Descripción de la morfología del sistema de canales radiculares del primer molar maxilar mediante tomografía computarizada cone-beam en una población chilena / Description of the morphology of the root canal system of the maxillary first molar using cone-beam computed tomography in a Chilean population

Describir la morfología del sistema de canales radiculares del primer molar maxilar en una población chilena mediante exámenes de tomografía computarizada Cone-Beam (CBCT). Se realizó un estudio observacional descriptivo en el cual se utilizaron los exámenes CBCT de pacientes que fueron atendidos en un Centro de Radiología Maxilofacial privado durante el período comprendido entre Enero y Diciembre del año 2018 en la ciudad de Temuco, Chile, los cuales fueron observados de manera independiente por dos investigadores previamente calibrados. Se observaron 199 exámenes CBCT. En la raíz mesiobucal,predominaron las morfologías tipo II, I y IV de Vertucci respectivamente, mientras que en la raíz distobucal y palatina predominó la morfología tipo I. El canal MB2 estuvo presente en el 62,3 % de los casos, con una prevalencia significativamente mayor en pacientes jóvenes. En la mayoría de los primeros molares maxilares de los habitantes de la ciudad de Temuco se observaron tres raíces separadas y la presencia de cuatro canales. Se determinó una alta frecuencia del canal MB2 en la raíz MB.

SUMMARY: The objective of this study was to describe the morphology of the root canal system of the maxillary first molar in a Chilean population through Cone-Beam computed tomography (CBCT) examinations. A descriptive observational study was carried out in which the CBCT examinations of patients who were treated in a private maxillofacial radiology center during the period between January and December 2018 in Temuco, Chile, were used which were observed independently by two previously calibrated researchers. In this analysis 199 CBCT exams were observed. In the mesiobuccal root, Type II, I and IV morphologies predominated respectively, while in the distobuccal and palatal root, Type I morphology predominated. The MB2 canal was present in 62.3 % of cases, with a higher prevalence in young patients. Three separate roots and the presence of four canals were observed in most of the maxillary first molars of the patients in Temuco. A high frequency of the MB2 canal was determined in the root MB.

CBCT study on the safe location of palatal microscrew implant anchorage nail between maxillary first and second molars / 口腔疾病防治

Objective@#Conebeam CT (CBCT) was used to measure the palatine between the maxillary first and second molars. The proximal and distal palatal widths of the maxillary first and second molar and the palatal mucosal thickness and bone tissue thickness when microscrew implant anchorage nail were implanted at different angles provided a reference for the clinical selection of microscrew implant placement.@* Methods@#The image data of 90 adult patients were selected as the research object, and the jaw bone was reconstructed by scanning. In maxillary palatine, selection of distances at 12 mm, 14 mm, 16 mm, and 18 mm from the palatal apex of maxillary first molar between the maxillary first and second molar were used as measurement, measured the proximal and distal palatal widths of maxillary first and second molar and the palatal mucosal thickness and bone tissue thickness when microscrew implant anchorage nails were implanted at 30 °, 45 °, 60 °, and 90 °. SPSS 26.0 software was used for one-way ANOVA and LSD pair comparison. @*Results@#The larger the angle of the microscrew implant anchorage nail was, the smaller the proximal and distal medial widths between the maxillary first and second molar, and the difference was statistically significant (P < 0.05). Compared with the 90° direction, the proximal and distal medial widths of the microscrew implant anchorage nail were larger in the 60° direction. The greater the angle of implantation, the smaller the mucosal thickness and the greater the bone tissue thickness, and the results showed a significant difference (P < 0.001). Compared with the direction of 30° and 45°, the mucosal thickness at the direction of 60° was smaller, and the bone tissue thickness was larger. The higher the position of the microscrew implant anchorage nail, the greater the width of the proximal and distal medial, and the difference was statistically significant (P < 0.05). Compared with the positions 12 and 14 mm from the palatal tip, the proximal and distal medial widths of the microscrew implant anchorage nail were larger. The higher the implant position was, the greater the mucosal thickness and the smaller the bone tissue thickness. The results showed a significant difference (P < 0.001). Compared with the position of 18 mm from the palatal tip of the maxillary first molar, the mucosal thickness was smaller and the bone tissue thickness was larger.@*Conclusion@#It is most appropriate to implant microscrew implant anchorage nail at least 10 mm in length in the direction of 60° at the palatal apex 16 mm from the maxillary first molar in palatine between the first and second molar.

Comparison of diagnosing the relationship between the root of maxillary posterior tooth and maxillary sinus between panoramic radiography and cone beam computer tomography / 口腔疾病防治

Objective@#To study the diagnostic accuracy and the distance between the root of maxillary posterior tooth and the maxillary sinus using panoramic radiography and cone beam computer tomography; to provide basic information for clinicians to treat diseases in the maxillary posterior region. @* Methods@#Eighty patients were included in this study. A total of 671 specimens were measured for the distance between the root tip and the maxillary sinus floor in both imaging modalities.@*Results @#The roots that did not contact the sinus floor or contacted but did not project into the sinus cavity showed an agreement of 82% and 70% when using panoramic radiography. Forty-eight percent of the roots that projected into the sinus cavity in panoramic radiography showed protrusion into the sinus with cone beam computer tomography (CBCT). For panoramic radiography and CBCT showing root projections into the sinus cavity, the average distances were 2.19 ± 1.82 mm and 1.47 ± 1.01 mm, respectively. There was a significant difference between the two values (P ＜ 0.05).@*Conclusion@# Panoramic radiography is more accurate when roots of maxillary posterior teeth do not contact the sinus floor or contact it. However, it has a lower accuracy rate when the tooth roots protrude into the sinus.

Clinical analysis on the root fracture of the maxillary first molar / 华西口腔医学杂志

OBJECTIVES@#This study aimed to investigate the common types and directions of root fractures of the maxillary first molar and the influence of root canal treatment on the prevalent sites of root fractures.@*METHODS@#A total of 274 maxillary first molars with root fractures diagnosed via cone beam computed tomography were included. The root fractures of nonendodontically and endodontically treated teeth were identified to be spontaneous and secondary root fractures, respectively. The sites, types, and directions of spontaneous and secondary root fractures were determined.@*RESULTS@#Among the spontaneous root fractures, the proportion of palatal root fractures (56.1%) was higher than those of mesial buccal root fractures (36.1%) and distal buccal root fractures (7.8%). Among the secondary root fractures, the proportion of mesial buccal root fractures (52.7%) was higher than those of palatal root fractures (36.5%) and distal buccal root fractures (10.8%). The distribution of predominant fracture sites was statistically significant (@*CONCLUSIONS@#This study provided an epidemiological basis for the clinical features of root fractures of the maxillary first molar. During the dia-gnosis and treatment of the maxillary first molar, the possibility of palatal root fractures should be considered. The occurrence of mesial buccal root fractures may be related to root canal treatment. Therefore, the risk of mesial buccal root fractures caused by iatrogenic factors should be minimized.

Endodontic management of maxillary first molar with an anatomical variation of two palatal canals: A case report

An in-depth knowledge of the root canal anatomy is important for any successful root canal treatment; however, complexities exist within the root canal morphology. The maxillary first molar has variations in its root morphology and canal configurations. In literature, this variation is only observed in an estimated 1.12%-1.17%. One such case is described in this case report which provides the endodontic management of a left maxillary first molar with two palatal canals using loupes magnification.

Effect of Developmental Disorders of Maxillary First Molars on Orofacial Morphology / 대한소아치과학회지

This study was aimed to evaluate orofacial morphologies on the cases of developmental disorders of maxillary first molars.Panoramic radiographs, lateral cephalographs, and clinical photos of 2983 children who attended the Pediatric Dental Clinic of Pusan National University Dental Hospital from 2006 to August 2017 were assessed retrospectively. 34 patients were selected whose maxillary first molars were missed or developmentally delayed unilaterally or bilaterally. Demirjian' s method was used for estimating dental age, then which was compared to chronologic age of children. Parameters expressing skeletal and dentoalveolar disharmony were checked and compared with control. Additionally, occlusion relationship was evaluated.Maxillary dental age was significantly delayed compared to chronologic age. Several parameters which show skeletal open-bite tendency and skeletal class III malocclusion with maxillary retrusion were statistically significant. Anterior crossbite and edge-bite were expected in most of these cases, but compensation by occlusion and soft tissue was also verified which might mask skeletal class III tendency.Congenital missed or developmentally delayed maxillary first molars might be related with declined growth of maxilla. If developmental disorders of maxillary first molars were verified during clinical examination, careful monitoring of orofacial growth was necessary during puberty and timed orthopedic and orthodontic intervention were considered.

Evaluation of complex mesiobuccal root anatomy in maxillary first molar teeth / Evaluación de la anatomía de la raíz mesiobucal compleja en los primeros dientes molares maxilares

The objective of this study was to investigate the complex anatomy of mesiobuccal roots, supporting and complementing commonly applied clearing technique, using access cavity modification and the pulpal groove deepening method. Three hundred and ninety eight extracted intact human maxillary first molars were included in this study. Firstly, modified rhomboidal shape access cavities were prepared then, the developmental groove between the mesiobuccal and the palatal canals was deepened 1 mm with a round slow speed bur. Indian ink was injected into both the canal orifices of mesiobuccal roots and into the groove between mesiobuccal and palatal canals, using a 22 gauge syringe. Then the clearing technique was applied. The incidence of one canal was 30.90 %, two canals was 62.07 %, three canals was 7.03 %. In twenty five (6.28 %) of the mesiobuccal roots, 8 root canal types, which are not included in Vertucci's classification, were seen. All these root canal types had three root canals. The establishment of adequate access and deepening of the pulp chamber floor increased the probability of locating the third canal in the mesiobuccal root of maxillary first molars.

El objetivo de este estudio fue investigar la compleja anatomía de las raíces mesiovestibulares, apoyando y complementando la técnica de limpieza aplicada comúnmente, usando la modificación de la cavidad de acceso y el método de profundización del surco pulpar. En este estudio se incluyeron 398 primeros molares maxilares, extraídos intactos. Se prepararon las cavidades de acceso con la forma romboidal modificada, el surco de desarrollo entre los conductos mesiovestibular y palatino se profundizó 1 mm con una fresa redonda de velocidad lenta. Se inyectó tinta china en los forámenes del canal de las raíces mesiovestibulares y en el surco entre los conductos mesiovestibular y palatino utilizando una jeringa de calibre 22. Luego se aplicó la técnica de limpieza. La incidencia de un canal fue del 30,90 %, dos canales del 62,07 % y tres canales del 7,03 %. En 25 casos (6,28 %) de las raíces mesiobucales, se observaron 8 tipos de conductos radiculares, que no están incluidos en la clasificación de Vertucci. Todos estos tipos de conductos tenían tres conductos radiculares. La determinación de un acceso adecuado y la profundización del piso de la cámara de pulpa aumentó la probabilidad de localizar el tercer canal en la raíz mesiovestibular de los primeros molares superiores.

Maxillary first molar with a single buccal root / 实用口腔医学杂志

Maxillary first molar demonstrates considerable anatomic complexities and abnormalities with respect to the number of roots and root canals. The occurrence of maxillary first molar with a single buccal root is rarely reported in literature. This is a case report of maxillary first molar with a single buccal root and a palatal root,each of which has one canal.

A maxillary first molar with two palatal roots and an accessory canal diagnosed by CBCT / 实用口腔医学杂志

A maxillary first molar with 2 distinct palatal roots and an accessory canal was diagnosed by CBCT and microscope.An enamel protuberance at the cervical area was found.A properly usage of CBCT and microscope is helpful for the diagnosis and treatment of tooth with complex root canal system.

Prevalence of Unclassified Root Canal Configuration in Permanent Maxillary First Molar in Indian Population.

Background: If a canal is left untreated, it is a foci of infection. Therefore, it is critical to know the usual configuration of the root canal along with the variations in root canal anatomy, in order to keep the cause of endodontic failure to a minimum. Aim: This study investigated the canal configuration in maxillary first permanent molar mesiobuccal root radiographically followed by histological evaluation in Indian population. Methods: Endodontic access preparation was performed on 100 human permanent maxillary Ist molars and all the canals were explored. The mesiobuccal root was separated and radiographed in mesiodistal and buccolingual direction. India ink dye was injected actively in the root canal of each sample. The root samples were prepared for histological viewing. The slides made were observed under light microscope and canal configurations were tabulated. Results: The radiographic interpretations by observers were correlated with histological findings and analyzed statistically (p value). The radiographic findings revealed a good inter observer agreement (Cohen kappa). On matching histological and radiographic interpretations, it revealed 69.2% Vertucci type I predominance. New unclassified canal configurations were also observed. Conclusion: To divulge three dimensional architecture of the root canal, application of alone conventional radiography is not enough.

Evaluación de la frecuencia, ubicación y tipos de itsmos en raíces mesiobucales de primeros molares maxilares: un estudio ex vivo / Evaluation of Isthmus frequency, location, and types in mesiobuccal roots of first maxillary molars: an ex vivo study

El objetivo fue describir la configuración interna del sistema canalicular de la raíz mesiobucal (MB) del primer molar maxilar, identificando el número de canales junto a la frecuencia, ubicación y tipos de itsmo a 1, 3 y 5 mm del ápice. Esta investigación fue aprobado por el comité de ética. Se realizó un estudio descriptivo ex vivo de corte transversal. Molares extraídos fueron limpiados, desinfectados y fijados en formalina al 10 %. Se identificó la raíz MB y se obtuvieron cortes transversales (3) a 1, 3 y 5 mm desde apical a coronal, identificadas como secciones A, B y C. Ciento cincuenta secciones fueron teñidas con azul de metileno y observadas bajo microscopio óptico, tanto en la superficie apical como coronal, y analizadas mediante el programa ImageJ. Se obtuvieron estadísticas descriptivas (media ± DE), y mediante las prueba ANOVA y chi-cuadrado de Pearson se compararon las secciones a diferentes niveles. Se observaron un total de 445 canales radiculares, 289 correspondieron a canales accesorios. El 41,6 % fueron canales mesiobucales secundarios (MB2) y 5,1 % un tercer canal accesorio. Se observaron con mayor frecuencia istmos Tipo I (48), seguidos de Tipo IV (26); los Tipos II, III y V no superaron el 15 %. De acuerdo con la prueba de chi-cuadrado de Pearson, existen diferencias significativas entre los tipos istmos y distancia del ápice (p> 0,001). La incidencia del Tipo I fue mayor cerca del ápice, con un descenso hacia los 3,0 mm. Se observó una compleja morfología del sistema canalicular apical en la raíz MB, que explica su baja tasa de éxito cuando son tratados con endodoncia. Las variaciones anatómicas, tales como MB2 o más canales accesorios e istmos deben ser considerados en la planificación y realización del tratamiento de endodoncia convencional o cirugía apical, con el fin de lograr procedimientos más exitosos. Se recomienda que las apicectomías se extiendan por lo menos a 3,3 mm del ápice.

The aim was to describe the internal configuration of the canalicular system of the mesiobuccal root (MB) of the maxillary first permanent molar, identifying the number of canals and isthmus frequency, location, and types at 1, 3 and 5 mm from the apex. This research was approved by the ethics committee. A descriptive ex vivo cross-sectional study was conducted. Extracted molars were cleaned, disinfected and fixed in 10% buffered formalin. The non-instrumented MB root was identified and 3 cross sections at 1, 3 and 5 mm from apical to coronal identified as A, B and C were obtained. 150 sections were stained with methylene blue and observed under microscope, in both apical and coronal surface using the ImageJ program. Descriptive statistics (Mean±SD) was obtained, and ANOVA and Pearson chi-square tests were used to compare the sections at different levels. A total of 445 root canals were observed, 289 corresponded to accessory canals. 41.6% were secondary mesiobuccal canal (MB2) and 5.1% a third accessory canal. The isthmus observed were Type I (48), followed by Type IV (26); Types II, III and V did not exceed 15%. According to the Pearson chi-square test, there are significant differences between the isthmus types and distance of the apex (p> 0.001). The incidence of Type I was greater near the apex, with a decline towards 3.0 mm. A complex morphology of the apical maxillary MB root system was found, and explains their low success rate when treated endodontically. Anatomical variations such as MB2, accessory canals and isthmus should be considered when planning and conducting endodontic treatment or apical surgery, in order to achieve more successful procedures. It is recommended that apicectomies extend at least 3.3 mm from the apex.

Maxillary first molar with two distobuccal root canals: a case report / 华西口腔医学杂志

The root and canal anatomy of maxillary first molar is very complicated. The incidence of having two canals in the mesiobuccal root of maxillary first molar is higher than that in its distobuccal root. This article described a maxillary first molar with five root canals, including two canals in mesiobuccal and distobuccal roots.

Radix mesiolingualis and radix distolingualis: a case report of a tooth with an unusual morphology

Variation in the root and canal morphology of the maxillary first molars is quite common. The most common configuration is 3 roots and 3 or 4 canals. Nonetheless, other possibilities still exist. The presence of an additional palatal root is rather uncommon and has been reported to have an incidence of 0.06 - 1.6% in varying populations studied. Whenever two palatal roots exist, one of them is the normal palatal root, the other is a supernumerary structure which can be located either mesiolingually (radix mesiolingualis) or distolingually (radix distolingualis). This case report describes successful endodontic treatment of a maxillary first molar with radix mesiolingualis and radix distolingualis. Identification of this variation was done through clinical examination along with the aid of multiangled radiographs, and an accurate assessment of this morphology was made with the help of a cone-beam computed tomography imaging. In addition to the literature review, this article also discusses the epidemiology, classifications, morphometric features, guidelines for diagnosis, and endodontic management of a maxillary first molar with extra-palatal root.

Finite element analysis of the prosthodontic design for maxillary first molar mesio-lingual cusp defect with subfissue / 实用口腔医学杂志

Objective:To study the prosthodontic design for the treatment of maxillary first molar mesio-lingual cusp defect with subfis-sue.Methods:A finite element model of maxillary first model,including mesio-lingual cusp defect with subfissue,periodontal support-ing tissue and a section of the maxilla was established by cone beam CT.Different prosthodontic designs for respective restoration and simulating different bite force were adopted,the Von Mises stress,maximum compressive stress and the crack distribution,J integral and the root displacement were analysed.Results:In the metal pile restoration model,the stress,JINT value and the equivalent stress and displacement of root were the smallest.With the increase of crack depth of the vertical and oblique fissue,the equivalent levels of stress (equivalent stress of J integral),the stress experienced by the dentin along with the peak of the maximum principal,increased signifi-cantly.Under 4 kinds of force direction and 3 repair methods,the equivalent stress peak value,J integral dentin stress,maximum prin-cipal stress peak value and dentin stress peak value of the cracks was 200 N,90°>200 N,45°>600 N,0°>200 N.Conclusion:High elastic modulus and all ceramic crown may lead to minimal equivalent stress,J integral,dentin equivalent stress and maximum principal stress.When subfissure is repaired,teeth fracture remains possible and any possible propagation may exist.The effect of later-al force on the crack and the dentin is greater than that of vertical force for crack expansion and tooth fracture.

Dos conductos en la raíz distovestibular del primer molar maxilar: revisión bibliográfica y reporte de caso clínico / Maxillary first molar with two canals in the distobuccal root: a review of the literature and report of a clinical case

La incidencia de dos conductos en la raíz distovestibular en un primer molar maxilar es una variación anatómica poco frecuente del sistema de conductos. Los investigadores han demostrado múltiples forámenes, conductos adicionales, furcaciones, deltas, conexiones entre conductos, conductos en forma de C y conductos accesorios. Este reporte de caso clínico presenta el tratamiento de un primer molar maxilar con dos conductos en la raíz ovestibular. Se muestra clínicamente la presencia dedos conductos distovestibulares tipo 2-1, los cuales se instrumentaron manualmente con técnica corono- apical con limas K-Flexofi le de 25 mm y se obturaron con la técnica de condensación lateral, con conos de gutapercha, conos accesorios número FF, F y cemento Sealapex. Después del tratamiento se selló el diente con cemento temporal y se refirió para realizar la restauración defi nitiva...

The presence of two canals in the distobuccal root of a maxillary fi rst molar is a rare anatomical variation of the canal systems. Investigators have shown multiple foramina, additional canals, furcations, deltas, intercanal connections, C-shaped canals, and accessory canals. This clinical case reports the clinical treatment of a maxillary fi rst molar with two canals in the distobuccal root. We present a clinical case involving the presence of the two 2-1-type distobuccal canals. Manual instrumentation was performed using the crown-down technique with the aid of 25 mm K-fl exofi le fi les. The canals were fi lled using the lateral condensation technique and gutta-percha cones, FF and F accessory cones, and Sealapex cement. Following the treatment, the tooth was sealed with temporary cement and the patient was referred for fi nal restoration. The aim of this paper is to examine the anatomical variations that can occur in the root canal system and the technologies that can be used to correctly identify the location of additional canals.

Maxillary first molar with seven root canals diagnosed with cone‑beam computed tomography scanning.

Nonsurgical endodontic therapy of a right maxillary first molar with three roots and seven root canals. This unusual morphology was diagnosed using a dental operating microscope (DOM) and confirmed with the help of cone‑beam computed tomography (CBCT) images. CBCT axial images showed that both the palatal and distobuccal root have a Vertucci type II canal pattern, whereas the mesiobuccal root showed a Sert and Bayirli type XVIII canal configuration. The use of a DOM and CBCT imaging in endodontically challenging cases can facilitate a better understanding of the complex root canal anatomy, which ultimately enables the clinician to explore the root canal system and clean, shape, and obturate it more efficiently.

Demystifying the mesiobuccal root of maxillary first molar using cone‑beam computed tomography.

Context: Imaging techniques and endodontics are inseparable from each other as the former have always been the cornerstone for successful endodontic diagnosis and treatment. Aims: The objective of this study was to detect the presence of extra canals in the mesiobuccal root of the maxillary first molar using cone‑beam computed tomography (CBCT). Materials and Methods: In this study, 75 freshly extracted human maxillary first molars were mounted on arches and exposed to CBCT and digital radiography (control). The incidence of additional canals is then evaluated using CBCT and the teeth identified with additional canals were marked and again exposed to RVG. Statistical Analysis Used: The results were analyzed by three examiners two endodontists and an oral radiologist to eliminate bias. Inter and intra rater agreement was analyzed using the kappa coefficient. Results: Statistical analysis revealed the incidence of extra canals to be at 47.1% with the difference between the readings of the 3 examiners being statistically insignificant. Conclusions: CBCT can be considered an advanced diagnostic tool for primary and secondary endodontic treatments.

Endodontic management of a maxillary first molar with three roots and seven root canals with the aid of cone-beam computed tomography

Variation in root canal morphology, especially in maxillary first molar presents a constant challenge for a clinician in their detection and management. This case report describes the successful root canal treatment of a three rooted right maxillary first molar presenting with three canals each in the mesiobuccal and distobuccal roots and one canal in the palatal root. The clinical detection of this morphologic aberration was made using a dental operating microscope, and the canal configuration was established after correlating and computing the clinical, radiographic and cone-beam computed tomography (CBCT) scan findings. CBCT images confirmed the configuration of the canals in the mesiobuccal and distobuccal roots to be Al-Qudah and Awawdeh type (3-2) and type (3-2-1), respectively, whereas the palatal root had a Vertucci type I canal pattern. This report reaffirms the importance of careful examination of the floor of the pulp chamber with a dental operating microscope and the use of multiangled preoperative radiographs along with advanced diagnostic aids such as CBCT in identification and successful management of aberrant canal morphologies.

The morphology of maxillary first molars and root canals in Uyghur adults examined by cone-beam com-puted tomography / 实用口腔医学杂志

Objective:To analyze the morphological characteristics of maxillary first molars,mesiobuccal roots and the incidence of second mesiobuccal(MB2)roots in Uyghur adults.Methods:1 00 Uyghur adults with full dentition were included.The morphology of maxillary first molars and root canals were examined by cone beam computerized tomography(CBCT).The prevalence of MB2 and the difference between sexes were analysed.Results:Among 200 maxillary first molars,1 54(77%)teeth were with 3 roots and 3 ca-nals,42(21 %)with 3 roots and 4 canals,2(1 %)with 3 roots and 5 canals,1 (0.5%)was with 4 roots and 6 canal,1 (0.05%) with 4 roots and 7 canal.The percentage of type Ⅰ,Ⅱ,Ⅲ,Ⅳ and Ⅴ mesiobuccal roots was 77.0,1 3.5,9.0,0 and 0.5 respec-tively.The prevalence of MB2 was 22.32% in male and 21 .2% in female(P =0.901 ).Conclusion:The prevalence of MB2 in Uy-ghur adults is about 22% and the predominant morphology of maxillary first molarsmesiobuccal roots was type I.

Location of three canals in the mesiobuccal root of the maxillary first molar

Introduction:The knowledge on the complex anatomy of the maxillary first molar and location of extra canals are essential for diagnosis and endodontic treatment success. Objective:The purpose of this study was to report a clinical case showing a varied number of root canals in maxillary molars with the aid of the operating microscope (OM). Case report: The endodontic retreatment of the right maxillary first molar with unusual anatomical variation was performed, displaying three canals in the mesiobuccal root (MB), a root canal in the distobuccal root (DV) and a root canal in the palatal root (P). To remove the resin core inside pulp chamber with and without the aid of dental operating microscope, a high-speed drill and ultrasonic tip (diamond round) was used, respectively, for the refinement of the pulp chamber walls. The dental operating microscopewas used during the access surgery, location, negotiation of canals and checking of the completion of all stages of the retreatment. Subsequently, the cleaning, shaping and filling of the root canal system was completed. The presence of three canals in the mesiobuccal root, one in the distobuccal root and one in the palatal root was found. Conclusion: Variations in the number of canals could be confirmed during the surgery access in endodontic retreatment cases with the aid of dental operating microscope.