Personalized Orbital Fracture Repair: Enhancing 3D-Printed Titanium Mesh with Biomimetic 3D-Printed HAP-COL Frameworks.

OBJECTIVE: Orbital wall fractures require precise reconstruction to restore orbital volume and visual function, and bio-inert titanium implants benefit substantially from osteoconductive surface modifications. This study evaluated the biocompatibility and osteogenic potential of hydroxyapatite-collagen (HAP-COL) composites used in titanium implants intended for orbital fracture repair, comparing a sprayed HAP coating with a robocasting-deposited, 3D-printed HAP-COL layer. METHODS: HAp-COL hybrid powder (HAp:COL mass ratio 4:1) was prepared by hydrothermal synthesis at 100 °C and 104 Pa, followed by spray drying, and characterized by FAAS, ICP-OES, FT-IR, XRD, and SEM-EDS. Two implant configurations were tested: Sample 1 (titanium with sprayed HAp) and Sample 2 (titanium with three robocasting-deposited 3D-printed HAP-COL layers). Cytotoxicity was assessed on a normal human osteoblast cell line (NHOst, Lonza CC-2538) in accordance with ISO 10993-12, using sample extracts at stock concentration and binary dilutions (1/2, 1/4, 1/8) and quantified by MTT assay at 24 and 48 hours. RESULTS: Both samples showed dose- and time-dependent viability profiles within the acceptable limits of ISO 10993-5. Sample 1 viability ranged from 70.62% (stock) to 89.72% (1/8) at 24 h, and from 77.28% to 93.63% at 48 h. Sample 2 consistently outperformed Sample 1, with values from 80.61% to 91.28% at 24 h and from 83.35% to 96.47% at 48 h. DISCUSSION: Both HAP-COL application techniques proved highly biocompatible and compliant with ISO 10993-5 non-cytotoxic safety limits. However, the 3D-printed robocast layer (Sample 2) consistently outperformed the sprayed coating, exhibiting superior osteoblast viability and proliferation. This demonstrates that a layered, biomimetic robocast architecture optimizes cell survival and successfully mitigates the bio-inert properties of standard titanium. CONCLUSIONS: The 3D-printed HAP-COL coating produced by robocasting exhibited superior biocompatibility and osteoconductive behavior compared with the sprayed alternative, supporting sustained osteoblast proliferation. HAP-COL robocast layers on titanium represent promising candidates for personalized orbital wall reconstruction, although in vivo validation remains necessary.