Papers by Julian Leprince
The new microbiologica, 2015
Electric currents have been shown to promote the antimicrobial effectiveness of several biocides ... more Electric currents have been shown to promote the antimicrobial effectiveness of several biocides against microbial biofilms. Therefore, the objective of this work was to test the null hypothesis that low electric direct currents (DC) do not influence chlorhexidine (CHX) efficacy against the periodontal pathogen Porphyromonas gingivalis within a biofilm. A brain heart infusion medium inoculated with Streptococcus gordonii and P. gingivalis was perfused for 7 days in anaerobiosis through two modified Robbins devices (MRD) assembled in parallel. Biofilms grew on hydroxyapatite discs placed at the bottom of the MRD plugs, and were then treated for 10 min with either CHX or CHX/DC (1.5 mA or 10 mA). The bactericidal effect against biofilms was then evaluated by comparing the mean proportions of P. gingivalis killed. In the first series of experiments (CHX ± 1.5mA), the proportions of P. gingivalis killed were 81.1% for biofilms undergoing CHX and 79.1% when they were additionally treated...
Dental Materials, 2016
The use of a Type I photoinitiator (monoacylphosphine oxide, MAPO) was described as advantageous ... more The use of a Type I photoinitiator (monoacylphosphine oxide, MAPO) was described as advantageous in a model formulation, as compared to the conventional Type II photoinitiator (Camphorquinone, CQ). The aim of the present work was to study the kinetics of polymerization of various composite mixtures (20-40-60-80mol%) of bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (BisGMA/TegDMA) containing either CQ or MAPO, based on real-time measurements and on the characterization of various post-cure characteristics. Polymerization kinetics were monitored by Fourier-transform near-infrared spectroscopy (FT-NIRS) and dielectric analysis (DEA). A range of postcure properties was also investigated. FT-NIRS and DEA proved complementary to follow the fast kinetics observed with both systems. Autodecceleration occurred after ≈1s irradiation for MAPO-composites and ≈5-10s for CQ-composites. Conversion decreased with increasing initial viscosity for both photoinitiating systems. However despite shorter light exposure (3s for MAPO vs 20s for CQ-composites), MAPO-composites yielded higher conversions for all co-monomer mixtures, except at 20mol% BisGMA, the less viscous material. MAPO systems were associated with increased amounts of trapped free radicals, improved flexural strength and modulus, and reduced free monomer release for all co-monomer ratios, except at 20mol% BisGMA. This work confirms the major influence of the initiation system both on the conversion and network cross-linking of highly-filled composites, and further highlights the advantages of using MAPO photoinitiating systems in highly-filled dimethacrylate-based composites provided that sufficient BisGMA content (>40mol%) and adapted light spectrum are used.
PloS one, 2015
In the aftermath of a major radiological accident, the medical management of overexposed individu... more In the aftermath of a major radiological accident, the medical management of overexposed individuals will rely on the determination of the dose of ionizing radiations absorbed by the victims. Because people in the general population do not possess conventional dosimeters, after the fact dose reconstruction methods are needed. Free radicals are induced by radiations in the tooth enamel of victims, in direct proportion to dose, and can be quantified using Electron Paramagnetic Resonance (EPR) spectrometry, a technique that was demonstrated to be very appropriate for mass triage. The presence of dimethacrylate based restorations on teeth can interfere with the dosimetric signal from the enamel, as free radicals could also be induced in the various composites used. The aim of the present study was to screen irradiated composites for a possible radiation-induced EPR signal, to characterize it, and evaluate a possible interference with the dosimetric signal of the enamel. We investigated ...
Journal of controlled release : official journal of the Controlled Release Society, Jan 28, 2015
Glioblastoma is the most frequent primary malignant brain tumor in adults. Despite treatments inc... more Glioblastoma is the most frequent primary malignant brain tumor in adults. Despite treatments including surgery, radiotherapy and chemotherapy by oral Temozolomide (TMZ), the prognosis of patients with glioblastoma remains very poor. We hypothesized that a polyethylene glycol dimethacrylate (PEG-DMA) injectable hydrogel would provide a sustained and local delivery of TMZ. The hydrogel photopolymerized rapidly (<2min) and presented a viscous modulus (≈10kPa). TMZ release kinetic presented two phases: a linear burst release of 45% of TMZ during the first 24h, followed by a logarithmic release of 20% over the first week. The in vivo tolerability study showed that the unloaded hydrogel did not induce apoptosis in mice brains nor increased microglial activation. In vivo, the anti-tumor efficacy of TMZ-hydrogel was evaluated on xenograft U87MG tumor-bearing nude mice. The tumor weight of mice treated with the photopolymerized TMZ hydrogel drastically decreased compared with all other g...
Dental Materials, 2014
New commercial tricalcium silicate based cements were elaborated to improve handling properties a... more New commercial tricalcium silicate based cements were elaborated to improve handling properties and setting time. The goals of the present work were: (i) to determine the composition of the new injectable and/or fast setting calcium silicate based cements, and (ii) to investigate the impact of the differences in composition on their setting kinetics. The materials considered were Angelus MTA™, Biodentine™, MM-MTA™, MTA-Caps™, and ProRoot MTA™ as control. Elemental composition of materials was studied by Inductively Coupled Plasma-Atomic Emission Spectroscopy and X-ray Energy Dispersive analysis, whereas phases in presence were analyzed by Micro-Raman spectroscopy and X-ray Diffraction analysis and cement surface by Scanning Electron Microscope. Setting kinetics was evaluated using rheometry. Elemental analysis revealed, for all cements, the presence of three major components: calcium, silicon and oxygen. Chlorine was detected in MM-MTA, MTA-Caps and Biodentine. Different radio-opacifiers were identified: bismuth oxide in ProRoot MTA, Angelus MTA and MM-MTA, zirconium oxide in Biodentine and calcium tungstate (CaWO4) in MTA-Caps. All cements were composed of di- and tri-calcium silicate, except Biodentine for which only the latter was detected. Major differences in setting kinetics were observed: a modulus of 8×10(8)Pa is reached after 12min for Biodentine, 150min for MM-MTA, 230min for Angelus MTA and 320min for ProRoot MTA. The maximum modulus reached by MTA-Caps was 7×10(8)Pa after 150min. Even if these cements possess some common compounds, major differences in their composition were observed between them, which directly influence their setting kinetics.
Objective: To examine the effect of dual wavelength light transmission and photoinitiator (PI) ab... more Objective: To examine the effect of dual wavelength light transmission and photoinitiator (PI) absorption on the curing extent through depth of light-activated resin-based composite materials Method: Two wavelengths centred at 400 and 470nm were measured on a MARC® Resin Calibrator (BlueLight analytics inc., Halifax, Canada) and adjusted to deliver approximately 1500 mW/cm2 to cure a variety of commercial and model resin composite formulations that either contained 1) CQ-amine, 2) TPO, or 3) CQ-amine/TPO PI systems. The total transmitted energy within the blue range (420-540 nm) and violet range (360-420 nm) was calculated as well as the percentage of light transmission. Raman spectroscopy was used to explore curing extent through depth. Result: Light transmission through commercial materials varied significantly between products (p<0.05) with considerable short wavelength absorption at 2mm depth for some materials. Experimental resins containing TPO exhibited significantly incre...
Regenerative medicine, 2015
Evaluation of survival, proliferation and neurodifferentiation of dental stem cells from the apic... more Evaluation of survival, proliferation and neurodifferentiation of dental stem cells from the apical papilla (SCAP) in fibrin hydrogels. We hypothesized that fibrin composition will influence cell behavior. Modulus, pore and fiber size were measured. SCAP in vitro viability, proliferation and neural differentiation, as well as in vivo proliferation and angiogenesis were studied. Hydrogel moduli were influenced by fibrin formulation but not hydrogel morphology, SCAP in vitro viability and proliferation. In total 60% of SCAP expressed PanNeurofilament in vitro without induction in Fibrinogen50-Thrombin10. SCAP proliferated when implanted in vivo and stimulated host endothelial cell infiltration. Fibrinogen30-Thrombin10 or Thrombin50 would be more favorable to in vitro SCAP viability and in vivo proliferation, while Fibrinogen 50-Thrombin50 would be more adapted to neurodifferentiation.
ABSTRACT Objectives: Exposure reciprocity law (ERL) promotes the common assumption that varying c... more ABSTRACT Objectives: Exposure reciprocity law (ERL) promotes the common assumption that varying combinations of curing irradiance and exposure time provide similar material properties for the same radiant exposure. This study aims to investigate the applicability of ERL to commercial flowable resin composites and their higher viscosity counterparts. Methods: A radiant exposure of 18J/cm2 using three different curing protocols (400mW/cm2 for 45s; 1500mW/cm2 for 12s; 3000mW/cm2 for 6s were used to polymerise various conventional restorative and low viscosity composite systems: Clearfil Majesty Posterior (CM-P) and Clearfil Majesty Flow (CM-F), Filtek Supreme Body (FS-P) and Filtek Supreme Flow (FS-F), Grandio (GR-P) and Grandio Flow (GR-F), Venus (VS-P) and Venus Flow (VS-F). Degree of conversion and polymerization kinetics were analysed using Fourier Transform near infrared spectroscopy in real-time for 70s. Results: Material 400 mW/cm2 for 45s 1500 mW/cm2 for 12s 3000 mW/cm2 for 6s DC (%) Rp max (s-1) Time to Rp max (s) DC (%) Rp max (s-1) Time to Rp max (s) DC (%) Rp max (s-1) Time to Rp max (s) CM-P 44 a 0.037 5.9 47 a 0.091 3.0 46 a 0.121 2.0 CM-F 64 a 0.037 5.9 65 a 0.077 3.9 61 a 0.075 2.9 FS-P 42 a 0.021 7.9 45 a 0.057 3.0 42 a 0.070 3.0 FS-F 62 a 0.029 10.6 62 a 0.052 6.9 59 a 0.075 4.9 GR-P 50 a 0.036 4.9 51 a 0.070 3.0 49 a 0.087 3.0 GR-F 56 a 0.022 11.8 49 b 0.038 5.9 35 c 0.043 4.9 VS-P 45 a 0.026 6.6 45 a 0.054 2.8 44 a 0.085 2.0 VS-F 65 a 0.023 14.8 60 b 0.043 8.6 46 c 0.055 5.8 Similar superscript letters across rows indicate no statistical significant difference (p&gt;0.05) Conclusions: Resin composites manufacturers accomplish lower material viscosity either by reducing the volume fraction of filler particles or by modification of the resin component. Flowable composite materials produced by decreasing resin matrix viscosity may not cure effectively using high irradiance and short exposure protocols.
ABSTRACT Objective: To compare the phenotype, the growth curve and the osteo- and chondrogenic di... more ABSTRACT Objective: To compare the phenotype, the growth curve and the osteo- and chondrogenic differentiation potential of mixed vs purified stem cells populations from the apical papilla (SCAPs); gingival fibroblasts (GFs) were used as control. Method: Four cell populations were considered: 1)mixed SCAPs (M-SCAPs); 2&amp;3)SCAPs purified by immunomagnetic separation based either on Stro-1 (P-SCAPs1), or on a combination of CD73, CD90 and CD105 (P-SCAPs2); 4)gingival fibroblasts (GFs). Each population was subcultured, and their growth curve determined. Their phenotype was characterized by flow cytometry using antibodies against CD29, CD31, CD34, CD90, CD105 and Stro-1. The cells were then cultured in osteo- and chondrogenic media during 25 days. Osteogenic and chondrogenic differentiation were evaluated respectively by alizarin red S and alcian blue staining. Result: All four cell populations had similar growth curves, were homogeneously positive to CD29, CD90 and CD105 (percentage of positive cells &gt;97% in all cases but P-SCAPs1 for CD90 – 91.5%), and negative to CD31, CD34 and Stro-1 (&lt;3% in all cases but GFs for CD34 – 7.5%). All cell populations were positive for alizarin red S, and all but GFs were positive for alcian blue. Conclusion: The present results question the specificity of certain markers considered to identify dental mesenchymal stem cells. The expression of Stro-1 was notably lost in P-SCAPs1, which however conserved their multi-differentiation potential. The rationale of sorting cells based on these markers is therefore called into question vs using a mixed population. Finally, the results suggest that GFs either contain a certain proportion of osteogenic progenitor cells, or that they intrinsically possess an osteogenic differentiation potential.
Dental materials : official publication of the Academy of Dental Materials, 2014
to complement our previous work by testing the null hypotheses that with short curing times and h... more to complement our previous work by testing the null hypotheses that with short curing times and high DC, TPO-based resin composites would exhibit (1) higher polymerization stresses and consequently display (2) higher temperature rise and (3) higher flexural modulus, flexural strength and hardness, compared to a conventional CQ-based experimental composite. Two experimental resin composites using either Lucirin-TPO or camphorquinone/DMAEMA as photoinitiators were prepared. Light curing was carried out using spectral outputs adapted to the absorption properties of each initiator. Different irradiation protocols were selected (0.5, 1, 3, 9 s at 500, 1000 and 2000 mW/cm(2) for Lucirin-TPO based composites and 20 or 40 s at 1000 mW/cm2 for Lucirin-TPO and camphorquinone-based composites). Degree of conversion (DC) was measured in real time by means of FT-NIR spectroscopy. Pulpal temperature rise (ΔT) was studied in a tooth model. Polymerization stress was monitored using the Bioman instr...
Dental Materials, 2014
Please cite this article in press as: Lambricht L, et al. The type and composition of alginate an... more Please cite this article in press as: Lambricht L, et al. The type and composition of alginate and hyaluronic-based hydrogels influence the viability of stem cells of the apical papilla. Dent Mater (2014), http://dx.
Journal of Endodontics, 2014
Introduction: Stem cells from the apical papilla (SCAP) are a population of mesenchymal stem cell... more Introduction: Stem cells from the apical papilla (SCAP) are a population of mesenchymal stem cells likely involved in regenerative endodontic procedures and have potential use as therapeutic agents in other tissues. In these situations, SCAP are exposed to hypoxic conditions either within a root canal devoid of an adequate blood supply or in a scaffold material immediately after implantation. However, the effect of hypoxia on SCAP proliferation and differentiation is largely unknown. Therefore, the objective of this study was to evaluate the effect of hypoxia on the fate of SCAP. Methods: SCAP were cultured under normoxia (21% O 2 ) or hypoxia (1% O 2 ) in basal or differentiation media. Cellular proliferation, gene expression, differentiation, and protein secretion were analyzed by live imaging, quantitative reverse-transcriptase polymerase chain reaction, cellular staining, and enzyme-linked immunosorbent assay, respectively. Results: Hypoxia had no effect on SCAP proliferation, but it evoked the up-regulation of genes specific for osteogenic differentiation (runtrelated transcription factor 2, alkaline phosphatase, and transforming growth factor-b1), neuronal differentiation ( 2 0 -3 0 -cyclic nucleotide 3 0 phosphodiesterase, SNAIL, neuronspecific enolase, glial cell-derived neurotrophic factor and neurotrophin 3), and angiogenesis (vascular endothelial growth factor A and B). Hypoxia also increased the sustained production of VEGFa by SCAP. Moreover, hypoxia augmented the neuronal differentiation of SCAP in the presence of differentiation exogenous factors as detected by the up-regulation of NSE, VEGFB, and GDNF and the expression of neuronal markers (PanF and NeuN). Conclusions: This study shows that hypoxia induces spontaneous differentiation of SCAP into osteogenic and neurogenic lineages while maintaining the release of the proangiogenic factor VEGFa. This highlights the potential of SCAP to promote pulp-dentin regeneration. Moreover, SCAP may represent potential therapeutic agents for neurodegenerative conditions because of their robust differentiation potential. (J Endod 2014;-:1-9)
PLoS ONE, 2013
In case of radiological accident, retrospective dosimetry is needed to reconstruct the absorbed d... more In case of radiological accident, retrospective dosimetry is needed to reconstruct the absorbed dose of overexposed individuals not wearing personal dosimeters at the onset of the incident. In such a situation, emergency mass triage will be required. In this context, it has been shown that Electron Paramagnetic Resonance (EPR) spectroscopy would be a rapid and sensitive method, on the field deployable system, allowing dose evaluation of a great number of people in a short time period. This methodology uses tooth enamel as a natural dosimeter. Ionising radiations create stable free radicals in the enamel, in a dose dependent manner, which can be detected by EPR directly in the mouth with an appropriate resonator. Teeth are often subject to restorations, currently made of synthetic dimethacrylate-based photopolymerizable composites.
Dental Materials, 2013
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Papers by Julian Leprince