Dentin bond strength and nanoleakage of the adhesive interface after intracoronal bleaching.

This study evaluated dentin bond strength (BS) and nanoleakage of non- and pre-etched dentin immediately (T0 ,), 7 days (T7 ), and 14 days (T14 ) after bleaching. Bovine incisors (150) were selected and half of them submitted to intrapulpal dentin etching (e). Non- and pre-etched dentin were subjected to the following (n = 15): no bleaching/control (C); 35% carbamide peroxide (CP); 35% hydrogen peroxide (35% HP); 25% hydrogen peroxide (25% HP); and sodium perborate (SP). Bleaching agents were applied to the pulp chamber four times within a 72-h interval. Afterwards, pulp chamber dentin was prepared for the BS test at different evaluation times (n = 5): T0 , T7 , and T14 . Composite blocks were built on pulp chamber and sectioned in slices. Slices were reduced to an hour-glass shape with a cross-sectional area of 0.8 mm2 and submitted to microtensile BS test. Two additional specimens for each group were prepared for nanoleakage evaluation by transmission electron microscopy (TEM). Results were analyzed by ANOVA (two-way) and Dunnett's test (p < .05). BS decreased immediately after intracoronal bleaching for both sound and pre-etched dentin (p < .05). At T14 , the BS of non-etched bleached dentin increased for all groups, whereas the pre-etched SPe group presented BS similar to the Ce. Nanoleakage within the hybrid layer was perceptible immediately after bleaching, although a decrease in nanoleakage was observed for all groups at T14 . Adhesive restorations should be performed 7-14 days after bleaching, according to the bleaching agent used. Intracoronal bleaching should be performed preferably with sodium perborate if previous dentin etching is applied.

Comparative bonding ability to dentin of a universal adhesive system and monomer conversion as functions of extended light curing times and storage.

OBJECTIVES: The purpose of this in vitro study was to evaluate the bonding ability and monomer conversion of a universal adhesive system applied to dentin as functions of different curing times and storage. The results were compared among a variety of commercial adhesives. MATERIALS AND METHODS: Flat superficial dentin surfaces were exposed on human molars and assigned into one of the following adhesives (n = 15): total-etch Adper Single Bond 2 (SB) and Optibond Solo Plus (OS), self-etch Optibond All in One (OA) and Clearfil SE Bond (CSE), and Scotchbond Universal Adhesive in self-etch mode (SU). The adhesives were applied following the manufacturers' instructions and cured for 10, 20, or 40s. Specimens were processed for the microtensile bond strength (µTBS) test in accordance with the non-trimming technique and tested after 24h and 2 years. The fractured specimens were classified under scanning electron microscopy (SEM). Infrared (IR) spectra were obtained and monomer conversion (%) was calculated by comparing the aliphatic-to-aromatic IR absorption peak ratio before and after polymerization (n=5). Data were analyzed by 2-way ANOVA/Tukey's tests (α = 0.05). RESULTS: At 24-h evaluation, OA and CSE presented similar bond strength means irrespective of the curing time, whereas SB and SU exhibited significantly higher means when cured for 40s as did OS when cured for 20 or 40s (p < 0.05). At 2-year evaluation, only OA exhibited significantly higher bond strength when cured for 20 and 40s (p < 0.05). When the evaluation times were compared, OA also exhibited the same bonding ability when cured for longer periods of time (20 and 40s). All of the adhesives tested exhibited significantly lower monomer conversion when photoactivated according to the manufacturers' instructions (10s). CONCLUSIONS: Higher monomer conversions obtained with longer light exposure allow only higher immediate bond strength for most of the adhesives tested. After 2-year storage, only the self-etching adhesive Optibond All-In-One exhibited the same bonding ability when cured for longer periods of time.

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

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.

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.

The influence of hemostatic agents on dentin and enamel surfaces and dental bonding: a systematic review.

BACKGROUND: Hemostatic agents have been used clinically in dentistry for many years to control bleeding. The authors reviewed scientific publications in which researchers investigated the effects of hemostatic agents on dentin and enamel surfaces and on bonding of adhesive systems and resin cements. TYPES OF STUDIES REVIEWED: The authors screened PubMed and Scopus databases for studies in English published from 1980 to 2013. They read the titles and abstracts to identify literature that fulfilled the inclusion criteria. The authors included studies in which researchers evaluated the hemostatic action on the dentin and enamel surfaces or its influence on the bond strength of adhesive systems or resin cements. They used cross-referencing to identify more articles. RESULTS: Twenty in vitro studies met the inclusion criteria. Investigators in 12 of these studies evaluated the bond strength to contaminated dentin. Investigators in 10 of these studies reported a significant decrease in bond strength. Those in two studies evaluated the influence of a hemostatic agent on the dental enamel and reported decreases in bond strength. Researchers also reported significant increases in microleakage of self-etching adhesives on contaminated dentin. Scanning electron microscopy revealed partial removal of the smear layer or an etching effect of dentin as a result of the application of hemostatic agents on dentin. PRACTICAL IMPLICATIONS: Adhesive procedures may be affected adversely when performed on dentin and enamel contaminated by hemostatic agents. Hemostatic agents may induce changes in the dentin surface morphology. The results of this review indicate that the bond strength of self-etching adhesive systems is affected more negatively than is that of etch-and-rinse systems. The authors found that a 60-second application of ethylenediaminetetraacetic acid followed by a water spray restored the bond strength of a self-etching adhesive to dentin; use of phosphoric acid for 15 seconds followed by a water spray also was an effective cleaning method. Direct comparison of selected studies was not possible, however, mainly because of methodological differences hampering definitive conclusions.

Long-term stability of dentin matrix following treatment with various natural collagen cross-linkers.

OBJECTIVES: Collagen disorganization is one of the main degradation patterns found in unsuccessful adhesive restorations. The hypothesis of this study was that pretreatment using natural collagen cross-linking agents rich in proanthocyanidin (PA) would improve mechanical properties and stability over time of the dentin collagen and, thus, confer a more resistant and lasting substrate for adhesive restorations. METHODS: PA-based extracts, from grape seed (GSE), cocoa seed (CSE), cranberry (CRE), cinnamon (CNE) and açaí berry (ACE) were applied over the demineralized dentin. The apparent elastic modulus (E) of the treated dentin collagen was analyzed over a 12 month period. Specimens were immersed in the respective solution and E values were obtained by a micro-flexural test at baseline, 10, 30, 60, 120 and 240 min. Samples were stored in artificial saliva and re-tested after 3, 6 and 12 months. Data was analyzed using ANOVA and Tukey test. RESULTS: GSE and CSE extracts showed a time-dependent effect and were able to improve [240 min (MPa): GSE = 108.96 ± 56.08;CSE = 59.21 ± 24.87] and stabilize the E of the organic matrix [12 months (MPa): GSE = 40.91 ± 19.69;CSE = 42.11 ± 13.46]. CRE and CNE extracts were able to maintain the E of collagen matrices constant over 12 months [CRE = 11.17 ± 7.22;CNE = 9,96 ± 6.11;MPa]. ACE (2.64 ± 1.22 MPa) and control groups immersed in neat distilled water (1.37 ± 0.69 MPa) and ethanol-water (0.95 ± 0.33 MPa) showed no effect over dentin organic matrix and enable their degradation and reduction of mechanical properties. SIGNIFICANCE: Some PA-based extracts were capable of improving and stabilizing collagen matrices through exogenous cross-links induction.

Effects of surface texture and etching time on roughness and bond strength to ground enamel.

AIM: The aim of this study was to assess the influence of surface texture and etching technique on surface roughness (Ra) and bond strength (BS) to enamel and to determine if a correlation exists between them. METHODS AND MATERIALS: Fifty enamel blocks were either roughened with 600-grit SiC paper or polished with diamond pastes. After establishing ten test groups (n=5), the initial Ra measurements, rough (R) and smooth (S) enamel surfaces were etched according to the following protocols: Group 1(R)/Group 2(S)- 35% phosphoric acid gel (H3PO4) for 15 seconds; Group 3(R)/Group 4(S)- 35% H3PO4 for 60 seconds; Group 5(R)/Group 6(S)- Clearfil SE Bond primer for 20 seconds; Group 7(R)/Group 8(S)- self-etching primer (SEP) for 60 seconds; Group 9(R)/Group 10(S)- 35% H3PO4 for 15 seconds + SEP for 20 seconds. After treatments, a new Ra measurement was performed and enamel surfaces were bonded with either Single Bond (Group 1 to Group 4) or Clearfil SE Bond (Group 5 to Group 10). Afterwards, specimens were prepared for the microtensile test. Ra values were analyzed using repeated-measures analysis of variance (ANOVA) and the BS values were analyzed using a two-way ANOVA and Tukey test (5%). Correlation between BS and Ra values was assessed using the Pearson's test. RESULTS: The application of SEP produced the lowest Ra values. No significant difference was detected between the BS values of polished and rough surfaces. No correlation was observed between Ra and BS values. Even though etching enamel with the SEP resulted in a surface with less roughness, similar BS values were observed for both self-etching and etch-and-rinse techniques. CONCLUSION: Within the limits of this study increasing the etching time or combining both etching techniques failed to improve the BS using SEP or etch-and-rinse systems. CLINICAL SIGNIFICANCE: Based on the findings of this study, there is no clinical justification for increasing the etching time or for combining the use of a SEP following the use of a 35% H3PO4 etchant to achieve a greater BS to ground enamel.

Effect of propionaldehyde or 2,3-butanedione additives on the mechanical properties of Bis-GMA analog-based composites.

OBJECTIVES: The purpose of this study was to evaluate the effect of two additives, propionaldehyde/aldehyde or 2,3-butanedione/diketone, on mechanical properties of Bis-GMA-based composites containing TEGDMA, propoxylated Bis-GMA (CH(3)Bis-GMA) or propoxylated fluorinated Bis-GMA (CF(3)Bis-GMA). METHODS: Three control composites, Bis-GMA/diluent monomer (25/75 mol%), and six test composites, Bis-GMA/diluent monomer/aldehyde or diketone (17/51/32 mol%) were prepared. All composites contained hybrid treated filler (barium aluminosilicate glass/pyrogenic silica; 60 wt%), and 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Degree of conversion (DC%), flexural strength (FS), modulus of elasticity (E), modulus of resilience (R) and diametral tensile strength (DTS) were determined. DC% (n=3) was investigated by FT-IR. For FS and E, beam-shaped specimens (25mm x 2mm x 2mm) were prepared (n=6), stored for 7 days in 37 degrees C deionized water and tested on an Instron utilizing a three-point loading jig (0.5mm/min). The R-values were obtained from the following equation: R=(FS)(2)/2E. For DTS, cylindrical specimens (4mm x 8mm) were prepared (n=6), stored for 7 days in 37 degrees C deionized water and diametrically loaded on an Instron (0.5mm/min). Data were analyzed by one-way ANOVA and Tukey's test (alpha=0.05). RESULTS: Incorporation of additives led to an increase in DC%, FS and E for Bis-GMA/TEGDMA and Bis-GMA/CH(3)Bis-GMA systems. R-values for all systems were unaffected by addition of additives. They had no significant effect on DC% or mechanical properties of Bis-GMA/CF(3)Bis-GMA. SIGNIFICANCE: The findings correlate with the ability of additives to improve degree of conversion of some composite systems thereby enhancing mechanical properties.

Degradação das interfaces resina-dentina: uma revisão da literatura / Degradation of resin-dentin interfaces: a literature review

Restaurações adesivas vêm sendo amplamente utilizadas em diversos procedimentos odontológicos na atualidade. Diversas pesquisas demonstram uma união satisfatória dos materiais resinosos à dentina, principalmente logo após sua aplicação. No entanto, a efetividade dos procedimentos restauradores adesivos promovida por diferentes protocolos de aplicação tem sido questionada com relação à durabilidade da união ao substrato dentinário. A degradação da união, atribuída principalmente à hidrólise dos componentes resinosos e à digestão enzimática dos constituintes da interface, tem se mostrado mais severa para alguns sistemas adesivos do que para outros. O objetivo desta revisão de literatura foi abordar os possíveis mecanismos de degradação das interfaces resina-dentina obtidas com os diferentes protocolos de aplicação disponíveis atualmente. Foram analisadas as diferentes metodologias para estudar o comportamento das interfaces ao longo do tempo. Os estudos das propriedades físico-mecânicas das interfaces e da nanoinfiltração têm se mostrado ferramentas importantes para estimar a longevidade dos adesivos no meio oral. Os trabalhos mostram que a nanoinfiltração ocorre com diferentes severidades, mas praticamente em todos os adesivos. A maioria dos materiais mostra-se eficiente logo após a sua aplicação; no entanto, o comportamento da união ao longo do tempo ante a presença de água varia consideravelmente. Os adesivos autocondicionantes de passo único são os mais susceptíveis à degradação após armazenagem em água. De acordo com os trabalhos revistos, concluiu-se que a degradação da união está relacionada à hidrofilia dos materiais

Adhesive restorations have been increasingly used in many dental procedures in the latest years. Several studies have demonstrated an effective bonding to dentin, especially immediately after application. However, the effectiveness of adhesive restorative procedures has been questioned with regard to the durability of the bond to dentin substrate. Degradation of bonds has been attributed to hydrolysis of resinous components or to enzymatic digestion of the resin-dentin interface, and has been shown to occur in different rates for different adhesive systems. The aim of this literature review was to examine the possible degradation mechanisms of resin-dentin interfaces obtained with currently available adhesive systems of different application protocols. Different methods for studying resin-dentin interfaces behavior over time were examined. The studies of interfaces physicomechanical properties and nanoleakage patterns have been proven to be important tools for predicting the long-term behavior of adhesive systems in the oral environment. The studies have demonstrated that no adhesive system is able of totally preventing nanoleakage. Most adhesives proved to be effective right after application; however, the behavior of bonded interfaces after long-term water-storage varies considerably. Single-step self-etching adhesives are the most susceptible to degradation after storage in water. Based on the studies analyzed it can be concluded that degradation of bonds is related to the hydrophilicity of the materials .