Evaluation of alternative photoinitiator systems in two-step self-etch adhesive systems.

OBJECTIVE: The aim of this study was to evaluate the effect of different photoinitiator systems on the cell viability and physico-chemical properties of an experimental adhesive resin of a two-step self-etch adhesive system. METHODS: Eight photoinitiators and coinitiators were evaluated, camphorquinone (CQ); ethyl-dimethylamino benzoate (EDAB); diphenyliodonium hexafluorophosphate (DPIHFP); 1,3-benzodioxole (BDO); piperonyl alcohol (AP); 1,3-diethyl-2-thiobarbituric acid (TBA); bisphenyl phosphinic oxide (BAPO); and diphenyl phosphinic oxide (TPO). Seven experimental adhesive resins (Bis-GMA:TEGDMA - 1:1 by wt%) were formulated by varying the initiation systems: RCQ+EDAB (control), RCQ+EDAB+DPHFP, RCQ+BDO, RCQ+AP, RCQ+TBA, RBAPO and RTPO. The cell viability of the different photoinitiators in their isolated form and after being incorporated into the adhesive resins was evaluated using the MTT assay. The degree of conversion within the hybrid layer (DC in situ) was evaluated by micro-Raman spectroscopy; the polymerization kinetics, by FTIR spectroscopy. The water sorption (Wsp) and solubility (Wsl) were calculated by using percentage of gain and loss of mass. Data were analyzed using One-way ANOVA and Kruskal-Wallis tests (α=0.05). RESULTS: When evaluated in their isolated form, the DPIHFP was considered cytotoxic in all concentrations evaluated. When incorporated into and adhesive resin, RCQ+TBA presented higher cell viability values than control and the highest values of DC in situ (p<0.05). Additionally, the use of CQ+TBA showed a higher cell viability when compared with the conventional CQ+EDAB system. SIGNIFICANCE: The pair CQ+TBA could be potentially useful in the development of materials with improved biocompatibility.

Surface detail reproduction and dimensional accuracy of molds: influence of disinfectant solutions and elastomeric impression materials.

This study compared the surface detail reproduction and dimensional accuracy of molds after disinfection using 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to those of molds that were not disinfected, for four elastomeric impression materials: polysulfide (Light Bodied Permlastic), polyether (Impregum Soft), polydimethylsiloxane (Oranwash L) andpolyvinylsiloxane (Aquasil Ultra LV). The molds were prepared on a matrix by applying pressure, using a perforated metal tray. The molds were removed following polymerization and either disinfected (by soaking in one of the solutions for 15 minutes) or not disinfected. The samples were thus divided into 16 groups (n=5). Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy to assess the 20-µm line over its entire 25 mm length. The dimensional accuracy results (%) were subjected to analysis of variance (ANOVA) and the means were compared by Tukey's test (a=5%). The 20-µm line was completely reproduced by all elastomeric impression materials, regardless of disinfection procedure. There was no significant difference between the control group and molds disinfected with peracetic acid for the elastomeric materials Impregum Soft (polyether) and Aquasil Ultra LV (polyvinylsiloxane). The high-level disinfectant peracetic acid would be the choice material for disinfection.

Este estudo comparou a reprodução de detalhes da superficie e estabilidade dimensional de moldes obtidos após desinfecção utilizando hipoclorito de sódio 2%, digluconato de clorexidina 2%, ou ácido peracético 0,2% a moldes que não foram desinfetados com quatro elastomeros: polissulfeto (Light Bodied Permlastic), polieter (Impregum Soft), silicona reação por condensação (Oranwash L) e silicona reação por adição (Aquasil Ultra LV). Os moldes foram preparados sobre matriz contendo linhas de 20, 50 e 75 µm realizado sob pressão com moldeira de metal perfurada. Os moldes foram removidos após a polimerização e desinfetados (utilizando uma das soluções por imersão, armazenados em frascos fechados durante 15 minutos) ou não desinfetados. Assim, as amostras foram divididas em 16 grupos (n=5). A reprodução detalhes da superficie e a precisão dimensional foram avaliadas usando microscopia óptica na linha 20 µm com 25 mm de comprimento, de acordo com a norma ISO 4823. Os resultados de precisão dimensional (%) foram submetidos a análise de variancia (ANOVA) e as médias comparadas pelo teste de Tukey com 5% de nivel de significancia. A linha de 20 µm foi completamente reproduzida por todos os elastomeros, independentemente do processo de desinfecção. Nao houve diferenga estatisticamente significativa entre o grupo controle e moldes desinfetados com acido peracético para os elastomeros Impregum Soft (polieter) e Aquasil Ultra LV (silicona reação por adição). O desinfetante de alto nivel ácido peracético seria o material de escolha para a desinfecção.

Surface detail reproduction and dimensional accuracy of molds: influence of disinfectant solutions and elastomeric impression materials / Reprodução de detalhes da superfície e estabilidadedimensional de moldes: influência das soluçõesdesinfetantes e elastômeros

This study compared the surface detail reproduction anddimensional accuracy of molds after disinfection using 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to those of molds that were not disinfected, forfour elastomeric impression materials: polysulfide (Light Bodied Permlastic), polyether (Impregum Soft), polydimethylsiloxane(Oranwash L) and polyvinylsiloxane (Aquasil Ultra LV). Themolds were prepared on a matrix by applying pressure, using aperforated metal tray. The molds were removed followingpolymerization and either disinfected (by soaking in one of thesolutions for 15 minutes) or not disinfected. The samples werethus divided into 16 groups (n=5). Surface detail reproductionand dimensional accuracy were evaluated using opticalmicroscopy to assess the 20 ­µm line over its entire 25 mm length. The dimensional accuracy results (%) were subjectedto analysis of variance (ANOVA) and the means were comparedby Tukey’s test (α=5%). The 20 ­µm line was completelyreproduced by all elastomeric impression materials, regardlessof disinfection procedure. There was no significant difference between the control group and molds disinfected with peraceticacid for the elastomeric materials Impregum Soft (polyether)and Aquasil Ultra LV (polyvinylsiloxane). The high­leveldisinfectant peracetic acid would be the choice material for disinfection.

Este estudo comparou a reprodução de detalhes da superfície e estabilidade dimensional de moldes obtidos após desinfecção utilizando hipoclorito de sódio 2%, digluconato de clorexidina 2%, ou ácido peracético 0,2% a moldes que não foram desinfetados com quatro elastômeros: polissulfeto (Light Bodied Permlastic), polieter (Impregum Soft), silicona reação porcondensação (Oranwash L) e silicona reação por adição (Aquasil Ultra LV). Os moldes foram preparados sobre matriz conten dolinhas de 20, 50 e 75 µm realizado sob pressão com moldeirade metal perfurada. Os moldes foram removidos após a polimerização e desinfetados (utilizando uma das soluções porimersão, armazenados em frascos fechados durante 15 minutos)ou não desinfetados. Assim, as amostras foram divididas em 16grupos (n=5). A reprodução detalhes da superfície e a precisão dimensional foram avaliadas usando microscopia óptica na linha 20 µm com 25 mm de comprimento, de acordo com a norma ISO 4823. Os resultados de precisão dimensional (%) foram submetidos à análise de variância (A NOVA) e as médias comparadas pelo teste de Tukey com 5% de nível de significância. A linha de 20 µm foi completamente reproduzida por todos os elastômeros, independentemente do processo de desinfecção. Não houve diferença estatisticamente significativa entre o grupo controle e moldes desinfetados com acido peracético para os elastômeros Impregum Soft (polieter) e Aquasil Ultra LV (siliconareação por adição). O desinfetante de alto nível ácido peracético seria o material de escolha para a desinfecção.

The influence of concentration of HEMA on degree of conversion and cytotoxicity of a dental bonding resin.

BACKGROUND: This study evaluated the influence of 2-hydroxyethyl methacrylate (HEMA) on the degree of conversion (DC) and cytotoxicity of a dental bonding resin (DBR). METHODS: A monomer mixture based on 61.9 wt% of bisphenol A glycidyl methacrylate (Bis-GMA), 36.9 wt% of triethylene glycol dimethacrylate (TEGDMA), and photoactivated using a binary system based on camphoroquinone (0.4 wt%) and ethyl 4-dimethylamine benzoate (0.8 wt%) was used as DBR. Different groups were obtained with addition of HEMA in crescent concentrations. DC was accessed by Real time Fourier Transform infrared spectroscopy. The cytotoxicity was evaluated with MTT assay. The DC and cytotoxicity were analyzed by one-way ANOVA followed by Tukey's Test (P<0.05). RESULTS: A decrease in the DC was observed in the group with higher amount of HEMA. All tested-extracts were cytotoxic and there was an increased cytotoxic effect with higher HEMA addition. CONCLUSIONS: Higher amount of HEMA in the DBR resulted in adverse effects, with more cell toxicity and lower degree of conversion.

BAPO as an alternative photoinitiator for the radical polymerization of dental resins.

OBJECTIVES: This study evaluated the performance of phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO) as an alternative photoinitiator in the polymerization kinetics (PK), flexural strength (σ) and elastic modulus (E) of a model dental resin. METHODS: A monomer mixture based on Bis-GMA and TEGDMA was used as model dental resin. Initially a screening was performed to evaluate BAPO concentrations (0.125, 0.25, 0.50, 1, 2, and 4 mol%). Photoinitiator systems were formed with the combination of camphorquinone (CQ), ethyl-dimethylamino benzoate (EDAB), diphenyliodonium hexafluorophosphate (DPIHFP), and BAPO. Groups with unitary photoinitiator systems (BAPO and CQ), binary (BAPO+EDAB, BAPO+DPIHFP and CQ+EDAB), ternary (BAPO+CQ+EDAB, BAPO+CQ+DPIHFP, BAPO+EDAB+DPIHFP and CQ+EDAB+DPIHFP) and quaternary (BAPO+CQ+EDAB+DPIHFP) were formulated for evaluation. Real-time Fourier transform infrared spectroscopy was used to investigate the PK and test mini-bending to evaluate σ and E. RESULTS: When only CQ was used, a slow polymerization reaction was observed and a lower monomer conversion. When only BAPO was used as photoinitiator an increase in the polymerization rate was observed and conversion was higher than CQ+EDAB. The ternary system (BAPO+EDAB+DPIHFP) showed the highest polymerization and conversion rate, in short photo-activation time. SIGNIFICANCE: BAPO it is a potential photoinitiator for the photopolymerization of dental materials.

2-hydroxyethyl methacrylate as an inhibitor of matrix metalloproteinase-2.

This study evaluated the effect of different concentrations of 2-hydroxyethyl methacrylate (HEMA) on the inhibition of matrix metalloproteinase-2 (MMP-2) in vitro. Mouse gingival explants were cultured overnight in Dulbecco's modified Eagle's minimal essential medium, following which the expression of secreted enzymes was analyzed by gelatin zymography and the effects of different amounts of HEMA on enzyme activity were investigated. The gelatinolytic proteinases present in the conditioned media were characterized as being matrix metalloproteinases (MMPs) by means of specific chemical inhibition. The MMPs present in the conditioned media were identified, using immunoprecipitation, as MMP-2. Three major bands were detected in the zymographic assays and were characterized, according to their respective molecular weights, into the following forms of MMP-2: zymogene (72 kDa), intermediate (66 kDa), and active (62 kDa). All forms of MMP-2 were inhibited by HEMA in a dose-dependent manner, implying that MMP-2 may be inhibited by HEMA in vivo.

Teor de flúor e propriedades erosivas dos sucos de frutas naturais concentrados / Fluoride levels and erosive properties of natural concentrated fruit juices

A preocupação com uma dieta saudável tem ocasionado aumento no consumo de frutas e sucos naturais. Orientações quanto à ingestão de sucos ácidos são extremamente importantes na prevenção e tratamento de lesões de erosão dental. O objetivo do presente trabalho foi determinar o pH e a concentração de fluoretos em sucos concentrados e diferentes frutas comercializadas na cidade de Pelotas-RS. Foram selecionadas amostras de sete frutas: maçã, laranja, maracujá, uva, melão, limão e abacaxi. As amostras foram processadas em triplicata. As frutas foram trituradas em mixer Walita (modelo HL 3235) para obtenção dos sucos e, em seguida, os mesmos foram centrifugados em centrífuga Sigma (modelo 4K15), a 19ºC e a 5100rpm por 10 minutos. As análises dos sucos concentrados foram feitas no Laboratório de Determinação de Fluoretos do Departamento de Bioquímica da UFPel. A mensuração do pH e a determinação do teor de flúor foram realizadas com aparelho potenciométrico microprocessado (ANALION - AN 2000). Os resultados mostraram que o pH dos diferentes sucos foi de: 2,25 (limão); 2,69 (maracujá); 3,30 (abacaxi); 3,32 (laranja); 3,88 (maçã); 4,14 (uva) e 6,04 (melão). O teor de flúor iônico livre nas frutas não ultrapassou 0,04ppm. Com base na metodologia empregada, concluiu-se que a maioria dos sucos de frutas testados apresentou potencial de desmineralização dos tecidos dentários e o teor de flúor presente em tais sucos foi inexpressivo