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.

Multiple natal teeth and oligodontia: a case report.

A rare family case of a healthy newborn and his mother with multiple natal teeth and oligodontia described. The baby had 12 teeth at birth, while dental records of his mother showed that she had 16 teeth at birth. Possible etiologies and previous reports about natal teeth are discussed.

Ultrastructural organization and microanalysis studies of deciduous enamel crystallites in regional odontodysplasia (RO).

The ultrastructural organization and chemical components of enamel crystallites in two deciduous teeth affected by RO, an uncommon developmental condition giving the tooth a ghost-like appearance, were investigated by scanning and transmission electron microscopy, X-ray diffraction, electron probe microanalysis and Fourier transform improved microspectroscopy. Pathologic mineralizations involving prismatic structures, which affected the size, shape and stoichiometric structure of crystallites and led to enhanced Mg/Ca and Na/Ca ratios and crystal defects, were observed. Local circulatory disorders may have caused this developmental anomaly.

Transmission FT-IR microspectroscopy of mineral phases in calcified tissues.

Fourier-transform infrared microspectroscopy (FT-IRM) was used to study bone mineralization processes in an in vivo model and in enamel in osteogenesis imperfecta. Finally, the ability of FT-IRM to map new bone formed in implanted macroporous calcium phosphate biomaterial from sections was reported for the first time. FT-IRM allowed the correlation of the microstructure of bone formation in the in vivo model with modifications in carbonate and phosphate environments of the mineral phases during maturation. FR-IRM analysis on enamel sections revealed changes in the mineral environment of carbonate and phosphate ions and probably in the size of enamel crystals. These modifications contributed to the fragility of enamel in osteogenesis imperfecta. The infrared functional group imaging of a part of implanted biomaterial and the bone ingrowth provided the visualization of chemical modifications occurring in biomaterial implants at 20 microns spatial resolution. The use of FT-IRM, in conjunction with appropriate sampling methods and data analysis should provide further insight into the molecular structure of mineral phases of calcified tissues and help to elucidate mineralization processes, skeletal disorders and properties of the biomaterials used as bone substitute.

Utilization of activated U937 monocytic cells as a model to evaluate biocompatibility and biodegradation of synthetic calcium phosphate.

The use of calcium phosphate biomaterials as a bone substitute necessitates the use of normative biocompatibility and biodegradation techniques which must be fast, simple and reproducible. In the present study, we have developed an in vitro model to study and to compare different calcium phosphate ceramics. After activation with 1,25-dihydroxy-vitamin D3 and phorbol 12,13-dibutyrate, the monoblastic U937 cells became multinucleated, expressed tartrate-resistant acid phosphatase and several markers of monocyte/macrophage differentiation. Activated U937 cells did not express the vitronectin receptor (VNR) (as revealed using monoclonal antibodies 23C6 or 13C2) but around 25% of the cells were strongly reactive with 211D, a novel monoclonal antibody that recognizes an osteoclast-specific membrane antigenic determinant. These cells remain active/viable with hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP) ceramics. In conclusion, activated U937 cells are good candidates to use in a normative in vitro method to evaluate new biomaterials.

Mineralization of Streptococcus mutans in vitro. An ultrastructural study.

Streptococcus mutans mineralization was studied in vitro, with the use of various metastable calcium phosphate solutions, fluoride-containing or otherwise. Degeneration of bacteria always occurred before their mineralization. After complete mineralization of the cytoplasmic area, growth of crystals was observed both in length and in thickness within the extracellular environment. Composition of the calcifying medium was an essential factor in the S. mutans mineralization process. The present study shows that, contrary to carbonate and magnesium ions that prevent intra- and extracellular deposits, fluoride ions promote crystal growth in the above mentioned mediums. Clinical implications of the role of fluoride, at the plaque level, are foreseen.

Development of a monoclonal antibody against dentin phosphophoryn: a tool to study odontoblastic activity.

The role played by phosphophoryn, one of the major noncollagenous proteins of dentin extracellular matrix, in the mineralization process has not been fully characterized. The purpose of our work was to produce monoclonal antibodies (MAbs) against dentin phosphophoryn and to test their reactivity with primary culture of odontoblasts. Dentin phosphophoryn (DPP) was extracted after the mechanical dissociation of teeth and dialyzed against guanidine and EDTA solutions followed by CaC1(2) precipitation. These extracts were characterized by SDS-PAGE and staining with Coomassie blue and Stains-All. After immunization of mice with these extracts, we produced MAb 7G4, which reacted with dentin phosphophoryn as revealed by Western blot. MAb 7G4 reactivity was tested against a primary culture of pig odontoblasts, revealing filaments specifically stained by the anti-DPP antibody. This antibody will be of great interest to study the mineralization process and dental pulp reaction after capping with various calcium phosphate materials.

Relevance of epidemiological indices for assessing dental fluorosis.

The aim of the study described in this article is to propose a suitable index for epidemiological surveys. The authors define the characteristics of a good index to evaluate a presumed pathology, dental fluorosis, whoever the examiner and whatever the circumstances. The earliest and most commonly used index is Dean's because it permits data comparison among studies. But it has shortcomings due to the low accuracy of its definitions. The TSIF proposed by Horowitz et al. does not bring any noteworthy improvement to the Dean index. The new TF index devised by Thylstrup & Fejerskov is a logical improvement of the Dean index and can reliably be compared with Dean's. The sensitivity of this index come from its 9 stages reflecting the histopathology and fluoride content in the enamel. At the moment it is the most outstanding index for evaluating the severity of fluorosis.

[Epidemiologic investigations on caries prevalence among schoolchildren in Brittany (France)]. / Epidemiologische Erhebungen zur Kariesprävalenz schulpflichtiger Kinder in der Bretagne (Frankreich).

1421 randomly selected 6- to 15-year-old Breton children were examined in 1987 in order to assess the prevalence of caries in permanent teeth. Methods proposed by Turlot & Cahen (1989) were used. At 6, 85.9% of all children were caries-free and at 15, only 5.3%. At 14, DMFT and DMFS rates reached 6.46 and 12.36, respectively. The differences of scores stated between boys and girls and between children from urban and rural regions were not statistically significant. Pits and fissures were more frequently affected than approximal and smooth surfaces. Since 1986, fluoridated domestic salt is available in France. Thus, the present investigation will serve to study the effects of this recently adopted preventive measure.

[Structural, ultrastructural and microanalytical study of multiple enamel pearls]. / Etude structurale, ultrastructurale et microanalyse de perles d'émail multiples.

Numerous enamel drops and compound enamel pearls were found on the radicular proximal faces of maxillary molars and mandibular third molars of a young woman. Enamel and dentin of compound pearls as well as cementum next to drops and pearls presented the same structure and ultrastructure as enamel, dentin and cementum of the corresponding teeth. Microanalysis did not reveal differences between enamel of the mother tooth and enamel of drops and pearls. The enamel drops had no incremental growth lines. Cementum next to enamel drops and compound enamel pearls was acellular and covered occasionally with a thick layer of cellular cementum. Only enamel drops were partially covered by acellular cementum. Close to the enamel drops and at their surface, numerous fusing globular calcifications were observed. Formation of enamel drops and compound enamel pearls on dental root surfaces is rare. The simultaneous presence of numerous enamel drops and some compound enamel pearls on several roots of molars in the same denture seems to be an exceptional phenomenon. The involved factors inducing enamel formation remain still unknown. The multitude of both enamel drops and compound enamel pearl might be due to constitutional predisposition.

[The oro-dental status of children 6-15-years of age in Pays de la Loire, Vienne and Deux Sèvres]. / Etat bucco-dentaire des enfants âgés de 6 à 15 ans des Pays de la Loire, de la Vienne et des Deux Sèvres.

This survey was conducted on a representative sample of schoolchildren aged 6 to 15 years from Pays de la Loire, Vienne and Deux-Sèvres. The results showed that the DMFT and DMFS indices increased with age. The girls had a higher caries experience. The children from rural zones had a higher caries prevalence than those of urban areas. However the differences were not statistically significant. Relatively low values were recorded between 6 and 15 years for the plaque index, the calculus index and the gingival index.