Now showing items 1-20 of 609

    • 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.
    • Tongue Asymmetry and Muscle Shortening During Speech in Partial Glossectomy Patients and Controls

      Miller, Natalie; Stone, Maureen L. (2021)
      Tumors of the tongue are routinely removed by partial glossectomy surgery. This study examines the extent of anatomical asymmetries caused by the glossectomy surgery and its effects on the tongue’s resting position and motor symmetry. Magnetic resonance imaging (MRI) data of ten control subjects and ten glossectomy patients were obtained. 3D tongue volumes were extracted from high-resolution MRI data using Matlab. Using cine- and tagged-MRI data, shortening of the genioglossus, transverse, and verticalis muscles were calculated during a speech task involving /∫/ and /l/. Anatomical asymmetries were observed in the control subjects, although they were generally small and less than in glossectomy patients. Glossectomy patients aimed to distribute their tongue volume evenly in the oral cavity, irrespective of anatomical asymmetry, by posturing their tongue towards the resected side. Glossectomy patients shortened more muscles when executing the speech task. Muscle shortening asymmetry was observed in both control and patient groups.
    • Optimal Antero-Posterior Position of the Maxillary Central Incisors and its Relationship to the Forehead in Adult Asian Males

      Kocan, Jessica; Sanchez, Dina (2021)
      Objective: To determine an optimal antero-posterior (AP) position of the maxillary central incisors (CI) and its relationship to the forehead in Asian males. Methods: Smiling profile photographs of 60 Asian males were obtained and divided into three groups based on the judged AP position of CI (“just about right,” “too far forward,” “too far back”), as evaluated by orthodontists and laypersons. CI position and forehead inclination (FI) were measured relative to glabella vertical (GV). Statistical analysis tested for differences among groups, differences between orthodontists and laypersons, and the relationship between CI position and FI. Results: Optimal CI position was 0.86mm anterior to GV. There were statistical differences between orthodontists and laypersons in the study groups. CI position and FI showed moderate positive correlation. Conclusions: In Asian males, the AP position of the CI can be evaluated relative to the forehead, to plan for optimized CI position and maximized facial harmony.
    • Evaluating Oropharyngeal Airway Volume in Patients with Class II Dental Relationships with Extractions vs Non-Extraction Orthodontic Treatment

      Feizi, Ariana Gabriela; Schneider, Monica, D.D.S., M.S. (2021)
      Purpose: The purpose of this study is to support the position of the AAO by demonstrating that the oropharyngeal volume does not decrease as a result of premolar extractions and orthodontic treatment. Materials and Methods: Cone-beam CT’s were obtained for twenty-seven orthodontic patients before and after treatment. Nine patients were treated with four premolar extractions, and eighteen treated non-extraction. Total oropharyngeal airway volume and minimum area of constriction were measured using InVivo Anatomage Software. Results: The initial and final airway volumes of the non-extraction group were correlated (p = 0.61). The total airway volume in the non-extraction cases showed a significant increase (p = .037). Conclusion: There was no significant change in oropharyngeal volume in Class II patients that underwent orthodontic treatment with extractions, however; patients that were treated non-extraction had a significant increase in oropharyngeal volume. There was no significant change in area of minimum constriction in either group.
    • Tongue Muscle Shortening Differences in Glossectomy Versus Non-Glossectomy Patients

      Dao, Anh; Stone, Maureen L. (2021)
      In cancers that affect the tongue, the most common treatment is glossectomy, a procedure that can have substantial effects on a patient’s intelligibility. We are seeking to identify the effect of this resection on the use of four muscles – genioglossus, transversus, verticalis, and superior longitudinal, which comprise the bulk of the tongue. MRI data was used to study differences in tongue muscle shortening patterns during the speech task “a thing” between patients who have undergone glossectomies and controls who have not. Speech data was collected from 2D tagged-MRI movies and reconstructed into 3D volumes at 26 timeframes. Velocity fields and tissue points were extracted and shortening was calculated to study how the muscles were used by glossectomies vs. controls to protract and retract the tongue during /θ/. The results reveal differences in function between the two groups, and potential compensation strategies for glossectomy patients.
    • The Contribution of TRPV1 S801 Phosphorylation to Nociception and Inflammatory Pain in Vivo

      Joseph, John; Chung, Man-Kyo (2020)
      Transient receptor potential vanilloid subtype 1 (TRPV1) is a nonselective cation permeable channel activated by painful stimuli, such as capsaicin and noxious heat, and enriched in many primary afferent neurons of the pain pathway. During inflammation, chemical mediators activate protein kinases (such as PKC) that phosphorylate TRPV1 and thereby enhance its function, which results in nociceptor sensitization. And this can result in a lower threshold for pain. However, the causal relationships between TRPV1 phosphorylation and pathological pain remain unexplored. To directly investigate the roles of one specific TRPV1 phosphorylation event in vivo, we genetically altered a major PKC phosphorylation site, mouse TRPV1 S801, to alanine. The TRPV1 expression pattern in sensory neurons of S801A knock-in (KI) mice was comparable to that in wildtype (WT) controls. In sensory neurons from KI mice, following the activation of PKC, the usual increase of capsaicin-induced currents was substantially impaired. Thermal hyperalgesia induced by PMA or burn injury in KI was identical to WT. Thermal hyperalgesia was only marginally attenuated in KI mice duirng inflammation. In contrast, PMA-evoked nocifensive responses and hyperalgesia to capsaicin were significantly attenuated in the hindpaws of KI mice. Ongoing pain from inflamed masseter muscle was also reduced in KI mice, and the pain was further inhibited by the TRPV1 antagonist AMG9810. These results suggest that PKC-mediated phosphorylation of TRPV1 S801 contributes to inflammation-mediated sensitization of TRPV1 to ligand, but not heat, in vivo. Further, this suggests that interference with TRPV1 S801 phosphorylation might represent a potential way to reduce inflammatory pain in the clinic, yet spare basal sensitivity and produce fewer side effects than with a more general TRPV1 inhibition.
    • Investigator/Faculty Onboarding: Facilitating the Transfer of Your New PI

      Hoffman, William F., Jr.; Pettitt, Debbie; Simons, Janet, M.B.A. (2020-10)
    • Programmed Death Ligand 1 in Oral Potentially Malignant Epithelium and Implications of Regulation by Interferon Gamma

      Elnaggar, Manar; Younis, Rania H. (2020)
      Programmed death ligand 1 (PD-L1) is an immune-checkpoint regulator. Expression of PD-L1 in a subset of head and neck squamous cell carcinoma (HNSCC) was linked to improved response to immunotherapy. Oral potentially malignant disorders (OPMDs) are characterized by increased risk for malignant transformation. We investigated the expression of PD-L1 in immune cells (ICs) and epithelial cells of OPMD, which is essential to prevent progression to malignancy. Immunohistochemistry analyses in HNSCC whole excision tissue sections (104 patients) indeed demonstrated predominant expression of PD-L1 in the epithelial margins (~86%). This directly correlated with PD-L1 expression in underlying ICs (P=0.0172) with a predominating lichenoid pattern of IC infiltrate. Immunoblotting analyses demonstrated the role of human recombinant IFN-γ in the upregulation of PD-L1 expression in the oral premalignant cell line (DOK) with implications of downstream activation of pS6. Our work suggests a role for IFN-γ/PD-L1 in the immune escape of OPMDs.
    • Dimensional Stability of CAD/CAM Patterns: A Longitudinal Study

      Byun, Shane S.; Masri, Radi, 1975- (2020)
      The goal of this study was to investigate the accuracy, over time, of computer-aided design and computer-aided manufactured (CAD/CAM) dental patterns in two different materials (resin and wax) using two different fabrication methods (subtractive and additive manufacturing). The intaglio surface of the patterns (n=48/time period) were evaluated at five predetermined time periods (zero minutes, 20 minutes, 24 hours, one week, and two weeks) relative to fabrication time. Intaglio surface scans of the generated samples were aligned with the Best Fit alignment to the design file (.stl) and compared with 3D Compare on Geomagic Control X to obtain the deviations as a root mean square (RMS). Trueness of the patterns were compared at all time points using three-way Analysis of Variance (ANOVA) (=.05). Accuracy of dental patterns deteriorated over time. When materials were considered, wax had better dimensional stability than resin. When fabrication method was considered, milled patterns had better dimensional stability than printed patterns. Time, material type, fabrication method, and all their interactions, showed a significant effect, however, the differences were very small (ranging from <1 m to 20 m). Thus, both resin and wax CAD/CAM patterns fabricated by additive and subtractive manufacturing can be used to produce dental restorations with acceptable accuracy.
    • A clinical evaluation of the ability of finishing files to supplement the removal of bacteria and endotoxin from primarily infected root canals (Part I- Initial evaluation)

      Kim, Eunice; Martinho, Frederico C. (2020)
      Aim: The aim of this study was to evaluate the ability of XP-endo Finisher (XPF) to supplement the removal of bacteria and endotoxin from primary infected root canals after instrumentation. Methodology: This randomized and blinded controlled trial included eight subjects. Instrumentation was performed using Vortex Blue or XP-endo Shaper, followed by supplemental instrumentation with XPF. All canals were irrigated with 2.5% sodium hypochlorite. Bacterial and endotoxin samples were taken using sterile paper points. Samples were collected before and after instrumentation and after XPF. Results: Bacteria was present in all root canals. After XPF, bacterial mean was reduced from 255 ± 311.82 CFU/mL to 2.5 ± 7.07 CFU/mL (p= .056). Endotoxin was detected in all root canals by the LAL method (KQCL test). After XPF, endotoxin mean was significantly reduced from .85 ± .26 EU/mL to .03 ± .01 EU/mL (p= .00004). Conclusion: The findings of this study showed that the supplemental use of the XP-endo Finisher after root canal instrumentation was effective in significantly reducing endotoxin but not bacteria present in primary endodontic infections.
    • MDental 2020

      University of Maryland, Baltimore. School of Dentistry, 2020