Joseph L. Hagan

Novel Dental Composites Reinforced with Zirconia-Silica Ceramic Nanofibers

OBJECTIVE To fabricate and characterize dental composites reinforced with various amounts of zirconia-silica (ZS) or zirconia-yttria-silica (ZYS) ceramic nanofibers. METHODS Control composites (70 wt% glass particle filler, no nanofibers) and experimental composites (2.5, 5.0, and 7.5 wt% ZS or ZYS nanofibers replacing glass particle filler) were prepared by blending 29 wt% dental resin monomers, 70 wt% filler, and 1.0 wt% initiator, and polymerized by either heat or dental curing light. Flexural strength (FS), flexural modulus (FM), energy at break (EAB), and fracture toughness (FT) were tested after the specimens were stored in 37°C deionized water for 24h, 3 months, or 6 months. Degree of conversion (DC) of monomers in composites was measured using Fourier transformed near-infrared (FT-NIR) spectroscopy. Fractured surfaces were observed by field-emission scanning electron microscope (FE-SEM). The data were analyzed using ANOVA with Tukeys Honestly Significant Differences test used for post hoc analysis. RESULTS Reinforcement of dental composites with ZS or ZYS nanofibers (2.5% or 5.0%) can significantly increase the FS, FM and EAB of dental composites over the control. Further increase the content of ZS nanofiber (7.5%), however, decreases these properties (although they are still higher than those of the control). Addition of nanofibers did not decrease the long-term mechanical properties of these composites. All ZS reinforced composites (containing 2.5%, 5.0% and 7.5% ZS nanofibers) exhibit significantly higher fracture toughness than the control. The DC of the composites decreases with ZS nanofiber content. SIGNIFICANCE Incorporation of ceramic nanofibers in dental composites can significantly improve their mechanical properties and fracture toughness and thus may extend their service life.

Amelogenin-assisted ex vivo remineralization of human enamel: Effects of supersaturation degree and fluoride concentration.

The formation of organized nanocrystals that resemble enamel is crucial for successful enamel remineralization. Calcium, phosphate and fluoride ions, and amelogenin are important ingredients for the formation of organized hydroxyapatite (HAP) crystals in vitro. However, the effects of these remineralization agents on the enamel crystal morphology have not been thoroughly studied. The objective of this study was to investigate the effects of fluoride ions, supersaturation degree and amelogenin on the crystal morphology and organization of ex vivo remineralized human enamel. Extracted third molars were sliced thin and acid-etched to provide the enamel surface for immersion in different remineralization solutions. The crystal morphology and mineral phase of the remineralized enamel surface were analyzed by field emission-scanning electron microscopy, attenuated total reflection-Fourier transformed infrared and X-ray diffraction. The concentration of fluoride and the supersaturation degree of hydroxyapatite had significant effects on the crystal morphology and crystal organization, which varied from plate-like loose crystals to rod-like densely packed nanocrystal arrays. Densely packed arrays of fluoridated hydroxyapatite nanorods were observed under the following conditions: σ(HAP)=10.2±2.0 with 1.5±0.5 mg l(-1) fluoride and 40±10 μg ml(-1) amelogenin, pH 6.8±0.4. A phase diagram summarizes the conditions that form dense or loose hydroxyapatite nanocrystal structures. This study provides the basis for the development of novel dental materials for caries management.

Toxicology screening results : Injury associations among hospitalized trauma patients

BACKGROUND Substance abuse is associated with injuries, but these associations have not been well characterized by type of substance and injury type. METHODS A cross-sectional study of patients selected for toxicology screening compared those with positive and those with negative test results for drugs and alcohol. RESULTS Patients with positive alcohol toxicology results were more likely to have violence-related and penetrating injuries than patients with negative results. However, after adjustment for positive cocaine toxicology results, the association between alcohol and penetrating injury was no longer significant. Positive test results for any drug were not associated with any specific injury type, but cocaine was independently associated with violence-related injury. The associations of alcohol and cocaine with violence-related injury appear to be additive. In contrast, opiates were independently associated with nonviolent injuries and burns. CONCLUSIONS Alcohol and cocaine use is independently associated with violence-related injuries, whereas opiate use is independently associated with nonviolent injuries and burns.

Management of giant sialoliths: Review of the literature and preliminary experience with interventional sialendoscopy

To report our experience with management of giant salivary stones via a combined approach technique using salivary endoscopy (CA) and results of a review of current literature related to giant salivary stones.

Force decay of elastomeric chains - a mechanical design and product comparison study.

Objectives To evaluate the percentage force decay of elastomeric chain products utilizing three different design mechanisms simulating canine retraction; and to evaluate the percentage force decay of elastomeric chain products from four different companies. Design In vitro, laboratory study. Setting LSUHSC Dental School, New Orleans, LA, USA. Methods Closed (non‐spaced), grey elastomeric chains from four companies were selected for the study. Three acrylic resin jigs were constructed to provide a framework for three simulated space closure mechanisms. The 6‐5‐3, the chain loop, and the 6‐3 were the configuration mechanisms used in the study. Outcome measures An electronic force gauge was used to measure the percentage force decay associated with each elastomeric chain over 28 days at preselected times. Results There was a significant difference in the mean percentage force decay for the three different mechanisms (P<0·001). For all four companies, the 6‐3 mechanical design had the smallest mean percentage force decay. There was a significant difference in the mean percentage force decay for the different companies (P<0·001). For all three mechanisms, Ormco had the smallest percentage force decay while Unitek had the highest percentage force decay. Conclusions The significant difference in the mean percentage force decay for the different mechanisms suggests that the 6‐3 design is a more efficient means of closing extraction spaces utilizing elastomeric chains.

Novel amelogenin-releasing hydrogel for remineralization of enamel artificial caries

Recently, the use of recombinant full-length amelogenin protein in combination with fluoride has shown promising results in the formation of densely packed enamel-like structures. In this study, amelogenin (rP172)-releasing hydrogels containing calcium, phosphate, and fluoride were investigated for remineralization efficacy using in vitro early enamel caries models. The hydrogels were applied to artificial caries lesions on extracted human third molars, and the remineralization efficacy was tested in different models: static gel remineralization in the presence of artificial saliva, pH cyclic treatment at pH 5.4 acetic buffer and pH 7.3 gel remineralization, and treatment with multispecies oral biofilms grown in a continuous flowing constant-depth film fermenter. The surface microhardness of remineralized enamel increased significantly when amelogenin was released from hydrogel. No cytotoxicity was observed when periodontal ligament cells were cultured with the mineralized hydrogels.

Applicability of the Pittsburgh Staging System for Advanced Cutaneous Malignancy of the Temporal Bone

The objectives are to evaluate the applicability of the Pittsburgh staging system (PSS) (designed for primary temporal bone malignancies) to advanced periauricular cutaneous malignancies with temporal bone involvement and to study treatment outcomes and prognostic factors predicting recurrence-free survival. Ten patients with advanced periauricular cutaneous malignancy with temporal bone involvement were identified. Patients with primary temporal bone or parotid gland malignancies were excluded. All patients were clinically T4 at presentation by the American Joint Committee on Cancer (AJCC) staging system. Using Pittsburgh staging, six were T1 (stage I) and four were T4 (stage III). The mean follow-up was 13.6 months (3 to 24 months). Patients with basal cell carcinoma were managed with wide local excision and lateral temporal bone resection (WLE/LTBR) without adjuvant therapy. Two of three (66%) are alive and free of disease; one patient died of other causes. Treatment for squamous cell carcinoma patients involved multimodality therapy. Kaplan-Meier survival curves show a worse prognosis in terms of disease-specific survival for patients with higher-staged PSS tumors. This did not reach statistical significance. The PSS may provide additional prognostic information on advanced cutaneous malignancies of the temporal bone over the more widely used AJCC staging system. However, further prospective multicenter studies with larger sample size are required to validate our findings. Basal cell carcinoma was well controlled with WLE/LTBR alone without adjuvant therapy, whereas squamous cell carcinoma required multimodality therapy: WLE/LTBR and postoperative radiation with or without chemotherapy.

Modeling the random effects covariance matrix for generalized linear mixed models

Generalized linear mixed models (GLMMs) are commonly used to analyze longitudinal categorical data. In these models, we typically assume that the random effects covariance matrix is constant across the subject and is restricted because of its high dimensionality and its positive definiteness. However, the covariance matrix may differ by measured covariates in many situations, and ignoring this heterogeneity can result in biased estimates of the fixed effects. In this paper, we propose a heterogenous random effects covariance matrix, which depends on covariates, obtained using the modified Cholesky decomposition. This decomposition results in parameters that can be easily modeled without concern that the resulting estimator will not be positive definite. The parameters have a sensible interpretation. We analyze metabolic syndrome data from a Korean Genomic Epidemiology Study using our proposed model.

PDZ-RhoGEF is essential for CXCR4-driven breast tumor cell motility through spatial regulation of RhoA

Summary The CXCL12–CXCR4 chemokine signaling pathway is a well-established driver of cancer progression. One key process promoted by CXCR4 stimulation is tumor cell motility; however, the specific signaling pathways leading to migration remain poorly understood. Previously, we have shown that CXCL12 stimulation of migration depends on temporal regulation of RhoA. However, the specific RhoGEF that translates CXCR4 signaling into RhoA activity and cell motility is unknown. We screened the three regulator of G-protein signaling RhoGEFs (LSC, LARG and PRG) and found that PRG selectively regulated the migration and invasion of CXCR4-overexpressing breast tumor cells. Interestingly, we found that PDZ-RhoGEF (PRG) was required for spatial organization of F-actin structures in the center, but not periphery of the cells. The effects on the cytoskeleton were mirrored by the spatial effects on RhoA activity that were dependent upon PRG. Loss of PRG also enhanced adherens junctions in the epithelial-like MCF7-CXCR4 cell line, and inhibited directional persistence and polarity in the more mesenchymal MDA-MB-231 cell line. Thus, PRG is essential for CXCR4-driven tumor cell migration through spatial regulation of RhoA and the subsequent organization of the cytoskeletal structures that support motility. Furthermore, immunohistochemical analysis of human breast tumor tissues shows a significant increase of PRG expression in the invasive areas of the tumors, suggesting that this RhoGEF is associated with breast tumor invasion in vivo.

Evaluation of 3 commercially available materials for resolution of white spot lesions.

INTRODUCTION White spot lesions are often seen on the teeth after orthodontic treatment, resulting in unpleasant esthetics. The aim of this in-vitro study was to compare subjectively and objectively the esthetic outcomes of white spot lesions treated with 3 commercially available products that have been reported to have a positive effect on the remineralization of enamel. METHODS Forty extracted premolars were randomly allocated into 1 of 4 groups (n = 10). The teeth were exposed to a demineralization solution at 37°C for 14 days to produce white spot lesions that were about 100 μm deep. Each group was then randomly assigned to receive either control treatment with artificial saliva or treatment with 1 of the 3 commercially available products: Restore toothpaste (Dr. Collins Inc, Orange County, Calif), which contains NovaMin (Dr. Collins Inc); Prevident 5000 (Colgate, New York, NY); and MI Paste Plus (GC America, Alsip, Ill). All groups were evaluated 5 times at 6 time points during the study. RESULTS The subjective and objective results were mixed within groups and between groups for the products tested. CONCLUSIONS We found no conclusive evidence that any of these 3 materials produced more favorable esthetic white spot lesion remineralization results.