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[The effect of immobilized salivary alkaline phosphatase on remineralization processes].

Relationship between alkaline phosphatase immobilized on apatite and remineralization processes has been studied. The enzyme notably accelerated the remineralization. The course of enzymatic remineralization depended on the source of phosphorus (inorganic phosphorus or beta-glycerophosphate). Calcium incorporation in remineralizing surface was the most rapid in the presence of beta-glycerophosphate. This may be explained by a higher rate of formation of apatite under the effect of immobilized alkaline phosphatase, than of brushite or vitlokite.

Alkaline Phosphatase↗

Intrusion injuries of primary incisors. Part III: Effects on the permanent successors.

Intrusion injuries of the primary dentition are highly associated with developmental disturbances of their successor teeth. The age of the child at the time of injury, the direction and severity of the intrusion, and the presence of alveolar bone fracture are important variables influencing the effect of primary tooth intrusion on the developing permanent germ. The developmental defects of the permanent successor tooth range from mild alteration in enamel mineralization to severe sequestration of the developing germ. This article will review the developmental anomalies of the permanent incisors induced by intrusion injuries of their predecessors.

Age Factors↗

A radiographic study of rostral tooth development in young Friesian cattle.

Twenty-nine British Friesian cattle fed the same diet, slaughtered at various weights and including bulls, steers (castrated males) and females (heifers) were examined. The stage of their rostral tooth development was recorded both visually and radiographically. Insufficient animals were present in each sex and slaughter weight treatment group to allow any comparison between them. When the data for each sex were compared, no statistically significant differences were seen between the mean ages at which bulls, steers and heifers attained each stage of dental development as determined from their radiographs. The results for all 29 cattle were then combined. This combined data showed a relationship between age and those stages of tooth formation which could be differentiated by examination of the X-ray films. As most phases of tooth formation occurred within well defined limits, it is suggested that radiographs of rostral tooth development might be used to estimate the age of cattle.

Age Factors↗

Mandibular cheek tooth development and its relationship to age in young Friesian cattle.

The oral and intra-osseous development of each of the six manidibular cheek teeth found in the permanent dentition of cattle was studied. The animals used were all British Friesians, of varying sex, and slaughtered at different weights at ages between 13 and 22 months. The various stages of development observed in each tooth together with the mean age and age range at which they were seen are recorded. Significant differences were found between the ages at which several of the developmental stages were seen in most of the teeth and indicated that tooth formation in the Friesian cattle studied tended to fall within well defined age limits.

Age Determination by Teeth↗

Sexual dimorphism in dentition mineralization.

This study determined for 121 boys and 111 girls of the serial experimental group of the Burlington Growth Centre the age, time interval and age sequence of 14 stages of mineralization of all tooth types. The two sexes differed significantly in the age at which the stages of tooth mineralization appeared, and in the length of the interstage intervals. In the canines, there was maximum sex difference in mineralization, which was almost 20 per cent and resulted from a delay in the boys. Changes in sequence of mineralization were due to delay rather than to acceleration. Sex differences in tooth mineralization manifested themselves before puberty, and mineralization was not accelerated at puberty. In contrast, post-pubertal mineralization of third molars appeared to be accelerated in both sexes and occurred earlier in the boys.

Age Factors↗

Amelogenesis imperfecta: diagnosis and resolution of a case with hypoplasia and hypocalcification of enamel, dental agenesis, and skeletal open bite.

A case of amelogenesis imperfecta with hypoplasia, hypocalcification of the enamel, congenital absence of teeth 12 and 22, delayed eruption of tooth 23, edge-to-edge incisal relationship, open bite, and bilateral posterior cross bite at the level of the first and second premolars is presented. Lateral skull teleradiography indicated a Class III skeletal pattern of maxillary origin associated with a dolichofacial pattern with multiple indicators of facial hyperdivergence. The patient presented a major esthetic abnormality of the face and required orthodontic treatment prior to a prosthetic solution with full-coverage metal-ceramic crowns in both the maxilla and the mandible. The diagnosis of cases such as this one and the therapeutic implications from an orthodontic and prosthetic standpoint are reported.

Adolescent↗

The relationship of maxillary cheek tooth development to age in young Friesian cattle.

Radiographs were taken of both the right and left sets of maxillary teeth in 23 Friesian cattle of known age. The stage of development of each permanent tooth was ascertained and the degree of root resorption in the deciduous premolars was noted. All stages in individuals were later than for those of the mandibular cheek teeth except in the case of the first permanent premolar. As with mandibular cheek tooth development stages of formation occurred within certain age limits.

Age Factors↗

Tooth formation and the mandibular symphysis during the first five postnatal months.

Schedules based on tooth development are useful in age assessments of children, but in early infancy they are based on only a few studies. The radiographic appearance of the mandibular symphysis during the first postnatal months has not gained attention. The present study describes the formation of teeth and the development of fusion between the mandibular halves during the first five postnatal months, as seen in panoramic tomograms taken in medicolegal autopsies of 29 ethnic Finns, 19 boys and 10 girls, at the Department of Forensic Medicine, University of Helsinki. In the majority of the infants, the criteria of sudden infant death (SID) were fulfilled. The stages of tooth formation used were those applied by Moorrees et al. with one modification (Nyström et al.). Mineralization of all primary teeth proceeded rapidly during the first postnatal months, the change being on average two developmental stages in four months. Considerable variation in tooth development existed in infancy. The mandibular halves were separated at birth. Complete fusion had occurred in the majority of infants aged four months, and the tomograms of the remaining infants showed a thin vertical line in a part of the symphysis. The marked changes, which during the first postnatal months occur in the radiographical appearance of the mandibular symphysis, and in the formation of primary teeth, provide valuable information for age assessments of infants.

Age Determination by Teeth↗

[Ultrastructural changes in cells of the inner enamel epithelium, stratum intermedium and reticulum stellatum in the enamel organ of the upper incisor of the Wistar rat at different phases of amelogenesis].

An electronmicroscopical study of the enamel organ of the upper incisors germs of Wistar rats was performed to analyse the ultrastructural features of the cells of the inner epithelium, the intermediate layer and the stellate reticulum, during preimary, young, transitional and mineralized enamel phases of amelogenesis. So, it was observed that the mitochondria in the ameloblasts are ovoid before the beginning of the enamel matrix formation and in the primary and young enamel phases. However, in the transitional and mineralized phases, these organelles are long and tortuous and some are characterized by a compact structure. In the cells of intermediate layer and stellate reticulum, the mitochondria are ovoid until the beginning of the mineralized phase. At the ending of this phase, these organelles are very long and present irregular form; many of them show also a compact structure. The "zonula adhaerens" could be observed only in the ameloblasts of the primary and young enamel phase. The cytoplasm of ameloblasts, during primary and young enamel phases is characterized by an abundance of free ribosomes and a branular endoplasmic reticulum; but during transitional and mineralized enamel phases, the cytoplasm of these cells shows little granular endoplasmic reticulum and free ribosomes, but ehe agranular endoplasmic reticulum is present. The granular endoplasmic reticulum and free ribosomes are abundant in the cells of the intermediate layer and stellate reticulum at the ending of the young enamel phase, in the transitional enamel phase and in the beginning of the minieralized phase. During different phases of amelogenesis, in the three above referred layers of the enamel organ, were also studied the features of the Golgi apparatus the presence and topographic distribution of the pigment granules, as well as the lysosomes, desmosomes and the tonophibriles.

Ameloblasts↗

Putative membrane receptor for 1,25(OH)2 vitamin D3 in human mineralized tissues during prenatal development.

The calciotropic hormone, 1,25(OH)2vitamin D3[1,25(OH)2D3], controls the formation of dental and bone mineralized tissues. The role of nuclear 1,25(OH)2D3 receptor has been extensively studied in the diverse secretory cells, i.e., osteoblasts, chondrocytes, ameloblasts, and odontoblasts. A nongenomic pathway also has been characterized and related to the interactions of 1,25(OH)2D3 ligand with a putative cell membrane receptor. This recognition moiety called 1,25(OH)2vitamin D3 membrane-associated, rapid-response steroid-binding [1,25D3-MARRS] protein is investigated here in the craniofacial skeleton of human embryos and fetuses. Immunolocalization using a specific Ab099 against chick intestinal basolateral 1,25D3-MARRS protein was performed. The data show a complementary expression pattern of the membrane receptor when compared with published data on the nuclear receptor, notably during amelogenesis. In mandible, membrane receptors for 1,25(OH)2D3 were identified in the heterogenous bone cell population, including osteoblasts and osteoclasts. Differential 1,25D3-MARRS protein levels were observed in distinct developmental stages and anatomical sites of tooth and bone, suggesting the existence of cross-talk between local factors and 1,25D3-MARRS protein expression.

Gestational Age↗

Developmental stages of the third molar in Israeli children.

PURPOSE: The purpose of this study was to examine the developmental stages of the third molar in Israeli children, compare its development in boys and girls, in the maxilla and mandible, right to left sides in various age groups, and relate the developmental stage to chronological age. METHODS: Panoramic radiographs of 693 healthy children and adolescents (328 boys and 365 girls) ages 7 to 16 were analyzed using a modified 6-stage method. Since the 16-year-old group was too small for statistical analysis, it was later excluded from the study. Radiographs were obtained from patient files. RESULTS: There were no significant differences in the development of the third molar between boys and girls and between right and left sides. Slight differences were found between the maxilla and mandible. The first appearance of a radiolucent bud was at age 8.7 in the mandible and 9.3 in the maxilla. Crown completion was observed on average at age 11.7 in the maxilla and 11.8 in the mandible. CONCLUSIONS: There was a high correlation between third molar development and chronological age. Agenesis can be determined conclusively if no radiolucent bud is present beyond age 14. The modified 6-stage method allowed more accurate determination of developmental stages.

Adolescent↗