CRANIOFACIAL AND DENTAL TISSUE - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 189

Table 9.2 Osteoconductive scaffolds

Type Graft Osteoconduction Osteoinduction Osteogenesis Advantages

Bone Autograft 3 2 2 “Gold standard”

Allograft 3 1 0 Availability in

many forms

Biomaterials DBM 1 2 0 Supplies

osteoinductive
BMPs, bone graft
extender

Collagen 2 0 0 Good as delivery

vehicle system

Ceramics TCP,

hydroxyapatite

1 0 0 Biocompatible

Calcium
phosphate
cement (CPC)

1 0 0 Some initial

structural support

Composite grafts b -TCP/BMA
composite

3 2 2 Amply supply

— 3 — Potentially limitless
supply
Score: 0 (none) to 3 (excellent). DBM: demineralised bone matrix, TCP: tricalcium phosphate, BMA: bone marrow aspirate,
BMP: bone morphogenetic protein

BMP/synthetic
composite

bones are fixated with screws and plates to avoid malunion, malocclusion, and fibrous (rather than
boney) healing. Likewise, when a bone defect is large enough (critical-size or larger), it will heal
by fibrous scar formation. In critical-size defects, a nonvascularized bone graft from the iliac crest,
tibial plateau, outer table of the calvarium, or olecranon can be employed to fill the gap. Allografts
(e.g . , demineralized freeze-dried bone), xenografts (coral), metals (titanium), and alloplasts (e.g.,
hydroxyapatite, methylmethacrylate) are also occasionally used (see Section 9.4.1 ); however, cau-
tion is employed because of the risks of nonunion, infection, and extrusion. When a defect > 6 cm is
encountered or the wound is compromised (i.e . , irradiated tissues), then a vascularized bone graft of
radius, fibula, rib, or iliac crest is used ( Franklin et al., 1980; Song et al., 1982; Taylor, 1983; Taylor
et al., 1975, 1979 ). Large maxillary defects are often filled with an obturator (a removable prosthetic)
or a vascularized soft tissue flap; however, soft tissue is not ideal since it can result in asymmetry
and contour abnormalities, and will not be able to accept osseointegrated implants for dental recon-
struction ( Hanasono et al., 2010 ). Furthermore, autogenous bone or soft tissue grafts have significant
drawbacks: limited supply; inaccuracy in the 3D shaping and inset; and their need for increased op-
erative time, larger surgical teams, more equipment, and extra operative site with its complications
( Ling and Peng, 2012 ).
Patients with craniofacial hypoplasia are treated with distraction osteogenesis, where osteotomies
(bone fractures) are iatrogenically made of the involved bones, and a device is applied that will distract