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Year : 2014  |  Volume : 2  |  Issue : 1  |  Page : 32-36

Effect of different bonding techniques on the bond strength of two different fiber posts

1 Department of Restorative Dentistry, Faculty of Dentistry, Erciyes University, Kayseri, Turkey
2 Department of Prostodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey

Date of Web Publication20-Mar-2014

Correspondence Address:
Yahya Orçun Zorba
Department of Restorative Dentistry, Faculty of Dentistry, Erciyes University, Kayseri
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2321-4619.129019

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Aim: The aim of this study was to investigate the effect of three different bonding techniques on the bond strength of two different fiber posts to root dentin with push out test. Materials and Methods: A total of 30 extracted teeth were sectioned at the cement-enamel junction using a diamond disc under water-coolant to obtain 18 mm root length. All roots were treated endodontically and filled with sealer and Gutta-percha points. The roots were randomly divided into two groups according to chosen post systems (Rebilda DC [VOCO, Cuxhaven, Germany] or UniCore [Ultradent, South Jordan, UT]). Following preparation specimens were randomly divided into three subgroups of 3 teeth each. Luting of the posts were completed with Rebilda DC (self-etch); BisCem (self-adhesive, Bisco, Schaumburg, IL) Duo-Link (etch and rinse Bisco). Specimens were transversally sectioned into 2 ± 0.05 mm thick discs and push-out test was performed. The data was analyzed statistically by using three-way ANOVA and Tukey tests. Results: The bond strengths between fiber posts and root dentin were affected by type of resin cement and post ( P < 0.05). Push out bond strengths of Rebilda groups was lower than UniCore groups ( P < 0.05). Push out bond strength of DuoLink and Rebilda DC cement groups were higher than BisCem groups. There were no statistically differences between root region. Conclusion: It can be concluded that, bond strength between fiber post and root dentin affected by the using of different post and cement types. Self-adhesion techniques were showed lower bond strength than both self-etch and etch and rinse techniques

Keywords: Adhesive cements, bonding techniques, fiber post, push-out bond strength

How to cite this article:
Pala K, Demirbuga S, Gümüs HÖ, Arslan S, Zorba YO. Effect of different bonding techniques on the bond strength of two different fiber posts. J Res Dent 2014;2:32-6

How to cite this URL:
Pala K, Demirbuga S, Gümüs HÖ, Arslan S, Zorba YO. Effect of different bonding techniques on the bond strength of two different fiber posts. J Res Dent [serial online] 2014 [cited 2020 Jun 4];2:32-6. Available from: http://www.jresdent.org/text.asp?2014/2/1/32/129019

  Introduction Top

It is suggested that, failure in root canal treatment is close related to final restoration. Final restoration; must seal the access cavity effectively that microorganisms cannot enter the coronally, preserve radicular and coronal tooth tissues and final restoration must seem to be esthetic. [1]

In general, the remaining coronal tooth tissue at endodontically treated teeth is poor for a core restoration without using a post. Due to increasing demand for the esthetic restorations, clinicians may use fiber posts in a single visit, for the advantages of corrosion resistance, esthetic appearance. [2] Previous studies concluded that, both fiber posts had similar elasticity modulus of sound root dentin and might distribute occlusal stresses more evenly in the root dentin. [1],[3],[4]

Adhesive resin cements, which have an more closely match the elastic modulus with both the post and dentin, are commonly preferred to lute the post into root canal. [5] Selecting a correct luting procedure and adhesive technique for bonding posts to root dentine is a demanding issue. Previous studies have showed that the most common failure reason of the fiber post adhesion was caused by debonding between fiber post and resin cement or between resin cement and root canal walls. [6],[7] Luting with resin cements can be divided into three subgroups regarding to adhesion techniques used, which etch and rinse, self-etch and self-adhesive systems. [8]

There were a lot of studies about the bonding effectiveness of different luting agent. [1],[9] A previous study reported that, push-out bond strength of fiber post was affected numerous factors, such as; light transmitting into the post space, high polymerization shrinkage stress, anatomical differences between coronal and root dentin, the weak bond strength between fiber post and composites. [10]

Some studies showed no differences between the used luting techniques systems whilst others suggest etch and rinse techniques have a superiority than self-etch and self-adhesive techniques. [9] Furthermore in a different study, etch and rinse adhesives was showed significantly lower microleakage at the cement root dentin interface, than self-etching primer when used for fiber post cementation. [11]

A further improvement of reduction of working steps is introduction of "self-adhesive" cements. Self-adhesive cements are do not require pre-treatment of tooth substrates and posts. Self-adhesive cements can both infiltrate tooth substrate, which results micromechanical retention and offer chemical adhesion like glassionomers. [12]

Both self-etching and self-adhesive approaches provide simplicity and reduction in chair side-time. Although, there is no clarification about which fiber post luting method might be most useful. Therefore, the aim of this study was to investigate the effect of three different bonding techniques (etch-and-rinse, self-etch and self-adhesive) on the bond strength of two different fiber posts to root dentin with push out test. [8] The tested hypothesis was; both type of adhesive cements and posts do not affect bonding strength to dentin.

  Materials and Methods Top

A total of 30 freshly extracted teeth with a single and round root segment were selected for this study. Each tooth was placed in 5.25% of sodium hypochlorite (NaOCl) for 2 h for surface disinfection and then stored in distilled water. The crown of each tooth was sectioned at the cement-enamel junction using a diamond disc under water-coolant to achieve 18-mm root length. The working length was determined visually by subtracting 1 mm from the length of a size 10 file (K-Files Limas K; MANI, Tochigi, Japan) at the apical foramen. Root canals were prepared using the ProTaper (Dentsply, Konstanz, Germany) system to manufacturer recommendation. Nearly 1.25% NaOCl solution was used for irrigation after every change of instrument and lubricant (Glyde File Prep; Dentsply, Montigny-le-Bretonneux, France) was used throughout the shaping and cleaning of the root canal. Shaping was completed with a size F3 file at the working length. Finally, the canals were rinsed with 17% ethylenediaminetetraacetic acid and distilled water for removing the smear layer and dried with paper points. The roots were filled with sealer (MM-Seal, Micro Mega, Besancon, France) and Gutta-percha points (Diadent Gutta-Percha Points, DiaDent Group International, Chongju, Korea) by using the cold lateral condensation technique with a finger spreader (MANI, Tochigi, Japan). After root canal treatment was completed, roots were stored at 100% humidity at 37°C (EN 032, Nüve, İstanbul, Turkey) for 7 days to allow the sealer to set.

The roots randomly divided into two groups regarding to post systems (Rebilda DC [VOCO, Cuxhaven, Germany] or UniCore [Ultradent, South Jordan, UT]). The post holes were prepared with their own drills Rebilda DC or UniCore, up to a fixed depth of 12 mm [Figure 1]. 1.25% NaOCl solution was used after preparation of the root canals and distilled water was used for final flushing. The canals were dried with paper points. The samples were randomly divided into three subgroups of 3 teeth each. Luting of the posts were completed with Rebilda DC (self-etch) in group 1 and 4; BisCem (self-adhesive, Bisco, Schaumburg, IL) in group 2 and 5 and Duo-Link (etch and rinse Bisco) in group 3 and 6, according to the manufacturer's instructions.
Figure 1: Root canal preparation

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Low-speed diamond saw (Micracut, Metkon, Bursa, Turkey) was used for sectioning of root from the coronal to the apical direction, which was perpendicularly to the axis of the root. Six slices, each 2.0 mm thick, were obtained from each root, as described previously [Figure 2]. [13],[14] The coronal two slices were deemed to represent the coronal region of the root and the apical two slices were deemed to represent the apical region of the root [Figure 1].
Figure 2: Root cut into discs and push-out test

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The slice was then fixed on the metal support of a universal testing machine (Instron Canton, MA, USA) with the apical aspect facing a cylindrical plunger of 0.65-mm diameter [Figure 2]. Loading was performed at a crosshead speed of 0.1 mm/min until bond failure occurred. The push-out strength was finally calculated in MPa by dividing the load at debonding (N) by the area (mm 2 ). [15]

The failure types were determined using a stereomicroscope (Olympus SZ 6045 TR Zoom stereomicroscope, Olympus Optical Co., Tokyo, Japan) at original magnification ×40, after testing the push-out bond strengths. The type of failure was classified into the following 4 categories: (1) Adhesive failure between dentin and luting material, (2) adhesive failure between post and luting material, (3) cohesive failure of the post system (4) and mixed type, a combination of 2 of the aforementioned types.

Kolmogorov-Smirnov test was used for determination of the values distribution. The data were analyzed using three-way analysis of variance (ANOVA). Post hoc multiple comparisons were performed using the Tukey test. The failure mode data were analyzed using the Chi-square test. In all the tests, the level of significance was set at (P < 0.05) and calculations were completed using SPSS, version 11.0 (SPSS, Chicago, IL, USA).

Scanning electron microscopy analysis

Two specimens were randomly selected from each subgroup for SEM examination of the post space. Following dislocation of post, in order to qualitatively assess the cleanliness of the post space the roots were split along the axis in the linguo-buccal direction using a chisel and a hammer to expose the entire extent of the root canal. The exposed root canals were immersed in 90% alcohol, air-dried, mounted on a metallic stub, gold-sputtered (Polaron Range SC7620, Quorum Technology, Newhaven, UK) and observed under a SEM (SEM, JSM-5600, JEOL Ltd., Tokyo, Japan) at different magnifications.

  Results Top

None of the prepared specimens failed prematurely. The mean (±standard deviation) push-out bond strength for each luting strategy (and statistically significant differences), curing techniques, the root region are indicated in [Table 1].
Table 1: Push out bond strengths of UniCore and Rebilda groups

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The results showed that bond strengths of fiber posts were affected by the type of post and the resin cement (P < 0.05).

Push out bond strengths of UniCore groups were higher than Rebilda groups (P < 0.05). Push out bond strength of BisCem cement groups was lower than DuoLink and Rebilda DC groups. There were no statistically significant differences between DuoLink cement and Rebilda DC cement groups (P < 0.05) [Table 1]. There are no statistically differences between apical and coronal groups [Table 1]. In this study, Unicore (post) and Rebilda DC (cement) groups show best results.

The distribution of failure modes is reported in [Figure 3]. There were no statistical significant differences found in failure modes except coronal and apical region of Unicore post with luted BisCem resin cement [Figure 3].
Figure 3: Failure mode distribution in the experimental groups

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SEM analyses revealed that there were more opened dentinal tubules at etch and rinse adhesives. Furthermore, both of tested adhesive had higher resin tags at coronal region than apical region. [Figure 4] shows the SEM images.
Figure 4: Morphological aspects of interradicular dentin at different magnifications (a: Duo-link coronal, b: Duo-link apical, c: Rebilda coronal, d: Rebilda apical, e: Bis-Cem coronal, f: Bis-Cem apical)

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  Discussion Top

The null hypothesis, that there are both type of adhesive cements and posts do not affect bonding strength to dentin was rejected. Two main groups and three sub groups (totally six groups) tested showed noticeable adhesive properties. In this study, Unicore post and Rebilda DC cement combination showed best push-out bond strength result and Unicore posts showed better results than Rebilda posts. The push out bond strength of self-adhesive cements was lower than other two adhesion techniques' results. On the other hand, there were no statistically significant differences between etch and rinse and self-etch cement groups.

The push-out test is based on the shear bond stress at the interface between cement and dentin as well as between cement and post, which is comparable to the stresses under clinical conditions. [16],[17] Obtaining for better estimation of the dislocation resistance than the conventional shear bond test push-out test was recommended, due to parallel occurrence of the fracture to the dentine-bonding interface. [15]

There is a lot of post brand in dental marketing. In a previous laboratory study, Kurtz et al.[18] claimed that, the type of fiber post can affect push-out bond strength to a greater extent than the luting agent. In addition, Farina et al.[14] concluded that bond strength of fiber post significantly affected by the post and cement used. In the present study, Unicore showed higher bond strength than Rebilda groups, which was in agreement with previous studies. However, review of clinical follow-ups Cagidiaco et al.[6] showed that, although fiber posts have better performance than metal posts, there were no statistical differences of survival rate of fiber posts.

Previous studies showed that bond strength of fiber post can influence from root regions. [19],[20],[21] These studies were founded that bond strength at apical third was lower than coronal third of root canal and they claimed this might occurred both lack of micromechanical bonding and difficulty of cementing agent flow in apical region of post. In our study, although there were differences in bond strength between coronal and apical region, this differences was not statistically significant.

Adhesion to dentin may influenced by many factors. However, bonding into root canals might be difficult due to the handling characteristics of adhesive systems, root anatomy, etc. [22],[23] A new resin cement was introduced in 2002, which has self-adhesion mechanism (RelyX Unicem, 3M-ESPE; St. Paul MN, USA). These materials were designed with intent to bring favorable characteristics of different cement classes in order to single products. [8] Today, clinicians can use either combinations of dual-cure bonding agents and resin cement or self adhesive resin cement, depending on their chooses. This study was aimed to compare different adhesion techniques (self-adhesive, self-etch and etch and rinse) on push out bond strength of fiber post in root canal. The results of this study showed that self-etch and etch and rinse luting cements had higher bond strength than self-adhesive cement. This results can explain by resin dentin inter diffusion zone and resin tags, which can occurred strength at self-etch and etch and rinse adhesion techniques, might lead better bond strength. However, further studies needed to explain this issue.

Fracture analysis showed a large number of mixed failure, which was contain both cohesive failure in resin cement and adhesive failure both within resin cement - post and between resin cement - root canal walls. This was explained by the both absence of polymerization of cements close to dentin and due to lack of adhesion to root canals. Furthermore, because of high configuration factor (C-factor) occurred polymerization shrinkage during the curing of cements'. C-factor may have a detrimental effect on the integrity of the bond to the root canal walls. [24]

  Conclusion Top

Within the limitation of results this study, bond strength significantly affected by the post type and resin cements used for luting. The highest bond strength was obtained for Unicore post luted with Duo-link cement. The push-out bond strength in self-adhesive cement was significantly lower than self-etch and etches and rinse adhesives cement.

Fracture analysis showed there was predominance of mixed failure in all groups. Furthermore, no significant differences found in failure modes except coronal and apical region of Unicore post with luted BisCem resin cement.

  Acknowledgments Top

This study was presented as a poster presentation at 5 th biennial meeting of the European Federation of Conservative Dentistry 13-15 October 2011, Istanbul, Turkey.

  References Top

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5.Mirmohammadi H, Gerges E, Salameh Z, Wesselink PR. Effect of post diameter and cement thickness on bond strength of fiber posts. Quintessence Int 2013;44:801-10.  Back to cited text no. 5
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1]


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