mechanical articulator. When there were deviations, these deviations were less than 100 μm and thus, these deviations may not be clinically relevant.
    • The effect of delayed curing time of a self-etch primer on shear bond strength of the orthodontic bracket

      Lee, Hyun San; Schneider, Monica, D.D.S., M.S. (2020)
      This study investigated if a delay in curing time of a self-etching primer (SEP) affects the shear bond strength (SBS) of orthodontic brackets and the Adhesive Remnant Index (ARI) score. In 2-Step group, the conventional two-step technique was used for enamel conditioning. In groups Delay0, Delay1, and Delay5, a SEP was used with various delays in curing time (0, 1, and 5 minutes). Stainless steel brackets were bonded to the specimens using composite resin adhesive and were tested for SBS. Then ARI scores were measured under naked eye, 2.5x, and 10x magnifications. The results showed no significant difference in mean SBS and the ARI scores between the SEP technique and the two-step technique. The findings also implied a delay up to 5 minutes in SEP curing time do not affect the SBS and ARI scores. Finally, there was no difference in the ARI scores measured under three levels of magnification.
    • Comparison of Setting Expansion of White MTA and Endosequence Root Repair Material Putty Fast Set

      Ghiasi Afjeh, Seyedeh Pegah; Chand, Priya (2020)
      The purpose of root end filling material in endodontic surgery is to provide a seal to prevent the ingress and egress of bacterial toxins into the periapical area. One reason for the sealing ability of these materials is their expansion upon setting. The aim of this study was to compare the percent linear setting expansion of WMTA and ERRM putty fast set using a linear voltage displacement transducer (LVDT) under controlled temperature of 37° Celsius. Materials were prepared according to the manufacturer’s instructions and packed into the hollow hydrophilic porous tubing. Approximately 200 µL of HBSS was added to the porous tube in order to initiate the setting reaction. Expansion changes were measured until it appeared to have plateaued. ERRM putty showed a significantly greater mean percent expansion compared to the MTA (P≤0.005). MTA expanded an average of 0.109% (0.08%-0.20%) while ERRM putty expanded an average of 6.63% (2.93%-8.89%).
    • Metformin Induces Pro-angiogenic Responses in Dental Pulp Stem Cells: Potential Applications in Craniofacial Bone Regeneration

      Ge, Sheng; Schneider, Abraham (2020)
      The present study was conducted to determine whether metformin, a low-cost drug widely prescribed to control type 2 diabetes mellitus, stimulates production of angiogenic factors to potentially enhance vascularization of dental pulp stem cell (DPSC)-based craniofacial tissue engineered bone. Bone tissue engineering utilizing stem cells, growth factors and scaffolds offer an attractive alternative for regenerating large craniofacial osseous defects versus autologous bone grafts. Yet, successful stem cell-based bone regeneration highly depends on proper adaptation of cells to hypoxia and reestablishment of a functional microvasculature. Recent reports show that metformin induces DPSC’s osteogenic differentiation; however, it remains unknown whether metformin stimulates DPSC-derived, pro-angiogenic responses to support bone regeneration. We found that metformin induced a marked but variable increase in DPSC-derived angiogenic factors, including VEGF and angiogenin, which were further amplified by hypoxia. These results point to a novel, pro-angiogenic action of metformin to potentially enhance DPSC-based vascularized craniofacial skeletal regeneration.
    • Prevalence of Atypical Radiographic Findings in Bitewings of Class II Composite Restorations: Detection and Assessment of Radiolucent Areas

      Bazerbashi, Jood; Melo, Mary Anne (2020)
      This retrospective study aimed to describe the prevalence of radiographic abnormalities in bitewing radiographs of proximal class II composite restorations. Bitewing radiographs of proximal composite restorations of adult patients who underwent restorative care at predoctoral clinics at the University of Maryland School of Dentistry from August 2014 to July 2016 were identified. Atypical radiographic features were categorized by type of material and location. The information recorded for patients included age, sex, tooth, and restored surface. Out of the 669 examined restorations, 16.5% radiographs showed no atypical radiographic findings and 83.5% restorations had unusual radiographic signs. The types of atypical radiographic findings were distributed as 16.5% internal voids, 3% overhang, 7.8% interlayer lines, 12.6% secondary caries, 20.7% interfacial gaps and 23.1% had multiple atypical findings. There is high prevalence of atypical radiographic findings in class II composite restorations, particularly in the body of the composite, premolars, and disto-occlusal restorations.
    • Role of Lipopolysaccharide and RANKL in Osteoclastogenesis: Potential Inhibitory Effects of C-Phycocyanin on the Respective Molecular Pathways of Osteoclastogenesis

      Al Qranei, Mohammed; Chellaiah, Meenakshi A. (2020)
      Many skeletal diseases are characterized by excessive bone loss. Bone loss is mediated by osteoclasts, which are differentiated from cells of the monocyte/macrophage lineage upon stimulation of two indispensable factors, the RANKL and M-CSF. Lipopolysaccharide (LPS), a bacterial pathogenic factor, has also been shown to engage in osteoclastogenesis during inflammatory events actively. C-phycocyanin (C-PC) is a phycobiliprotein found in the blue-green algae that showed many therapeutic effects, including anti-arthritic and anti-inflammatory properties. However, the exact mechanism by which LPS regulates osteoclastogenesis and also the impact of C-PC on osteoclastogenesis needs further elucidations. We studied the osteoclast differentiation process in vitro using RAW 264.7 macrophage cell line. First, we showed that LPS induced osteoclastogenesis in RANKL-primed cells in vitro. LPS elicited osteoclastogenic mechanism by signaling through the TLR4 receptor, which is expressed in osteoclast precursors. Here we also found that TNF-α secreted by osteoclast precursors in response to TLR4 stimulation regulated the processes of osteoclastogenesis via TNF-R signaling. Second, we tested the inhibitory effect of C-PC on osteoclastogenesis. We showed here that C-PC strongly inhibited the early stage of osteoclast differentiation, thus significantly suppressing RANKL- and LPS- mediated osteoclastogenesis. Nonetheless, osteoblast differentiation and activity were not affected by C-PC. Reactive oxygen species (ROS) are generated during RANKL-mediated osteoclast differentiation. While studying the possible mechanisms of osteoclast differentiation, we found that C-PC a) attenuated RANKL-induced ROS; and b) interfered with RANKL-stimulated NF-κB signaling by preventing the degradation of cytosolic IκB-α; subsequently, these resulted in the loss of sequential activation of the osteoclastogenic downstream markers such as c-Fos and NFATc1. We propose that a unique mechanism of osteoclastogenesis is mediated by bacterial LPS that can be targeted during inflammatory-mediated bone loss. Also, C-PC could potentially be used as a therapeutic compound in osteolytic diseases caused by osteoclast activation without affecting osteoblast function.
    • Methylsulfonylmethane: Possible Role in Bone Remodeling

      Aljohani, Hanan; Chellaiah, Meenakshi A. (2020)
      Methylsulfonylmethane (MSM) is a popular dietary supplement to assist with various conditions. The anti-inflammatory and osteogenic capabilities of MSM makes it an excellent material for inducing bone formation and promoting osteointegration. MSM is a non-toxic, naturally occurring sulfur-containing compound. This thesis investigated the effect of MSM on osteogenesis in vitro and in vivo. We first used oral stem cells derived from the human exfoliated deciduous teeth (SHED) to elucidate the effect of MSM on osteogenic differentiation using MC3T3-E1 and UMR-106 cells as positive controls. MSM reproduced the results of the osteogenic medium in the osteogenic differentiation of SHED cells. Osteogenic differentiation of SHED cells was determined by an increase in the expression of differentiation markers such as osterix, RUNX2, osteopontin (OPN), and collagen type 1 (Col 1), at both mRNA and protein levels. Moreover, MSM increased the activity of the alkaline phosphatase enzyme, which is vital in the maturation of the extracellular matrix and the formation of mineralized nodules. Very interestingly, the addition of mineralized bone particles enhanced the MSM’s effect on mineralization compared with MSM alone or MSM with demineralized bone particles. Therefore, MSM can act as a cost-effective osteoinductive material for reinforcing bone regeneration. Secondly, we determined the role of transglutaminase-2 (TG2) enzyme in the calcification process via cross-linking of matrix proteins. TG2 is a multifunctional enzyme implicated in matrix stabilization and maturation. MSM treated SHED cells showed a time-dependent increase in TG2 protein expression from 7 to 21 days. Furthermore, immunoprecipitation and immunostaining analyses showed an increase in TG2 colocalization with two prominent osteogenic markers (OPN, Col 1) in a time- dependent manner. An inhibitor to TG2 reduced not only the differentiation of SHED cells but also the mineralization processes by reducing the interaction of TG2 with OPN and Col 1. Our studies demonstrated the effect of MSM on osteogenesis in vitro in TG2 mediated cross-linking of matrix proteins. Thirdly, we identified the effect of MSM on osteogenesis in vivo using aging mice model. We injected aging C57BL/6 female mice (36 weeks old) subcutaneously with MSM and PBS for 13 weeks. Micro-computed tomography (Micro-CT), histological, and immunohistochemistry analyses were done extensively in the bone sections of mandibles isolated from aging mice injected with PBS and MSM. Comparative studies were also done in the tibial and femoral bones of long bones. An increase in the mandibular bone density at the inter-radicular area was observed in mice injected with MSM. The increase was either little or not seen in the femoral or tibial bones analyzed by Micro-CT or in bone sections stained with H&E and TRAP-stains. Immunohistochemistry analyses demonstrated an increase in osteocalcin (OCN) staining in osteoblast-like cells and a decrease in CD105, which is a marker for stem cells. Additionally, we found that MSM has an osteogenic effect via not only increasing the osteogenesis potential of osteoblast- like cells but also the differentiation potential of stem cells into osteoblast-like cells. More experiments are needed to further confirm whether the increase in bone density is a result of the induction of bone formation by osteoblasts or reduction of bone resorption by osteoclasts. MSM is a sulfur-containing non-toxic natural nutrient found in small quantities in many foods. It is commonly used as a supplement to treat arthritis and other inflammatory conditions. This is the first study to show the in vivo effect of MSM on bone remodeling in an aging mice model. We trust, our results may ultimately impact the treatment of other bone loss-associated diseases, including rheumatoid arthritis and periodontitis, which share several pathologic features with osteoporosis.
    • Commencement 2020

      Jarrell, Bruce E.; Hogan, Larry J., 1956-; Perman, Jay A.; Yang, Shi (Porter); Phelan, Mary T. (2020-05)
    • Prospective Clinical Investigation of Orthodontic Relapse from Gingival Clefts

      Scott, Christopher Jason; Stappert, Dina (2018)
      Background: Orthodontic space closure following premolar extraction may result in gingival cleft formation. This may contribute to orthodontic relapse due to reopening of extraction spaces. Aim: 1) To evaluate the effects gingival clefts have on relapse and opening of closed extraction spaces after orthodontic treatment. 2) To record any changes in cleft severity. 3) To establish any relationship between gingival phenotype and cleft severity. Methods: Subjects recruited from previous study in which the occurrence and severity of gingival clefts were measured during space closure. The clinical measures included the occurrence and severity of clefts and their relationship to gingival phenotype. Results: Sites with a cleft (N=42) had 42.86% relapse and those without (N=19) had 36.84% relapse. Conclusions: As cleft severity increases; the amount of relapse distance is likely to increase. Adult patients are at greater risk for relapse at extraction sites compared to adolescent patients.
    • Observational Study Evaluating Pain in Endodontic Patients Diagnosed with Depression – A Pilot Study

      Mannan, Saurabh; Greenspan, Joel D. (2019)
      TITLE: Observational Study Evaluating Pain in Endodontic Patients Diagnosed with Depression – A Pilot Study Saurabh Mannan, Master of Science 2019 Thesis Directed By: Joel Greenspan, PhD AIM: To evaluate the role of depression in endodontic post-procedural pain METHODOLOGY: This prospective observational study enrolled 42 patients that explored the correlation between patient’s level of depression and pain perception following non-surgical root canal treatment (NSRCT). The Hospital Anxiety and Depression Scale (HADS) assessed the patient’s level of anxiety/depression pre-and postoperatively. The patient used a visual analog scale (VAS) to record their pain intensity and feelings of unpleasantness with their dental experience immediately following their NSRCT. Pain diaries recorded pain intensity post-operatively at the 2nd, 4th, and 7th day. A cohort of endodontic patients who were not diagnosed with depression served as controls. RESULT: A total of 41 patients were included, 30 non-depressed patients and 11 patients diagnosed with depression by their physicians. Two patients did not return the pain dairy. Therefore, data from 29 non-depressed patients and ten depressed patients were available for analysis. This study showed that the diagnosis of depression was significantly associated with both higher immediate post-operative pain and immediate sensations of unpleasantness. Furthermore, HADS ≥ 8 was found to be a significant predictor of greater post-operative pain at day two. CONCLUSIONS: Within the limitations of this study, either a diagnosis of depression or signs of anxiety or depression are a positive predictor of greater post-operative pain.
    • The Diagnostic Utility of Cancer Stem Cell Marker CD44 in Early Detection of Oral Cancer

      Alsalem, Bader; Meiller, Timothy F. (2019)
      The incidence of Oral Squamous Cell Carcinoma (OSCC) is expected to increase in the coming decades. In recent years, cancer biomarkers have emerged as a promising diagnostic and prognostic tool for various cancers. The cluster differentiation antigen (CD44) is among the most frequently identified cancer stem cell markers in solid tumors. Using immunohistochemistry labeling in previously diagnosed specimens, we aimed to analyze the utility of CD44 in early diagnosis of OSCC. Biopsy specimen subgroups of lateroventral tongue revealed an increased proportion of cells staining positive for CD44 in the epithelial samples of OSCC compared with erosive lichen planus and oral dysplastic lesions. CD44, in combination with other oral biomarkers, therefore, has the potential to assist in the early diagnosis of OSCC. Future studies with larger sample sizes and multiple biomarkers should be carried out, utilizing a pre-determined IHC staining and interpretation strategy to promote reproducibility of evidence.
    • Development of Novel Nanostructured Therapeutic Root Canal Dental Sealers with Strong Antibacterial and Remineralization Capabilities

      Baras, Bashayer Hussain; Xu, Huakun H. (2019)
      Root canal therapy aims to remove microorganism or at least reduce them to subcritical levels that permit the host’s immunity to eliminate infection and regenerate damaged tissues. However, due to the complex and variable root canal anatomy and the resistant nature of root canal biofilm, complete elimination of root canal microorganisms is rarely accomplished. In addition, it has been frequently reported that some of the most commonly used irrigating solutions, such as, sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) can adversely alter the chemical and mechanical properties of dentin, resulting in a brittle dentin structure that is more susceptible to root fracture. This dissertation aims to develop a therapeutic root canal sealing material with potent antibacterial properties and remineralizaition capabilities through the incorporation of dimethylaminohexadecyl methacrylate (DMAHDM) to provide bacterial contact killing in case of micro leakage, nanoparticles of silver ions (NAg) to eliminate bacteria in the more complex root canal anatomy through release of silver ions, and nanoparticles of amorphous calcium and phosphate (NACP) to reverse the action of NaOCl and EDTA on root dentin and strengthen the root structure through the release of Ca and P ions. In this dissertation projects, the effects of incorporating DMAHDM, NAg, and NACP on the physical and sealing properties were evaluated. The antibiofilm properties were assessed by polysaccharide production, live/dead, and colony-forming units (CFU) assays. The antibiofilm properties of the developed sealer were assessed on cured sealer disks and utilizing a human dentin model. In addition, the effects of NACP on the Ca and P ion release, pH-alkalizing properties, and influence on dentin hardness were all measured. The triple incorporation of DMAHDM, NAg, and NACP did not compromise the physical properties of the root canal sealer and demonstrated sealing properties that were similar to that of a commercial control material. The incorporation of DMAHDM and NAg alone into the root canal sealer demonstrated great reductions in bacterial viability and quantity. However, when both agents were combined the antibiofilm effects were maximized, resulting in CFU reductions of 6 orders of magnitude. The DMAHDM NAg containing root canal sealer was able to kill bacteria not only on the surface of resin disks but also bacteria impregnated inside human dentin. The incorporation of NACP into the respective sealer allowed for the release of high levels of Ca and P ions, neutralized the acid and increased the solution pH, and increased the dentin hardness to match that of sound dentin. This bioactive antibacterial and remineralizing root canal sealer is promising to prevent endodontic treatment failure and secondary endodontic infections while releasing high levels of Ca and P ions that could remineralize and strengthen the tooth structures and potentially prevent future root fractures and teeth extractions.
    • In Vitro and in Vivo Characterization of Candida albicans and Streptococcus mutans Interactions

      Khoury, Zaid; Jabra-Rizk, Mary Ann; 0000-0001-9596-3560 (2019)
      The oral cavity is a complex environment harboring diverse microbial species that often co-exist within biofilms formed on oral surfaces. Within a biofilm, inter species interactions can be synergistic in that the presence of one organism generates a niche for another enhancing colonization. Among these species are the opportunistic fungal pathogen Candida albicans and the bacterial species Streptococcus mutans, the causative microorganisms strongly linked to the development of oral candidiasis and dental caries, respectively. Recent studies have reported the enhanced prevalence of C. albicans in children with early childhood caries indicating that this fungal-bacterial interaction may have clinical implications. In this study, we aimed to elucidate and characterize this interaction between these diverse species. Specifically, we designed in vitro and in vivo studies to validate the hypothesis that the presence of C. albicans in the oral cavity augments S. mutans colonization, potentially mediating dental caries development. Using various C. albicans mutant strains and a GFP-tagged S. mutans, metabolic viability and fluorescent biofilm assays were performed to assess S. mutans recovery from mixed biofilms and to elucidate the mechanisms of interactions. Additionally, to visualize the architecture of formed biofilms, confocal scanning laser fluorescent and electron scanning microscopy were used. Importantly, a clinically relevant mouse model of oral co-infection was developed to demonstrate C. albicans mediated enhanced S. mutans colonization in a host. The findings demonstrated significantly higher recovery of S. mutans from biofilms with C. albicans in vitro. Images revealed a high bacterial affinity to C. albicans, and secreted fungal cell wall polysaccharides were identified as the key factor mediating biofilm formation, particularly mannans. Importantly, analyses of harvested tissue demonstrated significantly higher S. mutans recovery from teeth of co-infected mice compared to mice infected only with S. mutans. Collectively, the findings strongly indicate that the presence of C. albicans in the oral environment may impact the development of dental caries and should be considered as a factor in evaluating the risk of caries. Results obtained in this thesis will support future studies using animal models of dental caries to further characterize this relationship in a closely related model in our laboratory.
    • University of Maryland School of Dentistry Strategic Plan 2017-2021

      University of Maryland, Baltimore. School of Dentistry (2017)