Histatins, a group of proteins produced by human salivary glands, have a variety of innate immune functions including the ability to: kill oral microorganisms, neutralize toxins, inactivate protease/collagenase activities, inhibit co-aggregation of oral bacteria, and inhibit lipopolysaccharide mediated activities. Hemagglutinin B (HagB), a virulence factor of the periodontal pathogen Porphyromonas gingivalis, induces a robust cytokine and chemokine response in human myeloid dendritic cells. In this study, I hypothesize that histatin 5 can attenuate a HagB-induced chemokine response. Objectives: To characterize an expanded cytokine and chemokine response induced in human myeloid dendritic cells by HagB, and to determine if prior incubation of HagB with histatin 5 attenuates these responses. Methods: In my first experiment, 0.040 M HagB was mixed with dilutions of histatin 5 and histatin 8 (Sigma, 0.04 to 40.0 M), incubated at 37C for 30 minutes, and added to 2 x 104 human myeloid dendritic cells (Lonza, Walkersville, MD). At 24 hours, culture media was removed, and 6 cytokines and chemokines (pg/ml) were determined in cell-free supernatants (Millipore, Billerica, MA) using the Luminex 100 IS instrument (Luminex, Austin, TX). In my second experiment, 0.040 M HagB was mixed with 40.0 M histatin 5 only (e.g., 1:1000), incubated at 37C for 30 minutes, and added to 2 x 104 human myeloid dendritic cells. At 0, 1, 2, 4, 8, 16, and 24 hours post-inoculation, culture media was removed, and 26 cytokines and chemokines (pg/ml) were determined in cell-free supernatants. Results: In both experiments, human myeloid dendritic cells incubated with HagB produced Th1, Th2, and Th17 cytokines (IL-2, IL-12(p70), IFN-, IL-3, IL-4, IL-5, , IL-15, IL-17); pro-inflammatory cytokines (IL-1, IL-1, IL-6, TNF-, IL-12(p40); anti-inflammatory v cytokines (IL-10, IL-13, IFN2); chemokines (CXCL8/IL-8, CXCL10/IP-10, CCL2/MCP-1, CCL3/MIP-1, MIP-1b, CCL11/eotaxin); and colony stimulating factors (IL-7, G-CSF, GM-CSF). Histatin 5 significantly attenuated (p < 0.05) the IL-8 response induced by HagB at 8 - 16 hours and to a lesser extent, the IL-6, GM-CSF, MCP-1, MIP-1α, MIP-1β, and TNF-α response. Conclusion: Histatin 5 is an important salivary component capable of attenuating an IL-8 response. Together with human beta defensin 3, another peptide previously shown to attenuate pro-inflammatory cytokines, histatin 5 may help control and contain oral infection and inflammation by down regulating IL-8 chemotactic response.

Objectives: This retrospective cohort study aimed to assess the survival time and factors associated with survival of anterior composite-resin restoration placed at the University of Iowa, College of Dentistry (UICOD). Methods: Patients at the UICOD who had anterior composite restorations placed between 1995-1997 and could be followed through 2013 were included in this study. Factors included: patient age and gender, tooth type (central or lateral incisor, or canine) and location (maxillary or mandibular), restoration size (1, 2, 3, 4 and more surfaces), provider type (dental student, graduate student, faculty), and clinic (operative, family, or other clinics) where the initial restoration placed. Survival time of a restoration was defined as how long a restoration lasted from the day of placement until the day of subsequent treatment. Subsequent treatment included: restorations, veneer and/or crowns, root canal therapy, and extraction. One restoration per patient was used for the study. Statistical analyses consisted of the Kaplan-Meier analysis and Cox regression (alpha=0.05). Results: Of the 668 subjects (mean±SD age=55±13 years and 60.8% females) who fulfilled the inclusion criteria, the mean±SD survival time of composite resin restoration was 11±7 years and an overall survival rate was 43.3%. Patients' gender, age, tooth location, and clinic type were not significantly associated with the survival time of composite resin restoration. Cox regression model indicated that significant differences in the restoration hazards were found on tooth type (p=0.002), provider type (p=0.003) and restoration sizes (p=0.0072). Central (HR=1.59; CI=1.23-2.07) and lateral (HR=1.36; CI=1.03-1.79) incisors had a significantly higher hazard ratio (HR) than canines, and faculty had significantly lower HR than undergraduate students (HR=0.68, CI=0.55-0.85). Restorations sizes one surface (HR=0.6; CI=0.44-0.81) and two surfaces (HR=0.65; CI=0.48-0.88) had significantly lower HR than four and more surfaces restorations. Conclusion: The mean and median survival time of anterior composite restoration at UICOD was 11 and 13 years, respectively. Tooth type, provider type, and restoration size were significant predictors for the survival time of anterior composite-resin restoration.

Tooth decay is a serious health risk and a significant contributor to health care costs in both industrialized and developing nations. Tooth decay is the end result of a change in the balance of plaque ecology towards more acidogenic and aciduric bacterial species. The primary force facilitating this change is an increase in the amount and frequency of simple carbohydrate, in particular, sucrose ingestion by the host. The acidity of plaque increases after host ingestion of fermentable carbohydrates and this promotes demineralization of the tooth enamel which is restored by salivary buffering and mineral deposition. Frequent and prolonged periods of low plaque pH drive cycles of enamel homeostasis towards demineralization, which ultimately leads to the formation of dental caries. Streptococcus mutans is the main etiologic agent in the development of dental caries. The cariogenic potential of S. mutans is based on their ability to produce and tolerate large amounts of acid and to adhere to and accumulate large numbers on the surface of a tooth. They are capable of efficiently fermenting a variety of simple carbohydrates and can produce high concentrations of acid, even in a low pH environment. However, it is the ability of S. mutans to rapidly synthesize copious amounts of water-insoluble and water-soluble glucan from dietary sucrose, which allow the bacteria to accumulate large enough numbers to dominate the dental plaque and significantly lower the plaque pH. Synthesis of glucan is mediated by glucosyltransferase enzymes and is crucial to sucrose-dependent adherence and to the cariogenicity of S. mutans. S. mutans also makes four non-GTF glucan-binding proteins: GbpA and GbpD are secreted and released proteins that contain a region that is homologous to the glucan-binding domains of the Gtf enzymes, and GbpC is a cell wall bound protein that confers the property of dextran-dependent aggregation during stressful conditions, and GbpB whose glucan-binding properties appear secondary to its role in cell-wall metabolism. It was hypothesized that Gbps A, C, and D primarily function to shape the architecture of S. mutans biofilms which in turn affects the cariogenicity of S. mutans. To test this hypothesis, a panel of Gbp mutants was constructed from S. mutans strain UA130 that encompasses all deletions of Gbps (GbpA, GbpC and GbpD) individually and in combination. Specific pathogen-free rats were infected with the WT S. mutans UA130 strain along with each of the Gbp mutants, were fed a high sucrose diet for seventy days, and were then scored for caries. Significant attenuation of caries was observed in some but not all gbp mutants. Biofilms were also grown and analyzed via confocal microscopy and COMSTAT image analysis software. Architectural differences were found with all of the gbp mutants when compared to the wild-type, most notably the mutant strains lost significant biofilm depth. Several of the architectural parameters correlated with caries attenuation. It was concluded that deletion of one or more Gbps resulted in a partial loss of the cohesive properties of S. mutans biofilms and changes in biofilm architecture. In several cases this resulted in significant attenuation of cariogenicity but not a complete loss. The architectural changes that resulted from this loss of biofilm cohesiveness and the specific combinations of Gbp deletions that lead to significant attenuation suggested specific roles for each Gbp in biofilm formation. Furthermore, the attenuation of Gbp mutant strains could not be explained by differences in acidogenicity or aciduricity among the mutants. Therefore it was concluded that Gbps A, C and D make profound contributions to biofilm architecture and changes in biofilm architecture, as a result of loss of Gbp-mediated cohesion, affects S. mutans cariogenicity.

Objectives: The aim of the current study is to establish the reliability of linear cephalometric measurements made on mandibles and their respective 3D printed models created from different voxel resolutions from a cone beam CT machine. Materials and methods: Ten dry mandibles obtained from the Department of Oral Pathology, Radiology and Medicine at The University of Iowa College Of Dentistry were used for this study. All mandibles were scanned on the i-CAT FLX cone beam CT machine (Imaging Sciences International, LLC, Pennsylvania, USA) using voxel resolutions of .30mm, .25mm and .20 mm in a 16cm x 8cm field of view using 360° rotation. The 3D models were reconstructed and saved as .STL files using 3D Slicer software and send to a 3D printer for printing. Two observers measured the 10 mandibles and 30 3D printed models. The measurement were repeated on 50% of the samples after at least one week interval. Cronbach’s alpha and intraclass correlation coefficient were calculated to measure reliability. Results: Good to excellent interobserver and intraobserver reliability was achieved across most of the measurements. There was no difference in reliability across models made from different voxel sizes. Conclusion: The current study successfully showed that the reliability of measurements made on 3D printed models of dry skull mandibles created using fused deposition modeling technique using images of different voxel sizes from an i-CAT FLX CBCT machine are valid, reproducible, and reliable and can be used for diagnostic and clinical purposes.

Objectives: To evaluate the influence of five different displays on the diagnosis of artificial caries-like lesions on restored and unrestored tooth surfaces. Materials & Methods: 60 extracted human teeth (30 premolars and 30 molars) were selected. All molars had class II cavities prepared and restored. Half of the premolars and molars were randomly selected and a 7mm² area was exposed to a demineralizing solution for 120 days. Phantoms with four teeth (two premolars and two molars) were created. Periapical radiographs were obtained on RVG 6100 digital sensor (Kodak Dental Systems, New York, USA). The images were evaluated under subdued lighting on five viewing displays (Barco MDNC-3321, NEC Wide, Apple iPad Pro, Microsoft Surface Pro 4 and Dell flat panel monitor) by three observers using a five-point rating scale. Sensitivity (Sn), specificity (Sp), accuracy (Ac) and Receiver Operating Characteristic (ROC) curves and their areas under the curves (AUC) were calculated and compared by Analysis of variance and post-hoc Tukey test. Intraobserver and interobserver agreement were accomplished after a three month interval observational.. The observer agreement was evaluated with the Cohen’s kappa test. Results: Even though the tablets slightly improved accuracy over the medical monitors, there was no statistically significant difference in sensitivity, specificity, accuracy or AUC among the five monitors when the same tooth group was considered (p< 0.05) with the exception of the iPad Pro which had a specificity p-value of 0.014 when comparing the two materials within the iPad Pro. Conclusion: There is no perceivable disadvantage to utilizing a higher resolution tablet viewing platform for plane images. No advantage to the medical grade monitors over the tablets or the consumer monitor. Both tablets improved detection accuracy on the unrestored premolars. However further evaluation especially in a clinical lighting setting is warranted to evaluate a displays impact on observer performance within common clinical practice lighting parameters.

My PhD projects were secondary analyses of data from a prospective study conducted at the University of Alabama at Birmingham. Two cohorts of low socioeconomic status, African-American children from Perry County, Alabama, were invited to participate. Children in the 1st Cohort (Cohort 1, n=98) were approximately six years old at baseline and followed for 6 years, while children in the 2nd Cohort (Cohort 2, n=95) were approximately one-year-old at baseline and followed for five years. For the first dissertation project, the prevalence and incidence of dental decay were assessed for children in Cohort 1. The findings of this report showed that 60-70% of the children had dental decay experience at each of the six annual exams. Approximately a third of the children had additional new tooth decay from age 6 to age 12. For the second project, risk factors for time to dental decay occurrence were assessed using a relatively new analytic approach which allowed the use of time-dependent risk factors for children in Cohort 1. This was the first time for this analytic approach to be used in the dental literature, although it is widely used in medical research. The merit of using this technique was that, since dental decay risk factors can change with time, the value of the risk factor was allowed to change over time. The second project showed that about 29% of the children had their first permanent tooth decay event during the six-year follow-up. Final results showed that greater consumption of water, milk and 100% juice were associated with lower dental decay hazards, while greater consumption of added-sugar juice was associated with greater hazard of having an event. The third PhD project was designed to assess the patterns of and the relationship between initial Mutans Streptococci detection and dental caries experience occurrence in African-American pre-school children with mean age of 1 year at baseline. The third project dealt with the MS variable as a “time-dependent variable”, using a statistical analysis called “Extended Cox hazards modeling”. To the knowledge of the author, this is the first published study which has used this relatively new analytic approach to assess the complex relationship between MS detection and dental caries experience. In addition, in the third project, the behavioral risk factors for having a positive salivary MS test were assessed. This study found that median MS acquisition survival (when 50% of the children had positive salivary MS test) was 2 years and mean survival time was 2.09±0.09 among African-American children who had valid MS acquisition tests (n=99). Approximately 23% of the children did not have any positive salivary MS test by age 4 years. Multivariable analysis showed that not having a positive salivary MS test at any of the study exams was associated with having acute illness in the previous 6 months and being recruited into the study before 10 months of age. Results of extended Cox proportional hazards modeling showed a significant relationship between having a caries experience event at any given time during the follow-up period and having a positive salivary MS test at any point in time (HR=2.25, 95% CI 1.06-4.75).

Significant efforts have been undertaken in medicine to identify hospital and primary care service areas (eg, the Dartmouth Atlas of Health Care) using patient origin information. Similar research in dentistry is nonexistent. The goal of this dissertation was to develop and refine methods of defining dentist service areas (DSAs) using dental insurance claims. These service areas were then used as spatial units of analysis in studies that examined relationships between utilization of oral health services, dentist workforce supply, and service area characteristics. Enrollment and claims data were obtained from the Iowa Medicaid program for children and adolescents ages 3-18 years during calendar years 2008 through 2010. The first study described rates of treatment by orthodontists in children ages 6-18 years. Orthodontic DSAs were identified by small area analysis in order to examine regional variability in utilization. The overall rate of utilization was approximately 3%; 19 DSAs were delineated. Interestingly, children living in small towns and rural areas were significantly more likely to have received orthodontic services than those living in metropolitan and micropolitan areas. The second study identified 113 DSAs using claims submitted by primary care dentists (ie, general and pediatric dentists). Characteristics of these primary care DSAs were then compared with counties. Localization of care was used as a measure of how well each region approximated a dental market area. Approximately 59% of care received by Medicaid-enrolled children took place within their assigned service area versus 52% of care within their county of residence. Hierarchical logistic regression was used in the final study to examine the influence of spatial accessibility and the importance of place on the receipt of preventive dental visits among Medicaid-enrolled children. Children living in urban areas were more likely to have received a visit than those living in more rural areas. Spatial accessibility assessed using measures of dentist workforce supply and travel cost did not appear to be a major barrier to care in this population. More studies are needed to explore the importance of spatial accessibility and other geographic barriers on access to oral health services. The methods used in this dissertation to identify service areas can be applied to other populations and offer an appropriate method for examining revealed patient preferences for oral health care.

No description available.

The prevalence of obesity is continually rising in developed countries like the United States. Based on the association between periodontitis and obesity and the relationship between periodontitis and peri-implantitis, it is important to understand the implications of obesity on peri-implant health. A potential relationship between obesity and peri-implant health has practical, biological and financial implications. The primary objective of this study was to determine the association between obesity as measured by the body fat indices (body mass index (BMI), waist circumference (WC), and body fat percent (fat %)) and the levels of inflammatory biomarkers in saliva. In addition, this study explored the correlations between the levels of these biomarkers in saliva versus their corresponding levels in peri-implant sulcular fluid (PISF) and gingival crevicular fluid (GCF) samples collected from the same subjects. Periodontal maintenance patients (N=73) were enrolled in this cross-sectional study. Anthropometric measurements (BMI, WC, and body fat %), intraoral assessment (full mouth plaque index, periodontal, and peri-implant comprehensive examinations) and unstimulated whole saliva samples were collected from the subjects. GCF and PISF were also collected. Levels of interleukin (IL)-1α, IL-1β, IL-4, IL-6, IL-8, IL-10, IL-12(p40), IL-17α, tumor necrosis factor (TNF)-α, osteoprotegerin (OPG), letpin and C-reactive protein (CRP) in saliva, GCF and PISF were analyzed using multiplex immunoassays. Statistical analyses were performed to explore the correlations of interest. Data from 63 subjects were included in the analysis. No statistically significant correlations were noted between any of the body fat indices and any of the biomarkers measured in saliva (p>0.05 in all instances). A significant positive correlation was noted between salivary and GCF levels of IL-1α (r=0.29, p=0.0232), IL-8 (r=0.29, p=0.0207) and between saliva and PISF levels of leptin (r=0.32, p=0.0284). The employed linear model also revealed the significant impact of tooth brushing frequency on the salivary levels of IL-1α, IL-1β and TNF-α (p<0.05). Based on this cross-sectional study of 63 patients, I conclude that there was no statistically significant correlation noted between salivary inflammatory biomarkers and any of the obesity measures. However, the levels of key inflammatory markers in saliva strongly correlated with their corresponding levels in GCF/PISF. In addition, frequency of tooth brushing was also related to levels of certain biomarkers in GCF/PISF.

Periodontal disease is a chronic inflammation of the gingiva and periodontium that leads to progressive destruction and irreversible damage to the supportive structures of the teeth. It affects nearly half of the United States population and is a particular risk factor in adults older than 65 years of age. Oral microorganisms assemble in plaque as a polymicrobial biofilm and Porphyromonas gingivalis, an important secondary colonizer in oral biofilms, has been implicated in periodontal disease. Although the protective functions of various salivary molecules such as antimicrobial proteins have been delineated, lipids present in saliva and on the oral mucosa have been largely ignored and there is growing evidence that the role of lipids in innate immunity is more important than previously realized. In fact, recent studies suggest that sphingoid bases and fatty acids, which exhibit potent broad spectrum antimicrobial activity against a variety of bacteria and fungi, are likely important innate immune molecules involved in the defense against oral bacterial and fungal infections. However little is known about their spectrum of activity or mechanisms of action. In addition, the effects of these lipids that are endogenous to the oral cavity have not been explored against oral bacteria. In this study I hypothesized that oral mucosal and salivary lipids exhibit dose-dependent antimicrobial activity against P. gingivalis and alter cell morphology and metabolic events. To test this hypothesis, I first examined the effects of two fatty acids: sapienic acid and lauric acid, and three sphingoid bases: sphingosine, dihydrosphingosine, and phytosphingosine, against a variety of gram-positive and gram-negative bacteria including P. gingivalis. Using broth microdilution assays to determine minimum inhibitory and minimum bactericidal concentrations, I show that antimicrobial activity against bacteria is dose-dependent, lipid specific, and microorganism specific. Kill kinetics were also variable across each bacteria-lipid combination. Upon examination of select bacteria-lipid combinations via scanning and transmission electron microscopy, different morphologies were evident across all treatments, demonstrating differential activity of each lipid for a particular bacterium as well as for each bacterium across different lipids. In addition, all sphingoid bases and fatty acids were taken up and retained in association with P. gingivalis cells and could be extracted along with bacterial lipids and separated using thin layer chromatography. Using a combination of two-dimensional in-gel electrophoresis and Western blots followed by mass spectroscopy and n-terminus degradation sequencing, I show that sapienic-acid treatment induces a unique stress response in P. gingivalis, as evidenced by the ability of P. gingivalis to upregulate a set of proteins involved in fatty acid biosynthesis metabolism and energy production, protein processing, cell adhesion, and virulence. Finally, utilizing flow cytometry and confocal microscopy, I assessed the effects of oral antimicrobial lipids against a representative host cell and describe oral lipid concentrations that are both antimicrobial to P. gingivalis cells and non-cytotoxic to the representative host cells tested. Combined, these data strongly suggest that sphingoid bases and fatty acids found within the saliva and on oral mucosa likely do contribute to the innate antimicrobial activity of saliva, mucosal surfaces, and skin and this dose-dependent activity is both lipid specific and bacteria specific. This information adds to current knowledge of the innate functions of endogenous lipids in the oral cavity. With bacterial resistance to current antibiotics increasing, the exploration of new antimicrobial agents is important and these lipid treatments may be beneficial for prophylactic treatments or therapeutic intervention of infection by supplementing the natural immune function of endogenous lipids on skin and other mucosal membranes.