A Novel Method for Periapical Microsurgery With the Aid of 3D Technology

A Case Report

Shangzhu Ye; Shiyong Zhao; Weidong Wang; Qianzhou Jiang; Xuechao Yang


BMC Oral Health. 2018;18(85) 

In This Article

Case Presentation

A 37-year-old female patient presented with discomfort in the left maxillary lateral incisor. Clinical examination revealed that the left maxillary lateral incisor and canine were slightly tender to percussion. Pulp vitality test showed a negative response to temperature for both teeth. Radiograph showed a large periapical radiolucency around both teeth. The patient was clinically diagnosed with chronic periapical periodontitis. Considering the large size of the periapical lesion and it was a suspected periapical cyst, we decided to treat the patient with a microsurgical endodontic surgery for biopsy and to remove the root-ends at the same time to eliminate contamination. No contraindications were found. The patient had no significant medical history and was in good medical status.

After obtaining the patient's informed consent about the surgery procedure and the possible prognosis of the outcome, a small volume CBCT scan (iCAT 17–19, Imaging Sciences International, Hatfield, PA, USA) was taken to obtain a more detailed view of the periapical area, to determine the accurate size of the lesion and the exact location of root apices, to evaluate the proximity of adjacent anatomical structures and to design a template. A well-defined radiolucent lesion with an approximate size of 13 mm*9 mm*9 mm at the apices of the upper left lateral incisor and canine was observed on CBCT (Figure 1). An endodontic specialist treated her with an appropriate root canal therapy before the surgery.

Figure 1.

a, b Sagittal CBCT images of the left maxillary lateral incisor and canine showed lesions in periradicular regions. c An oblique coronal CBCT image revealed that the teeth shared one elliptic lesion with an approximate size of 13 mm*9 mm*9 mm. The red arrow indicates the location of the lesion

The acquired Digital Imaging and Communications in Medicine (DICOM) files from the CBCT images were uploaded into a software (Simplant, Leuven Belgium) for virtual surgical planning. A digital impression was acquired with an intra-oral scanner (3Shape, Denmark) and uploaded into the same software. Both the CBCT and the surface scan were matched based on radiographically visible teeth. A template was virtually designed to locate the lesion area and the root apex of the teeth precisely (Figure 2a and Figure 2b). The thickness of labial cortical bone was gauged using a virtual measure tool provided by the software and recorded as working depth I. The straight distance from the surface of the labial cortical bone to the palatal side of the root-end requiring resection was also gauged and recorded as working depth II. The distance from the palatal side of the root-end to the labial side of the palatal alveolar bone was also gauged and recorded as safe depth to prevent the trephine from entering too deeply into the bone and causing unnecessary damage to the palatal alveolar bone (Figure 2c and Figure 2d). During the surgery, the thickness of the template (2.0 mm) and the space reserved for soft tissue (0.5 mm) was added to the working depth I and II to obtain total working depth I and II.

Figure 2.

a A 3 mm root-end for resection was marked by a simulated virtual trephine with a diameter of 4 mm on an oblique coronal section of the left maxillary lateral incisor and canine. The root-ends of the left maxillary central incisor and first premolar were safe from accidental damage. b A horizontal section indicated the location of root-ends for both teeth and the root-ends were marked by the simulated virtual trephine. c Based on a sagittal section of the left maxillary lateral incisor, we learned that a working depth of 4.57 mm would be sufficient for the trephine to remove the root-end completely. This depth was still 2.69 mm away from the palatal cortical bone, which we regarded as a safe depth. d For the left maxillary canine, the working depth was 4.87 mm, and the safe depth was 2.19 mm. All lengths were measured using a tool provided by the software. e Three-dimensional reconstruction of the scans obtained from CBCT and surface scans were matched to reconstruct the operating site. f The locations of the root-ends of the left maxillary lateral incisor and canine were marked out on the reconstruction image. g The template was designed to be supported by teeth from the left maxillary central incisor to the left maxillary first premolar. The lesion area was located, and the outline was confirmed. h The template was designed to be 2 mm thick after considering the flexural strength of the resin composite. A 0.5 mm space from the labial cortical plate to the template was preserved to accommodate soft tissues

To guide and accommodate a trephine (Meisinger, Germany) with an external diameter of 4.0 mm, the round hollow part aimed to locate the root-end was designed with a diameter of 4.2 mm, which was enough to hold the trephine but not so large as to destroy accuracy. To preserve more root length and avoid exposing more dentinal tubules, the track guiding the trephine was designed to be perpendicular to the long axis of the root. The other hollow part lying in the middle followed the outline of the lesion, locating the whole part of the lesion precisely (Figure 2e, Figure 2f, Figure 2g and Figure 2h). The virtual template was exported as a stereolithography (STL) file and was fabricated using a 3D printer (3510SD, 3D system Corporation, Rock Hills, SC, USA) (Figure 3a).

Figure 3.

a The template was fabricated exactly as designed with an equivalent thickness. b The disinfected template was positioned on the real teeth and checked. c A full-thickness marginal flap was prepared with a primary incision in the gingival sulcus and the relieving incision as vertical as possible to avoid severing supra-periosteal vessels and collagen fibres. d The reflection of the flap and the exposure of the lesion. e Sling suture to the buccal mucosa. f The template was placed in position and checked

After fabrication, the template was positioned on the patient's plaster cast, and its correct and reproducible fitting was checked. It was then detached and soaked in disinfectant for use. Another fitness check was performed on the real teeth of the patient before surgery (Figure 3b).

After disinfection of the skin and mucosa, primacaine was delivered into the loose connective tissue of the alveolar mucosa near the root apices for local anaesthesia. A rectangular, full-thickness flap design was chosen in this case (Figure 3c). The mucoperiosteum was reflected, and the labial alveolar plate was exposed where a semi-lunar perforation was observed (Figure 3d). We sutured the flap to the labial mucosa (Figure 3e).

The template was positioned on the teeth and was checked again for stability, a clear operating vision and a straight access to the cortical bone (Figure 3f). The trephine was laid inside the pre-designed track and was slowly and carefully pushed in with the guidance of the template with constant sterile saline flushing (Figure 4a). The trephine was removed when it reached total working depth I which was pre-gauged on the CBCT images, leaving an annular notch (Figure 4b). The template was detached to inspect the operating site (Figure 4c). The annular cortical bone was gently removed to expose the pathological tissues. The left maxillary lateral incisor and canine were both operated on in the same way, but the total working depth was different in each case. Other soft pathological tissues between the two root-ends were easily removed with suitable sizes of sharp surgical bone curettes (Figure 4d). The removed pathological tissues were sent for histopathological examination. The template was positioned again after the removal of pathological tissues. The trephine was laid inside and when it reached total working depth II, a sense of dropping was felt through the trephine just as the root-end was separated entirely from the tooth, forming a cutting bevel at the resected root-end perpendicular to the long axis of the canal.

Figure 4.

a The trephine was positioned. b After the trephine reached total working depth I and was removed, the annular notches were observed. c The template was removed and the operating site was inspected. d The pathological tissues were removed for biopsy

Root-end cavity preparation was carried out using an angled micro-surgical ultrasonic tip under a microscope. The root-end cavity was prepared, cleaned and dried. Mineral trioxide aggregate (MTA) was filled into the cavity (Figure 5a and Figure 5b). Considering the large size of the lesion (Figure 5c), a guided tissue regeneration (GTR) procedure was adopted for better healing. It was carried out using xenogeneic bone (Geistlich Bio-Oss, Switzerland) and collagen membrane (Geistlich Bio-Gide, Switzerland; Figure 5d and Figure 5e). The flap was gently eased back and sutured (Figure 5f). Pressure was applied for ten minutes after suturing. Biopsy findings were periapical granuloma (Figure 6a and Figure 6b).

Figure 5.

a, b Micro-surgical mirror was used to examine the cut root surface after the MTA was delivered into the root-end. Completed MTA root-end filling was obtained. c After removal and cleaning of soft pathological tissue, the lesion size was large and required a GTR procedure for better prognosis. d, e Bio-Oss and Bio-Guide were used in this case. f The flap was sutured back

Figure 6.

Histopathologic examination revealed the presence of (a) eosinophils (red arrows), foam cells (black arrows) and areas of hemosiderin pigmentation (green arrows; H&E, 40×); b plasma cell (red arrow) and many lymphocytes (black arrows; H&E, 40×). The features were consistent with periapical granuloma

The patient was reviewed 7 days later to remove stitches. The operating site was healing well, and no unusual symptoms or postoperative discomforts were reported by the patient (Figure 7a and Figure 7b).

Figure 7.

a A 7-day review to remove the sutures. b The mucosa at the operating site was healing well. c The incisions healed well at a six-month review. d A sagittal section from a six-month review CBCT showed evidence of bony healing of the left maxillary lateral incisor. e The same was true of the left maxillary canine. f One-year follow up radiographic examination showed complete healing of the periapical lesion of both teeth and no periapical radiolucency was observed. The red arrow indicates the surgical site

A six-month review showed evidence of bony healing and both teeth were symptom-free (Figure 7c, Figure 7d and Figure 7e). One year after the surgery, the patient was asymptomatic clinically and showed complete bony healing. No periapical radiolucency was observed on radiographic examination (Figure 7f).