Upper Airway Flow Dynamics in Obstructive Sleep Apnea Patients with Various Apnea-Hypopnea Index.

BACKGROUND AND AIM: This study evaluates the upper airway flow characteristics, anatomical features and analyzes their correlations with AHI in patients with varied degrees of OSA severity seeking for discernments of the underlying pathophysiological profile. MATERIALS AND METHODS: Patient-specific computational fluid dynamics models were reconstructed from high-resolution cone-beam computed tomography images for 4 OSA patients classified as minimal, mild, moderate, and severe according to AHI. RESULTS: The parameters, minimal cross-sectional area (MCA), and the pharyngeal airway volume did not show clear correlations with the OSA severity defined according to AHI. No correlations were found between the classically defined resistance of the airway in terms of pressure drop and AHI. The flow analysis further showed that the fluid mechanisms likely to cause airway collapse are associated with the degree of narrowing in the pharyngeal airway rather than AHI. Results also suggested that some patients classified as severe OSA according to the AHI can show less susceptibility to airway collapse than patients with relatively lower AHI values and vice versa. CONCLUSIONS: The relative contribution of anatomical and non-anatomical causes to the OSA severity can significantly vary between patients. AHI alone is inadequate to be used as a marker of the pathophysiological profile of OSA. Combining airflow analysis with AHI in diagnosing OSA severity may provide additional details about the underlying pathophysiology, subsequently improving the individualized clinical outcomes.

Ethnic variation of oral microbiota in children.

Despite widely used preventive measures such as sealant programs to control caries prevalence, disparities are seen among ethnic groups. Supragingival plaque harbors hundreds of bacterial species, playing a significant role in oral health and disease. It is unknown whether the ethnic variation influences the supragingival microbiota in children. In our study, variations in microbiota of the supragingival plaque was investigated from 96 children between 6 and 11 years old in four ethnic groups (African American, Burmese, Caucasian, and Hispanic) from the same geographic location by 16S rRNA gene sequencing. We found that the microbial alpha and beta diversity of supragingival microbiota significantly differed between ethnic groups. The supragingival plaque microbiota had the most complex microbial community in Burmese children. Within-group microbiota similarity in Burmese or Caucasian children was significantly higher than between-groups similarity. We identified seven ethnic group-specific bacterial taxa after adjusting for dental plaque index, decayed missing filled teeth (DMFT) and the frequency of brushing. Children with high plaque index and high DMFT values were more similar to each other in the overall microbial community, compared to low plaque index or low DMFT groups in which inter-subject variation is high. Several bacterial taxa associated with high plaque index or high DMFT were ethnic group-specific. These results demonstrated that supragingival microbiota differed among ethnicity groups in children.

Symmetric multiquadrant isolated dentin dysplasia (SMIDD), a unique presentation mimicking dentin dysplasia type 1b.

Dentin dysplasia (DD) is a rare developmental dentin disorder that causes root malformation. It is divided into radicular DD type 1 (DD-1) and coronal DD type 2 (DD-2). Recently, a new entity causing localized root malformation of permanent first molars that resembles DD-1b has been described as molar-incisor malformation (MIM). We report and compare 4 new cases that exhibit similar clinical, histologic, and radiographic features to the new entity, MIM. We believe MIM and our 4 cases to be the same entity, which is nonhereditary and, because of the isolated but bilaterally symmetric pattern of involvement, may be caused by a short-duration environmental insult that disrupts normal development/function of Hertwig's epithelial root sheath. We propose the name symmetrical multiquadrant isolated dentin dysplasia as the most appropriate descriptive designation for this unusual but highly distinctive anomaly.

Massive Open Online Courses in Dental Education: Two Viewpoints: Viewpoint 1: Massive Open Online Courses Offer Transformative Technology for Dental Education and Viewpoint 2: Massive Open Online Courses Are Not Ready for Primetime.

This point/counterpoint article discusses the strengths and weaknesses of incorporating Massive Open Online Courses (MOOCs) into dental education, focusing on whether this relatively new educational modality could impact traditional dental curricula. Viewpoint 1 asserts that MOOCs can be useful in dental education because they offer an opportunity for students to learn through content and assessment that is delivered online. While specific research on MOOCs is limited, some evidence shows that online courses may produce similar learning outcomes to those in face-to-face courses. Given that MOOCs are intended to be open source, there could be opportunities for dental schools with faculty shortages and financial constraints to incorporate these courses into their curricula. In addition to saving money, dental schools could use MOOCs as revenue sources in areas such as continuing education. Viewpoint 2 argues that the hype over MOOCs is subsiding due in part to weaker than expected evidence about their value. Because direct contact between students, instructors, and patients is essential to the dental curriculum, MOOCs have yet to demonstrate their usefulness in replacing more than a subset of didactic courses. Additionally, learning professionalism, a key component of health professions education, is best supported by mentorship that provides significant interpersonal interaction. In spite of the potential of early MOOC ideology, MOOCs in their current form require either further development or altered expectations to significantly impact dental education.

An in-vitro evaluation of mechanical and esthetic properties of orthodontic sealants.

OBJECTIVE: To evaluate mechanical and esthetic Properties of two commercially available orthodontic sealants: Opal(®)Seal (OS) and L.E.D. Pro Seal (PS). MATERIALS AND METHODS: Discs of each sealant were prepared to test the following properties: Micro hardness, wear resistance and color stability. Samples were randomly selected after the wear test for SEM imaging to analyze surface morphology. RESULTS: OS was significantly harder than PS (P < 0.001). PS was significantly more wear resistant than OS (P < 0.05). PS showed a greater ∆E*ab (increased staining) when placed in wine or coffee showing a significant difference (P < 0.05). SEM showed particle size, shape and distribution were different for PS and OS reflecting the pattern seen on wear surfaces. CONCLUSION: Both orthodontic sealants are beneficial for protecting enamel. However with better wear properties PS was superior in resisting mechanical stresses. OS was more color stable.

Oral epithelial cell reaction after exposure to Invisalign plastic material.

INTRODUCTION: Invisalign plastic aligners (Align Technology, Santa Clara, Calif) are used to correct malocclusions. The aligners wrap around the teeth and are in contact with gingival epithelium during treatment. The purpose of this study was to evaluate the cellular responses of oral epithelium exposed to Invisalign plastic in vitro. METHODS: Oral epithelial cells were exposed to eluate obtained by soaking Invisalign plastic in either saline solution or artificial saliva for 2, 4, and 8 weeks. Cells grown in media containing saline solution or saliva served as controls. Morphologic changes were assessed by light microscopy. The 3-[4, 5-dimethythiazol- 2-yl]-2, 5-diphenyl tetrazolium bromide assay and flow cytometry were used to determine cell viability and membrane integrity, respectively. Cellular adhesion and micromotion of epithelial cells were measured in real time by electrical cell-substrate impedance sensing. RESULTS: Cells exposed to saline-solution eluate appeared rounded, were lifted from the culture plates, and demonstrated significantly increased metabolic inactivity or cell death (P <0.05). Saliva eluates did not induce significant changes in cell viability compared with untreated cells. Flow cytometry and electric cell-substrate impedance sensing showed that cells treated with saline-solution eluate exhibited compromised membrane integrity, and reduced cell-to-cell contact and mobility when compared with saliva-eluate treatment. CONCLUSIONS: Exposure to Invisalign plastic caused changes in viability, membrane permeability, and adhesion of epithelial cells in a saline-solution environment. Microleakage and hapten formation secondary to compromised epithelial integrity might lead to isocyanate allergy, which could be systemic or localized to gingiva. However, these results suggest that saliva might offer protection.

Focal adhesion kinase mediates ß-catenin signaling in periodontal ligament cells.

Periodontal ligament (PDL) cells convert the orthodontic forces into biological responses by secreting signaling molecules to induce modeling of alveolar bone and tooth movement. Beta-catenin pathway is activated in response to mechanical loading in PDL cells. The upstream signaling pathways activated by mechanical loading resulting in the activation of ß-catenin pathway through Wnt-independent mechanism remains to be characterized. We hypothesized that mechanical loading induces activation of ß-catenin signaling by mechanisms that dependent on focal adhesion kinase (FAK) and nitric oxide (NO). We found that mechanical or pharmacological activation of ß-catenin signaling in PDL cells upregulated the expression of ß-catenin target genes. Pre-treatment of PDL cells with FAK inhibitor-14 prior to mechanical loading abolished the mechanical loading-induced phosphorylation of Akt and dephosphorylation of ß-catenin. PDL cells pre-treated with NO donor or NO inhibitor and subjected to mechanical loading. Western blot analysis showed that the mechanical loading or pre-treatment with NO donor increased the levels of dephosphorylated ß-catenin, pAkt, and pGSK-3ß. Pre-treatment with NO inhibitor blocked the mechanical loading-induced phosphorylation of Akt and dephosphorylation of ß-catenin. These data indicate that mechanical loading-induced ß-catenin stabilization in PDL cells involves phosphorylation of Akt by two parallel pathways requiring FAK and NO.

Delivery of Transforming Growth Factor-ß3 Plasmid in a Collagen Gel Inhibits Cranial Suture Fusion in Rats.

Objective : Studies described in this paper were designed to test the hypothesis that an increase in nonviral, plasmid-encoded Tgf-ß3 production, localized to the rat posterior frontal suture, prevents programmed suture fusion. Design : We developed a gene delivery system based on a dense collagen gel to deliver nonviral plasmids that encode for Tgf-ß3. Studies were performed to test the ability of this system to rescue rat cranial suture fusion in vitro and in vivo. Immunohistochemical studies were conducted to characterize the possible mechanisms by which increased production and presence of Tgf-ß3 protein interferes with suture fusion. Results : Posterior frontal sutures in the Tgf-ß3 plasmid-treated group exhibited 77% to 85% less bony bridging than the collagen control and untreated groups after 15 days in culture. In animals treated with Tgf-ß3 plasmid or Tgf-ß3 protein, there was a significant reduction in suture fusion in the middle region of the posterior frontal sutures when compared with control groups. In this region the Tgf-ß3 plasmid-treated group revealed 70% to 75% less bony bridging than control groups in vivo. Conclusions : Collagen gel can be formulated to provide release of nonviral plasmid DNA that results in cell transfection and elevated Tgf-ß3 protein production. Tgf-ß3 is an important regulator of suture fusion, and an increase in plasmid-encoded Tgf-ß3 protein is effective in inhibiting programmed suture fusion in rats.

Mechanical loading activates ß-catenin signaling in periodontal ligament cells.

OBJECTIVE: To determine whether ß-catenin signaling is responsive to mechanical loading in periodontal ligament (PDL) cells. MATERIALS AND METHODS: To determine whether Wnt/ß-catenin signaling pathway components are present and functional, PDL cells were treated with lithium chloride or Wnt3a-conditioned media. To determine whether mechanical strain activates ß-catenin signaling, PDL cells were subjected to compressive loading. Activation of the ß-catenin signaling pathway was determined by immunofluorescence, Western immunoblotting, and TOPflash assay. RESULTS: Mimicking Wnt signaling stimulates ß-catenin nuclear translocation and T-cell factor/lymphoid enhancer binding factor-dependent transcriptional activation in PDL cells. Mechanical loading stimulates a transient accumulation of dephosphorylated ß-catenin in the cytoplasm and its translocation to the nucleus. This effect of strain acts through activation of protein kinase B and phosphorylation of glycogen synthase kinase-3 beta. These strain-related changes do not involve the low-density lipoprotein receptor-related protein 5/Wnt receptor. CONCLUSIONS: The Wnt/ß-catenin signaling pathway components are functional and activated by mechanical loading in PDL cells. ß-catenin serves as an effector of mechanical signals in PDL cells.

Sustained delivery of bioactive cytokine using a dense collagen gel vehicle collagen gel delivery of bioactive cytokine.

OBJECTIVE: The use of cytokines as localized therapeutic agents is limited by the lack of a satisfactory delivery system. The aim of the current investigation was to determine the release kinetics and bioactivity of a simplified cytokine/collagen gel system designed to achieve extended, local delivery of bioactive cytokines at sites of premature cranial suture fusion (craniosynostosis). DESIGN: Cytokine release was determined by ELISA measurements of Tgf-beta3 collected in media. Cytokine bioactivity was determined by measuring the effect of conditioned media, containing released Tgf-beta3, on mink lung epithelial cell proliferation and osteoblast alkaline phosphatase activity. Osteoblast response was evaluated by measuring proliferation of cells cultured on collagen gel containing Tgf-beta3 using an AlamarBlue assay. RESULTS: Gels loaded with 100 and 500 ng of Tgf-beta3 produced a sustained release over 14 days with a pattern of initial large release followed by a gradual reduction in the amount released over the time. The reduced release over time was correlated to the amount initially loaded. Mink lung epithelial cell assay results indicated that Tgf-beta3 released from the collagen gel retained its bioactivity following incorporation into the collagen gel and release into the media. This bioactivity was further illustrated by a decreased alkaline phosphatase activity measured in osteoblasts cultured on the gels loaded with Tgf-beta3. Osteoblast proliferation assays demonstrated that the collagen gel has an inherent inhibitory effect on osteoblast cell number. CONCLUSIONS: This collagen gel/cytokine delivery system can retain and release bioactive cytokine over a prolonged period. These results will allow for better optimization of future in vitro and in vivo studies directed at improving the treatment of craniosynostosis.