Effects of soft denture liners on L929 fibroblasts, HaCaT keratinocytes, and RAW 264.7 macrophages.

The effects of six soft liners (Ufi Gel P (UG), Sofreliner S (SR), Durabase Soft (D), Trusoft (T), Coe Comfort (CC), and Softone (ST)) on L929, HaCat, and RAW 264.7 cells were investigated. Eluates (24 and 48 h) from the materials were applied on the cells and the viability, type of cell death, and morphology were evaluated. Cells were also seeded on the specimens' surfaces (direct contact) and incubated (24 or 48 h), and viability was analyzed. Controls were cells in culture medium without eluates or specimens. For cell viability, no significant differences were found among materials or between extraction periods, and the liners were noncytotoxic or slightly cytotoxic. Morphology of RAW 264.7 cells was altered by the 24 h eluates from CC and D and the 48 h eluates from SR, CC, and D. The 24 and 48 h eluates from all materials (except T) increased the percentages of L929 necrotic cells. For direct contact tests, the lowest cytotoxicity was observed for UG and SR. Although eluates did not reduce viability, morphology alterations and increase in necrosis were seen. Moreover, in the direct contact, effects on viability were more pronounced, particularly for D, T, CC and ST. Thus, the use of UG and SR might reduce the risk of adverse effects.

Cytotoxicity of hard and soft denture lining materials.

The cytotoxicity of nine soft and hard lining materials (Mollosil Plus, Ufi Gel SC, Visco-gel, Molloplast-B, GC Tissue Conditioner, Vertex Rapid Simplified, GC Reline Hard, Vertex Self-Curing, Ufi Gel hard C) was evaluated using human gingival fibroblasts (HGFs). Twelve disk samples per lining material were prepared and incubated for 24, 48, 72, and 96 h. Cytotoxicity of each lining material's extract on cultured HGFs was measured using XTT assay. Data were analyzed using one-way ANOVA, post hoc Dunnett's T3 and Bonferroni tests at a significance level of p<0.05. At all incubation periods, all the hard lining materials (Vertex-SC, GC Reline Hard, Vertex-RS, and Ufi Gel hard C) showed cell viability higher than 90%. Among the soft lining materials, although there were no significant differences in cell viability among the different incubation periods for each lining material (p>0.05), autopolymerized acrylic-based GC Tissue Conditioner showed significantly lower cell viability than the other soft lining materials at each incubation period. Among the hard lining materials, there were no significant differences both among the materials and across all incubation periods for each lining material (p>0.05). In conclusion, all soft and hard liners exhibited good biocompatibility regardless of incubation time, except for GC Tissue Conditioner.

Cytotoxicity of monomers, plasticizer and degradation by-products released from dental hard chairside reline resins.

OBJECTIVES: The aim of this study was to evaluate the cytotoxic effect of the monomers isobutyl methacrylate (IBMA) and 1,6-hexanediol dimethacrylate (1,6-HDMA), the plasticizer di-n-butyl phthalate (DBP), and the degradation by-products methacrylic acid (MA) and benzoic acid (BA) on L929 cells. Based on previous investigations on the release of these compounds from hard chairside reline resins, a range of concentrations (micromol/L) were selected for the cytotoxicity tests (IBMA, 5.49-1406.57; 1,6-HDMA, 1.22-39.32; DBP, 1.12-143.8; MA, 9.07-581; BA, 3.19-409). METHODS: Cytotoxic effects were assessed using MTT and (3)H-thymidine assays after the cells had been exposed to the test compounds at the given concentrations for 24 h. Cytotoxicity was rated based on cell viability relative to controls (cells exposed to medium without test substances). RESULTS: DNA synthesis activity was inhibited by all compounds. Mitochondrial dehydrogenase activity decreased in cells treated with monomers, plasticizer and MA by-product, whereas no cytotoxic effect was observed on contact with BA at the majority of concentrations tested. The ranges of suppression for (3)H-thymidine assay were: IBMA, 25-95%; 1,6-HDMA, 95-98%; DBP, 40-98%; MA, 97-99%; BA, 54-71%. For MTT assay, the ranges of suppression were: IBMA, 0-96%; 1,6-HDMA, 26-89%; DBP, 17-80%; MA, 52-66%; BA, 0-27%. The (3)H-thymidine assay was more sensitive than the MTT assay. SIGNIFICANCE: This study evaluated the cytotoxicity of a wide range of concentrations of monomers (IBMA and 1,6-HDMA), plasticizer (DBP) and degradation by-products (MA and BA), including those expected to be released from hard chairside reline resins. The differences observed in the cytotoxicity of these compounds, along with other properties, may assist the dental practitioners in the selection of reline materials with improved service life performance and low risk of adverse reactions in patients who wear relined dentures.

Mechanical properties and cytotoxicity of experimental soft lining materials based on urethane acrylate oligomers.

The purpose of this investigation was to determine whether experimental light-curing soft lining materials (ESLMs) based on commercially available urethane acrylate oligomers (UA-160TM, UV-3200B, UV-3500BA, and UV-3700B) are suitable for clinical use by measuring their viscosity, compressive modulus, Shore A hardness, tensile strength, adhesive strength, and cytotoxicity. The viscosities of the four ESLMs at 25 degrees C were 10.5 Pa.s, UV-3500BA; 144.0 Pa.s, UA-160TM; 328.8 Pa.s, UV-3700B; and 1079.7 Pa.s, UV-3200B. Polymerized UV-3700B was very soft, whereas the softness of the other ESLMs was similar to that of conventional soft lining materials. No significant difference in adhesive strength was observed between UV-3500BA and UV-3700B at 1 day and those at 12 months. Cytotoxicity was measured by a MTT-based assay using HeLa S3 and Ca9-22 cells. UV-3200B and UV-3700B oligomers and all four polymerized ESLMs showed cell viability over 95.2% (p < 0.05).

Residual monomer: effect on tensile bond strength of silicone resilient liners / Monômero residual: o efeito na resistência de união de reembasadores resilientes de silicone

Adhesion failure between silicone resilient liner materials and denture base resin is a common problem found in clinical practice. Bond failure results in localized unhygienic conditions at the debonded regions and causes functional failure of the prosthesis. The aim of this study was to evaluate the tensile bond strength of 2 resilient liners (auto-polymerized silicone - Permafix® and heat-polymerized silicone - Permaflex®) under the influence of a residual monomer methylmethacrylate ([MMA]R) concentration. Two polymethyl methacrylate (PMMA) specimens were prepared by implementing brass dies by means of a 3 mm thick spacer in a denture flask. Specimens (20 X 10 X 3 mm) were made by processing the resilient liners against the polymerized PMMA blocks. After polymerization, the brass spacer was removed from the mold, the PMMAblocks were trimmed, and the bonding surfaces were smoothed. The PMMA blocks were placed back into the molds and resilient liners were packed into the space provided by the brass spacer, followed by trial packing and polymerization according to manufacturer instructions. Twenty specimens...

Falha na união entre reembasadores resilientes de silicone e base acrílica da prótese é um problema encontrado na prática clínica. A falha na união resulta em condições anti-higiênicas localizadas em regiões que apresentam descolamento, além de causar perda de função das próteses. O objetivo deste trabalho foi avaliar a resistência de união de 2 reembasadores resilientes de silicone (autopolimerizável - Permafix® and termopolimerizável - Permaflex®) sob a influência da concentração do monômero residual metilmetacrilato ([MMA]R). Duas amostras de polimetilmetacrilato (PMMA) foram obtidas por meio da inclusão de matrizes metálicas separadas por um espaçador com 3mm de espessura em mufla. As amostras (20 X 10 X 3 mm) foram obtidas processando o material resiliente contra os blocos de PMMA polimerizados. Após a polimerização, removeu-se o espaçador, submeteram-se os blocos ao processo de acabamento, sendo as superfícies de união alisadas. Os blocos foram recolocados no molde e o material resiliente condensado no local...

Cytotoxicity of hard chairside reline resins: effect of microwave irradiation and water bath postpolymerization treatments.

PURPOSE: To evaluate the influence of water bath and microwave postpolymerization treatments on the cytotoxicity of 6 hard reline acrylic resins. MATERIALS AND METHODS: The materials tested were Tokuso Rebase Fast (TR), Ufi Gel Hard (UGH), Duraliner II (D), Kooliner (K), New Truliner (NT), and Light Liner (LL). LL resin was additionally tested with an air-barrier coating (LLABC). Nine disks of each material (10 x 1 mm) were made and divided into 3 groups: group 1 (no postpolymerization treatment); group 2 (postpolymerization in microwave oven); group 3 (postpolymerization in water bath at 55 degrees C for 10 minutes). L929 cells were cultured in 96-well plates and incubated for 24 hours in Eagle's medium. Eluates prepared from the disks or medium without disks (control) replaced the medium. Cytotoxicity was assessed by both dehydrogenase succinic activity (MTT) assay and incorporation of radioactive 3H-thymidine assay. Tests were carried out in quadruplicate and repeated twice. Differences between groups were determined by analysis of variance with Tukey multiple-comparison intervals (alpha = .05). RESULTS: For MTT assay, the postpolymerization treatments had no effect on the cytotoxicity of all materials (P > .05). For 3H-thymidine assay, the postpolymerization treatments significantly decreased the cytotoxicity of UGH (P < .05). The cytotoxicity of K, NT, LL, and LLABC increased after microwave irradiation (P < .05). TR, NT, and LLABC showed an increase in cytotoxicity after water bath (P < .05). CONCLUSION: When assessed by MTT assay, the cytotoxicity of the materials was not affected by postpolymerization treatments. 3H-Thymidine assay showed that the cytotoxicity of the resins was not improved by the postpolymerization treatments, with the exception of UGH.

Cytocompatibility and viscoelastic properties of phthalate ester-free tissue conditioners.

We prepared prototype phthalate ester-free tissue conditioners (PFT) from a powder of poly(ethyl methacrylate) and a mixture of several liquids, including di-n-butyl sebacate, benzyl benzoate (BB), and ethanol. The estrogenic activities of the liquids in the PFT were measured by an E-screen assay. We also assessed the cytotoxicity of the prototype and commercial tissue conditioners against a living skin equivalent. Finally, the viscoelastic properties were determined by measuring the rubber hardness and initial flow, while the effect of the mixing liquid on the mechanical properties of a denture resin was assessed by three-point bending test. PFT did not show any estrogenic activity and displayed a low or a similar level of cytotoxicity as the conventional materials. The viscoelastic properties and the effect of the mixing liquid on mechanical properties were influenced by the quantity of BB present in the mixing liquid. The prototype is therefore a reasonable PFT candidate.

Estrogenic activity of tissue conditioners in vitro.

OBJECTIVES: In order to assess the estrogenic activities of plasticizers used in tissue conditioners and four commercial tissue conditioners, we carried out in vitro tests. METHODS: Seven plasticizers and two metabolites were diluted to concentrations ranging from 10(-9) to 10(-4)M. Four commercial tissue conditioners were also diluted to concentrations ranging from 2 x 10(-8) to 2 x 10(-3)g/ml. Estrogenic activities were tested by the E-screen test using MCF-7 cells. When estrogen is present, the cells proliferate. Instead of counting the cells or nuclei directly, cell numbers were assessed by measurement of the total protein content using the sulforhodamine B assay. The liquid compositions of the four commercial tissue conditioners were examined by high-performance liquid chromatography. RESULTS: n-Butyl benzyl phthalate, dibutyl phthalate, n-butyl phthalyl n-butyl glycolate, di-2-ethylhexyl phthalate and benzyl salicylate significantly increased proliferation of MCF-7 cells. The remaining two plasticizers, di-2-ethylhexyl adipate and benzyl benzoate, as well as two metabolites of dibutyl phthalate and di-2-ethylhexyl phthalate, i.e. monobutyl phthalate and mono-2-ethylhexyl phthalate, respectively, did not increase proliferation of MCF-7 cells at the concentrations tested. Four commercial tissue conditioners, Coe comfort (CC), Tissue Conditioner (TC), Hydro Cast (HC) and Denture Soft (DS) II, significantly increased proliferation of MCF-7 cells. HPLC data revealed the commercial products contained plasticizers: benzyl benzoate and dibutyl phthalate in CC, dibutyl phthalate in TC, n-butyl benzyl phthalate in HC and n-butyl phthalyl n-butyl glycolate in DS II. SIGNIFICANCE: Except for benzyl benzoate and di-2-ethylhexyl adipate, the plasticizers tested showed estrogenic activity. The four commercial tissue conditioners tested also showed estrogenic activity, and HC showed especially strong estrogenicity.

Microleakage study of various soft denture liners by autoradiography: effect of accelerated aging.

STATEMENT OF PROBLEM: The longevity of soft denture liners is a major clinical problem. Debonding of the soft liner from the denture base material is one of the factors that influence their longevity. Debonding of the soft liner can be attributed to microleakage at the interface. PURPOSE: This study investigated microleakage at the interface of various soft liners and base materials. MATERIALS AND METHOD: Six soft liners were investigated. Forty specimens of each material in disk form (10 mm in diameter, thickness of approximately 4 mm) were prepared. Twenty specimens of each material were stored in an accelerated weathering tester for 900 hours. For 2 days, all disks were immersed in (45)Ca radioisotope solution, then they were embedded in acrylic resin blocks and sectioned longitudinally. Autoradiographic imaging was used to determine microleakage at the interface of the soft liners and their bases. RESULTS: Significant differences between nonaged materials were found (P<.05).The difference between Molloplast B and Mucopren (silanized) was not significant (P<.05). Differences among aged materials were significant (P>.05). Differences between Mucopren (nonsilanized), Mucopren (silanized), and Ufigel P-Tokuyama were not significant (P<.05). Significantly decreased microleakage characteristics were determined for Molloplast B, Mucopren (nonsilanized) and Ufigel P liners after aging. CONCLUSION: Microleakage of Mucopren and Molloplast B lining materials was the lowest. However, the microleakage of Flexor and Simpa was the highest. The aging process did not significantly affect the microleakage characteristics of the Simpa, Flexor, Mucopren (silanized), or Tokuyama materials. Molloplast B, Mucopren (nonsilanized), and Ufigel P materials should significantly decrease microleakage properties after aging.

Influência do reembasamento de moldes no comportamento morfodimensional de troquéis obtidos a partir de diferentes materiais elastoméricos / Influence of behavior of molds obtained from a relined impression technique using different elastomeric materials

O objetivo do presente trabalho foi avaliar o comportamento morfodimensional de moldes obtidos pela técnica de reembasamento de moldagem, utilizando materiais à base de polissulfeto, silicona de reaçäo por adiçäo e poliéter, comparativamente à técnica convencional simples com os mesmos materiais, por meio da análise do desajuste de uma coroa metálica de referência ou de mediçäo junto aos troquéis de gesso tipo IV que foram obtidos a partir dos diferentes materiais e técnicas de moldagem. Para possibilitar a operacionalizaçäo das moldagens, utilizou-se um dispositivo especial que permitiu a padronizaçäo sequencial das diferentes etapas para obtençäo dos moldes, tanto pela técnica convencional simples como a de reembasamento. Moldeiras individuais de resina acrílica foram confeccionadas para permitir uma espessura uniforme de 2,5 milímetros ao redor do troquel metálico, que simulava um preparo tipo coroa total. Os diferentes materiais de moldagem foram proporcionados por peso, manipulados por tempo de 30 segundos em laboratório com controle de temperatura e umidade, aplicados no troquel metálico e moldeira individual, realizando-se em seguida a moldagem simples. Para reembasamento dos moldes foi realizado previamente um alívio interno a partir da primeira impressäo...

In vitro evaluation of Candida albicans adherence to soft denture-lining materials.

The adherence of Candida albicans to seven commercial soft denture-lining materials was studied in vitro with BCA protein assay reagent. A good correlation was observed between the amount of protein in yeast cells and the number of yeasts (r = 0.993, p < 0.01), and it was revealed that the adherence of C. albicans to bare surfaces of these soft denture-lining materials correlated well with their relative hydrophobic properties (r = 0.905, p < 0.01); thus there was consistency with the thermodynamic theory. These results combined corroborated the accuracy of this method. To know the effect of pellicle on fungal adherence, the adherence of C. albicans to saliva-coated samples was examined. It was revealed that neither the amount of protein adsorbed by substrates nor the adherence of yeast to saliva-coated substrates correlated with the relative hydrophobic properties of these samples, suggesting that factors other than hydrophobic interaction play an important role in the adherence of C. albicans to pellicle-coated soft liners and tissue conditioners.

[Studies on the cytotoxicity of temporary relining materials in clinical use]. / Untersuchungen zur Zytotoxizität klinisch verwendeter temporärer Unterfütterungsmaterialien.

Temporary relining materials and surgical packs placed in a very intimate, direct contact to the adjacent epithelia or even wound surfaces are frequently used in dental and even more so in maxillofacial treatment procedures. Most of these materials, however, are not designed for this purpose; the results are inflammations and irritations. This study focussed on the cytotoxicity of the most frequently used temporary relining materials using the Erlangen ciliate test. This test method has been frequently used in various situations to determine the cytotoxic and cytostatic properties of substances and materials. It is based on liquid pure cultures of the eukaryotic monocellular organism "Tetrahymena piriformis". The sensitivity of these ciliates to cytotoxic noxae is rather similar to that of human and animal tissue cultures. Considerable differences in cytotoxicity have been observed.