The Effect of Different Cleaning Materials on the Bond Strength of Resin Composite to Primary Teeth Dentin Contaminated with Root Canal Sealer

DOI: https://doi.org/10.21203/rs.3.rs-2591855/v1

Abstract

Background

In the literature review, no study was found on the bond strength of the adhesive on the dentin surface contaminated with root canal sealers in root canal treatment applications of primary teeth without underlying permanent teeth germ. This study aims to shed light on clinical applications by finding the most suitable material for cleaning primary tooth dentin contaminated with permanent tooth canal sealers.

Methods

The occlusal enamel layer was removed and the dentin of the primary tooth that was contaminated with root canal sealers (AH Plus, MTA Fillapex) was cleaned with different irrigation solutions (saline, NaOCI, ethanol). Specimens were restored with a self-etch adhesive (Prime & Bond Universal Dentsply) and composite (Nova Compo C Composite Imicryl Corporation). Sticks with a thickness of approximately 1 mm were obtained from each sample, and the bond strength of the samples was measured in a microtensile test device. The interfacial morphology of the bonded space was evaluated using scanning electron microscopy.

Results

The highest bond strength was determined in the control and AH Plus saline groups. The group cleaned with ethanol showed the lowest bond strength among all groups (p < 0.01).

Conclusion

Wet cotton pellets soaked in saline provided the best bond strength for cleaning dentin tissue. It has been determined that the most effective material for removing both epoxy resin-based and calcium silicate-based root canal sealants from the access cavity is saline.

Clinical Significance:

The results presented in this study are very important in increasing the clinical success of primary teeth without underlying permanent teeth germ in pedodontics clinics during root canal treatment.

Background

It is known that the root canal filling materials used in primary teeth should be resorbed in a way that corresponds to the natural resorption of the primary tooth roots. However, when permanent tooth germs do not develop, the root canal filling materials applied to the primary teeth are not expected to be resorbed. For this reason, nonresorbable gutta-percha and root canal sealers used in permanent teeth should also be used in root canal treatment of primary teeth that do not have underlying permanent tooth germs [1]. Since it is reported that the congenital deficiency of permanent teeth is 1.52% in our society [2], the success of permanent root canal fillings to be made on primary teeth without permanent tooth germ has an important place in pedodontics clinics.

Although it is known as the golden rule to finish restoration with a stainless-steel crown in endodontically treated primary teeth [3, 4], aesthetic expectations have increased in children and adults in recent years [5]. From this point of view, composites, glass ionomers and compomers have been increasingly used in pediatric restorative dentistry [6].

In endodontic treatment, in addition to root canal filling, the restoration of the cavity is very important in clinical success regarding prevention of bacterial leakage, resistance to occlusal forces and preservation of the remaining tooth tissue [7–9]. Coronal microleakage is an important clinical problem, especially in multirooted primary teeth, as microorganisms may migrate from the pulp chamber to the furcation region [10].

Tissue tolerance, solubility in solvents, insolubility in oral fluids, bacteriostatic properties and biocompatibility in the case of leakage into periapical tissues are very important in the clinical success of root-canal sealants [11, 12]. AH Plus (Dentsply De Trey Gmbh, Konstanz, Germany), an epoxy resin-based paste, is considered the gold standard of root canal sealants due to its excellent physicochemical properties [13, 14]. MTA Fillapex (Angelus, Londrina, Brazil), a hydrophilic calcium-silicate-based canal filling paste, is highly preferable due to its ease of use in the clinic aswell as its biocompatible and bioactive properties [15, 16].

If endodontically treated teeth have a sufficient amount of coronal structure, they can be restored with composite resin by use of a direct technique due to their capacity to bond to dentin [8, 17]. The bonding of composite resins to dentin compared to enamel may vary due to organic components, fluid-filled tubules and differences in composition [18]. Furthermore, it is known that there are hardness differences between the dentin of permanent teeth and primary teeth due to the thickness and mineralization degrees [19].

In addition to all this information, in the literature review, it was concluded that the bond strength of the permanent filling material applied after the crown dentin contaminated with root canal sealer was wiped with cotton pellets soaked in irrigation solutions in primary teeth without permanent successor teeth was not studied. Based on this information, in the present study, we aimed to examine the effect of the resin-dentin bond strength created by the adhesive after cleaning the dentin of the primary teeth contaminated with AH Plus and MTA Fillapex root canal paste, which is used in the permanent root canal treatment of primary teeth without a permanent successor teeth germ, after cleaning with various materials. The null hypothesis of this study is that the cleaning solutions tested do not affect the dentin bond strength of the primary teeth of the adhesive system used.

Materials And Method

Study design and setting

This is an in vitro study that aimed to compare different irrigation solutions used to clean primary tooth dentin contaminated with permanent canal filling pastes during endodontic treatment applied to primary teeth. Information about the institution where this research was conducted was removed for blind peer review.

Sample size calculation

As a result of the analysis made in the GPower software, the power of the test was determined to be 85.44%.

Source of sample

Thirty-six caries-free primary second molars extracted due to excessive mobility as a result of root resorption were used. The sample source included patients who were referred to the Department of Pediatric Dentistry of the Faculty of Dentistry for dental treatment.

Inclusion and exclusion criteria

Caries-free primary second molar teeth from healthy individuals who applied to the clinic due to chewing complaints as a result of excessive mobility were included in the study. Caries and filled primary teeth were not included in the study.

Preparation of dentine surface and contamination with sealer

The enamel layer in the occlusal area of the primary teeth, which was stored in a 0.1% thymol solution at 4°C until use, was removed in a low-speed rotating water-cooled Isomet device (Isomet Low Speed Saw; Buehler Ltd, Lake Bluff, IL, USA) in Selcuk University Faculty of Dentistry Research Laboratory. The materials used in this study are shown in Table 1.

Table 1

Materials used in this study

Materials

Composition

Application mode

Root canal sealers

MTA Fillapex

Salicylate resin, diluting resin, natural resin, bismuth trioxide, nanoparticulated silica, MTA, pigments

It was applied to the dentine with help of dry cotton pellet

AH Plus

A patı: Epoxy resin

B patı: amine derivatives

It was applied to the dentine with help of dry cotton pellet

Irrigations

NaOCI

2.5% in intensity

Applied with the help of cotton pellet

Ethanol

95% in intensity

Applied with the help of cotton pellet

Bonding

Prime & Bond Universal; Dentsply, Germany

Diamine Bis Acrylic; Water; Propanol; Dihydrogen Phosphate Methacrylate; Penta; Bis Acrylic Propylamine; Camphorquinone; HexaFluorPhosphate; Benzonitrile Dimethylamino; Hydroquinone.

Bond was applied and waited for 20 seconds, the air was dried with water spray for 5 seconds and light was applied for 10 seconds

Composite

Nova Compo C

Dimetakrilat, ba-glass, yiterbiyum triflorur, prepolimerized filler, catalyst, stabilizer, ULS monomer

The resin composite was applied and light was applied for 20 seconds

The teeth, which were then washed and dried with air‒water spray, were randomly divided into three main groups to canal sealers:

Group 1: Control group. The root canal sealer and irrigation solution were not applied.

Group 2: AH Plus paste (AH Plus; Dentsply, Konstanz, Germany) was applied to the dentin surface with a dry cotton pellet for five minutes.

Group 3: MTA Fillapex paste (MTA-FILLAPEX (MTA Fillapex; Angelus, Londrina, Brazil) was applied to the dentin surface with a dry cotton pellet for five minutes.

The root canal paste was applied once to cover the dentin surface after contacting the dry cotton pellet.

The main groups (2 and 3) were further divided into four subgroups depending on the irrigation solution:

Subgroups 2a: Contaminated dentin was cleaned with cotton pellets soaked in saline.

Subgroups 2b: Contaminated dentin was cleaned with cotton pellets soaked in 2.5% NaOCl.

Subgroups 2c: Contaminated dentin was cleaned with cotton pellets soaked in saline after 24 hours. Samples were kept at 37°C for 24 hours.

Subgroups 2d: Contaminated dentin was cleaned with cotton pellets soaked in 95% ethanol.

Subgroups 3a: Contaminated dentin was cleaned with cotton pellets soaked in saline.

Subgroups 3b: Contaminated dentin was cleaned with cotton pellets soaked in 2.5% NaOCl.

Subgroups 3c: Contaminated dentin was cleaned with cotton pellets soaked in saline after 24 hours. Samples were kept at 37°C for 24 hours.

Subgroups 3d: Contaminated dentin was cleaned with cotton pellets soaked in 95% ethanol.

** All samples were cleared for one minute.

*** The manufacturer stated that the setting time for MTA Fillapex is more than two hours. For AH Plus, this is approximately eight hours. From this point of view, we set a waiting period of 24 hours in Subgroups 2c and 3c. When the recommended waiting times are applied in line with the recommendations of the manufacturer, a 24-hour waiting period is deemed appropriate to prevent patients from being kept in the clinic for a long time. Then, the restoration phase was initiated.

Bonding and restoration procedure

After removing the sealer, the teeth were restored with self-etch adhesive (Prime & Bond Universal Dentsply) and composite (Nova Compo C Composite Imicryl Corporation, Konya, Turkey) following the manufacturer's recommendations. In delayed restoration, the bonding and composite of the specimens were restored after they were kept in a humid environment at 37°C for 24 hours. Composite material with 2 mm thickness was placed using the incremental technique on the bonded dentin surface and cured with an LED curing unit (VALO Cordless, Ultradent, US) according to the manufacturer’s instructions.

Preparation of samples and micro tensile testing

After the composite was applied in the study, the samples were kept in a humid environment at 37°C for 24 hours. Horizontal sections of approximately 1 mm2 thickness were taken from the restored dental crowns mesiodistally and buccolingually under a water-cooled Isomet saw (Isomet Low Speed ​​Saw; Buehler Ltd, Lake Bluff, IL, USA). Sticks that were broken or attached to the enamel area during sectioning were removed from the study group and a total of 30 sticks were obtained in each group (270 sticks in total). The area of ​​the beams was calculated by measuring with an electronic caliper (Starret 727-6/150; Starret, San Paulo, Brazil). The bonded sticks were attached to a loading jig with cyanoacrylate resin glue (Akfix; Akfix Trade Ltd. Co., Istanbul, Turkey). Subjected to tensile force in a universal testing machine (Microtensile Tester; Bisco Inc., Schaumburg, IL, USA) at a tensile force with a speed of 1 mm/min. A microtensile load was applied until specimen failure. The bond strength was recorded in Newtons (N) and calculated as megapascals (MPa).

One-way ANOVA was used to determine whether there was a difference between the groups, and the Tukey test, which is one of the multiple comparison tests, was used to compare the group averages.

The failure modes for all specimens were evaluated at 100x magnification with scanning electron microscopy (SEM: Zeiss EVO LS10; Oberkochen, Germany). Failures were classified as adhesive failure, cohesive failure (between the resin and dentin), or mixed failure (in the dentin and adhesive material or composite resin).

Results

The microtensile bond strength values, standard deviations and failure types are summarized in Table 2.

As a result of the analysis of variance, the difference between the mean of the control group (without sealer) and AH Plus wet cotton was not statistically significant (p > 0.01). However, a significant difference was found between all other groups (p < 0.01) (Table 2). The control group and the group treated with AH Plus saline provided the highest micro tensile bond strength. Compared to the control group, the lowest bond strength was detected in the group cleaned with ethanol in both sealers.

In the present study, failure-type analysis with SEM adhesive and mixed fractures were detected in the samples (Fig. 1, Table 2).

Discussion

In the literature review, there are very few studies on root canal sealer and contaminated primary tooth bond strength. Elbay and Tosun found that composite materials bonded to pulp chamber dentin in primary teeth had higher strength than compomers and resin-modified glass ionomers in their study on bond strength of restorative systems in the primary tooth pulp chamber of endodontic sealers [20]. In addition, the composite was applied to primary teeth in their study. The present study has shown that the materials used in cleaning dentin contaminated with canal filling paste can affect the bond strength of restorative systems. Furthermore, Ghouchani et al. found that cleaning the tooth cavity using Metapex with 96% ethanol significantly increased the composite-dentin bond in their study that evaluated the effect of root canal filling materials and their solvents on the shear strength of primary tooth dentin and resin composite [21].

Wattanawongpitak et al. found that the root canal sealer reduced the micro tensile bond strength of a dual-curing resin composite with etch and rinse and self-etching adhesive systems to intrapulpal dentin. Another study determined that ethanol was effective in reducing the negative effects of root canal filling materials on the adhesion of primary tooth dentin [22]. In the present study, bond strength in teeth contaminated with both canal filling paste and cleaned with ethanol was found to be significantly lower than in the other groups (control, saline, NaOCl and delayed) (p < 0.01).

Some studies on NaOCl, which is frequently used in endodontic treatment, showed that NaOCl reduced the bond strength between adhesive materials and dentin and explained this condition as causing changes in the collagen fibrils of dentin [17, 23, 24]. In the present study, the results of the samples treated with AH Plus-NaOCl and MTA Fillapex-NaOCl were higher than those of the groups cleaned with ethanol but significantly lower than those of the control and saline groups (p < 0.01). On the other hand, a significant difference was found between the sample groups treated with MTA Fillapex NaOCl and AH Plus NaOCl (p < 0.01).

In light of the above information, since the negative effects of chemical solvents on the adhesion of the adhesive to the dentin are known, Kürklü et al. used water to clean the contaminated dentin with bioceramic-based sealant and found that the canal sealant in the access cavity was eliminated better as the amount of water increased [25]. The AH Plus filling paste used in the present study is a hydrophobic paste compared to other endodontic canal filling pastes [26]. In their study conducted in 2014, Borges et al. examined the physicochemical properties of MTA Fillapex and AH Plus and found that MTA Fillapex had a more homogeneous appearance with higher resolution [27]. MTA FillApex dissociates into calcium hydroxide and subsequently into calcium and hydroxyl ions when it contacts water, which increases the pH of the solution (Hungaro et al 2003). It has been reported that high pH prevents the destruction of mineralized tissue by neutralizing the acids secreted by osteoclasts [14]. However, in our study, the bond strength values of AH Plus treated with wet cotton were higher than those of MTA FillApex (p < 0.01).

On the other hand, in the examination of dentin contaminated with canal sealer, flat surface dentin was obtained from the teeth and bond strength was examined [24, 29, 30]. In the present study, flat surface dentin was used to examine the bond strength.

In the present in vitro study, the bond strength of primary tooth dentin contaminated with canal filling sealer varies according to different cleaning materials. More studies are needed to support these findings. Further studies on primary teeth with different canal filling materials and different cleaning protocols can bring new perspectives to pedodontics clinics.

Conclusions

Various materials are used to remove root canal sealants that affect the bond strength of the adhesive system and contaminate access cavity dentin. The present study has shown that the most effective material for removing both epoxy resin-based and calcium silicate-based root canal sealants from the access cavity is saline. Based on this result, saline can play an important role in increasing clinical success, as it is one of the materials that is cheap, safe and easily available and has the least patient irritation. The results presented in the current study are very important in increasing the clinical success of primary teeth without permanent teeth in pedodontics clinics during root canal treatment.

Declarations

Ethics approval and consent to participate

Approval numbered 05-2021/01 was obtained from the Ethics Committee of Karamanoğlu Mehmetbey University Faculty of Medicine for the study. At the same time, all experimental protocols were specified in the ethical approval form and approval was obtained. Informed consent was obtained from all volunteers and/or legal guardian(s).

Consent for publication

Not applicable.

Availability of data and materials

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

Competing interests

The author declared that there are no possible conflicts of interest.

Funding
 The author paid for the materials and analysis fees used in the study.

Authors contributions

All support for the current article (e.g., funding, provision of study materials, medical writing, manuscript processing fees, etc.) has been covered by the author.

Acknowledgements

The author verifies that all methods have been performed in accordance with relevant guidelines and regulations.

Author information

Department of Pediatric Dentistry, Faculty of Ahmet Keleşoğlu Dentistry, Karamanoğlu Mehmetbey University, Yunus Emre Campus, Karaman/TURKIYE ORCID: 0000-0003-1276-9709

Asu Çakır

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