Usefulness of Polycaprolactone and Beta-tricalcium Phosphate Implant for Reconstruction After Mandibular Reduction

Summary:

Mandibular reduction is common in East Asia, and earlier methods entirely removed the mandibular angle. This report presents a clinical case of mandibular angle reconstruction using a custom polycaprolactone and beta-tricalcium phosphate implant. Designed via 3-dimensional modeling from computed tomography data, the implant fits precisely without requiring fixation. One year postoperatively, a computed tomography scan showed successful bone replacement, and the patient was satisfied with the contour. This technique eliminates the need for autologous grafts and offers a promising alternative to mandibular reconstructions.

Takeaways

Question: Is there a good procedure for mandibular reconstruction when too much has been removed due to mandibular reduction?

Findings: The polycaprolactone and beta-tricalcium phosphate implant is gradually replaced by autologous bone.

Meaning: There is a problem with donor-site morbidity with autologous bone, and it does not replace other artificial bones. We believe that polycaprolactone and beta-tricalcium phosphate, which replaces autologous bone, is a useful reconstruction method.

INTRODUCTION

Correcting prominent mandibular angles is a popular procedure in East Asian individuals. This procedure involves the remodeling of the physiological mandibular angle. Mandibular V-line osteotomy preserves the mandibular angle and has become the standard procedure in recent years. However, before this procedure, the emphasis was on long curved osteotomies, in which the mandibular angle was eliminated and the size of the mandible was reduced.¹ Therefore, patients who have previously undergone long curved osteotomies often require reconstruction of the mandibular physiological angle.

Possible reconstruction methods include autogenous bone grafting, iliac bone grafting, and reconstruction using hydroxyapatite bone cement. In the present case, we reconstructed the mandible using custom-made polycaprolactone (PCL) (Evonik Industries, Essen, Germany) and beta-tricalcium phosphate (β-TCP) (Foster Corporation, Putnam, CT) composite artificial bone that could replace autogenous bone (TnR Mesh; T&R Biofab Co., Ltd., Seoul, Korea). Because of its porous structure, the PCL and β-TCP implant has been reported to possess osteoinductive properties, being absorbed by the body and replaced by bone.^2–4 Although clinical applications of the implant in maxillary and orbital reconstruction have been reported,^4,5 to our knowledge, this is the first clinical report of mandibular reconstruction using a PCL and β-TCP implant.

CASE PRESENTATION

The patient was a 23-year-old woman. She had undergone mandibular reduction 6 months previously in a foreign country. However, because of language communication problems, she was unable to effectively communicate her ideal appearance, resulting in excessive shortening of the mandibular ramus and enlargement of the gonial angle. Therefore, the mandible resembled that of a dog, appearing to protrude just below the earlobe. The patient desired a more natural appearance and requested a mandibular reconstruction.

Preoperative facial CT images, with a thickness of 1 mm, were exported in digital imaging and communications in medicine format. New mandibular margins and mandibular angle morphologies were designed using a 3-dimensional modeling software (Mimics version 20.0, 3-Matic version 14.0; Materialize, Leuven, Belgium). The implant was designed to fit the outer and inner sides of the mandible (Fig. 1). The PCL and β-TCP were mixed in a ratio of 8:2. The PCL and β-TCP mixture was 3-dimensionally printed using a multihead deposition system. The scaffolds were freeze-dried at −85°C for 24 hours and then sterilized using a 450-W ultraviolet lamp for 4 hours. For detailed methods, refer to previous reports.^2,3 The actual left PCL and β-TCP implant is shown in the Video. (See Video [online], which displays the actual left implant. The implant was designed to sandwich the remaining mandibular bone on the inside and outside.)

Fig. 1.

Designing implants from CT data.

Video 1. This video displays the actual PCL/β-TCP implant.

Download video file ^{(2.1MB, mp4)}

The mandible was approached through the previous vestibular incision, and the implant insertion site was dissected. The medial pterygoid muscle was adequately dissected. Once the implant was inserted, it was fitted to the mandible and did not require screws or fixation.

One year postoperatively, computed tomography (CT) revealed good autogenous bone replacement (Fig. 2). The patient was satisfied with the morphology of the reconstructed mandible.

Fig. 2.

Comparison of pre- and postoperative CT scans. Preoperative (A), 3-month postoperative (B), and 1-year postoperative (C). The reconstructed mandible underwent gradual osteogenesis.

DISCUSSION

For orbital reconstruction, implants can be made into flexible sheets because they can be adjusted to different hardnesses.⁵ For mandibular reconstruction, the implant was designed to be firm in thickened areas with slight flexibility at the thin edges. This flexibility reduces the risk of breakage during insertion. Furthermore, the implant has osteoinductive properties, making replacement without the use of autologous bone another major advantage.⁶ However, because the implants are artificial, they need to be removed in the event of infection. In addition, because of atrophy of the masseter and other muscles, the design needs to be reduced to the size at the time of the initial treatment. The cost of one implant is approximately $2000–$2500, which is expensive. It takes approximately 1 month from the time the design is finalized on the computer to the time it is created, shipped, and reaches the operating room.

In conclusion, we reported a case of mandibular reconstruction using a PCL and β-TCP–based custom-made implant, which was followed up for more than 1 year and demonstrated good bone formation and morphology. This may help improve the management of patients undergoing excessive mandibular osteotomies.

DISCLOSURE

The authors have no financial interest to declare in relation to the content of this article.