Laurent Bozec - Academia.edu (original) (raw)

Papers by Laurent Bozec

International Journal of Nanomedicine, 2015

Nanotechnology has rapidly expanded into all areas of science; it offers significant alternative ... more Nanotechnology has rapidly expanded into all areas of science; it offers significant alternative ways to solve scientific and medical questions and problems. In dentistry, nanotechnology has been exploited in the development of restorative materials with some significant success. This review discusses nanointerfaces that could compromise the longevity of dental restorations, and how nanotechnolgy has been employed to modify them for providing long-term successful restorations. It also focuses on some challenging areas in dentistry, eg, oral biofilm and cancers, and how nanotechnology overcomes these challenges. The recent advances in nanodentistry and innovations in oral health-related diagnostic, preventive, and therapeutic methods required to maintain and obtain perfect oral health, have been discussed. The recent advances in nanotechnology could hold promise in bringing a paradigm shift in dental field. Although there are numerous complex therapies being developed to treat many diseases, their clinical use requires careful consideration of the expense of synthesis and implementation.

Australian dental journal, Jan 25, 2015

To compare differences in wear of human enamel and dentine in vitro using a 3D measurement method... more To compare differences in wear of human enamel and dentine in vitro using a 3D measurement method comparing silica versus non-silica containing fluoridated dentifrices (Colgate Total(™) ; [CT] or Fluor Protector Gel(™) ; [FPG]). Mounted native enamel (n=36) and polished dentine (n=36) samples were subjected to 10 wear cycles. Each cycle consisted of: i) 1 hour remineralization in artificial saliva (AS); ii) 10 minute erosion (0.3% citric acid; pH=2.8); iii) 2 minute tooth-brush abrasion in AS (G1, control) or a slurry of 3:1 by weight of AS:dentifrice (G2=CT; G3=FPG) under a load of 2N. Each group contained 12 enamel and 12 dentine samples. Paired pre-and post-wear scans made with a contacting scanner were digitally superimposed using ball bearings as datum. Mean and (SD) enamel wear was G1=21.9μm (6.4); G2=15.2μm (2.8); G3=16.9μm (3.2). For enamel wear was not different between dentifrices (p=0.99). Both dentifrices resulted in less enamel wear compared to the control (p<0.05. D...

Objectives: Assessment of how replacement of the activator DMPT by the adhesive activator SAN, an... more Objectives: Assessment of how replacement of the activator DMPT by the adhesive activator SAN, and TEGDMA diluent with higher molecular weight PPGDMA in dental composites, affects dentine adhesion. Methods: Base monomer UDMA and diluent monomers TEGDMA (T) or PPGDMA (P) in 3:1 mass ratio were mixed with 5 wt % HEMA, 1wt% CQ and 1wt% DMPT (D) or SAN (N) to provide 4 composites designated as TD, TN, PD and PN. These were combined with silane treated glass particles. PLR was 4:1. The commercial composite Z250 was used as control. Ivory dentine blocks 5mm deep were used as received or after hydration / dehydration at 37C. Cylindrical holes (3mm diameter) were drilled and treated with 37 % phosphoric acid gel, and / or ibond total etch for 20s prior to filing with the composites. The debonding force (kN) required to push out the composite cylinders was determined (Table 1). Results:

This paper describes the application of Attenuated TotalReflection Fourier Transform Infra-red Sp... more This paper describes the application of Attenuated TotalReflection Fourier Transform Infra-red Spectroscopy (ATR-FTIR) together with Scanning Probe Microscopy (atomicforce microscopy and micro-thermal analysis) on acceleratedaged and archival parchment samples. Damageassessment by ATR-FTIR of collagen, the main constituentof parchment, was based on spectral changes in collagen,in particular within the amide I carbonyl stretching region.This is known to be sensitive to changes in the triple helicalstructure of collagen. Damage assessment by AtomicForce Microscopy (AFM) was based on changes in the periodicD spacing of the collagen fibrils. Measurements madeon the same samples showed that in damaged samplesthere was partial and eventually complete loss in the Dspacingof the collagen fibrils. This was particularly evidentin accelerated aged samples subjected to pollutantgas (SO2). Micro-thermal analysis (micro-TA) of the sameregions of parchment showed differences in the thermalbehaviou...

Staphylococcus aureus bacteria and titanium (Ti) implant surfaces were studied with atomic force ... more Staphylococcus aureus bacteria and titanium (Ti) implant surfaces were studied with atomic force microscopy (AFM) to understand early adhesion events occurring in dental implant biofilm formation. Both nanoindentation and fabrication of live-bacterium functionalized probes for force-spectroscopy are described for both strains.

Successful advance in development of bioactive composite have enable the production of a novel de... more Successful advance in development of bioactive composite have enable the production of a novel dentine adhering and high strength dental composites, with re-mineralising capability from calcium phosphate and integrated antibacterial components to provide resistance to bacterial microleakage have been produced. These new formulation contain PPGDMA as an alternative high molecular weight diluent monomer to more conventional TEGDMA. PPGDMA high molecular weight and flexibility enabled greater monomer conversion (>70%). The combination of adhesive co-initiator NTGGMA monomers and 4-META in addition to high calcium phosphate loading permits the bonding model dentine (ivory) without use of a separate composite adhesive.

The aim of the present study was to characterise the initial nanoadhesive interactions between li... more The aim of the present study was to characterise the initial nanoadhesive interactions between living Streptococcus sanguinis and Staphylococcus aureus bacteria and smooth titanium surfaces using single-cell force spectroscopy (SCFS) in buffer conditions. It is widely accepted that the installation of titanium dental implants is an efficacious treatment for oral reconstruction, however, long-term stability and success can be severely compromised if colonised by oral biofilm [1]. In the field of biomaterials, many efforts are currently being placed in understanding the biophysical events influencing bacterial adhesion and colonisation of implanted devices. Modern atomic force microscopy (AFM) setups are capable of characterising adhesion forces of single bacterium cells [2, 3]; however, the nanomechanic interaction between oral bacteria and titanium dental implants is yet to be fully understood. In this study, S. sanguinis and S. aureus strains were grown for 16 hours at 37°C in BHI ...

Objectives: Evaluate the effect of antibacterial chlorhexidine, reactive mono and tri calcium pho... more Objectives: Evaluate the effect of antibacterial chlorhexidine, reactive mono and tri calcium phosphate fillers and adhesive monomers, on the strength and ivory bonding of fibre –reinforced dental composites. Methods: Urethane dimethacrylate: triethylene glycol dimethacrylate (3:1) was mixed with 5 wt% adhesive monomer (2-hydroxyethyl methacrylate or methacrylate phosphate and 4-META). This was combined with silane treated glass particles containing fibres (5 wt%), chlorhexidine diacetate (0 or 5 wt%) and calcium phosphate (0 or 10 wt%). Powder to liquid ratio was 4:1. Biaxial flexural strength of light cured discs (10 mm diameter, 1 mm thick, n=6) was determined after 24 hours in distilled water and compared with commercial controls. Cylindrical holes 3 mm diameter were drilled through 5 mm deep ivory blocks. These were restored after etching with 37% phosphoric acid for 0 or 20s. The debonding forces (n=3) required to push out new material cylinders with no bonding agent were comp...

The scientific research in the field of Cultural Heritage conservation has more and more focused ... more The scientific research in the field of Cultural Heritage conservation has more and more focused its attention towards the development of new instruments for the examination of artefacts taking into account their historical value and fragility. In order to respond to the increasing demand from conservators of methodologies that do not involve sampling and irreversibly damaging of the object, non-destructive and non-invasive techniques are required for analysis, especially if they can perform in situ investigation of artefacts in their own display or storage environment.

Natural bone is a complex inorganic-organic composite material, in which apatite crystals and col... more Natural bone is a complex inorganic-organic composite material, in which apatite crystals and collagen fibrils are well organized into a hierarchical architecture. In tissue engineering, attempts in the synthesis of biomaterials have seen a remarkable growth in the recent past and current efforts have focused on biomimetic processes, in particular the development of three-dimensional collagenhydroxyapatite scaffolds with structure and properties comparable to hard native tissues, which can be difficult to replicate in a synthetic context. Collagen as a native scaffold is a promising biomimetic material that provides a 3D environment, supporting in vivo-like cellular activity and improving upon 2D cell culture [1]. Collagen has the ability to polymerise in vitro into fibrils that mimic, both morphologically and chemically, the properties of natural extracellular matrix, and provides excellent biocompatibility in various clinical applications, particularly for hard tissue regeneration [2][3][4].

Journal of Dental Research, 2015

ABSTRACT Adhesion of bacteria to dental implant surfaces is the critical initial step in the proc... more ABSTRACT Adhesion of bacteria to dental implant surfaces is the critical initial step in the process of biofilm colonization; however, the specific nanoadhesive interactions occurring during the first contact between bacterial cells and biomaterial substrates remain poorly understood. In this report, we utilize single-cell force spectroscopy to characterize the dynamics of the initial interaction between living Staphylococcus aureus cells and machined titanium surfaces at the nanoscale. Values for maximum adhesion force were found to increase from 0-s (-0.27 ± 0.30 nN) to 60-s (-9.15 ± 0.78 nN) surface delays, with similar results observed for total adhesion work (7.39 ± 2.38 and 988.06 ± 117.08 aJ, respectively). Single unbinding events observed at higher surface delays were modeled according to the wormlike chain model, obtaining molecular contour-length predictions of 314.06 ± 9.27 nm. Average single-bond rupture forces of -0.95 ± 0.04 nN were observed at increased contact times. Short- and long-range force components of bacterial adhesion were obtained by Poisson analysis of single unbinding event peaks, yielding values of -0.75 ± 0.04 and -0.58 ± 0.15 nN, respectively. Addition of 2-mg/mL chlorhexidine to the buffer solution resulted in the inhibition of specific adhesive events but an increased overall adhesion force and work. These results suggest that initial attachment of S. aureus to smooth titanium is mostly mediated by short-range attractive forces observed at higher surface delays. © International & American Associations for Dental Research 2015. Article can be found at: http://jdr.sagepub.com/content/early/2015/06/26/0022034515591485.abstract

Journal of biomedical materials research. Part A, Jan 26, 2015

Surface roughness on implant materials has been shown to be highly influential on the behavior of... more Surface roughness on implant materials has been shown to be highly influential on the behavior of osteogenic cells. Four surface topographies were engineered on cobalt chromium molybdenum (CoCrMo) in order to examine this influence on human mesenchymal stem cells (MSC). These treatments were smooth polished (SMO), acid etched (AE) using HCl 7.4% and H2 SO4 76% followed by HNO3 30%, sand blasted, and acid etched using either 50 μm Al2 O3 (SLA50) or 250 μm Al2 O3 grit (SLA250). Characterization of the surfaces included energy dispersive X-ray analysis (EDX), contact angle, and surface roughness analysis. Human MSCs were cultured onto the four CoCrMo substrates and markers of cell attachment, retention, proliferation, cytotoxicity, and osteogenic differentiation were studied. Residual aluminum was observed on both SLA surfaces although this appeared to be more widely spread on SLA50, whilst SLA250 was shown to have the roughest topography with an Ra value greater than 1 μm. All substra...

Materials, 2015

This study was performed to develop alternating dentine adhesion models that could help in the ev... more This study was performed to develop alternating dentine adhesion models that could help in the evaluation of a self-bonding dental composite. For this purpose dentine from human and ivory was characterized chemically and microscopically before and after acid etching using Raman and SEM. Mechanical properties of dentine were determined using 3 point bend test. Composite bonding to dentine, with and without use of acid pre-treatment and/or the adhesive, were assessed using a shear bond test. Furthermore, micro gap formation after restoration of 3 mm diameter cavities in dentine was assessed by SEM. Initial hydroxyapatite level in ivory was half that in human dentine. Surface hydroxyapatites decreased by approximately half with every 23 s of acid etch. The human dentine strength (56 MPa) was approximately double that of ivory, while the modulus was almost comparable to that of ivory. With adhesive use, average shear bond strengths were 30 and 26 MPa with and without acid etching. With no adhesive, average bond strength was 6 MPa for conventional composites. This, however, increased to 14 MPa with a commercial flowable "self-bonding" composite or upon addition of low levels of an acidic monomer to the experimental composite. The acidic monomer additionally reduced micro-gap formation with the experimental composite. Improved bonding and mechanical properties should reduce composite failures due to recurrent caries or fracture respectively. OPEN ACCESS Materials 2015, 8 2111

RSC Adv., 2014

Ultraviolet (UV) photofunctionalization has been shown to be highly effective at improving the os... more Ultraviolet (UV) photofunctionalization has been shown to be highly effective at improving the osteoconductivity of titanium and TiO 2 coated materials. We aimed to assess whether the bioactivity of TiO 2 coated cobalt chromium molybdenum (CoCrMo) could be enhanced by UV photofunctionalization of the surface TiO 2 layer. Using atmospheric pressure chemical vapour deposition (APCVD) a thin layer of anatase TiO 2 was deposited onto smooth CoCrMo discs (referred to as CCMT). Human mesenchymal stem cells (MSCs) were cultured onto CCMT substrates which had been treated with UV light for 24 hours and identical substrates which had not undergone UV treatment. UV treated CCMT promoted a superior cell response in the form of enhancing markers of cell adhesion. This included stimulating the development of larger cells with increased levels of the adhesion protein vinculin and cytoskeletal protein f-actin (p < 0.05). In addition, MSCs were shown to have superior retention to UV treated CCMT after 3 and 24 hours (p < 0.05). Other cellular processes including proliferation, attachment, migration and differentiation were not affected by UV photofunctionalization. Despite this, the enhancement in cellular adhesion alone should result in an improvement in MSC retention to implant surfaces following surgery, and as a consequence, increase MSC resistance to dislodgement from external forces such as blood flow and micro motion.

Quintessence international (Berlin, Germany : 1985)

To present the application of two different soft tissue grafts around dental implants during stag... more To present the application of two different soft tissue grafts around dental implants during stage-two surgery. Furthermore, the ultrastructure of these materials is shown and discussed using scanning electron microscopy (SEM). Although soft tissue autografts may be currently regarded as the gold standard, harvesting of these grafts might lead to higher morbidity, longer chair time, and intra-/postoperative complications at the donor site. New developments in collagen scaff olds have provided an alternative to successfully replace autologous grafts in clinical practice. The SEM pictures clearly show the different composition of a bilayer scaff old (collagen matrix, CM) and a porcine acellular dermal matrix (ADM). These distinctive properties lead to different possible indications. Within the presented cases, ADM was used to augment the ridge contour and was placed into a buccal pouch to achieve complete coverage and an uneventful closed healing. On the other side, CM was left expose...

Both scanning electron microscopy (SEM) and micro-thermal analysis (micro-TA) have been used to a... more Both scanning electron microscopy (SEM) and micro-thermal analysis (micro-TA) have been used to assess the level of degradation of collagen in historical and accelerated-aged parchments. SEM provides information on the overall morphology of the collagen fibre structure at the mesoand microscopic scale, whereas micro-TA provides thermo-mechanical information on the microscopic scale. Morphology changes observed with SEM have been used to classify historical and accelerated parchment samples in four damage categories. To determine whether these morphology changes are correlated with changes in thermo-mechanical properties, micro-TA measurements have been performed on selected samples. Although sample preparation methods still have to be optimized, first results indicate that micro-TA is a sensitive technique that can detect localized changes in thermo-mechanical properties and can provide more subtle understanding of the level of damage. Therefore the combination of SEM and micro-TA can provide a powerful tool for conservators.

Journal of Biomedical Materials Research Part A, 2014

The current gold standard material for orthopedic applications is titanium (Ti), however, other m... more The current gold standard material for orthopedic applications is titanium (Ti), however, other materials such as cobalt-chromium-molybdenum (CoCrMo) are often preferred due to their wear resistance and mechanical strength. This study investigates if the bioactivity of CoCrMo can be enhanced by coating the surface with titanium oxide (TiO 2 ) by atmospheric pressure chemical vapor deposition (CVD), thereby replicating the surface oxide layer found on Ti. CoCrMo, TiO 2 -coated CoCrMo (CCMT) and Ti substrates were used for this study. Cellular f-actin distribution was shown to be noticeably different between cells on CCMT and CoCrMo after 24 h in osteogenic culture, with cells on CCMT exhibiting greater spread with developed protrusions. Osteogenic differentiation was shown to be enhanced on CCMT compared to CoCrMo, with increased calcium ion content per cell (p < 0.05), greater hydroxyapatite nodule formation (p < 0.05) and reduced type I collagen deposition per cell (p < 0.05). The expression of the focal adhesion protein vinculin was shown to be marginally greater on CCMT compared to CoCrMo, whereas AFM results indicated that CCMT required more force to remove a single cell from the substrate surface compared to CoCrMo (p < 0.0001). These data suggest that CVD TiO 2 coatings may have the potential to increase the biocompatibility of CoCrMo implantable devices. V C 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 00A:000-000, 2014.