Dental Theses
This series contains theses from the University of Pennsylvania School of Dental Medicine. For more information about University of Pennsylvania dissertation/theses requirements and guidelines, please consult the dissertation manual.
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Publication ACCURACY OF 3D PRINTED MODELS WITH DIFFERENT DIE SPACING VALUES: AN IN VITRO COMPARISON TO A SOLID MASTER MODEL.(2024-08-30) Papaioannou, MarianthiStatement of the Problem: The accuracy of 3D-printed master models is crucial in prosthodontics, as any inaccuracies can result in poorly fitting restorations, particularly regarding margins, contact points, and occlusal levels. While various factors related to the printing process can influence the accuracy of these models, there is limited evidence on how die spacing in removable dies specifically impacts their precision. Purpose: The goal of this present study is to evaluate the accuracy of 3D-printed Pindex models by assessing the effects of varying die spacing values in comparison to a control solid 3D-printed master model. The null hypothesis is that there is no difference between the solid models with the test groups. Materials & Methods: A control model representing eight prepared teeth was designed using a design software (Modelliere, Zirkonzahn, Italy), exported as an STL file, and printed via additive manufacturing (Pro S , Sprintray,). The test samples, divided into three groups with offset values of 0.1mm(Group A), 0.05mm(group B), and 0.03mm(Group C), were fabricated from the same STL file. Each group consisted of ten samples. Post-processing followed the manufacturer’s guidelines, including alcohol rinsing, air drying, and UVA light curing. Samples were scanned using a laboratory scanner (Dentsply, Sirona) after being coated with a thin layer of titanium oxide powder to eliminate reflections and ensure high-quality data acquisition. The scanned files were then analyzed using Geomagic software, with all data aligned to the control model for comparison. Results: The findings confirmed the null hypothesis, showing no statistically significant differences between the three groups. However, the study revealed a notable difference in the fit of the dies in Group C, with a die spacing of 0.03mm, which exhibited greater deviation from the control model compared to Groups A and B, which showed closer alignment with the solid model. Conclusions: The results provide insights into the impact of die spacing variations on the accuracy of 3D-printed master models, contributing to improvements in digital dental model fabrication. The results provide valuable insights into how variations in die spacing affect the accuracy of 3D-printed master models, contributing to advancements in digital dental model fabrication.Publication Long-term Clinical and Radiographic Healing of Endodontic Microsurgery with Collagen-Based Bone-Filling Material: Comparison of 2D and 3D Healing(2024-08-30) Szu Hua Chiang, DMDABSTRACT Aim: (1) To evaluate the long-term clinical and radiographic periapical and cor:cal bone healing of endodon:c lesions with four-wall defects following endodon:c microsurgery (EMS) using collagen-based bone-filling material, (2) to study collagen-based filling material’s clinical significance and (3) to compare 2D- and 3D- outcome assessments. Methodology: The long-term clinical and radiographic evalua:ons of 58 surgical cases was reported in ‘Periapical Healing Following Endodon:c Microsurgery with Collagen-Based Bone- Filling Material: A Randomized Controlled Clinical Trial by Albagle et al. IEJ 2023 (1). In the preliminary methodology of this study, EMS was performed by calibrated postgraduate endodon:c residents. Before flap closure placement of a collagen-based bone-filling material was randomly assigned to osteotomies as the treatment group, whereas no material was placed in the control group. If necessary, separate osteotomies were created for mul:-rooted teeth. Samples were included only if two osteotomy sites were separated by bone. Each individual osteotomy was considered a sample and randomized. Proceeding with the asymptoma:c 66 endodon:c-origin lesions collected and assessed at the 1-year follow-up evaluated by double blinded endodon:sts examined using periapical (PA) radiographs according to Molven’s criteria 20 for 2D healing, cone beam computed tomography (CBCT) scans in conformity with Penn 3D criteria for 3D periapical healing and RAC/B index for cor:cal plate healing. For follow-up, pa:ents (n = 58) were contacted ini:ally for phone interviews, to determine if symptoms or it needed an extrac:on or re-surgery. Subjects returned for the long-term follow-up appointment. Teeth were assessed for sensi:vity to palpa:on and percussion, mobility, probing depths and symptom as such as presence of intraoral swelling or sinus tract. PA radiographs and CBCT scans of the asymptoma:c teeth were evaluated similarly by three evaluators following Molven and Penn3D evalua:on methods. Results: A total of 39 cases were evaluated radiographically a9er excluding extrac:ons, lost pa:ents, declining to clinical examina:on and one symptoma:c case due to fracture. The follow- up period ranged from 2.78 years to 4.75 years; 17 and 22 cases are in the control and treatment groups, respec:vely. Both control and treatment groups obtained higher success rates according to Molven’s criteria (95.5% and above) than PENN 3D criteria and C-score system. At the 3 year follow-up, the success rates were determined similar between PENN 3D and C-score ranging from 82.4% to 86.4% in both treatment and control groups. Compared to the control group, the Founda:on group obtained higher percentage of healing at year 1 according to Molven’s criteria, PENN 3D, and C-score system. In contrast, the control group had an overall higher improvement in healing rate from year 1 to year 3. The long-term follow-up rate for the study was 75.9%. Conclusions: The long-term evalua:on of the cor:cal plate healing is equal in the control and treatment groups as the observa:on period reached close to 4 years or above. The cri:cal healing 21 period was between 1 year to 3 years, where placement of collagen-based bone-filling material is suggested to accelerate the radiographic healing in two- and three- dimensions.Publication Cellular Senescence in Periodontitis: From Pathogenesis to Therapeutics(2023-12) Kantapon RattanaprukskulOver 70% of the elderly population exhibits some forms of periodontal diseases, imposing a significant global health burden. Cellular senescence is a hallmark of aging, which can be triggered by various extrinsic and intrinsic stressors. Senescent cells maintain metabolic activity and display a senescence-associated secretory phenotype (SASP). The accumulation of senescent cells within tissues can have detrimental effects, fostering further senescence in neighboring cells, and ultimately leading to numerous chronic conditions. Senotherapeutics, such as dasatinib and quercetin (DQ), are being used as safe and effective strategies to alleviate senescent cell burden and SASP in multiple chronic inflammatory conditions. Our hypothesis posits that cellular senescence serves as a driver of periodontitis, and targeting senescent cells could enhance disease outcomes. This study entails investigating senescence signatures such as p16, lipofuscin and β- galactosidase and SASP in gingival tissues from both periodontitis and healthy subjects, as well as examining the effects of pharmacological and genetic senescent cell targeting in preclinical disease models. We demonstrated significantly increased levels of senescence markers within periodontitis lesions compared to periodontally healthy sites, with specific patterns based on tissue localizations. P16 levels were predominantly upregulated in the epithelial layers, whereas lipofuscin and β-galactosidase were abundant in the connective tissue region, colocalizing with fibroblasts and macrophages. In vivo observations aligned with the clinical data, showcasing increased senescence in the course of periodontitis. Intriguingly, DQ treatment reduced senescent cell burden and mitigated alveolar bone loss in both young and aged mice. Additionally, we demonstrated the therapeutic effects of DQ on gingival keratinocytes in response to chronic exposure to F. nucleatum. Specifically, DQ exerts its mitigating effect on senescence through multiple cellular pathways, such as cell cycle arrest, metabolic dysfunction, and cellular morphology. Furthermore, we employed a mouse model for genetically targeting senescent cells, yielding improved periodontitis phenotypes. In summary, our study underscores the role of cellular senescence in periodontitis, suggesting that targeting senescence holds promise as an innovative approach to enhance periodontal health among susceptible individuals.Publication Lysosomal pH and the Control of Genes Involved in Inflammation and Degradation(2013-06-01) Khan, Sara A.The endosomal/lysosomal system is essential for cell survival. The regulation of lysosomal pH is critical for lysosomal function and has been known to play a pivotal role in aging and disease. The pH within the lysosomes is essentially increased in certain diseases and our preliminary data suggests that it may also increase with age. It is known that the methods used for lysosomal pH measurement are extremely difficult and technique sensitive. In this study, we searched for key genetic markers to help identify the presence of chronic elevation of lysosomal pH. This will allow us to utilize the speed, specificity and sensitivity of laboratory confirmation with quantitative polymerase chain reaction (qPCR) as an alternative method to direct measurement of lysosomal pH. In our study, we demonstrated a trend towards an increased expression of TcfEB and vATPase genes in the presence of long-term lysosomal pH elevation. Therefore, these two genes could potentially be used as markers to recognize the presence of chronic lysosomal pH elevation in diseased cells. In contrast, a short-term lysosomal pH elevation showed a decreased expression of IL-1b, IL-18 and TcfEB highlighting the time-dependent nature of genetic expression. Both genes, TcfEB and vATPase, might be used as important tools for the rapid detection of disease or infection in clinical specimens and are also particularly suitable in optimizing the therapeutic management of diseased cells.Publication Purinergic Signaling in Painful Pulpitis(2023-04-17) See, LilyInjury of the tooth pulp is often excruciatingly painful and yet the receptors and neural circuit mechanisms that transmit this form of pain remain poorly defined in both clinical human and preclinical rodent models. The role of purinergic pathways are of particular interest and potential relevance in dental inflammation and pain. This study examined the involvement of purinergic receptors in human dental inflammatory pain by comparing their distribution in healthy pulps compared to symptomatic and asymptomatic inflamed pulps, and then testing for sex differences in expression. Ionotropic P2X2R and P2X3R were selected for their implication in pain; whereas ecto-nucleotidase NTPDase1 (CD39) reflects extracellular ATP concentration. We found P2X3R and P2X2R, as well as CD39, to colocalize with protein gene product 9.5 (PGP9.5)-positive nerves in control tissues. P2X3R was additionally found on odontoblasts, and CD39 on other non-neuronal structures. Both immunohistochemistry and immunoblots demonstrated that all three proteins were significantly increased in symptomatic pulpitis, suggesting both receptors and agonist ATP were elevated with increased pain. Increased expression of P2X3 and CD39 were more frequently observed in women than men. Our findings support a role for increased purinergic signaling in humans with inflammatory dental pain, with preference in women. This differential response suggests purinergic signaling may contribute to sex differences in pain. To further study signaling pathways of painful pulpitis in the preclinical model, quantifiable behavioral models, namely the Mouse Grimace Scale (MGS) and Facial von Frey assay, were evaluated for their validity in assessing dental pulp pain in mice. We found that unilateral pulp exposure injury to the first maxillary molar in mice resulted in significant increase in MGS from 24 h onward, indicating presence of spontaneous pain. Mechanical allodynia, assessed by the Facial von Frey assay, progressed more gradually with significant increases on both sides of the face on day 4, and unwillingness to tolerate filaments above 0.6 g by day 6 post-injury. This work demonstrates that we have clear, easily identifiable behavioral readouts for trigeminal nociception in the mouse following dental injury.Publication A Retrospective Pilot Study of the Clinical and Histopathological Features of Oral Lichen Planus: Comparison of the Diagnostic Criteria(2022-11-24) Alaraik, Ayman F; Sollecito, Thomas P; Stoopler, Eric T; Akintoye, Sunday O; Bindakhil, Mohammed AObjective: The purpose of this study was to compare published Oral Lichen Planus (OLP) diagnostic criteria. Study Design: After obtaining IRB approval, electronic health records at a tertiary care academic medical center from 2015 to 2021 were reviewed. Adult patients with OLP (ICD-10 code L43 and its subcategories) were included. Cases were excluded if histological analysis or outcomes were not reported. Results: 341 charts were reviewed. Patient mean age was 66.2±11.7 years and 74.4% were female. 79.7% had OLP lesions in multiple anatomical locations within the oral cavity. 90.3% had bilateral involvement. Skin and genital lesions were reported as 15.5% and 13.7% respectively. 86.5% of cases had plaque, reticular or Wickham striae (WS), whereas 17.8% had atrophy, erosion, or ulceration. When applying the available diagnostic criteria to this cohort, 100% of cases agreed with 1978 WHO criteria, 60.9% with 2003 modified WHO, 74.5% with 2016 AAOMP, and 70.4% with 2020 WHO. Clinicopathologic features agreed with all 4 published criteria in 60.9% of cases. Conclusions: The 1978 WHO criteria may lack specificity, while 2003 WHO could be too specific clinically and histologically. The 2016 AAOMP criteria may be too strict histologically, while the 2020 WHO criteria may be too strict clinically. Further prospective studies are needed to reconcile diagnostic criteria.Publication Dolutegravir in Neurons and Macrophages: Molecular Mechanisms of Neurotoxicity and Neuroprotection(2022-12-22) Alboloushi, NaelaDespite effective antiretroviral (ARV) therapy (ART), human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) persevere, affecting up to 30%-50% of all HIV-infected individuals. Although the end result involves neuronal damage and death in the absence of ART, neurons themselves are not directly infected by HIV; therefore, the pathological mechanisms are most likely indirect. Biomarkers of inflammation, immune activation, and oxidative stress remain elevated in the cerebrospinal fluid (CSF) of HIV-infected individuals throughout the course of infection regardless of the ART status. HAND is multifactorial, and both the presence of infected and activated macrophages, which are considered as a major source of HIV replication in the central nervous system (CNS), and ARV-mediated toxicity have been implicated in the persistence of HAND. Dolutegravir (DTG)-containing regimens are first-line treatment options recommended by many health guidelines. However, several studies have raised concerns regarding DTG-associated CNS abnormalities. Taken together, we hypothesize that DTG contributes to neuronal death directly via oxidative stress induction, while indirectly providing neuroprotection from HIV-induced neurotoxicity by inhibiting viral replication in macrophages. In this dissertation, we have identified two related yet independent mechanisms of DTG-mediated neurotoxicity, each of which may contribute to HAND pathogenesis. First, we show that DTG mediates neurotoxicity in vitro via increased reactive oxygen species (ROS) production and oxidative stress induction, as indicated by the alleviation of DTG-mediated neurotoxicity with the inducers of endogenous antioxidant response. Second, we generated supernatants from monocyte derived macrophages (MDM) exposed to DTG, with and without HIV infection or HIV/MDM and Mock/MDM, respectively. And we demonstrated that DTG-treated HIV/MDM has lower glutamate released compared to HIV-only/MDM. Moreover, DTG-treated HIV/MDM supernatants were not neurotoxic, compared to HIV/MDM supernatants. On the other hand, in the absence of HIV, DTG-treated Mock/MDM have increased expression of nuclear factor (erythroid-derived 2)-like 2 (NRF2), a transcription factor that regulate the expression of antioxidant and cytoprotective genes. To our knowledge, this is the first study looking at both neurons and macrophages simultaneously. Taken together, DTG may contribute to the pathology seen in HAND patients both directly and indirectly. From a translational point of view, these findings not only impact ARVs prescription based on possible adverse effects, but also highlights the importance of both targeted- drug therapy and adjunctive therapies.Publication Mechanical Stimuli-Defined TNFα Endocytosis Governs Mesenchymal Stem Cell Homeostasis(2022-12-16) Yu, WenjingTumor necrosis factor alpha (TNFα) is a pro-inflammatory cytokine responsible for immune regulation and is considered to execute its function mainly through its receptor- mediated canonical signal pathway. Mesenchymal stem cells (MSCs) are the heterogeneous primitive cells initially discovered residing in the adult bone marrow stroma, possessing self-renewal and multiple differentiation potential and critically maintaining multiple tissue/organ homeostasis. The interplay between MSCs and immune cytokines via the receptors on the MSC surface has increasingly been recognized; increasing evidence has shown that MSCs produce a certain amount of cytokines by themselves with little understanding of the role of MSC-derived cytokines. In this study, we, for the first time, reveal a non-inflammatory, non-canonical role of MSC-derived TNFα by showing that TNFα-deficient MSCs exhibit impaired self-renewal and differentiation due to upregulated mTOR phosphorylation. Mature TNFα is internalized into the cytoplasm via endocytosis after being cleaved by the TNFα- converting enzyme and shedded into the extracellular microenvironment. We further find that cytoplasmic TNFα binds to Rictor, a component of mTOR complex 2, to restrain mTOR activation. A complex regulatory network and signaling pathways are involved in governing MSC fate commitment. Mechanical stimuli, including physical cues from the matrix and applied forces, account for one critical extrinsic factor controlling MSC fate determinations. Microgravity conditions, such as astronauts in spaceflight missions and bedridden patients, are reported to result in progressive bone loss, but the therapeutics have yet to be established. In our study, we use hindlimb unloading (HU) mice to mimic the microgravity condition and find that HU mice resulted in reduced TNFα endocytosis and impaired cell function in MSCs as well as osteopenia phenotype. Rapamycin therapy rescues MSCs impairment and osteopenia in HU mice by blocking mTOR activation. Collectively, our findings identify a previously unrecognized role of TNFα in maintaining MSC homeostasis via receptor-independent endocytosis to finetune mTOR signaling homeostasis. A mechanical stimuli-dependent and receptor-independent endocytosis of TNFα is required to maintain mTOR equilibrium and therefore safeguard MSC homeostasis. Rapamycin may be a promising therapy for hypodynamia-induced osteoporosis in astronauts and bedridden patients.Publication Accuracy of Intra-oral Scanner Impression for Different Post-Space Lengths(2022-12-19) Almalki, Abdulrahman; Blatz, Markus; Anadioti, Evanthia; Conejo, Julian; Hai, QingPurpose: To compare the accuracy of the intra-oral scanner for different post space lengths 6, 8, and 10 mm and compare it with conventional impressions using three-dimensional software. Materials and methods: A total of forty-five root typodont teeth (Maxillary central incisors) were selected. Root canal treatment and tooth preparation for the crown were performed on all teeth. Post space preparation of 6, 8, and 10 mm were created using prefabricated fiber post drill to standardize post space width and length. Root canal impressions were performed on all teeth using polyvinyl siloxane impression material. Each impression was then three-dimensionally scanned using an extraoral lab scanner to be used as a control. A direct scan was obtained using the chair-side scanner for each group. The file was exported to perform digital volume measurement using Geomagic control software to determine accuracy. Results:Mean overall post-length accuracy was 75, 95, and 144 mm for groups 6, 8, and 10 mm post-depth, respectively. The accuracy of the digital intra-oral scanner compared to PVS impression groups was statistically not significant in the coronal, middle, and apical third (P= >0.05) except in the apical third for the 10 mm post depth (P= Conclusion: Direct chairside scanning for post space has the same comparable accuracy as those using the gold standard direct conventional impression technique.Publication Preliminary Analysis of Transcriptomic Variations in Esrp1/Sox2 Double Transgenic Mouse Embryo Facial Prominences in Search of Esrp1 Targets Responsible for Cleft Lip and/or Palate Pathogenesis(2022-06-06) Lee, GraceCleft lip and/or palate (CL/P) is a highly prevalent craniofacial deformation worldwide, that is challenging to treat. Despite the series of reconstructive surgeries, orthodontic treatments, and functional rehabilitation therapies, patients can not fully recover from the esthetic and functional defect they were born with. A paradigm-shift in treatment approach is needed to lift the medical, psychosocial, and financial burdens from the patients and their families, one that would intercept the malformation in utero and recapitulate normal development of the lip and the palate before birth. A necessary first step towards this goal is to decipher the intricate molecular mechanisms underlying CL/P pathogenesis. We used a novel double transgenic mouse model Esrp1-/-;Sox2+/- and RNA-sequencing technology to search for target genes responsible for CL/P. The ablation of Esrp1 results in orofacial clefting in mouse embryos, but Sox2 haploinsufficiency in Esrp1-/- mouse rescues the CL/P phenotype by restoring normal development of the face. The analysis of the transcriptomic variations between Wild Type, Esrp1-/- and Esrp1-/-;Sox2+/- mice revealed that numerous genes were differentially expressed in the ectoderm and mesenchyme of the facial prominences at a critical stage for fusion. Among the genes that were either normalized or compensated by Sox2 haploinsufficiency in the Rescue model, we identified genes from known signaling pathways like Bmp4 and key epithelial-mesenchymal transition genes such as Snai1, Twist1, and Zeb1. This preliminary study lays the groundwork for promising treatment opportunities for orofacial clefting.