Tumor Necrosis Factor‐α Inhibits Transforming Growth Factor‐β–Stimulated Myofibroblastic Differentiation and Extracellular Matrix Production in Human Gingival Fibroblasts

Background: Fibroblasts play a critical role during wound healing and chronic inflammation through the synthesis and assembly of extracellular matrix (ECM) molecules. These responses may be modulated by soluble cytokines and growth factors present in tissues. In the present study, we evaluate whether transforming growth factor‐β1 (TGF‐β1) and tumor necrosis factor‐α (TNF‐α) modulate myofibroblastic differentiation and the production of ECM components. Methods: Primary cultures of human gingival fibroblasts (HGFs) were stimulated with recombinant TGF‐β1 and TNF‐α. Protein levels of α‐smooth muscle actin (α‐SMA), type I collagen, heat shock protein‐47 (HSP‐47), fibronectin (FN), ED‐A‐FN, and periostin and activation of the Smad pathway were evaluated through Western blot analysis. α‐SMA and actin fibers were identified by immunofluorescence. TGF‐β1, TNF‐α, and α‐SMA were identified by immunohistochemistry in biopsies of inflamed human gingival tissues. TGF‐β1 activity was evaluated using a plasminogen activator inhibitor‐1 (PAI‐1) reporter transfected in HGFs. Results: TGF‐β1 stimulated the differentiation of myofibroblasts as evidenced by strong expression of α‐SMA and ED‐A‐FN. Moreover, TGF‐β1 induced the production of type I collagen, HSP‐47, FN, and periostin. Costimulation with TNF‐α and TGF‐β1 significantly reduced the expression of all the above‐mentioned proteins. TNF‐α also inhibited the activation of the Smad2/3 pathway and the activity of the PAI‐1 reporter. Conclusions: TNF‐α inhibits several cell responses induced by TGF‐β1, including the differentiation of myofibroblasts, the activation of the Smad signaling pathway, and the production of key molecules involved in tissue repair, such as type I collagen, FN, and periostin. The interaction between cytokines may explain the delayed tissue repair observed in chronic inflammation of gingival tissues.     

Significance of elevated gingival crevicular fluid tumor necrosis factor‐α and interleukin‐8 levels in chronic hemodialysis patients with periodontal disease

Da? A, F?rat ET, Kadiro?lu AK, Kale E, Y?lmaz ME. Significance of elevated gingival crevicular fluid tumor necrosis factor‐α and interleukin‐8 levels in chronic hemodialysis patients with periodontal disease. J Periodont Res 2010; 45: 445–450. © 2010 John Wiley & Sons A/S Background and Objective: The prevalence of chronic renal disease in industrialized countries is increasing, and chronic renal disease and periodontitis can have significant, reciprocal effects. The aim of this study was to evaluate the associations between specific clinical parameters and the levels of tumor necrosis factor‐α (TNF‐α) and interleukin‐8 (IL‐8) in the gingival crevicular fluid of hemodialysis (HD) patients with periodontal disease. Material and Methods: Forty‐three HD patients and 43 systemically healthy subjects were enrolled in this study. Plaque index (PI), gingival index (GI) and pocket depth were used to determine periodontal status. Venous blood samples were obtained from each patient in the morning before the dialysis session and analyzed to determine the levels of inflammatory, biochemical and hematological parameters. Gingival crevicular fluid was collected from all subjects, and the levels of TNF‐α and IL‐8 were determined in the gingival crevicular fluid samples. Results: The following results were obtained from HD patients and controls: TNF‐α (pg/mL), 31.40 ± 1.46 and 3.06 ± 0.15 (p < 0.001); IL‐8 (pg/mL), 90.98 ± 94.03 and 35.05 ± 16.86 (p < 0.001); PI, 1.69 ± 1.02 and 0.04 ± 0.02 (p < 0.001); GI, 0.82 ± 0.06 and 0.04 ± 0.02 (p < 0.001); and pocket depth, 2.23 ± 0.63 and 1.51 ± 0.05 (p < 0.001), respectively. In addition, there were positive correlations between TNF‐α and PI (r = 0.642, p < 0.001), between TNF‐α and GI (r = 0.565, p < 0.001), between TNF‐α and pocket depth (r = 0.522, p < 0.001), between IL‐8 and PI (r = 0.402, p = 0.002), between IL‐8 and GI (r = 0.396, p = 0.002), and between IL‐8 and pocket depth (r = 0.326, p = 0.012). There were negative correlations between albumin and PI (r = ?0.491, p < 0.001), albumin and GI (r = ?0.406, p < 0.001), albumin and pocket depth (r = ?0.464, p < 0.001) and albumin and CRP (r = ?0.467, p = 0.002) and between the gingival crevicular fluid levels of TNF‐α and IL‐8, TNF‐α and hemoglobin (r = ?0.745, p < 0.001; r = ?0.285, p < 0.05) (respectively). Conclusion: The levels of TNF‐α and IL‐8 in gingival crevicular fluid were significantly higher in HD patients than in controls. There were strong, positive correlations between clinical periodontal parameters and the levels of inflammatory cytokines in gingival crevicular fluid from the HD patients.     

Tumor Necrosis Factor‐α and Interleukin (IL)‐1β, IL‐6, and IL‐8 Impair In Vitro Migration and Induce Apoptosis of Gingival Fibroblasts and Epithelial Cells,Delaying Wound Healing

Background: Multiple factors affect oral mucosal healing, such as the persistence of an inflammatory reaction. The present study evaluates effects of tumor necrosis factor (TNF)‐α and interleukin (IL)‐1β, IL‐6, and IL‐8 on epithelial cells (ECs) and human gingival fibroblasts (GFs) in vitro. Methods: GFs and ECs were seeded in 96‐well plates (1 × 10⁴ cells/well) in plain culture medium (Dulbecco’s modified Eagle’s medium [DMEM]) containing 1% antibiotic/antimycotic solution and 10% fetal bovine serum, and incubated for 24 hours. Both cell lines were exposed for 24 hours to the following cytokines: 1) TNF‐α (100 ng/mL); 2) IL‐1β (1 ng/mL); 3) IL‐6 (10 ng/mL); and 4) IL‐8 (10 ng/mL). All cytokines were diluted in serum‐free DMEM. Control cultures were exposed only to serum‐free DMEM. Effects of exposure to inflammatory cytokines were determined by means of: 1) apoptosis (anexin V); 2) cell migration (wound healing assay); 3) inflammatory cytokine synthesis (enzyme‐linked immunosorbent assay). Data were analyzed by Kruskal–Wallis and Mann–Whitney U tests (α = 0.05). Results: Increased apoptosis rates were noted when cells were exposed to inflammatory cytokines, except ECs exposed to IL‐1β. Cell migration was negatively affected by all inflammatory cytokines for both cell lines. ECs and GFs exposed to IL‐6 and IL‐8 significantly increased synthesis of TNF‐α and IL‐1β. Conclusions: Demonstrated results indicate negative effects of tested inflammatory cytokines on ECs and GFs, inducing apoptosis and impairing cell migration. These results can justify delayed oral mucosa healing in the presence of inflammatory reaction.     

High‐power,red‐light‐emitting diode irradiation enhances proliferation,osteogenic differentiation,and mineralization of human periodontal ligament stem cells via ERK signaling pathway

1 Background

Light‐emitting diode (LED) is attracting attention as a new light source for phototherapy. However, its effects on periodontal tissue regeneration remain unknown. The aim of this study was to examine the effects of high‐power, red LED irradiation on human periodontal ligament stem cells (PDLSCs), which play an important role in periodontal tissue regeneration.

2 Methods

PDLSCs were derived from adult human third molars. The light source was red LED (peak wavelength: 650 nm). Energy densities ranging from 0 to 10 J/cm² were tested to determine the optimal dose. PDLSC proliferation was measured using two parameters: live cell protease and ATP levels. After the cells were induced to differentiate, the effect of LED irradiation on osteogenic differentiation and mineralization was examined, with particular focus on the extracellular signal‐regulated kinase (ERK)1/2 signaling pathway using an ERK inhibitor (PD98059).

3 Results

LED irradiation at 8 J/cm² led to a significant increase in PDLSC proliferation and enhanced Runx2 and Osterix mRNA expression, Alkaline phosphatase activity, procollagen type I C‐peptide and osteocalcin production, calcium deposition, and alizarin red S staining. In addition, LED induced the activation of ERK1/2, and the effects of LED on PDLSC proliferation, differentiation, and mineralization could be suppressed by treatment with PD98059.

4 Conclusions

The results of this study show that 650‐nm high‐power, red, LED irradiation increases PDLSCs proliferation, and osteogenic differentiation and mineralization, mediated by ERK1/2 activation. These findings suggest that LED may be a useful tool for periodontal tissue regeneration.     

Clinical Comparison of Platelet‐Rich Fibrin and a Gelatin Sponge in the Management of Palatal Wounds After Epithelialized Free Gingival Graft Harvest: A Randomized Clinical Trial

Background: Platelet‐rich fibrin (PRF) promotes tissue regeneration by releasing various growth factors. The palatal donor site of the epithelialized connective tissue (CT) graft significantly influences the patient’s morbidity. The aim of this study is to compare the effects of PRF and gelatin sponge on the healing of palatal donor sites and the patient’s morbidity. Methods: Forty patients with at least one site of Miller Class I or II gingival recession were treated by a coronally advanced flap with CT graft resulting from the de‐epithelialization of a free gingival graft. In the test group (20 patients), a PRF membrane was placed over the palatal wounds; conversely, the 20 control group patients were treated with an absorbable gelatin sponge. Patients were monitored at 1, 2, 3, and 4 weeks after surgery for the complete re‐epithelialization of the palatal wound (CWE), the alteration of sensitivity around the wound area, postoperative discomfort, and changes in feeding habits (CFH). Furthermore, the consumption of analgesics during the postoperative week 1 was assessed. Results: The test group showed a significantly faster CWE (P <0.001); 35% of the test patients showed CWE at the end of week 2 (controls, 10%), whereas at the end of week 3, all palatal wounds in the test patients epithelialized completely (controls, 25%). Similarly, test patients reported significantly less discomfort and CFH (P ≤ 0.02) and took a significantly lower dose of analgesics (P = 0.02). Conclusion: The PRF‐enriched palatal bandage significantly accelerates palatal wound healing and reduces the patient’s morbidity.     

Effect of low-level Er:YAG laser irradiation on cultured human gingival fibroblasts

BACKGROUND: Low-level laser irradiation has been reported to enhance wound healing. Activation of gingival fibroblasts (GF) has a potential for early wound healing in periodontal treatment. The present study aimed to investigate the direct effect of low-level Er:YAG laser irradiation on gingival fibroblasts proliferation in order to clarify the laser effect on healing. METHODS: Cultured human gingival fibroblasts (hGF) were exposed to low-power, pulsed Er:YAG laser irradiation with different energy densities ranging from 1.68 to 5.0 J/cm(2). The cultures were analyzed by means of trypan blue staining and counted under a light microscope. The effect of Er:YAG laser on hGF was also evaluated using a transmission electron microscope (TEM). RESULTS: Cultures irradiated with Er:YAG laser presented faster cell growth when compared with untreated controls. This difference was statistically significant. Transmission electron microscopy revealed rough endoplasmic reticulum, prominent Golgi complexes, and mitochondria after laser irradiation. CONCLUSIONS: Our results showed that the low-level Er:YAG laser irradiation stimulates the proliferation of cultured gingival fibroblasts. The optimal stimulative energy density was found to be 3.37 J/cm(2). This result suggests that Er:YAG laser irradiation may be of therapeutic benefit for wound healing.     

Phototherapy up-regulates dentin matrix proteins expression and synthesis by stem cells from human-exfoliated deciduous teeth

Objectives

The aim of this study was to evaluate the effects of infrared LED (850 nm) irradiation on dentin matrix proteins expression and synthesis by cultured stem cells from human exfoliated deciduous teeth (SHED).

Methods

Near-exfoliation primary teeth were extracted (n = 3), and SHED cultures were characterized by immunofluorescence using STRO-1, CD44, CD146, Nanog and OCT3/4 antibodies, before experimental protocol. The SHEDs were seeded (3 × 10⁴ cells/cm²) with DMEM containing 10% FBS. After 24-h incubation, the culture medium was replaced by osteogenic differentiation medium, and the cells were irradiated with LED light at energy densities (EDs) of 0 (control), 2, or 4 J/cm² (n = 8). The irradiated SHEDs were then evaluated for alkaline phosphatase (ALP) activity, total protein (TP) production, and collagen synthesis (SIRCOL™ Assay), as well as ALP, collagen type I (Col I), dentin sialophosphoprotein (DSPP), and dentin matrix acidic phosphoprotein (DMP-1) gene expression (qPCR). Data were analyzed by Kruskal–Wallis and Mann–Whitney tests (α = 0.05).

Results

Increased ALP activity and collagen synthesis, as well as gene expression of DSPP and ALP, were observed for both EDs compared with non-irradiated cells. The ED of 4 J/cm² also increased gene expression of COL I and DMP-1.

Conclusions

In conclusion, infrared LED irradiation was capable of biostimulating SHEDs by increasing the expression and synthesis of proteins related with mineralized tissue formation, with overall better results for the energy dose of 4 J/cm².

Clinical significance

Phototherapy is an additional approach for the clinical application of LED in Restorative Dentistry. Infrared LED irradiation of the cavity's floor could biostimulate subjacent pulp cells, improving local tissue healing.     

Irsogladine maleate regulates epithelial barrier function in tumor necrosis factor-α-stimulated human gingival epithelial cells

Fujita T, Yumoto H, Shiba H, Ouhara K, Miyagawa T, Nagahara T, Matsuda S, Kawaguchi H, Matsuo T, Murakami S, Kurihara H. Irsogladine maleate regulates epithelial barrier function in tumor necrosis factor‐α‐stimulated human gingival epithelial cells. J Periodont Res 2012; 47: 55–61. © 2011 John Wiley & Sons A/S Background and Objective: As epithelial cells function as a mechanical barrier, the permeability of the gingival epithelial cell layer indicates a defensive capability against invasion by periodontal pathogens. We have reported the expression of claudin‐1 and E‐cadherin, key regulators of permeability, in the gingival junctional epithelium. Irsogladine maleate (IM) is a medication for gastric ulcers and also regulates Aggregatibacter actinomycetemcomitans‐stimuated chemokine secretion and E‐cadherin expression in gingival epithelium. In this study, we have further investigated the effects of IM on the barrier functions of gingival epithelial cells under inflammatory conditions. Material and methods: We examined the permeability, and the expression of claudin‐1 and E‐cadherin, in human gingival epithelial cells (HGECs) stimulated with tumor necrosis factor (TNF)‐α, with or without IM. Results: TNF‐α increased the permeability of HGECs, and IM abolished the increase. TNF‐α reduced the expression of E‐cadherin in HGECs, and IM reversed the reduction. In addition, immunofluorescence staining showed that TNF‐α disrupted claudin‐1 expression in HGECs, and IM reversed this effect. Conclusion: The results suggest that IM reverses the TNF‐α‐induced disruption of the gingival epithelial barrier by regulating E‐cadherin and claudin‐1.     

Diabetes mellitus-associated periodontitis: differences between type 1 and type 2 diabetes mellitus

Aspriello SD, Zizzi A, Tirabassi G, Buldreghini E, Biscotti T, Faloia E, Stramazzotti D, Boscaro M, Piemontese M. Diabetes mellitus‐associated periodontitis: differences between type 1 and type 2 diabetes mellitus. J Periodont Res 2011; 46: 164–169. © 2010 John Wiley & Sons A/S Background and Objective: Although many studies have appeared about diabetes mellitus‐associated periodontitis, few have compared periodontitis inflammatory markers between type 1 (T1DM) and type 2 diabetes mellitus (T2DM), and information regarding this issue is scarce and contradictory. We evaluated the levels of plasma C‐reactive protein and of interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6) and tumour necrosis factor‐α (TNF‐α) in gingival crevicular fluid in two groups of subjects affected by T1DM and T2DM, in order to identify possible differences between the two classes in the inflammatory mechanisms of diabetes mellitus‐associated periodontitis. Material and Methods: Plasma C‐reactive protein and gingival crevicular fluidIL‐1β, IL‐6 and TNF‐α were measured in periodontitis patients affected by type 1 (P‐T1DM, n = 24) and type 2 diabetes mellitus (P‐T2DM, n = 24). Results: Gingival crevicular fluid levels of IL‐1β and TNF‐α in P‐T1DM subjects were significantly higher than in P‐T2DM subjects. In P‐T1DM subjects, we found significant negative correlations between the duration of diabetes mellitus and IL‐1β and between the duration of diabetes mellitus and TNF‐α. Conclusion: This study shows that IL‐1β and TNF‐α levels in periodontitis patients with T1DM are affected by the duration of diabetes mellitus.     

Different cross-linked types of collagen implanted in rat palatal gingiva

Collagen membrane preparations were manufactured with the aim of enhancing wound healing following periodontal surgery. After crosslinking by various processing methods (with ultraviolet and hexamethylenediisocyanate) and to various extents, two types of collagen (atelocollagen and tendon collagen) were implanted into a dissection site within palatal gingival tissue. The time course of healing responses was investigated histologically. Collagen implantation was found to accelerate fibrous connective tissue attachment to the root surface and inhibit apical migration of the junctional epithelium. Cross-linked atelocollagen was superior in biocompatibility to the other collagen membranes studied.     

Effects of He-Ne laser irradiation on fibroblasts derived from scar tissue of rat palatal mucosa

This study was carried out to clarify the mechanism of stimulating effects of low power He-Ne laser irradiation on wound healing process of rat palatal mucosa. Experimental wounds were made in 8-week-old male SD rats by surgically excising mucoperiosteum in hard palate. Fibroblasts were cultured from the scar tissue one month after the excision. Cells were investigated ultrascopically and the effects of He-Ne laser irradiation were examined by measuring DNA and collagen synthesis. Thermal change of the medium was also monitored. Cultured cells from the palatal wounds exhibited features of myofibroblasts. They exhibited well-developed bundles of microfilaments in the cytoplasm and had nuclei with foldings. Single irradiation of He-Ne laser at 28J/cm2 stimulated uptake of [3H] Thymidine into myofibroblasts and the stimulating effect decreased time dependently. There was no significant change in collagen synthesis. No thermal change was detected during irradiation. Ultrascopically, dilatation of rER was observed immediately after irradiation at 28J/cm2. But there was no modification in other cytoplasmic structures. The author concludes that He-Ne laser irradiation stimulates DNA synthesis of myofibroblasts without any degenerative changes in the organelle.     

Is There an Interaction Between Polycystic Ovary Syndrome and Gingival Inflammation?

Background: The aim of this study is to evaluate the gingival crevicular fluid (GCF), saliva, and serum concentrations of tumor necrosis factor‐α (TNF‐α), TNF‐α receptor‐1 (TNF‐αR1), TNF‐αR2, and interleukin‐6 (IL‐6) in non‐obese females with polycystic ovary syndrome (PCOS) and either clinically healthy periodontium or gingivitis. Methods: Thirty‐one females with PCOS and healthy periodontium, 30 females with PCOS and gingivitis, and 12 systemically and periodontally healthy females were included in the study. GCF, saliva, and serum samples were collected, and clinical periodontal measurements, body mass index, and Ferriman‐Gallwey score (FGS) were recorded. Sex hormones, cortisol, and insulin levels were measured. TNF‐α, TNF‐αR1, TNF‐αR2, and IL‐6 were determined by enzyme‐linked immunosorbent assay. Kruskal‐Wallis followed by Bonferroni‐corrected post hoc Mann‐Whitney U tests were used to analyze the data. Results: The PCOS + gingivitis group revealed significantly higher GCF, saliva, and serum IL‐6 concentrations than the PCOS + healthy group (P <0.0001). The two PCOS groups exhibited significantly higher saliva TNF‐α concentrations than the control group (P = 0.024 and P = 0.013, respectively). The FGS index was significantly higher in the PCOS + gingivitis group than the PCOS + healthy group (P = 0.030). The PCOS + gingivitis group revealed significantly higher insulin concentration than the PCOS + healthy and control groups (P = 0.014 and P <0.0001, respectively). Serum TNF‐α, TNF‐αRs, and serum, GCF, and salivary IL‐6 levels correlated with the clinical periodontal measurements. Conclusions: PCOS and gingival inflammation appear to act synergistically on the proinflammatory cytokines IL‐6 and TNF‐α. Thus, PCOS may have an impact on gingival inflammation or vice versa. Additional studies are warranted to clarify the possible relationship between PCOS and periodontal disease.     

The Effect of Platelet‐Rich Plasma on Healing of Palatal Donor Site following Connective Tissue Harvesting: A Pilot Study in Dogs

Background: Peri‐implant plastic surgery includes soft tissue enhancement by connective tissue grafting. The palatal donor site provides peri‐implant keratinized mucosa and soft tissue height. Platelet‐rich plasma (PRP) contains growth factors that may enhance early healing. Purpose: The present animal study investigated the effect of PRP on wound healing of palatal donor site after connective tissue harvesting. Materials and Methods: In 12 mongrel dogs, bilateral palatal connective tissues of 10 × 15 mm were harvested. At test site, PRP was applied into the wound, and the contralateral site served as control. The healing was evaluated clinically and histologically at 1 week, 2 weeks, and 4 weeks after surgeries. Exact binomial probability and Wilcoxon signed‐rank test were used to compare the clinical and histologic measurements. Results: No statistically significant differences between PRP and control sites were measured with regard to clinical healing (p = 1.000) and histologic variables, including inflammatory cells (p = .750), collagen fibers (p = .375), and granulation tissue (p = .500) at any time interval. Conclusion: The addition of PRP to palatal mucosal wound sites did not accelerate wound healing.     

Cytokine profile in the gingival crevicular fluid of rheumatoid arthritis patients with chronic periodontitis

The aim was to assess the cytokine profile in the gingival crevicular fluid (GCF) of rheumatoid arthritis (RA) patients with chronic periodontitis (CP). Databases were searched from 1991 to August 2013 using a combination of various keywords. Eight studies were included. The GCF concentrations of interleukin (IL)‐1β, IL‐4, IL‐10, matrix metalloproteinase (MMP)‐8, MMP‐13 and tumor necrosis factor‐alpha (TNF‐α) were reported to be higher in patients with RA than in healthy controls (HC) without CP. In one study, TNF‐α levels in GCF were significantly higher in HC than in RA patients receiving anti‐TNF‐α therapy. One study reported no significant difference in GCF TNF‐α levels among RA patients and HC regardless of anti‐TNF‐α therapy. One study reported no difference in IL‐1β and prostaglandin E₂ levels among RA patients and HC with CP. Raised levels of proinflammatory cytokines are exhibited in the GCF of RA patients with CP.     

The Effect of α‐Tocopherol and Selenium on Human Gingival Fibroblasts and Periodontal Ligament Fibroblasts In Vitro

Background: The aim of the present study is to evaluate the effect of α‐tocopherol and selenium on gingival fibroblasts (GFs) and periodontal ligament fibroblasts (PDLFs) in terms of proliferation, basic fibroblast growth factor (bFGF) release, collagen type I synthesis, and wound healing. Methods: Primary cultures of human GFs and PDLFs were isolated. Four test groups and a control group free of medication was formed. In group E, 60 μM α‐tocopherol was used, and in groups ES1, ES2, and ES3, the combination of 60 μM α‐tocopherol with 5 × 10^?9 M, 10 × 10^?9 M, and 50 × 10^?9 M selenium was used, respectively. Viability, proliferation, bFGF, and collagen type I synthesis from both cell types were evaluated at 24, 48, and 72 hours, and healing was compared on a new wound‐healing model at 12, 24, 36, 48, and 72 hours. Results: α‐Tocopherol alone significantly increased the healing rate of PDLFs at 12 hours and increased bFGF and collagen type I release from GFs and PDLFs at 24, 48, and 72 hours. The α‐tocopherol/selenium combination significantly enhanced the proliferation rate of both cells at 48 hours, decreased the proliferation of PDLFs at 72 hours, and increased the healing rate of GFs at 12 hours and PDLFs at 12 and 48 hours. bFGF and collagen type I synthesis was also increased in both cell types at 24, 48, and 72 hours by α‐tocopherol/selenium combination. Conclusion: α‐Tocopherol and α‐tocopherol/selenium combination is able to accelerate the proliferation rate and wound‐healing process and increase the synthesis of bFGF and collagen type I from both GFs and PDLFs.     

Effects of L-ascorbic acid 2-phosphate magnesium salt on the properties of human gingival fibroblasts

Tsutsumi K, Fujikawa H, Kajikawa T, Takedachi M, Yamamoto T, Murakami S. Effects of L ‐ascorbic acid 2‐phosphate magnesium salt on the properties of human gingival fibroblasts. J Periodont Res 2012; 47: 263–271. © 2011 John Wiley & Sons A/S Background and Objective: l ‐Ascorbic acid 2‐phosphate magnesium salt (APM) is an l ‐ascorbic acid (AsA) derivative developed to improve AsA stability and display effective biochemical characteristics. This study aimed to investigate the effects of APM on the functions and properties of human gingival fibroblasts with respect to the prevention of periodontal disease in comparison with those of AsA. Material and Methods: Human gingival fibroblasts were incubated in the presence or absence of APM or l ‐ascorbic acid sodium salt (AsANa). Intracellular AsA was analysed by HPLC. Collagen synthesis was measured by ELISA and real‐time RT‐PCR. Intracellular reactive oxygen species (ROS) induced by hydrogen peroxide (H₂O₂) were quantified using a fluorescence reagent, and cell damage was estimated with calcein acetoxymethyl ester. Furthermore, intracellular ROS induced by tumor necrosis factor‐α (TNF‐α) were quantified, and expression of TNF‐α‐induced interleukin‐8 expression, which increases due to inflammatory reactions, was measured by ELISA and real‐time RT‐PCR. Results: APM remarkably and continuously enhanced intracellular AsA and promoted type 1 collagen synthesis and mRNA expression. Furthermore, APM decreased cell damage through the suppression of H₂O₂‐induced intracellular ROS and inhibited interleukin‐8 production through the suppression of TNF‐α‐induced intracellular ROS. These effects of APM were superior to those of AsANa. Conclusion: These results suggest that APM is more effective than AsANa in terms of intake, collagen synthesis, decreasing cell damage and inhibiting interleukin‐8 expression in human gingival fibroblasts. This suggests that local application of APM can help to prevent periodontal disease.     

Effect of modulated photo‐activation on polymerization shrinkage behavior of dental restorative resin composites

This study investigated the influence of modulated photo‐activation on axial polymerization shrinkage, shrinkage force, and hardening of light‐ and dual‐curing resin‐based composites. Three light‐curing resin composites (SDR bulk‐fill, Esthet X flow, and Esthet X HD) and one dual‐curing material (Rebilda DC) were subjected to different irradiation protocols with identical energy density (27 J cm^?2): high‐intensity continuous light (HIC), low‐intensity continuous light (LIC), soft‐start (SS), and pulse‐delay curing (PD). Axial shrinkage and shrinkage force of 1.5‐mm‐thick specimens were recorded in real time for 15 min using custom‐made devices. Knoop hardness was determined at the end of the observation period. Statistical analysis revealed no significant differences among the curing protocols for both Knoop hardness and axial shrinkage, irrespective of the composite material. Pulse‐delay curing generated the significantly lowest shrinkage forces within the three light‐curing materials SDR bulk‐fill, Esthet X flow, and Esthet X HD. High‐intensity continuous light created the significantly highest shrinkage forces within Esthet X HD and Rebilda DC, and caused significantly higher forces than LIC within Esthet X flow. In conclusion, both the composite material and the applied curing protocol control shrinkage force formation. Pulse‐delay curing decreases shrinkage forces compared with high‐intensity continuous irradiation without affecting hardening and axial polymerization shrinkage.