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A seventeen-year-old girl demonstrating severely worn permanent dentition and multiple retained root stumps with dentinogenesis imperfecta is presented. Overdentures were made to preserve bone height, re-establish the lost vertical dimension of occlusion, to provide acceptable esthetics, and to establish an efficient masticatory system.
This study was designed to investigate in vivo i) the role of TGF-beta as an active component of the dentin matrix during induction of reparative dentinogenesis; and ii) the ability of TGF-beta1 isoform to induce dentinogenic events. Dental pulps of dog molars and canines were mechanically exposed, and the following implants were placed intrapulpally for 42 d: i) Demineralized or native autogenous dentin matrix preincubated with a TGF-beta-neutralizing antibody; ii) Millipore filters soaked with solution containing 100 ng/ml of TGF-beta1 from human platelets; iii) biomatrices and filters soaked in control solutions. After incubation of biomatrices with the TGF-beta-neutralizing antibody, demineralized dentin completely lost its inductive activity, while native dentin was only able to stimulate formation of fibrodentin. Millipore filters soaked with TGF-beta1 were consistently surrounded by a thick zone of tubular matrix lined with high columnar polarized cells. The data provide evidence that pulp cells can express their dentinogenic potential in response to an appropriate surface containing exogenous TGF-beta1, and that the dentinogenic activity of dentin matrix may at least partly be ascribed to TGF-beta molecule(s).
The molecular basis underlying the mineralization process associated with the conversion of predentin to dentin is poorly understood. What is clear is that a unique set of non-collagenous proteins (NCPs) participate in the nucleation process and in hydroxyapatite growth during dentin formation. Phosphophoryn (PP), the most abundant NCP in dentin, is secreted by odontoblasts and appears at the mineralization front. Dentin sialoprotein (DSP), another NCP, also appears at the mineralization front, but only accounts for 5-8% of the weight of dentin NCPs. Functionally, PP is believed to be directly involved in tile nucleation process by virtue of its ability to bind to collagen type I, and its high affinity for calcium ions. Based on the analysis of the putative rat PP amino acid sequence, this latter activity is believed due to the highly phosphorylated character of PP, which results from the dual actions of casein kinases I and II at selected domains within PP. The precise role of DSP is currently unknown. In situ studies demonstrate that DSP is substantially expressed in odontoblasts and transiently expressed in preameloblasts. However, no information is currently available to directly explain DSP's role in mineralization. Genetically, we and others have now identified a novel DSP-PP bicistronic mammalian transcriptional unit, suggesting that the functional roles of these two NCPs may also be tightly coupled with respect to dentinogenesis. Certainly, further exciting studies are now needed to explain how this DSP-PP transcriptional unit is finally expressed: whether DSP and PP associate with one another, or with collagen at the mineralization front: and how selective mutations in either gene may influence dentin mineralization.
OBJECTIVE: To investigate the immunolocalization of laminin in the process of dental pulp injury and repair. METHODS: One cavity was prepared on the mesial surface of the first molars of Wistar rats. The animals were sacrificed in 3, 15, and 30 days of post-operation. After histological process, the paraffin sections were reacted with monoclonal antibodies against rat laminin using SABC method. RESULTS: Immunolocalization demonstrated positive staining for laminin in the different stages of dental pulp repair. In 3 days group, no reparative dentin were observed. The positive staining was located in odontoblasts and in predentin. After 15 days, reparative dentin and odontoblasts were observed. The odontoblast like cells and dental pulp cells were stained positively. 30 days later, the stronger staining intensity was observed in odontoblast like cells, pulp cells and in reparative dentin. Immunological reaction was particularly located among the interface of reparative dentin and dental pulp. CONCLUSION: The localization feature of laminin suggested that laminin may be a favored factor for the adhesion of dental pulp cell during reparative dentinogenesis.
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Eight days old offspring of six rats treated with single doses of 40 mg/kg and 50 mg/kg of cyclophosphamide on the 20th day of pregnancy constituted two experimental groups. Group 1 (40 mg/kg) comprised 21 animals, Group 2 (50 mg/kg) 14 animals. Histomorphologic investigations of the maxillary and mandibular incisors revealed the following changes: (1) dental constrictions, (2) niche-like dentinal defects, (3) scalloping of the amelodentinal junction, (4) incremental line in the pre-experimental tooth segment, (5) external resorptions, and (6) diffuse edema in the pre-experimental part of pulp. Constrictions and niches qualitatively concurred with those previously observed in adult rats of the same strain, but the lesion frequency was essentially higher in the offspring. Further, the additional change of external resorptions was evinced by the offspring incisors, and changes only rarely observed in adults, such as scalloping of the dentinoenamel junction and a dentinal incremental line, constituted frequent findings in the offspring material.
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Molar tooth germs from three-day-old rats were cultured successfully for fourteen days, permitting the study of the development in vitro of both extracellular matrix and cellular elements such as odontoblasts and ameloblasts. The ultrastructure of the cultured tooth germs was compared with the ultrastructure of tooth germs in vivo at a comparable developmental stage. Progenitor cells of odontoblasts and ameloblasts were found to differentiate in vitro. Odontoblasts seemed to contain more lysosome-like bodies and fewer secretory granules than in vivo. They formed normally mineralizing dentine or a thick layer of dense, unmineralized predentine with incidentally some amorphous, extracellular material. Enamel was exclusively present opposite well developed dentine. It was often hyper- or hypomineralized and enamel rods were not as regularly shaped as in vivo. In places where no enamel formation had taken place, large amounts of amorphous extracellular material were sometimes seen. From these observations it can be concluded that cellular development in cultured tooth germs appeared more or less normal, but extracellular matrix formation and mineralization were sometimes disturbed.
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