|Year : 2019 | Volume
| Issue : 3 | Page : 174-180
Effect of calcium hydroxide intracanal medicament on the push-out bond strength of RelyX Unicem self-adhesive cement
Nik Rozainah Nik Abdul Ghani1, Rosdayana Ibrahim2, Norhayati Luddin1, Sam'an Malik Masudi3, Mohmed Isaqali Karobari1
1 Conservative Unit, School of Dental Sciences, Health Campus, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
2 Restorative Unit, Ayer Keroh Dental Clinic, Melaka, Malaysia
3 Restorative Department, Faculty of Dentistry, Lincoln University College, Petaling Jaya, Selangor Darul Ehsan, Malaysia
|Date of Web Publication||16-Aug-2019|
Dr. Nik Rozainah Nik Abdul Ghani
Restorative Department, School of Dental Sciences, Health Campus, Universiti Sains Malaysia, Kubang Kerian 16150, Kelantan
Source of Support: None, Conflict of Interest: None
Aim: This study was aimed to determine the use of calcium hydroxide (Ca(OH)2) intracanal medicament effect on the push-out bond strength of RelyX Unicem self-adhesive cement onto the root canal wall.
Materials and Methods: A total of 50 extracted human maxillary permanent incisor teeth were randomly divided into control and experimental groups (n = 25 for each group). The control group was prepared for routine root canal treatment followed by post space preparation. RelyX Unicem self-adhesive cement is used for the cementation of fiber post in the root canal, as in experimental group, Ca(OH)2intracanal dressing was placed into the root canal for a week, followed by root canal filling, post space preparation, and cementation of fiber post using RelyX Unicem cementation. Each sample was divided into coronal, middle, and apical root sites. They were horizontally sliced and examined using scanning electron microscope (SEM). Three slices from each of the three sites were subjected to push-out test for bond strength measurement. Independent t-test was used to compare the push-out bond strength of RelyX Unicem on the root canal wall. One-way analysis of variance and pairwise comparison test were used for the statistical analysis. The significant level was set as P < 0.05.
Results: The significant differences in bond strength were demonstrated between the different sites of the root, where the coronal and apical with the P value 0.031 and 0.020, respectively. However, the middle third of the root showed no statistically significant difference, where P = 0.072.
Conclusions: Intermediate Ca(OH)2dressing has an effect on the bond strength of RelyX Unicem self-adhesive resin cementation on the root canal wall.
Keywords: Fiber post, intracanal medicaments, push-out bond strength, scanning electron microscope, self-adhesive cement
|How to cite this article:|
Abdul Ghani NR, Ibrahim R, Luddin N, Masudi SM, Karobari MI. Effect of calcium hydroxide intracanal medicament on the push-out bond strength of RelyX Unicem self-adhesive cement. Saudi Endod J 2019;9:174-80
|How to cite this URL:|
Abdul Ghani NR, Ibrahim R, Luddin N, Masudi SM, Karobari MI. Effect of calcium hydroxide intracanal medicament on the push-out bond strength of RelyX Unicem self-adhesive cement. Saudi Endod J [serial online] 2019 [cited 2020 Jul 2];9:174-80. Available from: http://www.saudiendodj.com/text.asp?2019/9/3/174/264644
| Introduction|| |
Root canal-treated tooth may always result in a significant loss of tooth structure. The tooth may require post placement in the canal as for retention of the final restoration. In the early 1990s, fiber-reinforced polymer post was introduced as an alternative to custom-made cast alloy post and core. The self-adhesive resin cement has been used for the fiber post cementation onto the root canal dentinal wall. This self-adhesive resin cements may as well improve retention, reduce microleakage, and increase resistance to tooth fracture. It also simplified and shortened the clinical time on the dental chair for the patients., However, some of the endodontic materials such as nonsetting calcium hydroxide (Ca(OH)2) intracanal medicament has been shown to influence the quality of bond strength between the post, adhesive cement, and dentinal wall. Several studies reported that the bond strength of fiber post is affected by Ca(OH)2 due to the process of degradation or demineralization of root canal dentinal wall., The low bonding strength of resin cement to root dentin was possibly due to the remnants of Ca(OH)2 in the entrance of dentinal tubules which line on the surface of the dentinal wall. These remnants were believed to interfere the hybrid layer formation of self-adhesive resin cement system. However, there was a study to investigate the effect of triple antibiotic paste (TAP), double antibiotic paste (DAP), and Ca(OH)2. The result showed that TAP decreased the bond strength of self-adhesive resin cement to root dentin compared with the control group, while Ca(OH)2 and DAP did not affect the bond strength. On the other hand, a similar study was conducted and concluded that Ca(OH)2 and TAP increased the bond strength of the RelyX cement to dentinal wall. As such, the aim of thisin vitro study was to evaluate the effect of intermediate Ca(OH)2 intracanal medicament on the push-out bond strength of RelyX Unicem self-adhesive cement and to determine the interaction between the cement and fiber post and onto the dentinal root wall under SEM magnification.
| Materials and Methods|| |
Sample selection and preparation
A total of 50 extracted permanent human maxillary incisor teeth were selected using the following inclusion criteria: none carious, no restoration, no fracture, no previous endodontically treatment, and no posts or crowns. Teeth with minimum length of 12 mm and coronal root diameter 2–5 mm were selected. The study was approved by the Human Research Ethics Committee at Universiti Sains Malaysia, USM/JEPeM/278.5 (3.6). Each tooth was placed in a container filled with 5.25% sodium hypochlorite (NaOCl) (Hospital Universiti Sains Malaysia) for 2 h for the surface disinfection and then rinsed in distilled water. The root diameter and canal morphology were determined radiographically from digital radiography by analyzing film in different plane “sagittal, coronal, and axial views” using the software (Gendex Oralic AC, Helsinki, Finland).
Root canal instrumentation and preparation
Endodontic access cavity was started with endo access high-speed bur no. 75A and 75B (Reco-Dent, Sweden). The working length was established by exploring the canal of each tooth using a size 10 K-file (Dentsply Maillefer, USA), until the apical foramen was reached, and the tip of the file was visible. The confirmative working length was measured by reducing 1 mm from the visible size 10 K-file. The root canal preparation was carried out with the crown-down procedures. The ProTaper hand files (Dentsply Maillefer, USA) were used up to finishing file F3 30/09 taper to the confirmative working length. A lubricant, Glyde File Prep (Dentsply Maillefer, USA), was used throughout the cleaning and shaping procedure, and the canal was irrigated between instrumentations with 2 mL of 2.5% NaOCl (Hospital Universiti Sains Malaysia).
Final irrigation was carried out using 17% ethylenediaminetetraacetic acid (EDTA) (Meta Biomed, South Korea) for 3 min followed by a flush with 10-mL distilled water. The root canals were dried with absorbent paper point (Dentsply Maillefer, USA) and randomly divided into two groups (n = 25). For the control group (Group 1), the root canals were filled and obturated under lateral compaction technique with the gutta-percha points (F3) (Dentsply Maillefer, USA) and AH Plus sealer (Dentsply Maillefer, USA), as for the experimental group (Group 2), nonsetting Ca(OH)2(Pulpdent, USA) was applied in the canal using a size 40 K-file (Dentsply Maillefer, USA). All the coronal cavity access of the samples was sealed with a small cotton pellet and temporary filling material (Cavit, 3M ESPE, USA). All samples of both control and experimental groups were submerged in normal saline in storage box at 37°C to mimic the oral environment for 1 week. Ca(OH)2 intracanal medicament was removed from the root canal of experimental group after a week. The canals were flushed with 10-mL 17% EDTA, followed by 10-mL 2.5% NaOCl and a final irrigation with 5-mL distilled water. Subsequently, root canal was filled with the same technique as for the control group. The samples from both control and experimental groups were coronally cut 1 mm below the cementoenamel junction using hard-tissue cutter under water cooling, leaving the obturated root canal with length between 12 and 15 mm.
Post space preparation and cementation
The root canal filling of both control and experimental groups were removed with heated endodontic instrument plugger, leaving 4 mm remaining at the apical root end. The removal of gutta-percha point was confirmed radiographically. The root canals of each sample were then prepared for post placement using low-speed drill of the same diameter and shape according to the prefabricated glass–fiber posts provided by the manufacturer (Cytec Blanco, Hahnenkratt, Germany). Following the post space preparation, the canals were rinsed with 2.5% NaOCl. A final flushing of the canal was accomplished with distilled water, and the canals were dried with paper points (Dentsply Maillefer, USA). The self-adhesive resin cement, RelyX™ Unicem Aplicap™ (3M ESPE, Germany), was manipulated according to the manufacturer's instruction, where the activated cement capsule was placed in amalgamator and the mixture process was taken for 15 s. The elongation plastic tip (3M ESPE, Germany) was attached to the capsule to deliver the cement into the canal. The posts were seated to full depth using finger pressure, and excess luting agent was removed with a small brush. Light polymerization was carried out for 40 s under Cabled Light Enmity Diode, Light Cure Unit (Dentsply Maillefer, USA). The post placement was confirmed radiographically [Figure 1]. All specimens were stored in saline solution at 37°C for a week before undergone push-out test.
|Figure 1: Root sample showing fiber post placement and 4-mm remaining gutta-percha at apical third|
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Preparation of roots for push-out bond strength testing
The root was cut horizontally into four slices with a double-face diamond disc at low speed under water cooling. The first coronal slice was not included to avoid the influence of excess RelyX Unicem self-adhesive cement. Therefore, three sections of 2 ± 0.5 mm were obtained per roots representing the cross sections of the coronal, middle, and apical regions of the post space [Figure 2]. The actual thickness of each slice was measured with a digital caliper (Mitaka, Japan), with an accuracy of 0.01 mm. The tooth slice was attached to a horizontal platform with a cyanoacrylate adhesive. The push-out test was performed by applying load with maximum power of 10 MPa, at 0.5 mm/min on a universal testing machine (Instron, Model 8824, USA). Each slice was loaded with two different sizes of punch pin: 1-mm diameter for coronal and middle thirds and with a 0.8-mm diameter for apical third. The load was applied to the apical aspect of the root slice and in an apical–coronal direction to push the post toward the larger part of the root slice, thus avoiding the limitation of the material movement. The punch pin was positioned to contact the post only without stressing the surrounding root canal walls. The bond strength was determined using a computer software program Merlin software (Instron Merlin Software, Massachusetts, USA).
|Figure 2: Illustration of the root sectioning, the first coronal slice was not included to avoid the influence of excess RelyX Unicem self-adhesive cement, and the other three sections represent the coronal, middle, and apical regions|
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Scanning electron microscope (SEM) preparation
One sample slice from each different site was randomly selected to evaluate the interaction interface between dentin, self-adhesive cement, and fiber post. The surface was cleaned with dampened cotton pellets, rinsed, and then air-dried. Specimens were mounted on aluminum stubs, and as for standardization, the lower/bottom surface of each root region faced the stub, and the front/upper surface of each root region was selected for scanning procedures. Each of the specimens was sputter coated with gold powder in SC005 Leica Sputter Machine (Leica Microsystems GmbH, Vienna, Austria) for work traces under the SEM. The gold sputter was used to produce clearer images. The specimens were mounted onto a specimen stub and viewed using high-resolution SEM (FEI Quanta 450, Oregon, USA). Photomicrographs were taken at ×100 and ×500 magnifications to provide and evaluate the type of interaction interface on each sample surface's region.
All data were entered and analyzed using the Statistical Package for the Social Sciences (SPSS) version 22.0 software (Chicago, IL, USA). The Kolmogorov–Smirnov test was used for the normality of the push-out bond strength data distribution and Levene's test for homogeneity of variances. Since the data of the bond strength measurement were normally distributed, they were analyzed using parametric test. The bond strength between roots with and without Ca(OH)2 intracanal medicament was compared using independent t-test. The significant difference in bond strength among the two groups and on the different sites of the root was assessed by one-way analysis of variance (ANOVA) test, followed by the Scheffe post hoc test for multiple comparisons. ANOVA and pairwise comparison tests were conducted to compare the mean of the push-out bond strength among the three different sites of the root for the control and experimental groups. The level of significance of the tests was set at P < 0.05.
| Results|| |
For both experimental and control groups, there was a significant difference in bond strength of RelyX Unicem self-adhesive cement to the dentinal wall at the different sites of the root canal. The push-out bond strength of RelyX Unicem self-adhesive cement on the control group was significantly higher than experimental group with P = 0.00004 [Table 1]. The highest bond strength was at the coronal site of the root canal for both control and experimental groups as represented in [Table 2] and [Table 3].
|Table 1: Mean (standard deviation) of the push-out bond strength value (MPa) for the control and experimental group|
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|Table 2: Mean (standard deviation) of push-out bond strength values (MPa) according to the site of the root for control group|
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|Table 3: Mean (standard deviation) of the push-out bond strength values (MPa) according to the site of the root canal for experimental group|
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The result showed that the coronal site and apical site of the control group had higher bond strength values than the experimental group with P = 0.031 and 0.020, respectively. However, even though the bond strength for the middle site of the root for the control group was higher than the experimental group, there was no statistically significant difference with P = 0.072 [Table 4].
|Table 4: Mean (standard deviation) of the push-out bond strength values (MPa) of RelyX self-adhesive cement for fiber post cementation with and without calcium hydroxide intracanal medicament according to the different site of the root canal|
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Scanning electron microscope observation
The SEM evaluation for both control and experimental groups revealed that gap was observed between RelyX Unicem self-adhesive cement and the root canal wall in all different sites of the root canal. The coronal site is represented in [Figure 3]a and [Figure 3]b, the middle site in [Figure 4]a and [Figure 4]b, and the apical site in [Figure 5]a and [Figure 5]b.
|Figure 3: (a) SEM of the coronal site of the root from the control group (×500). (b) SEM of the coronal site of the root from the experimental group (×500)|
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|Figure 4: (a) SEM of the middle site of the root from the control group (×500). (b) SEM of the middle site of the root from the experimental group (×500)|
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|Figure 5: (a) SEM of the apical site of the root from the control group (×500). (b) SEM of the apical site of the root from the experimental group (×500)|
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| Discussion|| |
In this study, RelyX Unicem self-adhesive cement was used because it exhibits moisture tolerance during bonding procedure. It is difficult to control the moisture deep inside root canal because of poor visibility and accessibility. Furthermore, the narrow canal holds water by surface tension, making it difficult to displace water with bonding agents. RelyX Unicem self-adhesive cement simplified the clinical steps by eliminating the pretreatment procedures on root canal dentinal wall and allowed luting fiber post using a standardized approach that reduces technique sensitivity despite limited access to root canal space. There was a chemical interaction which initiated by acid monomers in the cement and dissolved the Ca2+ ions in the tooth structure. The chemical interaction between the cement and hydroxyapatite was very effective and important for bond strength in the dentinal root area. A recent study conducted showed that all forms of Ca(OH)2 intracanal medicaments reduce the microhardness of the root canal dentin. Viscous and oily form of Ca(OH)2 has more deteriorating effect on microstructure of dentin compared to aqueous form. Good adaptation in most of the root canal sites between RelyX self-adhesive and dentinal wall may be related to chemical interaction with the hydroxyapatite within the dentin. The polymerization shrinkage of the adhesive cement may greater than the adhesion of the cement to dentinal wall and thus creates a gap that affects the adhesive interface., The gap may as well be due to inadequate pressure during luting procedures. RelyX Unicem self-adhesive cement should be applied using some pressure to ensure close adaptation to the root canal dentinal wall. The cement was hardly present in the apical site of the root canal of both control and experimental groups. The thin RelyX cement in the apical third of the root might be associated with the limitation of the material to flow into the area.
According to this present study, Ca(OH)2 intracanal medicament has significantly affected the push-out bond strength of RelyX Unicem self-adhesive cement on the root canal wall. The result agreed with the previous study that found Ca(OH)2 intracanal medicament affect the push-out bond strength of luting resin to the root canal dentinal wall., The presence of Ca(OH)2 remnants interferes with the chemical interaction between root canal sealer and dentin structure, which acts as an important factor to achieve the good bonding and adaptation between resin cement and root canal dentinal wall. A significant difference in the push-out bond strength between different sites of the root with a reduction value from coronal to apical site in the control group was found in this study. The result was agreed with another similar study which found higher bond strength in the coronal and middle site and lower bond strength in the apical site of the root for the group without Ca(OH)2 intracanal medicament.,,, The push-out bond strength value was reduced from coronal to apical third although there was no significant difference in bond strength value between coronal and middle thirds and middle and apical thirds. Other factors which may contribute to the reduction in bond strength of the RelyX Unicem self-adhesive cement could be due related to limitation of cement flow to the inner site of the root canal. Moreover, the coronal site of the root canal is the most accessible area to the root canal preparation and instrumentation compared to the middle and apical of the canal space, thus making it easier to apply the self-adhesive cement. The strongest adhesion was observed in the most coronal section of the root compared to the middle and apical sites; this was related with the high number of dentinal tubules on the dentinal wall which contribute a larger amount of self-adhesive cement flow to the tubules and provide good adaptation and bonding. In addition, the reduction in bond strength of the apical site could be explained by the difficulty of the curing light to reach the area. Furthermore, the apical third of the root was the most difficult area to trace and to remove remaining Ca(OH)2 intracanal medicament. Further research is recommended to take into consideration the age of the patient, to avoid the influence of age in mechanical properties of dentin and consistency of hydroxyapatite. Moreover, comparison between the varieties of resin cement and the effect of different technique in Ca(OH)2 removal and different types of irrigation solution may as well to be considered.
| Conclusions|| |
Under the condition and limitation of this study, the Ca(OH)2 intracanal medicament gave a significant reduction in the push-out bond strength of RelyX Unicem self-adhesive resin cement used for fiber post cementation.
We would like to thank Universiti Sains Malaysia Short Term Grant (304/PPSG/61313106) and Mr. Mohd Yusof Soon Abdullah and his team from Research Laboratory Unit School of Dental Sciences, University Sains Malaysia, for their helpful in providing all the facilities. We also thank Associate Professor Dr. Wan Mohd Amir Wan Ahmad for his advice in statistical analysis.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4]