Founded in 1804, the University of Maryland School of Dentistry is the direct descendant of the world's first dental college, the Baltimore College of Dental Surgery (BCDS). The School's mission is to graduate exceptional oral health care professionals, contribute to the scientific basis of treatments for diseases of the orofacial complex, and deliver comprehensive dental care.

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  • 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
  • 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.

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