A Cone Bean Computer Tomography Investigation of the Newly Formed Mandibular Anterior Ridge following the Treatment of an Extended Comminuted Fracture: A 12-Year Follow-Up

Abstract

Introduction: Extensive comminuted fractures are associated with tooth loss that ultimately leads to dimensional changes in the hard and soft tissues of the alveolar ridge. Reconstruction of the lost mandibular anterior ridge is very complex due to the natural curvature of the region. Case Presentation. In this case report, the combination of the modified shell technique with autologous bone plates and the guided bone regeneration (GBR) technique was performed on an 18-year-old patient after a comminuted fracture, to ensure new bone formation in the anterior ridge with a natural curvature. After the treatment progressed without complications, three dental implants were placed. Annual cone beam computed tomography (CBCT) images were obtained and evaluated using the GNU Image Manipulation Program (GIMP© 2.10). This allowed measurements of the buccal and lingual bone around the implants, showing the annual bone loss in a twelve-year observation period. Discussion. The treatment of the comminuted fracture and the combination of the modified shell technique with autologous bone plates, the GBR technique, and implant placement can be considered successful. The three dental implants were osseointegrated in 2010, with the buccal bone level averaging 1.31 mm below the implant shoulder and the lingual bone level 1.57 mm above the implant shoulder. In 2021, the measurements showed a bone loss of 0.99 mm at the buccal implant shoulder and 0.69 mm at the lingual implant shoulder.

Conclusion: The combination of the modified shell technique with autologous bone plates and the GBR technique is a reliable method to ensure new bone formation in the anterior ridge. The use of CBCT is an excellent method to evaluate bone resorption around dental implants, but due to minimal bone resorption in the observation period, an annual CBCT examination is exaggerated.

Figure 1

(a) CBCT: an example diagram showing how the measurements were taken ((A) implant length for reference (manufacturer information); (B) shoulder of the implant; (C, C¹) distance for lingual measurements were recorded from the implant shoulder (C) to the bone level (C¹); (D, D¹) distance for buccal measurements were recorded from the implant shoulder (D) to the bone level (D¹). (b) Graphical representation (frontal section): the combination of the modified shell technique with autologous bone plates and the guided bone regeneration technique ((A) mixture of milled bone chips and bone substitute; (B) bone plates; (C) osteosynthesis screws; (D) alveolar ridge; (E) periosteum; (F) collagen membrane). (c) Graphical representation (sagittal section): combination of the modified shell technique with autogenous bone plates and the guided bone regeneration technique. (d) The formula given for determining the implant length served as a reference for converting the measured pixels into millimetres.

Figure 2

(a) CBCT horizontal view: facial skull with comminuted fracture in the mandible. (b) CBCT vertical view: facial skull with comminuted fracture in the mandible. (c) Buccal view of the clinical situation 12 years after comminuted fracture. (d) Lingual view of the clinical situation 12 years after comminuted fracture.

Figure 3

(a) OPT: postoperative treatment of the comminuted fracture with two osteosynthesis plates and two lag screws. (b) OPT: postoperative restoration of the switching gap with an adhesive bridge. (c) OPT: removal of an osteosynthesis plate at 10 months after the accident. (d) OPT: insertion of three Ankylos® implants with the dimensions 3.5 × 14 mm. (e) OPT: after inserting the three Ankylos® implants, the switching gap was closed again with an adhesive bridge. (f) OPT: definitive restoration of the implants with a metal-ceramic bridge in the anterior part of the mandible.

Figure 4

(a) A graph showing the buccal bone level from 2010 to 2021 in mm, with each line representing the bone level for each implant. (b) CBCT: analysed CBCT image from 2010 to 2021 of each implant (implant 1: region 32; implant 2: region 31/41; implant 3: region 42). (c) A graph showing the lingual bone level from 2010 to 2021 in mm, with each line representing the bone level for each implant.