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.

Investigation of the Actinobacillus actinomycetemcomitans genome by pulsed field gel electrophoresis.

Pulsed field gel electrophoresis was used to investigate nineteen strains of Actinobacillus actinomycetemcomitans. The genome was found to contain a single chromosome whose size we estimate to be 2300 kb from the sum of restriction fragments generated with rare cutting endonucleases. We detected the presence of large plasmids with sizes ranging from 35 to 300 kb. In some strains, extrachromosomal elements constitute over 20% of the total genome. Comparison of the profiles of ApaI digests of the 19 strains showed a high degree of polymorphism with 13 different profiles, providing a new tool for epidemiological studies.

An evaluation of the bactericidal effect of the Nd:YAP laser.

The aim of this in vitro study was to compare the efficacy of a classical irrigant with that of a laser in disinfecting a contaminated root canal. Thirty canals of extracted single-root teeth were prepared with files to size #20. The teeth were sterilized with Germispad (Spad, France) for 30 min and then inoculated with Streptococcus mitis ATCC 33399. By randomization, the teeth were divided into six groups of five teeth each. In the first group, teeth were neither inoculated nor prepared. This was the sterility control group (1). In the second group (2) teeth were inoculated without any preparation: as positive controls. The third group was inoculated and then hand-instrumented with files to size #30 with 5.25% NaOCl as irrigant. This was the hand instrumentation group. The other groups were prepared with hand instrumentation with files to size #30, using sterile water as an irrigant, and the canal was then lased with different frequencies as follows: group 4, frequency of 5 Hz and power of 260 mJ; group 5, frequency of 10 Hz and power of 310 mJ; and group 6, frequency of 30 Hz and power of 300 mJ. After experimentation, the residual colonies were counted. The results indicated that (i) the treatment with NaOCl and manual instrumentation effectively inhibited the growth of Streptococcus mitis ATCC 33399; and (ii) the antibacterial effect of the Nd:YAP laser depended on the frequency. Only a frequency of 30 Hz of the Nd:YAP laser inhibited the growth of Streptococcus mitis ATCC 333999.

Bacterial leakage in endodontics: an improved method for quantification.

A new method for studying leakage of root fillings using the bacterium Pseudomonas fluorescens ATCC 13525 is described. The presence of the microorganism is detected by fluorimetry and can thus be used to measure the depth of penetration from the root apex toward the crown of the tooth. This system, applied to a number of methods of root canal filling, showed that procedures involving compaction of the gutta-percha gave a more effective seal than the use of a paste sealer with uncondensed gutta-percha. There was no statistically significant difference between the leakage results from the lateral, vertical, and thermomechanical condensed techniques.

An in vivo recording of variations in oral temperature during meals: a pilot study.

Thermocycling is often used in the in vitro evaluation of marginal leakage of dental restorations. The in vivo temperatures occurring during meals were recorded at different surfaces of restored teeth, to compare the variations in temperature with laboratory thermocycling. Temperatures were recorded with thermocouples at three different sites: (1) on the facial surface of a silver amalgam restoration, (2) at the base of a silver amalgam restoration and (3) within the root canal. The maximal temperature differences between upper and lower extremes were 29.6 degrees C at the base of a coronal restoration, 27.1 degrees C at the facial surface, and 11.8 degrees C within the root canal. A practical regimen for these experiments is suggested in the light of these ranges because many thermocycling regimens in in vitro studies appear extreme or unrealistic.

Stereochemical structure characterization of dental gutta-percha.

Natural gutta-percha is well known for its mechanical properties which derive from its particular stereochemical 1-4 trans structure. The gutta-percha contained in the various commercially available points is made of natural gutta-percha which has undergone a heating process to allow inclusion of the other elements found in its composition, especially a nonspecified coloring agent. The purpose of this study was to confirm that the stereochemical 1-4 trans structure contained in commercial points is identical to that of natural gutta-percha and that it has not been altered by the heating process inherent to its fabrication. Furthermore, we wanted to identify the coloring agent also included in its composition. Samples of commercial gutta-percha points were studied using nuclear magnetic resonance spectral analysis and compared with that of natural gutta-percha. Our results show that both natural and commercial gutta-percha mainly have a 1-4 trans stereochemical structure and that the coloring agent is erythrosin.

Thermomechanical analysis of dental gutta-percha.

Samples of three common commercial gutta-percha endodontic filling points (Hygienic, Mynol, and Maillefer Pink) and a sample of natural gutta-percha were submitted to thermomechanical analysis under pressures ranging from 0.01 to 0.2 N. Samples of Mynol and Maillefer filling points were thermally treated and then submitted to thermomechanical analysis in parallel with differential scanning calorimetric analysis. The results show that thermomechanical analysis gives results distinct from those obtained by classic dilatometry and that it is a technique well suited to the study of the thermoplastic properties of gutta-percha. An analysis of the results shows that the amount of the inorganic component used in a commercially available endodontic point has a strong influence on its thermomechanical properties. Thermodynamical properties and the "thermal history" of the gutta-percha are also important. Both temperature and force should be controlled in order to assess the thermomechanical properties of endodontic filling points, while the latter have not yet been codified in clinical procedures.

Dental gutta-percha: chemical composition, X-ray identification, enthalpic studies, and clinical implications.

The purpose of this investigation was to determine the chemical composition, confirmed on X-ray diffraction analysis, of some commercially available dental gutta-percha cones. In addition, their plasticity in response to temperature variations was studied by differential scanning calorimetry. Great chemical heterogeneity was found among gutta-percha cones of different origin as well as within the same brand between small and large sizes. Barium sulfate determined radiopacity, zinc oxide influenced the inherent plasticity, while an excess of gutta-percha seemed to produce brittle gutta-percha cones which were unusable in clinical practice. Differential scanning calorimetry measured accurately the thermal ranges within which gutta-percha cones show a maximal plasticity without any chemical damage. It was also possible to define the thermal optimums for heat carriers, which could lead to more appropriate use of these instruments in endodontic therapy, whatever method may be used.

[An epidemiologic study of the orodental status of 6-15-year-old children in the Languedoc-Roussillon region]. / Etude épidémiologique de l'état bucco-dentaire des enfants âgés de 6 à 15 ans de la région Languedoc-Roussillon.

An epidemiological study of a representative sample of 702 children, aged 6 to 15 years, was conducted in the Languedoc-Roussillon region composed of the departments of Aude, Gard, Hérault, Lozère and Pyrénées Orientales. The mean DMFT at 12 years of 4.21 was always higher in girls (5.13) than in boys (3.46) of the same age. The DMFT was lower in urban areas than in rural zones, but the difference was only statistically significant at 11 years of age. The pits and fissures were the most caries-affected sites (67%) followed by proximal (22%) and smooth surfaces (11%). The plaque index varied from 0.94 to 1.23 between 6 and 15 years. The calculus index increased with age from 0.20 at 6 years to 0.60 at 15 years. The gingival index passed from 0.28 to 0.51 between 6 and 15 years.

[Gutta-percha cones: chemical composition, X-ray analysis]. / Les cones de Gutta-percha: composition chimique, analyse aux rayons X.

We determined the chemical composition, confirmed on X-ray diffraction analysis, of 10 brand commercially available dental gutta-percha cones. We observed a great chemical heterogeneity among gutta-percha cones of different origin as well as within the same brand between small and large sizes.