Influence of the Maxillary Sinus on the Accuracy of the Root ZX Apex Locator

dentistry journal

Article Inﬂuence of the Maxillary Sinus on the Accuracy of the Root ZX Apex Locator: An Ex Vivo Study

Roula El Hachem 1,*, Elie Wassef 2, Nadim Mokbel 2, Richard Abboud 3, Carla Zogheib 1, Nada El Osta 4 and Alfred Naaman 1

1 Department of Endodontics, Faculty of Dentistry, Saint Joseph University, P.O. Box 11-5076 Riad el-Solh, Beirut 1107 2180, Lebanon; [email protected] (C.Z.); [email protected] (A.N.) 2 Department of Periodontics, Faculty of Dentistry, Saint Joseph University, P.O. Box 11-5076 Riad el-Solh, Beirut 1107 2180, Lebanon; [email protected] (E.W.); [email protected] (N.M.) 3 Department of Maxillo-Facial Radiology, Saint Joseph University, B.P. 11-514 Riad el-Solh, Beirut 1107 2050, Lebanon; [email protected] 4 Department of Prosthodontics, Saint Joseph University, B.P. 11-514 Riad el-Solh, Beirut 1107 2050, Lebanon; [email protected] * Correspondence: [email protected]; Tel.: +961-3836040 or +961-5452805

Received: 15 October 2018; Accepted: 11 December 2018; Published: 2 January 2019

Abstract: This study evaluated the accuracy of the Root ZX (J. Morita, Tokyo, Japan) electronic apex locator in determining the working length when palatal maxillary molar roots are in a relationship with the sinus. Seventeen human maxillary molars with vital pulp were scheduled for an extraction and implant placement as part of a periodontal treatment plan. The access cavity was prepared, and a #10 K file (Dentsply Maillefer, Ballaigues, Switzerland) was inserted into the palatal root using the Root ZX apex locator in order to determine the electronic working length (EWL); then, the teeth were extracted. To determine the real working length (RWL), a #10 K file was introduced into the root canal until its tip touched a glass plate. EWL and RWL were compared. Images reconstructed with CBCT (cone beam computerized tomography) revealed that eight palatal roots were related to the maxillary sinus, whereas nine were not. The results showed a significant difference between the EWL and the RWL of the palatal roots related to the sinus (p < 0.001). No significant difference was observed in measurements of roots not in contact with the sinus (p > 0.05). Within the study limitations, the reliability of Root ZX was influenced by the relationship of the roots with the maxillary sinus.

Keywords: maxillary molar; maxillary sinus; working length; Root ZX; apex locator

1. Introduction The elimination of microorganisms and pulp tissue from the root canal system is a crucial step for endodontic success [1,2], and such treatment should be confined within the roots [3,4]. This can only be achieved when the root canal length is determined with accuracy. Any endodontic act beyond or below this limit may increase the risk of failure due to overfilling or underfilling [5]. It is sometimes tricky to precisely determine the root canal preparation length using periapical radiographs, since they are subject to distortion, are sensitive in interpretation, and they only give a two-dimensional image of the three-dimensional roots [6]. The introduction of electronic apex locators (EAL) has allowed better reliability in working length (WL) determination [7,8] while minimizing the exposure of patients to radiation [9]. The latest generation of these devices determines the WL by measuring the variation of impedance by using different frequencies in the instrument tip within the canal [10]. Root ZX (J. Morita, Tokyo, Japan) is an accurate, third-generation EAL that expresses the quotient between the impedances of two frequencies

Dent. J. 2019, 7, 3; doi:10.3390/dj7010003 www.mdpi.com/journal/dentistry Dent. J. 2019, 7, 3 2 of 10

(0.4 and 8 kHz) and indicates the position of the instrument inside the root canal. It ensures high levels of efficiency and accuracy, making it the gold standard EAL [11–13]. However, some conditions might affect its performance. The influence of various factors on the accuracy of Root ZX has been studied, such as the degree of root canal curvature [14], tooth group [15], apical foramen diameter and file size [16], pulp vitality [17], presence of irrigants [18], and endodontic perforation [19]. Piasecki et al. [20] found that EAL performance may be affected by apical anatomic complexities. However, the effect of root apices being in contact with the maxillary sinus on the reliability of EAL has not been studied. The maxillary sinus is an anatomic organ that is localized near the nasal cavity in close proximity to the upper molars [21]. Crucial care should be taken during surgeries [22,23] and endodontic therapy on molars with roots in close proximity to the maxillary sinus [24]. Related to this, Matsumoto et al. [25] showed that odontogenic infection was the cause of 70% of 190 studied unilateral sinusitis cases. The occurrence of iatrogenic errors may induce sinusitis and infections resulting from thickening of the maxillary sinus mucosa [26] or the extrusion of endodontic files, irrigation solutions, or sealers into the sinus cavity while performing cleaning and obturation of the root canal system [27,28]. Cone beam computerized tomography (CBCT) imaging is an advanced, indicative imaging technique that has been adopted in root canal treatment for the three-dimension study of the root canal anatomy [29–32], as well as the evaluation of root resorption, the diagnosis of root fracture [33], and the determination of presurgical strategies [34,35]. It enables the topographic relationship between the sinus floor (MSF) and the maxillary molar roots to be established [36–38]. According to Aksoy and Orhan [39], in 84% of the second molars and in 77% of the first molars, at least one of the roots protrudes into the sinus or is in contact with it. Gu et al. [21] reported that maxillary molars are closer to the MSF than premolars and that age has a significant influence on the relationship between upper molars and the MSF. CBCT represents an important modality with great potential for clinical practice and precision compared to conventional radiography [40,41]. CBCT imaging offers several advantages over medical computed tomographic imaging, including its ease of use for dental applications, reduction of radiation doses, and lower cost [42–45]. To date, no studies have investigated the effect of apical root canal sinus projection on EAL accuracy. Considering the importance of the correct determination of WL when treating the upper molars, the relationship between the maxillary sinus and the roots of the maxillary posterior teeth, and to avoid endodontic complications of the sinus tissues, the aim of this ex vivo study was to evaluate the reliability of Root ZX when root canals are in contact with the maxillary sinus. The null hypothesis tested was that there are no significant differences in the reliability of the Root ZX between the roots whether they are in contact or not in contact with the maxillary sinus.

2. Materials and Methods This study was approved by the Ethics Committee of Saint Joseph University Beirut (USJ-2018-10) on 20 February 2018.

2.1. Selection of Teeth Patients in good general health aged 50 to 60 years old were recruited from the Dental Health Care Center of Saint Joseph University of Beirut. They were scheduled for the extraction of an upper molar and placement of an implant as part of their periodontal treatment plan. After clinical and radiographic examinations, only maxillary molars with vital pulp and no symptoms of pulpitis were included in the study. Molars with open apices, fractures, root resorptions, calciﬁcations, or previous endodontic treatments were excluded. Seventeen palatal roots were ﬁnally included in this study and written informed consent was obtained from the participants. Dent. J. 2019, 7, 3 3 of 10

Dent.2.2.Dent. ImagingJ. J. 2018 2018, ,6 6, , Proceduresx x FOR FOR PEER PEER REVIEW and REVIEW Evaluation of the CBCT Images 33 ofof 1010 Preoperatively, all patients received limited CBCT imaging as part of preimplant planning. Preoperatively,Preoperatively, all all patients patients received received limited limited CBCT CBCT imaging imaging as as part part of of preimplant preimplant planning. planning. The The The imaging system used was the NewTom VGI (QR, Verona, Italy) cone beam computed tomography imagingimaging system system used used was was the the NewTom NewTom VGI VGI (QR, (QR, Verona, Verona, Italy) Italy) cone cone beam beam computed computed tomography tomography (CBCT) with the following parameters: 3.3 mA, 110 kVp, 7.5 × 12 cm scan ﬁeld of view, and 0.150 mm (CBCT)(CBCT) with with the the following following parameters parameters: :3.3 3.3 mA, mA, 110 110 kVp, kVp, 7 7.5.5 × × 12 12 cm cm scan scan field field of of view, view, and and 0.150 0.150 voxel size. The CBCT images were established by employing OnDemand3D software (Cybermed, mmmm voxel voxel size. size. TheThe CBCTCBCT images images were were established established byby employingemploying OnDemand3D OnDemand3D software software Seoul, Korea) concordant to the operating parameters. Images were examined by an experienced oral (Cybermed,(Cybermed, Seoul, Seoul, Korea Korea) ) concordant concordant to to the the operating operating parameters. parameters. Images Images were were examined examined by by an an radiologist in order to conﬁrm whether or not the palatal root was in contact with the sinus, as shown experiencedexperienced oral oral radiologist radiologist in in order order to to confirm confirm whether whether or or not not the the palatal palatal root root was was in in contact contact with with in Figures1 and2. thethe sinus, sinus, as as shown shown in in Figures Figures 1 1 and and 2. 2.

aa bb cc mmmm 00 00 00 000000 00 00 0 0 00 00 00 00 00 00FigureFigure 1. 1. Representative Representative cone cone beam beam computed computed tomography tomography (CBCT) (CBCT) images imagesimages showing showing the thethe palatal palatal root root apexapex not not in in contact contact with with the the sinus sinus floor floor (MSF). (MSF). ( a(a,c,c) )A A maxillary maxillary axial axial CBCT CBCT view; view; ( b(b) )a a maxillary maxillary 0 apex not in contact with the sinus floor (MSF). ( , ) A maxillary axial CBCT view; ( ) a maxillary 0sagittalsagittalsagittal CBCT CBCT view. view.1; view.11; ; 5 5 and and 10 10 are are the the slices slices numbers. numbers. 00 0 a0a bb cc mmmm 0 00 00 00 0 0 0 00 00 00 0 00 00 00 0 0 00 00 0 0 00 00 00 00 00 00 FigureFigure 2. 2.2. Representative RepresentativeRepresentative CBCT CBCT CBCT images images images0 0showing showing showing the the palatal thepalatal palatal root root apex rootapex inapex in contact contact00 in contact with with the the with MSF MSF the. .( a(a, MSF.c,c) )A A 0 0maxillary(amaxillary,c) A maxillary axial axial CBCT CBCT axial CBCTview; view; ( view; b(b) )a a maxillary (maxillaryb) a0 maxillary0 sagittal sagittal sagittal CBCT CBCT CBCT view view view.. .1 1; ;5 5 and 1;and 5 and10 100 0are are 10 the arethe slices the slices slices numbers. numbers. numbers. 00 2.3. Determination of the Electronic Working00 Length Using Root ZX 00 2.2.33. .Determination Determination of of the the Electronic Electronic Working Working Length Length Using Using Root Root ZX ZX 00 00 The determination of the working0 length0 of the palatal root was completed by one endodontist 00TheThe determination determination of of the the working working length length of of the the palatal palatal root root was was completed completed by by one one endodontist endodontist who was blinded to the results of the CBCT.00 After applying local anesthesia00 and placing the rubber whowho was was blinded blinded to to the the results results of of the the CBCT. CBCT. After After applying applying local local anesthesia anesthesia and and placing placing the the rubber rubber dam,00 an access cavity was done on each tooth using a handpiece at high00 speed. The reference point dam,dam, an an access access cavity cavity was was done done on on each each00 tooth tooth using using a a handpiece handpiece at at high high speed. speed. The The reference reference point point was00 standardized by flattening the palatal cusp tip. The Root ZX apex locator then determined the waswas standardized standardized by by flattening flattening the the palatal palatal00 cusp cusp tip. tip. The The Root Root ZX ZX apex apex0 0locator locator then then determi determinedned the the EWL0 in accordance with the manufacturer’s instructions. A #10 K file (Dentsply Maillefer, Ballaigues, EWLEWL0 in in accordance accordance with with the the manufacturer manufacturer00 ’s’s instructions. instructions. A A #10 #10 K K file file ( Dentsply(Dentsply00 Maillefer, Maillefer, Ballaigues, Ballaigues, Switzerland) was connected to the file clip of the EAL and inserted apically into the canal until the SwitzerlandSwitzerland00 ) )was was connected connected to to the the file file clip clip of of the the EAL EAL and and inserted inserted apically apically00 into into the the canal canal until until the the “Apex mark” appeared. The silicone stop00 was then cemented to the file with light-cured glass ionomer “Apex“Apex00 mark” mark” appeared. appeared. The The silicone silicone stop stop was was thenthen cemented cemented to to the the file file with with light light-cured-cured glass glass cement (GC Fuji® Automix LC, GC Corp.,00 Tokyo, Japan), and the distance00 between the stop and the file ionomerionomer cement cement (GC (GC Fuji Fuji®® Automix Automix LC, LC, GC GC Corp Corp.,. ,Tokyo, Tokyo, Japan) Japan), ,and and the the distance distance between between the the stop stop tip0 was0 measured with a digital caliper at 5× magnification (Carl Zeiss GmbH,00 Oberkochen, Germany). andand the the file file tip tip was was measured measured with with 0 0 a a digital digital caliper caliper at at 5 5×× magnificationmagnification (Carl (Carl Zeiss Zeiss GmbH, GmbH, The00 working length obtained for each canal was then recorded and noted as the EWL. The canal was Oberkochen,Oberkochen, Germany). Germany). The The working working length length00 obtained obtained for for each each canal canal was was00 then then recorded recorded and and noted noted as as irrigated with 2.5% sodium hypochlorite (NaOCl), the rubber dam was removed, and an oral surgeon thethe0 0 EWL.EWL. The The canal canal was was irrigated irrigated w withith0 2.5% 2.5% sodium sodium hypochlorite hypochlorite (NaOCl), (NaOCl),00 the the rubber rubber dam dam was was extracted the tooth and checked it to ensure0 that the root tips were not broken. A solution of 2.5% removedremoved00 , ,and and an an oral oral surgeon surgeon extracted extracted the the tooth tooth and and checked checked it it to to en ensuresure0 that that the the root root tips tips were were not not NaOCl was used to disinfect the root surface,00 and then the teeth were saved0 for 20 minutes in a saline broken.broken.00 A A solution solution of of 2.5% 2.5% NaOCl NaOCl was was used used to to disinfect disinfect the the root root surface surface, ,and and then then the the teeth teeth were were solution in order to measure their real working00 lengths. 00 savedsaved for for 20 20 minutes minutes in in a a saline saline solution solution in in order order to to measure measure their their real real working working length lengthss. . 00 00 2.4.2.4. Determination Determination of of the the Real Real Working Working Length Length00 Using Using a a G Glasslass P Platelate 00 TheThe real real working working length length (RWL) (RWL) of of0 the0 the palatal palatal root root was was measured measured using0 using0 a a glass glass plate plate tangential tangential toto the the plane plane of of the the anatomic anatomic foramen foramen, ,and 0and0 a a #10 #10 K K-file-file ( Dentsply(Dentsply Maillefer, Maillefer,00 Ballaigues, Ballaigues, Switzerland Switzerland) ) 00 00

00 00 00 00 00 00 00 Dent. J. 2019, 7, 3 4 of 10

2.4. Determination of the Real Working Length Using a Glass Plate The real working length (RWL) of the palatal root was measured using a glass plate tangential to the plane of the anatomic foramen, and a #10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) was introduced into the root canal until its tip touched the glass plate. The file was then cemented to the ® siliconeDent. stop J. 2018 using, 6, x FOR light-cured PEER REVIEW glass ionomer cement (GC Fuji Automix LC, GC Corp., Tokyo,4 of 10 Japan) in order to prevent movement. The file was then extracted, and the measurement was taken between the stopwas andintroduced the file into tip. the The root endodontist canal until its applied tip touched the same the glass technique plate. The as file in EWLwas then in order cemented to measure to distances.the silicone The WL stop obtained using light for-cured each glas canals ionomer was then cement recorded (GC Fuji and® notedAutomix as theLC, RWL.GC Corp., Tokyo, Japan) in order to prevent movement. The file was then extracted, and the measurement was taken 2.5. Statisticalbetween the Analyses stop and the file tip. The endodontist applied the same technique as in EWL in order to measure distances. The WL obtained for each canal was then recorded and noted as the RWL. Statistical analyses were performed using the Statistical Package Software for Social Science (SPSS2.5. for Statistical Windows, Analyses Version 17.0, Chicago, IL, USA). The level of significance was set at p < 0.05. For each tooth,Statistical EWL and analyses RWL were performedrecorded three using times, the Statistical and the Package average Software measurement for Social was Science calculated and used(SPSSfor for theWindows, statistical Version analysis. 17.0, Chicago, The WL IL, error USA). was The calculated level of significance by subtracting was set theat p EWL< 0.05. fromFor the RWLeach (Error tooth, = EWL EWL −andRWL). RWL Negativewere recorded and three positive times values, and the indicated average measurement measurements was that calculated were short and longand used of the for real the length, statistical respectively, analysis. The whereas WL error 0.0 was indicated calculated coinciding by subtracting measurements. the EWL from The accuracythe of theRWL WL (Error measurements = EWL − RWL). was assessed Negative using and positive Student valuest-tests indicated to compare measurements the mean errorthat were between short roots in contactand long and of roots the real with length no contact, respectively, with the whereas sinus. 0.0 Paired indicated Student coincidingt-tests measurements. were also executed The to compareaccuracy the meanof the EWLWL mea andsurements RWL values was forassessed palatal using roots Student in contact t-tests or to not compare in contact the mean with error the sinus. between roots in contact and roots with no contact with the sinus. Paired Student t-tests were also One-sample t-tests were used to compare the mean error value with the theoretical value, 0, which executed to compare the mean EWL and RWL values for palatal roots in contact or not in contact assumes the absence of error. with the sinus. One-sample t-tests were used to compare the mean error value with the theoretical value, 0, which assumes the absence of error. 3. Results Seventeen3. Results palatal roots were finally included in this study. The CBCT images showed that eight were in contactSeventeen with palatal the sinus roots and were nine finally were included not. A in comparison this study. The of theCBCT EWL images versus showed the RWL that eight of palatal rootswere related in contact to or not with related the sinus to theand sinusnine were are detailed not. A comparison in Figures of3 theand EWL4. The versus mean the measurements RWL of palatal and standardroots deviationsrelated to or obtained not related in to groups the sinus are are shown detailed in Tablein Figures1. There 3 and were 4. The no mean significant measurements differences in theand EWL standard and RWL deviations when the obtained roots were in groups not inare a relationship shown in Table with 1. the There sinus were (p =no 0.744). significant However, the meandifference EWLs wasin the significantly EWL and RWL higher when than the roots RWL w forere rootsnot in relateda relationship to the with sinus the (p sinus= 0.001). (p = 0.744). Moreover, However, the mean EWL was significantly higher than RWL for roots related to the sinus (p = 0.001). palatal roots in relation with the maxillary sinus had a mean error that was significantly different from Moreover, palatal roots in relation with the maxillary sinus had a mean error that was significantly 0 (+0.974, p = 0.001). However, the mean error was not statistically significant for palatal roots with no different from 0 (+0.974, p = 0.001). However, the mean error was not statistically significant for palatal − sinusroots contact with ( no0.041, sinus pcontact= 0.639). (−0.041, p = 0.639).

Palatal roots in contact with the sinus

24 22 20 18 16 14 12 10 8 6 4 2 0 Root Root length(mm) 1 2 3 4 5 6 7 8 EWL 18.67 17.89 15.54 18.69 17.43 14.74 19.88 15.38 RWL 17.53 16.63 14.89 18.1 15.5 14.05 18.89 14.84 Error 1.14 1.26 0.65 0.59 1.93 0.69 0.99 0.54

FigureFigure 3. Electronic 3. Electronic working working length length (EWL) (EWL versus) versus real real working working length length (RWL) (RWL of) palatalof palatal roots roots in contact in withcontact the sinus. with the sinus.

Dent. J. 2019, 7, 3 5 of 10 Dent. J. 2018, 6, x FOR PEER REVIEW 5 of 10

Palatal roots not in contact with the sinus

24 22 20 18 16 14 12 10 8 6 4 2 0 Root Root (mm)length 1 2 3 4 5 6 7 8 9 EWL 16.52 20.78 22.34 19.73 16.55 17.09 22.17 19.03 21.84 RWL 16.55 20.8 22.3 19.79 17.21 17.08 22.14 18.74 21.81 Error -0.03 -0.02 0.04 -0.06 -0.66 0.01 0.03 0.29 0.03

Figure 4. EWLEWL versus versus RWL of palatal roots not in contact with the sinus.sinus.

Table 1.1. Mean and standard deviation measurements (in mm) of differences between the EWL and the RWL RWL..

GroupsMean Mean RWL RWL (mm)Mean Mean EWL EWL (mm) Mean Error Groups Mean Error Roots in contact with the sinus (n = 8)(mm) 16.304 ± 1.748(mm) 17.278 ± 1.858 +0.974 ± 0.470 Roots notRoots in contactin contact with with the the sinus sinus (n = 9) 19.602 ± 2.297 19.561 ± 2.396 −0.041 ± 0.253 16.304 ± 1.748 17.278 ± 1.858 +0.974 ± 0.470 (n = 8) Roots not in contact with the 4. Discussion 19.602 ± 2.297 19.561 ± 2.396 −0.041 ± 0.253 sinus (n = 9) The aim of this study was to evaluate the reliability of the Root ZX locator when root canals are in 4.contact Discussion with the maxillary sinus. To our knowledge, the effect of the relationship between the root apex of upper molars and the maxillary sinus on EAL accuracy has not been studied previously. The aim of this study was to evaluate the reliability of the Root ZX locator when root canals are Recently, different studies have reported the exactitude of several EALs [14,46–48]. In this in contact with the maxillary sinus. To our knowledge, the effect of the relationship between the root current ex vivo study, one of the critical steps in this process was the standardization of samples. apex of upper molars and the maxillary sinus on EAL accuracy has not been studied previously. We used the palatal roots of the first and second maxillary molars, and all teeth were flattened to allow Recently, different studies have reported the exactitude of several EALs [14,46–48]. In this standardization and the creation of a flat reference point for accurate measurements [49]. Each tooth current ex vivo study, one of the critical steps in this process was the standardization of samples. We was isolated with a rubber dam to obtain a stable electronic reading [50]. All specimens were measured used the palatal roots of the first and second maxillary molars, and all teeth were flattened to allow by the same Root ZX locator, as well as by the glass plate method. In addition, patients were of similar standardization and the creation of a flat reference point for accurate measurements [49]. Each tooth age, which provided comparable root growth and prevented morphological divergences. was isolated with a rubber dam to obtain a stable electronic reading [50]. All specimens were Although Tsesis et al. [51] showed that EALs are not influenced by the pulp status, this study only measured by the same Root ZX locator, as well as by the glass plate method. In addition, patients consisted of teeth with vital pulp tissue in order to remove any potential bias. The Root ZX locator was were of similar age, which provided comparable root growth and prevented morphological used in accordance with the manufacturer’s instructions with a size #10 K file [52]. Although Nguyen divergences. et al. [53] claimed that the accuracy of EALs is not affected by the file size, the same file size was used Although Tsesis et al. [51] showed that EALs are not influenced by the pulp status, this study in all canals to provide similar conditions for EWL and RWL. In this report, in contrast to the study only consisted of teeth with vital pulp tissue in order to remove any potential bias. The Root ZX conducted by Azabal et al. [54], the teeth were not decoronated; this kept the investigation variables locator was used in accordance with the manufacturer’s instructions with a size #10 K file [52]. nearest to an in vivo condition. Furthermore, the determination of the RWL was made when the #10 K Although Nguyen et al. [53] claimed that the accuracy of EALs is not affected by the file size, the file reached firm contact with the glass plate, instead of only using visual magnification; this gave a same file size was used in all canals to provide similar conditions for EWL and RWL. In this report, reduced margin of error. in contrast to the study conducted by Azabal et al. [54], the teeth were not decoronated; this kept the In the present study, all CBCT images were taken before the study, and no additional X-rays were investigation variables nearest to an in vivo condition. Furthermore, the determination of the RWL done to reduce radiation. According to the classification of vertical relationships between the root apex was made when the #10 K file reached firm contact with the glass plate, instead of only using visual of the second molars and the MSF, the frequency of a root projection in the sinus varies between 14% magnification; this gave a reduced margin of error. and 23% [51,55]. Wallace [56] reported that in 40% of cases, the first and the second maxillary molars In the present study, all CBCT images were taken before the study, and no additional X-rays communicate with the sinus. In this study, the CBCT taken as preimplant treatment planning was also were done to reduce radiation. According to the classification of vertical relationships between the used to assess whether the palatal maxillary molar roots were in contact with the sinus. The CBCT root apex of the second molars and the MSF, the frequency of a root projection in the sinus varies between 14% and 23% [51,55]. Wallace [56] reported that in 40% of cases, the first and the second maxillary molars communicate with the sinus. In this study, the CBCT taken as preimplant treatment

Dent. J. 2019, 7, 3 6 of 10 axial and sagittal images clearly showed that eight roots were associated with the sinus and nine were not. This research showed a significant difference between the EWL and the RWL of the palatal roots in relation with the sinus, but did not demonstrate a significant difference in measurements with roots that were not in contact with the sinus. The EWL was revealed to be significantly longer than the RWL when the palatal roots were in contact with the sinus. Previous investigations showed overestimated measurements in 2.56% [12], 7.9% [57], and 3.1% [58] of cases, respectively, when using the Root ZX. However, in one study that analyzed WL determination, the use of Root ZX was found to significantly reduce the incidence of working length overestimation compared to periapical radiographs [59]. One explanation for the results of the current study may be that roots in contact with the maxillary sinus have different levels of impedance than roots not in contact with the sinus. This finding is crucial, since it demonstrates the risk of over instrumentation, especially for those endodontists who only use the EAL to accomplish their root canal treatment. This is clinically important as inaccurate determination of the WL when treating teeth with close proximity to the maxillary sinus may induce the extension of bacteria, endodontic tools, intracanal solutions, and root canal fillings into the sinus [36]. The introduction of necrotic debris and microorganisms into the sinus could cause chronic sinusitis [60]. Kang et al. [37], who found a close distance between the root apexes of upper molars and the MSF and procured approximate measurements from the root apexes to the buccal cortical plate, stressed the importance of giving appropriate attention when treating upper molars. In addition, overestimated WL can be accompanied by microbial contamination, injury to the periapical tissues, and pain, reducing the success rate of root canal therapy [3,61]. Correct bacterial disinfection, pertinent shaping, and three-dimensional obturation of the root canal system rely on the precise determination of the root length [62,63]. The Root ZX locator is considered a reference to which other EALs are compared [64], and several investigations have evaluated its reliability [65,66]. In the current study, for teeth not in contact with the sinus, there was no significant difference between the EWL and RWL. This is in accordance with results from other authors, who measured an accuracy level of Root ZX from 75% to 97.37% [67–69]. This device provides the WL by measuring the impedance with two frequencies between the file and the canal fluid without adjustment or calibration. This is the reason that Root ZX is considered to be highly precise in locating the apical foramen [58,70]. However, some previously conducted studies showed that there are several factors that can adversely influence the results [71,72] or even prohibit accurate WL determination, such as blood [73], the protocol adopted [10], the preoperative pulp status [74], the irrigant used [75], or the presence of open apices [62]. This study showed that the reliability of Root ZX is also influenced by the relationship of the root with the maxillary sinus. There may be some limitations in this investigation. Primarily, the number of specimens was rather low, since strict inclusion criteria were applied. Even though the result of the power test was high, clinical studies over a bigger number of roots with a different degree of clinical situations are necessary to further confirm these findings. Thus, the present study data rejected the null hypothesis that there would be no difference between the roots in contact with the sinus or below it in terms of the reliability of the Root ZX apex locator.

5. Conclusions Despite the limitations of this study, a signiﬁcant difference in the accuracy of the Root ZX apex locator between roots in contact or not in contact with the maxillary sinus was found. Realizing the anatomical relationship between the maxillary posterior teeth and the sinus, the clinician must be particularly cautious to prevent possible complications from root canal treatment involving maxillary posterior teeth. Therefore, it is recommended that periapical radiographs are combined with apex locators to determine an acute and reliable working length to allow the long-term success of the root canal treatment. Dent. J. 2019, 7, 3 7 of 10

Author Contributions: Conceptualization, R.E.H. and A.N.; Formal analysis, N.E.O.; Investigation, R.E.H., E.W., N.M., and R.A.; Methodology, R.E.H. and A.N.; Project administration, R.E.H.; Resources, R.E.H., E.W., and N.M.; Software, R.A.; Supervision, A.N.; Validation, N.E.O. and A.N.; Visualization, R.E.H. and C.Z.; Writing—original draft, R.E.H.; Writing—review and editing, R.E.H., N.E.O., and N.M. Funding: This research received no external funding. Conﬂicts of Interest: The authors declare no conﬂict of interest.

References

1. Siqueira, J.F., Jr.; Rocas, I.N. Distinctive features of the microbiota associated with different forms of apical periodontitis. J. Oral Microbiol. 2009, 1. [CrossRef] 2. ElAyouti, A.; Hülber, J.M.; Judenhofer, M.S.; Connert, T.; Mannheim, J.G.; Löst, C.; Pichler, B.J.; von Ohle, C. Apical constriction: Location and dimensions in molars—A micro–computed tomography study. J. Endod. 2014, 40, 1095–1099. [CrossRef][PubMed] 3. Schaeffer, M.A.; White, R.R.; Walton, R.E. Determining the optimal obturation length: A meta-analysis of literature. J. Endod. 2005, 31, 271–274. [CrossRef][PubMed] 4. Ricucci, D. Apical limit of root canal instrumentation and obturation, part 1. Literature review. Int. Endod. J. 1998, 31, 384–393. [CrossRef][PubMed] 5. Sjogren, U.; Hagglund, B.; Sundqvist, G.; Wing, K. Factors affecting the long-term results of endodontic treatment. J. Endod. 1990, 16, 498–504. [CrossRef] 6. Fouad, A.F.; Reid, L.C. Effect of using electronic apex locators on selected endodontic treatment parameters. J. Endod. 2000, 26, 364–367. [CrossRef][PubMed] 7. De Morais, A.L.; de Alencar, A.H.; Estrela, C.R.; Decurcio, D.A.; Estrela, C. Working Length Determination Using Cone-Beam Computed Tomography, Periapical Radiography and Electronic Apex Locator in Teeth with Apical Periodontitis: A Clinical Study. Iran. Endod. J. 2016, 1, 164–168. 8. Akisue, E.; Gratieri, S.D.; Barletta, F.B.; Caldeira, C.L.; Grazziotin-Soares, R.; Gavini, G. Not all electronic foramen locators are accurate in teeth with enlarged apical foramina: An in vitro comparison of 5 brands. J. Endod. 2014, 40, 109–112. [CrossRef] 9. Martins, J.N.; Marques, D.; Mata, A.; Carames, J. Clinical efficacy of electronic apex locators: Systematic review. J. Endod. 2014.[CrossRef] 10. Nekoofar, M.H.; Ghandhi, M.; Hayes, S.J.; Dummer, P.M.H. The fundamental operating principles of electronic root canal length measurement devices. Int. Endod. J. 2006, 39, 595–609. [CrossRef] 11. Venturi, M.; Breschi, L. A comparison between two electronic apex locators: An in vivo investigation. Int. Endod. J. 2005, 38, 36–45. [CrossRef][PubMed] 12. D’Assunção, F.L.; de Albuquerque, D.S.; Salazar-Silva, J.R.; de Queiroz Ferreira, L.C.; Bezerra, P.M. The accuracy of root canal measurements using the Mini Apex Locator and Root ZX-II: An evaluation in vitro. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endodontol. 2007, 104, E50–E53. [CrossRef][PubMed] 13. Wrbas, K.T.; Ziegler, A.A.; Altenburger, M.J.; Schirrmeister, J.F. In vivo comparison of working length determination with two electronic apex locators. Int. Endod. J. 2007, 40, 133–138. [CrossRef][PubMed] 14. Saatchi, M.; Iravani, S.; Iravani Khaleghi, M.; Mortaheb, A. Influence of Root Canal Curvature on the Accuracy of of Root ZX Electronic Foramen Locator: An in Vitro Study. Iran. Endod. J. 2017, 12, 173–178. [CrossRef][PubMed] 15. Mancini, M.; Felici, R.; Conte, G.; Costantini, M.; Cianconi, L. Accuracy of three electronic apex locators in anterior and posterior teeth: An ex vivo study. J. Endod. 2011, 37, 684–687. [CrossRef][PubMed] 16. Herrera, M.; Abalos, C.; Lucena, C.; Jiménez-Planas, A.; Llamas, R. Critical diameter of apical foramen and of file size using the Root ZX apex locator: An in vitro study. J. Endod. 2011, 37, 1306–1309. [CrossRef] [PubMed] 17. Akisue, E.; Gavini, G.; de Figueiredo, J.A. Influence of pulp vitality on length determination by using the Elements Diagnostic Unit and Apex Locator. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endodontol. 2007, 104, 129–132. [CrossRef] 18. Prasad, A.B.; Harshit, S.; Aastha, S.A.; Deepak, R. An In vitro Evaluation of the Accuracy of Two Electronic Apex Locators to Determine Working Length in the Presence of Various Irrigants. Ethiop. J. Health Sci. 2016, 26, 457–462. [CrossRef] Dent. J. 2019, 7, 3 8 of 10

19. Nazari Moghaddam, K.; Nazari, S.; Shakeri, L.; Honardar, K.; Mirmotalebi, F. In vitro detection of simulated apical root perforation with two electronic apex locators. Iran. Endod. J. 2010, 5, 23–26. 20. Piasecki, L.; Carneiro, E.U.; Neto Westphalen, V.; Brandao, C.; Gambarini, G.; Azim, A. The use of micro computed tomography to determine the accuracy of 2 electronic apex locators and anatomic variations affecting their precision. J. Endod. 2016, 42, 1263–1267. [CrossRef] 21. Gu, Y.; Sun, C.; Wu, D.; Zhu, Q.; Leng, D.; Zhou, Y. Evaluation of the relationship between maxillary posterior teeth and the maxillary sinus floor using cone-beam computed tomography. BMC Oral Health 2018, 18, 164. [CrossRef][PubMed] 22. Maridati, P.; Stoffella, E.; Speroni, S.; Cicciu, M.; Maiorana, C. Alveolar Antral Artery Isolation during Sinus Lift Procedure with the Double Window Technique. Open Dent. J. 2014, 8, 95–103. [CrossRef][PubMed] 23. Beretta, M.; Cicciu, M.; Bramanti, E.; Maiorana, C. Schneider membrane elevation in presence of sinus septa: Anatomic features and surgical management. Int. J. Dent. 2012, 261905. [CrossRef][PubMed] 24. Hauman, C.H.; Chandler, N.P.; Tong, D.C. Endodontic implications of the maxillary sinus: A review. Int. Endod. J. 2002, 35, 127–141. [CrossRef][PubMed] 25. Matsumoto, Y.; Ikeda, T.; Yokoi, H.; Kohno, N. Association between odontogenic infections and unilateral sinus opacification. Auris Nasus Larynx 2015, 42, 288–293. [CrossRef][PubMed] 26. Roque-Torres, G.D.; Ramirez-Sotelo, L.R.; Vaz, S.L.D.A.; Bóscolo, S.M.D.A.D.; Bóscolo, F.N. Association between maxillary sinus pathologies and healthy teeth. Braz. J. Otorhinolaryngol. 2016, 82, 33–38. [CrossRef] [PubMed] 27. Khongkhunthian, P.; Reichart, P.A. Aspergillosis of the maxillary sinus as a complication of overfilling root canal material into the sinus: Report of two cases. J. Endod. 2001, 27, 476–478. [CrossRef][PubMed] 28. Kim, J.W.; Cho, K.M.; Park, S.H.; Park, S.R.; Lee, S.S.; Lee, S.K. Chronic maxillary sinusitis caused by root canal overfilling of Calcipex II. Restor. Dent. Endod. 2014, 39, 63–67. [CrossRef] 29. Patel, S.; Dawood, A.; Ford, T.P.; Whaites, E. The potential applications of cone beam computed tomography in the management of endodontic problems. Int. Endod. J. 2007, 40, 818–830. [CrossRef] 30. Nair, M.K.; Nair, U.P. Digital and advanced imaging in endodontics: A review. J. Endod. 2007, 33, 1–6. [CrossRef] 31. Demirbuga, S.; Sekerci, A.E.; Dincer, A.N.; Cayabatmaz, M.; Zorba, Y.O. Use of cone-beam computed tomography to evaluate root and canal morphology of mandibular first and second molars in Turkish individuals. Med. Oral Patol. Oral Cir. Bucal 2013, 18, 737–744. [CrossRef] 32. Rancitelli, D.; Borgonovo, A.E.; Cicciù, M.; Re, D.; Rizza, F.; Frigo, A.C.; Maiorana, C. Maxilary sinus Septa and Anatomic Correlation with the Schneideerian Membrane. J. Craniofac. Surg. 2015, 26, 1394–1398. [CrossRef][PubMed] 33. Ozer, S.Y. Detection of vertical root fractures of different thicknesses in endodontically enlarged teeth by cone beam computed tomography versus digital radiography. J. Endod. 2010, 36, 1245–1249. [CrossRef] [PubMed] 34. Cotton, T.P.; Geisler, T.M.; Holden, D.T.; Schwartz, S.A.; Schindler, W.G. Endodontic applications of cone-beam volumetric tomography. J. Endod. 2007, 33, 1121–1132. [CrossRef][PubMed] 35. Laino, L.; Troiano, G.; Giannatempo, G.; Graziani, U.; Ciavarella, D.; Dioguardi, M.; Lo Muzio, L.; Lauritano, F.; Cicciù, M. Sinus Lift Augmentation by Using Calcium Sulphate. A Retrospective 12 Months Radiographic Evaluation Over 25 Treated Italian Patients. Open Dent. J. 2015, 22, 414–419. [CrossRef] [PubMed] 36. Kilic, C.; Kamburoglu, K.; Yuksel, S.P.; Yuksel, T. An Assessment of the Relationship between the Maxillary Sinus Floor and the Maxillary Posterior Teeth Root Tips Using Dental Cone-beam Computerized Tomography. Eur. J. Dent. 2010, 4, 462–467. [PubMed] 37. Kang, S.H.; Kim, B.S.; Kim, Y. Proximity of posterior teeth to the maxillary sinus and buccal bone thickness: A biometrical assessment using cone-beam tomography. J. Endod. 2015, 41, 1839–1846. [CrossRef] 38. Tian, X.M.; Qian, L.; Xin, X.Z.; Wei, B.; Gong, Y. An analysis of the proximity of maxillary posterior teeth to the maxillary sinus using cone-beam computed tomography. J. Endod. 2016, 42, 371–377. [CrossRef] 39. Aksoy, U.; Orhan, K. Association between odontogenic conditions and maxillary sinus mucosal thickening: A retrospective CBCT study. Clin. Oral Investig. 2018, 1–9. [CrossRef] Dent. J. 2019, 7, 3 9 of 10

40. Üstün, Y.; Aslan, T.; ¸Sekerci, A.E.; Sa˘gsen,B. Evaluation of the reliability of cone-beam Computed Tomography scanning and Electronic Apex Locator Measurements in Working Length Determination with Large Periapical Lesions. J. Endod. 2016, 42, 1334–1337. [CrossRef] 41. Kasikcioglu, A.; Gulsahi, A. Relationship between maxillarynsinus pathologies and maxillary posterior tooth periapical pathologies. Oral Radiol. 2016, 32, 180–186. [CrossRef] 42. Pauwels, R.; Jacobs, R.; Bosmans, H.; Schulze, R. Future prospects for dental cone beam CT imaging. Imaging Med. 2012, 4, 551–563. [CrossRef] 43. Scarfe, W.C.; Li, Z.; Aboelmaaty, W.; Scott, S.A.; Farman, A.G. Maxillofacial cone beam computed tomography: Essence, elements and steps to interpretation. Aust. Dent. J. 2012, 57 (Suppl. 1), 46–60. [CrossRef] 44. Angelopoulos, C.; Scarfe, W.C.; Farman, A.G. A comparison of maxillofacial CBCT and medical CT. Atlas Oral Maxillofac. Surg. Clin. North. Am. 2012, 20, 1–7. [CrossRef][PubMed] 45. Yılmaz, F.; Kamburo˘glu,K.; ¸Senel,B. Endodontic working length measurement using cone-beam computed tomographic images obtained at different voxel sizes and field of views, periapical radiography, and apex locator: A comparative ex vivo study. J. Endod. 2017, 43, 152–156. [CrossRef][PubMed] 46. Haupt, F.; Hülsmann, M. Consistency of electronic measurements of endodontic working length when using multiple devices from the same manufacturer-an in vitro study. Clin. Oral Investig. 2018. [CrossRef] [PubMed] 47. Baruah, Q.; Sinha, N.; Singh, B.; Reddy, P.N.; Baruah, K.; Augustine, V. Comparative Evaluation of Accuracy of Two Electronic Apex Locators in the Presence of Contemporary Irrigants: An In vitro Study. J. Int. Soc. Prev. Community Dent. 2018, 8, 349–353. [CrossRef] 48. Oliveira, T.N.; Vivacqua-Gomes, N.; Bernardes, R.A.; Vivan, R.R.; Duarte, M.A.H.; Vasconcelos, B.C. Determination of the Accuracy of 5 Electronic Apex Locators in the Function of Different Employment Protocols. J. Endod. 2017, 10, 1663–1667. [CrossRef] 49. Camargo, E.J.; Zapata, R.O.; Mederos, P.L.; Bramante, C.M.; Bernardineli, N.; Garcia, R.B.; de Moraes, I.G.; Duarte, M.A. Influence of preflaring on the Accuracy of Length Determination with Four Electronic apex locators. J. Endod. 2009, 35, 1300–1302. [CrossRef] 50. ElAyouti, A.; Dima, E.; Ohmer, J.; Sperl, K.; von Ohle, C.; Löst, C. Consistency of apex locator function: A clinical study. J. Endod. 2009, 35, 179–181. [CrossRef] 51. Tsesis, I.; Blazer, T.; Taschieri, G.; Fabbro, M.; Corbella, S.; Rosen, E. The precision in electronic apex locators in electronic working length determination: A systematic review and meta-analysis of the literature. J. Endod. 2015, 4, 1818–1823. [CrossRef][PubMed] 52. Kobayashi, C.; Suda, H. New electronic canal measuring device based on the ratio method. J. Endod. 1994, 20, 111–114. [CrossRef] 53. Nguyen, H.Q.; Kaufman, A.Y.; Komorowski, R.C.; Friedman, S. Electronic length measurement using small and large files in enlarged canals. Int. Endod. J. 1996, 29, 359–364. [CrossRef][PubMed] 54. Azabal, M.D.; Garcia-Otero, D.; De la Macorra, J.C. Accuracy of the Justy II Apex locator in determining working length in simulated horizontal and vertical fractures. Int. Endod. J. 2004, 37, 174–177. [CrossRef] [PubMed] 55. Khandewal, D.; Ballal, N.; Saraswathi, M. Comparative evaluation of accuracy of 2 electronic apex locators with conventional radiography: An ex vivo study. J. Endod. 2015, 41, 201–204. [CrossRef][PubMed] 56. Wallace, J.A. Transantral endodontic surgery. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endodontol. 1996, 82, 80–83. 57. De Vasconcelos, B.C.; Do Vale, T.M.; De Menezes, A.S.; Pinheiro-Junior, E.C.; Vivacqua-Gomes, N.; Bernardes, R.A.; Hungaro Duarte, M.A. An ex vivo comparison of root canal length determination by three electronic apex locators at positions short of the apical foramen. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod. 2010, 11, 57–61. [CrossRef] 58. Aguiar, B.A.; Reinaldo, R.S.; Frota, L.M.A.; do Vale, M.S.; Vasconcelos, B.C.D. Root ZX Electronic Foramen Locator: An Ex Vivo Study of Its Three Models’ Precision and Reproducibility. Int. J. Dent. 2017, 5893790. [CrossRef][PubMed] 59. ElAyouti, A.; Weiger, R.; Löst, C. The ability of root ZX apex locator to reduce the frequency of overestimated radiographic working length. J. Endod. 2002, 28, 116–119. [CrossRef][PubMed] Dent. J. 2019, 7, 3 10 of 10

60. Ericson, S.; Finne, K.; Persson, G. Results of apicoectomy of maxillary canines, premolars and molars with special reference to oroantral communication as a prognostic factor. Int. J. Oral Surg. 1974, 3, 386–393. [CrossRef] 61. Nagendrababu, V.; Gutmann, J.L. Factors associated with postobturation pain following single-visit nonsurgical root canal treatment: A systematic review. Quintessence Int. 2017, 48, 193–208. [CrossRef] [PubMed] 62. Gordon, M.P.; Chandler, N.P. Electronic apex locators: A review. Int. Endod. J. 2004, 37, 425–437. [CrossRef] [PubMed] 63. Neelakantan, P. Endodontic Microbiology—A Special Issue of Dentistry Journal. Dent. J. (Basel) 2018, 6, 14. [CrossRef][PubMed] 64. Jung, I.Y.; Yoon, B.H.; Lee, S.J.; Lee, S.J. Comparison of the reliability of “0.5” and “APEX” mark measurements in two frequency-based electronic apex locators. J. Endod. 2011, 37, 49–52. [CrossRef][PubMed] 65. Segato, A.V.K.; Piasecki, L.; Felipe Iparraguirre Nuñovero, M.; da Silva Neto, UX.; Westphalen, V.P.D.; Gambarini, G.; Carneiro, E. The Accuracy of a New Cone-beam Computed Tomographic Software in the Preoperative Working Length Determination Ex Vivo. J. Endod. 2018, 44, 1024–1029. [CrossRef][PubMed] 66. Zand, V.; Rahimi, S.; Davoudi, P.; Afshang, A. Accuracy of Working Length Determination using NovApex and Root-ZX Apex Locators: An in vitro Study. J. Contemp. Dent. Pract. 2017, 18, 383–385. [CrossRef] [PubMed] 67. Shabahang, S.; Goon, W.W.; Gluskin, A.H. An in vivo evaluation of Root ZX electronic apex locator. J. Endod. 1996, 22, 616–618. [CrossRef] 68. Tselnik, M.; Baumgartner, J.C.; Marshall, J.G. An evaluation of root ZX and elements diagnostic apex locators. J. Endod. 2005, 31, 507–509. [CrossRef] 69. Plotino, G.; Grande, N.M.; Brigante, L.; Lesti, B.; Somma, F. Ex vivo accuracy of three electronic apex locators: Root ZX, Elements Diagnostic Unit and Apex Locator and ProPex. Int. Endod. J. 2006, 39, 408–414. [CrossRef] 70. Jenkins, J.A.; Walker, W.A.; Schindler, W.G.; Flores, C.M. An in vitro evaluation of the accuracy of the root ZX in the presence of various irrigants. J. Endod. 2001, 27, 209–211. [CrossRef] 71. Alothmani, O.S. The accuracy of Root ZX electronic apex locator. Saudi Endod. J. 2012, 2, 11530. [CrossRef] 72. Ding, J.; Gutmann, J.L.; Fan, B.; Lu, Y.; Chen, H. Investigation of apex locators and related morphological factors. J. Endod. 2010, 36, 1399–1403. [CrossRef][PubMed] 73. Ebrahim, A.K.; Yoshioka, T.; Kobayashi, C.; Suda, H. The effects of ﬁle size, sodium hypochlorite and blood on the accuracy of Root ZX apex locator in enlarged root canals: An in vitro study. Aust. Dent. J. 2006, 51, 153–157. [CrossRef][PubMed] 74. Haffner, C.; Folwaczny, M.; Galler, K.; Hickel, R. Accuracy of electronic apex locators in comparison to actual length—An in vivo study. J. Dent. 2005, 33, 619–625. [CrossRef][PubMed] 75. Duran-Sindreu, F.; Gomes, S.; Stober, E.; Mercade, M.; Jane, L.; Roig, M. In vivo evaluation of the iPex and Root ZX electronic apex locators using various irrigants. Int. Endod. J. 2013, 46, 769–774. [CrossRef] [PubMed]

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).