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Abstract Aim: The aim of this study was to assess and compare the coronal microleakage of e-Temp (DiaDent, Korea), intermediate restorative material (IRM) (Dentsply, Sirona), and Systemp Inlay (Ivoclar Vivadent, Germany) temporary restorative materials used to seal the class I cavity preparations. Materials and Methods: In this in vitro experimental study, three temporary restorative materials were assessed for microleakage. A standardized class I access cavities (2 mm × 4 mm) were prepared in 30 freshly extracted intact human premolar teeth. Teeth were then divided randomly into three groups consisting of 10 samples each. Teeth were restored with e-Temp (n = 10), IRM (n = 10), and Systemp Inlay (n = 10), temporary restorations, and subjected to thermocycling 5000 times in a cold bath followed by a temperature of 55°C with a dwell time of 30 seconds. Teeth were painted with two layers of nail polish except for 1 mm around the restoration margin, soaked in 1% methylene blue dye solution (pH 7.4), and kept for 24 h. Sticky wax was used to seal the apical foramina. All the teeth were sectioned mesiodistally, and the specimens were examined for the amount of dye penetration (microleakage) through the restoration using Digital Microscope under 50× magnification. Data were analyzed using descriptive statistics, Mann–Whitney U, and Kruskal–Wallis tests. Results: e-Temp showed 1 (10%) specimen with dye penetration up to 1 mm (Score 1). The specimens restored with IRM showed a 1 (10%) and 9 (90%) of scores for 1 and 3 dye penetration. However, 2 (20%) teeth restored with Systemp Inlay showed a dye penetration up to 3 mm or more (Score 3). A comparison of mean microleakage values of e-Temp (0.03 ± 0.10), IRM (2.69 ± 0.77), and Systemp Inlay (0.78 ± 1.64) showed a statistically significant difference (P < 0.001). IRM specimens showed significantly higher microleakage values than e-Temp and Systemp Inlay specimens (P < 0.05). Conclusion: All the temporary restorative materials tested in this in vitro experiment showed a certain extent of microleakage. The temporary restorative material e-Temp showed the least microleakage values followed by Systemp Inlay and IRM.
Keywords: Dye penetration, e-Temp, IRM, microleakage, Systemp inlay, temporary restoration
Introduction 
Microleakage in dental restorative materials is a significant concern in clinical dentistry. It is characterized by the clinically undetectable movement of bacteria, fluids, molecules, or ions between the cavity wall and the restorative material.[1],[2],[3] Use of temporary restorative materials between appointments is one of the considerations for deciding root canal therapy quality. These materials temporarily seal the tooth and prohibit the escape of drugs from the pulp chamber into the oral cavity between root canal appointments.[4]
Many approaches have been utilized to test coronal microleakage, including Micro-CT,[5] dye,[6],[7] bacteria,[8] and fluid infiltration.[9] However, these tests repeatedly concluded that all the temporary restorative materials showed some extent of leakage followed by a risk of canal contamination.[10]
A variety of intermediate restorative materials (IRMs) have been studied for use as an intracoronal seal to avoid microleakage, including Cavit, IRM, glass ionomer cement (GIC), and mineral trioxide aggregate (MTA).[8],[11],[12] The IRM and Cavit are the most frequently studied temporary restorative materials.[13] However, the increasing popularity of tooth-colored restoration coupled with patients’ demand for better esthetics has led to the introduction of Systemp Inlay (Ivoclar Vivadent, Schaan, Liechtenstein), a light polymerized polyester dimethacrylate-based resin composite designed for temporary restoration of class I and class II cavities. Systemp Inlay is placed into the preparation and polymerized by curing light, and it can be easily removed with an explorer.[14],[15]
Lately, resin-based materials are considered an alternative to traditional temporary restorative materials to enhance the sealing properties. Systemp Inlay (Ivoclar Vivadent, Schaan, Liechtenstein) and e-Temp (DiaDent, Korea) are currently used in dental practice. However, these materials are not tested extensively for their microleakage concerns against the traditional temporary restorative materials. Hence the present study aimed to assess and compare the coronal microleakage of e-Temp (DiaDent, Korea), IRM (Dentsply, Sirona), and Systemp Inlay (Ivoclar Vivadent, Germany) temporary restorative materials in sealing the class I cavity preparations. The hypothesis tested in this study would be no difference in the coronal microleakage values of the temporary filling materials e-Temp, IRM, and Systemp Inlay when used to seal the class I cavity preparations.
Materials and Methods This in vitro study was carried out at the Restorative Dentistry Department, College of Dentistry, Riyadh Elm University, from October 2020 to April 2021. Ethical approval for the study was obtained from the research and innovation center of Riyadh Elm University, Riyadh, Saudi Arabia (IRB # FPGRP/2020/518/302/299). This study used the dye method to test three types (e-Temp, IRM, and Systemp Inlay) of temporary restorative materials for their microleakage [Table 1].
Sample cleaning, storage, and preparation
Thirty freshly extracted human premolars were used in this study based on the inclusion criteria (teeth should be sound, free of caries, have no cracks or fractures, have no history of orthodontic or restorative treatment, and are free from any internal or external defects and abnormalities). On the contrary, teeth with visible multi-surface carious decay, fractures, and preexisting restorations were excluded.
The selected teeth were cleaned with an ultrasonic scaler to remove all soft tissues and debris. Teeth were then disinfected with 5.25% Sodium hypochlorite solution for 24 h and kept in distilled water at 37°C.[16] A single researcher prepared the standard class I cavities having a mesiodistal width of 2 mm and depth of 4 mm using a high-speed air turbine under water coolant with a number 4 round diamond bur for early entry and a diamond fissure bur to extend the cavity to the required occlusal outline. The bur replacement was carried out after every eight cavity preparations. All the measurements of the cavity preparations were standardized using a calibrated periodontal probe.
The teeth were divided randomly into three groups (group 1 restored with e-Temp [n = 10], group 2 restored with IRM [n = 10], and group 3 restored with light cure temporary filling material Systemp Inlay [(n = 10]), and color-coded with green, black and red. All materials were mixed and handled according to the manufacturer’s recommendation. The temporary materials were incrementally introduced into the cavity from the bottom up with a plastic instrument. Every effort was made to ensure that the restorative materials were carefully pressed against the cavity walls. All three groups were exposed to the thermocycling machine (SD Mechatronik, Huber model) for the temperature aging process. Specimens were put in a thermocycler for 5000 cycles in a cold bath followed by a temperature of 55°C with a dwell time of 30 seconds, equivalent to 2 years of simulation.
Dye penetration measurement
In preparation for leakage assessment, the specimens were painted with two layers of nail polish except for 1 mm around the restoration margin, soaked in 1% methylene blue dye solution (pH 7.4), and kept for 24 h. Sticky wax was used to seal the apical foramina. All the specimens were embedded in clear self-curing orthodontic Resin for sectioning mesiodistally using a low-speed Isomet cutting machine (low-speed saw, BUEHLER).
All the sectioned specimens were examined for the amount of dye penetration (microleakage) through the restoration using Digital Microscope (HiRoX, model KH 7700) under 50× magnification [Figure 1]. The dye penetration was measured using 4-point criteria: score 0––no dye penetration, score 1––dye penetrates up to 1 mm, score 2––dye penetrates up to 2 mm, and score 3––dye penetrates up to 3 mm or more.[17]
Statistical analysis
Descriptive statistics of frequency distribution, percentages, and mean microleakage (dye penetration) values were calculated for all three-group of specimens restored with temporary restorations. Microleakage was compared among cement groups (e-Temp, IRM, and Systemp Inlay) by applying Kruskal–Wallis H. Multiple comparisons between groups (e-Temp vs. IRM, e- Temp vs. Systemp Inlay, IRM vs. Systemp Inlay) was performed by applying the Mann–Whitney U test. The statistical analysis was conducted using Statistical Package for Social Sciences (SPSS version 25, Armonk, NY: USA). A value of P < 0.05 was considered significant for statistical tests.
Results The study results revealed that nine (90%) specimens restored with e-Temp did not show any dye penetration, whereas only one (10%) specimen showed a dye penetration up to 1 mm (score 1). On the contrary, specimens restored with IRM showed 1 (10%) and 9 (90%) scores 1 and 3 dye penetration. Similarly, teeth restored with Systemp Inlay showed no dye penetration in 8(80%) of the specimen, and 2 (20%) specimens showed a dye penetration up to 3 mm or more (score 3). More than half 17 (52.7%) of the teeth restored with different temporary cement types did not show any dye penetration (Score 0). However, 2 (6.7%) specimens showed a dye penetration of up to 1 mm, and 11 (36.7%) showed a dye penetration of up to 3 mm or more (Score 3). The specimens restored with the IRM cement (76.9%) showed the highest percentage of microleakage, followed by Systemp Inlay (15.4%) and e-Temp (7.7%), as shown in [Table 2].
The mean ± standard deviation values of microleakage in specimens restored with e-Temp (0.03 ± 0.10), IRM (2.69 ± 0.77), and Systemp Inlay (0.78 ± 1.64) are displayed in [Table 3]. A comparison of mean microleakage values among different groups showed a statistically significant difference (KW-H 15.942, df = 2, df = 2, and P < 0.001).
Further analysis by the Mann–Whitney U test showed a statistically significant difference in mean microleakage values between e-Temp and IRM (Z = –3.963, P < 0.001). Similarly, comparing mean microleakage values between e-Temp and Systemp Inlay groups did not show any statistically significant difference (Z = –.730, P = 0.466). However, mean microleakage values showed a significant difference between IRM and Systemp Inlay (Z = –2.343, P = 0.019) [Table 4].
Discussion The study findings indicate that all the tested temporary restorative materials exhibited microleakage. However, the extent of this microleakage varied in different materials. Teeth restored with e-Temp showed the least microleakage, followed by Systemp Inlay. In contrast, all the teeth restored with IRM showed various degrees of microleakage. The mean microleakage values of specimens restored with IRM were significantly higher than the teeth restored with e-Temp and Systemp Inlay. However, the microleakage values reported between e-Temp, and Systemp Inlay did not differ significantly. IRM’s highest microleakage is attributed to its material composition and capacity to achieve effective tooth sealing. Besides, the significant dimensional variations arising from thermocycling, the higher P/L ratio of 6 g/ml, the mixing phase, and the resulting lack of homogeneity and the volumetric contraction could be the factors that contributed to higher microleakage in an IRM-restored specimen.[18] Conversely, McInerney and Zillich reported that the IRM had the least bulk penetration than Tempit and Cavit.[19] However, Patel et al.[20] reported a significant difference in marginal leakage between IRM and Tempit restorative material.
The least microleakage of e-Temp is attributed to its setting property while in contact with moisture and undergoing hygroscopic expansion, thus retaining a tight seal at the material and the tooth interface. This finding is supported by studies in which tight to moderate seals were reported with conventional self-cure temporary restorative material due to hygroscopic expansion.[21],[22],[23] Different studies have reported inconsistent findings concerning readymade temporary filling materials such as Cavit and hand-mixed IRM to prevent coronal microleakage. Cavit had the best sealing ability and the least dye penetration and acted as a barrier to leakage than IRM.[24],[25],[26] The relatively low microleakage observed in Systemp Inlay could be attributed to the lower modulus of elasticity that remains elastic even after polymerization.[15] It has been reported that no material could block microleakage completely. Ideally, no such material is entirely adaptive and adhesive to a tooth structure that exhibits no microleakage.[27] Based on the study’s findings, the proposed null hypothesis has been rejected as we found a significant difference between the microleakage of IRM compared with e-Temp and Systemp Inlay.
This in vitro experimental study compared the degree of marginal microleakage among e-Temp, IRM, and Systemp Inlay temporary restorative materials after filling class I cavities of human premolar teeth. Class I cavities were chosen because of their structure or “C” factor, which refers to the ratio between the number of bounded and unbounded surfaces.[28]
Previous studies have reported that a minimum of 3.5–4 mm of restorative material is necessary to prevent microleakage. The likely reason is that the temporary restorative materials need adequate retention to prevent dislodgement between appointments. Therefore, a 4-mm thick temporary restorative material is desirable.[29],[30] In line with this, extracted intact premolars were used, and a thickness of at least 4 mm of restorative material was placed within the prepared cavity.
In this study, 1% methylene blue dye was used to verify microleakage since it quickly penetrates the tooth’s water compartment, does not interfere with hard tissues, and is easily detectable under visible light with a molecular size smaller than the bacteria. Moreover, dye penetration methodology is easy, quick, low-cost, and not needing complicated laboratory equipment.[31],[32],[33] However, to prevent the leakage of the dye through the tooth structure, teeth samples were painted with nail varnish.
It has been reported that placing experimental temporary restorative materials in the prepared cavity can affect the marginal microleakage of the material.[34] Hence, all the temporary restorative materials were manipulated following the manufacturer’s recommendations to overcome this issue. A single researcher restored all the prepared cavities with temporary materials to obtain a marginal seal. The present research used the thermal cycling technique to replicate intraoral conditions. The temperature variations up to 55°C, corresponding to the extreme temperature endured in the oral cavity, were carried out.
The e-Temp is a recently introduced hydraulic temporary restorative material that has not been extensively tested for its microleakage. IRM is a hand-mixed material utilized for a temporary restoration, whereas Systemp Inlay was a light cure temporary filling material considered in this study. Due to the lack of reported microleakage studies on e-Temp, the present study findings are compared with readymade temporary sealing materials such as Cavit.
The results collected from the dye penetration test have criticized investigators who contend that this procedure has broad standard deviations and is not reproducible.[35] This in vitro study has some limitations; it does not duplicate the oral condition and the availability of saliva. Moreover, the findings are unique to the experimental conditions utilized in this study. In clinical situations, microleakage can be affected by chewing forces that may differ depending on factors such as sex, the tooth’s position, age, and bruxism. Therefore, the occlusal load was not included in this study due to the abovementioned variations.
There is a controversy surrounding the use of the thermocycling procedure. It has been shown that the marginal sealing ability of temporary filling materials can be adversely affected by temperature fluctuations.[36] In contrast, others showed that thermal cycling did not affect microleakage.[1] Thermocycling was undertaken in this study to include the effect of temperature on microleakage. Given these limitations, more studies are required to determine microleakage based on quantitative microbiological tests and quantitative analyses.
Conclusion It can be concluded that all the temporary restorative materials tested in this in vitro experiment showed a certain extent of microleakage. The temporary restorative material e- Temp showed the least microleakage, followed by Systemp Inlay and IRM. Study findings indicate that e-Temp and Systemp Inlay be preferred over IRM as a temporary filling material for effective coronal microleakage control for a brief period. Therefore, permanent restorations should be placed at the earliest.
Acknowledgement
We would like to thank the Research and Innovation Center of Riyadh Elm University for supporting this project.
Financial support and sponsorship
Not applicable.
Conflicts of interest
There are no conflicts of interest.
Author’s contributions
SSA: Concepts, design, the definition of intellectual content, literature search, data acquisition, manuscript preparation, manuscript editing, and manuscript review. RB: Concepts, design, the definition of intellectual content, literature search, manuscript editing, and manuscript review. SB: the definition of intellectual content, literature search, manuscript editing, and manuscript review.
Ethical policy and institutional review board statement
The study proposal was registered in the research and innovation center of Riyadh Elm University (FPGRP/2020/518/302/299).
Patient declaration of consent
Not applicable.
Data availability statement
Data available on request from the authors.
References 
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