Papers by Laurence Jordan
Journal of Dental Education, Nov 7, 2022
PARIS7-Odontologie (751062104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
Partial Confirmatory Factor Analysis. (DOC 28 kb)
Final French version of the P-CPQ questionnaire. (DOC 95 kb)
Endodontic Materials in Clinical Practice, 2021
Go to www.bda. org/library/studentservices to view our range of student services. Any questions, ... more Go to www.bda. org/library/studentservices to view our range of student services. Any questions, comments or suggestions for new titles? Email library@ bda.org or call 020 7563 4545. Further information Go to www.bda.org/library/student-services to view our range of student services. Any questions, comments or suggestions for new titles? Email [email protected] or call 020 7563 4545. Further information Go to www.bda.org/library/student-services to view our range of student services. Any questions, comments or suggestions for new titles? Email [email protected] or call 020 7563 4545. Further information Go to www.bda.org/library/student-services to view our range of student services. Any questions, comments or suggestions for new titles? Email [email protected] or call 020 7563 4545.
NiTi alloys have been used for many years in dentistry, especially in endodontology. High flexibi... more NiTi alloys have been used for many years in dentistry, especially in endodontology. High flexibility of NiTi alloys, compared to the stainless steel one, has made of NiTi the alloy of choice for the new generation of shaping files. Despite the improvement of file design, endodontic NiTi instruments are not perfect and the risk of fracture during use is still a concern. In recent years, several new thermomechanical processes have been developed to optimize the structure of NiTi alloys, in particular, the development of treatments named "M-wire", "R phase" and "CM wire" technologies. According to the manufacturers, these innovative treatments may improve the flexibility and the fatigue life of endodontic instruments. In the present work, new generations of these files have been characterized using DSC and bending tests and compared to a conventional NiTi file. The new endodontic instruments seem to improve the instrument properties. Hypotheses on the mic...
Journal of the Mechanical Behavior of Biomedical Materials, 2021
This study aimed at determining an optimum polymerization pressure for Polymer Infiltrated Cerami... more This study aimed at determining an optimum polymerization pressure for Polymer Infiltrated Ceramic Network (PICN) blocks by characterizing the conversion degree (DC) and the viscoelastic properties of experimental PICN blocks polymerized at 90 • C under various high pressures followed or not by post-cure treatment (PC). Near infrared analysis and dynamic mechanical analysis were used to characterize DC and viscoelastic properties of sixteen PICN: one control (thermo-cured) and fifteen experimental groups (one thermo-cured followed by PC and fourteen high pressure polymerized PICN, in the range of 50-350 MPa without and with PC). Conversion degree of high pressure polymerized PICN blocks without post curing displays an optimum between 100 and 150 MPa resulting in an improved E ′ and T g. Post curing induces a higher DC with a controversial effect on thermomechanical properties. The results suggested that 100-150 MPa without PC is an optimum polymerization parameter, resulting in PICN blocks with significantly better DC, T g , E'.
Journal of Dentofacial Anomalies and Orthodontics, 2015
Childhood obstructive sleep apnea syndrome (OSAS) affects 2% to 3% of the pediatric population. I... more Childhood obstructive sleep apnea syndrome (OSAS) affects 2% to 3% of the pediatric population. It is characterized by increased upper airway resistance due to pharyngeal narrowing, leading to episodic snoring, apnea or hypopnea. These events often cause intermittent hypoxia, hypercapnia and disordered sleep. Without treatment, the consequences may include 4 :-poor school performance (cognitive deficit);-behavioral disorder (hyperactivity, aggression, attention deficit);-cardiovascular impact (pulmonary hypertension, right cardiac insufficiency);-growth disorder.
BMC Oral Health, 2018
Background: The Parental-Caregivers Perceptions Questionnaire (P-CPQ) is a measure of parental/ca... more Background: The Parental-Caregivers Perceptions Questionnaire (P-CPQ) is a measure of parental/caregivers' perceptions of the impact of children's oral health on quality of life. The aim of the study was evaluate the psychometric properties of the French version of the P-CPQ. Method: The original P-CPQ was developed in English language and has 31 items divided into four sub-scales. This cross-sectional study used the translation-back translation method. The translated questionnaire was pretested on 14 parents-caregivers to obtain the final French version. The psychometric properties were tested on 142 parents/ caregivers of three clinical groups of children from 8 to 10 years old without dental/facial anomalies (presumed healthy), with oral-facial clefts and with oral-dental anomalies linked to a rare disease other than cleft, approached in the waiting room of the Centre of the Hospital Rothschild in Paris, France, where the children attended treatment. Internal consistency was assessed by Cronbach's alpha and test-retest reliability by Intra-class Correlation Coefficient (ICC). Construct validity was measured by correlations between the total scores and the global ratings of oral health and overall wellbeing, and tested using exploratory factor analysis (EFA) and the factorial structure was evaluated by the partial confirmatory factor analysis (PCFA). Discriminant validity was determined using Kruskall-Wallis test. Results: The mean (standard deviation) P-CPQ score was 18.73(18.79). Internal consistency was confirmed by a Cronbach alpha of 0.85. The test-retest reliability revealed that the responses to items were satisfactorily stable (ICC = 0.88). Construct validity was demonstrated by significant correlation coefficients between the total scale and the global ratings (r = 0.54 and 0.46; p < 0.001). Factor analysis with Principal Component Analysis extracted seven factors explaining 65.23% cumulative variance. Goodness-of-fit indices for partial confirmatory factor analysis were satisfactory for the 7-factors model of the French-PCPQ version. There were statistically significant differences between clinical groups regarding the total scale, thus demonstrating discriminant validity (p < 0.001). Conclusion: This French P-CPQ version showed reliability and validity comparable to the previous versions. However, the cross-cultural structure of the subscales should be further evaluated.
Actualités Odonto-Stomatologiques, 2017
Restaurations coronoradiculaires des dents dépulpées par endocouronnes Coronadicular restorations... more Restaurations coronoradiculaires des dents dépulpées par endocouronnes Coronadicular restorations of teeth pulled by endocourons AOS n° 283-2017 Publié par EDP Sciences et disponible sur le site
Scripta Metallurgica et Materialia, 1992
Materials Science and Engineering: A, 2014
Mechanical properties of the Ti 50-Ni 47-Co 3 (at%) strips produced by twin-roll casting are anal... more Mechanical properties of the Ti 50-Ni 47-Co 3 (at%) strips produced by twin-roll casting are analyzed, focusing on the maximum recoverable strain obtained by inducing the martensitic transformation under constant tensile load. The recoverable strain achieves a value close to 5.5% for a load of $ 120 MPa. The microstructure shows a typical cellular solidification structure, where the austenite grains tend to a columnar array morphology with strong f100g B2 fiber texture aligned with ND (perpendicular to the strip surface). On the basis of the measured texture, the maximum B2-B19 0 transformation strain was estimated at 5.6%, using a Sachs-type upper bound model, which averages the most favorable martensite variants in each grain, disregarding interactions between them. The agreement between the measured maximum recoverable strain and the model 0 s outcome is ascribed to special properties of Ti-Ni alloys, which allow them to overcome incompatibilities in shape changes of transforming grains in this particular polycrystalline environment.
Journal of Alloys and Compounds, 1994
Thermal cycling carried out on Ni-Ti-X alloys leads to a stabilization of thermal properties (wel... more Thermal cycling carried out on Ni-Ti-X alloys leads to a stabilization of thermal properties (well-defined transformation temperatures) and mechanical characteristics (elastic modulus).
Le Journal de Physique IV, 2001
Endodontic treatments consist to eliminate the vascular nervous system of the tooth. The objectiv... more Endodontic treatments consist to eliminate the vascular nervous system of the tooth. The objectives of this treatment are adequate cleaning and shaping the root canals of the tooth. The endodontic treatment is essential to the success of prosthetics therapy and the lifetime of the tooth. The difficulties of endodontic treatments lie in the abruptness of canal curvature. Ni-Ti endodontic instruments were introduced to facilitate instrumentation of curved canals. They are superelastic and flex far more than stainless-steel instruments. Despite the increased flexibility we can observe unexpected fractures of these Ni-Ti files. The purpose of this work is to understand the process history on fracture life. Our results are based on microstructural and mechanical investigations of Ni-Ti engine-driven rotary files: X-ray diffraction, SEM, DSC, microhardness and bending tests. Thus, and as we expected, endodontic files are very work-hardened: there is a high density of defects in the alloy, which will impede the phase transformation. DSC : the phase transformation A/R-Phase is predominant, the martensitic transformation is difficult to observe. The microvickers hardness confirms these observations (dislocations and precipitates). The X-rays show that the experimental peaks are broad, which is typical of a distorted lattice. Morover, machining resulted in the work hardening of files. Some thermal treatments are involved in promoting some changes in the mechanical properties and transformation characteristics. Annealing around 400°C shows good results : the recovery allows a compromise between an adequate density of defects to see the R-Phase germination and a low density to limit the brittleness of these instruments. The surface state of the endodontic files is an important factor for failures and fractures initiation. In these applications, it is very critical to predict the service life based on the theoretical modeling.
Le Journal de Physique IV, 1995
Structural changes with cooling and heating of Ni-Ti alloys involve three phases : austenite, R-p... more Structural changes with cooling and heating of Ni-Ti alloys involve three phases : austenite, R-phase and martensite. The corresponding transformation sequences are often studied by techniques such as differential scanning calorimetry and internal friction. Structural transformation between any two phases is identified in these measurements by a peak in the studied property versus temperature plot. On this basis, the evidence of two transformations, austenite-+ R-phase and R-phase-, martensite, have been established in the literature. In spite of exhibiting these two transitions on cooling, the reverse transformation from martensite, on heating, can be associated with one or two peaks. The exact interpretation of this behaviour thus poses an open question. This is attended to in this communication and the possible transformation sequences will be discussed with qualitative model. The data for the present investigation have been obtained on NisoTiso and Ni47Ti5~Co3 alloys.
Le Journal de Physique IV, 1995
In the present work we report some results concerning the evolutions of transformation temperatur... more In the present work we report some results concerning the evolutions of transformation temperatures and microstructure during thermal cycling in Ti-47%Ni-3% Co (atomic percent). In the case of hulk material (obtained by a conventional solidification method) high amounts of dislocations l'onn during cycling, which produce a considerable evolution of the transformation temperatures (up LO-40K). wl~ile in mcltspun material containing a dispersion of fine precipitates, the formation 01' dislocations during thermal cycling is highly reduced, giving rise to stable transformation temperatures. The dislocation characteristics have been analysed by means of two-beam condition observations as well as the Large Angle Convergent Beam Electron Diffraction technique. Some energetical considerations concerning the dislocations are pointed out to interpret the evolution of transformation temperatures.
Le Journal de Physique IV, 1994
RESUME Deux alliages à mémoire de forme, NiTi et Ni47Ti50Co3 ont fait l'objet d'une étude compara... more RESUME Deux alliages à mémoire de forme, NiTi et Ni47Ti50Co3 ont fait l'objet d'une étude comparative vis à vis des transformations structurales intervenant sous l'effet de la température. Les résultats obtenus par calorimétrie différentielle à balayage (DSC) et par mesures de frottement intérieur (FI) permettent de définir de façon certaine la chronologie des transformations : "austéniteW+phase-R+"martensiteW au refroidissement et martensite+phase-R-austénite au chauffage, lorsque les hystérésis des transformations le permettent. Des expériences de cyclages thermiques montrent qu'il peut y avoir une inversion apparente dans le séquence des transformations au chauffage mais cela résulte d'une transformation martensitique directe partielle. La différence majeure entre ces deux alliages est le décalage en température, des hystérésis et donc des transformations M t> R et R H A.
American Journal of Medical Genetics Part A, 2009
An international group of clinicians working in the field of dysmorphology has initiated the stan... more An international group of clinicians working in the field of dysmorphology has initiated the standardization of terms used to describe human morphology. The goals are to standardize these terms and reach consensus regarding their definitions. In this way, we will increase the utility of descriptions of the human phenotype and facilitate reliable comparisons of findings among patients. Discussions with other workers in dysmorphology and related fields, such as developmental biology and molecular genetics, will becomemore precise. Here we introduce the anatomy of the male and female genitalia, and define and illustrate the terms that describe the major characteristics of these body regions.
Frontiers in Materials
The objective of this study was to develop a thermo-mechanical strategy to create a radial elasti... more The objective of this study was to develop a thermo-mechanical strategy to create a radial elasticity gradient in a β metastable Ti-Nb-Zr alloy, and to characterize it in terms of microstructural and mechanical properties. A first investigation was conducted on thin samples of Ti-20Nb-6Zr (at.%) submitted to various thermo-mechanical treatments. Microstructure-properties relationships and elastic variability of this alloy were determined performing uniaxial tensile tests, X-ray diffraction and scanning and transmission electron microscopies. Based on these preliminary results, mechanical deformation was identified as a potential way to lower the elastic modulus of the alloy. In order to create elastically graded pieces, shot-peening was therefore carried out on thicker samples to engender surface deformation. In this second part of the work, local mechanical properties were evaluated by instrumented micro-indentation. Experimental observations demonstrated that shot-peening enabled ...
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Papers by Laurence Jordan