Self-perceived educational needs of junior assistant professors in Conservative Dentistry and Endodontics in France.

INTRODUCTION: Academic dental educators play a major role in training future dentists. They help students to develop medical knowledge and behavioural skills that improve the quality and rigor of their future practice. Therefore, their experience and knowledge are critical to ensure effective learning. However, a French national workshop revealed that most junior assistant professors lack educational skills at the beginning of their career. The aim of this study was to assess educational training needs of junior assistant professors in the Department of Conservative Dentistry and Endodontics. MATERIALS AND METHODS: An electronic survey was sent to junior assistant professors belonging to Departments of Conservative Dentistry and Endodontics within the 16 French dental schools in 2016. This survey was designed to collect data regarding their motivations, teaching expertise and interest in pedagogy. RESULTS: Sixty of the 69 junior educators turned in their answers, which represents a response rate of 87%. About 86.7% of respondents cited their attraction to teaching as one of the main reasons behind their application. The major difficulty encountered by junior faculty was related to course preparation. Only 15% had received educational training despite the fact that 98.3% were convinced of the usefulness of such a training for junior teachers. CONCLUSION: This study identified the motivations and difficulties encountered by junior assistant professors. This collection of educational needs should be considered when planning a national programme for educational training of dental faculty that will promote the acquisition of teaching skills and improve the education of dental students.

Fas-dependent tissue turnover is implicated in tumor cell clearance.

The apoptosis-inducing Fas receptor has been shown to be down-regulated in various types of tumors, while its ligand (FasL) appears to be frequently up-regulated. Here we provide evidence that there is a strong selective pressure in vivo against Fas-expressing, tumorigenic NIH3T3 cells, favoring survival, proliferation and eventually tumor formation by Fas-negative cells. Importantly, re-expression of Fas in these cells results in either the complete abolishment of tumor development, or in a significant extenuation of the latency period of tumor outgrowth. In addition, we found that environmental conditions which prevail during tumorigenesis, such as limiting amounts of survival factors and the lack of cell adhesion, are markedly sensitizing tumor cells to Fas-mediated suicide. Our data suggest that in addition to T cell-mediated immune responses, mechanisms of Fas-dependent tissue turnover are also centrally implicated in tumor cell clearance.

Involvement of the Tpl-2/cot oncogene in MMTV tumorigenesis.

We report for the first time a relationship between the Tpl-2/cot oncogene and Mouse Mammary Tumor Virus (MMTV) associated transformation of mammary gland cells. A sub-genomic library generated from a primary mammary gland tumor yielded a novel MMTV integration site which disrupted the Tpl-2/cot proto-oncogene between exons 7 and 8. Comparison of a cell line derived from normal mammary gland (comma-D) and a cell line established from an MMTV induced mammary tumor (GR) demonstrated similar rearrangements within Tpl-2/cot for the GR cells but not in the comma-D cells. These rearrangements in the cell line were accompanied by an increase in the level of Tpl-2/cot specific mRNA. This data suggests that Tpl-2/cot expression may be important in epithelial cell transformation or tumor progression.

Rate and growth pattern of radicular apical third tissue apposition in tetracycline-labeled rats.

The aim of this in vivo study was to find a way to conduct qualitative and quantitative evaluations of radicular apical third apposition in rats. Twenty rats were injected intraperitoneally with tetracycline at weight-adjusted doses. Mesio-distal sections of the first mandibular molar regions were prepared. The 60 to 80 microns sections were examined by fluoromicroscopy using reflected light. Visible lines of fluorescence could be seen in the radicular dentin and the cementum. Each line corresponded to one injection. It was possible to define two periods: the first, from day 22 to day 59, corresponded to the immature tooth; the second, from day 59 to day 101, to the mature tooth. During period 1, the mean speed of radicular lengthening by cemental and dentinal apposition was 23.95 microns/24 h. The increase in mesio-distal diameter by cemental apposition was 12.15 microns/24 h. During period 2, the mean speed of radicular lengthening by cemental apposition was 8.23 microns/24 h. It is therefore possible to use this method to conduct quantitative and qualitative evaluations of apical morphogenesis by cemental and dentinal apposition.

Effects of the Nd:YAP laser on coronal restorative materials: implications for endodontic retreatment.

With new wavelengths that allow light transmission by optical fibers, the laser is now often used in endodontics either during treatment or retreatment. The aims of this study were to (i) specify the effects of laser irradiation on restorative materials in terms of topographic effects and (ii) describe different protocols for the first steps of retreatment. The laser used in this study was an optical fiber Nd:YAP (Lokki dt, Vienne, France) with a wavelength of 1.34 microns. Samples of the following restorative materials were prepared: amalgam, composite, permanent and temporary cements, and prosthodontic alloy. The handpiece of the Nd:YAP laser was fixed perpendicular to the surface of the different preparations. All trials were performed with the fiber tip either in contact with or at a distance of 2 mm from the material. The surface effects in all cases were (i) the creation of craters in the center of the lased areas, (ii) a border of fusion material at the edge of the craters, and (iii) cracks or fractures at a distance from the target areas. For the cements, amalgam and composite, the effects included a projection of material from the center to the edge of the lased area and/or the apparent photovolatization of light particles. For all materials the laser induced deeper absorption in the areas of direct contact than when it was held at a distance. This suggests that the fiber should be in contact with the restorative material for lasing in the straight part of the canal when the objective is either to pass through the material or alongside it between material and tooth. If the practitioner cannot determine the direction of the curve of the canal, lasing should be performed at a distance to weaken the material and thus permit more efficient use of an ultrasonic device. Lasing should in all cases be performed under close X-ray monitoring. Provided that sufficient caution is used, the laser may be helpful in removing restorative materials during retreatment.

Effects of different cryoprotectants and carbohydrates on freezing of matured and unmatured bovine oocytes.

Cumulus cell-enclosed bovine oocytes in germinal vesicle (GV) and in metaphase II (MII) stages were cryopreserved. Different concentrations (1 M; 1.5 M) of various cryoprotectants (glycerol, PROH, DMSO) were tested. After thawing, the oocytes were exposed to various carbohydrates (sucrose, lactose, trehalose) at a concentration of 0.1 M and 0.25 M for cryoprotectant removal. Developmental capacity of the frozen-thawed oocytes was studied by in vitro maturation, fertilization and culture. We found no difference in subsequent development using glycerol or PROH for GV and MII oocytes. The DMSO treatment led to significantly better cleavage and development up to 4-cell stage in MII oocytes. Development beyond the 8-cell stage was obtained only when unmatured oocytes were frozen. No difference in the efficiency of the 3 cryoprotectants was detected in MII oocytes. However, in GV oocytes, glycerol and PROH yielded significantly better cleavage and 4-cell rate compared to DMSO (P<0.001). Influence of the concentration of a cryoprotectant on development was not observed in GV or MII oocytes. Among the 3 cryoprotectants, DMSO was less suitable, at both concentrations, than PROH and glycerol for the development of 6- to 8-cell stage embryos in the GV group. In the MII group, 1.5 M DMSO was as efficient as PROH and as glycerol at a 1.5-M concentration, and it was more efficient than 1 M glycerol. The use of carbohydrates during rehydration did not render a beneficial effect at either of the 2 concentrations, and when no carbohydrates were used in the MII group the oocytes cleaved better than GV oocytes.

Comparison of aggregation and injection techniques in producing chimeras with embryonic stem cells in mice.

We analyzed embryonic stem cell lines for their capacity to produce aggregation chimeras with diploid or developmentally compromised tetraploid embryos. Descendants of embryonic stem cells which contributed to midgestation fetuses at high levels were capable of supporting fetal development also with tetraploid partners. Different numbers of embryonic stem cells were introduced into diploid and tetraploid morulae as well as into blastocysts by microinjection. There were no differences in the frequency of embryonic stem cell-containing fetuses when comparing aggregation or injection into morulae versus blastocysts. However, the distribution pattern of embryonic stem cell derivatives in chimeric fetuses suggested that pre-compaction embryos are more suitable for generating fetuses with high embryonic stem cell contribution. Injection of embryonic stem cells into tetraploid embryos showed that completely embryonic stem cell-derived fetuses can also be produced by this technique. Totally embryonic stem cell derived fetuses were observed in each group, when embryonic stem cells were injected into diploid embryos. However, the rate of chimeras and chimerism was lower when 1 or 3 embryonic stem cells were used versus 8 or 15 cells. This suggests that the number of embryonic stem cells introduced might play a role in the colonization ability.

Shaping ability of two rotary instruments in simulated canals: stainless steel ENDOflash and nickel-titanium HERO Shaper.

AIM: To compare the shaping ability of two rotary instruments in simulated curved canals: stainless steel ENDOflash Files (KaVo, Biberach, Germany) and the recently introduced nickel-titanium HERO Shaper instruments (Micro-Mega, Besançon, France). METHODOLOGY: Simulated root canals with 35 degree curves in resin blocks were prepared to size 30, .04 taper (HERO Shaper) using a crowndown technique or size 30, .02 taper (ENDOflash) using a rotary motion and a rotation speed of 400 or 250 rpm respectively. In both groups, irrigation was performed with 1 mL distilled water after each instrument size and Glyde (Dentsply Maillefer, Ballaigues, Switzerland) were used. Canals (n = 17 per group) were scanned before, during and after preparation. The assessment of preparation shape was carried out with a computer image analysis program. Material removal was measured at seven points beginning 1 mm from the end-point of the canal. Statistical analysis was performed using Wilcoxon's test and Fisher's exact test (P < 0.05). RESULTS: No instrument fractures, apical blockage or loss of working length (WL) occurred. More zips (10 vs. 4) and more strippings (17 vs. 0) were created with ENDOflash compared with the HERO Shaper. There were significant differences in terms of the amount of resin removed on the inner wall of the curvature obtained with the two instruments (P < 0.0001). On average, HERO Shaper instruments removed material more evenly on the outer and inner wall of the curvature. Considering the different points of measurement, there were significant differences between the two systems both on the inner and outer walls at WL-1, 2, 5 and 6 mm (P < 0.05). The HERO Shaper had a more centred enlargement compared with the ENDOflash. CONCLUSIONS: Stainless steel rotary ENDOflash instruments did not perform as well as HERO Shaper instruments and created an increased risk of root canal transportation. Nickel-titanium rotary HERO Shaper instruments maintained the original curvature significantly better.

[Fluoromicroscopy]. / La fluoromicroscopie.

The fluorescence is a photoluminescent phenomena consisting in the emission of light under the influence of a light wave excitation. Two types of fluorescence exist: the primary fluorescence (natural) and the secondary (induced by a fluorochrome) The fluoromicroscope is composed of two parts. One of which, unspecific, consists in the classical optical system of the photonic microscopy. The other part, specific, consists in a source of light at a high mercurial pressure and a double filtration system of excitation and pause. There are many applications of this technique. In odontology, it is frequently used for the study of apposition in calcified tissues after their labelling by injection of a fluorochrome.

[Obturation of curved canals: in vitro study of lateral compaction]. / Obturation des canaux courbes: étude in vitro du compactage latéral.

The instrumentation and filling of teeth with curved canals are always difficult, therefore, the current study indicates solutions to problems encountered while preparing curved canals. The gutta condensation techniques and their ability to seal curved canals are also discussed. This study uses endodontic simulators to show the incidence of protocols and instrumentation on the ability of the lateral condensation technique to fill curved canals. This study, also, evaluate the lateral condensation technique combined with the thermomechanical in filling curved canals.

Simultaneous genotyping of sex and kappa-casein of bovine in vitro fertilized embryos by the PCR technique.

Sex and the kappa-casein genotype of in vitro produced cattle demiembryos was identified by simultaneous PCR-genotyping using polymorphic sites in ZFY/ZFX and kappa-casein genes. We obtained PCR products of 530 bp (kappa-casein) and of 445/447 bp (sex). Sex and the two kappa-casein alleles could be identified after digestion of the PCR products with Pstl and simultaneous separation of the restriction fragments on one step, allowing a rapid and efficient analyses of embryos.

Liposome-mediated DNA uptake by sperm cells.

To investigate the potential use of sperm cells as vectors to transfer exogenous DNA via the fertilization of oocytes into the germ line of mice, we have used liposomes to transfect DNA into the sperm head. Although the DNA transfer into sperm mediated by liposomes was very efficient and no obvious reduction in the fertilization frequency of oocytes could be detected, we were unable to generate transgenic mice by this method.

Effect of calcium hydroxide form and placement on root dentine pH.

AIM: The aim of this study was to measure variations in dentinal pH following the placement of various forms of calcium hydroxide in either the root canal or the pulp chamber. METHODOLOGY: Extracted single-rooted human teeth were prepared, and the root canals instrumented using a conventional technique. Three cavities were drilled through the root dentine to within 1 mm of the canal wall at the cervical, middle and apical thirds. A total of 125 teeth were randomly divided into five groups; group 1: pure aqueous calcium hydroxide paste (calcium hydroxide/distilled water solution) was placed in the root canal; group 2: the same aqueous calcium hydroxide paste was placed in the pulp chamber; group 3: Hycal, a new form of calcium hydroxide paste, was placed in the pulp chamber; group 4: calcium hydroxide gutta-percha points were placed in the root canal; group 5: control group, wet canal (distilled water) without medication. The access cavities and apical ends were sealed, and the teeth were placed in individual vials containing phosphate-buffered saline, and stored at 37 degrees C. The pH was measured in the dentinal cavities at 8 h and at 1, 2, 3, 7, 14, and 21 days using a calibrated microelectrode. RESULTS: At 8 h and 1, 2, and 3 days, the highest pH values were obtained when the aqueous calcium hydroxide paste was placed in the pulp chamber. At 7 days, the pH had increased in the Hycal group without being significantly different from the aqueous calcium hydroxide paste placed either in the root canal or in the pulp chamber. At 14 days, Hycal( had the highest pH values (pH 10.65); however, at 21 days no significant difference was noted amongst these first three groups. Control group values ranged from 7.88 to 8.60; the pH created by the calcium hydroxide gutta-percha points was lower than for the control group. Whatever the product or placement location, cervical pH was similar to middle pH, and greater than apical. However, there was no significant difference between the three when all groups were combined. Overall, aqueous calcium hydroxide paste placed in the pulp chamber provided the highest pH values during the experiment, except at day 14. The aqueous calcium hydroxide paste placed in the root canal or Hycal had similar values at days 7 and 21. CONCLUSIONS: Under the conditions of this study, an aqueous calcium hydroxide paste placed in the pulp chamber increased dentinal pH more than the other techniques. The pH of dentine is affected by the form of calcium hydroxide used.

[A more efficient lateral condensation]. / Pour un compactage latéral plus efficace.

Advantages and inconvenients of the lateral condensation technique are reviewed in this paper. Different ways to gain more efficient lateral condensation are studied: plugger and gutta-percha points selection and adaptation, combination with thermomecanical technique or assistance by ultrasonic or thermal systems. The study of these various methods and combinations leads to the concept of an thermolateral-assisted condensation.

Variation of the growth hormone gene in ryr 1 genotyped Austrian pig breeds.

SUMMARY: Polymorphism in the second intron of the porcine growth hormone gene of 273 Austrian Landrace and 81 Austrian Edelschwein pigs was investigated with a PCR-RFLP-technique. Results showed significantly different genotype patterns between the two breeds. The frequency of the Hae II(-) allele was significantly (P < 0,001) higher in the landrace than in the Edelschwein population (0,83 and 0,47 resp.). The Msp I(+) allele was predominant in both breeds but signifanctly higher in the Landrace (0,98 versus 0,69; P < 0,01). Analyses the Hae II/Msp I locus combination revealed also in breed specific difference. In the Landrace a very low interaction was found between the Hae II and ryr 1 locus, and between Msp I and ryr 1 locus (c. c. = 0,181 and 0,186 resp.). The correlation was slightly stronger (c. c. = 0,266) between the ryr 1 and Hae II/Msp I genotypes. No correlation was detected among the three loci in the Edelschwein population. ZUSAMMENFASSUNG: Variabilität des Somatotropin Gens in österreichischen Schweinerassen genotypisiert hinsicbtlich ryr 1 An 273 Österreichischen Landrasse Schweinen und 81 Österreichischen Edelschweinen wurde der Polymorphismus am zweiten Intron des Schweinewachstumshormons mittels PCR-RFLP-Technik untersucht. Genotypen-und Genfrequenzen waren zwischen den beiden Rassen signifikant verschie- den. Die Hae II(-) Allelfrequenz war bei den Landrassetieren signifikant höher (P < 0,001) als bei den Edelschweinen (0,83 bzw. 0,47). In beiden Rassen überwiegte das Msp I(+) Allel, das aber signifikant öfters bei der Landrasse auftrat (0,98 bzw. 0,69; P < 0,01). Die Verteilung der Locuskombination von Hae II/Msp I zwischen den beiden Rassen war ebenfalls unterschiedlich. Bei der Landrasse konnte nur ein sehr geringer Zusammenhang zwischen dem Hae II und ryr 1 Locus (c. c. = 0,181 bzw. 0,186) und auch zwischen dem Msp I und ryr 1 Locus festgestellt werden. Die Korrelation zwischen dem ryr 1 und Hae II/Msp I Genotyp war geringfügig größ;er (c. c. = 0,266). Bei den Edelschweinen konnte kein Zusammenhang zwischen den drei untersuchten Loci festgestellt werden.

TGF-beta1 and Ha-Ras collaborate in modulating the phenotypic plasticity and invasiveness of epithelial tumor cells.

Metastasis of epithelial tumor cells can be associated with the acquisition of fibroblastoid features and the ability to invade stroma and blood vessels. Using matched in vivo and in vitro culture systems employing fully polarized, mammary epithelial cells, we report here that TGF-beta1 brings about these changes in Ras-transformed cells but not in normal cells. When grown in collagen gels in the absence of TGF-beta, both normal and Ras-transformed mammary epithelial cells form organ-like structures in which the cells maintain their epithelial characteristics. Under these conditions, treatment of normal cells with TGF-beta results in growth arrest. The same treatment renders Ras-transformed epithelial cells fibroblastoid, invasive, and resistant to growth inhibition by TGF-beta. After this epithelial-fibroblastoid conversion, the Ras-transformed cells start to secrete TGF-beta themselves, leading to autocrine maintenance of the invasive phenotype and recruitment of additional cells to become fibroblastoid and invasive. More important, this cooperation of activated Ha-Ras with TGF-beta1 is operative during in vivo tumorigenesis and, as in wound healing processes, is dependent on epithelial-stromal interactions.

Oncogenic Ras inhibits Fas ligand-mediated apoptosis by downregulating the expression of Fas.

Tumor growth is the result of deregulated tissue homeostasis which is maintained through the delicate balance of cell growth and apoptosis. One of the most efficient inducers of apoptosis is the death receptor Fas. We report here that oncogenic Ras (H-Ras) downregulates Fas expression and renders cells of fibroblastic and epitheloid origin resistant to Fas ligand-induced apoptosis. In Ras-transformed cells, Fas mRNA is absent. Inhibition of DNA methylation restores Fas expression. H-Ras signals via the PI 3-kinase pathway to downregulate Fas, suggesting that the known anti-apoptotic effect of the downstream PKB/Akt kinase may be mediated, at least in part, by the repression of Fas expression. Thus, the oncogenic potential of H-ras may reside on its capacity not only to promote cellular proliferation, but also to simultaneously inhibit Fas-triggered apoptosis.

Socio-economic and schooling status of dental undergraduates from six French universities.

OBJECTIVES: The aim of this study was to evaluate the socio-economic status of French undergraduate dental students. METHODS: A 46-item questionnaire was completed by the dental students of six universities between 1992 and 1995. Subjects related to family background, housing, schooling, income, expenditure and participation in student life were investigated. RESULTS: A total of 1192 out of 1207 questionnaires were returned. Both genders had equal access to dental training. The average overall cost of the four last years of the dental course was 30,302 French francs and varied greatly between faculties, as did the number of hours spent at the faculty for lectures, tutorials and practicals, and clinical work. Overall, the majority of students came from a well off social background, and had a relatively high quality of life while a small minority received no support from their families. Thirty-four per cent of students had never worked. One third of students smoked and one third regularly consumed medication of some sort. A third did not participate in any sport. Only 25% students bought dental text books and 42% of the students reported using the library regularly. CONCLUSIONS: This study offers an accurate description of the socio-economic status of French dental students that could be used as a reference for comparable studies in other European countries.