Porous Hydroxyapatite and Aluminium-Oxide Ceramic Orbital Implant Evaluation Using CBCT Scanning: A Method forIn VivoPorous Structure Evaluation and Monitoring

Abstract

Objective. This study aimed to define CBCT as a technique for postimplantation in vivo examination of porous hydroxyapatite and aluminium-oxide orbital implant shape, volume and density changes. Methods and Materials. CBCT was used to evaluate 30 enucleated patients treated with spherical polyglactin 910 wrapped hydroxyapatite and aluminum-oxide orbital implants. The mean duration of patient followup was 3.2 years or 1338 days with a range of 0.2 to 7.2 years or 79 to 2636 days in a population with an average age of 40.8 years. Results. The resolution of currently clinically used CBCT equipment allowed detailed structural observation of the orbital hydroxyapatite implants with some modifications. Volume and shape estimations were possible while density evaluation was more complicated compared to medical source computed tomography. The mean densities of the orbital implants were followed and a consistent gradual decrease identified from the beginning of implantation which was better defined after the applied correction procedure. Conclusion. CBCT with lower dosages of radiation exposure can be used to follow changes in implanted high-density porous structures. The density evaluation is possible with calibration modifications. Changes in orbital implant densities identified in this study may correspond to healing and maturation of soft tissues surrounding and penetrating the implants.

Postoperative Imaging of the Orbital Contents

“…They contain internal foci of air in the early postoperative period because of their permeable central framework, which resolves over time as a result of fibrovascular ingrowth (Fig 13). The remaining porous implant constructs-hydroxyapatite and aluminum oxide-are higher in attenuation at CT than is porous polyethylene, likely because of the presence of calcium and alumina, respectively (26). The literature about the attenuation changes of these implants over time is conflicting, specifically for hydroxyapatite, because both continued increased attenuation from bone formation and decreased attenuation from resorption of implant material associated with fibrovascular ingrowth have been reported (26,27).…”

“…The remaining porous implant constructs-hydroxyapatite and aluminum oxide-are higher in attenuation at CT than is porous polyethylene, likely because of the presence of calcium and alumina, respectively (26). The literature about the attenuation changes of these implants over time is conflicting, specifically for hydroxyapatite, because both continued increased attenuation from bone formation and decreased attenuation from resorption of implant material associated with fibrovascular ingrowth have been reported (26,27). This may, at least in part, result from the variability of the mineral attenuation with which hydroxyapatite implants are manufactured (28).…”

A New Method to Evaluate Volumetric Changes in Sinus Augmentation Procedure

“…[16][17][18] On the CBCT images of each patient, the gap inside the implant between the fixture and the bottom of the screw was taken as an Rp (Figure 1a). [16][17][18] On the CBCT images of each patient, the gap inside the implant between the fixture and the bottom of the screw was taken as an Rp (Figure 1a).…”

“…The software was set on standard parameters of density: air density at -1,000 Hounsfield units (HU) and water at 0 HU. [16][17][18] On the CBCT images of each patient, the gap inside the implant between the fixture and the bottom of the screw was taken as an Rp (Figure 1a). In order to obtain a standardized volume of interest (VOI) where the examinations are to be performed, an area of 2 cm (sagittal plane) ¥ 2 cm (axial plane) ¥ 1 cm (frontal plane) was defined in the program by the operator and centered on the Rp.…”

Substituted Hydroxyapatites with Antibacterial Properties

“…On the other hand, a hydroxyapatite material is a perfect component of composite implants with synthetic polymers and biopolymers [ 8 – 10 ]. Dense hydroxyapatite bioceramics, formed into suitable shapes, may be used in the creation of implants for the middle ear and eye (orbital implant), as well as PD implants (Percutaneous Device), and are included in inner dialysis systems [ 11 – 13 ]. Hydroxyapatite is widely used as a coating of metallic implants for bones in order to improve and accelerate the process of osseointegration [ 14 , 15 ].…”