Melatonin expression in periodontitis and obesity: An experimental in-vivo investigation

BACKGROUND AND OBJECTIVE

Melatonin deficiency has been associated with obesity and systemic inflammation. This study aims to evaluate whether melatonin could interfere with the mechanisms of co-morbidity linking obesity and periodontitis.

MATERIAL AND METHODS

Twenty-eight male Wistar rats were randomly divided in 4 groups: control group (Con) (fed with standard diet); high-fat diet group (HFD) (fed with a diet containing 35.2% fat); Con group with induced periodontitis (Con-Perio) and HFD group with induced periodontitis (HFD-Perio). To induce periodontitis, the method of oral gavages with Porphyromonas gingivalis ATCC W83K1 and Fusobacterium nucleatum DMSZ 20482 was used. Circulating melatonin levels were analyzed by multiplex immunoassays. Periodontitis was assessed by alveolar bone loss (micro-computed tomography and histology) and by surrogate inflammatory outcomes (periodontal pocket depth, modified gingival index and plaque dental index).

RESULTS

Plasma melatonin levels were significantly decreased (P < .05) in the obese rats with periodontitis when compared with controls or with either obese or periodontitis rats. Alveolar bone loss increased 27.71% (2.28 µm) in HFD-Perio group compared with the Con group. The histological analysis showed marked periodontal tissue destruction with osteoclast activity, particularly in the HFD-Perio group. A significant negative correlation (P < .05) was found between periodontal pocket depth, modified gingival index and circulating melatonin levels.

CONCLUSION

Obese and periodontitis demonstrated significantly lower melatonin concentrations when compared with controls, but in obese rats with periodontitis these concentrations were even significantly lower when compared with either periodontitis or obese rats. These results may indicate that melatonin deficiency could be a key mechanism explaining the co-morbidity effect in the association between obesity and periodontitis.

Effect of cathodic polarization on coating doxycycline on titanium surfaces

Cathodic polarization has been reported to enhance the ability of titanium based implant materials to interact with biomolecules by forming titanium hydride at the outermost surface layer. Although this hydride layer has recently been suggested to allow the immobilization of the broad spectrum antibiotic doxycycline on titanium surfaces, the involvement of hydride in binding the biomolecule onto titanium remains poorly understood. To gain better understanding of the influence this immobilization process has on titanium surfaces, mirror-polished commercially pure titanium surfaces were cathodically polarized in the presence of doxycycline and the modified surfaces were thoroughly characterized using atomic force microscopy, electron microscopy, secondary ion mass spectrometry, and angle-resolved X-ray spectroscopy. We demonstrated that no hydride was created during the polarization process. Doxycycline was found to be attached to an oxide layer that was modified during the electrochemical process. A bacterial assay using bioluminescent Staphylococcus epidermidis Xen43 showed the ability of the coating to reduce bacterial colonization and planktonic bacterial growth.

Antibacterial effect of doxycycline-coated dental abutment surfaces

Biofilm formation on dental abutment may lead to peri-implant mucositis and subsequent peri-implantitis. These cases are clinically treated with antibiotics such as doxycycline (Doxy). Here we used an electrochemical method of cathodic polarization to coat Doxy onto the outer surface of a dental abutment material. The Doxy-coated surface showed a burst release in phosphate-buffered saline during the first 24 h. However, a significant amount of Doxy remained on the surface for at least 2 weeks especially on a 5 mA-3 h sample with a higher Doxy amount, suggesting both an initial and a long-term bacteriostatic potential of the coated surface. Surface chemistry was analyzed by x-ray photoelectron spectroscopy and secondary ion mass spectrometry. Surface topography was evaluated by field emission scanning electron microscopy and blue-light profilometry. Longer polarization time from 1 h to 5 h and higher current density from 1 to 15 mA cm(-2) resulted in a higher amount of Doxy on the surface. The surface was covered by a layer of Doxy less than 100 nm without significant changes in surface topography. The antibacterial property of the Doxy-coated surface was analyzed by biofilm and planktonic growth assays using Staphylococcus epidermidis. Doxy-coated samples reduced both biofilm accumulation and planktonic growth in broth culture, and also inhibited bacterial growth on agar plates. The antibacterial effect was stronger for samples of 5 mA-3 h coated with a higher amount of Doxy compared to that of 1 mA-1 h. Accordingly, an abutment surface coated with Doxy has potential for preventing bacterial colonization when exposed to the oral cavity. Doxy-coating could be a viable way to control peri-implant mucositis and prevent its progression into peri-implantitis.

Alginate hydrogel enriched with enamel matrix derivative to target osteogenic cell differentiation in TiO2 scaffolds

The purpose of bone tissue engineering is to employ scaffolds, cells, and growth factors to facilitate healing of bone defects. The aim of this study was to assess the viability and osteogenic differentiation of primary human osteoblasts and adipose tissue–derived mesenchymal stem cells from various donors on titanium dioxide (TiO₂) scaffolds coated with an alginate hydrogel enriched with enamel matrix derivative. Cells were harvested for quantitative reverse transcription polymerase chain reaction on days 14 and 21, and medium was collected on days 2, 14, and 21 for protein analyses. Neither coating with alginate hydrogel nor alginate hydrogel enriched with enamel matrix derivative induced a cytotoxic response. Enamel matrix derivative–enriched alginate hydrogel significantly increased the expression of osteoblast markers COL1A1, TNFRSF11B, and BGLAP and secretion of osteopontin in human osteoblasts, whereas osteogenic differentiation of human adipose tissue–derived mesenchymal stem cells seemed unaffected by enamel matrix derivative. The alginate hydrogel coating procedure may have potential for local delivery of enamel matrix derivative and other stimulatory factors for use in bone tissue engineering.

The influence of sintering conditions on microstructure and mechanical properties of titanium dioxide scaffolds for the treatment of bone tissue defects

In this study the attempts to improve mechanical properties of highly-porous titanium dioxide scaffolds produced by polymer sponge replication method were investigated. Particularly the effect of two-step sintering at different temperatures on microstructure and mechanical properties (compression test) of the scaffolds were analysed. To this end microcomputed tomography and scanning electron microscopy were used as analytical methods. Our experiments showed that the most appropriate conditions of manufacturing were when the scaffolds were heat-treated at 1500 °C for 1 h followed by sintering at 1200 °C for 20 h. Such scaffolds exhibited the highest compressive strength which was correlated with the highest linear density and the lowest size of grains. Moreover, grain size distribution was narrower with predominating fraction of fine grains 10-20 μm in size. Smaller grains and higher linear density sug- gested that in this case densification process prevailed over undesirable process of grain coarsening, which finally resulted in im- proved mechanical properties of the scaffolds.

Cathodic Polarization Coats Titanium Based Implant Materials with Enamel Matrix Derivate (EMD)

The idea of a bioactive surface coating that enhances bone healing and bone growth is a strong focus of on-going research for bone implant materials. Enamel matrix derivate (EMD) is well documented to support bone regeneration and activates growth of mesenchymal tissues. Thus, it is a prime candidate for coating of existing implant surfaces. The aim of this study was to show that cathodic polarization can be used for coating commercially available implant surfaces with an immobilized but functional and bio-available surface layer of EMD. After coating, XPS revealed EMD-related bindings on the surface while SIMS showed incorporation of EMD into the surface. The hydride layer of the original surface could be activated for coating in an integrated one-step process that did not require any pre-treatment of the surface. SEM images showed nano-spheres and nano-rods on coated surfaces that were EMD-related. Moreover, the surface roughness remained unchanged after coating, as it was shown by optical profilometry. The mass peaks observed in the matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) analysis confirmed the integrity of EMD after coating. Assessment of the bioavailability suggested that the modified surfaces were active for osteoblast like MC3M3-E1 cells in showing enhanced Coll-1 gene expression and ALP activity.

The influence of surface nanoroughness, texture and chemistry of TiZr implant abutment on oral biofilm accumulation

OBJECTIVES

The aim of the study was to examine surface nanoroughness, texture and chemistry of dental implant abutment and to investigate how these parameters influence oral biofilm formation in healthy subjects.

MATERIALS AND METHODS

Eight different nanorough TiZr surfaces were produced by polishing, machining, cathodic polarization and acid etching. Surface topography was examined using field emission scanning electron microscope and a blue light laser profilometer. Surface chemistry was analyzed by secondary ion mass spectrometry and X-ray photoelectron spectroscopy. Surface hydrophilicity was tested by measuring contact angle on the surfaces. A human in vivo study using a splint model was employed to evaluate oral biofilm accumulation on these surfaces.

RESULTS

Different surface textures (flat, grooved and irregular) were created with nanoroughness from 29 to 214 nm. Some test surfaces were incorporated with hydrogen by cathodic polarization and/or acid etching with HCl/H(2)SO(4). Nanoroughness (S(a)) positively correlated with microbial adhesion. Biofilm accumulation was less pronounced on flat and grooved than on irregular surfaces. No significant association between hydrogen content or hydrophilicity of the surface and biofilm accumulation was observed.

CONCLUSIONS

Nanoroughness (< 214 nm) and surface texture influence oral biofilm accumulation independent of surface chemistry and hydrophilicity. Surface hydrogen, which has previously been shown to promote fibroblast growth, does not affect biofilm formation.

Bioactive implant surface with electrochemically bound doxycycline promotes bone formation markers in vitro and in vivo

OBJECTIVES

The objective of this study was to demonstrate a successful binding of Doxy hyclate onto a titanium zirconium alloy surface.

METHODS

The coating was done on titanium zirconium coins in a cathodic polarization setup. The surface binding was analyzed by SEM, SIMS, UV-vis, FTIR and XPS. The in vitro biological response was tested with MC3T3-E1 murine pre-osteoblast cells after 14 days of cultivation and analyzed in RT-PCR. A rabbit tibial model was also used to confirm its bioactivity in vivo after 4 and 8 weeks healing by means of microCT.

RESULTS

A mean of 141 μg/cm(2) of Doxy was found firmly attached and undamaged on the coin. Inclusion of Doxy was documented up to a depth of approximately 0.44 μm by tracing the (12)C carbon isotope. The bioactivity of the coating was documented by an in vitro study with murine osteoblasts, which showed significantly increased alkaline phosphatase and osteocalcin gene expression levels after 14 days of cell culture along with low cytotoxicity. Doxy coated surfaces showed increased bone formation markers at 8 weeks of healing in a rabbit tibial model.

SIGNIFICANCE

The present work demonstrates a method of binding the broad spectrum antibiotic doxycycline (Doxy) to an implant surface to improve bone formation and reduce the risk of infection around the implant. We have demonstrated that TiZr implants with electrochemically bound Doxy promote bone formation markers in vitro and in vivo.

Increased reactivity and in vitro cell response of titanium based implant surfaces after anodic oxidation

In the quest for improved bone growth and attachment around dental implants, chemical surface modifications are one possibility for future developments. The biological properties of titanium based materials can be further enhanced with methods like anodic polarization to produce an active rather than a passive titanium oxide surface. Here we investigate the formation of hydroxide groups on sand blasted and acid etched titanium and titanium-zirconium alloy surfaces after anodic polarization in an alkaline solution. X-ray photoelectron spectroscopy shows that the activated surfaces had increased reactivity. Furthermore the activated surfaces show up to threefold increase in OH(-) concentration in comparison to the original surface. The surface parameters Sa, Sku, Sdr and Ssk were more closely correlated to time and current density for titanium than for titanium-zirconium. Studies with MC3T3-E1 osteoblastic cells showed that OH(-) activated surfaces increased mRNA levels of osteocalcin and collagen-I.

Enhanced in vitro osteoblast differentiation on TiO2 scaffold coated with alginate hydrogel containing simvastatin

The aim of this study was to develop a three-dimensional porous bone graft material as vehicle for simvastatin delivery and to investigate its effect on primary human osteoblasts from three donors. Highly porous titanium dioxide (TiO₂) scaffolds were submerged into simvastatin containing alginate solution. Microstructure of scaffolds, visualized by scanning electron microscopy and micro-computed tomography, revealed an evenly distributed alginate layer covering the surface of TiO₂ scaffold struts. Progressive and sustained simvastatin release was observed for up to 19 days. No cytotoxic effects on osteoblasts were observed by scaffolds with simvastatin when compared to scaffolds without simvastatin. Expression of osteoblast markers (collagen type I alpha 1, alkaline phosphatase, bone morphogenetic protein 2, osteoprotegerin, vascular endothelial growth factor A and osteocalcin) was quantified using real-time reverse transcriptase–polymerase chain reaction. Secretion of osteoprotegerin, vascular endothelial growth factor A and osteocalcin was analysed by multiplex immunoassay (Luminex). The relative expression and secretion of osteocalcin was significantly increased by cells cultured on scaffolds with 10 µM simvastatin when compared to scaffolds without simvastatin after 21 days. In addition, secretion of vascular endothelial growth factor A was significantly enhanced from cells cultured on scaffolds with both 10 nM and 10 µM simvastatin when compared to scaffolds without simvastatin at day 21. In conclusion, the results indicate that simvastatin-coated TiO₂ scaffolds can support a sustained release of simvastatin and induce osteoblast differentiation. The combination of the physical properties of TiO₂ scaffolds with the osteogenic effect of simvastatin may represent a new strategy for bone regeneration in defects where immediate load is wanted or unavailable.

Coating of metal implant materials with strontium

The aim of this study was to show that cathodic polarization can be used for coating commercial implant surfaces with an immobilized but functional and bioavailable surface layer of strontium (Sr). Moreover, this study assessed the effect of fluorine on Sr-attachment. X-ray photoelectron spectroscopy revealed that addition of fluorine (F) to the buffer during coating increased surface Sr-amounts but also changed the chemical surface composition by adding SrF2 alongside of SrO whereas pre-treatment of the surface by pickling in hydrofluoric acid appeared to hinder Sr-attachment. Assessment of the bio-availability hinted at a positive effect of Sr on cell differentiation given that the surface reactivity of the original surface remained unchanged. Additional SrF2 on the surface appeared to reduce undesired surface contamination while maintaining the surface micro-topography and micro-morphology. Anyhow, this surface modification revealed to create nano-nodules on the surface.

Differential response of human gingival fibroblasts to titanium- and titanium-zirconium-modified surfaces

BACKGROUND AND OBJECTIVE

Gingival fibroblasts are responsible for the constant adaptation, wound healing and regeneration of gingival connective tissue. New titanium-zirconium (TiZr) abutment surfaces have been designed to improve soft tissue integration and reduce implant failure compared with titanium (Ti). The aim of the present study was first to characterize a primary human gingival fibroblast (HGF) model and secondly to evaluate their differential response to Ti and TiZr polished (P), machined (M) and machined + acid-etched (modMA) surfaces, respectively.

MATERIAL AND METHODS

HGF were cultured on tissue culture plastic or on the different Ti and TiZr surfaces. Cell morphology was evaluated through confocal and scanning electron microscopy. A wound healing assay was performed to evaluate the capacity of HGF to close a scratch. The expression of genes was evaluated by real-time RT-PCR, addressing: (i) extracellular matrix organization and turnover; (ii) inflammation; (iii) cell adhesion and structure; and (iv) wound healing. Finally, cells on Ti/TiZr surfaces were immunostained with anti-ITGB3 antibodies to analyze integrin β3 production. Matrix metalloproteinase-1 (MMP1) and inhibitor of metallopeptidases-1 (TIMP1) production were analyzed by enzyme-linked immunosorbent assays.

RESULTS

On tissue culture plastic, HGF showed no differences between donors on cell proliferation and on the ability for wound closure; α-smooth muscle actin was overexpressed on scratched monolayers. The differentiation profile showed increased production of extracellular matrix components. Ti and TiZr showed similar biocompatibility with HGF. TiZr increased integrin-β3 mRNA and protein levels, compared with Ti. Cells on TiZr surfaces showed higher MMP1 protein than Ti surfaces, although similar TIMP1 protein production. In this in vitro experiment, P and M surfaces from both Ti and TiZr showed better HGF growth than modMA.

CONCLUSION

Taking into account the better mechanical properties and bioactivity of TiZr compared with Ti, the results of the present study show that TiZr is a potential clinical candidate for soft tissue integration and implant success.

Surface hydride on titanium by cathodic polarization promotes human gingival fibroblast growth

Connective tissue seal to dental abutment is crucial for peri-implant health. Several efforts have been made previously to optimize abutment surfaces, but no consensus has been reached regarding the optimal surface architecture and/or composition for soft tissue seal. Here, we report on experiments using cathodic polarization in organic acids to optimize titanium (Ti) surfaces for use as abutments. The three main factors affecting surface topography and chemistry were electrolyte composition, current density, and polarization time. Under identical conditions, oxalic acid created rougher surfaces than tartaric acid and acetic acid, and acetic acid produced more surface hydride. Surface hydride amount was suggested to first increase and then decrease with current density from 1 mA/cm(2) to 15 mA/cm(2) . The complexity of the surface topography and hydride production both increased with polarization time. Proliferation rate of human gingival fibroblasts (HGFs) was positively correlated with surface hydride content, suggesting the positive effect of surface hydride on connective tissue growth around dental abutment. Changes in surface topography and hydrophilicity did not significantly influence HGF growth.

Effect of short LED lamp exposure on wear resistance, residual monomer and degree of conversion for Filtek Z250 and Tetric EvoCeram composites

OBJECTIVES

The latest LED dental curing devices claim sufficient curing of restorative materials with short curing times. This study evaluates mechanical and chemical properties as a function of curing time of two commercial composite filling materials cured with three different LED lamps.

METHODS

The composites were Filtek Z250 (3M ESPE) and Tetric EvoCeram (Ivoclar Vivadent) and the LED curing devices were bluephase 16i (Ivoclar Vivadent), L.E.Demetron II (Kerr) and Mini L.E.D. (Satelec). Control samples were cured with a QTH-lamp (VCL 400, Kerr). The wear resistance after simulated tooth brushing, degree of conversion, curing depth, and amounts of residual monomers were measured after different curing times.

RESULTS

The results of this study show that short curing time with high-intensity LEDs may influence the bulk properties of the materials, resulting in lower curing depth and increased residual monomer content. The measured surface properties of the materials, degree of conversion and wear resistance, were not affected by short curing times to the same extent.

SIGNIFICANCE

This study demonstrates that reduced exposure time with high intensity LEDs can result in composite restorations with inferior curing depth and increased leaching of monomers. Dentists are recommended to use sufficient curing times even with high intensity LEDs to ensure adequate curing and minimize the risk of monomer leaching.

Chemical debridement of contaminated titanium surfaces: an in vitro study

OBJECTIVE

To compare the efficacy of different chemical solutions when used for chemical debridement of biofilm contaminated titanium surfaces in an in-vitro experimental study.

MATERIALS AND METHODS

Commercially pure titanium discs with a diameter of 6.2 mm and height of 2 mm, mirror-polished with a measured surface amplitude value SA = 0.037 μm ± 0.009 were used as test-surfaces. A biofilm was simulated with multi-layers of Staphylococcus epidermidis ATCC359844 covering the entire titanium surface. The chemical agents tested were: 3% H2O2, 0.2% Chlorhexidine, 24% EDTA-gel, 3% H2O2 mixed with 1.6 g/L TiO2 and sterile saline solution. The decontamination effect was evaluated by optical density analysis using spectrophotometry and with scanning electron microscopy (SEM) images of the remaining biofilm.

RESULTS

The suspensions of 3% H2O2 and 1.6 g/L TiO2 or 3% H2O2 alone were the most effective in removing S. epidermidis biofilms (p < 0.05), whereas 0.2% chlorhexidine or 24% EDTA gel had no significant effects. SEM images of the remaining biofilms supported the quantitative results indicating the higher efficacy of 3% H2O2 and 1.6 g/L TiO2 or 3% H2O2 alone. It also revealed that EDTA, despite a non-significant effect on reducing the amount of established biofilms, was able to alter the biofilm architecture, as demonstrated by increased interspaced regions.

CONCLUSIONS

In this in vitro study the decontamination potential of a suspension of 3% H2O2 and 1.6 g/L TiO2 or 3% H2O2 alone were encouraging. Whether such procedures would have a similar effect in vivo remains to be determined.