MATERIALS IN

MAXILLOFACIAL

PROSTHODONTICS

CONTENT

s

.

INTRODUCTION

In evolving a successful prosthetic facial

replacement ,3 factors are necessary:

1. Creative ability

2. Technical knowledge, &

3. Materials which will allow the prosthodontist

to fully exploit these talents.

Objectives Of Maxillo-facial

Prostheses

Restoration of esthetics or cosmetic appearance of

the patient

Restoration of function

Protection of tissues

Therapeutic or healing effect

Psychologic therapy

CHALIAN,

MATERIALS

Ideal Requisites Of Maxillo-facial Materials……

1. Biocompatibility

2. Flexibility

3. Color and translucency

4. Chemical and environmental stability

5. Thermal conductivity

BEUMER, CHALIAN

6. Ease of Processing

7. Strength –

8. Ease of duplication

9. Weight

10.Dimensional stability

BEUMER, CHALIAN

Processing Characteristics-1.Low Viscosity at

ambient temperature

2. Intrinsic and extrinsic Coloration possible

3.Low Solubility parameter

4. Sufficient working time

5. Low curing temperature

Performance Characteristic(mechanical and

physical properties)

Tensile strength

Tensile modulus

Tear resistance

Surface hardness

JPD 1984:51;521-523

Criteria For Maxillo-facial Materials

Patient accommodation properties-

• Non allergic• Non-carcinogenic• Chemical and environmental stability• Moderate cost• Hygienic• Easy adherence to living tissue

JPD 1984:51;521-523

Classification

Impression phase Modelling

phase

Fabrication phase

Prosthetic reconstruction

The impression serve 2 purposes:

1. Allows the dentist to accomplish thepreliminary modeling without the patientpresent, which saves chairside time,eliminates unnecessary discomfort to thepatient.

2. Patient education and teaching aids are alsoserved with the resulting model.

Room Temperature Vulcanizing Materials-

Advantages 1. Fine detail obtainable

2. Inherent strength.

3. Easy to obtain.

Disadvantages1. Needs backing.

2. Difficulty in adjusting setting time.

3. Retaining walls needed for confinement of

material.

4. High cost.CHALLIAN

Modeling materials…

Ideal Properties:

• Malleable

• sufficient body and strength

• Should be possible to accept texture into thismaterial which will be imparted to thefinished mold.

• The closer the color of the material to skintone, less visual distortion

LANEY

1. Modeling clay (sculptor’s clay)water based clay , when allowed to dry, becomes a hard stone like substance.

Advantages

Inexpensive

Readily available

Consistency can be adjusted

feathered on the edge

Disadvantages

gray in color, and the color differential

causes visual distortion

Must be kept moist at all times

2. Plaster……• Readily available

• Inexpensive

• Can be shaped or molded in its plastic state

• Easily and quickly prepared for use

Advantages

• Lacks elasticity

• Adding material to build contour is difficult

• Tendency to flake on the surface

• Cannot be used in undercuts

Disadvantages

3. PLASTOLENE…prepared modeling clay with oil base

Advantages

Takes texture well

Always ready for use

Easily malleable

Requires comparatively little care

Keep a feather edge

Disadvantages

more expensive

Color does not match skin tone

seep into stone model and affect the finished product

4. Waxes……

keeps a feather edge

Readily available

Nominal cost

Color similar to skin tone

Advantages

Model must be carved rather than sculpted

Affect the finished product

Brittle when cooled

Disadvantages

Undertaker’s waxes

Properties similar standard dental waxes,except for 2 characteristics:

1. Due to low melting point, body heat allowit to become malleable & modeled quitereadily with the fingers and hands

2. The color is good in relation to skin tissue.

Fabrication phase materials

Extraoral materials – acrylic resin

vinyl chloride polymers

polyurethane

silicone

Intraoral materials -- silicones

poly (methyl methacrylate)

At present silicones and polyurethane materials are considered most desirable - strength, even though both are somewhat difficult to color.

J of Biomedical material research 2004:8(4);349-363

Extra oral materials

1. Poly-methyl methacrylate

- Palamed

2. Polyvinyl polymers and copolymers

- Realastic (poly vinyl chloride)

- Mediplas (polyvinyl acetate chloride)

3. Elastomersa) Polyurethane

- epithane 3

b) Silicone

- HTV

- RTV

BEUMER

1. Acrylic resin

Indications:

Preferred for restoring

defects which require

minimal movements.

e.g. fabrication of

orbital prostheses.

• Useful in cases of

rapidly changing

defects where relining is

mandatory.BEUMER

Advantages

1. Easy to work with & to maintain.2. Durable.3. Easy to reline with a tissue conditioner or reliner.4. Both extrinsic & intrinsic coloring can be

performed.5. Compatible with most adhesive system & can be

cleaned easily.

Disadvantages1. Rigidity

2. Does not have the feel of skin.

3 High thermal conductivity.

4. Poor margin esthetics.

5. Surface gloss present.BEUMER

Palamed

Cross linked co-polymer of methacrylics and acrylics.

Consists of base powders and stain concentrates, solvent liquid.

Shade guide is provided for base shade powders and stain concentrates.

Produces a soft, resilient skin with a spongy central mass, light weight

The sculptured wax is weighed to achieve the recommended ratio according to the weight ratio table.

CHALLIAN, BEUMER

In 1943 Tylman claimed that MMA could be

combined with plasticizer ( PALAMED)

Plasticized MMA resin has been formulated

with a foaming agent.

Palamed must be carefully proportioned

because too much will result in a stiff heavy

unstable product or too little will result in

incomplete filled mold with large pores.

BEUMER

Use of visible light cure resin system in

maxillofacial prosthetics

VLC resins underwent polymerization without substantial exothermic reaction. Biologic testing indicated–

they are non toxic & biocompatible.

Useful in the replacement of large full-thickness defects in the cranium & other regions.

Also used in mandibular augmentation

Advantages :

2. VINYL POLYMERS & COPOLYMERS

Most widely used plastics for fabrication of MFP

Copolymers of vinyl chloride & vinyl acetate

Properties are superior to those of natural rubbers in flexibility & resistance to sunlight & aging

Clinical usefulness may extend from 1-6 months

Vinyl plastisol

Introduced in 1940.

Vinyl resins are relatively rigid in their pure state,made flexible by addition of plasticizers.

In its plastisol stage the material is a thick liquidformed by dispersion of small vinyl particles inplasticizer

BEUMER

Advantages1. Inexpensive & easy to manipulate2. Can be remade by resoftening & reheating.3. Hydrophilic properties.

Disadvantages

1. Prosthesis made from plastisol looses itsflexibility with aging & become hard &distorted.

2. Degradation & destruction by UV light.3. Linotype Metal molds are used which are

expensive.4. Stains easily

BEUMER

3. Elastomers

Elastomers have been used for over 50 years now to fabricate facial prostheses for individuals missing facial anatomy due to resection, trauma or

even congenital anomalies.

BEUMER

a) Polyurethane elastomer • ……But only

Epithane-3 facial restorations.

3 component systemPart A - polyol Part B- isocyanatePart C- initiator such as dibutyltin dilaurate or

stannous octate)

Varying amount of isocyanates will change the physical properties of final products.

BEUMER

ADVANTAGES

- They can be made elastic without compromising edgestrength.

- Flexibility well suited to defects with movable tissuebeds

- Colored extrinsically & intrinsically

- Superior cosmetic results.

DISADVANTAGES

- Difficult to process consistently

- Isocyanate is moisture sensitive & toxic

- The presence of moisture in the air, leads toproduction of CO₂ resulting in porous elastomer.

BEUMER

Water contamination is difficult to control

Requires thorough dehydration before processing if stone molds are used

Poor compatibility with existing adhesive systems

Difficulty in clearing adhesive from prosthesis.

Not color stable.

Clinical usefulness less than 6 months ( approx. 3mths.)

BEUMER

Silicone Elastomer

• Properties of silicone

• Disadvantages of silicone

• Classification of silicone

• HTV silicone

• RTV silicone

• Advantages of HTV over RTV

b) Silicone elastomer

The silicon elastomers -- introduced -1946,

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 silicon is combined with methyl chloride to form Dimethyl dichloro siloxane, which, when it reacts with water, forms a polymer

BEUMER

Polymers – translucent , watery , white fluids .

Fillers -- additional strength.

Anti-oxidants & vulcanizing agents -- transform the raw mass from a plastic to a rubbery resin during processing

Cross linking makes the silicones especially resistant to degradation from ultra-violet exposure.

BEUMER

Disadvantages of silicones

Poor strength

Receive colors poorly or with difficulty

Some are opaque resulting in prosthesis that are cold and lifeless.

Microbial growth

Poor wet ability

Good only with silicone adhesives

Classification of silicone

• Based on the Mechanism

• Acc. to Application

• Based on chemistry

JIADS VOL 1 ISSUE 2 APRIL- JUNE 2005;

Based on the Mechanism

• Room temperature (RTV)

• High temperature (HTV)

Acc.toApplication

• Implant grade - FDA requirement

• Medical grade - external use

• Clean grade - packaging

• Industrial grade -industrial applications

Based on chemistry

• Polydimethyl siloxanes

• Methyl vinyl /dimethyl siloxanes

• Phenyl methylsiloxanes

• Fluoro dimethyl siloxanes

Industrial use

JIADS VOL 1 ISSUE 2 APRIL- JUNE 2005;

HTV Silicone

1. 1 or 2 component system with putty like consistency

2. 2 primary catalysts - platinum salt (addition) and dichlorobenzoyl peroxide (condensation).

3. Filler - very pure, finely divided silica (size 30 )

4. Processing of heat cured silicones requires sophisticated instrumentation and high temperature.

BEUMER

• Excellent thermal stability

• Biologically inert

• Color stable when exposed to ultraviolet light

Advantages

• Opaque, lifeless appearance

• Not adequate elasticity in function

• Metal Molds

Disadvantages

HTV Silicone

HTV silicone

Silastic S-6508 Silastic 370, 372, 373 Silastic 4-4514 Silastic 4-4515 MDX 4-4159 SE- 4524U Q7- 4635 Q7- 4650 Q7- 4735

These silicones can be preformed into various shapes for alloplastic implantation or facial prostheses.

BEUMER. CHALLIAN;

RTV Silicone

Available as clear solutions

A viscous silicone polymer that includes a filler& a catalyst –

Stannous octoate is the most common catalyst .

Fillers usually diatomaceous earths - improve strength, but significant loss of translucency occurs. This problem primarily exists typically with Silastic 382 & 399.

2 types of RTV

Condensation type

Orthoalkyl silicate cross-linking agent

Stannous octate catalyst

Addition type

Hydro-methyl siloxane cross-linking agent

Chloroplatinic acid catalyst

ADVANTAGES:

- Color stable

- Biologically inert

- Easier to process

- Retain physical & chemical properties at wide rangeof temperature

- Stone molds can be used

DISADVANTAGES:

- Poor edge strength

- Costly

- Cosmetic appearance of the material -- inferior tothat of polyurethanes, acrylic resins, polyvinylchloride.

ADVANTAGES OF HTV OVER RTV1. Less chances of air bubble entrapment,

since hand mixing of catalyst & pigmentswith the elastomer is avoided.

2. Increased tear strength mechanicaldurability, & chemical resistance.

3. Increased biocompatibility andflexibility

FOAMING SILICONES

The purpose -- reduce the weight of the prosthesis.

After the silicone is processed, the gas is eventually released leaving a spongy material.

ADV--The formation of the bubbles within the mass can cause the volume to increase by as much as 7 times.

However, the foamed material has reduced strength and is susceptible to tearing. This weakness can be partially overcome by coating the foam with another silicone

BEUMER

Silastic 386:

Recent Advances

MPDS- Silicone block copolymer

Polyphosphazenes

Silphenylenes

MDX4-4210

MDX 4 - 4210

Low temperature, vulcanizing silicone polymer

Provided as a two component kit

The polymerization reaction is addition reaction with no by product

Very colour stable

JIADS VOL 1 ISSUE 2 APRIL- JUNE 2005;

Advantages of this material

Most importantly it has a high tear strength compared to RTV silicones

Unusually thin edges can be designed in a prosthesis without the risk of damage during wear & removal.

Accelerated aging tests have shown that the elastomer is very color stable.

JIADS VOL 1 ISSUE 2 APRIL- JUNE 2005;

SilPhenylenes

Arylene silicone polymer - synthesized &

formulated as a pourable, viscous, RTV liquid

Transparent ,Reinforced with silica fillers.

Three component kit –

Base elastomer,

Tetrapropoxysilane (cross linking agent) and

Organotin catalyst

JIADS VOL 1 ISSUE 2 APRIL- JUNE 2005;

Improved property

Unusual combination of high-tensile strength &low modulous (relative to other conventional RTV silicones)

Improved edge strength

Superior coloration

Feel like skin

JIADS VOL 1 ISSUE 2 APRIL- JUNE 2005; BEUMER

MPDS -- Silicone Block Copolymers (Methacryloxy propyl-terminated poly dimethyl siloxane)

It is introduced to improve some of the drawbacks of silicone elastomers, such as decreased tear strength, low percent elongation & bacterial growth over prosthesis.

Methacrylate - (ADHEOPHILIC) reduces the hydrophobicity which enhances the adhesive bond strength to non-silicone-based adhesives

Polyphosphazenes

Fluoro elastomer has been developed for use as a resilient denture liner (NovusTM, Hygienic Corp.)

It has the potential to be used as a maxillofacial prosthetic material.

New organosilicone maxillofacial

prosthetic materialsLai, wang, Delong, Hodges.

The purpose of this study is to evaluate the physical properties

of new prosthetic materials based on methacryloxypropyl

terminatedpolydimethylsiloxane (MPDS-MF) and to compare

the properties with those of A-2186.

The hardness of MPDS-MF is similar to A-2186. However,

tensile strength, tear strength, ultimate elongation, and

adhesive bonding strength of MPDS-MF are higher than those

of A-2186

Dental Materials 18 (2002) 281 ±286

Effect of nano-oxide concentration on the mechanical

properties of a maxillofacial silicone elastomer,

The purpose of this study was to evaluate the effect of different

concentrations of nanosized oxides of various composition on the

mechanical properties of a commercially available silicone

elastomer.

Nanosized oxides (Ti, Zn, or Ce) were added in various

concentrations to a commercial silicone elastomer (A-2186),

Incorporation of Ti, Zn, or Ce nano-oxides at concentrations of 2.0% and 2.5% improved the overall mechanical properties of the silicone A-2186 maxillofacial elastomer.

(J Prosthet Dent 2008;100:465-473)

Coloration

Defined as one that has a distribution of pigments equivalent to that of human skin and whose overall colour appears to change precisely as does that of a human skin under all types of illumination. – Chalian

Coloration of the prosthesis varies with the materials used and the preference of the clinician.

Basic skin tones should be developed into a shade guide for the materials that are used.

The base shade selected should be slightly lighter than the lightest skin tones of the patient because the prosthesis will darken by either extrinsic or intrinsic coloration.

TAYLOR

Coloration techniques can be divided into 3 groups: Extrinsic, intrinsic or combination technique.

The combination technique is widely used because it produces prosthesis with a more natural appearance.

The color match of the prosthesis depends largely on the skill of the clinician, color activity of the individual and light source.

At present the procedure is done using an empirical trial and error method having no standardization for future reference.

TAYLOR

Intrinsic coloration:

Intrinsic coloration is the color applied within the mold during the casting procedure.

A three dimensional quality is accomplished by incorporating subsurface details such as blood vessels, freckles and moles.

TAYLOR

Knowledge of primary, secondary and complementary colors is helpful in selection of chroma.

Primary Color Secondary ColorComplementary

Color

1) Red Red+Yellow=orange Red-Green

2) Yellow Yellow+blue=Green Yellow-Violet

3) Blue Blue+Red=Violet Blue-Orange.

TAYLOR

Spectrophotometers used to measure patient skin color

Kaolin Powder Calcined White

G-102 used to create opacity with

silicone products

Basic Skin Pigments for intrinsic stain

Dry Pigments

Flocking / Fibres for intrinsic stains Veins

Accelerated color change in a maxillofacial

elastomer with and without pigmentation

This study attempted to determine whether predictable color changes occur when 3 pigments are individually incorporated into a specific silicone elastomer.

The materials included an RTV elastomer; 1 natural inorganic pigment, burnt sienna and 2 synthetic organic pigments, Hansayellow and alizarin red.

Acceleration was achieved…

If left indoors with exposure to normal levels of daylight, the observed color change of the specimens would likely occur but take more time.

(J Prosthet Dent 2001;85:614-20.)

Once the base color is identified, laminar glazes are

applied to simulate the skin complex appearance.

Laminar glazes are layers of color painted into the

mould before packing the base color and this is

combined with placement of threads and flocks for

blood vessel simulation.

Common colors for laminar glazes are:

Red bluish glaze .

Golden tan glaze

Dark brown glaze

Opaque Yellow White color

Dark blue or purple

Opaque, Pink to red helix color

TAYLOR

Base color is compared to patient

skin with red bluish glaze , layered

over a base color

Red bluish glaze is painted into the first layer of

mould

Tweezers and periodontal

probe to place thread for blood

vessel simulation

Syringe used to inject

silicone into the helical group

Instrinsically painted

mould prior to packing the

base color

Extrinsic Coloration:

It is more predictable

It should be used sparingly

Apply the extrinsic pigments in small amounts and on the surface of the prosthesis in a stippled fashion. Curing can be done by placing in an air-circulating oven at 90°centigrade.

Additional glazes are applied and cured by using air drier.

TAYLOR

Application of extrinsic color Blending the Seam

Application of kaolin to Compressed air used to

Cured surface of the prosthesis eliminate excess kaolin

TAYLOR

In vitro evaluation of color change in maxillofacial elastomer

through the use of an ultraviolet light absorber and a

hindered amine light stabilizer.

This study evaluated color stability when an ultraviolet light

absorber and hindered amine light stabilizer were mixed in the

maxillofacial elastomer containing either organic or inorganic

pigments.

The materials used were an RTV silicone elastomer, 1 natural

inorganic dry-earth pigment (burnt sienna) and 2 synthesized

organic pigments (hansa yellow and alizarin red), ultraviolet light

absorber (UVA) and hindered amine light stabilizer (HALS).

UVA and HALS were shown to be effective in retarding color

changes.

J Prosthet Dent. 2004 May;91(5):483-90

Adhesives

Introduction

Classification

Problem with adhesives

Introduction Adhesives are expected to retain prostheses

during ordinary & extreme facial expressions, build-up of sebaceous secretions & water & change of weather conditions.

Most facial prostheses are retained with a medical grade adhesive.

Selection depends -- Biocompatibility,-- Retentive properties-- Ease of applicability-- Removal on daily basis-- Nature of the material

from which prosthesis is fabricated.

BEUMER

Classification of Adhesive Rubber-based liquid adhesives (natural & latex)

Silicone

Cyanoacrylates

Pressure-sensitive tape(double-coated polyethylene, 3M surgical tape)

These materials are backing strips composed of cloth, paper, film, foil, or laminate coated with a pressure-sensitive adhesive.

The bond weaker than that of rubber adhesives.

Advantages - the ease of application & cleaning

after removal.

Indication for biphasic tape is with materials that have poor flexibility & nonmobile tissue beds.

Silicone adhesives(Holister)

Are a form of RTV silicone dissolved in solvent.

Once applied, the solvent evaporates & a tacky surface forms that form bond with another surface

Despite their low adhesive strength, they have good resistance to moisture & weathering with low water sorption

Acrylic resin emulsions(Epithane-3, ProsAide)

Composed of acrylic resin dispersed in water solvent when evaporated, leaves a rubber-like substance.

Other materials -- synthetic rubber, vinyl acetate, reclaimed rubber, vinyl chloride, styrene, & methacrylic

Penetration & wetting -- controlled by addition of surfactants or altering the particle size of the dispersion.

Increasing the viscosity -- prevent penetration into porous surfaces.

Problems with Adhesives

Patients with poor manual dexterity or coordination may not be able to apply the adhesive or position the prosthesis in a consistent manner.

Margins adjacent to mobile tissue require constant reattachment with facial movements.

Allergic or irritational responses may persist.

Some aromatic base adhesives may curl thin prosthesis margins.

Poor hygiene limit the wearing of a prosthesis , because of interference with adhesive qualities.

Routine removal of adhesive -- remove the external pigmentation

Limitations of the Maxillofacial Materials…

No single maxillofacial material is ideal for every patient

1. Continued effect of sunlight and vascular dilatation & contraction on the natural tissues cannot be duplicated in the prosthesis.

2. Variations of skin tone when the patient is exposed to different light sources (e.g., incandescent, fluorescent, & natural light) cannot be duplicated in the prosthesis

3. The prosthesis cannot duplicate the full facial movement of the non defective side

4. Varying physiologic conditions of the patient in everyday living (e.g., lack of sleep, infectious diseases, and edema resulting from interrupted lymph drainage caused by surgery) cannot be duplicated in the prosthesis.

5. Inflammation caused by recent surgery, which subsides with time -- necessitates remaking the prosthesis.

6. Lack of predictability of the life of the prosthesis, because of variations among patients (i.e., secretions, smoking, and environment

Conclusion…

References

1. “Maxillofacial Prosthetics”, Chalian

2. “Maxillofacial prosthetics” Laney WR

3. “Clinical maxillofacial Prosthetics” Thomas D Taylor

4. Oral and maxillofacial rehabilitation by Buemer.

5. Robert Sanchez, comparision of physical properties of two

types of polydimethyl siloxane, MDX4-4210 and new

material A-2186 JPD 1992:67(5);679

6. Effect of nano-oxide concentration on the mechanical properties

of a maxillofacial silicone elastomer, Ying Han, DDS, MS,a

Sudarat Kiat-amnuay, DDS, MS,b John M.Powers, PhD,c and

Yimin Zhao, DDS, PhDd, J Prosthet Dent 2008;100:465-473

7. New organosilicone maxillofacial prosthetic materials

Lai, wang, Delong, Hodges, Dental Materials 18 (2002) 281 ±286

8. Accelerated color change in a maxillofacial elastomer with and

without pigmentation, John J. Gary, Eugene F. Huget and Larry D.

Powell, J Prosthet Dent 2001;85:614-20.

9. In vitro evaluation of color change in maxillofacial elastomer

through the use of an ultraviolet light absorber and a hindered

amine light stabilizer, J Prosthet Dent,2004 May;91(5):483-90

10. An in vivo evaluation of adhesives used in

extraoral maxillofacial prostheses.

Haug SP, Richard GE, Margiotti E, Winkler MM, Moore

DJ, J Prosthodont 1995 Mar;4(1):11-5.

11. . Mechanical behavior of three maxillofacial prosthetic

adhesive systems: A pilot project, John F. Wolfaardt, Victor

Tam, M.Gary Faulkner, Narasimha Prasad, The journal of

prosthetic Dentistry,vol 68;6:December 1992, Pages 943–

949

12. . JPD 1984:51(4):523-226.