English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

This in-vitro study aimed to evaluate microtensile bond strength and nanoleackage of dentin surfaces pretreated with different etching materials. Twenty four extracted human intact second molar were selected and debrided to remove remnants of periodontal ligaments. Occlusal surfaces were flattened to expose a flat area of dentin under copious water coolant. One dentin bonding system (Te-Econom Bond) and one dental resin composite restoration (Tetric N-Ceram) were used for the study. The teeth were divided into four groups (6 each) according to the type of etchant material used as follows: group A – citric acid 6%, group B – citric acid 10%, group C – citric acid 20%, and group Dphosphoric acid 37%. The etchants were applied for 15 seconds to the dentin surface. After which teeth were washed, dried, then bonding agent was applied followed by the resin composite restoration. Then a longitudinal sectioning of restored teeth was made to obtain composite-dentin beams of (0.9 x 0.9 mm) in area. Each beam was composed of composite and dentin with adhesive at the interface. The microtensile bond strength (μTBS) was measured and the nanoleakage was observed using SEM. Data was then recorded, tabulated and statistically analyzed. There was no statistical significant difference between the results of the μTBS of groups A, B and D while group C has the lowest microtensile bond strength (19.20± 4.59). For all groups, nanoleackage was more demonstrated at group C and D, while group B show mild nanoleackage and no nanoleackage was observed for group A. It was concluded that low concentrations of citric acid was effective as etchant material compared to phosphoric acid on dentin surface in terms of microtensile bond strength and nanoleakage. (4004) Ahmed Adel A. Aziz and Heba Fathy El Imam E.D.J. Vol. 64, No. 4 turn enhanced the bond strength [1]. However, acid conditioning was the only way to remove apatite of dentin and hence resin infiltration occurred into intertubular dentin [2]. The tooth surface to which the bond has to occur is mostly covered with a loosely bonded smear layer with thickness between 0.05 and 15 μm after cavity preparation. It is composed of shattered and crushed hydroxyapatite, along with denatured and fragmented collagen. Bacteria and saliva may be found as contaminants within smear layer in vivo. This smear layer affect the bonding surface negatively as it reduces the bond to the underlying dentin. Thus, to eliminate the effect of smear layer and promote bonding, different surface treatment agents have been proposed to remove or modify the smear layer before placing the restoration [3]. A moderate to severe pulpal reactions can be resulted from acid etching but it was found that these reactions are highly caused by microleakage of the bacteria and their byproducts [4]. To enhance the adhesion in preventive and restorative dentistry, etching to dentin was used as it was considered as a surface preparation step to remove any surface debris after tooth cutting. Furthermore, acid etching has been reported to reduce microleakage around restoration margins and provide cuspal reinforcement [3]. Various commercially used acidic materials in the dental adhesive systems were applied to etch both enamel and dentin. These acidic materials are used to eliminate or remove the smear layer from the cut dentin surface and cause dentin demineralization to a certain depth besides leaving behind a network rich of collagen in order to interact with the adhesive resin and finally a hybrid layer formation was obtained [6]. Different acid etchants have been used for removing the smear layer and demineralizing the dentin surface. Thus, it allows for penetration of bonding resins and formation of tags [7]. Total etch adhesive system is a technique in which the full etching of dental substrate by phosphoric acid is first done followed by the application of both primer and bond, which can be presented in a single or in separate bottles. The self-etching systems were relevant and used nowadays as they have several advantages over the total etch techniques from which are its simplicity, convenience and time saving because no etching step is required [8]. The application of phosphoric acid creates a pattern with more retentive areas in enamel. Some researches advocated the use of total etch techniques in case of making indirect restorations or when large areas of enamel were present. Also it has been proved that the application of 37% phosphoric acid to dentin in some cases may have resulted in excessive demineralization and so there is improper resin infiltration in the collagen fibers which in turn resulted in poor adhesion [9]. Citric acid is a weak organic acid that has different functions as natural preservative substance, cleansing material and antioxidant used to add sour taste in food and soft drinks, found in fruit especially citrus and vegetable. Citric acid affects the dentin by causing permanently demineralized dentin surface by erasing or the removal of smear layer and the most superficial dentin and opening of the dentin tubules and exposing the collagen. It can be very erosive due to the capability to bind metal ion. The influence of citric acid was observed if it contacts the enamel or dentin surfaces. Enamel surface which is etched by citric acid will be erosive. It was found that when using excessive amount or high concentrations of citric acid on enamel and dentin surfaces can result in highly erosive demineralization and hence affect the adhesion [10]. Microtensile bond strength has always been used to evaluate the bond strength of the dentin adhesive restorations [11]. Also, Scanning Electron Microscopy (SEM) has been used traditionally as a method of assessment for the presence of nanoleakage as it demonstrated the different layers the dentin-adhesive-resin joint [12]. Therefore, the aim of the present study was to MICROTENSILE BOND STRENGTH AND NANOLEACKAGE OF DENTIN (4005) evaluate microtensile bond strength and nanoleackage of dentin surfaces pretreated with different concentrations of citric acid compared to 37% phosphoric acid. MATERIALS AND METHODS Different materials used in this study including the composition and manufacturer of each material are presented in Table 1: Etching materials: citric acid 6%, citric acid 10%, citric acid 20% and phosphoric acid 37%. Bonding agent: Te-Econom Bond Light-curing, radiopaque nano-hybrid composite resin restoration: Tetric N-Ceram Light curing unit: Bluephase N MC LED For the preparation of citric acid etching solutions, a 100ml pipette was filled with distilled water then, using a sensitive digital scale: 6 gm of citric acid powder were weighted and added to the 100ml distilled water to prepare the citric acid 6%. 10 gm of citric acid powder were weighted and added to the 100 ml distilled water to prepare the citric acid 10%. 20 gm of citric acid powder were weighted and added to the 100 ml distilled water to prepare the citric acid 20%. After that the solution was shacked well to make sure that the citric acid powder has completely dissolved in the distilled water. A total of twenty four freshly extracted human intact second molars were selected for this study. They were debrided to remove remnants of periodontal ligaments. The teeth were stored in normal saline at room temperature till use. The selected teeth were divided into four groups (6 each) according to different etchant acid used as follows: Group A – citric acid 6%, Group B – citric acid 10%, Group C – citric acid 20%, and Group Dphosphoric acid 37%. Occlusal surfaces were flattened to the level of the dentino-enamel junction using microtome to expose a flat area of dentin under copious water coolant. Different etching acids were applied for 15 seconds to the dentin surface with different applicator tips for each new sample. The surfaces were washed with water and air dried. Then, bonding agent was applied using Te-Econom Bond and light cured using bluephase N MC LED light curing unit for 20 seconds. The reduced occlusal surface was built with 3 mm layer by layer using Tetric N-Ceram resin composite restoration and light cured to facilitate longitudinal sectioning of the restored teeth. For easily distinguishing between different acids used, color coding was done for each group by applying permanent ink on the occlusal surfaces of the restored teeth as follows: red for citric acid 6%, green for citric acid 10%, black for citric acid 20% and blue for phosphoric acid 37%. The restored teeth were kept at 37°C with relative humidity for 24 hours in an incubator. Microtensile bond strength test Sixteen teeth were used for the microtensile bond strength test, each four representing each of the four groups. Cylindrical Teflon mold (15-mm diameter and 40-mm height), with a corresponding metal ring with two opposing screws at its top was used to produce acrylic resin blocks. The screws were used to hold the tooth in place in a centralized position, parallel to the long axis of the mold, during the setting of acrylic resin. Teeth fixed in acrylic resin blocks were then mounted in an automated diamond saw. Then longitudinal sectioning of restored teeth was made to obtain composite-dentin beams of (0.9 mm x 0.9 mm). Each beam was composed of composite and dentin with adhesive at the interface. Ten beams were collected from each tooth. For the longitudinal sectioning to be perpendicular to the flat occlusal surface of restored teeth, (4006) Ahmed Adel A. Aziz and Heba Fathy El Imam E.D.J. Vol. 64, No. 4 a specially designed gripping attachment was used to hold acrylic blocks with mounted teeth firm in place, parallel to the sectioning direction, thus maintaining the perpendicular relation between the cutting disc and the occlusal surface. After mounting in the gripping attachment, restored teeth were serially sectioned, using a 0.3-mm thick diamond coated disc, at 2050 rpm; 8.8 mm/min feeding rate; under copious

MICROTENSILE BOND STRENGTH AND NANOLEACKAGE OF DENTIN SURFACES PRETREATED WITH DIFFERENT ETCHING MATERIALS