Alloplastic Augmentation of the Facial Skeleton

What is a biomaterial?

The National Institute of Health defines biomaterial as, “Any substance or combination of substances, other than drugs, synthetic or natural in origin, which can be used for any period of time, which augments or replaces partially or totally any tissue, organ or function of the body, in order to maintain or improve the quality of life of the individual.”

What are the characteristics of “the ideal implant”?

1. Inert, causes no foreign-body reaction

2. Resistant to infection

3. Sterilizable

4. No donor site morbidity

5. Nontoxic, noncarcinogenic

6. No resorption

7. Simplifies procedure (time, complexity)

Under what circumstances is autologous tissue preferred over alloplasts?

1. Lack of soft tissue coverage

2. Radiation

3. Compromised vascularity

4. Poor quality of surrounding tissue

Why are the long-term results of autologous bone grafting disappointing in the facial skeleton?

The fate of onlay bone graft is unpredictable due to resorption and factors that impact its subsequent remodeling. Revascularization of the bone graft makes it susceptible to osteoclast activity, resulting in resorption and volume loss. The functional stresses that the recipient site places on the bone graft, determined by regional musculoskeletal forces and deforming forces of the overlying soft tissue envelope, impact the volume persistence of onlay bone grafts.

What are the main classes of biomaterials used in pediatric craniofacial applications?

1. Ceramics and bioactive glass

2. Biodegradable polymers

3. Prefabricated polymers

Name examples of ceramics.

1. Hydroxyapatite

2. Calcium phosphate

Which biomaterial is designed to be replaced by bone?

Bioactive glass is both osteoconductive and osteoinductive.

What is osteoconduction?

Osteoconduction refers to the ability of a material to serve as a scaffold and allow ingrowth of osteoblasts and gradual formation of osseous tissue.

What is osteoinduction?

Osteoinduction is the process by which primitive, undifferentiated pluripotent cells are stimulated to develop into the bone-forming cell lineage.

Name examples of biodegradable polymers.

1. Poly(lactic acid) (PLA)

2. Poly(glycolic acid) (PGA)

3. Poly(lactic-co-glycolic acid) (PLGA) (combination of PLA and PGA)

Name examples of prefabricated polymers.

1. Porous polyethylene (Omnipore; Matrix Surgical, Atlanta, GA; Medpor; Stryker, Kalamazoo, MI)

2. Polymethyl methacrylate (Hard-Tissue Replacement [HTR] polymer; Biomet, Jacksonville, FL)

In what ways can biomaterials be placed in the facial skeleton?

As nonload bearing inlay or onlay for facial augmentation.

What criteria are used to decide whether autologous bone or biomaterials is to be used in the pediatric craniofacial skeleton?

1. Skeletal maturity.

2. Requirement for inlay or onlay reconstruction.

3. Requirement for load-bearing reconstruction.

What is an appropriate choice of materials if skeletal growth is less than 90% complete, and the reconstruction needs to grow with the developing craniofacial skeleton?