Cosmetic surgery for esthetic purposes is an unrestricted medical procedure with diverse treatment methods. Therefore, diverse cosmetic biomaterials are used in such procedures. In this study, we identified 21 cases involving four types of cosmetic surgery-derived foreign bodies in the nasal, buccal, and chin regions of the face that were included in CT scans.

Cosmetic rhinoplasty can change the height and shape of the nose. When the nose height is altered, the height of the nasal tip or bridge of the nose can be modified. With respect to reshaping, the shape of the nasal tip or width of the nose can be reduced; the nostril shape can be changed. Foreign bodies in the nasal area from these procedures can include prostheses, injectables, and sutures composed of polydioxanone. Dorsal rhinoplasty using alloplastic implant materials, such as silicone, is the rhinoplasty procedure most commonly performed in Asian populations [7]. The artificial cartilage is constructed from silicone resin, and it exhibits either I- or L-shape, consistent with the imaging findings in the present study.

Of the 15 nasal foreign bodies detected during the study period, 14 had CT values greater than 100 HU and were regarded as nasal prostheses. Soft tissue images showed a high-density, bone-like material that was easily detected. The remaining foreign body, which was difficult to detect on soft tissue images, had a CT value of 4 HU and high signal intensity on STIR images; it presumably comprised a water-like injectable material that had been injected in a linear manner into the nasal dorsum. On hard tissue images, it was difficult to detect all foreign bodies in the nasal dorsum, but there were three foreign bodies with a heterogeneous and high-density posterior margin. Although most nasal foreign bodies exhibited uniform density, various alloplastic implant materials are available [8]; thus, compositional differences among products were suspected. Silicone plates were clearly visible as very low-intensity plates (void signals) on sagittal or coronal T1- and T2-weighted MRI [9]. In five of the six cases where a foreign body was present in the nasal region and included in the scope of MRI, the foreign body displayed a void signal suggesting that the material was silicone. In the present study, there were no complications after cosmetic rhinoplasty (e.g., infection), which may partially explain the lack of self-reporting.

Two different types of foreign bodies (five cases in total) were found in the buccal region. Thread lifting with sutures is a cosmetic procedure where lax tissue is lifted and repositioned to create a more youthful-looking facial contour [10]. Lifting uses absorbable threads such as polydioxanone, polycaprolactone, and poly L-lactic acid threads, as well as nonabsorbable threads comprising Prolene® and polyproline [11]. In one case in the present study, a nonabsorbable thread was suspected, but the material could not be identified. On CT images, it was difficult to determine the continuity of the foreign body, which appeared to be multiple punctate foreign bodies. However, panoramic radiographs were useful in identifying the history of thread lifting because the foreign bodies were linear and clearly visible across a large portion of the buccal region, excluding the nasal and orbital areas.

In the buccal region, cosmetic surgery is performed to lift and improve skin from within through the application of injectables into wrinkles and skin depressions. Commonly injected sites on the face include the perioral area, periocular region, nasolabial folds, malar fat pad, marionette lines, glabella, and lips [12]. There are numerous types of injectable facial fillers, including autologous fat fillers, collagen fillers, calcium hydroxyapatite fillers, hyaluronic acid fillers, poly-l-lactic acid, polyalkylimide and polyacrylamide hydrogels, and silicone oil fillers [12, 13]. Although hyaluronic acid is the most widely used and well-known injectable agent, its effect lasts only 1 to 2 years, and it requires regular visits. Thus, some cosmetic surgeons use the semi-permanent Aquamid® for economic reasons. Aquamid® is a transparent, nonabsorbable injectant consisting of 97.5% pure water and 2.5% cross-linked polyacrylamide [14]. However, nonabsorbable preparations are foreign bodies that have higher risks of secondary infection.

In the present study, postoperative infections occurred in two of the four cases involving buccal injections. The two patients who desired treatment of buccal swelling did not self-report a history of cosmetic surgery during the initial examination. Because imaging findings suggested that cosmetic materials were the source of infection in these two patients, they were reinterviewed after imaging; both had a history of semi-permanent residual Aquamid® injection approximately 2 years prior (Fig. 5). In clinical settings, reactive lesions can easily be misdiagnosed as soft tissue tumors or cysts. Because few problems are reported after cosmetic procedures and there is limited experience managing such problems, especially in rural areas, appropriate diagnoses can be difficult to establish. When a foreign body is detected without a dental source of infection, a history of cosmetic surgery should be considered; the foreign body may have a cosmetic origin.

CT images of foreign bodies in the buccal region showed an irregularly shaped lumpy or cord-like shape from the zygomatic muscle to the subcutaneous fat layer, with multiple foreign bodies. CT images of the foreign bodies revealed soft tissue-like density similar to muscle, which could be overlooked without careful interpretation. When inflammatory findings were observed without a dental source of infection, a cosmetic surgery-derived foreign body was the possible cause.

MRI showed high signal intensity on T2-weighted and STIR images, indicating that water was the main component of the foreign body, which aided in diagnosis. Therefore, additional MRI examination may be useful in the cases of unexplained inflammation that are difficult to diagnose because they can be identified by T2-weighted or STIR images.

A prominent, well-defined chin and jawline are key aspects of a harmonious, beautiful face. Contouring of the lower third of the face is an important component of cosmetic surgery [15]. Chin augmentation can be performed with injectables, implantation, or osseous genioplasty [15]. Silicone jaw implants are frequently used in cosmetic surgery to emphasize facial harmony [16, 17]. The foreign body identified in the chin region in the present study exhibited uniform density and was detected incidentally. The silicone jaw implants in the chin region had a smooth hemispherical shape; after initial recognition, diagnosis was relatively easy for oral radiologists.

Cosmetic surgery-derived foreign bodies in the maxillofacial region were more common in women (90.5%, 19/21 cases), and the age range varied from 20 to 84 years. In two cases where the foreign body was regarded as a possible source of infection, reinterviewing revealed a history of cosmetic surgery; in all cases, regardless of sex or site, there was no self-reporting during the initial examination. Therefore, clinicians should be aware that cosmetic surgery-derived foreign bodies may be present in numerous patients, regardless of age or sex.

This study had some limitations. First, because this study focused on cosmetic surgery-derived foreign bodies in the maxillofacial region that were incidentally detected on CT images, injectable agents in soft tissues (e.g., the lips) may have been missed. Although MRI may be useful to identify injectables because of their high signals on STIR and T2-weighted images, it was not realistic in the present study because the number of MRI examinations was much smaller than the number of CT examinations. Second, unlike urban areas where cosmetic surgery is commonly performed, the number of foreign bodies associated with cosmetic surgery was estimated to be low in the rural area where this study was conducted; this regional difference may have influenced the findings. Third, it was difficult to identify all foreign bodies, which made diagnosis challenging because individuals who underwent cosmetic surgery may have forgotten or denied the procedure; alternatively, they may not have known the type of foreign material used.

In conclusion, we observed the following four types of cosmetic surgery-derived foreign bodies in the maxillofacial region that could be identified via CT examination: nasal prostheses (nasal region), lifting sutures and injectable facial fillers (both in the buccal region), and silicone chin implants (chin region). Foreign bodies in the buccal region included a case in which the foreign body was the source of infection; a cosmetic surgery-derived foreign body should be suspected when a foreign body is identified without a dental source of infection. In addition, clinicians should be aware that cosmetic surgery-derived foreign bodies may be present in numerous patients, regardless of age or sex.