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Biomedical subjects

J C Ajacques

Publications and source records attributed to J C Ajacques.

At least 19 recordsLinked to original sources
PubMed1998

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.

Child, Preschool↗
PubMed1995

[Acoustic characterization of velar insufficiency in young children].

The following study concerns the acoustic parameters marking the difference between the phonation of children with velar incompetency and a corresponding control group. Population is made of 64 children aged 5 and 6; 32 are in the control group and 32 in the pathological group. Each child was required to repeat several words; 10 vowels and 9 consonants were taken from those words. Acoustic signal was recorded and studied using a standard speech assessment work station. 63 parameters for the vowels and 6 for the consonants were studied. Results showed that the best parameters concerned the vowels and that cepstrum coefficients were an efficient tool to perform the separation of the two groups. On the contrary, formants, voice pitch and jitter did not appear to be efficient enough to do this task. It was, then, deduced a check form for velopharyngeal incompetency, form which will be tested in future work.

Case-Control Studies↗
PubMed1990

[The dynamic equilibrium of the craniofacial structures].

Hanging at the extremity of the cervical spine, and subjected to multiple stresses from both suspensory muscular bundles and the dental system, man's craniofacial unit is a compromise between specific determinism and the dynamics involved. Analysis provides an understanding of the craniofacial architectonic in view of such constraints. Pathological cases characterized by more severe structural disorders shed light more particularly on this analytical concept.

Biomechanical Phenomena↗
PubMed1989

[Amelogenesis imperfecta and hypothalamo-hypophyseal insufficiency].

Eleven patients with hypopituitarism, medio-facial hypoplasia and amelogenesis imperfecta were examined. The hypothalamo-pituitary dysfunction affected somatotrophic, gonadotrophic, corticotrophic and thyrotrophic function. The facial anomalies included medio-facial hypoplasia with hypertelorism and amelogenesis imperfecta. The latter--hypoplastic in nature--was noted in all anterior teeth and affected both dentitions. The enamel defect was confirmed on microscopic examination of an impacted tooth. The spectrum of malformation may also present as amelogenesis imperfecta in association with somatotropin deficiency. A genetic mechanism may possibly account for the clinical elements.

Amelogenesis Imperfecta↗
PubMed1989

[Osteogenesis imperfecta and dentinogenesis imperfecta. Apropos of 4 cases].

Based on four personal cases of osteogenesis imperfecta and dentinogenesis imperfecta, the authors review the semiological elements constituting the syndrome, and assign each case to the Sillence (1979) classification. The author established his classification on clinical criteria and the genetic nature of the various forms of osteogenesis imperfecta, however, the most recent discoveries concerning collagen biochemistry confirm that the condition is without doubt more heterogenous than suggested clinically, thereby better explaining the wide range of mutations encountered.

Child↗
PubMed1989

[Closure of residual clefts of the palate. Indications and technic].

Residual defects of the palate, a possible complication of early surgery in the view of MALEK and PSAUME, should be closed as early as possible in order to avoid compromising normal acquisition of language while respecting bony growth. The technique described (staphylorrhaphy under cover of a rigid compression arch) takes both these requirements into account.

Cleft Palate↗
PubMed1987

[Structure, ultrastructure and microanalysis of the enamel of teeth near maxillary clefts].

Teeth located in the vicinity of cleft palate were studied using correlated light microscopy, microradiography, SEM, TEM and microanalysis. Structural, ultrastructural and chemical abnormalities were found in enamel. The enamel surface presented micro and gross hypoplasia, associated with hypomineralization. Microradiography showed the antenatal enamel to be more mineralized than postnatal enamel. Microanalysis showed the Ca/P ratio measured at the enamel surface to be higher in the teeth associated with cleft palate, compared with controls. The Ca/P value was due to a Ca increase and a P decrease in the enamel surface. The Ca increase was correlated with a decrease in Mg, supporting the hypothesis of a Mg/Ca substitution in the apatitic structure.

Adolescent↗
PubMed1984

Dental involvement in congenital chloride diarrhea.

Dental involvement in a case of congenital chloride diarrhea (CCD) was studied using light microscopy of decalcified and undecalcified sections, microradiography and TEM. Mixed enamel lesions were found, involving gross hypoplasia at the cuspal level and hypocalcification occurring all over enamel. The hypocalcification resulted in the immature aspect of the prismatic enamel, porosities, amorphous areas, prominent incremental lines and round-ended crystallites. A marked hypocalcification suggests a temporary break of amelogenesis likely related to acute episodes of the disease. Globular calcifications were associated with enamel formation. Dentinal hypocalcification was conspicuous and diffuse all over dentine. A globular mineralization pattern was revealed by the tretracycline (TC) stain which was well preserved in decalcified sections, thus indicating that TC uptake is related to the organic matrix. It is unlikely that TC alone is responsible for the hypocalcified areas which extended widely beyond the TC-stained bands. It is suggested that TC uptake only adds to dental defects induced by the metabolic troubles of CCD.

Alkalosis↗
PubMed1981

[Mohr's syndrome : type II orofaciodigital syndrome (author's transl)].

Mohr's syndrome consists of an association of three types of malformation : oral, facial, and digital. It is very similar, therefore, to the syndrome of Papillon-Léage and Psaume. Apart from this, precise, constant characteristics can be recognized which identify it as a separate entity. Firstly, the genetic mode of transmission differs. Secondly, clinical signs are dominated by the frequency and severity of the distal lesions, such that bilateral syndactyly of the big toe is a key element in the differential diagnosis.

Abnormalities, Multiple↗