| Four distinct studies aimed at ascertaining the effects of scaffold architectural parameters on bone ingrowth were carried out using rapid prototyping and controlled laser-sintering techniques: (1) Two configurations of hydroxyapatite implants with predetermined geometries and internal architectures were fabricated with systematically varied void volumes via 3-dimensional printing and evaluated at two time points. Data was analyzed as a 2 x 2 factorial and revealed that the two void volumes and times both affected the bone and soft tissue ingrowth responses. However, the responses were found to be non-linear, especially at low values of time. Higher amounts of bone were detected in the samples that contained side channels with increased void volume. (2) Six different architectures along a systematically varied scale were tested at 8 and 16 weeks and analyzed with a two-way analysis of variance. A new rapid prototyping technique for making structures with controlled geometries called "robocasting" was used in their construction. Once more, a non-linear bone and soft tissue response to void volume was detected, with the intermediate void volumes exhibiting the highest degree of bone ingrowth. (3) Two configurations of hydroxyapatite bone fillers with controlled geometries made via 3-dimensional printing were evaluated in a rabbit femoral canal model. Neither sample type exhibited extraordinary bone ingrowth, though the possible presence of de novo bone formation in blind end channels was revealed. (4) Endosseous dental implants with controlled laser-textured collar surfaces were implanted in the mandibles of dogs. Collars contained a lower texture of 12- x 12- for the facilitation of bone tissue apposition and an upper texture of 8- x 8- for soft tissue attachment. Samples were tested against smooth collar surfaces. Textured collars revealed the formation of a stable biologic width whereas smooth collars exhibited large amounts of epithelial downgrowth and bone resorption. Taken together, the data presented here offers alternative methods to evaluating scaffold and surface architectures in a systematic fashion for definitively determining isolated parameter effects on bone ingrowth. |
