The mineralization of mantle dentine and of circumpulpal dentine in the rat: an ultrastructural and element-analytical study

Abstract

The purpose of this study was to compare the biomineralization of circumpulpal dentine with that of mantle dentine by ultrastructural and element-analytical techniques. Forty upper second molar germs of 10-day-old albino rats were cryofixed in liquid nitrogen-cooled propane and embedded in resin after freeze drying. Semithin dry sections were cut for analyzing the calcium and phosphorous concentration in initial mantle dentine, at the mineralization front of circumpulpal dentine, in the middle region of circumpulpal dentine and in mantle dentine peripheral to circumpulpal dentine. For the morphological evaluation of mineral deposits we compared ultrathin and unstained sections of cryofixed molars with chemically fixed molars. For both dentine types it was found that they develop via identical steps of mineral formation at collagen fibrils and non-collagenous matrix molecules. In circumpulpal dentine no globular mineral protrusions along the mineralization front (i.e. calcospherites) and no indications of interglobular dentine at the transition from circumpulpal dentine to mantle dentine were present. Two von Korff fibres were not only visible in mantle dentine but also in circumpulpal dentine. Matrix vesicles were present only during the formation of an initial coherent layer of mantle dentine and could not be observed during successive formation of mantle dentine and circumpulpal dentine. The element-analytical data did not demonstrate any difference in the mineral content between the two dentine types. Therefore, we conclude that mantle dentine and circumpulpal dentine in the rat molar possess a high degree of structural and chemical similarity and that only the extent of terminal branching of the odontoblast processes gives an approximate estimation of the thickness of mantle dentine.

Initial aspects of mineralization at the dentino-enamel junction in embryonic mouse incisor in vivo and in vitro: A tem comparative study

“…The electron-lucent collagen fibrils seem to play an important role in the formation of enamel crystal as shown by the periodic arrangement of enamel crystallites perpendicular to the fibrils. A similar observation was recently reported by Stratmann et al (1997). Furthermore, in our observations at initial stages of mineralization, groups of enamel crystals seem to emerge from the dentine at specific loci.…”

“…In the mature human tooth, a persisting area of separation between enamel and dentine was found to be oe,-cupied by fibrils 80 to 120 nm linking the enamel mineral to the fibrillar network of the dentinal matrix (Lin et al, 1993). On the other hand, Stratmann et al (1997) observed the formation of the first layer of mineralized dentine directly in contact with the presecretory ameloblasts. The first stages of enamel mineralization might result from the nucleation of OCP (octaealcium phosphate) clusters (Diekwisch et al, 1995) or of HA (hydroxyapatite) clusters (Cuisinier et al, 1987(Cuisinier et al, , 1993(Cuisinier et al, , 1995, independently of the dentinal matrix.…”

Tooth root dentin mineralization defects in a mouse model of hypophosphatasia

“…Matrix vesicles (MVs) have been suggested to be important in the initiation of mineralization in mantle dentin (27,28). TEM was used to determine if MV formation, distribution, initiation of mineralization, and rupture, contributed to the dentin mineralization defect in the Alpl −/− mice.…”

Synthesis and intracellular transportation of type I procollagen during functional differentiation of odontoblasts

“…Although it is less understood for now, the cellular function of odontoblasts may change from protein synthesis to protein secretion with diVerentiation, i.e. from the early stage characterized by mantle dentin formation to the mature stage involving circumpulpal dentin formation (Kagayama et al 1997;Stratmann et al 1997).…”