Determination of residual monomer content in dental acrylic polymers and effect after tissues implantation

Abstract

The aim of the present study was to determine the content of residual monomer methyl methacrylate (MMA) in cold and hot polymerized poly(methyl methacrylate) (PMMA), both widely applicable in dentistry, by using MHE-GC-MS (multiple headspace extraction analysis by gas chromatographymass spectrometry) in combination with GC-FID (gas chromatography with flame-ionization detection). The samples of PMMA were obtained by free-radical polymerization of MMA at room temperature (cold polymerized PMMA) and at 100 C (hot polymerized PMMA), according to the manufacturer's instructions. The MHE-GC-MS method consisted of ten successive extractions of MMA from the polymerized samples. According to the constructed calibration curve, the content of residual MMA in PMMA samples (mg MMA /g PMMA ) was determined. Intramuscular implantation of sample materials was performed in experimental animals (rats) in order to demonstrate potential adverse effects of the unpolymerized residual reactants to the tissue in direct contact with polymeric implants. The content of residual monomer in cold polymerized PMMA was higher (15.75 mg MMA/ g PMMA ) in comparison to hot polymerized PMMA (10.96 mg MMA/ g PMMA ). The implanted samples of cold-polymerized acrylic resin showed intense inflammatory response of the surrounding tissue. According to the obtained results, hot polymerized PMMA is safer for use in dentistry.

The effect of cooling procedures on monomer elution from heat-cured polymethyl methacrylate denture base materials

“…[9][10][11] These species, such as methyl methacrylate (MMA), dimethacrylate (crosslinking) parent monomers, catalysts or formaldehyde are released after short intraoral exposure periods, 12,13 whereas hydrolytic or biodegradation byproducts are released after long intraoral exposure. 10,11,[14][15][16] Since MMA is the main eluent from heat-cured PMMA denture base resins, many laboratory methods have been developed to quantify residual MMA monomer in the polymerized materials, such as infrared spectroscopy, 17 gas chromatography (GC), [18][19][20] high-performance liquid chromatography (HPLC) [21][22][23][24][25][26] and ultraviolet spectrophotometry. 27,28 From these methods, the chromatographic analyses offer higher detection and quantification limits.…”

“…It has been found that an increased MMA/PMMA ratio leads to an increased amount of residual MMA in the set material, 10 with heat-cured materials possessing less residual monomer than the self-cured. 16,21 Furthermore, studies show that many procedures can reduce the MMA concentration, such as choosing a curing temperature of 100°C, 5,11,29 extending the polymerization time, [29][30][31] implementing a post-polymerization regime at 55°C for 60 min by exposure to microwave irradiation 24 or by smearing acrylic resin with a light-cured coating. 32 Recently, it has been documented that the cooling procedures of the processing flasks affect some mechanical properties of heat-cured denture base PMMA materials, 33 which may be assigned to post-curing reactions.…”

Factors Affecting Sorption and Solubility of Denture Base Acrylic Materials: A Review

“…The residual monomer content present in cold polymerised PMMA was higher than that of heat polymerised PMMA, with cold polymerised material also showing a greater inflammatory response of soft tissue. Tuna et al [4] noted that as the primary difference between heatand self-cured materials is the liquid-to-powder ratio, and taking the study by Kostić et al [22] into account, it can be confirmed that the amount of unreacted monomer present in the material after polymerisation directly affects the degree of solubility expressed by the material. These observations may not only be as a result of different liquid-to-powder ratios, as both Tuna et al [4] and Kostić et al [22] compared the heat-cure acrylic to self-cure acrylic.…”

“…Tuna et al [4] noted that as the primary difference between heatand self-cured materials is the liquid-to-powder ratio, and taking the study by Kostić et al [22] into account, it can be confirmed that the amount of unreacted monomer present in the material after polymerisation directly affects the degree of solubility expressed by the material. These observations may not only be as a result of different liquid-to-powder ratios, as both Tuna et al [4] and Kostić et al [22] compared the heat-cure acrylic to self-cure acrylic. Heat-cure and self-cure acrylics do not only have different liquid-to-powder ratios, but different activators and polymerisation procedures as well.…”

“…Tuna et al [4] investigated the sorption and solubility of various acrylic resins and their results indicated that heat-cured acrylic resins had lower solubility values than most of the self-cured acrylic resins. In a similar study, Kostić et al [22] investigated the residual monomer content present in dental acrylic polymers and its effect on tissue after implantation. The materials used in that study were Triplex Cold and -Hot from Ivoclar Vivadent™, with a liquid to powder ratio of 10ml:13g and 10ml:23.4g respectively.…”