Now showing items 1-20 of 620

    • Same Goal, Different Paths: NIH and a Recipient Organization Talk about Grants

      Hoffman, William F., Jr.; Levin, Elenora; Pettitt, Debbie; Simons, Janet, M.B.A. (2022)
    • Toluidine Blue Ortho @ Magnetic Photosensitizing Nanoplatform: Antibiofilm Effect against Thick Constant-depth-film-fermenter Biofilms

      Balhaddad, Abdulrahman A.; Mokeem, Lamia S.; Weir1, Michael D.; Xu, Hockin H. K.; Melo, Mary Anne S. (2022-04-27)
    • Efficient Bacteria Killing by Dental Adhesives with Benzyldimethyldodecylammonium Chloride

      Mokeem, Lamia S.; Balhaddad, AbdulRahman A.; Melo, Mary Anne S. (2022-04-27)
    • Dentin Bonding Evaluation To Identify Quaternary Ammonium Concentration For Antibacterial Adhesive Formulations

      Mokeem, Lamia S.; Balhaddad, AbdulRahman A.; Melo, Mary Anne S. (2022-03-04)
    • Long-Term Post-COVID-19 Associated Oral Inflammatory Sequelae

      Alfaifi, Areej; Sultan, Ahmed S.; Montelongo-Jauregui, Daniel; Meiller, Timothy F.; Jabra-Rizk, Mary Ann (2022-03-04)
      The oral cavity remains an underappreciated site for SARS-CoV-2 infection despite the myriad oral conditions observed in COVID-19 patients. Recently, replicating SARS-CoV-2 was found inside salivary epithelial cells resulting in inflammation and atrophy of salivary glands. Saliva possesses healing properties crucial for maintaining the health of the oral mucosa. Specifically, salivary antimicrobial peptides, most notable, histatin-5 exclusively produced in salivary glands, plays a vital role in innate immunity against colonizing microbial species. The demonstration of SARS-CoV-2 destruction of gland tissue where histatin-5 is produced strongly indicate that histatin-5 production is compromised due to COVID-19. Here we present a case of a patient presenting with the patient and matched healthy subject for histatin-5 and key cytokines. Findings demonstrated significantly reduced histatin-5 levels in patient’s saliva and activation of the Th17 inflammatory pathway. As histatin-5 exhibits potent activity against the opportunistic oral pathogen Candida albicans, we evaluated saliva potency against C. albicans ex vivo. Compared to control, patient saliva exhibited significantly reduced anti-candidal efficacy. Although speculative, based on history and salivary analysis we hypothesize that salivary histatin-5 production may be compromised due to SARS-CoV-2 mediated salivary gland destruction. With the current lack of emphasis on implications of COVID-19 on oral health, this report may provide lacking mechanistic insights that may lead to reassessment of risks for oral opportunistic infections and mucosal inflammatory processes in acutely-ill and recovered COVID-19 patients.
    • Nanotechnology-Based Dental Materials for Root Caries Management: Design Concepts and Advanced Strategies to Modulate Dysbiotic Patient-derived Oral Biofilms

      Balhaddad, Abdulrahman Abubaker; Melo, Mary Anne; Xu, Huakun H.; 0000-0001-6678-7940 (2021)
      The distinctive challenges associated with root caries demand innovative interventions to preserve the tooth structure and surrounding soft tissues. This dissertation is composed of a set of manuscripts aiming to advance the anti-biofilm approaches to prevent root caries from two perspectives: (i) invasive approach via novel bioactive resin composites, and (ii) non-invasive approach via magnetic field-guided antimicrobial photodynamic therapy (MF-aPDT). The first chapter provided a general introduction concerning the clinical burden of root caries, current treatment modalities, and their limitations. In the second chapter, I provided an overview of contact-killing monomers and bioactive fillers in restorative dentistry. Then, in chapter three, we developed bioactive resin composite formulations containing dimethylaminohexadecyl methacrylate (DMAHDM) antibacterial monomer and 20% nano-sized amorphous calcium phosphate (NACP) and subjected them to a series of mechanical/physical tests and antibacterial assays. We found that the DMAHDM-NACP resin composites were associated with a potent antibacterial action against cariogenic and periodontal biofilms, as 2 to 6-log reduction was observed. Other virulence factors, as lactic acid production, and polysaccharide production, were also reduced. The mechanical properties, physical characteristics, surface features, and polymerization behavior were comparable to the commercial control at baseline testing and after one year of aging. We concluded that the designed bioactive formulations might present a pathway to preven recurrent caries and the onset of periodontal diseases around dental restorations. In chapter four, we reviewed the most recent updates related to the implementation of nanotechnology to enhance antimicrobial photodynamic therapy (aPDT). Then, in chapter five, we investigated the impact of encapsulating superparamagnetic iron oxide nanoparticles (SPIONs) and toluidine blue ortho (TBO) inside a microemulsion, named MagTBO, to enhance the TBO’s penetration and antibacterial action against S. mutans and saliva-derived biofilms. Besides, the ability of magnetic field (MF) navigation to serve as a biofilm penetration strategy was also investigated. The MagTBO microemulsions were synthesized successfully and demonstrated excellent biocompatibility and thermodynamic stabilities. Furthermore, the MagTBO microemulsions demonstrated more remarkable and significant antibacterial action than conventional aPDT, especially when the MF is applied. Thus, this approach can be an adjunctive technique to control dental caries and other oral diseases.
    • Novel Dental Nanocomposites with Low-Shrinkage-Stress, Ion Recharge, Antibacterial and Remineralization Capabilities to Protect Tooth Structures

      Bhadila, Ghalia Yaseen; Xu, Huakun H.; Weir, Michael D.; 0000-0002-7361-9221 (2021)
      The objectives of this dissertation were to: (1) investigate a bioactive nanocomposite with strong antibacterial and ion-recharge capabilities containing dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and evaluate long-term Ca and P ion recharge by testing for 12 cycles of recharge and release; (2) develop a low-shrinkage-stress (LSS) nanocomposite with antibacterial and remineralization capabilities through the incorporation of DMAHDM and NACP to reduce marginal enamel and dentin demineralization under recurrent caries biofilm-model; (3) investigate the effects of the new composite on biofilm inhibition, mechanical properties, shrinkage stress, degree of conversion, and Ca and P ion releases; and (4) investigate the cytotoxicity of the new LSS composite and its monomers in vitro. For the antibacterial and rechargeable nanocomposite, biofilm lactic acid and colony-forming units (CFU) were measured. Ion recharge was tested for 12 cycles. For the LSS antibacterial and remineralizing nanocomposite, mechanical properties, shrinkage stress, and degree of conversion were evaluated. The growth of Streptococcus mutans and multi-species salivary biofilms was assessed using biofilm CFU, lactic acid production, and confocal laser scanning microscopy. Ca and P ion releases, and human gingival fibroblasts cytotoxicity were measured. The bioactive rechargeable nanocomposite reduced biofilm acid production and viability. High levels of ion releases were maintained throughout 12 cycles of recharge, maintaining steady-state releases without reduction in 6 months, representing long-term remineralization potential. The LSS composite with DMAHDM and NACP had flexural strength matching that of a commercial control composite. The bioactive low-shrinkage-stress composite substantially reduced the biofilm CFU and lactic acid production compared to control composite. The bioactive LSS composite exhibited no significant difference in antibacterial performance before and after three months of aging, demonstrating long-term antibacterial activity. The shrinkage stress of the bioactive low-shrinkage-stress nanocomposite was 36% lower than that of traditional control composite, with similar degrees of conversion. The new bioactive nanocomposite had a satisfactorily low cytotoxic effect toward human gingival fibroblasts and the new monomers had fibroblast viability similar to that of commercial control. The two developed nanocomposites are promising to inhibit recurrent caries and protect the teeth with an intended application for reducing recurrent caries.
    • Design, Development and Assessment of Dental Sealants with Anti-caries Functionalities Using Bimodal Agents

      Salem Ibrahim, Maria; Melo, Mary Anne; Xu, Huakun H. (2019)
      Dental caries presents a high prevalence worldwide despite the availability of various prophylactic means, including the daily use of fluoride toothpaste, water fluoridation, dental sealants, oral health educational programs, and various mouth-rinses. Dental sealants were introduced to prevent dental caries in the pits and fissures of the occlusal surfaces. Sealants act as a physical barrier to prevent food accumulation in the pits and fissures. The current evidence suggests that sealing the occlusal surfaces of permanent molars in children and adolescents reduces caries up to 24 months when compared to no sealant. However, epidemiologic findings have shown an increase in sealant failures with increasing caries risk status due to biofilm accumulation at the sealant-tooth interface with further caries development. Thus, there is a need to develop new approaches to improve oral health care and decrease dental caries through the suppression of cariogenic biofilm formation in the sealant-tooth interface and dental materials surfaces. We proposed the development of novel dental resin-based sealant formulations with anti-caries functionalities intended to prevent caries development or progression. The sealing formulations contain two biointeractive agents; nano amorphous calcium phosphate (NACP) dimethylaminohexadecyl methacrylate (DMAHDM), a promising antibacterial monomer. The role of NACP content as a source of localized calcium and phosphate ions release delivered from a dental material for sealant applications and its combined use with the antibacterial monomer, DMAHDM, to impair anti-biofilm function were investigated. We comprehensively assessed the newly-designed formulations using in vitro biofilm models and analytical testing to investigate the potential biological effects of these novel materials on human enamel repair. We found that the formulation containing 20% NACP and 5% DMAHDM greatly reduced and modulated the cariogenic biofilm with effects on the virulence factors of key microorganisms. The combinatory formulation also presented a robust release of calcium and phosphate ions that imparted changes in the mineral loss of enamel. The formulation of a dental sealant with antibacterial and remineralizing potentials is a promising approach to prevent dental caries on the occlusal surfaces of children’s and adolescents’ teeth.
    • MDental 2021

      University of Maryland, Baltimore. School of Dentistry, 2021
    • Development of New Formulations of nCaF2 Dental Nanocomposites with Antibacterial and Remineralizing Properties

      Mitwalli, Heba; Weir, Michael D.; 0000-0003-3877-6632 (2021)
      It is desirable to use a minimally invasive approach in dentistry through conservative techniques in order to prevent destruction of the tooth structure. Since resin-based dental materials are increasingly used, the occurrence of re-infections is also increasing. Recurrent caries and secondary infections are major problems in the restorative dentistry field. The prevalence of recurrent caries associated with resin-based restorative materials was previously shown to reach 60%. It is the most common reason recognized for composite resin restorations replacement and failure. Many efforts have been made to incorporate antibacterial agents into restorative materials. However, the majority of these materials act by releasing these agents into the surrounding environment, leading to their depletion over time. There is a clinical need for durable bioactive composite restorations that resist the formation of secondary caries for an extended period of time. Dimethylaminohexadecyl methacrylate (DMAHDM) is an antibacterial agent that is immobilized in resin and not lost or released with time. Therefore, this dissertation aims to develop new composite resin formulations containing DMAHDM antibacterial, 2-methacryloyloxyethyl phosphorylcholine (MPC) protein repellent, and nanoparticles of calcium fluoride (nCaF2) remineralizing modalities which could be a promising approach for management of recurrent caries around or under restoration margins. This dissertation incorporated DMAHDM, MPC and nCaF2 into composite resin restorations to achieve potent, long-lasting antibacterial, protein repellent, and Ca and F ion release and recharge/re-release capabilities. Mechanical testing was performed for all composite formulations. To determine biofilm properties, a human salivary microcosm biofilm model was used. Biofilm colony-forming units (CFU), minimum inhibitory concentration, lactic acid production, and metabolic activity of biofilm were investigated. Fluoride (F) and calcium (Ca) initial ion releasing, recharging and re-releasing capabilities were tested. The majority of nCaF2 nanocomposites show matching mechanical properties to the commercial control composite. The nCaF2-DMAHDM nanocomposites have potent antibacterial effects that substantially reduce biofilm activities in all biofilm experiments. Similarly, all nCaF2 nanocomposites have higher values of F and Ca ion release- recharge, and re-release when compared to the commercial control composite. Therefore, these new composite resin formulations may potentially lead to a fundamental contribution in restorative techniques that can be used to fight this most common limitation of composite restorations - recurrent caries - and contribute to the longevity of composite restorations through long-lasting antibacterial and protein repellent properties and remineralization capabilities.
    • Incidental Findings in Cone Beam Computed Tomography Images During Prosthodontic Evaluation: Characteristics of Head and Neck Atheromas

      Amarin, Rula Sabah Odeh; Masri, Radi, 1975- (2021)
      Objectives Atheromas can be incidentally detected in routine CBCT images. This study aims to assess prevalence, and risk factors associated with these vascular lesions. Materials and Methods Full-volume CBCT images of 458 patients were evaluated and divided into 4 groups: Subjects with no atheroma, subjects with intracranial atheroma (ICA), subjects with extracranial atheroma (ECA), and subjects exhibiting combined lesions. Age, sex, medical conditions, family history, and size were documented. Results Of the 458 subject scans, 29.9% presented with incidental atheromas. Atheroma’s incidence was significantly higher in older patients and in males compared to females. Patients with atheroma were significantly more likely to have a history of hyperlipidemia, hypertension, and myocardial infarction. Patients exhibiting combined lesions were more likely to have cardiovascular risk factors. Conclusion Incidentally detected atheromas are common and subjects with combined lesions are at higher risk for CVD, and this warrants early referral to medical specialists.
    • Determining the Neural Correlates of Burning Mouth Syndrome

      Payano Sosa, Janell; Seminowicz, David A.; 0000-0003-1337-3749 (2020)
      In the United States, nearly 1 million people suffer from burning mouth syndrome (BMS), a chronic orofacial pain condition that is largely unrecognized by the medical community and predominantly affects post- and peri-menopausal women. Relatively little in-depth research is available on the condition, and patients often give up seeking treatment. The pain in BMS arises spontaneously (i.e. in the absence of stimuli), but the mechanisms of this spontaneous pain is unclear, and there is limited research on structural and functional brain changes that may occur in a BMS sufferer. The goal of this dissertation was to investigate the central nervous system mechanisms of pain experienced in BMS. We collected: 8-day diaries, morning and afternoon quantitative sensory testing of both orofacial and forearm regions; afternoon structural and functional MRIs, and questionnaires from 27 BMS patients and 33 healthy post-menopausal women. Our hypotheses that, compared to healthy participants BMS patients have: higher pain sensitivity, especially in orofacial regions during the afternoon; lower grey matter volume and higher functional connectivity in nociceptive pathways associated with noxious heat during rest and evoked thermal pain, even after accounting for anxiety, were not supported. Instead, we found a time-of-day-dependent effect during warm detection and cold detection of face and forearm; lower grey matter volume of the dorsolateral prefrontal cortex (DLPFC), and higher grey matter volume of the inferior temporal gyrus and parabrachial nucleus (PBN); lower PBN connectivity with the DLPFC and primary somatosensory cortex (S1); higher connectivity of the right lateral hypothalamus (LH) with posterior insula during warm condition; connectivity of right medial hypothalamus and LH to left DLPFC and right PBN to bilateral S1 not associated with anxiety in BMS compared to healthy participants. Altogether, BMS showed abnormal responses to innocuous stimuli. This was supported by fMRI data, where connectivity differences were mostly present during innocuous stimulation. These altered sensory and brain responses could reflect heightened anticipation of thermal stimuli (both pain-specific and non-pain specific) associated with disruption of communication between regions associated with negative affect of pain (insula), attention modulation of pain (left DLPFC), somatosensation (S1), and thermoregulation (LH and PBN).
    • Surface Roughness of Zirconia Produced by Additive and Subtractive Manufacturing

      Triana, Frank James; Masri, Radi, 1975- (2021)
      Purpose – The purpose of this in vitro study was to compare surface roughness of full contour zirconia restorations produced by additive and subtractive manufacturing Materials and Methods – Full contour restorations were designed using 3Shape Dental System. The stl files were exported and utilized to guide production of all specimens. Zirconia samples were manufactured by two methods – additive manufacturing (n=10) and subtractive manufacturing (n=18). A two-step polishing protocol was used following sintering. All specimens were subject to profilometry to measure average Ra values. Ra values for both groups were compared. Statistical analysis was performed using t-test (p=0.05). Results – The average Ra value for zirconia restorations in the subtractive manufacturing group was 0.35 ±0.07µm while average Ra for additive manufacturing groups was 1.06 ±0.49 µm. Differences were statistically significant (p < 0.00001). Conclusions – Zirconia restorations produced by subtractive manufacturing were significantly smoother than those produced by additive manufacturing even after post-sintering polishing.
    • Metagenome and Metatranscriptome Analysis of the Subgingival Bacteria in Periodontal Disease. A Systematic Narrative Review

      Wohl, Hirschel; Aichelmann-Reidy, Mary Beth (2021)
      The main purpose of this systematic narrative review is to determine the difference in abundance of bacteria and bacterial genes of subgingival microflora of human periodontal pockets compared to healthy sites, via Metagenomic and Metatranscriptomic analyses. Databases EMBASE and MEDLINE were searched for articles, with earliest records from 1978. Main outcome measures included: 1) Bacterial genera and/or species significantly increased 2) Most prevalent or significantly upregulation of genes. Ten studies met selection criteria and were included in the study. Nine studies were cross-sectional, and one was longitudinal. Main results showed trends of specific bacteria and genes found in periodontal pockets. However, within the limitations of this narrative review, trends of abundant bacteria and genes does not imply these specific species or genes are actively participating in disease progression. Nine of ten included studies were cross-sectional in design with eight studies being metagenome based and not able to measure gene expression.
    • The Color Stability of 3D-Printed and Milled Zirconia Crowns

      Spatz, Harrison; Masri, Radi, 1975-; 0000-0002-3583-7674 (2021)
      Purpose: This is an in vitro study on the color stability of 3D-printed and milled zirconia crowns. Materials and Methods: A total of 18 samples were tested, 9 milled and 9 printed zirconia crowns. Change in color (ΔE) was assessed before and after samples were soaked in solutions of coffee, chlorhexidine and distilled water for a simulated period of 1 week. Two-way ANOVA was used to compare between the groups. Results: There was a significant difference (P = .003) between ΔE of samples soaked in chlorohexidine (4.24 ±3.62) versus coffee (8.84 ±7.48) and between ΔE of samples milled (1.64 ±1.12) versus printed (11.11 ±3.96, P ≤ .0001). Conclusion: Printed zirconia crowns are more susceptible to staining than milled crowns. Printed zirconia crowns appeared noticeably darker when soaked in coffee and lighter when soaked in distilled water and chlorohexidine.