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Evaluation of the potential toxicity of the polymethyl methacrylate (dental resin) on a cellular model alternate paramecium.


The methacrylic resin is the material of election for the clothes industry of the prosthetic bases. It results from the mixture between a liquid, the methacrylate of methyl and a powder made up of polymethacrylate of methyl and dyes. Polymerization results from a chemical reaction complex during which the macromolecules or polymers are formed starting from a great number of molecules called monomers [6].

The reaction between the monomer and polymer is more or less incomplete, leaving part of the free monomers able to diffuse in the oral medium. This monomer is regarded as poison when its proportion exceeds 0,4% of the product finished [18,15]. Le port of a resin prosthesis can entrained of irritations of the mucous membranes covering the bearing surfaces and of the reactions with over-sensitiveness of the type I or type IV [19,33].

The over-sensitiveness of the type I immediate or anaphylactic is very rare and gives significant functional signs not making it possible to the patient to continue to carry his prostheses. Occurred of the signs is very fast. A differential diagnosis is essential, with a toxic reaction of chemical origin due to certain components of the resin like the dyes and more particularly the monomers [19,36].

The over-sensitiveness of the type cellulaire (IV) delayed seems to be frequent, it corresponds to a prosthetic stomatitis of allergic origin which appears by an erythematic, an erosion of the oral mucous membrane and a feeling of burn on the register [14]. Only the dermatological test (Test patch) will be carried out to draw aside the prosthetic stomatitis of infectious origin [21]. To obtain a rate of reduced monomer, several authors recommend a long cycle of cooking for a polymerization with the Marie bath, which is the most used technique [35].

The technique that we propose to use is polymerization with the microwaves, calling upon an electromagnetic radiation (microwaves of frequency 2450 MHz) who allows shortening, significantly time necessary to cooking of the resins.

The objective of this study is to evaluate under the conditions of laboratory the toxicity of a dental resin containing methyl methacrylate (MELIODENTE) polymerized with the microwaves and to propose an optimum cycle of cooking for a less toxic resin.

Materiel and Methods

1-1. Biological Material:

The biological model used in our work is a unicellular micro organism of the class of cilia; Paramecium's cultivated in mass under strictly controlled conditions. According to the method of Wichterman [39]

1-2. Chemical material:

We carried out resin discs of 2mm thickness and of 1,5mm of diameter (MELIODENT resin), the resin is prepared starting from two different reports/ratios (powder/liquid)(MELIODENT) powders reference: batch 07Ep0029/CE0197;Liquid MELIODENT: batch 013085/CE0197) and polymerized with the microwaves according to two cycles of cooking (the cycle courts 4min to 360 W and the long cycle 7min with 360 W.

1-4.parameters Measured:

1-4-1. kinetics of cell multiplication:

The kinetic growth of the paramecium is carried out according to the method of Saving and et al., [30] by the measurement of the optical density ([lambda] = 600 nm (Jenway 6300)

1-4-2. percentage of answer:

Realized according to the method of Wong and et al., [40], this calculation evaluates the answer of the protist with respect to the dental resin by taking of account the parameter growth. It is based on the following equation:

Percentage of answer = [([N.sub.C] - [N.sub.E])/[N.sub.C]] 100

[N.sub.C]: number of Control cells.

[N.sub.E]: number of treated cells.

The positive values of the percentage of answers indicate an inhibition of the growth while the negative values indicate a stimulation of growth [40].

1-4-3. Proportioning of proteins:

The proteins are quantified according to the method of Bradford [5],

1-4-4. proportioning of the reduced glutathion (GSH):

The rate of glutathione (GSH) is carried out according to the method of Weckberker and Cory [38], whose principle rests to the colorimetric measure of the acid 2-nitro 5-mercapturic, resulting from the reduction of the acid 5-5' dithio-(a)-2-nitrobenzoic (DTNB) by the groupings thiol (-HS) of the glutathion measured with a wavelength of 412 nm.

1-4-5. polarographic Study:

The apparatus used is an electrode with oxygen, (HANSATECH), allowing the measurement of the production or the oxygen uptake by the cells. Its sensitivity makes it possible to detect concentrations of O2 of the order of the nM [10].

1-4-6. Statistical analysis:

The results are presented as mean [+ or -] standard error, the results are compared by non parametric Kruskal-Wallis, with the MINITAB software version 14.0, the level of significance chosen was p <0.05 [9].


2-2. kinetics of growth:

The curves of growths offer quantitative information allowing a reliable analysis of the toxic effect of a given substance.

Figure (1) represents the variations of the growth of the cells treated by the resins (R1 and R2). We note that the presence of the resins R1 and R2 slow down the cell multiplication of the cells treated compared to the pilot cells. This inhibiting effect is very highly significant (for R1 with P = 0.01) and nonsignificant (for R2 with P = 0.05). The comparison between the growth rate of the paramecies during treatment by R1 and R2 reveals differences very highly significant with (p = 0.001).


2-2-2--percentage of response of the paramecium treated by the resin (R1 and R2):

Figures (02) and (03) represent the percentage of response of the paramecium treated by the resin (R1 and R2), We observe a confirmation of the inhibition afterwards of treatment by the two types of resin.



2-3--effect of the resin on the rate of total proteins:

Figures (04) and (05) illustrate the variations of the rate of total proteins at the paramecium treated by R1 and R2. We note that at the treaties by the resin (R1), the rate of total proteins tends to increase in a manner proportions dependent and very highly significant (P = 0.01).


At the treaties by the resin (R2), the rate of total proteins tends to increase in a manner proportions dependent and significant (P = 0.05).


2-4--Effects of the resin on the evolution of the rate of glutathione (GSH):

Figure (06) represents the variations of rate of GSH at the paramecium treated by R1 and R2 We note a reduction highly with very highly significant in the rate of the GSH at the paramecium treated by R1 and R2 with P = 0.01 and P = 0.001). The comparison between the rate of proteins of the paramecium treated by R1 and R2 reveals differences highly with very highly significant with (P = 0.01 and P = 0.001).


2-5--influence of the resin on the respiratory metabolism:

Figure (07) illustrates the effects of the resins R1 and R2 on the respiratory metabolism of the paramecium. We notice that the pilot cells consume approximately 360,003 nmole/ml after 6h of treatment En revenge we note a stimulation of the respiratory metabolism of the cells treated by the resins (R1 and R2), with 380,03 nmole/ml for those treated by resin R1 and 375, 03 nmole/ml for those treated by the resin R2.


This stimulation is very highly significant on the respiratory metabolism of the paramecium treated by the resin R1 and R2, after (6h) of treatment with (P = 0.001).


Salting out in mouth of the monomers remained free after the polymerization of dental materials is responsible for many allergic irritations, reaction, and intoxication and affects inter alia the systems cellular and immunizing, the concentration of the residual monomer varies with the method and the conditions of polymerization [37]. Indeed, several techniques of polymerization of the resins are currently used, in this work we used that which calls upon the technique of the electromagnetic radiation known as polymerization with the microwaves [34,22].

The toxicity of the dental resin (MELIODENTE) is evaluated with various intervals of time: short time (0h with 6h) and long time (24h a72h) on the cell multiplication which is a good indicator of the state of the metabolism of cell [27].

Our results particularly reveal a significant inhibition of the growth of the micro-organisms according to time at the first hours of treatment and cycle of cooking of the resin R1. These results are in agreement with those of Sheridan and et al., [32] which announced that the cytotoxic effect of the resins is more significant at the first hours after polymerization, and decreases thereafter it is the same for work for Einicker-Spangled and et al., [11] ou still of Fukushima and et al., [13]. Ceci lets to us suppose the salting out of toxic residual monomers in the culture medium of the paramecies treated by R1and the toxic impulse of monomers with the interior of the cells like suggest [35]. L' evolution of the kinetics of growth in the presence of R1 and R2 is confirmed by the percentages of answers which is a reliable parameter confirming or cancelling an inhibition of the cell multiplication [3].

In our work, we aveons highlighted a amount-dependent and significant increase at highly significative (R1) in the presence of the resins. These results go in the same direction as those of Rouabhi [29,31] which showed a significant increase in the rate of proteins under the effect of a chemical stress at the paramecium. According to Masaya and et al., [24] the exposure of the micro-organisms to xenobiotic the armature a synthesis amount-dependent on proteins of stress hsp70

On the basis of the principle which any type of chemical stress causes a release of free radicals in the organization [2], a deterioration of the cellular components intervenes when the intensity of this phenomenon increases abnormally and all the cellular components (proteins, glucides...) can be touched [28,31].

In our work, we highlighted a reduction proportions--dependent on the rate of GSH in the presence of R1 and R2, this depletion is due to the mechanism of detoxication unclenched at the cells via the reactions of conjugation with the glutathione [26], for the elimination of xenobiotic the toxic (the residual monomers) out of the cells [20]. Our results go in the same direction as those of Engelmann, [12], Lefbvre and et al., [23] or still those of Chen and et al., [8]; Ha and et al., [16] which stipulate that the direct capture of the oxygenated free radicals, generated by the metabolisation of these xenobiotics is ensured by compounds trappers of radicals or enzymatic systems located in the vicinity of the initial place of production.

The other interesting aspect in our work relates to the evolution of the respiratory metabolism of Paramecium treated by the resins R1 and R2. Our results highlighted a stimulation of the oxygen uptake at the cells treated by the resins thus confirming the assumption of-Lock and et al., (1977). Suggesting the presence of anions toxic radicalizing superoxide's, from where the disturbance of the consumption of [O.sub.2] observed in our work.

Thus, it appears that the resin R1 is more toxic than the R2.Ceci resin leads us to suggest than the long cycle of cooking is advised the most for obtaining a not very toxic resin; our results go in the direction of those of Al Doori and et al., [1], Kedjarune et al., [22], Harrison and Huggett, [17] which confirm that for the traditional resins, plus the cycle of polymerization are long with a high temperature more the rate of residual monomers is weak. This is also valid for the polymerizable resins car (MELIODENT) which we tested and our results go in the same direction as those of Yunus and et al., [41], Blagojevic and et al., [4] and Muster, [25], which noted a reduction in the rate of residual monomers after a long cycle of cooking.


In this work we could show that the selected biological model for our toxicological tests is adapted perfectly to this kind of studies, moreover the method of the immersion of the resin discs supports the contact of xenobiotic with the cells in culture. On another side we confirmed that resin MELIODENT is toxic according to the mode of polymerization used. Indeed more the temperature is raised and the long time of cooking and less the resin is toxic (R2).


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(1) Grara Nedjoud., (1) Bouaaricha Houda., (1) Boucenna Mounir., (1) Atailia Amira., (1) Berrebbah Houria., (1) Djebar Mohamed Reda and (2) Zeriati Chafica

(1) Cellular laboratory of Toxicology, Department of Biology, Faculty of Sciences, Badji Mokhtar University of Annaba, 23000, B.P.12. Algeria.

(2) Department of Dental surgery, Badji Mokhtar University of Annaba, 23000, B.P.12. Algeria.

Grara Nedjoud., Bouaaricha Houda., Boucenna Mounir., Atailia Amira., Berrebbah Houria., Djebar Mohamed Reda and Zeriati Chafica: Evaluation of the potential toxicity of the polymethyl Methacrylate (dental resin) on a cellular model alternate paramecium.

Corresponding Author

Grara Nedjoud., Cellular laboratory of Toxicology, Department of Biology, Faculty of Sciences, Badji Mokhtar University of Annaba, 23000, B.P.12. Algeria.

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Title Annotation:Original Article
Author:Nedjoud, Grara; Houda, Bouaaricha; Mounir, Boucenna; Amira, Atailia; Houria, Berrebbah; Reda, Djebar
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:6ALGE
Date:Apr 1, 2012
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