Current hydrophilic resin adhesives undergo hydrolytic degradation and show a decrease in bond strength over time. Nanoleakage and ultrastructure studies suggest that inadequately infiltrated collagen leads to enzymatic degradation and resin-dentin bond failure. Adequate degree of conversion (DC) of resin adhesives is also critical to resin-dentin bond strength and durability. The long-term goal of this dissertation is the realization of durable resin-dentin bond. It is hypothesized that ethanol-wet bonding technique (EW) may effectively facilitate the infiltration of hydrophobic monomers into hydrophilic acid-etched dentin by maintaining interfibrillar spacing, stiffening collagen matrix, and improving adhesive resin-demineralized dentin matrix miscibility. Chlorhexidine (CHX), Matrix Metalloproteinase-inhibitor (MMP-inhibitor), should further preserve collagen integrity and resin-dentin bond strength. Moreover, efficient photoinitiator systems that broaden light absorptivity and provide more reactive radicals may enhance polymerization. In this dissertation, a clinically-relevant EW protocol, 3×15s absolute ethanol rinsing, provided significantly higher microtensile bond strength (πTBS) of a hydrophobic resin (70%BisGMA/30%TEGDMA) to dentin as compared to water-wet bonding (WW). All groups showed no significant drop of πTBS after 1-year storage except EW without CHX application, showing marginally significant reduction in πTBS (p=0.0558) suggesting MMP-inhibition by CHX in EW. These results were consistent with subsequent experiments. EW maintained interfibrillar width and hybrid layer thickness for resin infiltration and retention. Monomer molar concentration across the hybrid layer was significantly higher in EW than WW. An application of 2% CHX diacetate further preserved collagen banding in EW. WW showed more generalized spotted nanoleakage, while EW presented localized reticular nanoleakage. The use of Irgacure 819 (BAPO) alone and in combination with benzoyl peroxide (BPO) or camphorquinone (CQ) increased DC of hydrophobic and hydrophilic resins over resins containing the CQ/amine (4E) control. Only BAPO and BAPO/BPO demonstrated significantly higher immediate shear bond strength than CQ/4E. Within the limitations of these studies, EW improved resin-dentin bond durability by maintaining collagen interfibrillar spaces for efficient infiltration of a hydrophobic BisGMA/TEGDMA resin resulting in significantly higher πTBS and monomer molar concentrations with less nanoleakage distribution within the hybrid layer than WW. CHX further maintained collagen integrity and πTBS in EW. BAPO is a potential alternative photoinitiator of dental resins.

The precise role that genes play in early craniofacial development and postnatal craniofacial growth are essential to understand dento-facial development overall. However, genotype-phenotype correlations between genetic variation of early craniofacial genes and adult craniofacial phenotypes is poorly understood. Thus, this thesis focused on identifying the genetic etiology underlying phenotypic variations present in malocclusion conditions. First, we performed genotype-phenotype association analyses between common variants in 82 craniofacial genes and phenotypic variations extracted from 2D and 3D pre-treatment dental records of individuals with malocclusion. This effort identified that variant rs2189000 upstream of TWIST1 is highly associated with mandibular body length and inclination and cranial base angulations which can lead to malocclusion. Next, via cell based functional assays, we discovered that rs2189000 disrupts a PITX2 binding site and also showed the direct regulation of TWIST1 expression by the PITX2 gene. Finally, we identified abnormal craniofacial phenotypes and malocclusion in Twist1 deleted mice including asymmetric snouts, domed cranial vaults, and changes in size and inclination of the cranial base, palate and mandible resulting in malocclusion and resembling the human phenotypes observed. Also, premature calcification of calvarial sutures and cranial base synchondroses were also observed in the mutant mice indicating a possible biological mechanism for the abnormal phenotypes detected. These results confirm that TWIST1 is an important regulator of postnatal growth and that genetic variation in TWIST1 can result in malocclusion. The continued identification of genetic etiological factors and their role in craniofacial growth will impact treatment and prevention of malocclusion and other craniofacial conditions

Objective: The purpose of this study was to evaluate the accuracy of surgical guides for dental implant placement fabricated by additive and subtractive techniques. Methods: A standardized mandible model (BoneModels, Castellón, Spain) was duplicated and the proposed implant position was performed from a diagnostic wax-up. An implant was placed in the printed model as a reference. Cone beam computed tomography (CBCT) was made with the radiographic surgical guide to design a surgical guide on BlueSky Plan 4 software. The .stl file of the surgical guide was exported and fabricated by two different techniques: additive (3D printing) and subtractive (milling). Fifteen surgical guides per group were used to place implants in the printed models. The angular deviations, differences in depth, coronal and apical deviations were measured using GeoMagic Control X software. Results were analyzed by Wilcoxon-Mann-Whitney (Wilcoxon Rank Sum) test and PERMANOVA (Permutational Multivariate Analysis of Variance). Intraclass correlation was used to analyze the reproducibility. A 0.05 level of significance was used, with Bonferroni multiple adjustment as needed. Results: There were no significant differences in accuracy of implant placement using additive technique vs subtractive techniques. The mean angular deviations between planned and actual position of implant in mesio-distal cross-section were 0.780±0.803 degrees for printed group and 0.772±0.724 degrees for the milled group. The analogous results in bucco-lingual cross-section were 1.601±1.223 degrees in in printed group and 1.767±0.762 degrees in the milled group. The differences in depth (mm) were measured in four aspects including mesial, distal, buccal and lingual. The mean differences in depth in the group that using printed surgical guides were 0.373±0.285 mm, 0.325±0.230 mm, 0.240±0.228 mm, and 0.247±0.168 mm in those 4 aspects, respectively. The mean differences in depth in the group that using milled surgical guides were 0.511±0.326 mm, 0.396±0.316 mm, 0.215±0.230 mm, and 0.230±0.122 mm in those four aspects, respectively. The mean coronal deviation showed 0.32 mm in the printed group and 0.27 mm in the milled group. For the apical deviation, the results of this study showed mean apical deviation 0.84 mm in the printed group and 0.80 mm in the milled group. Conclusions: No statistically significant difference was identified between the position of implant placed using surgical guide fabricated by the additive technique (3D printing) vs surgical guides fabricated by subtractive technique (milling). The 3D-printed surgical guide could be an alternative for guided-implant surgery with the benefits of high accuracy, ease of fabrication and reduction of laboratory time and materials, thereby increasing cost-effectiveness.

Introduction: The use of CBCT to visualize the relationship between the inferior alveolar canal and the mandibular third molar roots continues to grow as it is becoming the standard of care. It becomes important to understand the impact that luminance, one of the factors that affects the viewing conditions of digital images, has on appropriately assessing the third molar-canal relationship. To date, no study has assessed the impact of luminance on visualizing anatomic structures on CBCT. The aim of this study is to determine if there is a difference in the ability to appropriately assess the root development and the third molar-canal relationship on a medical grade monitor with four different luminance settings on CBCT. Materials and methods: 285 scans were randomized and evaluated by three calibrated and masked evaluators. The evaluations were completed on a Barco MDNC-3321 Nio Color 3MP monitor (Kortrijk, Belgium) monitor at four different luminance settings; 200 cd/m2, 300 cd/m2, 400 cd/m2, and 500 cd/m2. The gold standard was established by two board-certified oral and maxillofacial radiologists. All evaluations were performed in a controlled subdued environment lighting of less than 15 lux. There was a washout period of at least one week between each of the four evaluations by an observer. Results: The accuracy of two of the three evaluators was substantial to almost perfect independent of luminance. None of these assessments showed any statistical significance (P = 0.05). The accuracy of one evaluator was moderate to almost perfect for all evaluations with one assessment of one canal showing statistical significance (P = 0.05). Conclusion: There is no difference in the ability to appropriately assess the third molar canal relationship or the root development of third molars on a medical grade monitor at luminance settings between the range of 200 cd/m2 and 500 cd/m2 when viewed in a dimly lit room.

No description available.

POTENTIAL ANTIMICROBIAL METHODS FOR PROVISIONALIZING TEETH AFTER ENDODONTIC TREATMENT By Laura T. Garden, DDS A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry at Virginia Commonwealth University. Virginia Commonwealth University, 2018 Thesis Advisor: Garry Myers, DDS Department of Endodontics Objective:To evaluate the effectiveness of a Chlorhexidine soaked cotton pellet on bacterial leakage. Methods: Fifty-one extracted teeth, including six controls, were instrumented, obturated, and sealed with either a cotton pellet (CP), 2% Chlorhexidine soaked cotton pellet (CHX), or a Permaflo orifice barrier (OB). Each root was suspended between two chambers: the coronal chamber inoculated with brain heart infusion broth and colony-forming units of Enterococcus faecalis, the apical chamber with brain heart infusion broth and phenol red. The latter was checked daily for turbidity, indicating bacterial leakage. Results: All open and closed control groups had leaked by day 7. The average CP tooth survived for 13.1 days whereas the CHX and OB teeth leaked by an average of 5.8 days. Conclusion:There is insufficient evidence to support the use of a Chlorhexidine soaked cotton pellet. The results were not as expected and the study design should be re-evaluated.

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.