Nawaf Labban

A novel three‐dimensional scaffold for regenerative endodontics: materials and biological characterizations

An electrospun nanocomposite fibrous material holds promise as a scaffold, as well as a drug‐delivery device to aid in root maturogenesis and the regeneration of the pulp–dentine complex. A novel three‐dimensional (3D) nanocomposite scaffold composed of polydioxanone (PDS II®) and halloysite nanotubes (HNTs) was designed and fabricated by electrospinning. Morphology, structure, mechanical properties and cell compatibility studies were carried out to evaluate the effects of HNTs incorporation (0.5–10u2009wt% relative to PDS w/w). Overall, a 3D porous network was seen in the different fabricated electrospun scaffolds, regardless of the HNT content. The incorporation of HNTs at 10u2009wt% led to a significant (pu2009<u20090.0001) fibre diameter increase and a reduction in scaffold strength. Moreover, PDS–HNTs scaffolds supported the attachment and proliferation of human‐derived pulp fibroblast cells. Quantitative proliferation assay performed with human dental pulp‐derived cells as a function of nanotubes concentration indicated that the HNTs exhibit a high level of biocompatibility, rendering them good candidates for the potential encapsulation of distinct bioactive molecules. Collectively, the reported data support the conclusion that PDS–HNTs nanocomposite fibrous structures hold potential in the development of a bioactive scaffold for regenerative endodontics. Copyright

The direct cytotoxic effects of medicaments used in endodontic regeneration on human dental pulp cells

AIMnThe purpose of this in vitro study was to evaluate the effects of intracanal medicaments commonly used in endodontic regeneration on the survival of human dental pulp cells (DPCs).nnnMETHODSnDPCs were cultured and exposed to either no medicament treatment or low concentrations (0.3-5 mg ml(-1) ) of calcium hydroxide [Ca(OH)2 ], triple antibiotic paste (TAP), or double antibiotic paste (DAP) for 3 days. After that, toxicity to the DPCs was determined by lactate dehydrogenase activity assays (LDH) and cell proliferation was measured by colorimetric assays (WST-1). Two-way anova followed by Fishers protected least significant differences was used for statistical analyses (α = 0.05).nnnRESULTSnThe group-by-concentration interactions were significant for the LDH and WST-1 assays (P < 0.0001). For the LDH assays, only the highest tested concentration (5 mg ml(-1) ) of Ca(OH)2 and TAP caused significant toxicity to the DPCs compared with the untreated control, while four tested concentrations of DAP (0.5, 1, 2.5, and 5 mg ml(-1) ) caused significant toxicity to the DPCs compared with the untreated control. For the WST-1 assays, the highest concentrations that did not negatively affect the proliferation rate of DAP, TAP and Ca(OH)2 were 0.3, 2, and 2.5 mg ml(-1) , respectively.nnnCONCLUSIONnThe low concentrations of intracanal medicaments tested in this study were not cytotoxic in cultured cells. However, these concentrations are much lower than the concentrations that have been advocated in endodontic regeneration. Furthermore, the negative effects of TAP on DPCs were detected at lower concentrations by using the WST-1 assays than by measuring the LDH release.

Effects of cigarette smoke condensate on oral squamous cell carcinoma cells

OBJECTIVEnEpidemiological studies have reported that tobacco use is a major etiological factor for oral cancer. Several matrix metalloproteinases (MMPs) have been shown to play important roles in the invasion and metastasis of oral squamous cell carcinomas, especially MMP-2 and MMP-9. This study examined the effects of cigarette smoke condensate (CSC) on oral cancer cells.nnnDESIGNnTwo oral squamous cell carcinoma cell lines, SCC-25 (metastatic) and CAL-27 (non-metastatic), were exposed to different concentrations of CSC and examined for their collagen degrading ability and MMP production using collagen degradation assays, zymograms and Western blots.nnnRESULTSnExposure to CSC increased the collagen degrading ability of the metastasizing cell line (SCC-25) by a mechanism involving increased MMP-2 and MMP-9 production.nnnCONCLUSIONnCSC increased the collagen degrading ability of SCC-25 by increasing the MMP-2 and MMP-9 protein levels. Continued cigarette smoking in oral cancer patients may result in decreased survival rates due to enhanced metastatic potential of the cancer cells.

Effects of provisional acrylic resins on gingival fibroblast cytokine/growth factor expression

STATEMENT OF PROBLEMnSeveral studies have reported that polymerized resin materials may release agents into surrounding tissues. These agents could alter cytokine/growth factor expression.nnnPURPOSEnThe purpose of this study was to determine the effects that provisional acrylic resins have on cell toxicity and the expression of cytokines/growth factors from human gingival fibroblasts (HGFs).nnnMATERIAL AND METHODSnThe materials used in this study were chemically activated bis-acryl composite (Chem-Bis), chemically activated polyethyl methacrylate (Chem-PEMA), chemically activated polymethyl methacrylate (Chem-PMMA), and heat-activated polymethyl methacrylate (Heat-PMMA) resins. HGFs were incubated for 72 hours in the presence of eluate from each resin and in the absence of any eluate (negative control). The conditioned media were then collected and stored at -70 degrees C. Cell toxicity was determined using a lactate dehydrogenase method. Cytokine/growth factor expression was examined using cytokine antibody arrays. The experiments were repeated 3 times. The data were analyzed with 1-way ANOVA, Mann-Whitney test, and 1-sample t test (alpha=.05).nnnRESULTSnThere was no significant cell toxicity observed from the eluates. The cytokine/growth factor expression induced by Chem-Bis was significantly greater than the control for growth-regulated oncogene (GRO) (P<.001), monocyte chemoattractant protein-1 (MCP-1) (P=.031), and tumor necrosis factor-beta (TNF)-beta (P=.009). For Chem-PEMA, the cytokine/growth factor expression was significantly greater than the control for GRO-alpha (P=.022), interleukin (IL)-13 (P=.031), and TNF-alpha (P=.017). The cytokines/growth factors induced by Chem-PEMA were significantly less than the control (P=.008) and Chem-Bis for IL-8 (P=.042). The expression induced by Chem-PMMA was significantly greater than the control for IL-13 (P=.036), IL-1 alpha (P=.003), IL-2 (P=.020), and IL-5 (P=.045). Finally, Heat-PMMA induced significantly greater levels than the control for GRO (P<.001) and IL-13 (P=.008).nnnCONCLUSIONSnThis study demonstrated that the resins evaluated were nontoxic to the HGFs. There were changes in the cytokine/growth factor levels that were statistically significant, but may not be clinically significant.

Triethylene Glycol Dimethacrylate Induction of Apoptotic Proteins in Pulp Fibroblasts

OBJECTIVEnMonomers such as triethylene glycol dimethacrylate (TEGDMA) can leach from dental composites. TEGDMA-induced apoptosis in human pulp has been reported. However, the apoptotic (pro or anti) proteins involved in this process remain unclear. Therefore, the purpose of this study was to determine which apoptotic proteins are enhanced or suppressed during TEGDMA-induced apoptosis.nnnMATERIALS AND METHODSnHuman pulp fibroblasts (HPFs) were incubated with different TEGDMA concentrations (0.125-1.0 mM) and cytotoxicity was determined. TEGDMA was shown to be cell cytotoxic at concentrations of 0.50 mM and higher. The highest concentration with no significant cytotoxicity was then incubated (0.25 mM TEGDMA) with the HPFs. Cell lysates were then prepared and the protein concentrations determined. Human Apoptosis Array kits were utilized to detect the relative levels of 43 apoptotic proteins.nnnRESULTSnHPFs exposed to TEGDMA showed significant increases in multiple pro-apoptotic proteins such as Bid, Bim, Caspase 3, Caspase 8, and Cytochrome c at 24 hours. Some anti-apoptotic proteins were also altered.nnnCONCLUSIONSnThe results indicated that TEGDMA activates both the extrinsic and intrinsic apoptotic pathways.

Effects of resolvin D1 on cell survival and cytokine expression of human gingival fibroblasts.

BACKGROUNDnTissue breakdown in periodontitis is initiated by bacteria, such as Porphyromonas gingivalis, and is caused largely by host responses. Resolvins protect the host against acute inflammation by blocking the migration of polymorphonuclear neutrophils to initiate resolution. The effects of resolvins on human gingival fibroblasts (HGFs) are unknown. This study examines the effects of resolvin D1 on HGF survival and cytokine expression when treated with or without P. gingivalis supernatant.nnnMETHODSnCytotoxicity of resolvin D1 on HGFs with or without a toxic level of P. gingivalis supernatant was measured with lactate dehydrogenase assays. Cytokine arrays were performed on HGF-conditioned media treated with or without resolvin D1 and with or without P. gingivalis supernatant.nnnRESULTSnResolvin D1 had no cytotoxic effects on HGFs at concentrations between 1 and 1,000 nM (all P > 0.05). Resolvin D1 (1,000 nM) significantly inhibited the toxic effects of 13.5% (v/v) P. gingivalis supernatant on HGFs (P = 0.002). Resolvin D1 significantly reduced the expression of interleukin (IL)-6 (P = 0.010) and monocyte chemoattractant protein (MCP)-1 (P = 0.04) in untreated fibroblasts. P. gingivalis (10%) supernatant significantly increased the expression levels of granulocyte-macrophage colony-stimulating factor (CSF), granulocyte CSF, growth-regulated oncogene (GRO), IL-5, IL-6, IL-7, IL-8, IL-10, MCP-1, MCP-2, MCP-3, and monokine induced by γ-interferon. Resolvin D1 significantly reduced the expression of GRO (P = 0.04), marginally reduced the levels of MCP-1 (P = 0.10), and marginally increased the levels of transforming growth factor (TGF)-β1 (P = 0.07) from HGFs treated with P. gingivalis supernatant.nnnCONCLUSIONSnResolvin D1 altered the cytotoxicity of P. gingivalis supernatant on HGFs. Resolvin D1 significantly reduced GRO, marginally reduced MCP-1, and marginally increased TGF-β1 from P. gingivalis-treated HGFs, which could alter the ability of P. gingivalis to induce inflammation.

Effects of interim acrylic resins on the expression of cytokines from epithelial cells and on collagen degradation

STATEMENT OF PROBLEMnInterim acrylic resins release agents that alter cytokine expression in the surrounding tissues, which could alter extracellular matrix degradation.nnnPURPOSEnThe purpose of the study was to evaluate the responses of human epidermal keratinocytes to eluates of interim acrylic resins in regards to cytokine expression and cell-mediated collagen degradation.nnnMATERIAL AND METHODSnSpecimens of 4 different interim acrylic resins (HI-I, Jet Acrylic, SNAP acrylic, and Protemp Plus) were placed in Epilife medium for 48 hours and the eluates collected. The cells were incubated for 72 hours in nontoxic concentrations of the eluates. Cytotoxicity was evaluated with lactate dehydrogenase assays and cytokine expression with cytokine antibody arrays. Collagen degradation was determined with a collagen type I assay. The experiments were performed 3 times. Data were analyzed with 1-way and mixed-model ANOVA (α=.05).nnnRESULTSnNone of the eluates were cytotoxic. Cytokine expression from the heat-activated polymethyl methacrylate resin group was significantly less for interleukin-3, but significantly greater for interlukin-7. Expression for the chemically activated polymethyl methacrylate resin group was significantly less for growth-regulated oncogene-α, interleukin-1α, and interleukin-3. Expression for the chemically activated polyethyl methacrylate resin group was significantly less for interleukin-1α and interleukin-3, but significantly greater for interleukin-13 and monocytes chemoattractant protein-3. The cytokine expression induced by chemically activated bis-acryl composite resin was significantly greater for granulocyte-macrophage colony stimulating factor, interleukin-7, and monocytes chemoattractant protein-3, but significantly less for growth-regulated oncogene-α. Collagen degradation was not significantly different in any of the groups.nnnCONCLUSIONSnThe eluates used were not cytotoxic and did not induce cell-mediated collagen degradation. Some significant changes in cytokine expression were noted.

Responses of Human Neutrophils to Nicotine and/or Porphyromonas gingivalis

BACKGROUNDnTobacco smoking is considered a major modifiable risk factor for periodontal disease. Nicotine is the addictive ingredient in tobacco and has been shown to affect multiple cellular processes. Neutrophils are the first line of host defense and are critical cells in the maintenance of periodontal health through their role in the control of bacteria, but they can also contribute to the progression of periodontal disease by the production and release of reactive oxygen species (ROS). Virulence factors from periodontal pathogens, such as Porphyromonas gingivalis (Pg), stimulate the respiratory burst of neutrophils. The objective of this study is to explore the oxidative activity of neutrophils when stimulated with Pg, nicotine, or both.nnnMETHODSnNeutrophils were separated from buffy coats by the double dextran gradient method. The generation of ROS by neutrophils was determined using luminol-dependent chemiluminescence assays. The reaction was followed for 90 minutes, and the neutrophil activation was recorded as the total integrated energy output.nnnRESULTSnThe Pg and Pg plus nicotine groups had a significantly higher active and peak chemiluminescence than the nicotine group (all with P <0.0001). The Pg and Pg with nicotine groups were not significantly different (P = 0.90).nnnCONCLUSIONnIn the presence of Pg, the nicotine did not further enhance the ROS release by the neutrophils, suggesting that the bacteria induced the maximum ROS release in this model system.

A simple technique to reduce the risk of irreversible gingival recession after the final impression.

The chemicomechanical method is the most common tissue displacement technique used to facilitate the final impression for fixed dental prostheses. The article describes a simple technique to minimize the risk of developing gingival irreversible recession because of tissue displacement cords.

The influence of delayed light curing on the degree of conversion and polymerization contraction stress in dual-cured resin luting agents

Abstract The aim of the study was to assess the effect of delayed photo-initiation on the polymerization contraction stress (PCS) and degree of conversion (DC) of a dual-cure resin-luting agent. Thirty-five disk (6 mm × 1 mm) samples (n = 10 each group) of dual cure resin luting agent for PCS assessment were fabricated and polymerized using two illuminated quartz rods. Based on the delay in photo-initiation, 30 disks were divided among six groups [group A-0 min (min) delay, group B-2 min, group C-4 min, group D-6 min, group E-8 min and group F-10 min]. A non-photoinitiated group (group G – chemical cure – n = 5) was included as control. The PCS for all specimens was assessed using a Tensometer. For DC evaluation thirty-five specimens were divided into seven groups with delays in photo-initiation (group H-0 min, group I-2 min, group J-4 min, group K-6 min, group L-8 min and group M-10 min, group N-chemical cure). DC was assessed using attenuated total reflectance spectroscopic technique. Statistical comparison among groups was performed using analysis of variance (α = 0.05). The maximum and minimum PCS and DC values with delayed photo-initiation was observed in group-C (3.34 MPa) & group-F (2.44 MPa); and group-M (0.78 MPa) and group-H (0.55 MPa) respectively. Chemically cured samples showed the least PCS (group-G, 1.94) and DC (group-N, 0.53) values in their respective categories. PCS significantly decreased with delayed photo-initiation. A significant increase in DC was noticed when photo-initiation was delayed in the dual cure resin luting agent.