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.

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.