Evaluation of fracture resistance of endodontically treated premolars restored by alkasite cement compared to various core build-up materials

Ankita Sharma; Subhashish Das; Manuel S Thomas; Kishore Ginjupalli

doi:10.4103/sej.sej_94_18

ORIGINAL ARTICLE

Year : 2019 | Volume : 9 | Issue : 3 | Page : 205-209

Evaluation of fracture resistance of endodontically treated premolars restored by alkasite cement compared to various core build-up materials

Ankita Sharma¹, Subhashish Das¹, Manuel S Thomas¹, Kishore Ginjupalli²
¹ Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Affiliated to Manipal Academy of Higher Education, Mangalore, Karnataka, India
² Department of Dental Materials, Manipal College of Dental Sciences, Affiliated to Manipal Academy of Higher Education, Manipal, Karnataka, India

Date of Web Publication

16-Aug-2019

Correspondence Address:
Dr. Manuel S Thomas
Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Affiliated to Manipal Academy of Higher Education, Manipal, Karnataka
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/sej.sej_94_18

Abstract

Aim: This study aimed to compare the fracture resistance of endodontically treated premolars restored by alkasite cement (Cention N), composite resin, and glass ionomer cement (GIC).
Materials and Methods: Fifty freshly extracted mandibular and maxillary premolars with typical morphology were selected and mounted on acrylic cylinders. Five groups were made with ten teeth in each group as follows: Group A: intact teeth with no restoration (control); Group B: unfilled teeth with prepared mesio-occluso-distal (MOD) cavity; Group C: teeth with MOD cavity restored with nanohybrid composite; Group D: teeth with MOD cavity restored with type IX GIC; and Group E: teeth with MOD cavity restored with Cention N. Root canal treatment was done for groups B, C, D, and E after MOD cavity and before placement of the coronal filling. The specimens were mounted on a universal testing machine, and load was applied until the specimen fractured. The values were tabulated and subjected to statistical analysis.
Results: The mean value of fracture resistance was highest in Group A (2015 N) followed by Group C (1504 N) and Group E (1319 N). Groups D and B showed the lowest reading. However, there was no statistical difference between Groups C and E.
Conclusions: Within the limitations of the study, it can be concluded that composite is the material of choice for restorations in endodontically treated tooth. Alkasite cement can be used as an alternative to composite resin due to ease of manipulation.

Keywords: Alkasite cement, composite resin, core build-up materials, endodontically treated teeth, fracture resistance

How to cite this article:
Sharma A, Das S, Thomas MS, Ginjupalli K. Evaluation of fracture resistance of endodontically treated premolars restored by alkasite cement compared to various core build-up materials. Saudi Endod J 2019;9:205-9

How to cite this URL:
Sharma A, Das S, Thomas MS, Ginjupalli K. Evaluation of fracture resistance of endodontically treated premolars restored by alkasite cement compared to various core build-up materials. Saudi Endod J [serial online] 2019 [cited 2023 Mar 27];9:205-9. Available from: https://www.saudiendodj.com/text.asp?2019/9/3/205/264651

Introduction

Endodontically treated teeth are more susceptible to fracture in comparison to healthy teeth. Access cavity preparation leading to loss of coronal structure is a critical cause for the weakening of tooth structure and consequent tooth fracture.^{[1],[2],[3],[4],[5],[6],[7]} Thus, the material used for core build-up has both structural and functional roles. Structurally, the material used for core build-up compensates for the missing tooth structure, and functionally, it bears masticatory forces as well as supporting the indirect restoration placed on the top of it.^[3] Restored teeth are susceptible to mechanical failures under large stresses and fatigue compared to healthy teeth.^[7] Contributing factors such as cavity size and design, tooth structure loss as a result of excavation, and type of restoration have been researched over the past few decades. Although there are several contributing factors to the mechanical failure of restored teeth, failures that occur within the restoration are of equal importance. Failure of the restoration generally involves subcritical fractures (i.e., chipping and indentation fractures).^[8] Sequelae of restoration fracture might involve fracture of the tooth with subsequent loss of the tooth. Tooth fracture is one of the main reasons for tooth loss along with dental caries and periodontal problems.^[9]

Indirect restorations such as full-coverage crowns serve as ideal restorations for endodontically treated teeth.^[10] Core build-up materials such as composite resin and GIC are foundation restorations for the indirect restorations. Composite resin restorations ensure esthetically acceptable direct restorations that reinforce the strength of the endodontically treated teeth.^[11] According to a study conducted by Mincik et al., GIC showed comparable mechanical strength to composite resin, but the strength of GIC deteriorates after 2 years and hence it cannot be used as a permanent core build-up material.^[12] These limitations of core build-up materials have led to the development of Cention N material (Ivoclar, Vivadent, Liechtenstein, Germany).

Cention N is a restorative material designed for complete and permanent replacement of tooth structure in posterior teeth. The alkaline fillers uniquely present in this material increase the release of hydroxide ions to neutralize the pH during acid attacks. The pH-neutralizing action enhances the cariostatic activity of this restorative cement that belongs to the material group of alkasite.^[13] Cention N also possesses a highly cross-linked polymer structure at a molecular level that contributes to its increased mechanical strength.^[14] As each of these restorative materials namely composites, GICs, and Cention N possess unique properties that in some way or the other reinforce the missing tooth structure, thisin vitro study aims to compare and analyze the fracture resistance of these materials.^[14]

The purpose of this study was to compare the fracture resistance of endodontically treated premolars restored with alkasite cement (Cention N), composite resin, and GIC.

Materials and Methods

Sample selection

A total of fifty human caries-free premolar teeth with no restorations or cracks were selected. Cracks and restorations were checked under ×4 magnification. Premolars were selected due to their anatomy and location in the arch which make them prone to masticatory forces at a higher rate. The buccolingual dimension of the teeth was noted, and it varied between 8 and 11 mm. The selected teeth were extracted due to orthodontic reasons within the last 3 months and were stored in 100% humidity throughout the study.

Ethical clearance # 17029 was obtained from the Institutional Ethical Committee, Manipal College of Dental Sciences, Mangalore (affiliated to Manipal Academy of Higher Education, Manipal, Karnataka, India). The ethical committee approval number is 17029.

Experimental groups

The teeth were then divided randomly into the following five groups:

Group A: Positive control: Intact teeth
Group B: Negative control: Unfilled teeth
Group C: Teeth restored with composite resin
Group D: Teeth restored with GIC
Group E: Teeth restored with alkasite cement.

The individual premolars were coated with putty (Aquasil Soft putty, Denstply Konstanz, Germany) below the cementoenamel junction to simulate the periodontium, and the teeth were embedded in an acrylic cube measuring 3 cm up to 2 mm below the cementoenamel junction.

Sample preparation

Mesio-occluso-distal (MOD) cavities were then prepared in all the teeth except the positive control, which was intact. The dimensions of the cavity were standardized using a Vernier caliper. The width of the cavity was kept 1/4^th of the intercuspal distance. The depth of the cavity was kept at 4 mm using a graduated probe. Following MOD cavity preparation, access cavity was prepared with straight buccal and lingual/palatal walls.

Once the cavity was prepared, deroofing of the pulp chamber was done using a diamond bur. Root canal treatment was then initiated in all the groups except the positive control, i.e., Group A. Working length was measured and all the teeth measured between 17 and 21 mm. The canals were prepared by step-back technique with hand K-files. Normal saline and 2.5% NaOCl (sodium hypochlorite) were used as irrigants. The canals were obturated with gutta-percha and AH Plus root canal sealer (Dentsply De Trey, Konstanz, Germany) using cold lateral condensation technique.

Once the obturation was done, a Tofflemire^® retainer and a matrix band were placed around the tooth to simulate the missing walls. The teeth were then restored according to the groups.

Group C: Composite resin group: The cavity was etched and bonded using Single Bond (3M™ ESPE™, St. Paul, USA), light cured for 15 s, and composite resin Z350 × T (3M ESPE, St. Paul, USA) was then placed using oblique layering technique and light cured. The restoration was polished using SOF-LEX polishing discs (3M ESPE, St. Paul, USA)
Group D: GIC group: The cavity was conditioned using polyacrylic acid. Fuji IX GIC (GC Gold Label, Tokyo Japan) was mixed according to the manufacturer's instruction and was placed in the cavity
Group E: alkasite group: Retentive features were given in the cavity. The powder liquid in the Cention N (Ivoclar, Vivadent, Liechtenstein, Germany) was dispensed in a 1:1 ratio and mixed using a plastic spatula. The restoration was placed in the cavity and after a setting time of 4 min, it was polished using SOF-LEX polishing discs (3M ESPE, St. Paul, USA).

Testing conditions

The specimens were mounted on a universal testing machine (Instron 3360 Series Universal Testing Systems, UK) and were subjected to an axial compressive load applied parallel to the long axis of the tooth and to the slopes of the cusps. A steel sphere (6 mm wide) loaded the buccal and lingual cusps of the tested specimens at a crosshead speed of 1 mm/min until fracture occurred. The load required to inflict fracture was expressed in Newton (N) as registered by the machine for all the teeth in the five groups [Figure 1].

Figure 1: Graphical presentation of various values of fracture resistance of each sample of different groups

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The data were normally and equally distributed and were analyzed using one-way analysis of variance (ANOVA) and post hoc Tukey's test.

Results

Descriptive statistics provided the mean fracture resistance values for each group with the value of standard deviation and maximal and minimal values. One-way ANOVA was used to evaluate the significance of differences between groups at a level of difference of 0.001 [Table 1].

Table 1: Comparison of fracture resistance between study groups

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Among the three experimental groups, the highest fracture resistance was seen in composite resin followed by alkasite cement and least in GIC. This difference was statistically significant with P < 0.001.

The post hoc Tukey's test revealed significant differences among the groups [Table 2]. A significant difference was found between all the experimental groups when compared to the positive control (intact teeth). There was no significant difference between GIC and negative control (unfilled teeth), but GIC was significantly different from composite and Cention N. Composite and Cention N were not significantly different from each other, but there was statistically significant difference compared to intact teeth.

Table 2: Inter-group comparison of test results

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Discussion

Endodontically treated teeth might be more susceptible to vertical fractures than are healthy teeth.^[1] Endodontic treatment reduces the core strength of the tooth due to the loss of coronal tooth structure during the preparation of access cavity and radicular structure during the preparation of the canal. Fewin vivo studies believe that endodontic treatment is the primary cause of tooth fracture.^{[15],[16],[17]}

Restoration of root canal-treated teeth depends on several factors such as the amount of remaining coronal tooth structure, tooth type, position in the dental arch, and whether the tooth should serve as an abutment for a fixed or removable partial denture.^[18] Premolars are prone to masticatory loading, more due to their position in the arch, and the anatomy of the premolars with the deep cuspal inclination makes it more susceptible to fracture.^[19] MOD cavities were prepared in the premolars to mimic the most common form of tooth loss leading to root canal therapy. Previously, similar situation has been tested in variousin vitro studies.^{[10],[20],[21],[22]} Since tooth fracture is a common occurrence in clinics, the study of this pathology remains relevant.

The three materials chosen for core build-up were composite resin, GIC, and alkasite material (Cention N), all being tooth-colored restorations and readily available in clinical setup.

Fracture resistance of sound tooth structure in this study was estimated to be 2015 N which was highest among all the groups; this result was comparable to previous studies^{[10],[23],[24]} which gave readings of 1139 N, 1514 N, and 1218 N, respectively. The negative control group that is the unfilled teeth with root canal treatment but no core build-up done showed the minimum reading 346.4 N. The variation in fracture resistance of unfilled cavities has been shown to be very vast, ranging from 221 to 545 N.^[21],[25] The wide variation in fracture resistance of unfilled teeth can be attributed to the various dimensions of the cavity designs and the testing conditions. The diameter of the metal sphere in the universal testing machine varies from 4 to 8 mm. The sphere that was used in our study was 6 mm wide, and hence the pressure at which the teeth were loaded was relatively higher. This variation can be explained by the relative variations among all the groups.

GIC has been used in the clinics as temporary or sometimes due to lack of time and increased patient inflow as permanent postendodontic restorative material.^[26] The easy manipulation and quick setting properties of GIC, along with the tooth-colored clinical appearance, lead to the increased usage of GIC in clinics as a core build-up material. GIC gave a fracture resistance of 419 N, which is almost as low as the negative control group, hence suggesting that despite the easy manipulation, GIC is not a suitable material for core buildup and should be discouraged in the clinics.^[26]

Composite resin has been set as the gold standard for core build-up material. The fracture resistance of composite resin according to our study was 1504 N, which is comparable to various previous studies showing 1407 N and 1499 N.^[24],[27] The main disadvantage of composite resin is the technique sensitivity and difficult manipulation.^[28] Cention N gave a reading of 1319 N which was comparable to composite resin. The high strength of alkasite cement Cention N is attributed to the high filler contents and the polymerization reaction. Barium aluminum silicate glass and calcium aluminum silicate glass are the fillers that render strength to the material. The flexural strength of Cention N is >110 MPa which makes it more suitable and a long-lasting material in the stress-bearing posterior region. Cention N is also a tooth-colored material and has a transparency of 11% which is higher than GIC (4%). The polymerization shrinkage of Cention N is higher than that of composite resin and GIC, as seen in a previous study by Samanta et al.^[29] and thus, plays a vital role in a core build-up material for a long-lasting restoration. All the properties of Cention N along with the ease of manipulation and handling and fracture resistance, almost like the composite resin, give a promising scope as a core build-up material.

Conclusions

Within the limitations of this study, it can be concluded that composite resin restoration is the ideal material for core buildup. However, Cention N has shown equally good results. Due to the easier manipulation of Cention N compared to composite resin, it can be used as an alternative for core build-up material in clinical practice.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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