Research Day

Abstracts

Graduate Students

Research Day 1

Alaa A. Alkhateeb

Alkhateeb AA, Mancl LA, Ramos KJ, Kotsakis GA, Trence DL, Rothen ML, Chi DL.
UW Department of Oral Health Sciences

Study objective: Cystic fibrosis-related diabetes (CFRD) is a unique type of diabetes that affects up to 50% of adults with cystic fibrosis (CF). The prevalence and severity of periodontitis are both significantly higher in adults with diabetes than adults without diabetes. Our previous work indicates that adults with CF are not at greater risk for periodontitis, but it is unknown if CFRD impacts the periodontal health of adults with CF. The goals of this pilot study were to compare the prevalence of periodontitis in adults with CF to non-CF controls, taking into account diabetes status.

Methods: Prospective observational study of adults with CF (age ≥ 18 years) at a single CF Center in Seattle, Washington, USA. CFRD was defined following the American Diabetes Association diagnostic criteria. Periodontitis was defined following the U.S. CDC and the American Academy of Periodontology case definition. We used the 2013-2014 NHANES to form non-CF control groups (with and without diabetes). Non-CF controls were frequency matched to adults with CF on age, sex, diabetes status, and insulin use. Based on CF and diabetes status, we compared periodontitis prevalence across four groups: CFRD, CF and no diabetes, non-CF with diabetes, and non-CF and no diabetes (healthy). We used the Fisher’s exact test for hypotheses testing.

Results: The prevalence of periodontitis for the two CF groups, with and without CFRD, were higher than healthy controls (CFRD 78% vs. healthy 7%; P<0.001), (CF no diabetes 60% vs. healthy 7%; P=0.001) and not significantly different than non-CF controls with diabetes (CFRD 78% vs. non-CF with diabetes 56%; P=0.43), (CF no diabetes 60% vs. non-CF with diabetes 56%; P=1.0).

Conclusion: Regardless of diabetes status, adults with CF had significantly higher prevalence of periodontitis than healthy controls and similar prevalence to non-CF controls with diabetes. Additional studies with a larger sample size and prospective control groups are needed to confirm our study findings.

Supported by: The University of Washington Cystic Fibrosis Foundation Research Development Program (Grant Number: SINGH19R0), the National Institute of Diabetes, Digestive and Kidney Disorders Cystic Fibrosis Research Translation Center Clinical Core (Grant Number: NIH P30 DK089507), the U.S. National Institute of Dental and Craniofacial Research (Grant Number: K08DE020856), the Dr. Douglass L. Morell Dentistry Research Fund, University of Washington School of Dentistry, the UW Dental Hygiene Education Fund, and King Saud University.

Rachel Kehr

Kehr R, Paranjpe A
UW Department of Endodontics

Stem cells of the apical papilla (SCAP) are vital for the success of regenerative endodontic procedures (REPs). Previous studies have demonstrated the effects of inadequate disinfection and bacteria on the success of REPs. Lipopolysaccharide (LPS) is the major component Gram-negative bacteria and could be present in the canal even after bacteria cell lysis and could possibly affect SCAP. However, the direct effect of LPS on SCAP has not yet been elucidated. Hence, the aim of this study is to evaluate the effects of LPS has on the survival and differentiation gene expression of SCAP.

Human SCAP were cultured under three different conditions for 24 hours, untreated cells, LPS and a Dexamethasone group. RNA was extracted and reverse transcribed to cDNA. The cDNA was analyzed using Real time-PCR for various osteogenic, transcription and differentiation genes. Data were analyzed using a one-way analysis of variance (ANOVA).

Real time-PCR analysis demonstrated that SCAP treated with LPS had downregulation of osteogenic genes (ALPL), genes promoting angiogenesis and endothelial cell growth (VEGFC, FT1), and collagen synthesis (COL5A1, COL10A1). There was an upregulation of genes involved with the breakdown of extracellular matrix (MMP13, MMP7), genes involved in the activation of innate immunity (TLR3, TLR4), apoptosis related genes (FADD, TRADD) and those promoting tissue inflammation (IL1B, CSF2).

Conclusions: SCAP treated with LPS have a downregulation of pathways related to osteogenesis, angiogenesis and cell growth, and an upregulation of pathways related to innate immunity activation, apoptosis and tissue inflammation. This research suggests that LPS can have negative effects on REPs.

Apichai Yavirach

Yavirach A, Giachelli CM
UW Department of Oral Health Sciences

Medication-related osteonecrosis of the jaw (MRONJ) is a serious side effect of antiresorptive drugs including bisphosphonates (BPs) and denosumab (anti-receptor activator of nuclear factor kappa B ligand (RANKL) antibody). The pathophysiology of MRONJ remains elusive, however, the potential mechanisms include osteoclast deficiency and macrophage alteration.

Our previous study shows that the replenishment of osteoclasts in the MRONJ mouse model alleviates only some features of the disease. This suggests that the imbalance of pro-inflammatory (M1) and anti-inflammatory (M2) macrophages may potentially play a role in MRONJ as well. Several studies have shown that BPs increase M1/M2 ratio corresponding with severity of MRONJ. On the contrary, effects of denosumab on macrophages in MRONJ remain inconclusive. The objectives of this study are 1.) to determine the effects of RANKL on unpolarized macrophages (M0) in vitro and 2.) to investigate the effects of anti-RANKL antibody on macrophage population in vivo. Bone marrow derived cells were isolated from wild-type mice, differentiated into M0, and treated with RANKL for 2 and 6 hours. RNA was isolated from the treated cells for RNA sequencing for gene expression and pathway analysis. Next, MRONJ model was developed in mice using tooth extraction with anti-RANKL antibody treatment as previously described. Immunofluorescence staining was utilized to study M1 (F4/80+iNOS+) and M2 (F4/80+CD206+) in MRONJ tissue sections.

As a result, several genes were upregulated in RANKL-treated M0 in both timepoints, however, in much lower level compared to M1. Moreover, increased M1/M2 ratio was observed in MRONJ model compared to the control. In summary, although RANKL has a small direct effect on gene expressions of macrophages in vitro, M1/M2 ratio was significantly increased in MRONJ model. This study is the first to show similar effects of BPs and anti-RANKL antibody on macrophage population in MRONJ.

Supported by: United States Department of Defense Peer Reviewed Orthopaedic Research Program Award (OR120074), SunStar Award, Warren G. Magnuson Scholarship, Fulbright Scholarship

Summer Research Fellowship (SURF) Program Students

Research Day 2

Michael Guyumdzhyan

Guyumdzhyan MM, Radella F, Wang Y, Kemoli A, Chung WO, Seminario AL
UW Department of Pediatric Dentistry

Objectives: Secretory Leukocyte Protease Inhibitors (SLPI) are antimicrobial proteins found in saliva. Our goal was to quantify SLPI concentrations in saliva samples of children and adolescents living with HIV (CALHIV) and identify relevant factors associated with its secretion.

Methods: This cross-sectional study was nested within the 1) Optimizing Pediatric HIV-1 study (OPH); early- ART cohort: children enrolled <12 months old; and 2) Pediatric Adherence Study (PAD; late-ART cohort: children enrolled >24 months old. Salivary samples (n=77) from CALHIV at Kenyatta National Hospital were obtained for analysis. Enzyme-Linked Immunosorbent Assays (ELISA) were used to assess SLPI concentrations. Demographics and data on ART and CD4 cell count were obtained from PAD and OPH databases. Two-Sample t-test was used to compare SLPI concentrations between cohorts. Pearson Correlation Coefficient and regression analyses were conducted to identify predictors for SLPI secretion.

Results: Majority of participants were male (55.6%; mean age 13.2±3.4 years). Average time on ART was 11.6±1.7 years. Average SLPI concentrations were 288.6±282.6ng/ml. Analysis of early and late cohorts showed late cohort had higher SLPI concentrations than early cohort (p=0.037). Comparisons of SLPI concentrations with subject age and length of ART showed weak-moderate correlation with SLPI of 0.28 (p=0.01) and 0.23 (p=0.04), respectively. CD4 cell counts showed moderate-positive correlation in both cohorts, though findings were significant only in the early cohort (0.3, p=0.03). Regression analysis indicated that late cohort had 185.14±65.81ng/ml (p=0.0063) more salivary SLPI levels than early cohort.

Conclusion: This study shows the late cohort had significantly higher SLPI concentrations compared to early cohort. Age, length of ART, and CD4 count were found to be associated with salivary SLPI levels. Our results call for longitudinal studies evaluating the impact of early ART initiation on restoring oral innate immune system among CALHIV

Supported by: The University of Washington SunStar and CFAR NIDCR awards; and the University of Washington Dr. Douglass L. Morell Dentistry Research Fund

Sara Johnson

Johnson S, Tang K, Jeffrey S, Arola D, Zhang H
UW Department of Restorative Dentistry, Department of Material Sciences and Engineering

Objectives: Diabetes is a known risk factor for oral diseases, including periodontal disease, but the effect of type 2 diabetes (T2D) on dentin is largely unstudied. Recent research reported decreased mechanical strength of dentin in diabetic compared to non-diabetic patients. The goal of this study was to examine changes in dentin microstructure and composition that may account for decreased dentin strength. Increased plasma glucose in T2D can modify mineral and collagen properties via advanced glycation end-products, which is hypothesized to increase tubule occlusion, mineral-to-collagen ratio and collagen crosslinking.

Methods: Single-rooted extracted teeth from T2D (n=9) and non-diabetic donors (n=9) were collected and polished for analysis. Mineral-to-collagen ratio and collagen crosslinking were obtained along the dentin beams at different locations (apical, middle, cervical root and mid-coronal) using Raman spectroscopy. Occlusion ratio (# of occluded lumens/total lumens) of coronal dentin was analyzed using optical microscopy.

Results: The collagen crosslinking ratio was significantly greater in the whole tooth dentin in T2D compared to non-diabetic teeth (p=0.001). Mineral-to-collagen ratio of dentin in the cervical root (p=0.04) and coronal section (p=0.002) were significantly higher in the T2D teeth samples than control. Occlusion ratio was higher in the coronal dentin of T2D samples (p=0.01).

Conclusion: Dentin from T2D teeth had increased collagen crosslinking in the whole tooth analysis. Mineral-to-collagen ratio was significantly higher in the cervical root and coronal sections of diabetic teeth suggesting possible influences from saliva and blood. Future studies will examine how these biological changes affect dentin fatigue strength and resistance to fracture. Understanding the biological and mechanical changes of dentin in T2D patients will provide a basis for the development of innovative techniques and materials in dental treatments that may prevent the increased tooth fractures in diabetic patients.

Supported by: The University of Washington Dr. Douglass L. Morell Dentistry Research Fund

Madelyn Koh

Koh M, Kerr D, Hill CM, Chi DL
UW Department of Oral Health Sciences

Objectives: To understand topical fluoride-related beliefs and refusal behaviors for caregivers of children with special health care needs (CSHCN).

Methods: This was a two-part explanatory sequential mixed methods study. For the quantitative analyses, we surveyed 523 caregivers to (a) compare fluoride-related beliefs for caregivers of CSHCN and caregivers of healthy children and (b) evaluate the association between SHCN status and topical fluoride refusal. We used logistic regression models to generate unadjusted odds ratios (OR), confounder-adjusted odds ratios (AOR), and 95% confidence intervals (CI). For the qualitative analyses, we analyzed interview data for 56 caregivers who refused or were hesitant about topical fluoride. Data were coded deductively and compared by special health care need (SHCN) status to assess the relative importance of each domain based on an existing topical fluoride refusal model.

Results: In the quantitative analysis, 41.3% of surveyed caregivers refused or thought about refusing topical fluoride. There were no significant differences in beliefs about topical fluoride (p-values > 0.05) and there was no significant association between SHCN status and topical fluoride refusal (AOR: 0.65, 95% CI: 0.37-1.14; p=0.13). In the qualitative analysis, caregivers of CSHCN were represented across all six domains and the relative importance of each domain was similar to caregivers of healthy children. Two differences were that all caregivers of CSHCN wanted to keep chemicals out of their child’s body and thought fluoride was unnecessary.

Conclusion: While caregivers of CSHCN were not more likely to refuse topical fluoride than caregivers of healthy children, there are differences in reasons for refusing topical fluoride. Strategies to manage topical fluoride hesitancy and refusal in clinical practice may need to be tailored to caregivers of CSHCN.

Supported by: University of Washington Dr. Douglass L. Morell Dentistry Research Fund, the Lloyd and Kay Chapman Endowed Chair for Oral Health, and grant funding from the U.S. National Institute of Dental and Craniofacial Research [grant number: R01DE026741].

Roxanne Koistinen

Koistinen R, Jain S
UW Department Periodontics

Lipid A (LA) is a lipopolysaccharide (LPS) moiety expressed on the outer membrane of gram-negative-bacteria. The immune-system-receptor-complex, TLR-4/MD-2 binds to LA, eliciting a pro-inflammatory-response. Porphyromonas gingivalis (Pg), a subgingival bacteria associated with periodontitis exhibits heterogeneous LA. LA heterogeneity results from a deacylation enzyme encoded by gene PGN_1123 and dephosphorylation enzymes encoded by genes PG1587 and PG1773. Several Pg LA molecules are antagonistic/inert for TLR4 activation, resulting in immune evasion and survival.

Planktonic Pg was grown in tubes of TYHK broth and biofilm Pg was grown in 24-well-plates with TYHK. The samples were spun, pellets were brought up in TRIzol/chloroform, centrifuged, the upper aqueous phase (UAP) pipetted into a new tube, and an equal volume of isopropanol was added to the UAP. Samples were Zymo RNA treated according to the instructions. RNA was converted to cDNA. The cDNA was subjected to qPCR.

In this work, expression of PGN_1123, PG1587 and PG1773 genes (gene(s) of interest or GOI) were compared between planktonic and biofilm growth by qPCR, in duplicate, and by multiple experiments. Expression during planktonic and biofilm growth, as measured by qPCR cycle-threshold (Ct) values, were comparison to Pg16s rRNA reference genes Ct. ∆Ct was determined by calculating the difference between the mean Ct of the GOI and the mean Ct of Pg16s. This data does not refute or support the following hypothesis: deacylation and dephosphorylation of LA are regulated by the local environment and there will be differential expression between planktonic and biofilm growth, indicating the genes are subject to specific regulation, since gene expression did not uniformly increase/decrease across multiple experiments. GOI expression was compared to their three-gene-operons by qPCR and showed the first gene was more highly expressed than the second gene, which was more highly expressed than the third gene, suggesting they are co-transcribed in an operon.

Supported by: The University of Washington Dr. Douglass L. Morell Dentistry Research Fund

Deborah Lee

Lee D, Hanson-Drury S, Alghadeer A, Ruohola-Baker H
UW Department Biochemistry

Objectives: Tooth regenerative therapy requires an understanding of tooth morphogenesis. With our novel single-cell combinatorial indexing RNA sequencing (sci-RNA seq) of human fetal developing oral tissues, we now have the computational power to analyze multiple signaling pathways in tooth development and reveal critical signaling patterns that determine tooth germ identity. Here we focus on the signaling molecules produced from the dental mesenchyme and received by the dental epithelium to identify the most active signaling pathways in molar and incisor development, compare signaling patterns between tooth types, and identify transcriptional targets unique to each tooth type.

Methods: sci-RNA seq data of molar and incisor toothgerms (n=42,174) were analyzed using Monocle 3. The dental epithelium and mesenchyme lineage were divided into subpopulations. Top pathway analysis was used to identify differentially expressed genes, activated ligand-receptor pairs, and downstream transcriptional targets within molar and incisor progenitors.

Results: Both incisor and molar toothgerm datasets showed the same five transcriptionally unique dental mesenchymal cell types, including two distinct progenitor populations, SOBP and DEM. Molars and incisors shared major signaling pathways such as BMP, FGF, WNT, and ACTIVIN, but at different levels of activity. Unique transcriptional targets of each toothgerm type included SLC2A1, SLIT2, RAC1, and IGF2R for the incisor and SOX4, MAPK14, and IGFBP5 for the molar. We hypothesize that these transcriptional targets account for the different activity levels between molar and incisor toothgerms.

Conclusion: Despite sharing several signaling pathways, molar and incisor progenitors develop into dramatically different crown shapes. In our study, we characterized transcriptional targets that are unique to each tooth type in human embryonic teeth, suggesting that specific patterns of signaling within each tooth type determines tooth germ identity. Future studies should connect the transcriptional targets back to its associated signaling pathways and validate current findings with immunohistochemistry and in situ hybridization.

Supported by: The University of Washington Dr. Douglass L. Morell Dentistry Research Fund

Jeffrey Lee

Lee JN, Hill C, Chi DL
UW Department of Oral Health Sciences

Objectives: One of the barriers to research use by policymakers is inadequate dissemination efforts by researchers. This study compares the effectiveness of two types of policy briefs to communicate dental research findings to policymakers.
Methods: In this observational study, we developed two types of policy briefs, data-focused versus narrative-focused, to communicate recent research findings that sugar sweetened beverage (SSB) intake leads to higher rates of tooth decay in Medicaid-enrolled children with special healthcare needs. We disseminated the policy briefs to 825 policymakers and staff in Washington state from three levels of government (city, county, and state). Each was randomly assigned to receive one of the two types of policy briefs and asked to complete a 22-item online questionnaire. There were four outcomes: whether the brief was understandable, whether the brief was credible, likelihood of use, and likelihood to be shared (each measured on a five-point Likert-like scale). Data were analyzed using the two-sided t-test to evaluate the relative effectiveness of the two types of policy briefs.

Results: At the time of analyses, there were 40 respondents out of 746 valid survey recipients. The mean age of study participants was 52.3±12.9 years, 60% were female, and 65% were white. Policymakers found both data and narrative briefs understandable (mean rating: 4.22±0.93 and 4.33±0.61, respectively; P=0.63) and credible (mean rating: 4.21±0.78 and 4.32±0.63, respectively; P=0.65), but were not likely to use (mean rating: 2.86±1.01 and 2.89±1.43, respectively; P=0.93) or share (mean rating: 2.9±1.12 and 2.53±1.39, respectively; P=0.36) either brief. There were no statistically significant differences between the data and narrative briefs across all four outcomes.
Conclusion: While policy briefs are understandable and credible to policymakers, they were unequally unlikely to be used or shared. Additional research should be done on how to develop policy briefs to improve the likelihood that they are used and shared by policymakers.

Supported by: The University of Washington Dr. Douglass L. Morell Research Fund and the William T. Grant Foundation Scholars Program

Lauren Lee

Lee L, Liu ZJ
UW Department of Orthodontics

Objectives: This study explores temporary and spatial alterations in the oropharyngeal airway and the tongue base in relation to the respiratory dynamics and airflow features in a minipig model. The hypothesis is that the normal tongue base is elongated and thinned to maximize airflow during respiration.

Methods: Eight 7–8-month-old Yucatan minipigs were used. Respiratory engaged time-series 2D MRI was acquired. The animals were further instrumented with sonometric crystals in the tongue base for quantifying 3D deformational changes and a pneumotach system for respiratory monitoring for the airflow variables and SpO2. The 2D MRI images of the oro- and nasopharyngeal and retroglossal airway spaces were analyzed for their cross-sectional areas in relation to the respiratory phases. The tongue base deformation was analyzed to link with collected airflow variables. Paired t-tests were applied to compare the outcomes between inspiration and expiration.

Results: Stereotyped changes in the width, length, and thickness of the tongue base were identified in relation to the respiratory phases. In respiration the tongue base elongated, widened, and thinned in inspiration, and vice versa in expiration. The range of elongated dorsal length was significantly larger in inspiration than that of shortening during expiration. Overall, the cross-sectional areas of naso- and oro- pharyngeal and retroglossal airway spaces presented distinct features in relation to the respiratory phases and were larger in inspiration than those in expiration. However, these differences were not significant.

Conclusion: The patterns of internal kinematics in the tongue base are closely related to the respiratory phases. In addition, there was a pattern in the change of the areas of the airway in relation to the respiratory cycle.

Supported by: University of Washington Dr. Douglass L. Morell Dentistry Research Fund and by the Grant R01DE028864 from NIH/NIDCR

Jason Lu

Lu, J., Greenlee, G., Rafferty, K., Mancl, L., Romanyk, D.L., Popowics, T.
UW Department of Oral Health Sciences

Objectives: Determining the orthodontic force necessary to generate periodontal ligament (PDL) strain and promote tooth movement is important to orthodontic practice. The objectives of this study were to design an orthodontic intrusion/tipping appliance for pig mandibular incisors ex vivo and utilize an in-Fiber Bragg Grating (FBG) sensor to measure strains generated within the PDL space under variable loading.

Methods: Springs calibrated to produce desired forces of 200g, 1000g, 1500g, and 2000g were mounted on ex vivo 2-month-old swine tooth-PDL-bone-complexes (n=6). Bi-cortical surgical screws (16mm) were placed 17mm inferior to the gingival crest in the mandibular symphysis. A sectional orthodontic arch wire (0.18” stainless steel) was bonded to the facial aspect of the incisors. Springs were stretched on the lingual between screw and arch wire, generating tension. A subgingival FBG sensor was placed on the facial of the left incisor PDL to collect peak strain data. ANOVA for a randomized block design was performed on the mean peak strain values followed by the Holm’s method post-hoc adjustment for multiple comparisons.

Results: Peak strain values overlapped between the four different spring forces, ranging from 1.5-10.3. There was a trend for the peak strain to increase with spring force; the peak strain was significantly higher for the 2000g spring force as compared to the other force levels (p-value <0.05). Conclusion: The FBG sensors detected differences in strain at the highest level of spring force used (2000g). Although these forces are higher than orthodontic tooth loads applied in humans, these findings demonstrate the efficacy of the ex vivo model and yield confidence that strain measures will be possible in future in vivo studies using a similar experimental configuration.

Supported by: The University of Washington Dr. Douglass L. Morell Endowment, University of Washington Dental Alumni Association, American Association of Orthodontic Foundation

Andrew Marchant

Marchant AD, Gray S, Ludwig DC, Dillon J
UW Department of Oral and Maxillofacial Surgery

Objectives: The COVID-19 pandemic has been an unprecedented crisis during which social distancing policies have been enacted and domestic violence (DV) has increased. The purpose of this study is to understand the impact of social distancing policies on the incidence and severity of oral and maxillofacial trauma (OMFT) secondary to interpersonal violence (IPV) and domestic violence.

Methods: A retrospective cohort study was designed, enrolling subjects presenting to an urban Level 1 trauma center in Seattle, WA, for evaluation and management of OMFT between January 1 and December 31 in the years 2018-2020. The primary predictor variable was evaluation of OMFT during periods with (2020: investigational group) or without (2018 or 2019: control group) social distancing policies. The primary outcome variables were the mechanism and severity of injury, defined as IPV, DV or neither, abbreviated injury scale (AIS), injury severity score (ISS). Descriptive, univariate and bivariate analyses were performed with statistical significance at p < 0.05.

Results: N=828; 737 (89%) IPV and 91(11%) IPV due to DV. The incidence of OMFT secondary to IPV or DV was unchanged (p=0.81, p=0.57 respectively). There was a nonsignificant increase in ISS for IPV (p=0.07) and no change for DV (p=0.46). AIS was unchanged for IPV (p=0.36). For DV, AIS was lower in 2020 compared to 2019 (p=0.04) but unchanged from 2018 (p=0.58). Half of the DV victims were male (50%-2018, 59%-2019, 53%-2020). Of these, 65% were under 18, representing the pediatric majority (62%).

Conclusion: The COVID-19 pandemic did not change the number or severity of OMFT cases secondary to IPV or DV. Interestingly, pediatric males were more likely to be victims of DV.

Supported by: The University of Washington Dr. Douglass L. Morell Research Fund

Elizabeth Saxe

Saxe E, Senturia K, Kim C.J., McKinney C.M.
Seattle Children’s Craniofacial Center

This qualitative and explorative project aims to determine the extent and scope of awareness that pregnant women have regarding the U.S Toxicology Program’s claim that fluoride is a neurotoxin. This project was based on interviews with a convenience sample of pregnant women across the United States asking about their knowledge, opinions, behaviors, concerns, and perspectives, around fluoride and pregnancy. This project aimed to document pregnant women’s primary concerns around chemicals, diet, and fluoride during pregnancy.

Published literature documenting pregnant women’s perspectives/views of fluoride in pregnancy is non-existent. The U.S. National Toxicology report demonstrates that fluoride is a common substance necessitating further research. This project is the first step in a larger project.

We thank the participants in our study for taking the time to contribute to this effort. This work was supported by the University of Washington Summer Research Fellowship Program (SURF) funded by the Morell Endowment and the University of Washington Dental Alumni Association.

Diala Sellk

D. Sellk, A. Sadr, D. C. Chan
UW Department of Restorative Dentistry

Objectives: This study aimed to compare the micro tensile bond strength (MTBS) of resin-modified glass ionomer (RMGI) to dentin treated with silver diamine fluoride (SDF) or SDF with potassium iodide (SDF+KI) with or without rinsing and polyacrylic acid (PAA) application.

Methods: Occlusal enamel of 60 extracted human posterior teeth was removed. Exposed sound dentin was polished with 800-grit silicon carbide paper and divided into three groups (n=10); Control: dentin surface rinsed with deionized water (DI); SDF: dentin treated with one drop of 38% SDF (Riva Star step 1, SDI) using a micro brush. SDF+KI: treated as in SDF followed by KI (Riva Star step 2). Two different protocols were followed to form six subgroups; RINSE+PAA: rinsed with DI, applied 20% PAA (Cavity Conditioner, GC) and rinsed off; No-Rinse: allowed to air dry with no-rinse/conditioner. RMGI (Fuji II LC, GC) was then placed on dentin followed by composite build-up. After 24h storage in DI water, MTBS beams (1mmx1mm) were produced and tested in Bisco Micro Tensile Tester. Data (MPa) was analyzed using ANOVA with multiple comparisons correction at a significance level of 0.05.

Results: The highest values with Rinse+PAA protocol were obtained in SDF+KI group (21.6±9.2), which were significantly different from SDF and Control (p<0.05). For No-Rinse protocol, SDF resulted in higher MTBS compared with SDF+KI and Control. Within SDF+KI No-Rinse (14.0±7.2) was significantly lower than Rinse+PAA (p<00.1), while there was no difference between rinsing protocols within Control or SDF (p>0.05).

Conclusion: Bond strength of RMGI to dentin was affected by SDF and SDF+KI application depending on rinsing and PAA protocol. SDF alone, either when rinsed followed by conditioning or when dried off from the surface without rinsing did not reduce RMGI bond to dentin. For SDF+KI, the rinsing and PAA application step was necessary to achieve dentin bond.

Supported by: The University of Washington Dr. Douglass L. Morell Research Fund

Michael Suk

Suk M, Cruz S, Randall C,
UW Department of Oral Health Sciences

Objectives: Though previously utilized sparingly in dental education, online instruction was rapidly implemented due to the COVID-19 pandemic and will likely continue being part of post-pandemic dental education to some degree. Thus, our goal was to identify dental student perspectives on online instruction and determine which aspects are viewed as most helpful and unhelpful for learning.

Methods: We conducted a qualitative study using semi-structured focus group interviews with dental students from all four years at a US dental school. The interview guide focused on the impact of online instruction on dental school experience and its effective/ineffective characteristics. The interviews were recorded, transcribed verbatim, and verified for accuracy. The transcripts were double coded using an inductive content analysis approach, with coded data synthesized into categories.

Results: Nineteen dental students participated (M age = 24.5 years; n=12 female, n=6 male, n=1 non-binary; n=9 first-year, n=5 second-year, n=4 third-year, n=1 fourth-year students). Students’ descriptions of the impact of online instruction on learning were mixed. Generally, students perceived online didactic instruction to be similar or enhanced over in-person instruction and online lab/clinical instruction to be worse. Camaraderie with faculty/students was negatively impacted but interactions with family/friends were positively impacted. Commonly described effective characteristics of online instruction were opportunities for increased accountability (in some classes), engagement with the lecture, and flexibility in scheduling; ineffective characteristics included decreased accountability (in other classes), lack of interactions with faculty/students, and feelings of intimidation on online platforms.

Conclusion: Dental students have mixed perceptions about the effectiveness of and their confidence in online instruction. Elements that increase engagement and accountability, such as SoftChalk modules and low-stakes assignments, may improve student learning for classes facilitated online. In implementing online instruction in the future, it will be important to consider how best to foster a psychologically safe online learning environment and ensure adequate student-student and student-faculty interaction.

Supported by: The University of Washington Dr. Douglass L. Morell Research Fund

Jennifer Tang

Tang, J., & Hujoel, P. P.
UW Department of Oral Health Sciences

Objectives: Leading dental editors stated that policy makers should ignore high-level evidence. Medical editors have not authored such a statement. The goal of this study was to assess whether these leading dental editors exhibit editorial bias in the studies they accept for publication.

Methods: A systematic search was conducted in PubMed to identify articles related to periodontal-systemic associations in 6 dental journals and 5 medical journals. Data on the reporting of statistical significance, dubious inference, level of adjustment for confounders in epidemiological studies, and publication of pivotal National Institutes of Health (NIH) trials was extracted.

Results: 240 articles were included in the study. Dental journals, when compared to medical journals, were 189 times more likely to include periodontal-systemic association content (odds ratio 189, 95% CI: 128-278) and 5 times more likely to report significant results (odds ratio 5.3, 95% CI: 1.5-18.3). Dental journals were more likely to include dubious inference, but the difference was not statistically significant (odds ratio 2.5, 95% CI: 0.6-11.1). Epidemiological studies in medical journals were more likely to adjust for confounders (p <0.05). Pivotal NIH-trials were exclusively published in medical journals (p <0.05).

Conclusion: These findings suggest that dental editors are biased towards publishing low-quality studies.

Supported by: The University of Washington Dr. Douglass L. Morell Research Fund

Tina Wang

Wang T, Huang G, Chan D
UW Department of Restorative Dentistry and Department of Orthodontics

Objectives: Common drawbacks with orthodontic adhesives are the time needed to light cure brackets and subsequently remove residual adhesive after bracket removal. We aim to investigate both the light curing and the debonding aspect by assessing debonding force values of orthodontic brackets using an experimental resin-based adhesive and different curing methods. The experimental adhesive is laser reversible and differences in debonding force between the laser-applied experimental adhesive and non-lased experimental adhesive were compared. We also explored the removal of residual adhesive after bracket removal.

Methods: 150 brackets were bonded on 75 extracted teeth. Brackets were bonded with an experimental laser-sensitive adhesive(R) and polymerized by either LED(Ascent) or Laser curing light (Monet). Traditional orthodontic adhesive 3M-Transbond(T) was used as control. Brackets were randomly assigned to the following groups: (1)T/LED, (2)T/Monet, (3)R/LED, (4)R/LED+450nm diode laser, (5)R/Monet and (6)R/Monet+450nm diode laser. The bonded specimens were mounted in resin, and shear bond tests were conducted using a universal testing machine (crosshead speed:5mm/min) to dislodge the brackets. Groups 4 and 6 were lased for 60 seconds with the 450nm laser before debonding. PVS impressions of retained adhesives on debonded surfaces after shear test and after polishing for subsequent SEM surface analysis. Data were analyzed using 2-way ANOVA and Tukey tests with α=0.05.

Results: There were significant differences in debonding forces between the LED and Monet groups prior to diode laser activation with mean bond forces from 40N-46N. After activation of the laser-sensitive adhesives, both LED and Monet groups showed 50% higher bond strengths from 62N-71N, which was statistically significant(P<0.001). More laser-sensitive adhesive was removed within 30 seconds regardless of activation with the diode laser.

Conclusion: The Monet laser light works as well as the LED for curing the two adhesives tested. Activating the experimental laser-sensitive adhesive with the diode laser increased the bond strength. Polishing the laser-sensitive residual adhesive was easier.

Supported by: The University of Washington Dr. Douglass L. Morell Research Fund

Elliot Willis

Elliot Willis-Orlando, Sydney Honnlee, Sophia DeVore, Zi-Jun Liu
UW Department of Orthodontics

Objectives: To investigate how the internal kinematics of the tongue base contributes to the swallowing during the natural feeding in a minipig model. It is hypothesized that the normal tongue base is shortened and thickened to propel the bolus during swallowing.

Methods: Eight 7 to 8-month-old Yucatan minipigs were used for the study. Under anesthesia, 8 sonometric crystals (SONO) were implanted in a cube-shaped region occupied by approximately 80% of the total volume of the tongue base. Electromyography (EMG) activity was recorded through wire electrodes inserted into jaw, tongue, palatal, hyoid, and pharyngeal muscles. X-ray videofluoroscopy was performed during unrestrained feeding and the bolus swallowing episodes were noted. The SONO and EMG were recorded simultaneously. The videofluoroscopic frames were digitized and movements of the soft palate, epiglottis, and tongue base were traced for each swallowing episode. The 3D changes of the tongue base and muscle activities corresponding to the digitized bolus swallowing episodes were quantified.

Results: During swallowing, SONO data revealed the dorsal and ventral length of the tongue base lengthened in dorsal and ventral regions. The posterior tongue base thickened more than the anterior and both dorsal and ventral regions widened in the anterior but narrowed in the posterior. All tongue, pharyngeal and hyoid, palatal, and jaw muscles activated during swallowing episodes with clear activity spikes in middle constrictor. The excursions of the oropharyngeal structures show the tongue base vertically thickening to contact the soft palate before horizontally lengthening to allow the passage of the bolus through the oropharynx.

Conclusion: The oropharyngeal structures are highly dynamic with the tongue base showing the largest moving range. The tongue base initially shortens and vertically thickens to engage the food bolus against the soft palate, before lengthening in coordination with the soft palate and epiglottis to propel the bolus through the oropharynx.

Supported by: Grant R01DE028864 from NIH/NIDCR, Summer Research Fellowship (SURF) of UW School of Dentistry, and University of Washington Dr. Douglass L. Morell Research Fund

4th Year Dental Student Research Program

Research Day 3

Samar Haghighi

Haghighi S, Sadr A
UW Department of Restorative Dentistry

Introduction: Laser curing lights have the advantage of low divergence, coherent and collimated light beam, which in comparison to LED curing lights, can improve the quality of composite restorations. The aim of this in vitro study was to measure the degree of debonding composite at the floor of a cavity in a class I restoration, using conventional LED curing light in comparison to monochromatic laser light.

Methods: In this study we created 40 specimens using Estelite flow quick resin composite in shape of a hollow cylinder and divided them into 8 groups. Our variables consisted of 2 composite groups: 3M bulkfill and Surefill SDR bulkfill (SF); 2 light curing systems: Monet laser curing light and Paradigm Deep cure; 2 curing depths: 1mm and 8mm. 3M Scotchbond Universal Adhesive was applied to the interior of each cylinder (the cavity space), according to the manufacturer’s instructions and cured using Paradigm deep cure. Subsequently, the cavity space was filled with the composite of choice and cured using the curing light of choice at our pre-determined depth. In order to assess the degree of debonding, we used Optical Coherence Tomography (OCT) to obtain a 3-D image of our cavity floor and calculate the C-factor. The curing process was recorded live to illustrate the debonding.

Results: The laser curing light on 3M composite showed less debonding in both 8mm and 1mm depths, compared to LED curing light. In SF composite the laser showed less debonding for 8mm depth and it showed no significant difference for 1mm depth, compared to LED.

Conclusion: Based on our findings laser curing light could decrease the time required for curing of bulkfill composites while reducing the debonding and improving the adaptation in a deep preparation, particularly when there is a distance between the curing light and surface of the cavity.

Supported by: UWSOD

Mariam Mustafa

Mustafa M, Taylor S
UW Department of Oral Medicine

Background: The size and shape pf the sella turcica has been previously analyzed in association with headaches, cleft palate and impacted teeth.

Objective: In this study, CBCT volumes are used to measure the volume of the sella turcica in relation to survey questionnaire on the severity and chronicity of orofacial pain symptoms.

Methods: A review of anonymized, self-reported TMD patient (TMD Impact study participant) survey responses to questions assessing severity and chronicity of TMD symptoms, headache symptoms and orofacial pain symptoms was performed. Each subject had completed a questionnaire and had a diagnostic CBCT image taken. The length, diameter and depth of the sella turcica were measure in the sagittal plane and the interclinoid distance was measured in the coronal plane by two reviewers. Their mean measurements were taken and used to measure the mean volume of the sella turcica which was then compared to the duration of pain reported.

Results: The mean length, diameter, depth and interclinoid distance of the sella turcica across 21 subjects were 8.79mm, 11.97mm, 8.26mm and 20.9mm, respectively. The mean duration of TMD pain for the subjects was 210.2 months. The mean duration of headache pain was 189 months. 17 subjects described their pain as recurrent, 3 as persistent and no response from one subject. The mean volume of the sella turica was 140.2mm3.

Conclusions: In this study there was no association between the volume of the sella turcica and the duration of pain (TMD or headache).