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1.
Materials (Basel) ; 14(19)2021 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-34640263

RESUMO

Polycarbonates are polymers of bisphenol A (BPA), a well-known endocrine disruptor. This study evaluated the release of BPA from polycarbonate crowns that were (1) milled from Temp Premium Flexible (ZPF, Zirkonzahn, Italy) or Tizian Blank Polycarbonate (TBP, Schütz Dental, Germany), or (2) 3D-printed (Makrolon 2805, Covestro, Germany). Commercial prefabricated polycarbonate crowns (3M, USA) and milled poly(methyl methacrylate) (PMMA) crowns (Temp Basic, Zirkonzahn, Italy) were included for comparison. The crowns were stored at 37 °C in artificial saliva (AS) or methanol, which represented the worst-case scenario of BPA release. Extracts were collected after 1 day, 1 week, 1 month and 3 months. BPA concentrations were measured using liquid chromatography-tandem mass spectrometry. The amounts of released BPA were expressed in micrograms per gram of material (µg/g). After 1 day, the highest amounts of BPA were measured from milled polycarbonates, TBP (methanol: 32.2 ± 3.8 µg/g, AS: 7.1 ± 0.9 µg/g) and ZPF (methanol 22.8 ± 7.7 µg/g, AS: 0.3 ± 0.03 µg/g), followed by 3D-printed crowns (methanol: 11.1 ± 2.3 µg/g, AS: 0.1 ± 0.1 µg/g) and prefabricated crowns (methanol: 8.0 ± 1.6 µg/g, AS: 0.07 ± 0.02 µg/g). Between 1 week and 3 months, the average daily release of BPA in methanol and AS decreased below 2 µg/g and 0.6 µg/g, respectively. No BPA was released from PMMA in AS, and the cumulative amount released in methanol was 0.2 ± 0.06 µg/g. In conclusion, polycarbonates could be a relevant source of BPA, but the current tolerable daily intake of BPA (4 µg/kg body weight) should not be exceeded.

2.
J Mech Behav Biomed Mater ; 115: 104295, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33412405

RESUMO

The bonding performance of dental adhesives is most frequently evaluated using the micro-tensile bond strength (µTBS) test. Despite lacking evidence, peripheral specimens are often discarded to avoid regional variability. This study, therefore, examined whether µTBS to central and peripheral dentin differed. Dentin surfaces of extracted human molars were bonded with various self-etch adhesives, built up with a resin composite, cut into beams, and stressed in tension. Failure mode was classified as adhesive, cohesive in dentin, or other using scanning electron microscopy. Since cohesive failures in dentin were frequent and could confound µTBS results, the data from central/peripheral dentin were analyzed using a Weibull competing risk (CR) model distinguishing failure modes, and its outcomes were compared to a conventional failure mode non-distinguishing Weibull model. Based on the strength data of cohesively failed specimens, the CR model also estimated the strength of dentin. For comparison, the ultimate tensile strength (UTS) of dentin was measured in both regions. The conventional model suggested that peripheral µTBS was higher than central µTBS. Conversely, the CR model disclosed no significant difference in µTBS between the regions but indicated a higher strength of peripheral dentin. This finding was confirmed by UTS measurements, and further supported by the significantly higher incidence of cohesive failures in central dentin. Therefore, peripheral specimens can be used in the µTBS test as well as central ones, but a CR model should be used for statistical analysis if cohesive failures in dentin are frequent, as the strength of peripheral dentin is higher.


Assuntos
Colagem Dentária , Adesivos Dentinários , Resinas Compostas , Dentina , Humanos , Teste de Materiais , Cimentos de Resina , Resistência à Tração
3.
Dent Mater ; 36(12): 1508-1515, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32948331

RESUMO

OBJECTIVES: A competing risk (CR) model distinguishing adhesive, cohesive and mixed failures as competing events was used for the analysis of micro-tensile bond strength (µTBS) data and compared with a conventional failure mode non-distinguishing survival model. METHODS: Fifty human molars were bonded using five universal adhesives (n = 10) and subdivided according to aging conditions (24-h water storage, thermocycling). After µTBS to dentin was tested, a fractographic analysis was performed using scanning electron microscopy. Survival analyses of the µTBS data were performed using both a failure mode distinguishing Weibull CR model, and a conventional failure mode non-distinguishing Weibull model. Weibull shape (m) and scale (σθ) parameters were calculated for both models using the maximum likelihood estimation method, and strength at 10 % probability of failure, σ0.10, was estimated. Groups were compared using 95 % confidence intervals. RESULTS: CR-model estimates of σθ and σ0.10 for adhesive failures were higher than those of the conventional model, more markedly in groups with lower percentages of adhesive failures. CR-model strength estimates for cohesive failures were similar in all groups regardless of their bond strengths and failure mode distributions. SIGNIFICANCE: Merging all bond-strength data into one dataset irrespective of the failure mode may result in a severe underestimation of bond strength, especially in groups with low incidence of adhesive failures. Bond-strength data analysis using a CR model could provide more accurate estimates of bond strength, and strength estimates for cohesive failures which were apparently independent of bond strength could serve as an internal validity indicator of the CR model.


Assuntos
Colagem Dentária , Adesivos Dentinários , Resinas Compostas , Análise de Dados , Cimentos Dentários , Dentina , Humanos , Teste de Materiais , Cimentos de Resina , Resistência à Tração
4.
J Adhes Dent ; 22(2): 183-193, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32322839

RESUMO

PURPOSE: To determine the effect of Weibull analysis with censoring of cohesive failures on the evaluation of the effect of surface treatment and adhesive on the microtensile composite-composite bond strength. MATERIALS AND METHODS: Surfaces of Filtek Z250 (3M Oral Care) specimens aged in distilled water for five months at 37°C were ground with SiC paper P320 or air abraded with Al2O3 and built up with the same composite using Optibond FL (OPF, Kerr), Clearfil SE Bond (CSE, Kuraray Noritake) and Gluma Comfort Bond (GLU, Kulzer) adhesives. After sectioning and trimming, the specimens were stored at 37°C in distilled water for 24 h and then tested in a microtensile bond strength setup. Complete datasets of all strength data and adhesive datasets containing adhesively failed specimens were analyzed with a one-way Welch ANOVA at α = 0.05 and compared with the results of Weibull analysis applied on complete and adhesive datasets as well as complete datasets right censored for cohesive failures. Weibull shape (m) and scale (σo) parameters were estimated using the maximum likelihood method and used to calculate bond strength (σ0.10) at 10% probability of failure as a measure of system performance. The surface morphology was studied using light and scanning electron microscopy. RESULTS: While ANOVA indicated a significant effect of surface treatment and non-significant effect of the adhesive, the Weibull analysis results depended on bond strength characteristics and censoring. The scale parameter of the complete dataset indicating a significant effect of surface treatment for all adhesives became statistically non-significant for CSE after censoring. When this effect was evaluated by σ0.10, the non-significant effect of surface treatment for OPF and GLU became statistically significant due to censoring. The effect of the adhesive evaluated by the scale parameter was non-significant both for surfaces as well as complete and censored datasets. On the other hand, s0.10 suggested significant differences between adhesives on the ground surface for complete datasets which became statistically non-significant for the censored datasets. CONCLUSION: This study indicates that the results of statistical evaluation of bond strength can be affected not only by the experimental set-up and statistical model but also the bond strength characteristics and the manner in which the strengths of cohesively failed specimens are included in calculations.


Assuntos
Colagem Dentária , Condicionamento Ácido do Dente , Cimentos Dentários , Teste de Materiais
5.
Dent Mater J ; 39(3): 500-508, 2020 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31827058

RESUMO

The aim of this study was to compare the effect of several commercially available disinfectants on the accuracy of various types of impression materials and their compatibility with gypsum including surface quality and structure evaluation. Four alginate and three elastomeric impression materials in combination with disinfectants Aseptoprint Liquid, Zeta 7 solution, Silosept and Dentaclean Form were tested. The dimensional changes, detail reproduction, the compatibility with gypsum and surface/subsurface morphology were evaluated using light microscopy, scanning electron microscopy and micro computed tomography. Two alginate materials disinfected in Dentaclean Form exhibited the most significant differences (p<0.0001). The loss of detail on some alginate impressions in combination with this disinfectant including deterioration and change of morphology of gypsum surfaces was observed. Porosity in subsurface area and exposed large particles were detected. It was confirmed that the desired properties of impressions may be negatively affected in combination with some disinfectants.


Assuntos
Sulfato de Cálcio , Desinfetantes , Desinfetantes de Equipamento Odontológico , Materiais para Moldagem Odontológica , Modelos Dentários , Teste de Materiais , Microscopia Eletrônica de Varredura , Propriedades de Superfície , Microtomografia por Raio-X
6.
Dent Mater ; 35(12): e299-e309, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31542248

RESUMO

OBJECTIVE: The influence of light-curing of a one-step self-etch adhesive (1-SEA) prior to the application of different bonding agents (BA) on the micro-tensile bond strength (µTBS) to dentin after 24h and thermal cycling was investigated. Additionally, the degree of conversion was evaluated using Fourier-transform infrared spectroscopy. METHODS: Three ion-releasing BAs, BZF-21 (experimental BA), Clearfil SE Protect (CSP), and FL-Bond II (FL-II), were applied subsequently to G-Premio Bond (1-SEA, GPB). Prior to their application, GPB was either light-cured (10s, 1000mW/cm2) or remained uncured. GPB was used as a control and Clearfil SE Bond 2 (CSE2) as a gold-standard 2-step reference. After resin-composite build-up and 24-h water storage (24h), half of the specimens were subjected to 15,000 thermal cycles (TC). Then, the specimens were sectioned into beams and tested under tensile load (1mm/min). The acquired data were analyzed using a 2-way ANOVA and Student's t-test with Bonferroni correction, and a two-parameter Weibull analysis, α=0.05. RESULTS: The µTBS of GPB increased significantly in the uncured groups with BZF-21 (24h: p<0.001, TC: p<0.001) and CSP (24h: p=0.039, TC: p<0.001), and in the light-cured group with CSP after TC (p=0.044). The groups with FL-II were not significantly different from GPB (p=1). No significant difference was found between CSE2 and the uncured groups GPB+BZF-21 (24h: p=1, TC: p=0.452) and GPB+CSP (24h: p=0.671, TC: p=0.566). SIGNIFICANCE: BZF-21 and CSP improved the µTBS of GPB to dentin both immediately and after TC. Higher µTBSs were obtained when GPB remained uncured prior to BA application.


Assuntos
Luzes de Cura Dentária , Colagem Dentária , Resinas Compostas , Cimentos Dentários , Dentina , Adesivos Dentinários , Humanos , Teste de Materiais , Cimentos de Resina , Resistência à Tração
7.
Scanning ; 38(5): 380-388, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26492940

RESUMO

This study investigated formation of protective deposits on the enamel surface after application of several anti-erosive toothpastes with different active ingredients. NaF-containing Sensodyne Pronamel, SnCl2 /F-based Elmex Erosion Protection and calcium phosphate-based BioRepair Plus Sensitivity Control, SensiShield and Enamel Care toothpastes with claimed anti-erosive properties were tested. Artificial saliva and Elmex Erosion Protection mouth rinse served as control groups. The toothpastes were applied 30 times by a toothbrush for 2 min per day, mouth rinse for 30 s on polished enamel of thirty five human molars (n = 5) with series of five rhomboid-shaped indents of various length prepared by a Knoop indentor. After 15 and 30 applications, the shape of the indents and surface morphology was characterised using light and scanning electron microscopy. At the end of treatment, the samples were exposed to 0.2 wt. % citric acid (pH 3.30) to test resistance of the treated enamel to erosion. Pronounced differences were observed between protective properties of the toothpastes. While Sensodyne Pronamel and BioRepair Plus Sensitivity Control did not produce any protective deposits, Enamel Care formed a compact layer of deposits which protected the enamel surface against erosion. With Elmex Erosion Protection and SensiShield fractured indent edges and scratches on the treated enamel suggested that their abrasive properties prevailed over ability of active ingredients to form deposits. These results revealed that toothpastes with strong potential to form acid-resistant deposits on the enamel surface and of low abrasivity should be used for effective prevention of enamel erosion. SCANNING 38:380-388, 2016. © 2015 Wiley Periodicals, Inc.


Assuntos
Esmalte Dentário/ultraestrutura , Erosão Dentária/prevenção & controle , Cremes Dentais/farmacologia , Humanos
8.
J Adhes Dent ; 10(6): 423-9, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19189672

RESUMO

PURPOSE: To estimate the in vitro reliability of typical self-etching and etch-and-rinse adhesives of various application protocols. MATERIALS AND METHODS: The following adhesives were applied on flat dentin surfaces of extracted human teeth (n = 223): self-etching two-step adhesives: AdheSE (AH), Clearfil SE Bond (CL), OptiBond SE (OS); one-step adhesives: Adper Prompt L-Pop (ADP), Adper Prompt (AD), and Xeno III (XE); all-in-one adhesive: iBond (IB); etch-and-rinse three-step adhesives: OptiBond FL (OF), two-step Gluma Comfort Bond (G), Excite (E) and Prime & Bond NT (PB). Composite buildups were prepared using a microhybrid composite, Opticor New. Shear bond strength was determined after 24 h of storage at 37 degrees C in distilled water. The results were analyzed with a nested ANOVA (adhesive, type of adhesive) followed by the Fisher post-hoc tests of group homogeneity at alpha = 0.05. A two-parameter Weibull distribution was used to calculate the critical shear bond strength corresponding to 5% probability of failure as a measure of system reliability. RESULTS: ANOVA revealed a significant decrease (p < 0.001) in the mean shear bond strength as follows: AH=CL=OS=G=E=OF>AD=IB=XE>PB=ADP, but no significant difference (p > 0.48) between the etch-and-rinse and self-etching adhesives. The corresponding characteristic bond strength of Weibull distribution ranged between 24.1 and 12.1 MPa, Weibull modulus between 8.3 and 2.1, and the critical shear bond strength varied from 16.0 to 3.0 MPa. CONCLUSION: Pronounced differences in the critical shear bond strength suggest reliability variations in the adhesive systems tested, which originate from chemical composition rather than type of adhesive.


Assuntos
Condicionamento Ácido do Dente/métodos , Colagem Dentária , Adesivos Dentinários/química , Dentina/ultraestrutura , Resinas Acrílicas/química , Bis-Fenol A-Glicidil Metacrilato/química , Resinas Compostas/química , Humanos , Teste de Materiais , Metacrilatos/química , Organofosfatos/química , Ácidos Polimetacrílicos/química , Probabilidade , Cimentos de Resina/química , Resistência ao Cisalhamento , Estresse Mecânico , Temperatura , Fatores de Tempo , Água/química
9.
J Prosthet Dent ; 96(6): 443-8, 2006 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17174662

RESUMO

STATEMENT OF PROBLEM: Setting of irreversible hydrocolloid impression materials is based on the ionic reaction between carboxylic groups and calcium ions and may, therefore, be affected by ionic species present in the mixing water. The impact of this phenomenon on the clinical performance of these materials has not been well documented. PURPOSE: The purpose of this study was to compare the setting behavior of irreversible hydrocolloid impression materials when mixed with tap and distilled water, and to determine the impact of typical cations present in tap water and their concentrations on the setting process. MATERIAL AND METHODS: Six brands of irreversible hydrocolloid impression materials (Kromopan 100, Xantalgin Select FS, Alginoplast, Elastic Plus, Ypeen, and Ypeen Premium) were mixed with tap and distilled water (control) according to manufacturers' recommendations. Elastic Plus was also mixed with aqueous solutions containing various concentrations of NaCl, CaCl(2), and AlCl(3) to determine the role of typical cations on setting. Using a controlled shear stress oscillatory rheometer, time changes of storage (G') and loss (G'') moduli during setting were measured at 23 degrees C and used to determine the working and setting times and rigidity of set impression materials. The sample size (n=3) for each material/mixing system was increased to 8 to increase reliability of measurements in systems where the effect of mixing water was low or variance of results was high. The data were analyzed (alpha=.05) using a t test (tap water), a 1-way ANOVA, a Tukey post hoc test (shear stress), and a nested ANOVA and Fisher Least Significant Difference post hoc analysis (cation and cation concentration). RESULTS: Statistical analysis showed significant (P<.001) acceleration in the setting rate for Kromopan 100, the working time of which was shorter with tap water by 23.4 seconds and the setting time, by 32.8 seconds. Similar significant reductions (in seconds) in both working and setting times, respectively, were found with Xantalgin Select FS (12.0, P<.001 and 23.6, P<.002), Alginoplast (24.3, P<.001 and 44.7, P<.005), and Elastic Plus (23.0, P<.001 and 22.0, P<.002), when compared with the same materials mixed with distilled water. At the same time, the rigidity of the set impression materials mixed with tap water increased by approximately 10%. With Ypeen Premium, the setting time decreased significantly by 20.0 seconds (P<.001) with tap water, while the working time and rigidity did not change. The setting behavior of Ypeen was not significantly affected by water quality. Acceleration of the setting reactions and increase in impression rigidity depended (P<.001) primarily on concentration and valency of cations present in mixing water. CONCLUSION: Setting of irreversible hydrocolloid impression materials can be significantly accelerated when tap water with high water hardness is used for mixing or when the mixing water contains higher concentrations of cations such as Na(+), Ca(2+), and Al(3+).


Assuntos
Coloides/química , Materiais para Moldagem Odontológica/química , Soluções/química , Água/química , Alumínio/efeitos adversos , Cálcio/efeitos adversos , Resistência ao Cisalhamento , Sódio/efeitos adversos
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