Accidental migration of dental implants: Two unique cases and their management

Dental implant therapy for the rehabilitation of partially or completely edentulous jaws with implant-supported prostheses has become a routine procedure among oral surgeons and dentists [1],[2],[3],[4]. Although dental implant placement has a high success rate and a substantial positive impact on patients’ quality of life, implant migration (i.e., displacement) is among the most common complications of dental implant therapy [5],[6]. Migration or displacement of dental implants is usually associated with poor surgical planning, inadequate surgical technique, or insufficient primary stability [2]. When migration into the maxillary sinus occurs, it can lead to serious complications like sensory disturbances, acute or chronic sinusitis, and oroantral fistula [7],[8]. Theore, removal of a displaced implant from the sinus at an early stage is recommended [7],[9]. Migration or displacement of dental implants most commonly occurs within the maxillary sinus [1],[2],[3],[5],[7],[8],[9],[10],[11],[12]; however, migration into soft tissue appears to be rare.

Several approaches have been described for managing dental implant displacement into the maxillary sinus, including an intraoral approach with an anterior–lateral window to the maxillary sinus, transnasal or transoral endoscopic surgery, and, in some cases, no intervention with follow-up only [5]. The bony window technique, an intraoral approach involving the creation of a bony window pedicled to the sinus mucosa, can be used for removing dental implants displaced into the maxillary sinus [1]. The endoscopic surgical approach can be another treatment choice for removing dental materials displaced into the sinus [10]. Among preoperative imaging modalities used to determine the precise location of a migrated implant, computed tomography (CT) is most commonly employed [4],[11]. Although various approaches and imaging modalities have been proposed for the management of dental implant displacement [1],[3],[9],[10], the optimal strategy remains controversial.

Here, we report two cases of accidental migration of a dental implant into the maxillary sinus or soft tissue, in which the migrated implant was successfully removed using the bony window technique assisted by endoscopy or through precise interpretation of CT images.

Case 1

A 64-year-old female was erred to our department from a private dental clinic with the primary complaint of dental implant migration into the maxillary sinus. Systemically, she had hypertension and was taking oral antihypertensive medication. Two months prior, a second-stage implant surgery had been performed for the right maxillary first premolar. Subsequent panoramic radiography taken at the clinic revealed that the implant had migrated into the maxillary sinus, prompting her erral to our department. The patient exhibited no nasal or oral symptoms (Figure 1). However, panoramic radiography confirmed the presence of the migrated implant in the maxillary sinus (Figure 2). CT further revealed the implant located within the sinus without evidence of mucosal thickening (Figure 3A and Figure 3B). According to the erring dentist, the migrated implant was a tapered fixture measuring 3.5 × 10 mm.

Based on a clinical diagnosis of accidental migration of a dental implant into the maxillary sinus, the patient underwent implant removal using the bony window technique assisted by endoscope under general anesthesia approximately two weeks after the initial visit. A rectangular bone lid was created by osteotomy in the lateral bony wall of the right maxillary sinus, while maintaining the integrity of the sinus mucosa on the superior side (Figure 4A). A rigid endoscope equipped with a digital video unit was inserted through the created bony window, allowing identification and subsequent removal of the migrated implant (Figure 4B and Figure 4C). The lid was finally repositioned and fixed using absorbable suture material passed through the previously prepared holes on the bone lid and the adjacent bone. A CT scan taken six months after surgery showed a healthy sinus appearance and no visible gap between the margins of the bony window on the lateral wall of the right maxillary sinus (Figure 5A and Figure 5B).

Subsequently, a lateral window sinus augmentation was performed under general anesthesia using autogenous bone harvested from the extraction site of the right mandibular third molar, along with an octacalcium phosphate collagen composite (Bonarc; TOYOBO CO., LTD., Shiga, Japan) as the graft material. A surgical window was created in the lateral wall of the right maxillary sinus, and the sinus mucosa was caully elevated to create space for graft placement. Complete healing of both the bony wall and the sinus mucosa at the site where the bone lid had been previously created was observed. The graft materials were placed beneath the elevated mucosa, and the surgical site was then sutured. The postoperative course was uneventful. A CT scan taken four months after the sinus augmentation revealed newly augmented bone on the floor of the right maxillary sinus, with no signs of sinusitis (Figure 6A and Figure 6B). Currently, dental implant treatment is being carried out at a private dental clinic.

Case 2

A 68-year-old male was erred to our department from a dental clinic due to suspected migration of a dental implant into the soft tissue around the maxillary sinus. He had hypertension, for which he was taking oral antihypertensive medication. He also had a local history of a left maxillary fracture. One week earlier, implant placement surgery had been performed for the left maxillary first molar. Subsequently, as postoperative CT revealed that the implant was buccally deviated within the maxilla, an attempt was made to remove it. However, the implant accidentally migrated into the soft tissue adjacent to the maxilla. The patient exhibited no nasal symptoms. Intraoral examination revealed diffuse swelling of the maxillary buccal mucosa, although no distinct mass was palpable (Figure 7). Panoramic radiography showed superior displacement of the implant beyond the maxillary alveolar region (Figure 8). Three-dimensional CT showed that the implant was located buccally around the left maxillary alveolar region, and maxillary bone deformity was observed (Figure 9). According to the erring dentist, the migrated implant was a straight fixture measuring 3.3 × 10 mm.

Based on the clinical diagnosis of accidental migration of a dental implant into the soft tissue adjacent to the maxilla, implant removal under local anesthesia was scheduled for the afternoon of the same day. Guided by the surgeon’s interpretation of the CT images taken in the morning regarding the three-dimensional position of the migrated implant, a horizontal incision was made in the gingivobuccal mucosa at the level of the root of the maxillary left first molar. The implant was subsequently identified and retrieved without complications (Figure 10A and Figure 10B). The postoperative course was uneventful. Currently, no further implant treatment has been initiated at the same site.

The clinical courses of these two cases provided important insights. Although accidental migration of a dental implant into the maxillary sinus, as seen in case 1, can occur, bone healing is generally favorable following implant removal using the bony window technique assisted by endoscope. Subsequent maxillary sinus floor elevation can then be performed successfully. Minimally invasive removal under local anesthesia is feasible with appropriate interpretation of CT images, although migration of a dental implant into the soft tissue adjacent to the maxillary sinus—as observed in case 2—appears to be rare.

Accidental displacement of roots, endodontic materials, and dental implants into the maxillary sinus is a relatively common complication in dental practice [3]. Displacement of dental implants into the maxillary sinus typically occurs during implant placement or is identified during secondary surgery [2]. Regarding the causes of migration, perioperative implant displacement is often associated with inadequate surgical planning, such as placing implants in sites with insufficient bone height or volume, surgical inexperience, improper procedures (e.g., overpreparation of the recipient site, excessive force during implant insertion), or perforation of the sinus membrane during drilling [5],[11]. During the healing period, previous studies have suggested three probable mechanisms: (1) changes in intrasinus and nasal air pressures; (2) autoimmune reactions to the implant, leading to peri-implant bone destruction and compromised osseointegration; and (3) bone resorption caused by an incorrect distribution of occlusal forces [2],[9],[12]. Additionally, previous study showed that the incidence of implant migration into the sinus cavity is higher for cylindrical implants as compared to conical ones, for narrower implants [12]. In case 1, placement of a narrow implant in a site with insufficient bone height may have caused perforation of the sinus membrane and compromised osseointegration, and following secondary surgery, it appeared that the implant had migrated into the maxillary sinus due to occlusal forces on the healing abutment, despite its conical shape. In case 2, placement of a cylindrical implant in a site with insufficient bone volume may have resulted in migration into the buccal soft tissue, which may have been associated with inadequate surgical planning.

Early removal of implants displaced into the sinuses is advisable to prevent further complications, such as facial pain, airway obstruction, nasal discharge, and infection, which may result from migration into other upper structures, even in asymptomatic cases [7],[13]. Although both cases were asymptomatic, prompt removal was performed in consideration of potential future complications and ethical concerns.

Removal of a foreign body into the sinus cavity may be performed using different techniques: extraction through the intraoral fistula, direct approach by opening a lateral window into the sinus, and transnasal or transoral endoscopic surgery [5]. The bony window technique, in which the bone lid was cut on three sides—inferior, medial, and distal—while the superior side remained intact, enables the creation of a bony window pedicled and vascularized by the thin blood vessels of the sinus mucosa, and also allowed the window to be rotated easily [1]. The advantages of this procedure include improved visibility of the sinus cavity, rapid healing of the sinus mucosa, and complete re-ossification of the bone lid margins, which may, if indicated, allow for a safe sinus lift procedure via a lateral approach, similar to that performed in a previously untreated maxillary sinus [1]. On the other hand, clinicians may perentially choose the transoral endoscope-assisted approach for removing a dental implant displaced into the maxillary sinus, assuming that the implant may change position within the sinus [14]. This approach offers wider visibility and access, enabling rapid and safe removal via a minimally invasive technique under endoscopic control [4],[14]. In case 1, future sinus lift and implant placement in the same area were anticipated. Extraction through the intraoral fistula could have required excessive enlargement of the existing implant osteotomy, potentially complicating subsequent implant treatment. Theore, a bony window technique was employed, allowing a safe lateral approach sinus lift. Because the erence CT image had been obtained two weeks prior and the implant’s position might have shifted, an endoscope-assisted approach was also used to provide wider visibility and ensure safe removal. The window was created large enough for safe insertion of the endoscope shaft. Complete healing of the bone lid margins was achieved, and the subsequent lateral window sinus augmentation was highly successful.

An accurate radiological examination is essential to determine the exact location of a migrated implant before its removal [4],[8]. Accurate localization minimizes the invasiveness of the procedure, reduces patient discomfort, and helps avoid further complications while improving clinical outcomes [4]. Three-dimensional imaging is particularly well suited for this purpose and should be performed immediately before surgery, as secondary migration can occur within a short period [4]. In case 2, removal surgery was performed a few hours after the CT scan, and the migrated implant, lodged within the soft tissue, appeared unlikely to move. We theore considered that the CT findings accurately lected the actual condition, and that caul interpretation of the three-dimensional reconstructed CT images enabled minimally invasive implant removal.

Accidental migration of dental implants can occur either into the maxillary sinus or into adjacent soft tissue. In cases involving the maxillary sinus, the endoscope-assisted bony window technique may facilitate favorable bone healing and may permit subsequent sinus floor elevation. Rare soft tissue migration might also be managed in a minimally invasive manner under local anesthesia with accurate interpretation of CT images. Our experience may serve as a useful erence for physicians and oral and maxillofacial surgeons managing similar cases in clinical practice.