Effect of fiber-reinforced composites on the fracture strength values under different thickness of CAD/CAM systems

Abstract

Background

To evaluate the effect of fiber-reinforced composites on fracture-strength (FS) values of nanoceramic CAD/CAM restoration materials with different thicknesses.

Methods

One-hundred extracted, caries-free human maxillary premolars were divided into two main groups based on the thickness of the nanoceramic CAD/CAM restorative material (2 mm and 3 mm). Within each main group, five subgroups were formed: one control, one non-fiber (G-ænial Universal Flo), and three fiber-reinforced experimental subgroups (Ribbond, EverStick NET, and EverX Flow). Standardized MOD cavities were prepared in all experimental groups, extending 2 mm below the cementoenamel junction and 3 mm wide on the proximal walls. All restorations were fabricated using Cerasmart blocks and cemented with G-CEM Link Force dual-cure resin cement. FS testing was performed, and the data were statistically analysed (p < 0.05).

Results

Ribbond significantly increased fracture resistance compared to the control group (p = 0.047), while other fiber materials showed no significant difference (p > 0.05). An increase in restorative material thickness enhanced fracture resistance in fiber-reinforced groups (p < 0.001). In the control group, variation in the remaining tooth structure height did not significantly affect fracture resistance (p = 0.078). There was also no significant difference in the interaction between the fiber-reinforced composite type and restoration thickness (p>0.05).

Conclusion

Although the thickness of the restorative material may influence FS, the use of fiber-reinforced composites does not appear to significantly affect the fracture resistance of nanoceramic CAD/CAM restorations.

Background

The long-term survival of root canal-treated teeth is important for patients and clinicians. The survival of root canal-treated teeth is closely related to the success of coronal restoration as well as successful root canal treatment [1]. The structural integrity and biomechanical behavior of root canal-treated teeth are influenced by factors such as dental caries, fractures, cracks, endodontic procedures, and restorative protocols, making them more prone to fragility [2]. Even during conservative endodontic cavity access and root canal instrumentation, stiffness drops by 5% [3]. If the mesial, occlusal, and distal marginal ridges (MOD cavities) are included in the endodontic cavity, stiffness will be reduced by 63% [4].

Current adhesive systems allow preservation of tooth structure and restoration of severely damaged, endodontically treated teeth without extensive tissue loss [5, 6]. Adhesive restorations preserve tooth structure more than full crowns and generate a biomechanical construction similar to intact teeth [7, 8]. However, deep subgingival carious lesions or defective restorations may be very challenging during restorative treatment. The gingival margins of large MOD cavities located in the subgingival area, make it difficult to take impressions and apply adhesive procedures [9]. Dietschi, and Sprefico described the technique of ‘deep margin elevation (DME), which is elevation of the gingival ridges with composite resin increments supragingivally [10]. The DME technique is applied using immediate dentine sealing (IDS) protocols; besides elevating margins to supragingival positions, exposed dentinal areas are sealed with composite resins that may be either paste or flowable, undercuts are covered, creating an ideal cavity design for indirect restorations [11, 12].

Clinicians choose dental composites with different structural properties when preparing teeth for indirect restorations. However, conventional dental composites that contain filler particles do not replicate dentine structure and its physical properties [13]. Hybrid dental composites exhibit lower fracture strength (FS) than dentine [14]. To achieve restorations with high fracture resilience and the ability to resist crack propagation, fiber reinforced dental composites are used as ideal dentine-like replacement materials [15, 16]. Fibers inhibit crack initiation and propagation, and are able to stretch, bridging cracks and preventing cracks from opening and spreading further. These characteristics in fiber-reinforced composites are based on the types of fiber ingredients, orientation distributions, aspect ratios, volumes, and the relation between fiber fillers and resin matrix [16–18].

Studies comparing the effects of different fiber-reinforced composite materials on the fracture resistance of severely damaged, endodontically treated teeth restored using the deep margin elevation (DME) technique are quite limited. There is a lack of published comparative data on this topic in the current literature. Rocca et al. [19] reported the importance of cavity reinforcement and fiber configuration to enhance the load-bearing capacity of such restorations. Therefore, the present study aimed to contribute to the knowledge base by providing standardized comparative data on the use of fiber-reinforced materials. Specifically, the effects on the FS of severely compromised teeth of three different fiber types (Ribbond, EverX Flow, and EverStick NET) and two different restoration thicknesses were investigated.

The null hypotheses tested in this study are:

1. Fiber-reinforced material type does not affect fracture strength of restorations.

2. Thicker restorations do not show higher fracture strength values.

Materials and methods

This study was begun after receiving permission from the Ethics Committee of Kocaeli University (Decision Number: KU GOKAEK-2022/05.11). Prior to data collection, a power analysis was conducted using G*Power software (version 3.1.9.7, Düsseldorf, Germany), which indicated that a minimum of 10 specimens per group (total N = 100) was required, based on an effect size of 0.50, 90% power, and an alpha level of 0.05. Table 1 presents the materials used in this study along with their compositions.

Table 1.

Brand, content, and manufacturer information of the materials used in the study

Materials	Type	Contents*	Lot Numbers
Cerasmart (GC, Tokyo, JAPAN)	Nanoceramic CAD/CAM Material	71% SiO2 and Bariumglass 29% Resin (Bis-MEPP, UDMA, DMA)	2,202,041
G-CEM Link Force (GC, Tokyo, JAPAN)	Dual Cure Resin Cement	Paste A: Pigments, initiator, DMA, UDMA, Bis-GMA Paste B: BHT, dibenzoyl peroxide, Bis-EMA, Initiator, DMA, UDMA, MEPP-B	2,202,091
G-Aenial Universal Flo (GC, Tokyo, JAPAN)	Flowable Composite	Resin (UDMA, bis-MEPP and TEGDMA) 31% wt; fillers (silicon dioxide[16 nm], strontium glass [200 nm]) 69 wt % and traces of photoinitiator	2,202,181
G-Premio Bond (GC, Tokyo, JAPAN)	Universal Bonding Agent	10-MDP, 4-META, 10- methacryoyloxydecyl dihydrogen thiophosphate, methacrylate acid ester, distilled water, acetone, photo-initiators, silica fine powder	2,202,141
GC Modeling Liquid (GC, Tokyo, JAPAN)	Modeling Liquid	Uretan Dimetakrilat (UDMA) 2-hydroxy-1,3 dimetacrylatopropan 2-hydroxyethyl metacrilate	2,309,081
EverX Flow (GC, Tokyo, JAPAN)	Short Fiber Reinforced Flowable Composite	Bis-EMA, TEGDMA, UDMA, Short glass fibers (200–300 μm & Ø7 µm), Barium glass 70% wt	2,311,141
Ribbond (Ribbond Inc., Seattle, USA)	Polyethylene Fiber	Ultra-High Molecular Weight Polyethylene Fiber	N.A.
Ever Stick Net (GC Europe, Leuven, BELGIUM))	Bidirectional Glass Fiber	E-glass Fiber, silanized bis-GMA and PMMA	2,206,201

N.A. Not Available (not indicated on the packaging)

Collection of natural teeth

In this study, 100 human upper premolar teeth extracted for prosthetic, orthodontic and periodontal reasons at the Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Kocaeli University were used. Care was taken to ensure that there were no caries, cracks or restorations in the teeth. Soft tissue residues, bone particles and calculus were removed with a periodontal curette; discolorations were cleaned with pumice and water. The selected teeth were disinfected in a 2.5% sodium hypochlorite solution for the first 24 h and subsequently stored in distilled water, which was refreshed weekly throughout the study period. The experimental procedures were initiated within one week after the last extraction to ensure consistency in storage conditions.

Preparation of samples

One-hundred human upper premolar teeth were embedded in acrylic resin molds so that the resin level was located approximately 3 mm apical to the cementoenamel junction (CEJ). The pulp of all teeth except Groups A1 and B1, the control groups, was removed with K and H-type hand files (Dentsply Maillefer, Ballaigues, Switzerland). During restoration procedures, the root canal orifices were closed using Teflon tape.

Standardized cavities were prepared with a buccolingual width of 3 mm and a depth of 2 mm. The gingival floor of the cavity was positioned 2 mm apical to the CEJ, and the cavity was extended to include the pulp chamber (MOD), resulting in a flat surface configuration. The occlusal surface of the cavity, which served as the bonding interface for the restorative material, terminated at 1 mm coronal to the CEJ as a butt joint margin. The depth of the pulp chamber was adjusted to approximately 3 mm from the pulp floor to the internal cavomargin level.

All cavity preparations were performed by the same experienced clinician using a high-speed handpiece, equipped with a diamond bur. To ensure standardization among specimens, cavity dimensions were verified using a periodontal probe, as illustrated in Fig. 1.

Fig. 1.

Cavity design of the samples in the study groups (proximal view)

Following cavity preparation, the specimens were randomly divided into ten experimental groups (n = 10 per group) based on the type of restoration material and application technique (Fig. 2). The experimental workflow is outlined in Fig. 3 to provide a visual summary of the methodological steps.

Fig. 2.

Schematic view of the study groups

Fig. 3.

Workflow diagram summarizing the experimental procedures

Before fiber-reinforced restorations were applied, all samples underwent a standardized adhesive protocol. Enamel margins were etched with 37.5% orthophosphoric acid (Ultra-Etch, Ultradent, South Jordan, UT, USA) for 20 s, rinsed, and gently air-dried. A universal bonding agent (G-Premio Bond, GC Corp., Tokyo, Japan) was applied to all internal cavity surfaces and light-polymerized in accordance with the manufacturer’s instructions using a light-emitting diode (LED) curing device (Elipar Deep Cure-S, 3 M Oral Care, St. Paul, MN, USA) at a light intensity of 1470 mW/cm² for 20 s.

To recreate proximal walls, a 0.5 mm-thick layer of flowable composite (G-Aenial Universal Flo A2) was applied to both the mesial and distal surfaces using a matrix system and light-cured. Following this, Teflon tape-covered canal orifices were sealed using the same composite material.

Subsequently, group-specific restorative procedures were performed, as follows:

Group A1 (Control – 2 mm Cerasmart) To simulate specimens restored with 2-mm thick Cerasmart (GC Corp., Tokyo, Japan), a flat surface was prepared 3 mm above the CEJ, the occlusal enamel was removed, and the samples were directly subjected to fracture testing.

Group B1 (Control – 3 mm Cerasmart) To simulate specimens restored with 3-mm thick Cerasmart, a flat surface was prepared 4 mm above the CEJ, the occlusal enamel was removed, and the samples were directly subjected to fracture testing.

Groups A2 and B2 (G-Aenial universal Flo A2) These groups were restored without fiber-reinforced materials. All cavities were filled using G-Aenial Universal Flo A2 (GC Corp., Tokyo, Japan) flowable composite resin. Polymerization was performed using an LED curing device.

Groups A3 and B3 (Ribbond) The Ribbond (2 mm width; Ribbond Co., Seattle, USA) was pre-wetted with GC Modeling Liquid, adapted to the cavity walls in a circular motion along with G-Aenial Universal Flo, and polymerized using an LED device. The remaining cavity space was then filled with G-Aenial Universal Flo and light-cured.

Groups A4 and B4 (EverStick NET) Cavity walls were pre-wetted with flowable composite. EverStick NET (2 mm width; GC Europe, Leuven, Belgium) was adapted to the cavity walls in a circular motion and light-cured. The rest of the cavity was restored with G-Aenial Universal Flo and polymerized.

Groups A5 and B5 (EverX Flow) EverX Flow (GC Corp., Tokyo, Japan) was applied as a 2-mm base layer and light-cured. Subsequently, a 1-mm layer of G-Aenial Universal Flo was applied over it and polymerized.

Polymerization of composite or fiber-reinforced materials in all groups was performed using the same LED curing device (Elipar Deep Cure-S, 3 M Oral Care, St. Paul, MN, USA) in standard mode at an intensity of 1470 mW/cm² for 20 s. After fiber application and final polymerization, all cavities were finished as flat surfaces and prepared for the cementation of the prefabricated nanoceramic CAD/CAM blocks (Cerasmart A3 HT, GC Corp., Tokyo, Japan), which were adjusted according to group assignment.

Production and cementation of restoration materials

Cerasmart blocks were sectioned into 2-mm and 3-mm-thick slices using a precision cutting device (Micracut 151, Metkon, Turkey) to simulate different restoration heights. The slices were then adjusted with diamond burs to fit the tooth specimens restored with fiber-reinforced composites.

Before cementation, Cerasmart specimens were sandblasted using aluminum-oxide (mean particle size 50 μm [20]), using a sandblaster (Basic Eco, Renfert GmbH, 78247, Hilzingen, Germany) at a pressure of 1.5 bar for 10 s from a distance of approximately 10 cm. Then, the Cerasmart specimens and the tooth surfaces were etched using 37.5% phosphoric acid (Ultra-etch, Ultradent, South Jordan, UT, USA) for 20 s, washed with water, and dried [21].

G-Multi PRIMER (GC Corp., Tokyo, Japan) was applied to the internal surface of the restoration and gently air-dried. G-Premio BOND (GC Corp., Tokyo, Japan) was applied to the cavity surfaces of the tooth for 20 s and then gently air-dried.

Dual-cure resin cement (G-CEM Link Force, GC Corp., Tokyo, Japan) was applied according to the manufacturer’s recommendations. The restorations were initially seated with manual pressure, followed by the use of an ultrasonic device (Cementation Tip, EMS, Nyon, Switzerland) [19]. After initial light exposure for 5 s to facilitate removal of excess cement, final polymerization was performed for 20 s per surface using the LED device.

All specimens were then stored in distilled water at room temperature until further testing. An example of the completed restoration is shown in Fig. 4.

Fig. 4.

Presentation of a sample after cementation protocol

Fracture testing

Continuous increasing force was applied vertically to the center of the occlusal surface of the restorations using a 5-mm diameter metal sphere and a universal static fracture test device (Atlas-LH-EMK 20 KN) at a head speed of 1 mm/min until the first fracture occurred. The FS test set-up is shown in Fig. 5. FS values for each sample were recorded in Newtons (N). After the FS test, the specimens were visually examined under 6× magnification, and fracture types were classified. Fractures occurring in the tooth, restoration, or deep margin elevation were classified as repairable, whereas fractures extending below the deep margin elevation and requiring tooth extraction because of tooth or root fracture were classified as non-repairable, with representative examples presented in Figs. 6 and 7 [21].

Fig. 5.

An example of performing a fracture test with an experimental sample

Fig. 6.

Non-repairable fracture

Fig. 7.

Repairable fracture

Statistical analysis

All statistical analyses were performed using the SPSS, version 20.0 (IBM Corp., Armonk, NY, USA). The Shapiro-Wilk test was used to assess the normality assumption. Continuous variables are presented as mean ± standard deviation. Two-way analysis of variance (ANOVA) was conducted to investigate the main and interaction effects of the fiber-reinforced material types and the different thicknesses of restorative materials on FS values. All pairwise comparisons were performed using Bonferroni adjustment. A p < 0.05 was considered statistically significant.

Results

In this study, the effects of different fiber-reinforced composite types on the fracture resistance of restorations were evaluated. A statistically significant increase in fracture resistance was observed only in the groups reinforced with Ribbond compared to the control group (p = 0.047). No statistically significant differences were found between the groups with other fiber materials, either when compared to the control or between the sub-groups (p > 0.05).

Increased restorative material thickness led to a significant enhancement in FS in samples using Universal Flo (p = 0.002), Ribbond (p < 0.001), EverstickNet (p = 0.002), and EverX Flow (p = 0.010) groups. However, in the control group, variation in the height of the remaining tooth structure did not result in a statistically significant difference in fracture resistance (p = 0.078). These findings suggest that the effect of thickness on fracture resistance may be more pronounced in fiber-reinforced restorations. There was also no difference in the interaction between the fiber-reinforced composite type and restoration thickness (p>0.05). The results of the two-way ANOVA are presented in Table 2.

Table 2.

Two-Way ANOVA results for the effects of composite type, restoration thickness, and their interaction

	p
Material type	0.082
Thickness	< 0.001
Interaction (Material type × Thickness)	0.374

The mean FS values obtained from the mechanical tests are presented in Table 3. The failure modes of the specimens, classified as repairable or non-repairable, are shown in Table 4. A graphical comparison of the failure loads across different fiber types and Cerasmart thicknesses is illustrated in Fig. 8.

Table 3.

The mean values found on fracture strength testing grouped by CAD/CAM slice thickness (Group a = 2 mm and group B = 3 mm) and subgrouped by material used

	Group-A (Mean ± Standart Deviation)		Group-B (Mean ± Standart Deviation)
		2-mm CAD/CAM Slice		3-mm CAD/CAM Slice
Control Group	A1	1628,50 ± 458,86 Aa	B1	1926,60 ± 306,82 Aa
Universal Flo	A2	1643,40 ± 270,44 Aa	B2	2171,00 ± 398,71 Ab
Ribbond	A3	1722,20 ± 260,15 Aa	B3	2496,50 ± 456,58 Ab
Ever Stick NET	A4	1617,70 ± 284,73 Aa	B4	2143,40 ± 505,49 Ab
EverX Flow	A5	1750,20 ± 370,99 Aa	B5	2189,90 ± 335,05 Ab

Capital letters are used for vertical comparisons, while lowercase letters indicate lateral comparisons. The same capital letters within a column indicate no significant difference (p > 0.05). Similarly, identical lowercase letters in a row indicate no significant difference (p > 0.05), whereas different lowercase letters denote a statistically significant difference (p < 0.05)

There was no significant difference between groups A1, A2, A3, A4, and A5 or between B1, B2, B3, B4, and B5. Fiber application did not affect the FS values of the restorations (p = 0.082)

Table 4.

Fracture mode analysis of all groups

	Repairable	Unrepairable		Repairable	Unrepairable
A1	0	10	B1	0	10
A2	3	7	B2	1	9
A3	6	4	B3	2	8
A4	3	7	B4	4	6
A5	5	5	B5	6	4

Fig. 8.

The effect of different fiber types and Cerasmart thickness on the fracture strength of restorations

Discussion

The aim of this study was to analyze the effects of different fiber materials on the FS of CAD/CAM restorations and to guide clinicians in their use of specific, more effective combinations. Ultra-high-molecular-weight, polyethylene fiber Ribbond, bidirectional strengthening fiber Ever Stick NET, and short glass-fiber-reinforced flowable composite EverX Flow were applied to the samples and then tested. G-ænial Universal Flo was used as the base composite, and a universal adhesive was applied following the manufacturers’ instructions. The materials were selected because they are commonly used in clinical settings and all were compatible with nanoceramic CAD/CAM blocks, such as Cerasmart.

The results of the present study showed that fiber application did not affect the FS values ​​of the restorations. No statistically significant difference was found between the experimental groups to which G-Aenial Universal Flo, Ribbond, Ever Stick NET and EverX Flow was applied. The first hypothesis, “Fiber-reinforced material type does not affect the fracture strength of restorations.” was accepted.

Advances in fiber-reinforced composite technology have increased the use of conventional composites in teeth with excessive material loss [22]. It has been reported that the use of Ribbond in the restoration of teeth with excessive material loss with direct composites increased the strength of the direct composite restorations [23–25]. It has also been demonstrated that the use of continuous glass fibers in large composite restorations that will receive high stress has a positive effect on the strength of the restorations [25, 26]. Short fiber-reinforced materials have also been used in combination with conventional composites to improve the fracture toughness of direct composite restorations [13, 15, 25]. However, in the present study, no difference in fracture resistance was observed between the tested fiber-reinforced materials under vertical loading. This suggests that, within the parameters of this study, the type of fiber-reinforced material may not influence the FS.

Another aim of the present study was to determine whether a relationship could be established between fiber reinforcement and restorative material thickness. Previous research reported that application of fiber-reinforced composite did not change the FS values ​​and fracture modes of thick restorations under perpendicular occlusal forces [19]. To investigate this, 2-mm and 3-mm thick restoration groups (Control, G-Aenial Universal Flo, Ever Stick NET and EverX Flow) were compared pairwise. It was found that the FS values ​​of samples with 3 mm Cerasmart restoration thickness were higher. Thus, the second null hypothesis, “Thicker restorations do not show higher fracture strength values.” was rejected.

To the best of the authors’ knowledge, two studies [19, 27] are relatively comparable to the present study, as they simulated teeth with extensive material loss, restored the entire occlusal surface using endocrowns or overlays, and used static FS testing. Rocca et al.. applied Ever Stick NET and short fiber-reinforced composites EverX Posterior to the pulp chamber of molar teeth and restored resin nanoceramic CAD/CAM material, which was LAVA Ultimate. A static fracture toughness test was performed and it was reported that there was no significant difference in terms of FS values between teeth with and without fiber-reinforced composite applications. These authors found that the stress-relieving properties of Everstick NET were better than EverX Posterior after examination performed with stereoscopic electron microscopy, even though the loaded samples were of the type that required tension [19].

Fildisi and Eliguzeloglu examined the effect of applying Ribbond on the structure of root canal-treated molar teeth, again by measuring the FS values of Cerasmart overlay/onlay restorations. These authors placed two pieces of Ribbond polyethylene fiber in a cross position on the floor of the pulp chamber of root canal-treated teeth, which was then covered with flowable composite. It was reported that there was no significant difference in FS values between the restoration groups with and without Ribbond. However, Ribbond application affected the fracture modes, tending to result in repairable fractures [27].

Garoushi et al.. investigated the effect of short fiber-reinforced composite (EverX Flow) on FS values of direct and indirect (nanoceramic Cerasmart and e-max CAD) restorations. EverX Flow was applied in a 2-mm thickness to each tooth structure. Then, samples were restored using direct composite restoration, nanoceramic, and E-max onlay restorations (3-mm restorative material thickness). In this study it was reported that there was no significant difference between the FS values of the restoration groups [28].

Contrary to the results of the present study, Monaco et al.. reported that the application of continuous glass fibers increased the FS of indirect composite overlay restorations. The authors fabricated the overlays using a microhybrid composite material. This difference in findings may be attributed to differences in the type of restorative material, the number and configuration of fiber layers, or the anatomical placement design of the reinforcement. Furthermore, the authors reported that increasing the amount of fiber further improved FS [29]. Similarly, it has been reported that the FS of direct composite onlay restorations was enhanced by an increased amount of EverX Flow [28].

The combination of fibers and CAD/CAM restorative materials is a topic of current interest [22, 29, 30]. One recent study has shown that endocrown restorations produced with an experimental CAD/CAM restorative material, incorporating short fibers into its structure, have higher FS values ​​than other CAD/CAM materials, including the nanoceramic CAD/CAM block, Cerasmart [31].

The findings of the present study may provide useful insights for clinical decision-making. First, the absence of a statistically significant difference in FS between the fiber-reinforced materials suggests that routine inclusion of fibers beneath CAD/CAM nanoceramic restorations may not be essential in cases where adequate restorative material thickness can be achieved. Instead, ensuring an adequate restorative material thickness that can withstand occlusal forces appears to have a more direct influence on fracture resistance. This is particularly relevant when planning endocrown or onlay restorations for endodontically treated teeth. In clinical cases with limited vertical space or reduced coronal structure, fiber reinforcement may still be considered as a supplementary strategy to potentially modulate fracture behavior. However, clinicians should prioritize achieving appropriate material thickness, when possible, as it offers a more predictable improvement in mechanical performance.

CAD/CAM restorative materials developed with advances in technology demonstrate superior physical and mechanical properties when compared to traditional materials [32]. However, comprehensive laboratory studies involving larger sample sizes are needed to understand the effects of applying fiber-reinforced composite resins with nanoceramic CAD/CAM restorative materials. Furthermore, in vitro studies cannot fully replicate intraoral conditions, which remains a notable limitation. Therefore, findings should ideally be supported by well-designed clinical trials. Nonetheless, the use of thermal cycling and dynamic loading protocols may help approximate the clinical environment. Future studies should evaluate how different fiber placement strategies, fiber types, and artificial aging protocols affect the long-term performance of these restorations. Such insights will help clinicians to make evidence-based decisions regarding the integration of fiber-reinforced materials with CAD/CAM restorations, particularly in cases involving extensive tooth structure loss.

Conclusions

The type of fiber net or using fiber-reinforced composite resins under restorations did not change the FS values of CAD/CAM restorations. In clinical applications, designing restorations with increased thickness within clinically applicable limits may be a suitable approach to enhance fracture resistance. The results of the present study suggest that if the restorative materials have advanced physical and mechanical properties, the effect of the combination of different materials used in the substructure is minimal.

Abbreviations

ANOVA

Analysis of variance

CAD/CAM

Computer aided design/ computer aided manufacturing

CEJ

Cementoenamel junctıon

DME

Deep margin elevation

IDS

Immediate dentine sealing

LED

Light emitting diode

MOD

Mesio-occlusal-distal

N

Newton

FS

Fracture strength

Authors’ contributions

CAT, NT participated in the design of the study. CAT, SNB participated in the generation of data for the study. CAT, SNB, VT participated in data collection for the study. CAT, SNB participated in analyzing the data. CAT wrote most of the original draft of the article. SNB, NT participated in writing the manuscript.CAT, SNB, VT, GNC, NT had access to all raw data for the study. CAT, SNB, VT, GNC, NT reviewed the relevant raw data on which the conclusions and implications of this study are based. CAT, SNB, VT, GNC, NT approved the final version of this article. CAT, VT, GNC ensured that all individuals who met the journal’s authorship criteria were included as authors of this article.

Funding

Supported by grant no. 2022–3018 from the University of Kocaeli Scientific Research Projects Coordination Unit.

Data availability

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

Declarations

Ethics approval and consent to participate

This study was approved by the Ethics Committee of Kocaeli University (Decision Number: KU GOKAEK-2022/05.11). The study was conducted in accordance with the Declaration of Helsinki. Only extracted human teeth were used, which were obtained with informed consent from patients under routine clinical procedures and anonymized prior to use. No personal data were collected, and no living human participants were involved in the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.