Brigitte Grosgogeat

Influence of fluoride content and pH on the corrosion resistance of titanium and its alloys.

In the last decade, new titanium alloys have been developed in different areas of dentistry, such as TiAl6V4 and NiTi. Concurrently, treatments using fluoride supplementation, such as odontology fluoride containing gels, have also been widely used in odontology. The aim of this study was to compare the NiTi, NiTiCo and TiAl6V4 alloys with the titanium, regarding the corrosion resistance in Fusayama Meyer artificial saliva with different pH and fluoride contents. In the experimental methods, the corrosion potential was measured over time, then a linear sweep voltametric analysis measured the polarization resistances and corrosion currents. Our results have shown that TiAl6V4 alloys have a good corrosion resistance as good as that of titanium in Fusayama Meyer saliva and acid salivary solution, except NiTi and NiTiCo alloys. Conversely, we noticed, as for the titanium, a remarkable localized corrosion phenomenon of those new alloys in fluoride and acid-fluoride salivary solutions. The fluoride ions could cause the breakdown of the protective passivation layer that normally exists on the titanium and its alloys, leading to pit corrosion.

Measurement and evaluation of galvanic corrosion between titanium/Ti6Al4V implants and dental alloys by electrochemical techniques and auger spectrometry

The purpose of this study was to investigate, in different experimental conditions, the galvanic corrosion phenomena which can exist between a dental suprastructure and a dental implant. The electrochemical behavior of 7 alloy superstructures with titanium and titanium alloy (Ti6A14V) implants was investigated by electrochemical means in Fusayama-Meyer de-aerated saliva and Carter-Brugirard (AFNOR) non de-aerated saliva. Different techniques were used to obtain the value of the galvanic coupling current and potential for each couple. All showed very low corrosion rates, ranging from 10(-6) to 10(-8) A. Surface analysis confirmed these results.

Response of fibroblast activity and polyelectrolyte multilayer films coating titanium

OBJECTIVES The study of surface properties is a recent and crucial issue in the biomaterial fields applied to Odontology. The reference biomaterial in dental implantology is titanium. The principal objective is a perfect bio-integration in the oral ecosystem, both in terms of mucosal and bone tissues. The aim of this work was to optimize the tissue-titanium interface by applying polyelectrolyte multilayer films on the surface of titanium. METHODS The experimental study was undertaken on pure titanium samples. Two types of film ending with polycations or polyanions were selected. Both film types were built with a first poly(ethyleneimine) (PEI) base layer and composed either of poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) or of hyaluronic acid (HA) and poly(l-lysine) (PLL) layers. Final architectures were as follows: PEI-(PSS/PAH)(10), or PEI-(PSS/PAH)(10)-PSS, or chemically cross-linked PEI-(HA/PLL)(10) or PEI-(HA/PLL)(10)-HA. An analysis of the physicochemical characteristics of the surfaces was carried out by tensiometry measurements (dynamic contact angle, wettability, contact angle hysteresis) and atomic force microscopy. A biological study with human fibroblasts was followed over a 7-day culture period at days 0, 2, 4 and 7 to observe the cellular response in terms of morphology (scanning electron microscopy) and viability (Mosmanns test). RESULTS The results showed that polyelectrolyte multilayer films could be successfully deposited onto titanium as previously described for glass or composite. Fibroblast adhesion and proliferation was strongly dependent on film type. SEM observations of cells on the different films agreed with the viability cell test. Furthermore, films containing PSS/PAH generated a better cellular response than films containing cross-linked HA/PLL. CONCLUSION PSS/PAH polyelectrolyte films coating titanium could represent a new approach for oral bio-integration with great potential for clinical application in the fields of dental implantology. More particularly, the specific biofunctionalization of PSS/PAH films coating titanium could be envisioned by introducing layers of molecules that encourage the bio-integration process between the films.

Functionalization of Titanium with Chitosan via Silanation: Evaluation of Biological and Mechanical Performances

Complications in dentistry and orthopaedic surgery are mainly induced by peri-implant bacterial infections and current implant devices do not prevent such infections. The coating of antibacterial molecules such as chitosan on its surface would give the implant bioactive properties. The major challenge of this type of coating is the attachment of chitosan to a metal substrate. In this study, we propose to investigate the functionalization of titanium with chitosan via a silanation. Firstly, the surface chemistry and mechanical properties of such coating were evaluated. We also verified if the coated chitosan retained its biocompatibility with the peri-implant cells, as well as its antibacterial properties. FTIR and Tof-SIMS analyses confirmed the presence of chitosan on the titanium surface. This coating showed great scratch resistance and was strongly adhesive to the substrate. These mechanical properties were consistent with an implantology application. The Chitosan-coated surfaces showed strong inhibition of Actinomyces naeslundii growth; they nonetheless showed a non significant inhibition against Porphyromonas gingivalis after 32 hours in liquid media. The chitosan-coating also demonstrated good biocompatibility to NIH3T3 fibroblasts. Thus this method of covalent coating provides a biocompatible material with improved bioactive properties. These results proved that covalent coating of chitosan has significant potential in biomedical device implantation.

Comparison of corrosion behaviour in presence of oral bacteria

The aim of this study was to compare the resistance of the corrosion of dental alloys in a solution containing oral bacteria named Actinomyces viscosus (ATCC19246). In this paper, we explain the choice of this precise species of bacteria, then specify its culture in artificial saliva and the experimental precautions needed to avoid the pollution by other bacteria. The electrochemical behaviour of two dental alloys (Ni-Cr alloy and gold-based alloy) was investigated by electrochemical means in sterile Fusayama artificial saliva (AS), AS enriched with sterile yeast extract (YE) and YE modified by introducing bacteria (AV). Open-circuit potentials, potentiodynamic curves, polarization resistance and impedance spectroscopy are the electrochemical procedures selected for this work. It has thus been shown that the open-circuit potential of the non-precious alloy is always lower than that of the gold precious alloy, and the colonization of metal surface by bacteria caused a drop in open circuit potential. The electrochemical impedance spectroscopy results have shown that the electrolyte resistance decreased between the AS, YE and AV milieu, in the presence of bacteria a slight decrease in polarization resistance was observed with the precious alloy and an increase with the non-precious alloy. The drop in the electrolyte resistance cannot explain the change in polarization resistance. The influence of Actinomyces viscosus might be essentially due to the consumption of oxygen at the metal/electrolyte interface of the specimen. For the non-precious alloy, the absence of oxygen (instigator of corrosion) led to an increase in polarization resistance whereas the slight decrease for the precious alloys might be justified by the organic and inorganic metabolites released by bacteria in to the electrolyte. The scanning electron micrography after electrochemical analysis, confirmed the absence of contaminants. These preliminary results demonstrate the unquestionable influence of this bacteria on the corrosion behaviour of the alloys studied, however, further studies are necessary.

Surface Entrapment of Fibronectin on Electrospun PLGA Scaffolds for Periodontal Tissue Engineering

Abstract Nowadays, the challenge in the tissue engineering field consists in the development of biomaterials designed to regenerate ad integrum damaged tissues. Despite the current use of bioresorbable polyesters such as poly(l-lactide) (PLA), poly(d,l-lactide-co-glycolide) (PLGA), and poly-ɛ-caprolactone in soft tissue regeneration researches, their hydrophobic properties negatively influence the cell adhesion. Here, to overcome it, we have developed a fibronectin (FN)-functionalized electrospun PLGA scaffold for periodontal ligament regeneration. Functionalization of electrospun PLGA scaffolds was performed by alkaline hydrolysis (0.1 or 0.01 M NaOH). Then, hydrolyzed scaffolds were coated by simple deposition of an FN layer (10 μg/mL). FN coating was evidenced by X-ray photoelectron analysis. A decrease of contact angle and greater cell adhesion to hydrolyzed, FN-coated PLGA scaffolds were noticed. Suitable degradation behavior without pH variations was observed for all samples up to 28 days. All treated materials presented strong shrinkage, fiber orientation loss, and collapsed fibers. However, functionalization process using 0.01 M NaOH concentration resulted in unchanged scaffold porosity, preserved chemical composition, and similar mechanical properties compared with untreated scaffolds. The proposed simplified method to functionalize electrospun PLGA fibers is an efficient route to make polyester scaffolds more biocompatible and shows potential for tissue engineering.

Conservative approach of a symptomatic carious immature permanent tooth using a tricalcium silicate cement (Biodentine): a case report

The restorative management of deep carious lesions and the preservation of pulp vitality of immature teeth present real challenges for dental practitioners. New tricalcium silicate cements are of interest in the treatment of such cases. This case describes the immediate management and the follow-up of an extensive carious lesion on an immature second right mandibular premolar. Following anesthesia and rubber dam isolation, the carious lesion was removed and a partial pulpotomy was performed. After obtaining hemostasis, the exposed pulp was covered with a tricalcium silicate cement (Biodentine, Septodont) and a glass ionomer cement (Fuji IX extra, GC Corp.) restoration was placed over the tricalcium silicate cement. A review appointment was arranged after seven days, where the tooth was asymptomatic with the patient reporting no pain during the intervening period. At both 3 and 6 mon follow up, it was noted that the tooth was vital, with normal responses to thermal tests. Radiographic examination of the tooth indicated dentin-bridge formation in the pulp chamber and the continuous root formation. This case report demonstrates a fast tissue response both at the pulpal and root dentin level. The use of tricalcium silicate cement should be considered as a conservative intervention in the treatment of symptomatic immature teeth.

A chitosan‐hyaluronic acid hydrogel scaffold for periodontal tissue engineering

The current challenge in treating periodontitis is regenerating the periodontium. This motivates tissue-engineering researchers to develop scaffolds as artificial matrices that give mechanical support for osteoblasts, cementoblasts, gingival and periodontal ligament fibroblast cells. In this study, modified hyaluronic acid (HA) and chitosan (CS) were employed to create a hybrid CS-HA hydrogel scaffold for periodontal regeneration. CS, HA, and CS-HA scaffolds were obtained by freeze-drying technique, resulting in porous structures suitable for use in tissue engineering. Scaffolds were submitted to gamma and UV-sterilization without significant morphology changes. The ATR-FTIR spectra of CS-HA hydrogels showed peaks at 377 cm-1 , 1566 cm-1 , and 1614 cm-1 , representing secondary amide, primary amine, and carboxyl acid respectively, and it was also observed the emergence of peaks at 886 cm-1 , which probably represents the Schiff base formed in the case of hybrid CS-HA hydrogels. The scaffolds presented a high rate of PBS uptake, reaching values higher than 95%. Thermal degradation of HA scaffolds was around 225°C and CS was around 285°C. The ATR-FTIR spectra and swelling degree were slightly disturbed mainly after gamma sterilization, but degradation temperature did not change after sterilization. The performance of the CS-HA hydrogel scaffolds for in vitro cell culture was tested using NIH3T3 and MG63 cell lines. The Alamar Blue test showed a significant increase in cellular viability and high CD44 expression, suggesting that the cells migrated more when seeded onto the scaffolds.

Comparison of mechanical properties of a new fiber reinforced composite and bulk filling composites

Objectives The aim of this study was to evaluate the mechanical and physical properties of a newly developed fiber reinforced dental composite. Materials and Methods Fiber reinforced composite EverX Posterior (EXP, GC EUROPE), and other commercially available bulk fill composites, including Filtek Bulk Fill (FB, 3M ESPE), SonicFill (SF, Kerr Corp.), SureFil (SDR, Dentsply), Venus Bulk Fill (VB, HerausKultzer), Tetric evoceram bulk fill (TECB, Ivoclar Vivadent), and Xtra Base (XB, Voco) were characterized. Composite samples light-cured with a LED device were evaluated in terms of flexural strength, flexural modulus (ISO 4049, n = 6), fracture toughness (n = 6), and Vickers hardness (0, 2, and 4 mm in depth at 24 hr, n = 5). The EXP samples and the fracture surface were observed under a scanning electron microscopy. Data were statistically analyzed using one-way ANOVA and unpaired t-test. Results EXP, FB, and VB had significantly higher fracture toughness value compared to all the other bulk composite types. SF, EXP, and XB were not statistically different, and had significantly higher flexural strength values compared to other tested composite materials. EXP had the highest flexural modulus, VB had the lowest values. Vickers hardness values revealed SF, EXP, TECB, and XB were not statistically different, and had significantly higher values compared to other tested composite materials. SEM observations show well dispersed fibers working as a reinforcing phase. Conclusions The addition of fibers to methacrylate-based matrix results in composites with either comparable or superior mechanical properties compared to the other bulk fill materials tested.

In vitro orthodontic bracket bonding to porcelain

This in vitro study investigated the influence of using different combinations of bracket, adhesive, and light-curing source on the tensile bond strength to porcelain and on failure patterns at debonding. Tensile tests were performed using: one ceramic bracket versus one metal bracket, two orthodontic composites; type bisphenol A-glycidyldimethacrylate and urethane dimethacrylate (UDMA), and four light-curing units with the same range of emission spectrum but various light intensities: three light-emitting diode (LED) units and one halogen-based unit. One hundred and sixty porcelain samples were randomly divided into 16 equal groups. The porcelain surface was conditioned with 9 per cent hydrofluoric acid before silane application. The composite was photo-polymerized for 40 seconds. After storage in water at 37°C for 24 hours, the samples were subjected to tensile force until bond failure. Bond strength and bond failure mode were recorded; results were analysed (α = 0.05) using R language; linear model with constant variance for the bond strength and multinomial distribution for the failure mode. The bond strength in all groups was sufficient to withstand orthodontic treatment (>6 MPa). There was no statistical difference between the adhesives, but comparing bracket × light interaction, it was significantly higher with the ceramic bracket. No significant differences were seen between the metal bracket groups, but for the ceramic bracket, the results were significantly higher with the LED light. No fracture was observed in porcelain with the metal bracket but it occurred in 35 per cent of the ceramic bracket samples and the risk was higher when using UDMA composite and lower with LED high intensity light.