Button of Hydroxyapatite Composite for Craniotomy Flap Fixation: Fabrication and Mechanical Properties

This paper deals with the development of button made from a hydroxyapatite (HA) and bioglass composite. The HA powder derived from the bovine bone were added 2.5 and 5 wt% of P2O5-CaO-Na2O-bases glass and subsequently sintered at 1200 - 1350 °C to form the HA ceramics. It was observed that the densest HA ceramic could be achieved for the sample composed of hydroxyapatite with the addition of 5 wt% of bioglass and sintered at 1300°C, resulting in the maximum value of bending strength of about 77 MPa, which ensured the use in load bearing applications of this HA ceramic. The HA and 5 wt% bioglass composite is designed as a button for reattach the bone flap after a craniotomy procedure. Each device is comprised of an inner plate and an outer plate. The fabrication processing was used the powder compression and then sintering at 1300°C for 3 h. The button have fracture toughness (K1C) values of 1.3±0.1 MPa.m1/2 and bending strength of 65.7±3.8 MPa. The liquid phase sintering of this sample contributed to the high mechanical properties that can be use as craniotomy flap fixation.

Analysis of Stress Distribution for Powder Compression Molding by Finite Element Method

The ultrasonic mold was designed for the ceramic powder compression. CAD and CAE were used in the design to analyze the mold strength and its natural frequency. The study of stress distribution and compression in upper and lower punch, mold body and waveguide comparison of stresses was analyzed by FEA experiments under maximum compression at 50,000 N to validate the results of both methods and the mold natural frequency. The difference between FEA and experimental analysis was 3-7%, acceptable. The redesign results in a cylindrical mold body with the outer diameter of 80 mm, the height of 100 mm, and the upper punch of 125 mm in length. The six sides are 26 mm of the high waveguide with 100 mm height. The internal and external diameters are 80 and 110 mm, respectively. The mold has been redesigned and can support the maximum compression force of 1,500 kN. with the bearing steel, AISI 52100, obtainable hardness 65 HRC, the stress concentration occurs at the neck of the upper punch using the ultrasonic at 12.00 to 12.45 kHz.