Alloplastic bone implants and bone-substitution materials

by **Supra Chan** Fri Jun 18, 2010 4:00 pm

Alloplastic bone implants and bone-substitution materials

Category: Implantology
Chapter: Materials for bone substitution and augmentation

Editors


created	IMC	19.03.2008
last changed	Frank Jünger	31.03.2009

Definition

Alloplastic materials

These are biological materials either manufactured completely synthetically, or produced by extensive physical or chemical processing of xenogeneic (not species-related) types of tissue and/or structures.

Requirements for alloplastic materials

They should be complex systems (drug delivery systems). These are composed from a basic substance, the carrier substance, and the active substances transported by the latter.
Carriers are materials without active factors. They can be produced from organic tissues as well as from synthetic structures.
Carriers should hold a limited amount of the active substances for a limited period of time and make them available for local requirements (Hollinger and Leong 1996).
At the same time, carriers should function as bone-substitution material (Zellin and Linde 1997) with a definable absorption and transformation rate.
They should enable characterization of their biochemical, physical and pharmacological properties and must be biocompatible.
The long-term tolerability also affects degradation products that are produced at the time of decomposition.
The decisive factor with regard to the osteoconductive effect of the carrier is the synchronization between the carrier's decomposition rate and the bone's growth rate (Hutmacher et al. 1998)

Classification into biological material groups

Natural organic and anorganic materials

Materials of animal origin

Navigraft

Spongiosa Transplant
Processed bovine cancellous bone

Bio-Oss

Spongiosa Granulate
Natural bovine bone granulate

Bio-Oss

Spongiosa Block
Natural bovine bone granulate

Bio-Oss

Collagen
Natural bovine bone mineral containing 10% (V/V) collagen fibers (pig)

BioGen C

, BioGen S

, BioGen Mix

Natural equine bone mineral (cancellous, cortical, mixture)

BioGen B

Natural equine bone mineral

Collagen

Collagen I is the main component (90%) of the organic bone matrix. Type I collagen binds osteoblasts via specific receptors (Basle et al. 1998).

Targobone

Collagen lyophilizate of bovine origin, contains the antibiotic teicoplanin

Colloss

Collagen lyophilizate of bovine origin

Hydroxyapatite

Osteograf

N-300/N-700
Natural bovine hydroxyapatite

Bio-Oss

Corticalis
Natural bovine hydroxyapatite
Materials of plant origin

Frios

Algipore
Bone-analogous highly porous calcium phosphate as biological hydroxyapatite (origin: algal species)

Biocoral

Natural crystalline calcium carbonate in aragonite structure from corals. The natural anorganic skeleton remains intact. The pore size is 250-750 µm.

Synthetic anorganic materials

HTR Bioplant

Slowly absorbable copolymer, consisting of poly methyl methacrylate ("PMMA") and poly hydroxy ethyl methacrylate ("PHEMA") with an extremely thin layer of barium sulfate for radiopacity and a border area of calcium hydroxide/calcium carbonate.

Tricalcium phosphate [Ca3(PO4)2]

Cerasorb

Synthetic, phase-pure ß-tricalcium phosphate

KSI tricalcium phosphate

Synthetic, phase-pure ß-tricalcium phosphate

chroOs&tm;
Synthetic, phase-pure ß-tricalcium phosphate

BioResorb

Synthetic, phase-pure ß-tricalcium phosphate

Ossaplat

Synthetic, phase-pure ß-tricalcium phosphate

This material is still disputed. On the one hand, TCP was inserted into one of two skull bone defects in a study and compared to the untreated opposing side after 6 months of unloaded healing. The untreated opposing side had almost completely regenerated bone. After 6 months, the TCP was not decomposed, the individual granules were covered by a fibrous layer without osteoblasts (Handschel et al. 2002).

In another study, tricalcium phosphate and autologous bone were used bilaterally for sinus augmentation in 4 patients, though for each patient an additional onlay graft was required. The bone biopsies showed no lateral difference after 6 months (Szabo et al. 2001).

Synthetic organic materials

Polylactic and polyglycolic acids

Fisiograft
Synthetic copolymerized polyglycolic acid (PGA) and polylactic acid (PLA) in a 1:1 ratio

Advantages:
Studies with animals and clinical studies had promising results when used both as bone substitution material and as carriers for proteins and growth factors (Peter et al. 1998, Hutmacher DW 2000).

Disadvantages:
The hydrolytic decomposition of the material leads to a local acidulation of the tissue and causes an inflammatory reaction during absorption (Martin et al. 1996).

Glass ceramic or bioglass

Biogran&tm;

Synthetic composition of Si, Ca Na, P

Absorbable bioactive glass is an excellent material for the stimulation and transport of cells and molecules needed for the formation of bone (Ducheyne et Qiu 1999).

Composite materials

PepGen P-15&tm;
Synthetic peptide with natural bovine hydroxyapatite

PepGen P-15&tm; Flow
Synthetic peptide with natural hydroxyapatite carrier in a hydrogel from sodium carboxy methyl cellulose, glycerol and water.

Overview

Bone substitution materialsAvailabilityEffectAdvantagesDisadvantages

Allogens	Almost unlimited availability	Osteoconductive after suitable preparation Osteoinductive	Transfer of infectious diseases possible
Xenogens	Free availability	Osteoconductive	Transfer of infectious diseases possible
Bone morphogenetic proteins		Osteoinductive	Suitable carrier substances required

The use of alloplastic bone implants and/or bone substitution materials

Synthetic bone substitution materials

Advantages

Unlimited availability
Unlimited durability
No transfer of pathogens
No immune reaction

Disadvantages

No osteogenesis
No osteoinduction
Questionable osteoconduction
No definable absorption and transformation rates
Different mechanic capacity
Risk of infection with missing bony insertions or build-up

No material is osteoinductive. The material is osteoconductive at most, i.e. it has a guiding structure for the bone build-up (Schlegel and Neukam 2002)

Use of synthetic bone substitution materials

In order to reach a functionally loadable hard-tissue reconstruction, these materials should only be used mixed with bone shavings or bone chips in a 1:1 ratio. In order to avoid connective-tissue incision and subperiosteal movement, a membrane cover is recommendable. When augmented purely, they only lead to a volume expansion of the corresponding alveolar process.

sources

Basle MF, Lesourd M, Grizon F, Pascaretti C, Chappard D (1998) Type I collagen in xenogenic bone material regulates attachment and spreading of osteoblasts over the beta1 integrin subunit Orthopade 27:136-42
Ducheyne P, Qiu Q (1999) Bioactive ceramics: the effect of surface reactivity on bone formation and bone cell function Biomaterials 20:2287-303
Handschel J, Figgener L, Joos U (2001) Forensic evaluation of injuries to nerves and jaw bone after wisdom tooth extraction from the viewpoint of current jurisprudence Mund Kiefer Gesichtschir. 2001 Jan;5(1):44-8
Hollinger J, Leong K (1996) Poly(a-hydroxy acids): carriers for bone morphogenetic proteins Biomaterials 17: 187-194
Hutmacher D, Kirsch A, Ackermann K, Hürzeler M (1998) Matrix and carrier materials for bone growth factors: state of the art and future perspectives Berlin Heidelberg, Springer
Hutmacher DW (2000) Scaffolds in tissue engineering bone and cartilage Biomaterials 21:2529-43
Martin C, Winet H, Bao JY (1996) Acidity near eroding polylactide-polyglycolide in vitro and in vivo in rabbit tibial bone chambers Biomaterials 17:2373-80
Peter SJ, Miller MJ, Yasko AW, Yaszemski MJ, Mikos AG (1998) Polymer concepts in tissue engineering J Biomed Mater Res 43:422-7
Schlegel KA, Neukam FW (2002) Augmentationen, Knochenersatzmaterialien, Membranen Curriculum Zahnärztliche Chirurgie Band 1
Szabo G, Suba Z, Hrabak K, Barabas J, Nemeth Z (2001), Autogenous bone versus beta-tricalcium phosphate graft alone for bilateral sinus elevations (2- and 3-dimensional computed tomographic, histologic, and histomorphometric evaluations): preliminary results, Int J Oral Maxillofac Implants 16:681-92
Zellin G, Linde A (1997), Importance of delivery systems for growth-stimulatory factors in combination with osteopromotive membranes. An experimental study using rhBMP-2 in rat mandibular defects, J Biomed Mater Res 35:181-190

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