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 Table of Contents  
Year : 2021  |  Volume : 33  |  Issue : 2  |  Page : 112-117

Computer-aided design-CAM-guided endodontic microsurgical localization and retrieval of two separated instruments from the periapical area of a mandibular second molar

Department of Conservative Dentistry and Endodontics, AMC Dental College, Ahmedabad, Gujarat, India

Date of Submission26-Apr-2020
Date of Decision03-Nov-2020
Date of Acceptance01-Mar-2021
Date of Web Publication11-Jun-2021

Correspondence Address:
Dr. Akshayraj Langaliya
AMC Dental College, Bhalakhiya Mill Compound, Opp. Anupam Cinema, Ahmedabad - 380 008, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_60_20

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Three-dimensional (3D) imaging devices used for the visualization of anatomic structures not only allow for a more accurate diagnosis but also facilitate precise planning of surgical treatments, such as in guided surgery for instrument retrieval using templates. The innovative template-based treatment methods could also play a crucial role in future modern surgical endodontic treatments, enabling exact preplanning and precision-guided surgical interventions, and resulting in greater accuracy and success rates. We present here a case of a patient with a periapical lesion below a right mandibular second molar, with a fractured file segment extruding beyond the apex in the distal canal, and another instrument half-way extruded from the mesial canal, with radiolucencies evident at the mesial and distal root apices. The patient was treated by employing a 3D-guided microsurgical approach. First, 3D optical scans were imported into a guided surgery program. Periapical lesions and extruded fractured instruments were marked within the software. The osteotomy size, apical resection level, and bevel angle were defined pretreatment. This case introduces a novel-guided microsurgical endodontic technique, incorporating recommended guidelines of modern surgical endodontic treatment with the aid of 3D-printed surgical templates, by which minimally invasive surgical treatment was ensured with preservation of tooth, bone, and surrounding anatomical structures.

Keywords: Endodontic microsurgery, guided microsurgery, three-dimensional printing

How to cite this article:
Langaliya A, Chaudhari E, Patel A, Shah J. Computer-aided design-CAM-guided endodontic microsurgical localization and retrieval of two separated instruments from the periapical area of a mandibular second molar. Endodontology 2021;33:112-7

How to cite this URL:
Langaliya A, Chaudhari E, Patel A, Shah J. Computer-aided design-CAM-guided endodontic microsurgical localization and retrieval of two separated instruments from the periapical area of a mandibular second molar. Endodontology [serial online] 2021 [cited 2021 Oct 18];33:112-7. Available from: https://www.endodontologyonweb.org/text.asp?2021/33/2/112/318138

  Introduction Top

Successful endodontic therapy depends on many factors, one of the most important being canal preparation. Over the decades, a wide array of nickel–titanium rotary instruments have been introduced for shaping root canals. These instruments are subjected to torque and are susceptible to cyclic fatigue, which are the main causes of instrument fracture. Removal of fractured instruments is one of the most difficult operative procedures in endodontics. The orthograde removal of broken instruments, in most cases, is difficult and often hopeless. Nevertheless, an attempt to remove broken instruments should be made in every case.[1]

Occasionally, instruments may be separated apical to the curvature of the canal and in an attempt to bypass or retrieve such fragments, they are in some rare cases pushed beyond the apical foramen. In such cases, a safe access to the site of separation may not be achieved and surgery or extraction will be needed if adverse signs and symptoms occur.

With introduction of recent surgical techniques including endoscopy, sonic-driven microtips, and biocompatible materials, such as Mineral Trioxide Aggregate (MTA) and bioceramics, along with the advent of microsurgical approaches, including the use of a dental operating microscope, microinstruments, ultrasonic tips, and more biologically acceptable root-end filling materials,[2] the success rate of endodontic surgery has been reported to be approximately 90%.[3] The relative risk ratio showed that the probability of success for endodontic microsurgery was 1.58 times that of traditional root-end surgery,[4] which means that endodontic microsurgery has a considerably higher and predictable clinical outcome.

Three-dimensional (3D) imaging techniques add an extra dimension to routinely available preoperative radiographs. Cone-beam computed tomography (CBCT) has been used in endodontics for an effective evaluation of root canal morphology, along with the diagnosis of endodontic pathology, assessment of root and alveolar fractures, analysis of re-absorptive lesions, identification of nonendodontic pathology, and surgical assessment before root-end surgery.[5],[6] If available, CBCT can be used to discern the proximity of the instrument to the mandibular canal.

There are currently three practical ways to apply this technique in a clinical setting: guided surgery using drill guides processed by stereolithographic rapid prototyping,[7],[8],[9] computer-milled templates,[10] or computer navigation systems.[11]

This case report introduces a novel surgical technique, using a virtually planned, 3D-printed surgical template for guided osteotomy preparation of the recipient site, and safe removal of the separated instruments from the periapex of a mandibular second molar. This approach prevented complications, such as iatrogenic damage to the adjacent molar, nerve injury, and trismus.

  Case Report Top

A 19-year-old female patient with a chief complaint of continuous dull aching pain related to her lower right posterior teeth region of 15 days duration was referred to the department of endodontics of our institution. A brief history revealed that the patient had undergone root canal treatment (RCT) in mandibular right second molar (47) 6 months earlier, by a general dental practitioner, but her symptoms persisted. On clinical examination, the second molar had a faulty restoration and was symptomatic, with tenderness on percussion. Periodontal examination revealed mobility and probing depth within normal limits. An intraoral radiograph revealed incomplete endodontic treatment, with a fractured file fragment extruding beyond the apex in the distal canal and a fractured instrument halfway extruded from one of the mesial canals, with a radiolucency encompassing both the mesial and distal root apices [Figure 1]a. With the consent of the patient, a small-volume sectional CBCT scan (CS 9300 scanner, Carestream Inc.; Rochester, NY, USA) was taken of the right mandibular posterior region, with exposure parameters of 80 kV, 8.0 mA, and 90 s. The reconstructed images from the CBCT scan revealed that the periapical radiolucency was 11 mm in diameter and had not perforated the bony cortex [Figure 1]b, [Figure 1]c, [Figure 1]d. The diagnosis was incomplete RCT with a symptomatic periapical abscess resulting from an extruded and separated instrument. After discussing the various treatment options with the patient (extraction/implant or conventional apical surgery), it was decided to treat the tooth with a guided microsurgical approach.
Figure 1: (a) Preoperative radiograph. (b-d) Cone-beam computed tomography images Showing fractured file fragments

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A written consent of the patient was taken regarding the entire procedure and the treatment was initiated. Firstly, a preliminary impression was made using irreversible hydrocolloid, and the diagnostic cast was fabricated using yellow stone. The volumetric data from the CBCT scan was exported as a Digital Imaging and Communications in Medicine (DICOM) file [Figure 2]. The DICOM file was converted into a stereolithography (STL) file using computer-aided design (CAD) software (DDS-PRO, Gdynia, Poland). The STL file was then uploaded and a 3D-printed resin model of the surgical site was fabricated [Figure 3]a. To convey the intended design of the surgical stent to the designer, a “mock-up” of the device was formed in dental wax on the resin model of the surgical site. On the basis of the prepared design and the mandibular DICOM files of the CBCT data, the surgical stent was finally prepared in a software environment using DDS Pro software. After this collaborative, iterative design process, the STL file of the device was printed in an autoclavable resin material, and its fit was confirmed against the anatomical model [Figure 3]b.
Figure 2: (a-e) Three-dimensional planning and preparation of the surgical stent model after conversion of the Digital Imaging and Communications in Medicine cone-beam computed tomography files into stereolithography files using DDS Pro Software (Gdynia, Poland).

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Figure 3: (a and b) Three-dimensional printed models. (c) Full-thickness crestal incision was performed in the keratinized tissue. (d) The surgical template was precisely positioned on tooth #31; guided osteotomy was performed using a 1.5-mm-diameter, surgical round bur adapted from a surgical handpiece. (e) Subsequent incision to create a mucosal window. (f) Placement of probe to verify the position of separated instrument. (g) Custom-made modified IV set suction device with a delivery tip. (h) Microscopic image of extruded instrument from the peri-apex. (i) Complete removal of separated instrument from distal and mesial canals. (j) Radiograph immediately postobturation. (k) Follow-up radiograph after 6 months

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During the initial appointment, the access cavity was reopened, and canals were negotiated very gently with a #15 K file (Mani, Tochigi, Japan) to prevent any further displacement of the fragments. Careful and copious irrigation was performed with 3% sodium hypochlorite using a 30-gauge Max-i-Probe side-vent needle (Dentsply Maillefer, Ballaigues, Switzerland). Intracanal calcium hydroxide dressing RC Cal (Prime Dental Inc, Thane, India) was placed for a week and an interim restoration with Cavit (3M ESPE, Germany) was done following which the patient was then recalled for the surgical appointment.

Surgical protocol

All surgery and postoperative controls were conducted consecutively by a single operator. The patient was draped for maximum asepsis. The perioral skin was disinfected using iodopovidone 10% (Betadine, Meda Pharma, Johannesburg, South Africa) and the patient was asked to rinse with chlorhexidine mouthwash 0.2 wt% (Clohex, Reddy Pharma, Hyderabad, India) for 60 s. All surgical procedures were performed using a surgical operating microscope (OPMI PICO; Carl Zeiss; Göttingen, Germany). Under local anesthesia using 2% lignocaine hydrochloride with 1:80,000 adrenaline (Indoco Remedies, Ltd., Mumbai, India), a full-thickness crestal incision was performed in the keratinized tissue. The mesial relieving incision started about 6-mm inferiorly in the buccal sulcus at a point corresponding to the junction of the anterior two-third and distal one-third of the mandibular first molar [Figure 3]c. The incision was then taken vertically upward to the neck of the second molar, passing around the gingival margin of the posterior one-third of the tooth and continuing cervically along the distal aspect to approximately the midpoint of the tooth. From this point, the incision ran posteriorly and buccally up to the distobuccal line angle of the third molar. On the buccal side, a full-thickness mucoperiosteal flap was elevated.

After the surgical template was precisely positioned on tooth #31, guided osteotomy was performed using a 1.5-mm-diameter, surgical round bur adapted from a surgical rear vent handpiece (Younity BDC Dental Corporation, Guangzhou, China) [Figure 3]d and [Figure 3]e. The surgical template was then removed and the osteotomy was confirmed with an explorer placed and a subsequent radiograph was taken [Figure 3]f. An additional osteotomy was performed using a bone cutter (H161 Lindemann; Brasseler, Savannah, GA, USA) until sufficient space for manipulation of the ultrasonic instruments was gained. Periapical curettage was performed very carefully such that the apex of the distal root along with the extruded floating instrument could be well visualized.

The fractured fragment was safely removed using a custom-made, modified IV set suction device with a delivery tip attached to the high vacuum suction dental unit [Figure 3]g. A deep cut was made using the Lindemann bur, with copious sterile saline irritation, parallel to the long axis, located nearly at the center of the mesial root through the mesial and distal aspect. The cut segment, along with the fractured file that was halfway in the root, was retrieved with a locking tweezer [Figure 3]h. After confirming the removal of the fragments on a periapical radiograph [Figure 3]i, all granulomatous tissues were thoroughly debrided, and endodontic treatment was then performed intraoperatively after providing appropriate hemostasis at the surgical site.

Biomechanical preparation was carried out with ProTaper GOLD (Dentsply Tulsa Dental, Tulsa, OK, USA). Cleaning and shaping were completed for mesiobuccal, mesiolingual, and distal canals, which were enlarged to F2, F2, and F3, respectively. Thereafter, the canals were dried and a master cone corresponding to the final instrumentation size and length of the canal was coated with AH Plus (Dentsply, DeTrey GmbH, Konstanz, Germany) sealer, inserted into the canal, laterally compacted with spreaders, and filled with additional accessory cones. The access preparation was restored with Cavit (3M, Maplewood, MN, USA). Root-end preparation was made 3 mm into the canal space along the long axis, using ProUltra tips (Dentsply). The prepared root-end cavity was dried and filled with Biodentine (Septodont, Saint-Maur-des-Fosses, France) [Figure 3]j. Adaptation of the filling material to the canal was confirmed under the highest magnification of the operating microscope. A mucoperiosteal flap was approximated with multiple interrupted 5-0 silk sutures. An immediate postoperative radiograph was taken to confirm the complete retrieval of the fractured segments.

On recall after surgery, 7 days later, the patient was asymptomatic, and sutures were removed. Postoperatively, clinical and radiographic examinations were performed at 1 month, 6 months, and 1 year [Figure 3]k. A final restoration was provided at the 6-month follow-up. The CBCT image obtained at the 1-year follow-up demonstrated significant healing of the periapical radiolucency, with no clinical signs or symptoms [Figure 4].
Figure 4: (a-c) Posterior–anterior radiograph and cone-beam computed tomography image after 1 year show healing of the periapical lesion

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  Discussion Top

Endodontic surgical failures can mainly be attributed to the inability to eliminate the microscopic cause of disease,[12] limited accessibility, poor visibility in certain regions, such as at the mandibular molars, and anatomical restrictions, such as at the maxillary molars and mandibular premolars. It has also been demonstrated that there was a correlation between the size of the osteotomy and the healing duration,[13] with smaller osteotomies tending to heal faster, based on evidence from radiographic changes. The rate of endodontic surgery success has been improved with the advent of microinstruments, ultrasonic tips, and new biologically acceptable root-end filling materials, i.e., gutta percha and Biodentine™.

Endodontic microsurgery, as it is now called, primarily focuses on atraumatic handling of soft tissue and a minimally-sized osteotomy needed for root-end preparations to promote faster postsurgical healing. Furthermore, 3D imaging technique scan provides more detailed information regarding bone volume, bone quality, or anatomical restrictions. Moreover, development in and access to scanner technology and CAD software have made it easier to use 3D printing technology.

3D imaging devices used in oral and maxillofacial surgery not only allow for a more accurate diagnosis but also precise planning of surgical treatment, as in guided implant surgery, by using templates for implant site preparation and insertion.[14],[15],[16],[17] Such templates were also recently introduced in endodontic therapy for orthograde-guided access cavity preparation and root canal location in calcified canals.[18],[19],[20],[21] Such surgical templates have also been used in autotransplantation for guided osteotomy preparation[22] and donor tooth placement and for designing trephine burs to achieve single-step osteotomy, root-end resection, and biopsy in complex cases.[23] 3D planning for prefabricating the template is comparatively costly and time consuming. However, the preservation of the cortical bone and dental structures, as recommended in the guidelines for state-of-the-art endodontic surgery, could be credited as potential benefits and may justify additional planning time and cost.[2],[24]

In the present case, two broken fragments were present: one was floating in the periapical area and the other was partially protruding out of the apical region of the mesial root, making this an obvious and unique case to opt for guided microsurgery. Furthermore, the proximity of the inferior alveolar nerve to the mandibular second molar, due to the upward curve in the mandibular canal, makes the use of a surgical guide even more appropriate. In addition, after osteotomy, a novel technique involving the use of an IV set suction device with a delivery tip was implemented since one of the fragments was already present in the periapical area. To prevent accidental slippage of this fragment to other regions, this device was used to remove the fragment with ease. To prevent any untoward manipulation of the broken fragments due to instrumentation, irrigation, or obturation, an intraoperative RCT was performed. Although Biodentine does not present any dramatic radiographic appearance, it was preferred to MTA as a retrofilling material due to the ease of manipulation and placement in this critical area.

All previously reported attempts to prepare guides have been based on dental models, although the precise guides are those prepared on the basis of CBCT images. The only disadvantage of the osteotomy bone guide is the stabilization of the guide in the posterior mandibular area due to surrounding structures, i.e., the cheek, tongue, surrounding musculature, and the elevated flap. Therefore, in this case, a two-piece osteotomy bone guide was fabricated, which was then stabilized firmly by industrial-grade glue and was subsequently checked on the dental model that had been previously prepared.

  Conclusion Top

Within the limitation of this case report, the outcome of this novel microguided surgical approach appears to be encouraging. Conducting guided osteotomy, apex localization, and root-end resection was executed for retrograde retrieval of separated instrument fragments, with adequate consideration of the advocated guidelines for modern surgical endodontic treatment. Such an approach has not been reported previously. Nevertheless, to confirm the reliability of this procedure, further studies with long-term follow-up should be conducted.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.


The authors would like to thank Dr Anjali Kothari and Dr Neeta Patel for their constant support and valuable inputs.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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Di Giacomo GA, Cury PR, de Araujo NS, Sendyk WR, Sendyk CL. Clinical application of stereolithographic surgical guides for implant placement: Preliminary results. J Periodontol 2005;76:503-7.  Back to cited text no. 5
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]


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