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MATERIALS USED IN

MAXILLOFACIAL PROSTHESIS

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Introduction Definition History Review of literature Maxillofacial Impression materials and

advancements Maxillofacial Prosthetic Materials

Auxillary Maxillofacial Materials

Discussion

Conclusion

Reference

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INTRODUCTION

Facial defects can result from trauma, treatment

of neoplasm’s, or congenital malformations. More

often facial defects referred to the Prosthodontist for

restorations are usually the result of surgical resection

of tumors. Restoration of facial defects is a difficult

challenge for both the surgeon and the Prosthodontist.

Both surgical reconstructions and Prosthodontic

restoration have distinct limitations.

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The surgeon is limited by the availability of

tissue, the compromise of the local vascular bed

by radiation in tumor patients, the need for

periodic visual inspections of an oncology

defects and the physical condition of the patient.

The Prosthodontist is limited by the inadequate

materials available for facial restoration,

movable tissue bed, difficulty in retaining large

prosthesis and patient acceptance.

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Maxillofacial prosthesis :-

Any prosthesis used to replace part or all

of the stomatognathic and/or craniofacial

structures

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There are two ways of presenting an

overview of the subspecialty of maxillofacial

prosthesis. One way is by viewing the patient

‘being treated’ and the other is by the ‘type of

prosthesis’ that is prepared for the patient.

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I ) Patient wise, they are classified as:

1. Surgical - The defect to be restored was created by a definitive surgical procedure. Ex: Cancer patients

2. Congenital - The defect is a result of congenital or developmental anomaly. Ex: cleft lip /palate and syndromes of head and neck.

3. Traumatic - The defect of the head and neck is a result of a traumatic experience in automobile accidents, industrial accidents or suicidal attempts.

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II) By type of prosthesis, they can be classified as:

1. Extra oral - Facial restorations. Ex: Nasal

prosthesis, orbital, ocular auricular

2. Intra oral. Ex: Obturator, speech aids,

modified complete or partial dentures and

infant feeding prosthesis.

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HISTORY:HISTORY:

Even before dentistry attained its status

as a profession, some surgeons had recognized

the limitations inherent in grafting tissue for

repair of certain maxillofacial deficiencies and

had argued the use of prosthesis as an alternate

method.

Artificial eye and foot found in Egyptian

mummy, the use of artificial eye and noses by

the Indians and the Chinese lead us to think that

they applied their skill to prosthetic restoration

also.

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BEFORE 1600 ADBEFORE 1600 AD

Ambroise pare, (1510-1590) the famous

French surgeon appears to be the first medical

writer on this subject. He recommended a

prosthetic nose, which could be made of gold,

silver, paper and linen cloth glued together. He also

described the fabrication of an auricular prosthesis.

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1600-18001600-1800

Maxillofacial prosthetics owes much to

Pierre fauchard (1678-1761). Fauchard made a

monumental contribution to prosthetic facial

reconstruction, he made a silver mask to replace

the lost portion of the mandible for a french

soldier. This prosthesis was constructed under the

direction of a military surgeon, in collaboration

with a silversmith for french artillery. The victim

later came to be known as the “GUNNER WITH

THE SILVER MASK”.

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1800-19001800-1900

William Morton (1819-1868) also did some

pioneer work is Maxillofacial prosthetics. He

constructed a nose out of porcelain for a Boston

lady who had lost her own from a malignant

disease. Dr. Morton attached the nose to her

spectacles.

Frenchman Claude martin published a

book in 1819 and described using a ceramic

material to fabricate a nasal prosthesis.

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1900-19401900-1940

Upham (1901), a Boston dentist described

the use of vulcanite rubber for the fabrication of

nasal and auricular prosthesis.

In time, however some workers showed

dissatisfaction with vulcanite due to their poor

color stability, translucency and rigidity.

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In Germany (1913), the gelatin - Glycerin

compounds attracted much attention due to their

ease to manipulate, pliability, translucency and

adaptability of intrinsic coloring to match the

skin. But this material lasted only a few days or a

week.

Bulbulian Clarke then introduced

prevulcanized latex which was used with water

soluable dyes.

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1940-19601940-1960

Acrylic resin polymers were introduced and

replaced older vulcanite rubber. Its translucency,

colorability and ease of processing was

attractive to most clinicians. Transparent

photographic paints, acrylic resin polymer stains,

water color, oil colors were also used.

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1960- 19701960- 1970

Silicone elastomers were introduced

Barnhard was the first to use silicone and

coloring the facial prosthesis by combining a

silicone rubber base material with acrylic resin

polymer stains. Tashma used dry earth

pigments.. Schaaf described the use of artist oil

paint. Fine described the use of colored nylon

flocking

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1970-19901970-1990

Different types of elastomers came into market.

Lontz – polysiloxane elastomers

Gonzalez - polyurethane elastomers

Lewis - Siphenylenes

Turner - isophorone polyurethane

Drane and udagama - Silastic medical adhesive

silicone type A

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1990- to present1990- to present

Advances in polymer chemistry has renewed

interest in developing new materials

Gentleman-polyphosphazenes

Silicone block polymers

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REVIEW OF LITERATURE

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Aziz T, Waters M, Jagger R J. Biomed Mater

Res B Appl Biomater. 2003; 65 :252. Development

of a new poly(dimethylsiloxane) maxillofacial

prosthetic material.

A new poly(dimethylsiloxane) material with

improved mechanical properties was compared to

commercially available materials. The formulations

developed were based on condensation chemistry

containing a hydroxy-end-blocked

poly(dimethylsiloxane), hydrophobic silica filler,

silane cross-linking agents, and a tin catalyst.

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A formulation was developed with a base

polymer mix of 80%:20% high- to low-molecular-

weight polymers into which 20% w/w filler was

added. This formulation had a tear strength

better than compared to the commercial

materials

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Bellamy KE, Waters MG. Biomed Mater Eng. 2005;15:21-7. Designing a prosthesis to simulate the elastic properties of skin.

They discussed a three-layered maxillofacial prosthesis consisting of a silicone rubber base layer, an inner gel layer and an outer polymeric coating (to simulate the elastic properties of skin). Gels were made by the addition of both low and high molecular weight unreactive silicone fluids. The results of the study shows that the gel produced, closely simulates the elastic properties of skin when bonded to a base silicone rubber layer. Further clinical trials are needed.

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FOR MODELING OF AN EXTRA-ORAL IMPRESSION

• Conventional method (using impression material)

• CT and MRI

• 3-D optical scanner (light source)

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IMPRESSION MATERIALS

PLASTER OF PARIS

Highly accurate in reproducing details

But it is lengthy and time consuming technique.

Used mainly to reinforce alginate impression.

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RUBBER BASE IMPRESSION MATERIAL

Provides good details

Mainly for intra oral use

Expensive

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ALGINATE

Most widely used

Excellent reproduction of details

Overall cost is reasonable

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Disadvantage of conventional impression

Discomfort to the patient.

Deformation of the soft tissue because of the

weight caused by the impression material.

Master cast for the reconstruction of the orbital

defects usually show the remaining eye closed,

so the technician must rely on other data (e.g.-

photographs) for the design of the orbital

structures.

Testing ability of the clinician.

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CT AND MRI

The difficulties encountered while using

impression material was overcome by the use of

CT AND MRI

CT AND MRI scan the defect area and a CAD

model of the defective area and the prosthesis

pattern is designed. The prosthesis pattern is

obtained by a procedure known as rapid

prototyping.

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Disadvantage

Radiation is more with CT

Length of the time that the patient is required to

be exposed and remain motionless- during MRI

scanning

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OPTICAL THREE DIMENSIONAL SCANNER

Newer device used to scan the facial defect

and reproduce a model

It is a mobile multi-view 3D measuring

system based on self calibration projection

technology.

It facilitate the fully automatic recording of

the body parts from various direction in one

measuring process

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A transmission grating with parallel lines

inside the projector produced a fringe pattern on

the face

These pattern are recorded by camera and

transmitted to the PC

The generated CAD model is converted

into a physical model by means of a rapid

prototyping procedure.

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ADVANTAGE

The body parts are exposed to light and

recorded optically.

Time taken for measurement-10 to 20 seconds.

Accuracy- 100µm.

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RAPID PROTOTYPING

Rapid prototyping, operate on the principle

of depositing materials in layers or slices to build

up a model rather than forming a model from a

solid block. The use of a CT OR MRI allows

parts of the body to be serially recorded slice by

slice. Similarly, an object can be reproduced

slice by slice using the three dimensional

computed data in conjunction with a rapid

prototyping machine

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STEREOLITHIOGRAPHY

It is a method of rapid prototyping that

uses data obtained from CT OR MRI scan

stored in 3-dimensional form

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Works based on the principle of curing liquid photomer into specific shape

A vat which can be lowered and raised filled with photocurable liquid acrylate polymer

Laser generating U-V beam is focused in x-y directions

The beam cures the portion of photo polymer and produces a solid body

This process is repeated till the level b is reached as shown in the figure

Now the plat form is lowered by distance ab

Then another portion of the cylinder is shaped till the portion is reached

STEREOLITHIOGRAPHY

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MATERIALS USED IN MAXILLOFACIAL

PROSTHESIS

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Generally an ideal material should have the following characteristics –

Non-toxic. Odorless. High tear strength. High edge strength. Ease of processing. Dimensionally stable during and after processing. Ease of intrinsic and extrinsic coloring with

commercially available colorants. Ease of repair and refabrication if needed.

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Chemically inert after processing.

Non-porous after processing.

Long shelf life.

Long working time.

No water sorption.

Translucent.

Softness compatible to tissue.

Usable life of two years or more.

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A number of materials are available and have been used for facial prosthesis. The materials currently in use are:

I. ACRYLIC RESINS

The material is readily available and most dentists are familiar with its physical to chemical properties and processing techniques. These materials can be successfully employed in specific types of facial defects particularly those in which little movement occurs in the tissue bed during function.

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Heat polymerizing MMA is preferred over

the autopolymerizing form because of the

presence of free toxic tertiary amines in the later.

Facial prosthesis made of this material remains

serviceable up to 2 years but required

occasional repainting of the surface. With age,

however the prosthesis becomes shiny and

crazing is noted.

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Advantages:

a. Both intrinsic and extrinsic coloration can be

performed.

b. Has good edge strength

c. Alterations can be easily affected.

d. Compatible with most adhesive systems

e. Color stability is good in heat polymerized MMA.

f. Can be easily relined with tissue conditioner of

denture liner.

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Disadvantages:

a) Rigidity, therefore its usefulness is

compromised in highly movable tissue beds

leading discomfort and expose of margins.

b) High thermal conductivity.

c) Duplication is not possible because of

destruction of the mould during removal from

flasks.

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II. ACRYLIC CO-POLYMERS

Conta and Hildested did extensive study on this material but did not receive wide acceptance, despite being soft and elastic because of a number of objectionable properties like poor edge strength, poor durability, degradation when exposed to sunlight.

Disadvantages:

Processing and Coloration are difficult.

The completed restoration often tacky, predisposing to dust collection and staining

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III. VINYL POLYMERS AND COPOLYMERS

a. Commonly marketed as (Realistic and Mediplast, prototype III)

Is a flexible plastic material basically plasticized polyvinyl Chlorides (PVC) or copolymer of Polyvinyl acetate.

The primary deficiency arises from the leaching of the plasticizer and resulting hardening of the prosthesis.

The lifespan as reported by Castleberry (1973) has been extended to 9-11 months.

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Advantages:

Adaptable to both extrinsic and intrinsic

coloration.

Flexible.

Disadvantages:

Migration of plasticizer leading to discoloration

and hardening.

Easily get stained when exposed to ultra-violet

light, peroxide and ozone.

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Poor edge strength.

Tend to absorb sebaceous secretions,

cosmetics and solvents.

They soil easily because of surface tackiness.

Metal moulds are required, as curing is

accomplished at high temperatures

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IV. POLYURETHANE ELASTOMERS:

(Epithane - 3)

These elastomers are called so because they

contain urethane linkages. They arise from two

major reactants. In the presence of a catalyst, a

polymer terminating with an isocynate is combined

with one terminating with a hydroxyl group. Varying

the amount of isocynate will change the physical

properties of the final product.

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They are quite elastic and flexible

especially well suited to defects with movable

tissue bed.

Isocynate are moisture sensitive and when

water contamination occurs, gas bubbles causes

defects and poor curing of the material. The

reaction must be carried out in a dry

atmosphere. The processing temperature is

100o C.

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Advantages:

Good edge strength.

Can be colored both intrinsically and

extrinsically.

Superior cosmetic results when compared to

other materials currently available.

Stone molds are acceptable but care should be

taken to thoroughly dehydrate before

processing.

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Disadvantages:

Difficult to process consistency.

Isocyanides, as these compounds are toxic and

moisture sensitive due to which gas bubbles can

accumulate and cause defects and poor curing.

Extrinsic coloration tends to wear off rapidly.

Clinically, the life range from minimum 3 months

to maximum 6 months.

Poor compatibility with existing adhesive

systems.

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V. SILICONE ELASTOMER

The silicones are probably the most widely used

materials for facial restoration. Silicones are a

combination of organic and inorganic

compounds. The first step in their production is

the reduction of silica to elemental silicon. Then

by various reactions the silicone is combined

with methyl chloride to form dimethyl

dichlorosixane, which when it reacts with water

forms a polymer.

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These polymers are translucent, watery

white fluids whose viscosity is determined by

length of the polymer chain. Polydimethyl

Siloxane commonly referred to as silicone is

made from these silicone fluid polymers. Most

rubbery forms are compounded with fillers that

provide additional strength. Additives are used to

provide color. Antioxidants and vulcanizing

agents are used to transform the raw mass from

or plastic to a rubbery -resin during processing.

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The long-chained polymer which is cross-

linked create a network that can be separated

only with difficulty. This network makes the

silicones especially resistant to degradation from

UV light exposure.

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The process of cross-linking the polymers

is referred to as vulcanization. Vulcanization

occurs both with and without heat and depends

on the catalytic or cross-linking agents utilized.

Depending on the method of vulcanization, two

forms are available:

1. Those that require heat - Heat vulcanized

(HTV)

2. Those that vulcanize at room temperature-

Room temperature vulcanized (RTV)

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Silicones are classified into four groups according

to their application

1. Implant grade- material that can be implanted

interstitially.

2. Medical grade- for external use eg-

maxillofacial silicones.

3. Clean grade.

4. Industrial grade- both are used for industrial

application.

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Heat Vulcanized Silicones (HTV):

Supplied as one component or two component putty.

The catalyst or vulcanizing agent is

dichlorobenzoyl peroxide or platinum salt,

depending on the type of polymerization.

Various amounts of filler are added to these

polymers depending on the degree of hardness,

strength and elongation desired. The more filler, the

harder and less resilient the compounded rubber will

be.

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The filler is very pure finely divided silica

with a particle size of about 30.

Co-Polymers like methyl vinyl or methyl

phenyl siloxy radical are added for softness

and tear strength.

Advantages:

a. Exhibit excellent thermal stability.

b. Color stable.

c. Biologically inert.

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Disadvantages:

a. Do not posses sufficient elasticity to function in

movable tissue bed.

b. Poor edge strength.

c. Are opaque and have lifeless appearance.

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Room temperature silicones (RTV)

It is a viscous silicone polymer that

includes a filler and catalyst, which also acts as

cross-linking agent.

Stannous octoate is the common catalyst

used.

Filler, like diatomaceous earth are added

to increase strength.

The properties of RTV are similar to the

HTV types, except for the ease of processing of

RTV’s.

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Advantages:

Same as HIV Silicones.

Easy to process and stone molds can be used.

Disadvantages:

Same as HTV silicones except for its ease in

processing.

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FOAMING SILICONES

It is a form of RTV silicone. They reduce the weight of prosthesis because of formation of bubbles within the mass.

The basic silicone has an additive so that a gas is released, when catalyst stannous octoate is introduced. The gas forms bubbles within the vulcanizing silicone. After the silicone is processed, the gas is eventually released leaving a spongy material. And the formation of bubbles within the mass can cause the volume to increase by as much as seven times.

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DISADVANTAGE

Has reduced strength.

Susceptible to tearing.

Because of these problems its use is limited.

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VI. SIPHENYLENES: (polytetramethylsiphenylenesiloxanedimethylsiloxane)

These belong to silicone family that contain methyl and phenyl group.

It is a pourable, viscous, room temperature vulcanizing liquid.

Three component kit

Consist of a base resin

crosslinking agent- tetrapropoxysilane

catalyist- organotin

Siphenylenes elastomers feels like skin.

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Are biocompatible, resistance to degradation on exposure to ultraviolet light and heat.

Have good edge strength and colorability.

Advantage:

Edge strength and colorability is superior to silicones.

Disadvantages:

Not enough clinical trials have been done due to limited research on this material.

High cost.

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SILICONE BLOCK POLYMERS

Developed to improve some of the weakness of

silicone elastomers.

Incorporates poly methyl methacrlyate into

silicone block.

Has been found to be more tear resistant than

conventional cross linked silicone polymers.

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POLYPHOSPHAZENES

It has been developed for resilient denture

liner.

Properties of this material is been modified

to satisfy the requirements for fabrication of

maxillofacial material.

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AUXILLARY MAXILLOFACIAL MATERIALS:

Primers

These are used to promote bonding of silicone and other maxillofacial material.

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FACIAL PROSTHETIC

ADHESIVES

Facial prosthesis

may be retained by

mechanical means or

by the use of

adhesives.

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No one adhesive will behave in the same

way to different patient. This mainly due to

adhesive reacting to various skin types, ie oily,

dry, flaky etc and each skin type will exhibit

varying degree of retention.

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They can be classified as

Pastes. (PSA 1)

Liquids [paintable (pros-Aide, DC-355) or

spray-on (DC MED)].

Double sided tapes( 3M biface tape).

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TISSUE CONDITIONING

Used to prevents the skin damage when

removing the adhesives. It forms a protective

barrier.

Comfeel protective film

It contains ethoxyethyl acid co-polymer ethyl

acetate

When applied it forms a chemical film that is

compatible with adhesives, so increasing the

adhesion qualities of the prosthesis to the skin

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Skin prep protective dressing (Smith & Nephew

Inc) are used to enhance the prosthesis

adhesion and to protect the skin from trauma.

Composition

Isopropyl alcohol.

Butyl esters of poly vinyl methacrylate/ methyl

methacrylate copolymer.

Acteyl tributyl citrate

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Technique of application of adhesives

Apply the adhesive to 6 to 7mm of the

periphery of the fitting surface

To prevent the break down of the fine thin

edges, leave the last 4mm without any

adhesives, instead Vaseline may be applied to

them to make the margin disappear

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ADHESIVE REMOVER

The biggest

problem as far as the

patient is concerned is

the removal of the

remaining residual

adhesive from the skin.

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Plaster remover.

Zoff prosthetic cleanser. Trichloroethane

Thackeray cleanser.

Acetone.

Krylon medican spirit gum remover

Uni-solve adhesive remover

Isoparaffin.

Isopropyl alcohol.

Dipropylene glycol methyl ether.

Aloe extract.

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Technique of removal

To remove the prosthesis

Lift the edge using a cotton bud or gauze

soaked in the remover, slowly working around

and under the fitting surface, lifting the

prosthesis away from the skin as you go.

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To clean the adhesive from the skin

Soak a piece of gauze in the remover and

by gently rubbing and turning the gauze

constantly. Finish off by washing with soap and

water.

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To clean the prosthesis

Initially rub the thumb over the fitting

surface, causing the adhesive to “ball” for easy

removal. Finally use the gauze soaked in

remover to clean the fitting surface.

If still traces of adhesive remain soak the

prosthesis in the solvent for one or two minutes

and then use a gauze swab.

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DISCUSSION

Since the sixteenth century acquired surgical

defects have been restored by prosthetic

replacements constructed from a variety of

materials and techniques. The cosmetic and

functional disabilities following radical surgery for

oral and paraoral cancer are significant and

disabling. Definitive reconstruction should be

performed wherever possible as part of the

ablative procedure.

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When definitive reconstruction is

coordinated and combined with maxillofacial

prosthetic rehabilitation, head and neck defects

can be restored to near-normal function and

appearance in many cases. The traditional

concept of a one-time prosthesis that supplies the

patient's requirements through the course of life

is no longer realistic or valid.

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Identification of the variable factors that

influence the serviceability of prostheses for the

treatment of jaw defects is important and useful

information for the patient, the family of the

patient, the rehabilitative team, and third-party

payers.

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CONCLUSION

Jaw defects affect many vital functions

(that is, respiration, mastication, deglutition,

speech, and aesthetics). Ideally, any anatomic

defect should be surgically reconstructed.

However, when surgical reconstruction is

contraindicated, prosthetic reconstruction must

be employed to restore anatomy, function, and

aesthetics.

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Effective communication between the

surgeon and the maxillofacial Prosthodontist is

essential for developing a realistic treatment plan

or rehabilitation of patients undergoing resection.

Preoperative consultations allow the

prosthodontist to make recommendations to the

surgeon to achieve better prosthetic results.

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The team concept, in which the head and

neck surgeon, speech pathologist, radiation

oncologist, maxillofacial Prosthodontist, and

other members of the health profession function

together in planning the rehabilitation and

primary modes of therapy, ensures the patient's

early and successful rehabilitation

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REFERENCE Maxillo Facial Rehabilitation – Prosthodontic and

surgical consideration.

JOHN BEUMER. Clinical Maxillofacial Prosthetics -

THOMAS D. TAYLOR. Prosthetic rehabilitation-

KEITH F THOMAS.

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