Clinical characteristics and removal of broken burs retained in the lower jaw

Abstract

Background

A broken bur retained in the lower jaw is an uncommon complication that occurs during the extraction of the impacted mandibular third molar. The purpose of this retrospective study was to investigate the clinical characteristics of the broken burs and review our experience with the removal of the broken burs in these cases.

Methods

All patients, who suffered the broken bur remained in the lower jaw due to the extraction of the impacted mandibular third molar and presented to our hospital from July 2019 to July 2024, were included in this retrospective study. Demographic information of these cases was analyzed by descriptive statistics and the treatment methods were summarized.

Results

Based on the location of the broken burs, these cases can be classified into three types: (1) in the mandible; (2) between the lingual alveolar bone and periosteum; and (3) in the soft tissue of the mouth floor. In the cases of type 1, the removal of the broken burs was assisted by a tooth-supported digital guiding plate that precisely located the broken bur. The localization of the broken burs in types 2 and 3 was based on the preoperative radiographs, and the removal of the broken burs in the two types was mainly dependent on the surgeons’ experience. All the broken burs were successfully removed, and all patients displayed uneventful healing.

Conclusions

The broken burs remained in the lower jaw due to the extraction of the impacted mandibular third molar assumes many forms. The key point for the successful removal of the broken burs is to choose the corresponding methods based on the location of the broken burs.

Background

Mandibular third molar extraction is one of the most common oral surgery procedures. Mandibular third molar extraction is considered difficult due to impaction, proximity to the internal and external mandibular canal, restricted access, and anatomical considerations. High-speed handpieces are often used during mandibular third molars extraction for tooth sectioning or bone removal, and breakage of the burs happens occasionally when the instrument is not properly selected and the bur is not properly used [1,2,3]. Breakage of the burs might be due to the reuse of bur and repeated sterilization cycles. In addition, excessive cutting depth and pressure with lateral force in dentoalveolar surgery are the reasons that contribute to the breakage of the burs.

Generally, the doctor should remove them almost immediately if breakage of the bur does occur. In most cases, the broken bur can be removed immediately. The removal of the broken bur is usually easy when it is visible. If the broken bur moves deeply and is not visible, it will be difficult to locate and remove. The broken burs should be removed as soon as possible before they migrate deeper into the adjacent tissues [4]. It obliges to search for the broken instrument fragments and remove them to avoid possible infection or to prevent complications due to swallowing or aspiration of the broken fragments [5]. Especially when the broken bur is small, it will cause secondary injury due to the extensive surgery. The patients usually complain of uncomfortable symptoms caused by the broken bur remained in the lower jaw, such as swelling, pain, and limited mouth opening. Additionally, the patient is alarmed by the awareness of a foreign body remained in the body [6].

Accidental breakage of surgical instruments is a rare surgical complication that has been reported infrequently in the literature. The previous literature on patients suffering the broken bur remained in the lower jaw due to the extraction of the impacted mandibular third molar consists mostly of case reports [1, 2, 4, 6,7,8,9], whereas no case series analysis. The purpose of this retrospective study is to investigate the clinical characteristics of the broken burs remained in the lower jaw and review our experience of the removal of the broken burs in these cases.

Patients and methods

All patients identified as suffering a broken bur retained in the lower jaw due to extraction of impacted mandibular third molar presenting to our hospital from July 2019 to July 2024, were included in this retrospective study. To be included in the study sample, patients had to meet the following criteria: (1) available preoperative Computed Tomography (CT) images; (2) at least 3 months of follow-up data available. The exclusion criteria were as follows: (1) the patients underwent mandibular third molar extraction and other oral surgery procedures simultaneously; (2) the patients refused the surgery of removing the broken bur. This study was approved by the institutional review board at Hospital of Stomatology, Wuhan University (approval number 2024- B29), and was conducted in accordance with the institutional review board standards. The informed consent to participate was obtained from all of the participants in the study. The investigators adhered to the Declaration of Helsinki in this study.

The following information was collected from the patients’ medical records: age, gender, the tooth involved, clinical symptom, length of the broken bur, operation duration, and postoperative complications. The preoperative CT images were collected, aiming to diagnose the position of the broken burs and analyze the characteristics. At the same time, the methods used to remove the broken burs were analyzed and summarized. The follow-up data consisted of regular clinical assessment of mouth opening, numbness of the tongue, and pain. Demographic information and details of these cases were tabulated and summarized by descriptive statistics, in which the mean of the patients’ ages, length of the burs, and operation duration were calculated.

Results

Fifteen patients suffering a broken bur retained in the lower jaw due to extraction of impacted mandibular third molar were included in the study (Table 1). There were ten females and five males. The ages of these patients ranged from 19 to 51 years, with a mean of 30.33 years. Nine teeth were the lower left third molar and the other were the lower right third molar. The patients had the following symptoms: limited mouth opening (n = 7), swelling (n = 5), numbness (n = 1), or pain (n = 5). The length of the broken burs averaged 5.85 mm, median 6.0 mm (range from 1.5 to 9.3 mm). Based on the location of the broken burs indicated in the preoperative CT images of the 15 patients, there are three types of presentations: (1) in the mandible (Type 1, n = 6); (2) between the lingual alveolar bone and periosteum (Type 2, n = 4); (3) in the soft tissue of mouth floor (Type 3, n = 5). The surgical treatment varied based on the location of the broken burs, which can be summarized as follows.

Table 1 The 15 cases suffering a broken bur retained in the lower jaw due to extraction of impacted mandibular third molar

For the cases with a broken bur remained in the mandible (Type 1), a personalized tooth-supported digital guiding plate was designed based on the preoperative CT data (Fig. 1A), aiming to accurately locate the foreign body intraoperatively. The tooth-supported digital guiding plate was designed to locate the foreign body through the posterior molars in the mandible (Fig. 1B&C). The original wound was used, or an extended incision was made to raise the gingival mucoperiosteal flap and expose the alveolar bone. The tooth-supported guiding plate was placed in the posterior molars. The bone around the positioning indicator point of the guiding plate’s indicator bar was removed, and then the broken bur was targeted and removed (Fig. 1D&E).

Fig. 1

A The CT scans (axial, sagittal and coronal) revealed a metal foreign body in the mandible. B & C The tooth-supported digital guiding plate was designed and printed. D The bone around the positioning indicator point of the guiding plate’s indicator bar was removed. E The removed bur fragment

For the cases with a broken bur remained between the lingual alveolar bone and periosteum (Type 2), preoperative CT imaging and digital model were prepared to display the spatial relationship between the mandible and the broken bur (Fig. 2A&B). The original wound was used, or an extended incision was made to raise the lingual mucoperiosteal flap and expose the space between the mucoperiosteal and the lingual alveolar bone. The bur was found and removed under direct vision (Fig. 2C). The capturing of the broken bur was assisted by methods of magnet attraction and tube suction.

Fig. 2

A The CT scans (axial, sagittal and coronal) revealed a metal foreign body that remained between the lingual alveolar bone and periosteum. B The digital model displayed the spatial relationship between the mandible and the broken bur. C The removed bur fragment

For the cases with a broken bur remained in the soft tissue of the mouth floor (Type 3), preoperative CT imaging and digital model was prepared to display the spatial relationship between the mandible and the broken bur (Fig. 3A&B). The original wound was used or an incision on the mouth floor was made to expose the broken bur. The broken bur was detected and captured depending on the CT images and the experience of the surgeons (Fig. 3C).

Fig. 3

A The CT scans (axial, sagittal and coronal) revealed a metal foreign body remained in the soft tissue of the mouth floor. B The digital model displayed the spatial relationship between the mandible and the broken bur. C The removed bur fragment

The operation duration ranged from 30 to 180 min, with a mean of 79 min. The average operation duration of Type 1 was 73 min, ranging from 30 to 120 min. The removal of the broken burs in Type 2 was less time-consuming, and the average operation duration was 32.5 min with a range of 30–40 min. The removal of the broken burs in Type 3 was most time-consuming, and the average was 126 min with a range of 60–180 min.

The postoperative orthopantomography confirmed the broken bur was removed in all patients. Postoperatively, all patients displayed uneventful healing without complications such as postoperative hemorrhage or infection, whereas seven patients reported experiencing tongue numbness after the surgery. After the follow-up period of three months, all patients displayed normal mouth opening without any pain, but one patient still complained of numbness of the tongue.

Discussion

A broken bur remained in the lower jaw is an uncommon complication in extraction of mandibular third molars. The cases in which the broken bur cannot be found successfully were due to poor visibility caused by hemorrhage, or the location of the broken bur being too deep to be targeted. In the previous literature regarding patients suffering a broken bur that remained in the lower jaw due to extraction of mandibular third molar [1, 2, 4, 6,7,8,9], there is no formal report on the classification of these broken burs. To the best of our knowledge, it is the first time, in the literature, that case series of broken burs remained in the lower jaw due to extraction of mandibular third molar are investigated. In this study, we summarized that these broken burs could be classified into three types: (1) in the mandible; (2) between the lingual alveolar bone and periosteum; and (3) in the soft tissue of the mouth floor, based on the location of the burs. Meanwhile, based on the classification, we describe the corresponding treatment strategies for removal of broken burs remained in the lower jaw.

In this study, the removal of the broken bur in the three types varied in operation duration. The type 2 was less time-consuming. The broken burs in type 2 were located in the “bag” formed by the mucoperiosteal and the lingual alveolar bone. The bag is open when the space between the mucoperiosteal and the lingual alveolar bone is exposed, and the bur usually can be seen in the bag. The capturing of the broken bur can be assisted by methods of magnet attraction and tube suction because the broken bur is located in the “bag”. To be noticed that the removal of those broken burs in type 2 should be minimally invasive. The blind exploration of tissue spaces is wont to push the broken bur deeper, and it will break through the periosteum and then migrate farther into the mouth floor, becoming the type 3. The removal of the broken burs in the type 3 is the most time-consuming. Compared with type 1 and type 2, the removal of the broken burs in type 3 is challenging. It is difficult to target the broken bur in the soft tissue of the mouth floor because the broken bur will constantly move into the soft tissue. The removal of the broken burs in type 3 is mainly dependent on the surgeons’ experience.

Accurate localization is essential for the successful removal of foreign bodies. In general, Three-dimensional (3D) imaging techniques have become standard for localization and treatment strategies with the advantage of visualizing not only foreign bodies but also surrounding anatomical structures [10,11,12]. The broken bur presents as a high-density sign on CT images, which is easy to identify. However, CT images can only be used as a preoperative reference to determine the optimal approach. The broken bur cannot be precisely targeted in the operation and thus the surgeons can only rely on their own experience. Computer-assisted navigation systems have been widely applied to the localization and removal of foreign bodies in the maxillofacial region [13,14,15]. However, this system has certain limitations for the removal of foreign bodies in some anatomical structures with a mobile nature, such as the mandible and the soft tissue of the lower jaw [8, 14, 16]. The cause is the topographic changes triggered by surgery, resulting in discrepancies between the preoperative image data and the surgical site. The patient’s mouth should be open and the position of the mandible is changed during the removal of the foreign body in the lower jaw [14].

In recent years, with the development of computer-aided design software, digital guiding plates based on 3D printing technology have been widely used in all kinds of oral surgery [17, 18]. Teeth are an ideal anatomical structure for plate retention, and a change in body position will not affect tissue morphology [19]. Digital tooth-supported guiding plates make the operation easier, especially for novice surgeons [20]. In the cases of type 1, we removed the broken burs assisted by this method. This tooth-supported digital guiding plate precisely located the position of foreign bodies in the lower jaw, which was not affected by the position of the mandible in the operation. The result in these cases of type 1 confirms that removing foreign bodies becomes objective and minimally invasive under the assistance of the digital guiding plate. In addition, the tooth-supported digital guiding plate can be designed and fabricated preoperatively and has the advantages of small size, easy usage, and low cost. If the foreign body in the mandible remains in a constant position with the teeth of the mandible, a tooth-supported digital guiding plate can be used to target the foreign body. However, if the foreign body is in the soft tissues, its position may change during the surgery, which will result in discrepancies between the preoperative imaging data and the surgical site. For this reason, a tooth-supported digital guiding plate is not a suitable technique for removing the broken burs in types 2 and 3.

Small sample size is the main limitation of this study. With this limited study, it is not known whether these findings can be applied to all clinical scenarios. Notwithstanding this limitation, this study has proven that the corresponding treatment method for removal of broken burs based on the classification can potentially serve as efficient strategies. Future research will reconfirm these findings by more cases.

Conclusions

The broken burs retained in the lower jaw due to the extraction of mandibular third molar can be classified into three types: (1) in the mandible; (2) between the lingual alveolar bone and periosteum; and (3) in the soft tissue of mouth floor. In the cases of type 1, removal of the broken bur can be assisted by a tooth-supported digital guiding plate, aiming to precisely locate the position of the broken bur. The localization of broken burs in types 2 and 3 is based on the preoperative radiograph examination, and the removal of the broken burs in these 2 types is mainly dependent on the surgeons’ experience. The corresponding methods may serve as a better option for the successful removal of the broken burs, based on the location of the broken burs.