Cytotoxic Interactive Effects of Dentin Bonding Components on Mouse Fibroblasts

Previous studies have shown a wide range of pulpal reactions to dentin bonding systems and a poor correlation between in vitro and in vivo toxicity of dentin bonding agents. Because dentin bonding agents are composed of multiple components which may diffuse through dentin, we hypothesized that these components may cause cytotoxicity through interactive (synergistic) effects. We investigated the cytotoxicities of four dentin bonding components-HEMA, Bis-GMA, TEGDMA, and UDMA-and interactive effects for three binary combinations of the dentin bonding components-HEMA and Bis-GMA, Bis-GMA and TEGDMA, and TEGDMA and UDMA. Cytotoxicities to Balb/c 3T3 mouse fibroblasts were measured by the MTT assay. Concentrations which caused 50% toxicity compared with controls (TC50 values) were compared, and the interactive effects were determined by evaluation of the differences between observed and expected MTT activities of the cells. The ranks of toxicity of the dentin bonding components in terms of TC50 values were as follows: Bis-GMA > UDMA > TEGDMA >>> HEMA (least toxic) after 24- and 72-hour exposures. As binary combinations, the three combinations of dentin bonding components interacted in three ways—synergism, additivism, and antagonism-which were influenced by the concentrations of both components. The longer period of exposure resulted in a significant increase in the cytotoxicity of the dentin bonding components and combinations. The findings indicate that both exposure time and the interactions between the dentin bonding components may be important parameters in determining the cytotoxicity of dentin bonding agents in vivo.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66489/2/10.1177_00220345950740091601.pd

Quantitative scale of oral mucositis associated with autologous bone marrow transplantation

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Two-Versus Three-Dimensional In Vitro Differentiation of Human Pulp Cells Into Odontoblastic Cells

International audienceThe spatial organization of the pulp cells may modify the cytodifferentiation process. The purpose of this study was to compare the two-versus three-dimensional cell culture systems for differentiation of human odontoblastic cells in vitro. Pulpal cores from freshly extracted human third molars were cultured in vitro in a perfusion device on two types of membranes: polyester membrane (twodimensional [2D] cell culture) and nylon mesh (three-dimensional [3D] cell culture). The cells were incubated with minimum essential medium containing (a) substitute serum, (b) 10% fetal calf serum (FCS), (c) 10% fetal calf serum + 2 mM β-glycerophosphate (βGP), and (d) 10% fetal calf serum + transforming growth factor (TGF)β1. Immunohistochemistry was used to evaluate the expression of collagen I, osteonectin, and nestin. Small differences were observed between 2D and 3D cell culture systems. This was particularly evident in the 10% FCS group. β-Glycerophosphate in the 3D system seems to stimulate the osteogenic cell phenotype, as a considerable induction of osteonectin is observed

The effect of cavity restoration variables on odontoblast cell numbers and dental repair

International audienceObjectives: Dentinal repair following cavity restoration is dependent on several parameters including the numbers of surviving odontoblasts. The purpose of this study was to examine the effects of cavity cutting and restoration treatments on post-operative odontoblast numbers. Methods: 353 Standardised non-exposed rectangular Class V cavities, were cut into the buccal dentin of intact 1st or 2nd premolar teeth of 165 patients, aged between nine and 25 years of age. Composite cavity restorations with various etching treatments were compared with resin-modi®ed glass ionomer cements, enamel bonding resins, as well as polycarboxylate, calcium hydroxide, and zinc oxide eugenol materials. Following tooth extraction (20±381 days) for orthodontic reasons, the area of the reactionary dentine and the area of the odontoblasts was measured histomorphometrically. Results: Odontoblast numbers and dentine repair activity were found to be in¯uenced more by cavity restoration variables, than the choice of cavity ®lling materials or patient factors. The most important cavity preparation variable was the cavity remaining dentine thickness (RDT); below 0.25 mm the numbers of odontoblasts decreased by 23%, and minimal reactionary dentine repair was observed. Conclusions: Odontoblast injury increased as the cavity RDT decreased. In rank order of maintaining odontoblast numbers beneath restored cavities with a RDT below 0.5 mm, and using calcium hydroxide for comparison; calcium hydroxide (100%), polycarboxylate (82.4%), zinc oxide eugenol (81.3%), composite (75.5%), enamel bonding resin (49.5%) and RMGIC (42.8%). The vitality and dentine repair capacity of the pulp is dependent on odontoblast survival. Variations in the extent of odontoblast injury caused during operative procedures, may be the major underlying reason for the success or failure of restorative treatments

Influence of resinous monomers on the differentiation in vitro of human pulp cells into odontoblasts.

International audienceOdontoblasts are highly differentiated postmitotic cells, which under pathological conditions such as carious lesions and dental injuries may degenerate and be replaced by other pulp cells. A recent work showed that this physiological event can be reproduced in an in vitro assay system. The purpose of the present study was to evaluate the effects of resinous monomers on odontoblast differentiation in vitro. Pulp cores from extracted human third molars were cultured with ␤-glycerophosphate (2 mM) and used to evaluate the effects of TEGDMA, HEMA, UDMA, and Bis-GMA on the differentiation of pulp fibroblasts into odontoblasts. The effect of the monomers was studied by evaluating the expression of several odontoblast specific genes. In the absence of monomers, mineral nodule formation was observed. Pulp cells contributing to the nodule formation synthesized type I collagen, osteonectin, and dentin sialoprotein (DSP). In addition, Fourier transform infrared microspectroscopy showed that the mineral and organic composition of the nodules were characteristic of dentin. When the monomers were added at nontoxic concentrations, the effects of HEMA and Bis-GMA were more evident than that of TEGDMA and UDMA on collagen 1, osteonectin, and DSP expression. However, all monomers significantly decreased DSP expression and completely inhibited the mineral nodule formation

Human odontoblast cell numbers after dental injury

International audienceObjectives: The purpose of this study was to measure the changes in odontoblast cell numbers in response to cavity restoration variables and patient factors, and the effect these factors have on dental repair by tertiary dentinogenesis. The number of vital odontoblasts is a critical factor for pulpal repair following restorative surgery, and yet little information is available on these cell numbers. Methods: Class V non-exposed cavities were prepared in the buccal surface of intact first or second premolar teeth of 27 patients, between 9 and 17 years of age. Following tooth extraction (28-163 days) the area of reactionary dentine and the area of the odontoblasts were measured histomorphometrically. Results: Patient factors, as well as cavity preparation and restoration variables, had little effect on the numbers of odontoblasts per pulpal unit area. However, the age of the patient did appear to have an effect on the reactionary dentine secretory capacity of odontoblasts per unit area, and on the relative number of odontoblasts beneath cut dentinal tubules. Conclusions: Odontoblast cell numbers were maintained following the preparation of cavities cut into dentine with a 0.5 mm residual dentine thickness. The repair capacity of the pulp-dentine complex would appear to be age dependent, this may explain differences in the success of various restorative treatments between patien

Polymerized bonding agents and the differentiation in vitro of human pulp cells into odontoblast-like cells.

International audienceObjectives: Odontoblasts are highly differentiated post-mitotic cells, which under pathological conditions such as carious lesions and dental injuries may degenerate and be replaced by other pulp cells. We have recently shown that this physiological event can be reproduced in an in vitro assay system, but is highly modified by the presence of unpolymerized resinous monomers. Our hypothesis was that the photopolymerization of the monomers in the bonding agents might abolish these negative effects. The purpose of this study was to evaluate the effects of polymerized dentin bonding agents, through dentin slices, on odontoblast differentiation in vitro. Methods: Pulp cells were obtained from human third molars. They were used to study the effects of four dentin bonding agents through 0.7 mm dentin slices which served as a barrier between the bonding agents and the culture medium. The media containing the bonding agents' extracts were added at non-toxic concentrations onto the cultured cells. Immunohistochemistry was performed to study the differentiation of pulp fibroblasts into odontoblasts under these conditions by evaluating the expression of several odontoblast specific genes. Results: Pulp fibroblasts cultivated under these conditions synthesized type I collagen, osteonectin, dentin sialoprotein and nestin at the same level as in control cultures. Moreover, pulp cells synthesized a mineralized nodular extracellular matrix. Expression of these proteins was higher in the cells contributing to the nodule formation. In addition, except nestin, all these proteins were expressed in the mineral nodules. Significance: This work shows the lack of effects of photopolymerized bonding agents, through dentin slices, on cytodifferentiation of secondary odontoblasts