Resistência de união e estabilidade de um sistema adesivo universal à dentina erodida/abrasionada após desproteinização

Os desafios erosivos promovem alterações na estrutura dental, podendo levar à perda do esmalte e exposição da dentina subjacente. O contato frequente da dentina exposta com uma substância ácida leva à desmineralização de sua camada superficial, ocasionando, ao menos in vitro, a exposição de uma malha rica em fibras colágenas com espessura considerável. Este trabalho se propõe a verificar os efeitos da abrasão promovida pela escovação e da aplicação de hipoclorito de sódio a 10% sobre a matriz orgânica da dentina erodida, visando determinar as consequências de tais condições na resistência de união (RU) de um sistema adesivo universal. Espécimes de dentina bovina foram divididos em cinco grupos de acordo com a condição da matriz orgânica (n=20): Controle (C); Erosão (E); Erosão + Abrasão (EA); Erosão + Hipoclorito (EH); Erosão + Abrasão + Hipoclorito (EAH). Em seguida, os grupos foram novamente divididos (n=10) de acordo com a aplicação do Sistema Adesivo Universal (condicionamento total ou autocondicionamento). Foram confeccionados blocos de resina composta sobre as superfícies tratadas e obtidos palitos para o teste de microtração. Metade dos palitos obtidos de cada espécime foi testada imediatamente, a outra metade foi testada após envelhecimento artificial (5000 termociclos/ 5 e 55oC) utilizando-se uma Máquina de Ensaios Universal à velocidade de 1mm/min. Através do teste ANOVA foi observada diferença estatisticamente significante para a interação entre os três fatores estudados (p=0,0007). Os maiores valores médios de RU foram obtidos pelos grupos EH e EAH, tanto para os grupos imediatos como para os submetidos a envelhecimento artificial, e também para ambas as técnicas adesivas. O grupo controle apresentou valores médios de RU similares aos grupos E e EA, para ambas as técnicas adesivas. Conclusões: A erosão e a erosão/abrasão não influenciaram significativamente a RU à dentina. A técnica de desproteinização promoveu a manutenção da estabilidade adesiva à dentina erodida e a dentina erodida submetida à abrasão, especialmente quando a técnica de condicionamento total foi utilizada. O envelhecimento artificial reduziu os valores de RU apenas para os grupos C, E e EA quando a técnica de condicionamento total foi utilizada.The erosive challenges promote changes in tooth structure and may lead to enamel loss and the exposure of underlying dentine. The frequent contact of exposed dentine with an acidic substance leads to demineralization of its surface layer, leaving, at least under in vitro conditions, a mesh rich in collagen fibrils with considerably thickness. This study intended to verify the effects of abrasion by brushing and the application of sodium hypochlorite 10% on the organic matrix of eroded dentine, to determine the consequences of such conditions on the microtensile bond strength (μTBS) of a universal adhesive, immediately and after artificial aging. Specimens of bovine dentin were divided into five groups according to the organic matrix treatment (n=20): Control (C); Erosion (E); Erosion + Abrasion (EA); Erosion + Sodium hypochlorite (EH); Erosion + Abrasion + Sodium hypochlorite (EAH). The groups were further divided (n=10) according to the application of a Universal Adhesive System (total etching or self etching). Blocks of resin composite were bonded to the samples and sticks were obtained for μBS test. One half of the sticks of each specimen was immediately tested and the other half was tested after artificial aging (5000 thermocycles/5 and 55oC). Results: ANOVA showed significant difference for the interaction between the three studied factors (p=0.0007). The higher μTBS means were obtained by EH and EAH groups as for immediate as for aged data, and for both adhesive techniques. The control group showed similar μTBS means to E and EA groups, for both adhesive techniques. Conclusions: Erosion and erosion/abrasion did not significantly influence the μTBS to dentin. The deproteinization technique maintained the bond stability to the eroded and eroded/abraded dentin, especially when using the total etching technique. The artificial aging reduced μTBS values only for groups C, E and EA using the total etching technique.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Film-Forming Polymers for Tooth Erosion Prevention

Different agents have been proposed to prevent the progression of acid induced dental substance losses, which are called erosive tooth wear (ETW), such as fluorides, calcium, and phosphate-based products; however, there is a need for a further increase in efficacy. Recently, the ability of polymers to interact with the tooth surface, forming acid resistant films, has come into the focus of research; nevertheless, there is still the need for a better understanding of their mode of action. Thus, this article provides an overview of the chemical structure of polymers, their mode of action, as well as the effect of their incorporation into oral care products, acid beverages, and antacid formulations, targeting the prevention of ETW. Recent evidence indicates that this may be a promising approach, however, additional studies are needed to confirm their efficacy under more relevant clinical conditions that consider salivary parameters such as flow rate, composition, and clearance. The standardization of methodological procedures such as acid challenge, treatment duration, and combination with fluorides is necessary to allow further comparisons between studies. In conclusion, film-forming polymers may be a promising cost-effective approach to prevent and control erosive demineralization of the dental hard tissue

Desgaste das cerâmicas odontológicas

Based on the development of adhesive dentistry, minimally invasive restorations in ceramics are used as alternatives to restore a tooth. Dental ceramics are largely applied in the dentistry field mainly due to their esthetic and mechanical strength. One of the ceramic properties to be well known before its use is the wear resistance that should be compatible with the antagonist wear behavior to avoid unwanted performance. Therefore, several methods have been performed to assess the ceramic materials wear behavior considering different conditions present in the complex oral medium. This study aimed to compile the methods used to investigate dental ceramics wear and to describe the wear mechanisms involved on them. Obtaining and analyzing data is also addressed to discuss the results obtained from different methods, as well as the clinical analysis of wear and future perspectives on this topic. In conclusion, many methodologies are available to measure the ceramic wear. Therefore, the methods must be selected based on the clinical significance of each study and should follow previously reported parameters for standardization, allowing literature comparison

Comparison of Polishing Systems on the Surface Roughness of Resin Based Composites Containing Different Monomers

Changes in the organic matrix of composite resins have been proposed to improve their surface properties. However, polishing systems may perform differently in different materials. This study compared the effect of polishing systems on the surface roughness of four composite resins containing different resin monomers: Admira Fusion (nanohybrid containing pure ormocer), Aura Bulkfill (nanohybrid containing Bis-GMA, UDMA), Charisma Diamond (nanohybrid containing TCD-DI-HEA) and Vittra APS (nanofilled containing UDMA). Cylinders (N = 120, n = 10) were prepared from each material and the top surface of each specimen was grounded using a diamond finishing bur. Baseline measurements of surface roughness (Ra) were recorded using a contact profilometer and the specimens of each composite were divided into three subgroups according to the polishing system: one-step, two-step, three-step. Ra measurements were recorded also after polishing. Data were analyzed using three-way ANOVA and Tukey’s test (p < 0.05). The baseline roughness of all composites was significantly reduced after polishing (p < 0.001). The two-step polishing system provided the smoothest surface for Admira Fusion (0.0770 ± 0.0171) and Charisma (0.1091 ± 0.0090), whereas for Aura and Vittra no significantly differences were found for the three polishing systems tested. The surface smoothness seems to be more material dependent than step dependent, but all tested systems provided clinically acceptable results

Influence of different post-endodontic restorations on the fatigue survival and biomechanical behavior of central incisors

Purpose: To evaluate the influence of different post-endodontic techniques on the fatigue survival and biomechanical behavior of crowned restored central incisors. Methods: The crowns of 69 bovine incisors were cut, and the roots were treated endodontically and assigned randomly into three groups (n=23): resin composite buildup (BUP), glass fiber post-retained resin composite buildup (GFP), and cast post-and-core (CPC). They received full crown preparation with 2 mm ferrule, and a leucite-reinforced ceramic crown was cemented adhesively. Three specimens from each group were tested monotonically. The remaining specimens were subjected to the stepwise stress fatigue test until fracture or suspension after 1.5 × 106 cycles in a chewing simulator. The load and step at which each specimen failed were analyzed by Kaplan-Meier and Mantel-Cox (log-rank test) statistics, followed by multiple pairwise comparisons, at 5% significance level. The three groups tested (BUP, GFP, and CPC) were 3D modeled (Rhinoceros 4.0) and the maximum principal stress (MPa) criteria were used to calculate the results using FEA. Results: There was no statistical difference between the treatments regarding the load or the number of cycles (Mantel-Cox log-rank test for trend, X2= 0.015, df=l, P= 0.901, X2 =3.171, df=l, P= 0.995). Crown cracks were the predominant failure mode, and oblique root fractures were only observed in groups GFP and CPC. In endodontically treated incisors with a 2-mm ferrule, the post-endodontic treatment had no significant effect on fatigue survival. Non-restorable fractures only occurred in teeth restored with posts

Comparison of Different Dentin Pretreatment Protocols on the Bond Strength of Glass Fiber Post Using Self-etching Adhesive

Introduction: This study compared the influence of different irrigants with and without ultrasound or laser irradiation on the bond strength of glass fiber posts using a self-etching adhesive in a supplementary dentin pretreatment. Methods: Ninety bovine incisor roots were divided into 3 groups according to the irrigant tested: 2% chlorhexidine (CHX) (n = 30); 2.5% sodium hypochlorite (NaOCl) (n = 30), and saline solution (control) (n = 30). Each group was randomly divided into 3 subgroups according to the supplementary dentin pretreatment: ultrasound, Nd:YAG laser, and nonsupplemented (control). A self-etching adhesive system (Futurabond DC; VOCO GmbH, Cuxhaven, Germany) was used, and the glass fiber posts were cemented with dual-cure epoxy-based luting agent (Bifix QM, VOCO GmbH). All roots were sectioned transversely, and the push-out test was performed. Failure mode analysis was also evaluated. Results: Bond strength decreased significantly after the use of 2.5% NaOCl in all root thirds (P &lt; .05). CHX showed no difference in the mean bond strength value compared with saline solution (P &gt; .05). The supplementary dentin pretreatment using the Nd:YAG laser or ultrasound did not improve the bond strength values for both NaOCl and CHX (P &gt; .05). Moreover, the apical third exhibited the lowest mean bond strength values (P &lt; .05). Analysis indicated that the predominant failure mode was the mixed type.. Conclusions: Regardless of the irrigant used, the supplementary dentin pretreatment with ultrasound or laser irradiation showed no improvement in bond strength. Also, the use of NaOCl decreased the bond strength of glass fiber posts using a self-etching adhesive system, whereas CHX preserved it.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq