Original Article

Effects of Intracanal Medicaments on the Measurement Accuracy of Four Apex Locators: An In Vitro Study


  • Hamza Cudal
  • Tuğrul Aslan
  • Bertan Kesim

Received Date: 18.07.2022 Accepted Date: 25.10.2022 Meandros Med Dent J 2023;24(3):215-219


This study aimed to examine the effect of various intracanal medicaments on the precision of four electronic apex locators (EALs).

Materials and Methods:

This study comprised 160 maxillary central incisors. After root canal preparation, a 25-K file was carefully introduced into the root canal until it was perceptible through the apex, and 0.5 mm was subtracted from this amount to determine the actual length. Samples were divided into four groups: calcium hydroxide, double antibiotic paste, triple antibiotic paste, and the control groups. Intracanal medications were removed with EDTA ten days later, and electronic measurements were performed. Chi-square (χ2) test was used to assess the precision of EALs within the margins of ±0.5 and ±1 mm (α=0.05).


The accuracies of the four EALs did not vary significantly for different intracanal drugs within the bounds of ±0.5 and ±1 mm (χ2 tests, p>0.05).


The EALs used in this study obtained reliable readings of working length in the context of varying intracanal medications.

Keywords: Calcium hydroxide, antibiotics, root canal medicaments, electronic apex locator


Achieving the proper working length which is an important stage of the procedure (1), is vital for a successful root canal treatment (RCT). Since there are concerns that many factors may affect this measurement, the influence of numerous clinical factors on the precision of electronic apex locators (EALs), such as coronal enlargement (2), diameter of the apical foramen (3), irrigation solutions (4), and intracanal medicaments (5,6), have been investigated by many researchers.

Complex root canal anatomy and the bacteria behind persistent periapical lesions can be especially difficult to clean and disinfect from the root canal system; such conditions may require using medications between RCT sessions (7). The high pH of Ca(OH)2 makes it the optimal intracanal medicament for RCT (8). As alternative intracanal drugs; triple antibiotic paste (TAP) is prepared by mixing ciprofloxacin, metronidazole, and minocycline antibiotics in equal proportions (1:1:1) (8), and double antibiotic paste (DAP) is obtained by mixing ciprofloxacin and metronidazole in equal proportions (1:1) (9).

In RCT, one of the biggest issues is the full eradication of intracanal medicaments that have stayed in root canals between treatment sessions (7). Prior research has revealed that it is impossible to completely flush or agitate away intracanal dressings from root canals (6,10). The influence of Ca(OH)2 as an intracanal dressing on the accuracy of EALs has been explored in previous literature (5,6,11). Nevertheless, no research has assessed the impact of intracanal applications of DAP and TAP on the precision of EALs.

This study aimed to analyze the effect of various intracanal medicaments on the accuracy of four EALs. This study hypothesized that the accuracy of EALs would not vary significantly when exposed to various medication residues.

Materials and Methods

This laboratory study has been composed in accordance with the Preferred Reporting Items for Laboratory studies in Endodontology 2021 guidelines (12). The Erciyes University Clinical Research Ethics Committee gave their consent to conduct this study (decision no: 2020/110, date: 12.02.2020). The G*Power v. (Heinrich Heine, Düsseldorf University, Düsseldorf, Germany) program was employed to ascertain the necessary minimum sample size. An alpha-type error of 0.05, an effect size of 0.26 and a beta power of 0.80 were set, thus determining the minimal estimated sample size to be 160.

Selection and Preparation of Samples

This study used 160 extracted human maxillary central incisors. Radiographs were taken of the specimens in mesiodistal and buccolingual directions to verify the presence of straight single canals. Teeth with root canal obliteration, excessive coronal tissue loss, and internal or external resorption were excluded and replaced by two examiners (T.A., H.C.).

Testing was conducted after the teeth were submerged in a 0.1% thymol solution. Teeth were decoronated at the cementoenamel junction with a Minitome precision cutting device (Struers ApS, Ballerup, Denmark) to establish a fixed reference point. After locating the root canal orifices, canal patency was checked using a 10 K-type hand file (EndoArt, Incidental, İstanbul, Turkey). The root canals were enlarged using a 25 Wave One Gold rotary file system (Dentsply). During root canal preparation, the canals were irrigated with 2.5 mL of 2.5% NaOCl, followed by 2.5 mL of distilled water. Paper cones were utilized to dehydrate the canals, and appropriate root canal conditions were obtained prior to the application of intracanal medicaments.

Actual Working Length (AL) Determination

An experienced clinician (T.A.) ascertained actual working length using an operating microscope (OPMI Pico, Carl Zeiss Gmbh., Jena, Germany) at 10× magnification. A 25 K-type hand file was advanced until it could be seen apically. The rubber stopper of the file was fixed and a digital calliper was employed to measure the space between the file tip and the stopper. This measurement minus 0.5 mm yielded the actual working lengths.

Applying Medicaments to Canals

The samples were distributed into four groups (n=40) randomly with regard to the type of intracanal medication being used.

Group 1 [Ca(OH)2]: Ca(OH)2 powder (Kalsin; Spot Dis Deposu AS, İzmir, Turkey) and distilled water were mixed in a 1:1.5 proportion until a creamy consistency was obtained. The root canals were filled using a lentulo spiral until Ca(OH)2 was visible at the apex.

Group 2 (DAP): DAP was obtained by mixing ciprofloxacin (Cipro, Biofarma, İstanbul, Turkey) and metronidazole (Nidazol, IE Ulagay, İstanbul, Turkey) in equal proportions (1:1). Sterile saline solution was used as a carrier to form a paste of the antibiotics and mixed until it reached a creamy consistency. The root canals were filled using a lentulo spiral until DAP was seen at the apex.

Group 3 (TAP): TAP was obtained by mixing ciprofloxacin, metronidazole, and minocycline (Skid, Zentiva, Frankfurt, Germany) in equal proportions (1:1:1). Sterile saline solution was used as a carrier to mix the antibiotic powder into a paste with a creamy consistency. The root canals were filled using a lentulo spiral until TAP was seen at the apex.

Group 4 (Control): In the control group, no intracanal medication was delivered into the root canals of the samples.

Detection of Electronic Lengths (EL)

The medicaments were left in the root canals of the samples for one week, and then the temporary fillings were removed. No additional preparation was performed, and the root canals were irrigated with 17% EDTA using a 30-G needle. The specimens were embedded in a plastic mould filled with alginate, keeping 2 mm of the teeth crowns visible.

After randomly allocating 40 teeth to four subgroups (n=10), each subgroup was assigned an EAL measurement. Prior to measurement, the lip clip was placed in the alginate, and all measurements were completed within 2 hours to ensure that the alginate remained moist. A 25 K-type hand file (EndoArt, Incidental, İstanbul, Turkey) was used during the measurement.

All measurements were performed by an experienced clinician (H.C.) and conducted for each device following the instructions provided by the manufacturers. In these instructions, the markings on the products and how to interpret the numerical values were specified to indicate the apical constriction point.

Representative samples from each group were divided into two halves. Stereomicroscope images were then obtained to determine if the intracanal medicament in the root canals could be completely removed (Figure 1).

Statistical Analysis

All statistical analyses were carried out with SPSS 22.0 (SPSS Inc., IL, USA) employing an alpha value of 0.05. The normality of the data was examined with the Shapiro-Wilk test, which demonstrated that all data were normally distributed (p>0.05). The EL-AL scores for each medication group were categorized within the margin of ±0.5 and ± 1 mm, the chi-square (χ2) test was utilized to contrast the precision of the EALs, with a significance level of 0.05.


The descriptive statistics of EL-AL values of EALs tested in different medicament groups are presented in Table 1. No statistical variation was found between the four EALs when evaluating measurements in the presence of different intracanal medicaments, given the tolerance of ±0.5 and ±1 mm (χ2 tests, p>0.05).

Figure 2 details the success levels of EALs based on intracanal medicaments staying within the ±0.5 mm tolerance limit.

In addition, no strong correlation was observed between the EL-AL differences and the type of residual medication [r=0.296 for Ca(OH)2; r=0.025 for TAP; r=0.123 for DAP].


No residual intracanal medication should be left in the root canals; otherwise, these residues could impede the successful integration of root canal filling materials with the root canal walls (13). Therefore, various irrigation agents and techniques have been proposed to take out intracanal dressings from the root canal. According to previous studies, Ca(OH)2, DAP, and TAP could not be completely removed from the root canal (6,14,15). In contrast, EDTA showed significantly greater success in eliminating Ca(OH)2 than other irrigation solutions (16,17). In addition, EDTA can be effectively used to remove antibiotic pastes from root canals (14,18). In light of these findings, 17% EDTA was utilized in this study to dislodge intracanal medicaments from the root canal.

The impact of using Ca(OH)2 as an intracanal drug on the precision of apex locator devices has been investigated in previous studies with conflicting results (5,6,11). In the Ca(OH)2 group in this study, there was no notable discrepancy in the measurement accuracies of the four EALs at the ±0.5 and ±1 mm tolerance limits (p>0.05). Our results are consistent with those of Shojaee et al.’s (11).

This might be because the EALs used in both studies operated at nearly equal frequencies. Although there was no discernible statistical variation in the accuracy of EALs, Raypex 6 and Ipex 2 showed more consistent results than other EALs used in the Ca(OH)2 group within the tolerance limit of ±0.5 mm. This might be due to variations in the apical anatomy of samples.

Analyses did not reveal any noteworthy variation in the precision of the four EALs when taking into account the ±0.5 and ±1 mm boundary conditions in the DAP and TAP groups (p>0.05). Considering the composition of DAP and TAP, only TAP contains minocycline. Minocycline is an antibiotic containing tetracycline, and it has a slight effect on removing the smear layer (19). Due to potential surface modifications caused by the smear layer’s removal, such as the opening of tubules on the root dentin surface, dissolution of the inorganic structure, and movement of the dentin fluid (20) electronic measurement results may be affected. However, the lack of differences in the statistical results indicate that the antibiotic with the active ingredient minocycline did not significantly affect modern EALs. This might be because minocycline is a weak chelating agent at low doses and induces limited demineralization on the dentin surface (21).

Although no noteworthy distinction was observed between Raypex 6 and Apex ID in the TAP group, Raypex showed a higher accuracy in the DAP group, compared with other EALs, within the tolerance limit of ±0.5 mm. Due to the similar frequency ranges of EALs used in this study, no statistically significant difference may have occurred; however, small variations in frequencies may lead to small differences in the percentage of accuracy.

Ca(OH)2, DAP and TAP groups showed less consistent results than the control group in measurements made with Propex Pixi. In the measurements made with Apex ID, the most consistent results were obtained in the TAP group, while the most inconsistent results were obtained from the Ca(OH)2 group. However, these results as percentages are not statistically significant (p>0.05). These results may be due to the differences of apical anatomy in the samples.

The strengths of the present study are that the electronic measurement with EALs performed by another clinician who is unaware of the actual length measurements carried out under the operating microscope, and the differences between ELs and ALs were evaluated at a precision of 0.01 mm. All the EALs in this research showed optimum results with 100% accuracy in the four groups within the tolerance limit of ±1 mm. This was consistent with the findings of other studies in the literature (22). It is thought that the reason for the high accuracy rate within the 1 mm error range of the EALs tested in this study could be attributed to the remarkable technical characteristics of these contemporary EALs.

One of the shortcomings of this study was its in vitro nature hence the results of this study need to be verified in vivo. More research in a laboratory setting and in clinical trials is needed to back up the discoveries of this study.


Within the confines of this study, contemporary EALs equipped with advanced technology were dependable in setting the working length despite the presence of DAP, TAP, and Ca(OH)2 residue in the root canal.


Ethics Committee Approval: The Erciyes University Clinical Research Ethics Committee gave their consent to conduct this study (decision no: 2020/110, date: 12.02.2020).

Informed Consent: This study does not require informed consent.

Peer-review: Externally peer-reviewed.

Authorship Contributions

Surgical and Medical Practices: H.C., Concept: H.C., T.A., B.K., Design: H.C., T.A., Data Collection or Processing: H.C., T.A., Analysis or Interpretation: T.A., Literature Search: H.C., T.A., B.K., Writing: H.C., B.K.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: This study was supported by the Erciyes University Scientific Research Projects Department (Project number: TDH-2020-10292).


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