Resin-dentin bond stability of etch-and-rinse adhesive systems with different concentrations of MMP inhibitor GM1489

Abstract Enzymatic degradation of the hybrid layer can be accelerated by the activation of dentin metalloproteinases (MMP) during the bonding procedure. MMP inhibitors may be used to contain this process. Objective To evaluate the degree of conversion (DC%), dentin bond strength (µTBS) (immediate and after 1 year of storage in water), and nanoleakage of an experimental (EXP) and a commercial (SB) adhesive system, containing different concentrations of the MMP inhibitor GM1489: 0, 1 µM, 5 µM and 10 µM. Methodology DC% was evaluated by FT-IR spectroscopy. Dentin bond strength was evaluated by µTBS test. Half of beams were submitted to the µTBS test after 24 h and the other half, after storage for 1 year. From each tooth and storage time, 2 beams were reserved for nanoleakage testing. Data were analyzed using ANOVA and Tukey's test to compare means (α=0.05). Results All adhesive systems maintained the µTBS after 1 year of storage. Groups with higher concentrations of inhibitor (5 µM and 10 µM) showed higher µTBS values than groups without inhibitor or with 1 µM. The nanoleakage values of all groups showed no increase after 1 year of storage and values were similar for SB and EXP groups, in both storage periods. The inhibitor did not affect the DC% of the EXP groups, but the SB5 and SB10 groups showed higher DC% values than those of SB0 and SB1. Conclusions The incorporation of GM1489 in the adhesive systems had no detrimental effect on DC%. The concentrations of 5 µM GM1489 for SB and 5 µM or 10 µM for EXP provided higher μTBS than groups without GM1489, in the evaluation after 1 year of storage; whereas the concentration of inhibitor did not affect adhesive systems nanoleakage.

Effect of iodonium salt and chitosan on the physical and antibacterial properties of experimental infiltrants

Abstract Resinous infiltrants are indicated in the treatment of incipient carious lesions, and further development of these materials may contribute to greater control of these lesions. The aim of this study was to analyze the physical and antibacterial properties of experimental infiltrants containing iodonium salt and chitosan. Nine experimental infiltrants were formulated by varying the concentration of the diphenyliodonium salt (DPI) at 0, 0.5 and 1 mol%; and chitosan at 0, 0.12 and 0.25 g%. The infiltrants contained the monomeric base of triethylene glycol dimethacrylate and bisphenol-A dimethacrylate ethoxylate in a 75 and 25% proportion by weight, respectively; 0.5 mol% camphorquinone and 1 mol% ethyl 4-dimethylaminobenzoate. The degree of conversion was evaluated using Fourier transformer infrared spectroscopy, and the flexural strength and elastic modulus using the three-point bending test. Sorption and solubility in water, and antibacterial analysis (minimum inhibitory concentration and minimum bactericidal concentration) were also analyzed. Data was analyzed statistically by two-way ANOVA and Tukey's test (p<0.05), with the exception of the antibacterial test, which was evaluated by visual inspection. In general, the infiltrant group containing 0.5% DPI and 0.12% chitosan showed high values of degree of conversion, higher values of elastic modulus and flexural strength, and lower sorption values in relation to the other groups. Antibacterial activity was observed in all the groups with DPI, regardless of the concentration of chitosan. The addition of DPI and chitosan to experimental infiltrants represents a valid option for producing infiltrants with desirable physical and antibacterial characteristics.

Influence of activation mode, fatigue, and ceramic interposition on resin cements' diametral tensile strength

Abstract This study evaluated the influence of activation modes, on Diametral Tensile Strength (DTS) of dual cured resin cements subjected to a Mechanical Fatigue test (MF). Four dual-cured resin cements (RelyX UNICEM [U], RelyX ARC [A], ENFORCE [E] and Nexus 2 [N]) were activated by three different curing modes as follows: Self-Curing (SC), Dual Cure activation with photoactivation executed directly (DC) and Dual Cure activation with Photoactivation Through Porcelain (DCTP). After 24 hours, half of the sample was subjected to 30.000 fatigue cycles at 1 Hz frequency and 12 N load. Then, all specimens were subjected to DTS test in Instron Universal Testing Machine and data were analyzed by three-way ANOVA and Tukey's Test (5%). The results of DTS test means (MPa) and standard deviation, for each cement factor activated by SC, DC and DCTP was respectively: U (28.12 ± 5.29; 37.44 ± 6.49 and 40.10 ± 4.39), A (49.68 ± 8.42; 55.12 ± 5.16 and 63.43 ± 6.92), E (49.12 ± 3.89; 56.42 ± 8.88 and 56.96 ± 6.45) and N (61.89 ± 11.21; 59.26 ± 9.47 and 62.56 ± 10.93). Turkey's test indicated that DC is related to the highest DTS values; Nexus 2 DTS remained the same independently of activation mode and that the Porcelain disk interposition enhanced DTS only for RelyX ARC the ANOVA statistical test indicated that MF didn't alter the DTS values for all experimental groups. MF results clinical implication is that all cements tested exhibited, in an immediate loading, good cross linked bonds quality.

Long-term bonding efficacy of adhesives containing benzodioxioles as alternative co-initiators

Abstract This study evaluated the three-year lifespan of the bond to dentin of experimental self-etch adhesives containing benzodioxole derivatives - 1,3-benzodioxole (BDO) and piperonyl alcohol (PA) - as co-initiator alternative to amines. Adhesive resins were formulated using Bis-GMA, TEGDMA, HEMA, camphorquinone and different co-initiators: BDO, PA or ethyl 4-dimethylamino benzoate (EDAB - amine). An experimental self-etch primer was used to complete the two-step, self-etch adhesive system. Clearfil SE Bond (CSE) was used as commercial reference. Bond strength to human dentin was assessed by microtensile bond strength (µTBS) test, and failure mode was classified. Morphology of the dentin bonding interface was assessed via scanning electron microscopy (SEM). Irrespective of the dental adhesives evaluated, µTBS was higher after 24 hours compared with that after 1.5 and 3 years (p ≤ 0.001). However, adhesives with BDO and PA as co-initiators showed significantly higher bond strength than the bonding resin with EDAB (p ≤ 0.002), independent of the time evaluated. The commercial adhesive CSE showed similar bond strength compared with the other groups (p ≥ 0.05). Mixed failures were mainly observed after 24 hours, while adhesive failures were more frequently observed after 1.5 and 3 years. No notable differences in homogeneity and continuity along the bonded interfaces were detected among the materials in the SEM analysis. In conclusion, benzodioxole derivatives are feasible alternative co-initiators to tertiary amine in camphorquinone-based self-etching dental adhesive formulations.

Influence of a hydrophobic monomer on the physical and mechanical properties of experimental surface sealants

Abstract This study evaluated the effect of adding the hydrophobic monomer 1,12 dodecanediol dimethacrylate (DDDMA) to experimental sealants with and without thermocycling on degree of conversion (DC), water sorption (WS), water solubility (WSB), color stability (ΔE), and micro-shear bond strength (μSBS). Five experimental and one commercially available sealant (Bisco - BIS) were tested. The experimental sealants were formulated by mixing different percentages of DDDMA monomers and urethane dimethacrylate (UDMA). The photoinitiator system was composed by camphorquinone (CQ) and tertiary amine 4-ethyl benzoate dimetilamiono (EDBA). Ethanol was used as a solvent. The experimental groups were named sequentially according to the monomeric content (DDDMA/UDMA): S40/40 (40/40), S50/30 (50/30), S60/20 (60/20), S70/10 (70/10) and S80/0 (80/0). Data were analyzed separately by one-way ANOVA, followed by Tukey's test (p<0.05). The values of DC ranged from 94.59% (S40/40) to 54.02% (S80/10). BIS showed the highest WS value (p<0.05) and S40/40, S50/30, S60/20 and S80/0 showed the lowest WS values of all tested sealants. WSB values ranged from 7.88 µg/mm3 (BIS) to 13.27 µg/mm3 (S70/10). The highest ΔE value was 11.05±2.88 for BIS and the highest μSBS value was found for S60/20. No significant difference was observed in bond strength between sealants and bovine enamel after thermocycling. Adding DDDMA to the composition of surface sealants can improve its performance, once the monomer increased the degree of conversion and the color stability.

Evaluation of physical-mechanical properties, antibacterial effect, and cytotoxicity of temporary restorative materials

Abstract The objective of this study was to compare selective physical-mechanical properties, antibacterial effects and cytotoxicity of seven temporary restorative materials (TRM): five resin-based materials [Bioplic (B), Fill Magic Tempo (FM), Fermit inlay (F), Luxatemp LC (L) and Revotek LC (R)], and zinc oxide-eugenol cement (IRM) and glass ionomer cement (GIC) as the controls. Material and methods The physical-mechanical properties were evaluated by determining microleakage (ML), ultimate tensile strength (UTS) and Shore D hardness (SDH). In addition, the polymerization rate (Pr-1), depth of cure (DC), water sorption and solubility (WS/SL) were evaluated. The antimicrobial effects of the materials were assessed by biofilm accumulation of Streptococcus mutans (BT) and the direct contact test (DCT) by exposure to Enterococcus faecalis for 1 and 24 h, and cytotoxicity by MTT assay. The data were analyzed by ANOVA or Kruskall-Wallis tests, and a complementary post-hoc method (p<0.05). Results Group B, followed by FM and GIC had significantly lower percentages of microleakage in comparison with the other groups; Groups FM and L showed the highest WS, while Groups R and FM showed the significantly lowest SL values (p<0.05). Group R showed the statistically highest UTS mean and the lowest DC mean among all groups. Group F showed the lowest S. mutans biofilm accumulation (p=0.023). Only the Group L showed continued effect against E. faecalis after 1 h and 24 h in DCT. The L showed statistically lower viability cell when compared to the other groups. Conclusions These findings suggest the antibacterial effect of the temporary materials Fill Magic and Bioplic against S. mutans, while Luxatemp showed in vitro inhibition of S. mutans biofilm accumulation and E. faecalis growth. Regarding the cell viability test, Luxatemp was the most cytotoxic and Fill Magic was shown to be the least cytotoxic.

Model resin composites incorporating ZnO-NP: activity against S. mutans and physicochemical properties characterization

Abstract Although resin composites are widely used in the clinical practice, the development of recurrent caries at composite-tooth interface still remains as one of the principal shortcomings to be overcome in this field. Objectives To evaluate the activity against S. mutans biofilm of model resin composites incorporating different concentrations of ZnO-nanoparticles (ZnO-NP) and characterize their physicochemical properties. Materials and Methods Different concentrations of ZnO-NP (wt.%): E1=0, E2=0.5, E3=1, E4=2, E5=5 and E6=10 were incorporated into a model resin composite consisting of Bis-GMA-TEGDMA and barium borosilicate particles. The activity against S. mutans biofilm was evaluated by metabolic activity and lactic acid production. The following physicochemical properties were characterized: degree of conversion (DC%), flexural strength (FS), elastic modulus (EM), hardness (KHN), water sorption (Wsp), water solubility (Wsl) and translucency (TP). Results E3, E4, E5 and E6 decreased the biofilm metabolic activity and E5 and E6 decreased the lactic acid production (p<0.05). E6 presented the lowest DC% (p<0.05). No significant difference in FS and EM was found for all resin composites (p>0.05). E5 and E6 presented the lowest values of KHN (p<0.05). E6 presented a higher Wsp than E1 (p<0.05) and the highest Wsl (p<0.05). The translucency significantly decreased as the ZnO- NP concentration increased (p<0.05). Conclusions The incorporation of 2 - 5 wt.% of ZnO-NP could endow antibacterial activity to resin composites, without jeopardizing their physicochemical properties.

Degree of conversion and bond strength of resin-cements to feldspathic ceramic using different curing modes

Abstract Resin cements have led to great advances in dental ceramic restoration techniques because of their ability to bond to both dental structures and restorative materials. Objective The aim of this study was to assess the performance of resin cements when different curing modes are used, by evaluating the degree of conversion and bond strength to a ceramic substrate. Material and Methods Three resin cements were evaluated, two dual-cured (Variolink II and RelyX ARC) and one light-cured (Variolink Veneer). The dual-cured resin cements were tested by using the dual activation mode (base and catalyst) and light-activation mode (base paste only). For degree of conversion (DC) (n=5), a 1.0 mm thick feldspathic ceramic disc was placed over the resin cement specimens and the set was light activated with a QTH unit. After 24 h storage, the DC was measured with Fourier transform infrared spectroscopy (FTIR). For microshear bond strength testing, five feldspathic ceramic discs were submitted to surface treatment, and three cylindrical resin cement specimens were bonded to each ceramic surface according to the experimental groups. After 24 h, microshear bond testing was performed at 0.5 mm/min crosshead speed until the failure. Data were submitted to one-way ANOVA followed by Tukey test (p<0.05). Scanning electron microscopy (SEM) was used for classifying the failure modes. Results Higher DC and bond strength values were shown by the resin cements cured by using the dual activation mode. The Variolink II group presented higher DC and bond strength values when using light-activation only when compared with the Variolink Veneer group. Conclusion The base paste of dual-cured resin cements in light-activation mode can be used for bonding translucent ceramic restorations of up to or less than 1.0 mm thick.

Influence of addition of [2-(methacryloyloxy)ethyl]trimethylammonium chloride to an experimental adhesive

Abstract The aim of this study was to develop an experimental adhesive with addition of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) and to evaluate its mechanical and biological properties and its in vitro antibacterial activity. An experimental adhesive resin was formulated with Bis-GMA, TEGDMA, and HEMA. The antibacterial monomer was added at concentrations of 1%, 2.5%, and 5% (METAC groups). A group without METAC addition was used as control. The experimental adhesives were evaluated as to their antibacterial potential against Streptococcus mutans, degree of conversion, and softening in ethanol for 2 hours. The data were analyzed by one-way ANOVA, Tukey’s post-hoc test, and the paired Student’s t-test (significance level of 0.05). METAC showed antibacterial activity against S. mutans at all concentrations (p < 0.05). There was no statistical difference across METAC groups (p > 0.05). The 1%, 2.5%, and 5% groups yielded the highest mean values for degree of conversion (p < 0.05). The 1% group did not differ from the control group (p > 0.05). There was no statistical difference in baseline microhardness values (p > 0.05) and microhardness values after immersion in ethanol were lower than at baseline for all groups (p < 0.05). There was no statistical difference in the reduction of Knoop hardness number (KHN) after immersion in ethanol for any of the groups (p > 0.05). The results of the present study indicate that METAC is a promising antibacterial agent when added to an adhesive system.

Longevity of metal-ceramic crowns cemented with self-adhesive resin cement: a prospective clinical study

Abstract Resin cements are often used for single crown cementation due to their physical properties. Self-adhesive resin cements gained widespread due to their simplified technique compared to regular resin cement. However, there is lacking clinical evidence about the long-term behavior of this material. The aim of this prospective clinical trial was to assess the survival rates of metal-ceramic crowns cemented with self-adhesive resin cement up to six years. One hundred and twenty-nine subjects received 152 metal-ceramic crowns. The cementation procedures were standardized and performed by previously trained operators. The crowns were assessed as to primary outcome (debonding) and FDI criteria. Statistical analysis was performed using Kaplan-Meier statistics and descriptive analysis. Three failures occurred (debonding), resulting in a 97.6% survival rate. FDI criteria assessment resulted in scores 1 and 2 (acceptable clinical evaluation) for all surviving crowns. The use of self-adhesive resin cement is a feasible alternative for metal-ceramic crowns cementation, achieving high and adequate survival rates.

Evaluation of phenyl-propanedione on yellowing and chemical-mechanical properties of experimental dental resin-based materials

ABSTRACT Objective To evaluate the influence of phenyl-propanedione on yellowing and chemical-mechanical properties of experimental resin-based materials photoactivated using different light curing units (LCUs). Material and Methods Experimental resin-based materials with the same organic matrix (60:40 wt% BisGMA:TEGDMA) were mechanically blended using a centrifugal mixing device. To this blend, different photoinitiator systems were added in equimolar concentrations with aliphatic amine doubled by wt%: 0.4 wt% CQ; 0.38 wt% PPD; or 0.2 wt% CQ and 0.19 wt% PPD. The degree of conversion (DC), flexural strength (FS), Young’s modulus (YM), Knoop hardness (KNH), crosslinking density (CLD), and yellowing (Y) were evaluated (n=10). All samples were light cured with the following LCUs: a halogen lamp (XL 2500), a monowave LED (Radii), or a polywave LED (Valo) with 16 J/cm2. The results were analysed by two-way ANOVA and Tukey’s test (α=0.05). Results No statistical differences were found between the different photoinitiator systems to KNH, CLS, FS, and YM properties (p≥0.05). PPD/CQ association showed the higher DC values compared with CQ and PPD isolated systems when photoactivated by a polywave LED (p≤0.05). Y values were highest for the CQ compared with the PPD systems (p≤0.05). Conclusion PPD isolated system promoted similar chemical and mechanical properties and less yellowing compared with the CQ isolated system, regardless of the LCU used.

Effects of the application techniques of self-adhesive resin cements on the interfacial integrity and bond strength of fiber posts to dentin

ABSTRACT Objective: To evaluate the influence of an application technique of a glass-fiber post using self-adhesive resin cements on the push-out bond strength and the presence of bubbles in the root thirds. The cements were either applied according to the manufacturer's instruction or using a commercial delivering system (Centrix), at which the cement pastes were collected and applied after manipulation. Material and Methods: Self-adhesive resin cements (RelyX U200/3M ESPE-U200; Maxcem Elite/Kerr-MAX; Clearfil SA Cement/Kuraray-CSA) and a conventional cement (RelyX ARC/3M ESPE-ARC) were used to cement a post and applied either based on the manufacturer's instructions or using a Centrix syringe to deliver the cements directly onto the post of choice, or directly into canal. The roots were scanned with a micro-computed tomography (μCT) and then sectioned into nine 1-mm thick slices for a push-out bond strength test. The μCT images showed the percentage of bubbles in the root thirds (cervical, medium, and apical). Data were analyzed with three-way ANOVA/Tukey (α=0.05). Results: Triple interaction was not significant (p>0.05). The interaction “material” vs “root third” was not significant. A significant interaction was observed between “material” vs “application technique” (p<0.05). For ARC, U200, and MAX, significantly lower percentages of bubbles were observed when the Centrix syringe delivered the cements. Equivalent percentages of voids were observed for CSA, irrespective of the application technique (p>0.05). Significantly higher bond strength was observed when the self-adhesive resin cements were applied using the Centrix delivery system, in comparison with the manufacturer's instructions (p<0.05). Bond strength varied with the root third: cervical>medium>apical (p<0.05). No correlations were found between the bond strength and voids. Conclusions: Bond strength and voids are negatively influenced by the conventional application technique for luting fiber posts. The delivery system (Centrix) seems to produce better results when cementing fiber posts.

Porosity of temporary denture soft liners containing antifungal agents

ABSTRACT Incorporation of antifungals in temporary denture soft liners has been recommended for denture stomatitis treatment; however, it may affect their properties. Objective: To evaluate the porosity of a tissue conditioner (Softone) and a temporary resilient liner (Trusoft) modified by minimum inhibitory concentrations (MICs) of antifungal agents for Candida albicans biofilm. Material and Methods: The porosity was measured by water absorption, based on exclusion of the plasticizer effect. Initially, it was determined by sorption isotherms that the adequate storage solution for specimens (65×10×3.3 mm) of both materials was 50% anhydrous calcium chloride (S50). Then, the porosity factor (PF) was calculated for the study groups (n=10) formed by specimens without (control) or with drug incorporation at MICs (nystatin: Ny-0.032 g, chlorhexidine diacetate: Chx-0.064 g, or ketoconazole: Ke-0.128 g each per gram of soft liner powder) after storage in distilled water or S50 for 24 h, seven and 14 d. Data were statistically analyzed by 4-way repeated measures ANOVA and Tukey's test (α=.05). Results: Ke resulted in no significant changes in PF for both liners in water over 14 days (p>0.05). Compared with the controls, Softone and Trusoft PFs were increased at 14-day water immersion only after addition of Ny and Chx, and Chx, respectively (p<0.05). Both materials showed no significant changes in PF in up to 14 days of S50 immersion, compared with the controls (p>0.05). In all experimental conditions, Softone and Trusoft PFs were significantly lower when immersed in S50 compared with distilled water (p<0.05). Conclusions: The addition of antifungals at MICs resulted in no harmful effects for the porosity of both temporary soft liners in different periods of water immersion, except for Chx and Ny in Softone and Chx in Trusoft at 14 days. No deleterious effect was observed for the porosity of both soft liners modified by the drugs at MICs over 14 days of S50 immersion.

Influência na resistência de união de pinos de fibra de vidro com e sem retenções mecânicas em função dos materiais utilizados para cimentação: teste de 'push-out' / Influence on the bond strength of glass fiber posts with and without mechanical retentions depending of materials used for cementing: push-out test

Este estudo teve como objetivo avaliar a influência na resistência de união de pinos de fibra de vidro (PFV) com retenções mecânicas (CRM) e sem retenções (SR), associados a três materiais: RelyX ARC cimento resinoso convencional dual com sistema adesivo Adper Single Bond (ASB), convencional de 2 passos; RelyX U200 cimento resinoso auto condicionante dual e resina flow SDR foto ativada, com sistema adesivo Prime & Bond 2.1 (PB), convencional de 2 passos; nos terços cervical (C), médio (M) e apical (A), por meio do teste de push-out. Sessenta incisivos bovinos foram selecionados, tiveram as coroas seccionadas para padronizar 17mm de raiz e foram submetidas ao tratamento endodôntico, para posterior cimentação do PFV. Foram divididas aleatoriamente em 2 grupos (N=30), quanto ao tipo de PFV: CRM - com retenções mecânicas (Glassix+plus no2) e SR - sem retenções (Exacto no2). Todos os PFV apresentavam formato cônico. Cada grupo foi subdividido em 3 (N=10), quanto ao tipo de material: cimento RelyX ARC+ASB; cimento RelyX U200 (auto condicionante) e resina SDR+PB. Todas as orientações dos fabricantes para tempo de manipulação e foto ativação do material foram rigorosamente respeitadas. As raízes foram mantidas em saliva artificial e decorridas 24h da cimentação dos PFV, foram seccionadas perpendicularmente ao longo eixo, obtendo 9 fatias de aproximadamente 1mm, cuja identificação foi feita de acordo com o terço correspondente. O teste de push-out foi realizado em máquina de ensaio universal com célula de carga de 50N; velocidade de 0,5mm/min, da direção apical para a cervical da fatia até que o pino fosse deslocado, respeitando o formato cônico do canal radicular. Todos os espécimes foram analisados em microscopia óptica, aumento de 200 vezes, quanto aos tipos de falha ocorrido. Os dados foram tabulados considerando as variáveis dos diferentes materiais utilizados para a cimentação, presença ou não de retenções mecânicas nos PFV e terços radiculares. Os valores de resistência de união (Ru) obtidos foram submetidos ao teste de normalidade Kolmogorov- Smirnov, à análise de variância a três critérios (ANOVA) e ao teste LSD de Fisher (p<0,05). Os resultados mostraram diferença estatisticamente significante nos terços C, M e A, respectivamente para os cimentos ARC com pino Glassix+plus, média e desvio padrão (MPa) a seguir, 8,50 (4,76); 6,99 (3,55); 4,71 (2,13) e U200 com pino Exacto: 9,40 (4,93); 8,02 (4,67); 4,67 (1,86); a resina SDR não interagiu significativamente com os PFV CRM 6,78 (2,72); 5,97 (2,45); 2,67 (1,55) e SR 7,24 (3,55); 6,86 (2,84); 4,10 (1,90). A análise microscópica mostrou predominância de falhas adesivas entre cimento e dentina e mista para todos os grupos. O cimento U200 com pino Exacto apresentou o melhor desempenho, seguido do ARC com pino Glassix+plus. A resina SDR teve desempenho semelhante para ambos os PFV. Todos os grupos apresentaram valores de Ru maiores no terço cervical, intermediários no terço médio e menores no terço apical.(AU)

This study aimed to evaluate the influence on the bond strength of glass fiber posts (GFP) with mechanical retention (WMR) and without retentions (NR), associated with three materials: RelyX ARC total-etching resin cement dual cure with Adper Single Bond (ASB) adhesive system, conventional 2 steps; RelyX U200 self-etching resin cement dual cure, and flowable resin SDR, activated by light, with Prime & Bond 2.1 adhesive system conventional 2 steps in the cervical (C), medium (M) and apical (A) thirds by the "push-out" test. Were selected sixty bovine incisors, had the crowns sectioned to root was standardized 17mm, were submitted to endodontic treatment, for cementing the GFP later. Were randomly divided into 2 groups (N=30), according to the GFP: WMR - with mechanical retentions (Glassix+plus ≠2) and NR - without retentions (Exacto ≠2). All GFP had conic shape. Each group was divided into 3 (N=10), according to material: RelyX ARC+ASB, RelyX U200 (self-etching) and flowable resin SDR+PB. All guidelines of manufacturers to handling time and cure time of the material were strictly adhered. The roots were kept in artificial saliva and 24 hours after GFP cementing it were sectioned perpendicular to the long axis, obtaining nine slices of approximately 1mm, which identification was done according to the corresponding third. The "push-out" test was performed with a universal test machine, 50N load cell; crosshead speed of 0.5 mm/min, the load was applied in an apical to cervical direction until the post dislodged from the specimen, respecting the conical shape of the root canal. Subsequently, all specimens were analyzed with optical microscopy 200 times increase to evaluate failure modes. Data were tabulated considering the materials used for cementing, presence or absence of mechanical retentions in GFP and root thirds. The bond strength values (BS) were submitted to Kolmogorov-Smirnov normality test, three-way ANOVA and Fisher's LSD test (p<0.05). The values showed statistically significant differences in thirds C, M and A, respectively for the ARC with Glassix+plus, average and standard deviation (MPa): 8.50 (4.76); 6.99 (3.55); 4.71 (2.13) and U200 with Exact post: 9.40 (4.93); 8.02 (4.67); 4.67 (1.86). SDR resin does not significantly interacted with GFP WMR 6.78 (2.72); 5.97 (2.45); 2.67 (1.55) and NR 7.24 (3.55); 6.86 (2.84); 4.10 (1.90). The microscopic analysis showed predominance of failure between cement and dentine and mixed for all groups. U200 cement with Exacto post had the best performance, followed by ARC with Glassix+plus post, SDR resin has similar performance for both GFP. All groups showed BS values higher in the cervical third, intermediate in the middle third and smaller in the apical third.(AU)

Efeito de inibidores da atividade proteolítica na resistência de união de pino de fibra de vidro à dentina radicular após 12 meses / Effect of proteolytic activity inhibitors on bond strength of glass-fiber post to radicular dentin up to 12 months

O estabelecimento de uma camada híbrida adequada no canal radicular representa um dos principais desafios clínicos devido à dificuldade de acesso. Dessa forma, o uso de inibidores proteolíticos poderia tornar-se um recurso favorável. O objetivo deste estudo foi avaliar o efeito de inibidores proteolíticos na união de pino de fibra de vidro fixado com cimento adesivo, considerando os terços radiculares e tempos distintos, por meio da resistência de união (RU). Cento e quarenta e quatro raízes bovinas foram selecionadas e divididas em 6 grupos de tratamento, e redivididas em 3 subgrupos de acordo com os tempos de avaliação de 24 horas, 6 e 12 meses (n=8). Após o tratamento endodôntico e desobturação padronizados, as raízes foram cimentadas com pinos de fibra de vidro cônicos (Exacto/Angelus). As raízes foram tratadas com sistema adesivo convencional de três passos, Adper Scotchbond Multipurpose/ 3M ESPE (SBMP) e cimento dual RelyX ARC/ 3M ESPE. Após prévia divisão, foram alocadas em grupos CN (Controle Negativo- sem pré tratamento associado), CP (Controle Positivo- com agentes ativador e catalisador), EDTA (ácido etilenodiamino tetra-acético a 17%), CHX (digluconato de clorexidina a 2%), E-5 (E- 64 a 5 µM) e E-10 (E-64 a 10 µM). Após 24 horas, as raízes foram seccionadas perpendicularmente ao longo eixo e identificadas quanto à região, obtendo-se fatias de 1 mm de espessura (cervical, médio e apical), que foram armazenadas em saliva artificial para serem testadas. Todas as fatias foram submetidas ao teste de extrusão (push-out) na máquina de teste universal (Instron) com célula de carga de 50 N a 0,5 mm/min. Os dados foram analisados pelo teste de ANOVA a três critérios e comparações múltiplas com Tukey, ambos com p<0,05. Após 24 horas, não se observou diferenças entre os tratamentos. Após 6 meses, a CHX demonstrou melhor desempenho, cujo efeito não se prorrogou até os 12 meses. O uso de inibidores proteolíticos não foram capazes de preservar a resistência de união dos pinos intrarradiculares até o tempo de 12 meses.(AU)

The adequate establishment of hybrid layer in the root canal on bonding process is still a clinical challenge due to its hard access. Thus, the use of proteolytic inhibitors could become a favorable tool. The aim of this study was to evaluate the effect of proteolytic inhibitors in the bonding of a glass- fiber post fixed with a luting cement, regarding the root thirds and different times through the bond strength. One hundred and forty four bovine roots were selected and divided into 6 treatment groups, and subdivided according to the time of evaluation of 24 hours, 6 and 12 months (n=8). After endodontic treatment and standardized removal procedure, the roots were cemented with tapered glass fiber posts (Exacto/ Angelus). The roots were treated with three-step etch-and-rinse adhesive system Adper Scotchbond Multipurpose/ 3M ESPE (SBMP) and dual cement RelyX ARC/ 3M ESPE. After previous division, CN (negative- control without pre associated treatment), CP (Control positive- with activator and catalyst agents) EDTA (17% ethylenediaminetetraacetic acid) CHX (2% chlorhexidine digluconate) E-5 (5µM E-64) and E-10 (10µM E-64). After 24h, the roots were sectioned perpendicular to the long axis and identified according to third in 1mm thick slices (cervical, middle and apical), which were stored in artificial saliva to be tested. All slices were subjected to extrusion tests (push-out) in the universal test machine (Instron) at 50 N load cell at 0.5 mm/min. Data were analyzed with three-way ANOVA and multiple comparisons with Tukey test, both with p <0.05. After 24 hours, no differences were observed between treatments. After 6 months, CHX showed better performance, which did not last up 12 months. The proteolytic inhibitors performed differently in the bonding process over time; only CHX promoted inhibition at 6 months. The use of proteolytic inhibitors were not able to maintain the bond strength of intraradicular posts up time of 12 months.(AU)

Influência do tempo de condicionamento ácido na alteração superficial, resistência de união e compressão da cerâmica de dissilicato de lítio / Influence of etching time on the superficial alterations, bond strength and compression resistence of lithium disilicate ceramic

Este estudo in vitro propôs analisar os padrões de condicionamento da superfície da cerâmica a base de dissilicato de lítio após três tempos de condicionamento com ácido fluorídrico a 10%, a influência desses tempos na resistência ao cisalhamento de cilindros cerâmicos e à compressão de placas cerâmicas cimentadas em esmalte de dentes bovinos. Para análise de superfície foram utilizadas 36 placas de cerâmica (IPS e.max Press), sem tratamento e condicionadas por 10s, 20s e 60s (E0,E10,E20,E60; n=3), observadas em MEV, energia dispersiva espectroscópica (EDS) e perfilômetro. Para o teste de resistência de união, 180 cilindros cerâmicos (2mm diâmetro x 2mm comprimento; n=20) foram condicionados e cimentados (80 m de espessura) com RelyX ARC em esmalte variando os sistemas adesivos {Silano+Single Bond (S); RelyX Ceramic Primer Silano +Single Bond (R); Single Bond Universal (U)}, obtendo-se os grupos: E10S, E20S, E60S, E10R, E20R, E60R, E10U, E20U e E60U. Após 24h realizou-se o teste de cisalhamento (EMIC, 0,5mm/min, 50Kgf). O teste de compressão ao esmalte (Kratos, 0,5mm/min 50Kgf) foi realizado após 24h da cimentação de 60 placas cerâmicas quadradas (5x5mm com 1mm de espessura; n=10), condicionadas e cimentadas (RelyX ARC, 80m) variando os sistemas adesivos R e U (10R, 20R, 60R, 10U, 20U e 60U). Os resultados da análise em MEV mostraram que foi mantido o mesmo padrão de condicionamento, porém, mais evidenciado com o aumento do tempo de tratamento. A quantidade de sílicio observada em EDS foi: E0:24,73% < E10:61,10% < E20:67,50% = E60:67,54% e a rugosidade: E0: 6,25 m < E10: 10,6m < E20: 12,0m < E60: 18,0m. Para os resultados dos ensaios de cisalhamento foi usado um modelo linear generalizado, com distribuição normal para a variável resposta e função de ligação do tipo raiz quadrada. Para compressão, usamos um modelo linear normal. Em ambos os casos, a hipótese de normalidade dos desvios foi verificada a partir do Q-Q Plot e do Teste de Kolmogorov-Smirnov. Para os testes de cisalhamento (MPa), independente do tempo de condicionamento, o grupo S apresentou os menores valores, enquanto os grupos R e U apresentaram valores semelhantes (E10S:84,2±7,2A/a, E10R:124,4±7,9A/b, E10U:117,2±7,8A/b, E20S:102,3±7,6B/a, E20R:146,2±8,2B/b, E20U:138,4±7,9B/b, E60S:107,2±7,8B/a, E60R:152,1±8,1B/b, E60U:144,1±8,1B/b). Para o teste de compressão (N), os valores Médios foram: 10R:869,8±122a, 10U:879,3±159a, 20R:795,0±219ab, 20U:852,3±227ab, 60R:772,7±162b, 60U:704,0±235b. O aumento do tempo de condicionamento da superfície da cerâmica a base de dissilicato de lítio aumentou a rugosidade superficial, não demonstrou diferença significativa da resistência de união de 20s par 60s, e apresentou leve diminuição para resistência de compressão.(AU)

The present in vitro study aimed to analyze the etching patterns of lithium disilicate based ceramic after three etching times with 10% hydrofluoric acid, and the influence of these times on the shear bond strength of ceramic cylinders and compression resistance of ceramic plates cemented to bovine enamel teeth. For the surface analysis, 36 ceramic plates (IPS e.max Press) were used untreated and etched for 10s, 20s and 60s (E0, E10, E20, E60; n = 3), as observed in SEM, energy dispersive spectroscopy (EDS) and profilometry. For the bond strength test, 180 ceramic cylinders (2x2mm; n = 20) were etched and cemented with RelyX ARC (80 m thick) on the enamel varying adhesive systems {Silane + Single Bond (S); RelyX Ceramic Primer Silane + Single Bond (R); Single Bond Universal (U)}, yielding the groups: E10S, E20S, E60S, E10R, E20R, E60R, E10U, E20U and E60U. After 24h, the shear bond strength test was performed (EMIC, 0.5 mm/min, 50Kgf). The ceramic compression test (Kratos, 0.5 mm/min, 50Kgf) was performed 24h after etching and cementing (RelyX ARC, 80m) 60 square ceramic plates (5x5mm, 1mm thick; n = 10), varying R and U adhesive systems (10R, 20R, 60R, 10U, 20U and 60U). The same pattern of damage was maintained as seen in the SEM analysis, however, it worsened with increasing the etching time. The amounts of silicium seen on EDS were: E0: 24.73%

Optimizing light-cured composite through variations in camphorquinone and butylhydroxytoluene concentrations

Abstract The use of a free-radical polymerization inhibitor, butylhydroxytoluene (BHT), and a common photo-initiator, camphorquinone (CQ), to reduce polymerization stress in dental composite was investigated in this study. Samples were prepared by mixing Bis-GMA, UDMA, and TEGDMA at a 1:1:1 ratio (wt%), and silanized borosilicate glass fillers at 70 wt% were added to form the composite. Sixteen groups of resin composite were prepared using combinations of four CQ (0.1%, 0.5%, 1.0%, and 1.5%) and four BHT (0.0%, 0.5%, 1.0%, and 1.5%) concentrations. For each group, six properties were tested, including flexural strength (FS), flexural modulus (FM), degree of conversion (DC), contraction stress (CS), stress rate, and gel point (GP). The effects of CQ and BHT combinations on each of these properties were evaluated using two-way analysis of variance (ANOVA) and Fisher's Protected Least Significant Differences test at the 5% significance level. Groups with low CQ and BHT showed moderate values for FS, FM, and CS with a 70% DC. Increasing the BHT concentration caused a decrease in CS and DC with an increase in GP values. Increasing the CQ content led to a steady increase in values for FS and FM. High CQ and BHT combinations showed the most promising values for mechanical properties with low stress values.

Relined fiberglass post: an ex vivo study of the resin cement thickness and dentin-resin interface

Abstract The aim of this study was to evaluate the thickness of resin cements in the root thirds when using conventional fiberglass posts (CP) and relined fiberglass posts (RP) in weakened roots and to evaluate the morphological characteristics of the dentin-resin interface. Forty human maxillary anterior teeth had the crown sectioned below the cemento-enamel junction. The canals were endodontically treated and weakened with diamond burs. Teeth were divided into four groups (n = 10): Group 1 - CP + RelyX ARC; Group 2 - CP + RelyX U200; Group 3 - RP + RelyX ARC; and Group 4 - RP + RelyX U200. Prior to luting, 0.1% Fluorescein and 0.1% Rhodamine B dyes were added to an adhesive and resin cement, respectively. Slices were obtained from the apical, middle, and cervical thirds of the root. Confocal laser scanning microscopy images were recorded in four areas (buccal, lingual, mesial, distal) of each third. In each area, four equidistant measures of the resin cement were made and the mean value was calculated. The interface morphology was observed. The data were submitted to three-way ANOVA and Tukey's test (α = 0.05). The interaction between fiberglass posts, resin cement, and root thirds was significant (p < 0.0001). The resin cement thicknesses were significantly lower for RP in comparison with CP, except in the apical third. There was no significant difference between the resin cements for RP. There was formation of resin cement tags and adhesive tags along the root for RP. RP favored the formation of thin and uniform resin cement films and resin tags in weakened roots.

Does the Moment of Fiber Post Cutting Influence on the Retention to Root Dentin?

Despite several advantages associated with pre-fabricated glass-fiber posts, the coronal portion of these posts must be cut to allow their use in various clinical situations. However, cutting the cemented post can generate stress on the bonding interface and affect the bond strength. The aim of this study was to investigate the effect the of fiber post cutting on the bond strength of root canals. Sixty bovine incisor roots were included in resin cylinders with simulated periodontal ligaments. Glass-fiber posts were luted using regular resin cement RelyX ARC (3M ESPE) or self-adhesive cement RelyX Unicem (3M ESPE). The posts were cut prior to cementation, immediately after luting or after building up the core (n=10). After storage for 24 h, the samples were cut and subject to push-out testing using a mechanical testing machine (EMIC DL 2000). Data were analyzed using two-way ANOVA (resin cement x moment of post cutting) and Tukey's post hoc test (α=0.05). The moment of fiber post cutting did not affect the bond strength when Unicem was used. However, the bond strength was reduced when ARC was used and when the post was cut immediately. In conclusion, the moment of fiber post cutting may affect the retention of root canal posts when a regular resin cement is used.

Apesar das diversas vantagens associadas aos pinos de fibra de vidro pré-fabricados, o corte da sua porção coronária deve ser realizado para permitir seu uso em algumas situações clínicas. Entretanto, o corte do pino cimentado pode gerar tensões na interface adesiva e afetar a resistência de união. O objetivo deste estudo foi avaliar o efeito do momento do corte do pino na resistência de união ao canal radicular. Sessenta raízes de incisivos bovinos foram incluídas em cilindros de resina com simulação do ligamento periodontal. Pinos de fibra de vidro foram cimentados utilizando um cimento resinoso convencional RelyX ARC (3M ESPE) ou autoadesivo RelyX Unicem (3M ESPE). Os pinos foram cortados previamente à cimentação, imediatamente após a cimentação, ou após a reconstrução do núcleo de preenchimento (n=10). Após o armazenamento por 24 h, as amostras foram seccionadas e submetidas ao ensaio de cisalhamento por extrusão utilizando máquina de ensaio mecânico (EMIC DL 2000). Os dados foram analisados por ANOVA dois fatores (cimento resinoso x momento do corte do pino) e teste de Tukey (=0,05). O momento do corte do pino de fibra de vidro não afetou a resistência de união quando o RelyX Unicem foi utilizado. No entanto, o corte do pino imediatamente após a cimentação reduziu os valores de resistência de união quando o RelyX ARC foi utilizado. Em conclusão, o momento do corte do pino pode afetar a resistência de união ao canal radicular quando o cimento resinoso convencional for utilizado.

O papel da concentração de nanofibras e da composição da matriz resinosa nas propriedades flexurais de compósitos experimentais baseados em nanofibras / Flexural properties of experimental nanofiber reinforced composite are affected by resin composition and nanofiber/resin ratio

O objetivo do presente estudo foi de avaliar a influência de soluções de resina com diferentes proporções de monômeros e diferentes concentrações em massa de nanofibras nas propriedades flexurais de compósitos resinosos experimentais reforçados com nanofibras de poliacrilonitrila (PAN). Materiais e métodos: Nanofibras de PAN foram produzidas pelo processo de eletrofiação e caraterizadas por teste de tração e microscopia eletrônica de varredura (MEV). Os compósitos experimentais foram produzidos pela infiltração das mantas de nanofibras com diferentes misturas de BisGMA-TEGDMA (BisGMA/TEGDMA: proporções em % massa de 30/70, 50/50, e 70/30). Foram incorporadas diferentes concentrações em massa de nanofibras (de 0% a 8%). Espécimes em forma de barra foram seccionados a partir de blocos do compósito experimental e armazenados em água na temperatura de 37oC por 24h anteriormente à realização dos testes de flexão de três pontos. Foram avaliados a resistência flexural (RF), o módulo flexural (MF) e o trabalho de fratura (TF). Resultados: Os testes de tração das nanofibras de PAN demonstraram um comportamento anisotrópico das mantas de nanofibras. As propriedades mecânicas exibiram maiores valores na direção perpendicular ao eixo de rotação do coletor metálico utilizado na produção das fibras por eletrofiação. Maiores proporções de BisGMA nas misturas de resina resultaram em maiores valores de RF e MF, o que não ocorreu para os valores de TF. A adição de diferentes concentrações de nanofibras não afetou as propriedades de RF e MF em comparação com o grupo controle (resina pura) (p>0.05). No entanto, a adição das nanofibras promoveu um aumento significante do TF, principalmente para as misturas de resina com maior proporção de TEGDMA (p<0,05). Significância: A inclusão de nanofibras de PAN em resinas de modo a formar compósitos resinosos reforçados por nanofibras não afetou negativamente as propriedades flexurais do material e resultou em um aumento significativo da...

The present study had the objectives to evaluate the influence of different resin blends concentrations and nanofibers mass ratio on flexural properties of experimental Poliacrylonitrile (PAN) nanofibers reinforced composite. Materials and Methods: Poliacrylonitrile (PAN) nanofibers mats were produced by electrospinning and characterized by tensile testing and scanning electron microscopy (SEM). Experimental resin-fiber composite beams were manufactured by infiltrating PAN nanofiber meshs with varied concentrations of BisGMA-TEGDMA resin blends (BisGMA/TEGDMA: 30/70, 50/50 and 70/30 weight %). The mass ratio of fiber to resin varied from 0% to 8%. Beams were cured and stored in water at 37oC. Flexural strength (FS), flexural modulus (FM) and work of fracture (WF) were evaluated by three-point bending test after 24 hs storage. Results: The tensile properties of the PAN nanofibers indicated an anisotropic behavior being always higher when tested in a direction perpendicular to the rotation of the collector drum. Except for WF, the other flexural properties (FS and FM) were always higher as the ratio of BisGMA to TEGDMA increased in the neat resin beams. The addition of different ratios of PAN fibers did not affect FS and FM of the composite beams as compared to neat resin beams (p>0.05). However, the addition of fibers significantly increased the WF of the composite beams, and this was more evident for the blends with higher TEGDMA ratios (p<0.05). Significance: The inclusion of PAN nanofibers into resin blends did not negatively affect the properties of the composite and resulted in an increase in toughness that is a desirable property for a candidate material for restorative application.