Toxicity of some dental cements in a cell culture system.

A cell culture method has been used to study the effect of zinc phosphate cement (De Trey's Zinc Zement Improved), zinc silicophosphate cement (Fluoro-Thin) and polycarboxylate cement (Durelon) on animal cells. Disks (20 x 1 mm) of the materials were placed in the center of plastic Petri dishes and subsequently incubated with human epithelial cells. Cell multiplication, medium pH and the release of cement constituents were measured. All three cements exhibited a cytotoxic effect, which was most pronounced in the cultures with zinc silicophosphate cement and polycarboxylate cement. The results also indicated that cell growth on the surface of the disks is a more sensitive indicator of cytotoxicity than cell growth around the disks. pH of the medium was only slightly affected in cultures with polycarboxylate cement, whereas a decrease was found in cultures with zinc phosphate cement and especially with zinc silicophosphate cement. A rapid release of phosphate was found in cultures with zinc silicophosphate cement. Zinc was released into the medium from disks of zinc phosphate cement, zinc silicophosphate cement and polycarboxylate cement--exceeding the toxicity level for the present cell line after 24 h. In cultures with zinc silicophosphate cement and polycarboxylate cement the release of fluoride reached toxic levels within the same time interval.     

Toxicity of some dental cements in a cell culture system

abstract – A cell culture method has been used to study the effect of zinc phosphate cement (De Trey's Zink Zement Improved®), zinc silicophosphate cement (Fluoro-Thin®) and polycarboxylate cement (Durelon®) on animal cells. Disks (30 × 1 mm) of the materials were placed in the center of plastic Petri dishes and subsequently incubated with human epithelial cells. Cell multiplication, medium pH and the release of cement constituents were measured. All three cements exhibited a cytotoxic effect, which was most pronounced in the cultures with zinc silicophosphate cement and polycarboxylate cement. The results also indicated that cell growth on the surface of the disks is a more sensitive indicator of cytotoxicity than cell growth around the disks. pH of the medium was only slightly affected in cultures with polycarboxylate cement, whereas a decrease was found in cultures with zinc phosphate cement and especially with zinc silicophosphate cement. A rapid release of phosphate was found in cultures with zinc silicophosphate cement. Zinc was released into the medium from disks of zinc phosphate cement, zinc silicophosphate cement and polycarboxylate cement – exceeding the toxicity level for the present cell line after 24 h. In cultures with zinc silicophosphate cement and polycarboxylate cement the release of fluoride reached toxic levels within the same time interval.     

Aluminium and dental materials—a study in vitro of its potential release and toxicity

Summary. Aluminium release was investigated from a range of dental materials including several composed of aluminosilicate glass; with the exception of ASPA and Silicap, the release was negligible. The concentrations of aluminium released from these two materials were neither toxic to a fibroblast cell line nor to mouse peritoneal macrophages. Levels in the order of 40ppm were required to exert a toxic effect.     

Biological tests of a silicophosphate cement

The biological compatibility of a silicophosphale cement (Fluoro-Thin®) and a zinc phosphate cement (de Trey's Improved®) has been assessed in in vitro (cell culture) and in vivo (monkey teeth) tests. In the in vitro tests both materials were toxic when freshly prepared, In experiments with prolonged cell-material contact time, with set specimens of the materials, the zinc phosphate cement appeared to be non-toxic, whereas the silicophosphate cement was clearly toxic. The in vivo experiments confirmed that a possible pulp reaction caused by zinc phosphate cement is of a mild nature. The silicophosphate cement, however, caused a moderate or severe reaction in the pulp after 8 days of observation, and there was chronic inflammation in most teeth after 36 or 72 days. It was concluded, therefore, that Fluoro-Thin should not be used as a luting agent or for restorative purposes in direct contact with vital dentine.     

Interactions of zinc with fluoride on growth, glycolysis and survival of Streptococcus mutans GS-5

Effects of zinc and/or fluoride on growth, glycolysis and survival of Streptococcus mutans GS-5 were examined in vitro. Zinc inhibited growth and glycolysis, and enhanced the antimetabolic activity of fluoride. Zinc alone had little effect on cell survival. During cell growth without pH control a protection from cell death was mediated by fluoride, which appeared to be caused by a higher final pH in the culture medium. When cell death was observed under controlled pH conditions in a lactate-acetate buffer at pH 6.5, 5.0 or 4.0, fluoride was bactericidal only at pH 4.0. However, the combination of zinc plus fluoride was strongly bactericidal at all pH values that were tested.     

Effect of dental luting cements from the viewpoint of cell recovery (in vitro)

Cell recovery of four cell lines [L-929 cells, HEp-2 cells, Gin-1 cells and the cells from human dental pulp tissues (Hp cells)] was examined after exposure to four zinc phosphate cements, five polycarboxylate cements, three glass ionomer cements, five resin based cements and one zinc oxide-eugenol.EBA cement. Phosphate cements, glass ionomer cements and zinc oxide-eugenol.EBA cement were markedly cytotoxic to the four cell lines 3 hours and 24 hours after mixing. Polycarboxylate cements considerably inhibited cell recovery of the three types of cells except Hp cells even 24 hours after mixing, compared to the gradual recovery of Hp cells after mixing. Two of the resin based cements inhibited cell recovery, while the three others allowed moderate cell recovery. The pH values of the medium used for the experiments was 6.6-6.8 for phosphate cements, glass ionomer cements and zinc oxide-eugenol.EBA cements. Polycarboxylate cements had no effect on the pH. On the other hand, in resin based cements the pH was shifted from acidic to basic. The solubility of the materials used was, in decreasing order: glass ionomer cements, zinc oxide-eugenol.EBA cement and one of the resin based cements, polycarboxylate cements, phosphate cements and another resin based cement, and the other three of resin based cements (lowest). The difference in cell recovery was considered to be due to composition and solubility of the materials.     

Viadent, ethanol, and pH effects upon gingival epithelial-like cells, in vitro

Interest has recently been directed towards the use of antiplaque mouthrinses. Most published material concerns the antimicrobial effects of these agents rather than their effects upon oral tissue. This study was conducted to evaluate the effect of a sanguinarine-containing mouthrinse called Viadent upon epithelial-like gingival cells. The cells were grown for 24 hours in supplemented Earle's medium, with and without different Viadent dilutions. Cell counts were made with a hematocytometer. It was found that 50% of the cells were inhibited at 1.2% Viadent. In similar studies, it was found that 70% ethanol and two pH buffers were less toxic than Viadent. Exposure of preformed cell monolayers to Viadent also showed significant inhibition. The relative toxicity of different antiplaque agents may be compared using such cells as a model system. In conclusion, it was observed that Viadent significantly affected gingival cell growth in vitro, that viable cell numbers were greatly reduced by short time exposure, and that the toxic effect of Viadent could only partially be accounted for by ethanol content and/or pH.     

Evaluation of the cytotoxicity of four dental materials in vitro assessed by cell viability and enzyme cytochemistry

The cytotoxic effects of zinc phosphate and silicate cements, Concise composite and zinc oxide/eugenol were evaluated after 24 h in an in vitro system which simulates the clinical usage of the material, and the results compared with those using phenol. Data of gross changes affecting cell viability placed these materials in ranking order of increasing severity: Concise less than zinc phosphate less than Silicap much less than zinc oxide/eugenol. More discrete changes involving alterations in enzyme cytochemistry were assessed and the significance of the results discussed. The presence of dentine powder in the system reduced the cytotoxic effects on these materials.     

The cytotoxicity of Sne-Pack periodontal dressing and scanning electron microscopic study]

We prepare a non-eugenol periodontal dressing Sne-pack(Sp),then investigated the effects of cess cytotxicity and observed the surface of materials on scanning electron of materials on scanning electron microscopy.The comparison results with Coe-pack (Cp) and zinc oxide-eugenol(Ce)showed that three materials have inconsiderable toxic effect on L-929 cell,the Sp and Cp dressing are smoother than Ce.     

In vitro cytotoxicity of root canal filling materials: 1. Gutta-percha

Gutta-percha (GP) has been the most widely used root canal filling material because of its well-known low toxicity. The inertness of GP, however, was challenged recently. The purpose of this study was to evaluate the toxicity of marketed endodontic GP using the radiochromium release test. Fourteen commercially available and three experimental GP brands were tested. Raw GP, zinc oxide, and barium sulfate, which were considered major components of GP points, and zinc ions were also evaluated. The material was spread to cover the bottom of testing wells after being dissolved in chloroform or warmed. A labeled suspension of L929 cells was added to the wells. After incubation at 37 degrees C for 4 and 24 h, extracellular radiochromium in the culture medium was measured and calculated in percentage of the total intracellular label. Spontaneous release of radiochromium was used as control and the results were considered to be within normal limits either at 4 or 24 h. All chloroform-dissolved GP showed low toxicity at 4 h, whereas warmed GP showed statistically significant differences at 4 h. Both dissolved and warmed GP were toxic at 24 h. The raw materials and barium sulfate were not toxic, whereas zinc oxide and zinc ions showed marked toxicity. All GP points tested were toxic at longer observation periods, and the toxicity was attributed to leakage of zinc ions into the fluids.     

The modified model cavity method for assessing antibacterial properties of dental restorative materials

A new in vitro method for assessing the antibacterial properties of dental restorative materials is described with ratios of test material/culture medium volume aiming to simulate conditions around a restoration in vivo. Antibacterial activity is determined by the reduction in optical density of the test culture relative to controls. The method was used for assessment of the antibacterial activity of five dental materials of different composition against five oral bacteria. Release of zinc and fluoride from these materials was also measured and correlated with antibacterial activity. There was a general trend toward greater antibacterial activity with increased zinc release, while fluoride release had a significant effect on only one organism. While all the materials, when freshly mixed, were strongly toxic to three out of the five bacteria studied, much of this activity was lost after the materials had set.     

Investigation of the cdytotoxicity of bacterial species implicated in pulpal inflammation

Summary. The major bacterial species in ferret plaque were indetified and the cytontoxicity of selected orginsisms in vitro assessed to determine their porential role in pulpal inflammation. Of the five species investigated in detail the cell fractions of Escherichia coli and Streptococcus sanguis from anaerobic cultures. The release of a lysosomal enzyme was elicited to differing degree by all five bacterial species. While the amount of enzyme released from macrophages was greater, fibroblasts were generally more sensitive, with the media fraction in addition to the cellular fraction affecting cell numbers and enzyme release. The action of S. faecalis on both cell types was shown to be dose-department. Since the number of bacteria involved in vivo is small these results suggest they would have little direct toxic effect indicating that some other mechanism must be invoved.     

pH值对HAPw-nmZnO-nmCaO复合生物材料形貌影响的研究

目的:探讨不同pH条件下,纳米氧化锌(nmZnO)和纳米氧化钙(nmCaO)对羟基磷灰石晶须(HAPw)表面改性形貌的影响。方法:在温度为70 ℃,pH分别为6.0、6.2、6.4、6.6、6.8、7.0条件下,硝酸锌和硝酸钙溶胶-凝胶法改性HAPw,通过X射线衍射仪(XRD)、透射电子显微镜(TEM)和X射线能量色散光谱仪(EDX)分析材料的物相组成和表面形貌。结果:在不同pH条件下,nmZnO和nmCaO颗粒在HAPw表面的分布存在差异。nmZnO颗粒为六方晶型,nmCaO为圆形颗粒状,颗粒与晶须通过化学键相互结合。结论:在pH为6.2和6.4时,采用溶胶－凝胶法可实现nmZnO和nmCaO对HAPw的较优改性。     

Ion release from copper phosphate cement and influence on Streptococcus mutans growth in vitro: a comparative study

The aim of this study was to compare the effects of a black copper cement (BCC), an established restorative material (a conventional glass ionomer cement) and two temporary restorative materials (a zinc phosphate and a zinc polycarboxylate cement) on the growth of Streptococcus mutans in vitro, and to correlate bacterial growth with ion release from each material. Test specimens were eluted in either 0.1 M lactic acid, pH 4, or 0.1 M sodium chloride, pH 7. At 2 days, 7 days, 28 days and 6 months, eluates were inoculated with S. mutans and bacterial growth was recorded. Metal ion (Cu(2+), Zn(2+ )and Mg(2+)) and fluoride release were measured. At most immersion times, the different materials had a statistically significant inhibitory effect on bacterial growth compared to the respective control, at both pH levels. The inhibitory effect decreased with time and in most cases was associated with high levels of ion release at the beginning of the experimental period, followed by significantly lower levels. For BCC, there were statistically significant relationships between the median rates of growth of S. mutans in the presence of BCC eluates and the median values for release of copper and zinc, although not magnesium. Of the different materials, BCC demonstrated greatest antibacterial activity.     

Biological evaluations of zinc hexyl vanillate cement using two in vivo test methods

The cellular and tissue responses to 3 dental cements were studied by 2 methodologies, the connective tissue implantation technique (CTI), recommended by the ADA, and the peritoneal cavity implantation technique (PCI), which has emerged as a method to quantitatively study the cellular response to implanted materials. A mixed inflammatory cell response consisting of neutrophils and macrophages occurred at most of the time periods for all the cements examined in the CTI study. Similar cell populations, including lymphocytes, were observed with the PCI study using differential staining techniques. The histopathological observations from both procedures were similar. Each cement elicited a chronic foreign body reaction containing few chronic cells and mature fibroblastic activity. The intensity of the observed tissue reactions for each cement, as determined by capsule thickness in the CTI study and the overall cell counts in the PCI study, did not differ significantly with increasing time. The cellular and connective tissue reactions to the zinc hexyl vanillate (ZHV) cement approximated those of zinc oxide-eugenol (ZOE) and zinc phosphate (ZP) cements for both methodologies utilized in this work. While similar histopathological results were obtained for the implantation of cements using both methodologies, the PCI technique offers a more thorough investigation of cellular and tissue responses to implanted materials. In addition to histopathological evaluations, the PCI techniques allows quantitative investigation of the specific cells responding to the implants, and provides a mechanism, using chemical analysis techniques, to quantify the concentration of specific degradative products within the retrieved cells and host tissue. Finally, the results from these 2 methodologies demonstrated the acceptable biological performance of ZHV cement compared with the clinically acceptable ZP and ZOE cement formulations.     

Neurotoxicity of dental amalgam is mediated by zinc

The use of dental amalgam is controversial largely because it contains mercury. We tested whether amalgam caused toxicity in neuronal cultures and whether that toxicity was caused by mercury. In this study, we used cortical cell cultures to show for the first time that amalgam causes nerve cell toxicity in culture. However, the toxicity was not blocked by the mercury chelator, 2,3-dimercaptopropane-1-sulphonate (DMPS), but was blocked by the metal chelator, calcium disodium ethylenediaminetetraacetate (CaEDTA). DMPS was an effective mercury chelator in this system, since it blocked mercury toxicity. Of the components that comprise amalgam (mercury, zinc, tin, copper, and silver), only zinc neurotoxicity was blocked by CaEDTA. These results indicate that amalgam is toxic to nerve cells in culture by releasing zinc. While zinc is known to be neurotoxic, ingestion of zinc is not a major concern because zinc levels in the body are tightly regulated.     

Evaluation of biologic effects of dental materials using four different cell culture techniques.

The cytotoxicity of fresh and 1-day-old silicate cement, composite restorative material and zinc oxide-eugenol cement (ZOE) was tested using human epithelial cells (NCTC 2544) in four different cell culture systems: (1) 51Cr-release from prelabeled cells after incubation for 4 and 24 h in the presence of the materials. (2) Implanting the materials on an agar everlay and visualizing any cytotoxic effects after 24 h by neutral red vital stain. (3) Cell growth during 5 d in the presence of the materials. (4) Colony-forming ability after exposure of the cells for 30 min to medium previously incubated with the materials for 24 h. Freshly prepared and 1-day-old ZOE exhibited a prominent cytotoxic effect in all four systems. A less marked effect was found for the composite material in systems 2, 3, and 4, while silicate cement appeared to be the least toxic material in these three systems. Neither silicate cement nor composite showed any cytotoxic effect in system 1 based on 51Cr-release. It is concluded that the effects obtained by the cell culture techniques did not mimic the reactions obtained when the materials are tested under conditions which reflect their clinical use.     

Determination of pH and calcium ion release provided by pure and calcium hydroxide-containing AHPlus

AIM: To compare in vitro the pH and calcium ion release provided by pure and calcium hydroxide-containing AHPlus. METHOD: Pure and modified AHPlus, the latter containing 5 and 10% (w/w) calcium hydroxide added during spatulation, were used. The material was spatulated and stored in 10 tubes that were 1 cm long and 1.5 mm in diameter, and then immersed in 20 mL deionized water before the materials had set. Ten tubes with zinc oxide and eugenol were used as controls. Four millilitres of water was removed from the flasks after 24 and 48 h, and after 7, 14 and 30 days, and pH and calcium release were measured with a pH meter and by atomic absorption spectrophotometry, respectively. The results obtained at each time point were compared statistically. RESULTS: A more alkaline pH for AHPlus supplemented with 5 and 10% calcium hydroxide was recorded when compared to pure AHPlus; there were significant differences at 14 and 30 days (P<0.05). The results of calcium ion release showed no significant difference between pure AHPlus and zinc oxide plus eugenol (P>0.05). The comparisons between the AHPlus containing 10% calcium hydroxide with AHPlus containing 5% calcium hydroxide, pure AHPlus, zinc oxide plus eugenol demonstrated significant differences (P<0.05) at all periods. The comparisons between AHPlus containing 5% calcium hydroxide with pure AHPlus and zinc oxide plus eugenol demonstrated significant differences (P<0.05) at all periods of evaluation. CONCLUSIONS: The addition of 5 and 10% calcium hydroxide to AHPlus cement favoured a more alkaline pH and greater calcium ion release.     

Nicotine-induced alterations in human primary periodontal ligament and gingiva fibroblast cultures

Various in vivo and in vitro investigations have indicated that tobacco smoking as well as the use of smokeless tobacco products may be important risk factors for the development and severity of inflammatory periodontal disease. The purpose of this study was to determine the cytotoxicity of nicotine by means of human primary oral fibroblast cultures and a permanent cell line. The cytotoxicity of nicotine was evaluated by determination of cell growth, cell membrane integrity, protein content, and alterations of the cytoskeleton. Furthermore, recovery following nicotine exposure was assessed by vital staining (trypan blue). Dose-dependent toxic effects of nicotine were measured within a range of 0.48 mM to 62 mM. Growth of fibroblasts was decreased by nicotine concentrations higher than 7.8 mM. Additionally, the protein content was significantly decreased and cell membranes were damaged. Morphological alterations of microtubules and vimentin filaments were observed at concentrations higher than 3.9 mM. Nicotine-exposed cells revealed atypical shapes and vacuoles. The toxic effects of nicotine became irreversible in the range between 10.5 and 15.5 mM, whereas at lower concentrations cells recovered after the withdrawal of nicotine. Our results confirm clinical oberservations regarding the important role of nicotine as a risk factor in the etiology and progression of periodontal disease.