Research Day 2021

Poster Presentations 2021

Graduate Students

Poster Presentations-Grad

Alaa A. Alkhatee, MSa, Erika D. Lease, MDb, Lloyd Mancl, PhDa, Donald L. Chi, DDS, PhDa
UW Department of Oral Health Sciences

Background: Dental clearance is typically part of the evaluation process prior to placement on the lung transplant waiting list. Individuals with cystic fibrosis (CF) are thought to be at low risk for dental disease. We hypothesized that individuals with CF in need of lung transplantation would have lower dental disease prevalence and shorter waitlist evaluation time than individuals with non-CF lung diseases.

Methods: We analyzed electronic health record data for individuals who received a lung transplant between 2011 and 2017 at the University of Washington (Seattle, WA, U.S.A.) (N=280). We defined the presence of untreated dental disease using data from dental clearance forms. An individual was considered to have untreated dental disease if they had an oral infection or needed major dental treatment at time of initial dental evaluation. Waitlist evaluation time was defined as the time, in days, from the initial evaluation by a transplant pulmonologist to placement on the lung transplant waiting list. We used logistic and linear regression models for hypothesis testing.

Results: The prevalence of untreated dental disease did not differ by CF status (CF 27.7% vs. non-CF 27.6%; 95%CI: – 0.14, 0.14; P=0.99). There was no difference in waitlist evaluation time for transplant recipients by CF status (Geometric mean in days [GM]: CF 154 vs. non-CF 179; P=0.78). Differences in the two study outcomes remained insignificant after adjusting for age, sex, smoking status, and lung function.

Conclusions: Contradictory to the CF dental health paradigm, our results indicate no difference in the prevalence of untreated dental disease or in waitlist evaluation time by CF status. These findings provide further evidence that individuals with CF are not at low risk for dental disease. These findings are particularly concerning in the context of increased survival of individuals with CF, which makes it critical to ensure life-long optimal oral health.

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), and the Dr. Douglass L. Morell Dentistry Research Fund.

a Department of Oral Health Sciences (UW)
b Department of Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine

Elise Ellingsen DDS, Avina Paranjpe BDS, MS, MSD, PhD.
UW Department of Oral Health Sciences

Regenerative endodontic procedures (REPs) are an important component in the treatment plan for immature teeth with necrotic pulps. Stem cells of the apical papilla (SCAP) are vital for successful regeneration of the dental pulp. Previous studies have shown N-acetyl cysteine (NAC) aids in the differentiation of SCAP making them more resistant to apoptosis. However, the pathway of cell survival and differentiation is still unknown. Hence, the aim of this study was to evaluate the effects of NAC on the survival and differentiation gene expression of SCAP.

Human SCAP were cultured and exposed to either NAC for 24 hours, non-treated (negative control) and Dexamethasone (positive control). RNA was extracted from the cells. RNA was reverse transcribed to cDNA. The cDNA was analyzed using TaqMan Array Human Signal Transduction Pathway Fast plates and TaqMan Array Human Osteogenesis Pathway Fast plates. The plates were analyzed using Real time-PCR. Data were analyzed using a one-way analysis of variance (ANOVA).

Real time-PCR analysis showed SCAP pre-treated with NAC had upregulation of anti-apoptotic genes (BCL2, BCL12L1), genes promoting DNA synthesis (CDKN1A, CCND1), and genes promoting cell adhesion (FN1) and cell proliferation/differentiation (FOS). There was a downregulation of genes involved with breakdown of extracellular matrix (MMP10 and MMP7) and prostaglandin synthesis (PGES2).

SCAP treated with NAC have an upregulation of pathways related to the maintenance of the cell cycle, proliferation and differentiation thereby protecting these cells. This research outlines the differentiation pathway of NAC treated SCAP suggesting that NAC could be used effectively during REPs.

Supported by:  Douglass L. Morell Grant

Dianne Gan, DMD,a Muhammad Naeem Iqbal MSc,b Qianhui Xu DMD,c Zhijian Shen PhD,b Van Ramos, Jr, DDS,a and Kwok-Hung Chung, DDS, MS, PhDa
UW Department of Restorative Dentistry

Background: This in vitro study was to evaluate the shear bond strength of resin cement to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) when using zirconia-alumina composite (ZAC) particles to conduct airborne-particle abrasion.

Materials and Methods: 160 zirconia disks (4.0 mm x 6.6 mm) were fabricated from 4 commercially available zirconia blanks using computer-aided manufacturing technology. These were further divided into four surface treatment groups: as-sintered controls (ZR0), alumina airborne-particle abrasion (ABC), air abrasion with ZAC particle at 0.2MPa (2ZA), and air abrasion with ZAC particle at 0.4MPa (4ZA). Surface roughness (Ra) and area roughness (Sa) of specimens from each group were measured. Following the application of an adhesive (Scotchbond Universal, 3M ESPE), resin cement (RelyX Ultimate, 3M ESPE) buttons (4.0 mm x 6.6 mm) were fabricated for shear bond test conducted using a universal testing machine (n=10). ANOVA, Tukey HSD tests, and regression analysis were used for data analysis at α=.05. Scanning electron microscopy (SEM) was used to observe changes of the zirconia surface and failure modes of each group.

Results: The mean of Ra and Sa values ranged from 0.27μm to 0.74μm and 0.48μm to 1.48μm, respectively. The mean ±SD bond force values ranged from 272.6 ±41.4 N to 686.7 ±152.8 N. Statistically significant higher shear bond force values were obtained using airborne-particle abrasion than the controls (P < 0.05). No significant differences were found among any of the air abrasion treatment groups (P > 0.05). SEM observation revealed differences between the zirconia surfaces air-abraded with alumina versus the ZAC particle. The spherical ZAC particles create micro-craters on the zirconia surface

Conclusions: Surface treatment of zirconia with sharp-edged alumina or the spherical ZAC abrasives improved the bonding strength between zirconia and resin cement.

There are no statistically significant differences in shear bond force values between airborne-particle abrasion surface treatment groups.

Supported by:  Stanley D. Tylman Research Grant from the American Academy of Fixed Prosthodontics; Department of Restorative Dentistry, University of Washington [Task 821], and the Swedish Research Council [grant number 2016-04191].

a Restorative Dentistry, UW
b Department of Materials and Environmental Chemistry Arrhenius Laboratory Stockholm University, Stockholm, Sweden.
c Department of Epidemiology, Columbia University Mailman School of Public Health, New York, NY

Gem H1,2, Diab A2, Swanger J2, Welcker M2, Clurman B2
UW Department of Oral Health Sciences

Introduction: Head and neck squamous cell carcinoma (HNSCC) represents the sixth most common cancer worldwide. HPV-negative HNSCC is particularly aggressive due to certain alterations in cell cycle genes. Specifically, deregulation of the G1/S checkpoint commonly occurs with the amplification of CCND1 and deletion of CDKN2A. This genomic profile is characteristic of many HPV-negative HNSCCs, and it makes them a good candidate for the targeted therapy palbociclib, a selective CDK4/6 inhibitor, to restore the G1/S checkpoint. While this drug has shown promise in preclinical HNSCC models, innate and acquired resistance during clinical trials have emerged as serious problems. The objectives of this study are to understand mechanisms of resistance related to CCNE1 up-regulation and to examine the role of FBXW7 deletion, an E3-ubiquitin ligase that regulates CCNE1 activity.

Methods: We used CRISPR technology to knockout FBXW7 in a CCND1 amplified, CDKN2A deleted, HNSCC cell line called FaDu. Using EdU incorporation and flow cytometry, we examined cell cycle dynamics of wild-type and FBXW7 knockout FaDu cells in response to palbociclib. We also used in vitro kinase assays to correlate CCNE1 hyperactivity to drug response.

Results: We showed that FBXW7 knockout confers partial resistance to palbociclib in cells that were previously sensitive. Furthermore, we showed that CCNE1 is the likely downstream mediator of this phenotype as its hyperactivity in FBXW7 knockout cells correlates with resistance.

Conclusion: By demonstrating partial resistance in FBXW7 knockout cells, we revealed a novel biomarker to palbociclib response in a HNSCC cell line. As the application of this targeted therapy expands into treatment regimens for HNSCC, predicting tumor response through biomarker testing will be an important step for successful treatment. By characterizing a resistance mechanism linked to FBXW7 deletion, we hope our data can inform the appropriate use of palbociclib in patients who will be responsive to this drug.

Supported By: NIH T90DE021984 & NIH 5R01CA215647

1 Department of Oral Health Sciences (UW)
2 Human Biology, Fred Hutchinson Cancer Research Center

Melinda Lee DMD, Avina Paranjpe BDS, MS, MSD, PhD
UW Department of Endodontics

It is a common practice for clinicians to pre-bend a rotary file and spray it with Endo-Ice (1,1,1,2 tetrafluoroethane)(TFE). TFE helps to maintain this bend and facilitates file placement into the canal. Many previous studies have investigated various properties of NiTi rotary files. However, there are limited studies that have demonstrated the effects of cold on cyclic fatigue resistance of NiTi files. Hence, the aim of this study is to investigate the effects of TFE on cyclic fatigue resistance in two different file systems.

Vortex Blue (VB) 20/0.04 files and ProTaper Universal (PTU) F1 files were used. The files were sprayed with TFE for 3 seconds and inserted into plastic blocks with a 45° curve and operated per manufacturer’s instructions until failure. Control group files were not exposed to cold. Number of cycles to failure (NCF) was calculated by multiplying time (in minutes) until failure by RPM. The results were analyzed using Student t-test.

The results demonstrated that both the VB group and the PTU group exposed to cold had significantly lower NCF compared to their respective control groups.

This research demonstrates that exposing files to cold could dramatically affect the cyclic fatigue resistance of NiTi files. Hence, clinicians should be cautious about the use of TFE on NiTi files for instrumentation.

Shivani Suvarna, BDS; Armand Bedrossian, DDS, MDS; Van Ramos, Jr. DDS, FACP; Kwok-Hung Chung, DDS, PhD, FADM
UW Department of Restorative Dentistry

Purpose. The aim of this in vitro study was to assess the effectiveness of using fiber reinforcement to enhance the flexural strength of the transitional implant-supported fixed dental prosthesis (TISFDP).

Material and Methods. 140 acrylate denture resin plates (64x12x5mm) with two holes, 7mm in diameter were fabricated using heat-polymerized (Lucitone-199) and CAD/CAM prepolymerized (AvaDent) materials to simulate a chair-side fabrication of the TISFDP. Specimens were divided into 7 groups (n=10) according to the airborne-particle abrasion of titanium cylinder (Straumann) surface and locations of fiber reinforcement ribbons (Ribbond-ULTRA); no cylinder surface abrasion and no fiber addition specimens were controls. The prosthetic screws were hand-tightened on a customized-fixture with analogs. Specimens were picked up using a 50:50 mix of chemically polymerized resin (QYK; Holmes) and repair resin (Dentsply). All specimens were stored in a water bath at 37°C for 24-hours before the four-point bending test (ASTM standard-D6272) conducted using a universal testing machine at a cross-head speed of 1mm/min. Maximum failure load values were recorded and analyzed with 2-way ANOVA and Tukey tests at α=0.05.

Results. The flexural strength values obtained ranged from 55.4±8.3MPa to 140.9±15.4MPa. The flexural strength decreased significantly when fiber was attached on the titanium cylinder surface (p<0.05). There were no statistically significant differences in flexural strength values between specimens with and without titanium cylinder surface abrasion (p>0.05). Statistically significant improvement in flexural strengths were observed in specimens with fibers added around the repair holes (p<0.05) buccally and lingually, combined with some fixation screw fractures before catastrophic failure of specimens.

Conclusions. Fiber reinforcement significantly improved the flexural strength of denture base resins only if added around the repair holes on the tension side at the site of initiation of crack propagation. Even when the specimens underwent catastrophic failure, the segments remained attached to each other with the fiber.

Summer Research Fellowship (SURF) Program Students

Poster Presentations-Surf

Hovander D, Sadr A
UW Department of Restorative Dentistry

Objectives: The aging and mastication stresses induce microcracks in the dental hard tissues, potentially leading to tooth fracture. There are currently no standard clinical procedures for observation and removal of these cracks. This in vitro study aimed to use optical coherence tomography (OCT) for non-invasive evaluation of the effectiveness of current clinical techniques to remove deep coronal dentin cracks.

Methods: Standard dentin cracks were induced on the pulpal floor human posterior teeth (n=40) using a diamond disc, resembling cracks extending from marginal ridges. The specimens were randomly assigned to 5 treatment groups to remove the cracks; I) #1156 bur, II) ½ round carbide bur, III) airborne particle abrasion, IV) #2 steel bur, and V) #8847 diamond bur. Before and after the crack removal, OCT scans were collected. 3D image registration was performed to analyze the amount of dentin removed and the dimensions of cracks initiated and/or propagated in each treatment group. Data were statistically analyzed at a significance level of 0.05.

Results: Dimensions of the removed dentin structure as a result of crack treatment were the largest in the particle abrasion group exhibited by the average removal depth and width of 1,124 and 1,017 µm, respectively which was significantly different from all bur groups (Man-Whitney, p<0.005). On the other hand, particle abrasion resulted in smallest crack propagation in each dimension, which was significantly different from all bur groups (Man-Whitney, p<0.01). All burs resulted in a degree of crack formation and there was no difference in crack dimensions among bur groups (p>0.05).

Conclusion: Mechanical removal of dentin cracks by conventional clinical technique using a dental bur leads to formation and propagation of the crack. Particle abrasion is a preferred technique in terms of preventing crack propagation while the amount of tissue removed may be more difficult to control than burs.

Supported by: The UW Dental Alumni Association

Isabelle Hwang1, Leigh Armijo2, Lloyd Mancl1, Tracy Popowics1
UW Department of Oral Health Sciences

Objectives: Understanding how the fluid and fibrous components of periodontal ligament (PDL) contribute to the transmission of stress to the alveolar bone during mastication is important to understanding orthodontic tooth movement. It is the goal of this study to compare the strain and force required to displace a swine incisor by 0.5 mm between the intact PDL and reduced-fiber PDL, and between different age groups.

Methods: The mandibles of 5 younger pigs and 5 older juvenile pigs were collected, and a subset of the central incisors were used (nyounger=9, nolder=7). A material testing machine (MTS) and in-fiber Bragg grating sensors (FBG) placed within the PDL were used to measure strain induced by a compressive load to 0.5mm over 15 repetitions. Incisors were tested in saline with intact PDL fibers and with fiber reduction (fiberotomy/collagenase treatment). Incisors run under both conditions (11) and run under one condition (5) resulted in 27 trials.

Results: We discovered that the PDL space develops more strain when PDL fibers are fully intact vs. reduced (median difference -9.6; 95% CI [-44.2, -4.1] and that the intact PDL fatigues over time (p-value<0.0001). Both younger (p-value<.0001) and older pigs (p-value = 0.023) showed time dependent reduction in peak force and this reduction may be greater in the PDL’s of younger pigs.

Conclusion: Our findings propound that the fibrous component of the PDL is important to maintaining the viscoelasticity of PDL and is essential to its function. We attribute the finding of PDL fatigue to the stress-relaxation of the PDL and theorize that age group differences in PDL fatigue may be the result of differences in PDL fiber composition or density, a direction of potential future research.

Supported by: The Douglass L. Morell Dentistry Research Fund and an AAOF Ormco Center Award.

1 Department of Oral Health Sciences (UW)
2 Department of Orthodontics (UW)

Liu TC, Randall CL
UW Department of Oral Health Sciences

Objectives: Dental students experience disproportionately high rates of stress, anxiety, and depression. However, little research has focused on how dental education programs can address student wellness. The overall objective of this project was to understand dental students’ perceptions about mental health and their preferences for wellness programming.

Methods: This qualitative study involved focus group interviews with current second-, third-, and fourth-year dental students (N=20) from a single U.S. dental school. We developed a study-specific semi-structured interview guide probing school-related influences on mental health, wellness practices students already use or want to learn, and preferences for future wellness initiatives. The interviews were recorded, transcribed, verified for accuracy, and coded using inductive content analysis.

Results: Participants described two types of institution-specific influences on mental health: structural and cultural. They frequently noted that relationships with those from their own class, and those from other classes and with faculty, promote a culture of wellness within the dental school. Three types of currently used wellness practices were endorsed: independent, those involving others, and those involving university resources. Participants believed the school should do more—structurally and operationally—to promote wellness. Interest in wellness-related initiatives was high, and strongest for experiential (versus didactic) programming outside of the classroom. Participants believed such initiatives should facilitate breaks, relaxation, socialization, opportunities for mentorship/support, and/or fun. Among others described by participants, factors to consider for the successful implementation of wellness-related programs included regular (versus one-off) frequency, inter-class involvement, pairing with existing social events, and planning by administrators (versus student groups).

Conclusion: Dental students prefer experiential wellness programs organized by the school and offer considerations for program development and potential operational and cultural changes to improve wellness. The findings of this first study identifying student perspectives about wellness initiative targets and preferences can be used to inform their future development.

Supported by: The UW Dental Alumni Association

Xu E, Daubert D, Jain S
UW Department of Periodontics

Objectives: Recent evidence suggests that the presence of titanium particles sloughed off from dental titanium implants is significantly associated with both peri-implantitis and an increase in the population of Veillonella species in subgingival plaque. We aim to begin investigation of this relationship by determining, in vitro, if the presence of titanium particles alters the growth rate or the immune stimulating potential of V. parvula.

Methods: Veillonella parvula, Streptococcus gordonii, and Porphyromonas gingivalis were grown separately in 96-well plates, either alone or with titanium particles of varying concentrations for 48 h. Titanium particles were commercially bought and suspended in water or scaled from commercially available pure titanium disks using an ultrasonic scaler. Single-species biofilm growth was quantified using a crystal violet assay. To determine changes in the immune stimulating potential of V. parvula, HEK293 cells grown in 96-well plates were exposed to media or V. parvula, with or without titanium particles, and the TLR4 response was measured 18 h to 20 h later.

Results: V. parvula showed increased biofilm growth in the presence of titanium particles, with the most growth found in the wells with the most titanium particles. S. gordonii and P. gingivalis, on the other hand, did not show any differences in biofilm growth in the wells with titanium particles. There were no changes in the robust immune stimulating potential of V. parvula in the presence of titanium particles.

Conclusion: V. parvula demonstrated increased single-species biofilm growth in the presence of titanium particles. This increase in biofilm growth in response to titanium particles was specific to V. parvula in that it was not observed in S. gordonii and P. gingivalis. V. parvula does not exhibit increased TLR4 stimulation in the presence of titanium particles. This study may help inform the development of treatment strategies for peri-implantitis.

Supported by: The Dr. Douglass L. Morell Research Fund

Xu K, Chan D, Pozhitkov A, Chung W, Jain S
UW Department of Restorative Dentistry

Objectives: A common problem with dental implants is that they are susceptible to biofilm formation, leading to peri-implantitis. Gold-titanates are a group of compounds that hold promise as an antibacterial coating that could mitigate this issue. We aim to investigate possible formation of gold titanate compounds through measuring antibacterial activity of zirconia washers vacuum coated with layers of gold and titanium. This will be assessed through zone of inhibition assays using Porphyromonas gingivalis, as it is a bacterial species commonly associated with peri-implantitis.

Methods: 12 zirconia washers were coated under vacuum with a constant level of titanium but a varying level (light, medium, heavy) of gold. The washers themselves had sections that were coated with gold, titanium, and both. Porphyromonas gingivalis was grown from frozen stock before inoculating into liquid media. Media containing P. gingivalis was spread plated on TYHK plates, and washers were placed in the middle (N=3). Plates were incubated for 5 days under anerobic conditions. Plates were analyzed with photometric analysis to measure zones of inhibition.

Results: The only coating group that had significant zones of inhibition as compared the control bare washer was the light gold coating group (p<.05, two-sided t-tests). There was no significant difference between zones of inhibition for sections of washers coated with gold only, titanium only, and both gold and titanium (p<.05, two factor ANOVA).

Conclusion: A lighter gold coating over titanium causes a statistically significant zone of inhibition while a heavier coating has minimal effect on the growth of P. gingivalis. Furthermore, it does not seem that gold and titanium together have greater antibacterial properties than each by themselves. These observations go against our initial hypotheses since possible titanate formation should be supported by a mixture of gold and titanium. Further studies should be done to elucidate these phenomena.

Supported by: The Dr. Douglass L. Morell Research Fund

4th Year Dental Research Program

Poster Presentations-4th year

Chiu A, Chen YW, Deng S, Steele S, An SW, Sadr A
UW Department of Restorative Dentistry

Objectives: Monolithic glass-ceramic crowns have become increasingly popular because of optimal esthetics and superior mechanical strength. However, limited data exist regarding the effect of axial wall height (AWH) when factoring in adhesive cementation of crowns and bonding between tooth and lithium disilicate (LD) surfaces. The purpose of this in-vitro study was to evaluate the effect of various AWH on the debonding of LD crowns under fatigue loading.

Methods: Extracted maxillary third molars were prepared for glass-ceramic crown at 20-degrees using a customized jig. Samples were divided into four groups (0 mm, 1 mm, 3 mm, 4 mm) and scanned using the 3Shape TRIOS3 Scanner. Crowns were then designed, milled, and cemented with PANAVIA SA Cement and Clearfil Universal Bond Quick following manufacturer protocol. Samples were subjected to fatigue loading with 100N at 30-degree inclination on the functional cusp using a chewing simulator (SD Mechatronik CS-4). Number of cycles until failure and mode of failure were recorded. Debonded samples were examined under microscopy and optical coherence tomography (OCT).

Results: No tooth or crown fractures were observed during 2 months of continuous loading in this study. The 0 mm group debonded under 250,000 cycles, 1 mm group debonded after 5 million cycles, while 3 mm and 4 mm groups remained intact beyond this stage. Microscopic evaluation of debonded specimen revealed that debonding had mainly occurred at the cement and LD interface, and the majority of cement remained on the dentin surface. OCT imaging confirmed microscopy findings in all debonded samples.

Conclusions: Adhesively cemented LD crowns with a short (1 mm) AWH resisted debonding for 5 million cycles which was less than that of 3 mm (6.25 million) and 4 mm preparations; however, it could be considered as clinically acceptable. Preparation of tooth for bonded restorations should consider tooth tissue preservation over excessive reduction for optimal resistance.

Supported by: The Dr. Douglass L. Morell Research Fund

Foy, T, Taylor, S
UW Department of Oral Medicine
Background: Ossification of the stylohyoid complex (SHC) is a relatively common occurrence- in people. When presenting in combination with head and neck pain and/or other symptoms, such as dizziness or difficulty swallowing, this combination of findings has been named Eagle’s Syndrome (ES).

Objectives: The present study utilized anonymized subject CBCT imaging and TMD Impact Study Questionnaires to compare the mean questionnaire response values of specific questions (relating to symptoms associated with ES) and the length of SHC’s. H0: The length of the SHC has no association with the questionnaire response value of TMD Impact Study participants.

Methods: A cohort study was conducted on 132 patients ¬¬ – these subjects were returning patients included at one site of a multi-center TMD study1. Each subject had completed a number of questionnaires and had a diagnostic CBCT image taken for TMJ assessment. This data was used for this study. Questions related to symptoms associated with ES were selected. The responses to these questions were scored (0= no, 1=yes). The length of the SHC’s were measured by two observers. Chi-squared test were used to compare the two categorical variables, mean question response value and SHC length (>25mm or <25mm). The statistical significance level was set at 0.05.

Results: It was determined that 22 (16%) of all 132 patient SHC’s were within normal limits bilaterally (<25mm) and 70 (53%) were elongated bilaterally (>25mm). Statistical analysis of responses to questions 1 (p =. 66), 2 (p= .46), 3 (p = .71) and 4 (p = .67) independently showed no significance correlation to SHC lengths (p <.05).

Conclusions: In this study, there was no association between the length of the calcified SHC and the number of positive reports of ES symptoms, in this TMD study population.

Supported by: The Dr. Douglass L. Morell Research Fund

Ninneman S, Zarrabi I, Prajapati S, Daubert D, Wang I, Hsu YT
UW Department of Periodontics

Background: Lateral window sinus floor elevation (LSFE) allows implant reconstruction in the posterior maxilla. The aims of this retrospective study were (1) to determine demographic or surgical factors related to Schneiderian membrane perforation (SMP) during LSFE, (2) to investigate the outcomes of implants placed in grafted sinuses.

Methods: The retrospective study was approved by the UW institutional review board. All data was retrieved from an existing database of electronic health records. Demographic and surgical-related factors at SFE were recorded. Outcome variables included the incidence of SMP during LSFE, implant survival, and prosthetic complications. Fisher’s exact test was used to compare any differences in abovementioned factors between groups with or without SMPs.

Results: Sixty-four patients (65 ±12.36 years) with a total of 82 sinuses and 110 implants placed in the grafted sinuses were included in the study. At the time of LSFE, 5 patients were diabetic and 9 patients were currents smokers. Forty-nine patients were diagnosed with periodontitis and 11 patients had gingivitis. For the surgical factors, the window of LSFE were outlined by rotary burs in 31 sinuses and piezoelectric devices in 32 sinuses, respectively, with 19 being unknown. Prophylactic antibiotics were given for 62 patients before LSFE. Twenty-one sinuses were perforated during surgery, with an incidence of 25.6%. However, none of these factors showed significant association with the incidence of SMPs. Among 110 implants placed in the grafted sinuses, 8 required additional osteotome prior to implant placement, and 2 of these were in areas of prior SMP. Eighteen implants required GBR simultaneously with implant placement, with 8 of these in areas of prior SMP. The overall implant survival rate is 97.2% with 5 prosthetic complications and 14 implant complications.

Conclusion: With the study limitations, LSFE is a reliable procedure with promising survival rates of implant placed in grafted sinus.

Supported by: The University of Washington School of Dentistry Elam M and Georgina E Hack Memorial Research Fund and the Dr. Douglass L. Morell Research Fund.

Other Dental Students

Poster Presentations-other

Seminario, A.L., DeRouen, T., Cholera, M., Liu, J., Phantumvanit, P., Kemoli, A., Castillo, J. and Pitiphat, W
UW Center for Pediatric Dentistry

Although oral diseases are largely preventable, they are among the most non-communicable diseases globally, and they disproportionately burden disadvantaged communities, especially within low- and middle-income nations. The COVID-19 pandemic has highlighted the social, economic, and health inequalities in our society, including the existing global oral health inequalities. There is a shortage of dentist-scientist all around the world, especially in developing countries, such as Thailand. The National Institute of Dental and Craniofacial Research (NIDCR) and Fogarty International Center (FIC), joined efforts on creating research capacity in oral health in South East Asia through the Fogarty International Center Training Program in Clinical, Public Health and Behavioral Oral Health Research for Thailand (2006 – 2016). The University of Washington (USA), Thammasat University (Thailand) and Khon Kaen University (Thailand) partnered to conduct short-, medium- and long-term training programs to build regional oral health research capabilities. Investing in research has not only impacted trainees’ career development but enhanced advancement of oral health research of South East Asia. The success of partnership calls for expanding oral health research training in other low-income countries.

Supported by: Two grants funded by both, the National Institute of Dental and Craniofacial Research and Fogarty International Center (D43 TW007768 and D43 TW009071).

Eftekhar M, Lee L, Salamati A, Liu ZJ
UW Department of Orthodontics

Objectives: Hypermobility, a common symptom of periodontitis, is due not only to the loss of alveolar bone, also to the associated alteration in the periodontal ligament (PDL). The present study hypothesized that the structure of the PDL Sharpey’s fibers is altered by experimental periodontitis in the young pig model.

Methods: Six three-month-old pigs were periodically inoculated with four types of periodontal bacteria, along with a ligature around the last maxillary deciduous molar for eight weeks to induce periodontitis (PG). Eight same-aged pigs served as the control group (CG). Upon euthanasia, the harvested molar blocks were sectioned coronally and stained with either hematoxylin & eosin (H&E) or Sirius Red (SR). The structures of PDL on H&E-stained images were first reviewed. Then, each adjacent SR-stained section was chosen, and the images were captured at the region close to the apex of the mesial roots under polarizing light microscopy. Sharpey’s fiber numbers in each bundle (Bundle size), total bundle numbers, the connection of the bundle to the root cementum and alveolar socket, as well as bundle angulations to the long axis of the molar, were quantified in the defined area 500μm apical to the root apex. Three images were captured and quantified in each animal by using Metavue software.

Results: Compared to the CG, the PG showed the following features: 1) less in the total bundle number and fiber numbers in each bundle; 2) more interrupted fiber bundles; 3) more oriented toward the cervical in the bundle angulation.

Conclusions: These results suggested the experimental periodontitis leads to the altered structures of PDL Sharpey’s fiber in young pigs.

Supported by: NIH/NIDCR R21DE023127 and Sunstar Preventative Dentistry Award

Lee JN, Scott JM, Chi DL
UW Department of Oral Health Sciences

Dental caries is a significant public health problem for low-income children with special health care needs (CSHCN). We evaluated associations between oral health behaviors (e.g., diet, fluoride, dental care) and caries for CSHCN enrolled in Medicaid, a health insurance program for low-income populations that provides comprehensive dental coverage for children. We recruited 116 CSHCN ages 7 to 20 years from Medicaid enrollment files in Washington State. Caregivers completed a 166-item questionnaire and children received a dental screening. The outcome was dental caries, defined as total pre-cavitated, decayed, missing, or filled tooth (PDMF) surfaces. We ran log-linear regression models and generated prevalence rate ratios (PRR). The mean age of study participants was 12.4±3.1 years; 41.4% were female, and 38.8% were white. The mean PDMF surfaces was 6.4±9.4 (range: 0 to 49). Only sugar-sweetened beverage intake was significantly associated with dental caries. CSHCN who consumed >4 sugar-sweetened beverages per week were significantly more likely to have tooth decay than those who consumed no sugar-sweetened beverages (PRR: 2.58; 95% CI: 1.37, 4.85; P<0.01). Sugar-sweetened beverages are an important target for future behavioral interventions aimed at preventing dental caries in low-income CSHCN.

Special thanks to Dr. Joanna Scott for assisting with statistical analyses and Dr. Donald Chi for encouragement, guidance through manuscript publication, and mentorship.

Faculty and Postdoctoral Fellows

Poster Presentations-faculty

Huang X 1, Xu KA 2, Jain S 3, Chan D 1
UW Department of Restorative Dentistry

Objectives: Ultraviolet (UV) light is one of the technologies widely used for inactivating bacteria, viruses, and fungi in disinfection of surfaces. UVC irradiation (200-280 nm) is the main source of the germicidal effect. The present study was to evaluate the disinfection performance of LED and mercury lamp based conventional UV germicidal irradiation (UVGI)

Methods: Porphyromonas gingivalis was spread on the TYHK-agar plates. Plates were covered with lids lined with tin foil, except for a square window to expose the agar. Then the plates were treated by the following three commercial portable UVGI sanitizers at the wavelength of 253.7 nm for 1s, 5s, and 10s respectively. No UVC treatment and Ampicllin were used as negative and positive controls, respectively. All the plates were then incubated in an anaerobic condition for 48h. To further evaluated Brand C, stimulated saliva was spread, treated by UVC for 1s, 5s, and 10s respectively and then incubated.

Lamp Power (W) Intensity (mW/cm2)
Brand A Mercury 4 3
Brand B Mercury 5 2.5
Brand C LED 80 65

Results: Brand A could kill P. gingivalis after 5s treatment, while Brand B needed 10s. Brand C with LED lamps could kill all the P. gingivalis after almost 1s. For much denser colonies from saliva, Brand C could reduce the density significantly after 1s and kill almost all the microorganisms after 5s.

Conclusions: LED UVGI is much more effective than the mercury lamp based conventional UVGI, probably due to higher power and output UV intensity.

Supported by: Department of Restorative Dentistry

1 Department of Restorative Dentistry (UW)
2 School of Dentistry (UW)
3 Department of Periodontics (UW)

Roston RA, Mirando AJ, McLellan WA, Pabst DA, Hilton MJ, Roth VL
UW Department of Orthodontics

Sutures, the fibrous joints between bones, serve important roles in the growth and mechanics of vertebrate skulls. Based on their varying mechanical functions, sutures display different collagen fiber orientations and bone morphologies (e.g., abutting, interdigitated, beveled). While most mammal skulls, including those of humans, possess beveled and overlapping sutures, the histological structure, ontogeny, and biomechanics of these sutures are largely unknown. Cetaceans (whales and dolphins) in particular have taken bone overlap to the extreme—some sutures cover nearly the entire surface of the underlying bone—and possible functions of this extensive bone overlap in cetaceans have been widely speculated. To inform investigations of functional hypotheses for overlapping sutures, we examined the maxillo-frontal suture in neonatal and adult bottlenose dolphins (Tursiops truncatus) using CT, microCT, and histological methods. We found that in the neonates, the bony margins of the suture were smooth and the sutural fibers were oriented parallel to the bone margins. In contrast, in the adult, the maxilla and frontal were interlocked with rugose interdigitation of the bones and a complex arrangement of collagen fibers. This adult morphology suggests this suture in cetaceans, and perhaps overlapping sutures more generally, forms a strong joint that resists complex mechanical loading.

Supported by: NIH DE021984; Grant-in-Aid, Wainwright Fund; Duke University’s Arts & Sciences Council on Faculty Research

Dogan S, Baioumy Y, Lyu L, Yip E, Hamann J, Yucesoy DT, Fong H, Bulmus V, Sarikaya M
UW Department of Restorative Dentistry

The goal of this research is to develop a biomimetic strategy to facilitate regeneration of an acellular cementum (aC)-PDL interface by forming an integrated hybrid of mineral layer functionalized with the peptides derived from the key proteins of the periodontium, which with further research, can be adapted for clinical regenerative therapeutic strategies. Four ambitious specific tasks are set forth to realize the overarching objective: (i) In vitro remineralization of demineralized cervical root dentin using shADP5, a mineralizing peptide derived from amelogenin; (ii) Functionalization of remineralized dentin surface with chimeric peptides with Hap binding and PDL cell-favorable attachment/signaling functions, identified via machine learning tools and high-throughput screening methods or designed according to sequences known in literature; (iii) Quantitative determination of preferential PDL cell attachment/proliferation and orientation, over gingival epithelial cells, on biomimetic hybrid peptide-mineral layer; and (iv) Identification of biomimetic hybrid layer yielding structurally integrated aC-PDL junction. The lab team has optimized a remineralization strategy that provided pathways to achieve several goals. Namely, functional stable remineralized layer has been formed on the surface of dentin forming continuous mineral layer that penetrates into exposed dentin tubules. This achievement is the key step in the formation of a functional cementomimetic layer towards building the PDL. The team is in the process of identifying the signaling peptides derived from relevant proteins towards the generation of structurally integrated aC-PDL interface. The presentation will give highlights of the latest developments.

Supported by: SoD-Spencer Fund

Fong H, Yucesoy DT, Dogan S, Bulmus V, Sarikaya
UW Department of Materials Science and Engineering

In convergent science approach that involves genetic engineering, biochemistry, bioinformatics, molecular biology, dental science and technology and materials sciences and engineering, we have developed a combination of highly versatile platform in which biomineralizing peptides are used for controlling tooth remineralization towards developing practical treatments of diseases with the demineralization origin. Our team has developed a platform technology based on the design of peptides from proteins that epitomize their key functions. Using amelogenin, the key protein in enamel mineralization (as well as Fetuin-A, osteopontin, OC90 and matrix-gla protein), we developed a set of Amelogenin-Derived Peptides (ADPs) with hydroxyapatite (HAp) binding and mineralization properties. In particular, using shADP5, a 15-AA long peptide, we demonstrated biomimetic restoration of human (in vitro) and rat (in vivo) enamel (incipient caries), and occlusion of (human) dentin tubules (in vitro) through remineralization. In all cases, the newly formed mineral layer was demonstrated to be structurally, chemically, and mechanically integrated into the underlying enamel and dentin tissues, the critical step to achieve functional restoration of the tooth with long-term durability. Using the protein-derived peptides we have developed formulations, such as solution, gel, lozenge, varnish, and paste as well as antimicrobial and osteointegrative biogenic coatings for implants (each in the R&D pipeline at different stages of development) and demonstrated their in vitro and in vivo efficacy using demineralized teeth. With the goal of bringing the formulations to the level of the minimum viable products, the team is currently planning to initiate human trials in the coming months, a critical step before for practical OTC and clinical implementations.

Supported by: WA-LSDF, CoMotion Gap Funds, SoD-Spencer Fund, and Amazon-Catalyst

Sarikaya M, Gunderman H, Hamann J, Rodriguez J, Yucesoy DT, Fong H, Dogan S
UW Department of Materials Science and Engineering

Based on convergent science approach, including computational biology, bioinformatics, biochemistry, oral health science, and materials sciences, the goal of this project has been to identify functional domains within the native proteins of periodontium that are known to control mineralization and regeneration of cementum, cementum-PDL junction, and PDL tissues. Three specific tasks are set forth to realize the overarching objective: (i) Identification of domains within the known periodontium-related proteins using a ML- and bioinformatics-based algorithms which incorporate HTP experimental selection of peptides using combinatorial mutagenesis combined with next-generation sequencing; High-throughput characterization of identified peptides using custom peptide-arrays and massively parallel fluorescent cell attachment, proliferation and toxicity assays; and (iii) Iterative redesign and refinement of robust (chimeric) peptides with multiple functions through conformational and functional deep mutational scanning. Although the bench work has been restricted significantly because of the pandemic, in this Spencer project the progress has been highly unusually rapid with diverse spinoff projects with implications for future progress in many fronts in the Lab’s quest for peptide guided biomimetic dental restoration, repair, and therapeutics of for innovative oral care. In the first part of the project, the team is developing a machine learning (ML) algorithm to discover short sequences from biomineralizing and signaling molecules with a biomineralization function in dental tissues. This part of the project has focused on the identification of mineral binding and signaling domains in a variety of Hap-binding proteins, including amelogenin, as well as Fetuin-A, osteopontin, OC90 and matrix-gla protein. Once the consensus sequences with affinity to HAp are identified within proteins that undergo biomineralization, the next step is to demonstrate the relatedness of species’ proteins via looking purely at their domains, and characterizing the mineralization characteristics of chosen sequences. In parallel, the team has been optimizing the high-throughput system for biomimineralization screening studies. In the next step, the high-throughput system is focusing on generating high volume biomineralization data for assessing the effect of peptide sequences derived in Part 1 of this project on the mineral formation characteristics (rate, morphology, mineralogy, etc).

Supported by: SoD-Spencer Fund

Yucesoy DT, Fong H, Hamann J, Hall E, Dogan S, Sarikaya M
UW Department of Materials Science and Engineering

Dentin hypersensitivity (DH) is a common oral health condition that affects the quality of life. The exposure of dentin tubules due to demineralization is a prevalent cause of DH. Despite being a widespread ailment, no long-term solution exists to permanently address DH. Current treatments are designed to alleviate the pain by either using desensitizers or blocking tubules by secondary precipitates, which are transient due to their loose integration with dentin. Ideally, DH treatment should reproduce a mineral layer on dentin that extends into the tubules and reestablishes the structural and mechanical integrity of the tooth to achieve permanent durability. Here, we describe a biomimetic treatment that utilizes a mineralization-directing peptide, sADP5, derived from amelogenin using biochemical and bioinformatics design principles. Demineralized human mid-coronal dentin, mimicking DH, were subjected to repeated rounds of peptide-guided treatment. The structure, composition, and nanomechanical properties of the remineralized dentin is analyzed by cross-sectional scanning electron microscopy imaging, energy dispersive X-ray spectroscopy and nanomechanical testing. The occlusion of exposed dentin tubules achieved through a layer-by-layer mineralization process that formed continuous mineral layer penetrating into the tubules. The elemental analysis provided Calcium/Phosphate composition, similar to that of hydroxyapatite. The average hardness and reduced elastic modulus values for the mineral layer were significantly higher than those of the demineralized and sound human dentin. The interface between the mineral layer and the underlying dentin remained integrated after 90 days of thermal aging with no marginal separation. These results suggest that structurally robust and mechanically durable interface forms between the mineral layer and underlying dentin that can withstand long-term thermal stresses encountered in the oral environment. The remineralization procedures described herein could provide a foundation for the development of effective biomimetic oral care treatments for a wide range of demineralization-related ailments and, more specifically, a potent long-term solution for DH.

Supported by: CoMotion Gap Funds, SoD-Spencer Funds