Maxillofacial materials

MAXILLOFACIAL
MATERIALS
DR. AATIF KHAN
1

CONTENTS -
1. INTRODUCTION
2. HISTORY
3. CHARACTERISTICS
4. CLASSIFICATION
5. MATERIALS
6. COLORATION
7. RETENTION
8. LIMITATIONS
9. RECENT ADVANCES
10. REFERENCES
2

DEFINITION -
Maxillofacial prosthetics –
The branch of prosthodontics concerned with the restoration and/or replacement of
stomatognathic and craniofacial structures with prostheses that may or may not be removed on
a regular or elective basis. (GPT – 9)
Maxillofacial prosthetics –
The art and science of anatomic functional or cosmetic reconstruction by means of non-living
substitutes of those regions in the maxilla, mandible and face that are missing or defective
because of surgical intervention, trauma, pathology or developmental or congenital
malformations. (Chalian)
Maxillofacial prosthesis –
Any prosthesis used to replace part or all of any stomatognathic and/or craniofacial structures.
(GPT – 9)
3

ADVANCEMENTS IN SOFT-TISSUE PROSTHETICS PART A: THE ART OF IMITATING LIFE - RENA L. J. CRUZ 5

PHYSICAL AND MECHANICAL PROPERTIES
High edge and tear
strength -
Range - 30 to 100 psi
(to resist rupture)
UTS and % elongation –
High values are most
desirable
(Flexibility)
Dynamic modulus –
should be low
(Less rigidity)
Hardness – same as that of
facial structure
(25-35 Shore A scale)
Stiffness -
Low glass transition
temperature
(prevent stiffening at cold
temperatures)
Wettability –
High surface
energy/contact angle
Water sorption -
Low
Shouldn’t absorb water
Weight –
Lightweight
Comfortable
7

CHARACTERISITCS
1. PROCESSING
2. PERFORMANCE
3. BIOLOGICAL
8

A. PROCESSING CHARACTERISTICS -
• Material should be a castable solvent-free liquid (to avoid bubbles) having a low viscosity.
• Chemical and color stability after processing.
• Ease of application and retaining of intrinsic and extrinsic coloring during use.
• Reusable molds.
• Working time should be long enough to allow the clinician to degas the mixture and fill the
mold carefully (15 mins to 1 hour).
9JPD 1984:51;521-523

B. PERFORMANCE CHARACTERISTICS -
• The prosthesis must be strong and tough yet soft and pliable enough to respond to the facial
movements.
• No distortion should occur when the prosthesis is boiled in water or sterilized in steam, even if
either treatment is a recommended procedure.
• The finished prosthesis should not contain leachable plasticizers or additives and should retain
its size and shape.
10JPD 1984:51;521-523

B. PERFORMANCE CHARACTERISTICS -
• Readily available at a reasonable cost, have an adequate shelf life, and be easily stored.
• Easily repaired, lightweight and should lend itself to the fabrication of hollow or foamed
prostheses.
• Compatibility with strong adhesives.
11JPD 1984:51;521-523

C. BIOLOGICAL CHARACTERISTICS -
1. Non allergenic and non-carcinogenic.
2. Inert to solvents and skin adhesive.
3. Hygienic, cleansable with disinfectants.
4. Easily adhere to living tissue.
5. Resist growth of microorganisms.
12JPD 1984:51;521-523

CLASSIFICATION
A. MAXILLOFACIAL MATERIALS –
1. RIGID MATERIALS –
• ACRYLIC RESIN
• BASE METAL ALLOYS (INTRAORAL)
• IMPLANTS
13

CLASSIFICATION
2. FLEXIBLE MATERIALS –
• ACRYLIC RESIN COPOLYMERS (PALAMED, POLYDERM)
• VINYL POLYMER AND COPOLYMERS (MEDIPLAST, REALISTIC)
• POLYURETHANE ELASTOMERS (EPITHANE – 33)
• SILICONE ELASTOMERS (HTV, RTV, FOAMING, SIPHENYLENES ETC)
14

CLASSIFICATION
B. AUXILLARY MATERIALS –
1. REVERSIBLE HYDROCOLLOID
2. IRREVERSIBLE HYDROCOLLOID
3. PLASTER OF PARIS
4. TISSUE CONDITIONERS
5. MODELLING CLAY / SCULPTER’S CLAY
6. PLASTOLENE
7. WAXES
15

MAXILLOFACIAL
MATERIALS -
1. ACRYLIC RESINS AND ACRYLIC RESIN COPOLYMERS
2. VINYL POLYMERS AND COPOLYMERS
3. POLYURETHANE ELASTOMERS
4. SILICONE ELASTOMERS
16

1. ACRYLIC RESIN
PROPERTY ADVANTAGES DISADVANTAGES
Powder : Polymethyl
Methacrylate
Durable Rigid
(Less acceptable to the patient)
Monomer Liquid: Methyl
methacrylate
Color stable (cosmetic) Can not be duplicated
Used in areas where less
movement occurs
Reline/repair possible Not suitable for movable tissue
beds
Chemical or self polymerized Compatibility with adhesives Water sorption
Ease of fabrication High thermal conductivity
(patient discomfort)
ACRYLIC RESIN 18

2. ACRYLIC RESIN COPOLYMERS -
(PALAMED)
PROPERTIES ADVANTAGES DISADVANTAGES
Powder - Plasticized Methyl
methacrylate polymer (elastic
properties)
Softness Poor durability,
Photodegradation
Monomer Liquid – Methyl
methacrylate
Good edge strength
Short avg life – 7 months,
yellowing necessitates
replacement.
Softness can be decreased by
mixing the monomer with
paladion liquid in ratio 60% : 40%
Elasticity Intrinsic staining difficult
Requires special cleansing agent -
Benzene
Finished restoration is sticky,
collects dust and stains
20ACRYLIC COPOLYMERS

• A new generation of acrylic monomers and oligomers which are thermal, chemical and photo
initiated are being researched. (Antonucci and Stansburry).
• These promise to eliminate the shortcomings of traditional acrylic copolymers.
21ACRYLIC COPOLYMERS

VINYL POLYMERS
AND COPOLYMERS
22

3. VINYL POLYMERS AND COPOLYMERS
CHARACTERISTICS ADVANTAGES DISADVANTAGES
Popular and widely used in the
past
Eg – Mediplast, Realistic
Flexible Edges tear easily,
Photodegradation
It consists of a combination
of polyvinyl chloride and a
plasticizer - vinyl acetate
Allows intrinsic and extrinsic
coloring
Stained easily,
Absorbs sebaceous secretions
Clear,
tasteless and odorless Acceptable esthetics
Metal molds for curing at high
temperature
Cross linking agents are added for
strength and UV stabilizers for
color stability
Plasticizers are added to produce
an elastomeric effect at room
temperature
Plasticizer migration and loss
resulting in discoloration
23VINYL COPOLYMERS

POLYURETHANE
ELASTOMERS
A. POLYURETHANE
B. ISOPHORONE POLYURETHANE
24

4. POLYURETHANE ELASTOMERS
• Formed by addition of a polymer terminating with an di-isocyanate, combined with one
terminating with a hydroxyl group, in presence of a catalyst - Organotin.
25MAXILLOFACIAL PROSTHETIC MATERIALS- AN INCLINATION TOWARDS SILICONES – A. MITRA

4.A POLYURETHANE ELASTOMERS
CHARACTERISTICS ADVANTAGES DISADVANTAGES
Serve a variety of commercial uses They can be
made elastic without
compromising strength
Difficult to process,
Poor color stability
Epithane - 3 and Calthane are for
facial restorations
Allows intrinsic and extrinsic
coloring
Moisture sensitivity,
Water contamination difficult to
control
Processing is carried out at 100°C
in stone molds.
Superior cosmetic results Poor compatibility with adhesives,
Toxicity – limits their use to
extraoral prostheses

4.B ISOPHORONE POLYURETHANE
• It comprises of isophorone diisocyanate, a butane diol and a polyether polyol which undergo a
controlled combination to produce a prepolymer.
• The prepolymer is then combined with a triol as a cross-linking agent and an organotin catalyst
and processed as polyurethanes.
• The material produced is stronger than the conventional polyurethanes.
27
Isophorone diisocyanate
MAXILLOFACIAL PROSTHETIC MATERIALS- AN INCLINATION TOWARDS SILICONES – A. MITRA
Polyol

5. SILICONES -
• Also known as Polydimethylsiloxanes, are a combination of organic and inorganic compounds
introduced in 1946.
• Most successful maxillofacial material till current times.
• Most frequently researched material and newer advances are being made to overcome the
weaknesses of the material.
29SILICONES

CHEMICAL STRUCTURE
• The silicone bonds (Si-O-Si) in the main chains, and the Si – C bonds in the side groups makes it
extremely flexible.
• Low viscosity and surface tension, low melting point and low glass transition temperatures.
• To increase strength, various fillers such as fumed silica, precipitated silica, aerogels are added.
• Anti-oxidants and vulcanizing agents - added to change the raw mass into rubbery resin during
processing.
• Silicones must be cross linked to form solid elastomer materials (Vulcanizing).
SILICONES 31

CLASSIFICATION OF SILICONES
There are four grades of silicone –
1. Class 1 – Implant grade
2. Class 2 – Medical grade
3. Class 3 – Clean grade
4. Class 4 – Industrial grade
Depending on whether the vulcanizing process uses heat or not, silicones are classified as:
• HTV Silicone
• RTV Silicone
SILICONES 32

4.A - HTV SILICONES
• A white opaque material with a highly viscous putty
like consistency.
• Available as 1 component or 2 component system.
• Examples – Silastic 370, 372, 373 etc
33HTV SILICONE

HTV SILICONES
Three main vulcanizing medical grades of HTV silicones are available –
1. MDX 4 – 4514 : Soft rubber - used for ear prosthesis if undercut areas are used for retention.
2. MDX 4 – 4515 : Medium rubber - provides the most satisfactory standard of resilience for
the average prosthesis.
3. MDX 4 – 4516 : Hard rubber - used where more rigid support is required (base of ear, bridge
of nose, to support fixation of spectacles)
HTV SILICONE 34

HTV SILICONES
COMPOSITION ADVANTAGES DISADVANTAGES
Poly-dimethyl siloxane copolymer. Excellent tear strength Elasticity not adequate
Vulcanizing agent –
Di-chlorobenzoyl peroxide
Excellent chemical and color
stability
Low edge strength
Filler –
Very fine silica (30)
Excellent thermal stability Technique sensitive
Catalyst –
Platinum salt
High percentage elongation Processing requires sophisticated
instrumentation and high
temperature
Opaque,
life-less appearance Excellent esthetics after pigment
incorporation
Difficult to pigment and process,
Metal molds required

4.B RTV SILICONES
• Viscous Polydimethyl siloxane copolymers that includes a filler and a catalyst.
• Supplied as single-component materials that cure by evaporation of acetic acid.
• Characterized by a natural flesh-like appearance by using dyed rayon fibers, dry earth
pigments, and/or oil paints.

4.B RTV SILICONES
• Prostheses are polymerized by bulk packing.
• Recently epoxy resins and stainless steel molds are being used.
• Requires increased curing time at room temperature.

CLASSIFICATION OF RTV SILICONES
RTV SILICONES
1. Condensation
type
Cross linking agent
– Tetraethyl silicate
Catalyst –
Stannous octoate
2. Addition type
Cross linking agent
– Hydroxymethyl
siloxane
Catalyst –
Chloroplatinic acid

RTV SILICONES
1. CROSS LINKING BY CONDENSATION REACTION
• They have reactive groups such as silariols (hydroxyl- terminated polysiloxanes).
• This method of cross-linking requires a cross linking agent, eg. tetraethyl silicate, and a catalyst,
e.g. dibutyltin dilaurate or stannous octoate.
• Crosslinking requires water molecules to hydrolyze the silane and produces acetic acid (an irritant)
as the by-product. The use has therefore been limited to that of an extrinsic colorant carrier applied
to the surface of the prosthesis.
• Eg – Medical adhesive type A.

RTV SILICONES
Advantages –
• Fine details obtainable.
• Inherent strength.
• Easy to obtain.
Disadvantages –
• Produces by-products.
• Curing time is excessively long.
• Relatively low tear strength and are incapable of maintaining edge resistance.

RTV SILICONES
2. CROSS LINKING BY ADDITION REACTION
• Involves addition of silyl hydride (--SiH) groups to vinyl groups (CH2 = CH--) attached to the silicone
with the help of a platinum containing catalyst.
• Curing requires heating the material at 150 C for an hour.
• Have improved tear strength over condensation RTV silicones.
• Examples – Silastic 382, 399, 891, MDX4-4210, Cosmesil, A-2186, and A-2186F.

RTV SILICONES
ADVANTAGES –
• Use of stone molds.
• Ease of manipulation and coloring.
• Color stability and biological inertness.
DISADVANTAGES –
• Very hydrophobic.
• Selective adhesive property.
• No extrinsic coloration possible.
• Curing may be inhibited by traces of amines, sulfur, nitrogen oxides and organo-tin compounds.

PROPERTIES OF HTV AND RTV

ADVANTAGES OF HTV OVER RTV
1. Increased tear strength.
2. Increased mechanical durability and chemical stability.
3. Increased biocompatibility and flexibility.

DEGRADATION OF
SILICONES
1. TIME AND WEATHERING
2. SKIN SECRETIONS
3. MICROBIAL GROWTH
4 DISINFECTION
46

DEGRADATION OF SILICONES
• Over time, all prostheses will undergo mechanical and chemical changes that limit their service
life.
• Despite excellent durability, silicone eventually begins to look and feel unrealistic through color
degradation, staining, weathering, changes to elasticity, and premature tearing.
• In addition, contact with skin secretions further degrades them and also encourages microbial
growth --> potential irritation and infection for the patient and microbial induced polymer
degradation.
47

A. TIME AND WEATHERING
• Degradation of silicone’s color and mechanical properties occurs by UV radiation, pollution,
variations in temperature, and humidity.
• Degradation mechanism has 3 steps -
1. Initiation - Formation of free radicals.
2. Propagation - Silyl radicals react with O2 to produce polymer-oxy radicals and secondary
polymer radicals, resulting in chain scissions.
3. Termination - Radicals react with each other, often creating crosslinks between the chains.
• All 3 steps occur simultaneously; with chain scission and crosslinking continuously occurring.
GOIATO ET AL., 2012B, ELENIET AL., 2009, STATHI ET AL., 2010, RABEK,2012 48

A. TIME AND WEATHERING
1. Incorporation of additives (opacifiers) –
• Barium sulfate (0.2wt%) prevented color change in unpigmented and pigmented silicones.
• It strongly associates within the silicone matrix, staying within the silicone and not greatly
effecting the material hardness.
2. Addition of titanium dioxide nanoparticles can inhibit color change in silicones with organic
pigments and increase tensile strength.
GOIATO, WANG ET AL, HAN ET AL 2010 49

B. SKIN SECRETIONS
• Acidic and alkaline perspiration is generally absorbed which weakens silicone while increasing
its elasticity and hardness.
• Sebum interacts with the silicone surface with highly variable results depending on the type of
silicone.
• Water absorption - leads to an increase in weight of the prosthesis.
(POLYZOISET AL., 2000; ELENI
ET AL., 2011A) 50

C. MICROBIAL GROWTH
• Adversely affects the mechanical properties and appearance of the prosthesis .
• Hydrophobic nature, porosity and surface roughness of silicone - colonized by a variety of
commensal microorganisms which form biofilms and resist removal.
• Increase in filler content may hinder the colonization of C. albicans.
(HULTERSTRÖMET AL., 2008;
PREOTEASA ET AL., 2011; ARIANIET AL., 2012). 51

52
• Microorganisms penetrate into the silicone matrix and create bag-like defects and reduce the
service life of the prosthesis, irritation and possibly infection.

D. DISINFECTION OF SILICONES
• Cleaning products and disinfectants themselves can also degrade the silicone.
• Several studies performed using the disinfectants chlorhexidine, effervescent tablets, and
neutral soap, did not see any significant change in dimensional/mechanical properties of silicone
without additives.
• However, specimens with additives (ceramic pigments, make-up, or titanium dioxide opacifiers)
showed changes in mechanical properties even with reduced disinfection regime.
53

D. DISINFECTION OF SILICONES
• Eleni et al. investigated microwave disinfection by immersing silicone samples in water and
microwaving for 3 min, 365 times, to simulate daily disinfection for 1 year : hardness appears to
decrease by a small amounts.
• Longer duration microwave disinfection at 8 min damaged the surface of silicone and reduced tensile
strength. Kotha et al. (2016)
• Less frequent disinfecting appears to reduce the negative effects of disinfectants.
54

RECENT ADVANCES IN
THE MATERIALS
MDX4 4210, FOAMING SILICONES, MPDS-SILICONE BLOCK
COPOLYMERS, SIPHENYLENES, CHLORINATED POLYETHYLENE,
POLYPHOSPHAZENES
55

1. MDX4 - 4210
• Introduced in the 1970s.
• An RTV silicone copolymer.
• It is a clear to translucent two-part silicone system.
• Polymerization reaction - addition reaction, no by products.
• Very color stable.
56JIADS VOL 1 ISSUE 2 APRIL- JUNE 2005MAXILLOFACIAL PROSTHETIC MATERIALS- AN INCLINATION TOWARDS SILICONES – A. MITRA

1. MDX4 - 4210
ADVANCEMENTS -
• Most importantly it has a high tear strength compared to conventional RTV silicones.
• High edge strength - 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.
• Characterization - achieved with pigments immersed in a silicone adhesive.
• Very biocompatible - also used as a drug matrix for drug delivery system
57JIADS VOL 1 ISSUE 2 APRIL- JUNE 2005MAXILLOFACIAL PROSTHETIC MATERIALS- AN INCLINATION TOWARDS SILICONES – A. MITRA

2. A - 2186
• Introduced in 1986 by Factor II (Lakeside, AZ)
• A- 2186 was the first commercial platinum-catalyzed silicone elastomer.
• It is a clear-to-translucent two-part (10:1 base:catalyst) pourable RTV silicone.
• A fast polymerization rate version of A-2186 with higher platinum content, “A-2186F,” became
commercially available in 1987, though it was not a very preferred material for prosthesis
purpose.

• Due to their hydrophobic nature, silicones have low adhesion to non - silicone adhesive materials.
• According to a survey conducted by PC Montgomery et al., to review the extraoral maxillofacial
materials -
• MDX4-4210 and A-2186 RTV silicones along with Silastic Medical Adhesive Type A (for extrinsic
coloring of prostheses) were the most preferred maxillofacial prosthetic materials used.

• Half-life of silicone maxillofacial prosthesis - approximately 6 months.
• Degradation of physical and color properties of silicones are the most common reasons for re-
fabrication.
• Surface-treated silica fillers with an increased surface area and a small particle size - enhance the
physical and mechanical properties of silicone elastomers.
• Lately, researchers have found even stronger enhancement in properties through the use of nano
silica powder, which has an even larger surface area than micrometer-size silica powder.

FOAMING
SILICONES
SILASTIC 386
62

FOAMING SILICONES (SILASTIC 386)
• Foaming silicones have Silastic 386, a type of RTV silicone.
• Additive type, which release gas when the catalyst, stannous octoate is introduced.
• After the silicone is processed, the gas is eventually released leaving a spongy material.
• The purpose of the foam is to reduce the weight of the prosthesis.
63BEUMER, MAXILLOFACIAL PROSTHETIC MATERIALS- AN INCLINATION TOWARDS SILICONES – A. MITRA

FOAMING SILICONE (SILASTIC 386)
ADVANTAGES –
• The formation of the bubbles within the mass can cause the volume to increase by as much as
7 times.
DISADVANTAGES –
• Reduced strength.
• Susceptible to staining.
• Weakened material.
64BEUMER, MAXILLOFACIAL PROSTHETIC MATERIALS- AN INCLINATION TOWARDS SILICONES – A. MITRA

Silicone Block Copolymers
• In this, blocks of polymers other than siloxane i.e Methacrylate, are positioned with the traditional
siloxane polymers.
• The hydrophobic and foreign nature of silicones cause problems with the body on a molecular level.
• This can lead to the induction of foreign body reactions and the development of infections
particularly at the interface between silicone and tissue.

Silicone Block Copolymers
• These silicone block copolymers can overcome these problems as the more hydrophilic part
of these amphiphilic polymers provides improved wettability and thus tissue compatibility.
• Example - Intertwining of Methacrylate (PMMA) into the chains of siloxane.
• Methacrylate - reduces the hydrophobicity which enhances the adhesive bond strength to
non-silicone-based adhesives.

SIPHENYLENES
• These are siloxane copolymers that contain methyl and phenyl groups.
• Synthesized and formulated as a pourable, viscous, RTV liquids.
• Transparent, reinforced with silica fillers.
Three component kit –
1. Elastomer base.
2. Cross linking agent – Tetrapropoxysilane.
3. Catalyst – Organotin.

SIPHENYLENES
• IMPROVED PROPERTIES –
• Unusual combination of high-tensile strength & low modulus of elasticity (relative to
other conventional RTV silicones).
• Improved edge strength and color stability.
• Biocompatibility.
• Feel like skin.

CHLORINATED POLYETHYLENE
• Industrial grade thermoplastic elastomer. (DOW Chemicals)
• Macromolecular elastomer, primarily used as impact modifier to improve the strength of
resins.
• Non-carcinogenic, less toxic and less irritating than silicones.
• Suitable substitute for silicones for the fabrication of maxillofacial prostheses in situations
where cost of silicones is high.
• Processing involves high heat curing of pigmented sheets in metal molds.

POLYPHOSPHAZENES
• Polyphosphazene elastomers have been developed for use as resilient denture liners.
• Researchers have found that compounding Polyphosphazenes with little or no fillers and
decreasing the ratio of acrylic to rubber yields a softer rubber, similar to human skin.
• The rubber is compounded with pigments for appropriate matching with the patients skin.

POLYPHOSPHAZENES
• ADVANTAGE –
• Freedom of movements of the dentures toward the tissue, similar to the periodontal
membrane around natural tooth.
• DISADVANTAGE – Expensive.
• Future scope – These might become the material of choice for many biomedical uses.

COLORATION
 Defined as one that has a distribution of pigments equivalent to that of human skin and whose
overall color appears to change precisely as does that of a human skin under all types of
illumination. – Chalian
 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.
77CHALIAN, Intrinsic and Extrinsic Stains & Colour Bleeding in Maxillofacial Prosthesis – P. Srivastava

COLORATION
• There are intrinsic and extrinsic methods of coloring.
• Dry earth pigments, rayon flocking fibers (most commonly used), artist’s oil pigments, or a
combination of these materials for intrinsic coloring.
• Kaolin was commonly used as an opacifier.
• The most-used extrinsic coloring method was Medical Adhesive Type-A mixed with xylene as a
retarder/thinner tinted with dry earth pigments or artist’s oil pigments applied to the surface
of the prosthesis in a thin layer.

INTRINSIC COLORATION
79
• Added and mixed into the silicone before curing or applied in the mold during casting.
• Depth of color and translucency can be more accurately achieved.
• A three dimensional quality is accomplished by incorporating subsurface details such as blood
vessels, freckles and moles.
• These are cured with the silicone and hence cant be rubbed off easily, increasing the service
life of the prosthesis.
Intrinsic and Extrinsic Stains & Colour Bleeding in Maxillofacial Prosthesis – P. Srivastava

INTRINSIC COLORATION
• Basic shade must be achieved by intrinsic coloration as extrinsic coloring can change the look
of the prosthesis only to some extent.
• Flocks and veins can also be added to enhance the look of the prosthesis.
• Flocks are nylon fibers, provide a life – like appearance and texture, available in various shades
are added in minimal quantities.
• Veining fibers can also be added to give the prosthesis a darker or bluish hue resembling veins
in particular areas.
80Intrinsic and Extrinsic Stains & Colour Bleeding in Maxillofacial Prosthesis – P. Srivastava

81
Oil paints for intrinsic staining Basic pigments for intrinsic staining
Rayon flocking fibers for
characterization
Basic Skin Pigments for intrinsic stain
Kaolin Powder Calcined White
G-102 used to create opacity with
silicone products
Veins

EXTRINSIC COLORATION
• They are externally added after curing the prosthesis.
• Though they are more predictable and can be evaluated directly with the patient skin, they’re
used sparingly due to vulnerability to environmental degradation and handling.
• Physically applied with a brush on the surface of prosthesis in presence of the patient, so that
final coloring can be made to match the patients skin tone as close as possible.

EXTRINSIC COLORATION
• A single component silicone sealant/primer is added to seal the pigment down into the silicone.
• Commercially available sealants are used to give final finishing and detail to the prosthesis.
• Manipulation of the color of the prosthesis is kept to minimal by these sealants
• They are mechanically bonded to silicone hence there is degradation of color with repeated
handling, cleaning and exposure to environmental factors.

MATERIALS FOR EXTRINSIC COLORATION
84
Silicone primer
Extrinsic
stains
Silicone primerExtrinsic stains
PIGMENTS AVAILABLE AS POWDERS, PIGMENTS SUSPENDED IN OILS, PASTES

PARTIAL LIST OF PIGMENTS USED IN MAXILLOFACIAL PROSTHETICS
PIGMENTS AND THEIR APPLICATION IN MAXILLOFACIAL ELASTOMERS: A LITERATURE REVIEW
JOHN J. GARY
85

COLOR BLEEDING / COLOR FADING
• Principle reason for replacement of facial prosthesis –
• Degradation in appearance due to change of color and physical properties.
• Chen et al evaluated the reaction of 138 patients to their facial prosthesis, and found that color
fading was the most frequent response given by patients for disliking their responses.

• Factors causing color instability –
• Accumulation of stains.
• Dehydration, water absorption.
• Surface roughness, chemical degradation from use.
• Oxidation during double carbon reactions producing peroxide compounds.
• Continuous formation of pigments due to degradation.

• Intrinsic factors involve discoloration within the material itself with alterations in the matrix.
• Extrinsic factors involve adsorption and absorption of substances that are chiefly responsible
for discoloration.
• Intrinsic pigments exhibit less loss of color (fewer chances of being dissolved during cleaning).

MATERIALS FOR RETENTION
IN MAXILLOFACIAL
PROSTHETICS -
89

90
MODES OF RETENTION
A. Intraoral
Anatomical Mechanical
1. Temporary
S.S wire to
remaining teeth
S.S wire to denture
2. Permanent
B. Extraoral
Anatomic
Mechanical
Adhesives
Combination
RETENTIVE AIDS USED IN MAXILLOFACIAL PROSTHESIS – YASHWANTE B
(IJCDS)

ADHESIVES
• Maxillofacial prosthetic adhesive - a material used to adhere external maxillofacial prostheses
to skin and associated structures around the periphery of an external anatomic defect. (GPT-9)
• They're classified as solvent or water based.
• Bond strength of solvent based adhesives are much stronger than water base, but they cause
curling of the thin margins of the prostheses.
(IJCDS)
91

ADHESIVES
• Water based adhesives are easier to clean.
• Solvent based require a solvent (ethyl acetate) to clean off the adhesive which may cause
tearing of thin edges.
• Adhesives are available in many forms such as -
• Liquids, medical adhesives, emulsions, sprays and double coated polyethylene sheets or tapes.
92
(IJCDS)

ADHESIVES
Commonly used adhesives are classified as –
1. Rubber based liquid adhesives (natural and latex),
2. Pressure sensitive bi-faced tape (3M),
3. Silicones,
4. Acrylic resin emulsions (gum mastics) and
5. Cyanoacrylate
93
(IJCDS)

ADHESIVES
• Adhesives are expected to retain a prosthesis during ordinary and extreme facial expressions,
build up of sebaceous secretions and water, change of weather conditions.
• They must be biocompatible (contact skin for lengthy periods).
• Immediately traumatized tissue must be treated with great care and the chemical composition
of the adhesive must be evaluated before administration.
94
(IJCDS)

ADHESIVES
ADVANTAGES
•Easily available.
•Provide sufficient retention for a limited
period of time.
•Used in patients with good dexterity and soft
tissue condition as careful application of the
adhesive is required.
DISADVANTAGES
•May cause skin rashes and irritation.
•Accumulation of dust particles at skin-
prosthesis interface.
•Thinned out margins may tear due to
improper handling while adjusting prosthesis.
•Curling of the edges due to aromatic adhesive
may avoid correct placement and compromise
esthetics.
•May causes complication on irradiated/
inflamed skin.
95
(IJCDS)

1. SILICONE ADHESIVE (HOLLISTER)
• These adhesives are a form of RTV silicone dissolved in solvent.
• Once applied/sprayed , the solvent evaporates and a tacky surface forms that
can contact bond with another surface.
• Good resistance to moisture and weathering with low water sorption.
• Low adhesive strength, prone to dissolving in organic solvents such as xylene.
97MATERIALS AND TECHNIQUES IN MAXILLOFACIAL PROSTHODONTIC REHABILITATION – HUBER H AND STUDER S
(DCNA)

2. (DOUBLE COATED POLYETHYLENE, 3M
SURGICAL TAPE, PRESSURE SENSITIVE TAPE)
• These materials are backing strips composed of cloth, paper, film, foil or laminate coated with a
pressure sensitive adhesive.
• In these, the adhesive is a rubbery type of elastomer combined with a liquid or solid resin
tackifier component, plasticizers, fillers and anti-oxidants.
(DCNA)

3M SURGICAL ADHESIVE TAPE
• Advantages – Ease of application and cleaning after removal.
• Disadvantages – Weaker bond than that of rubber adhesives.
• Primary indication – For materials that have poor flexibility
and non-mobile tissue beds.
(DCNA)
2. (DOUBLE COATED POLYETHYLENE, 3M
SURGICAL TAPE, PRESSURE SENSITIVE TAPE)

3. ACRYLIC RESIN EMULSIONS (EPITHANE - 3)
• Acrylic resins dispersed in water solvent, when evaporated, leaves a rubber like substance.
• Other materials in the mixture - synthetic rubber, vinyl acetate, reclaimed rubber, vinyl chloride,
styrene and methacrylic.
• Penetration and wetting can be controlled by adding surfactants and by altering particle size of the
dispersion.
• Increasing viscosity can prevent penetration into porous surfaces.
(DCNA)

4. LATEX BASED ADHESIVES
• Contain natural rubber, ZnO and solvents, can be easily removed by peeling of when dry.
• Method of application same as silicone.
• Eg – Davol, DUO.
Disadvantages –
• A strong smell until it sets.
• Adhesive builds up on the prosthesis unless removed before each new application.
(DCNA)

In a survey of 73 patients who wear facial prostheses, the ranking of preferences for various
adhesive brands were –
1. Double sided tape (41%)
2. Rubber based liquid (21%)
3. Acrylic resin emulsions (19%)
4. Silicone (4%)
5. No reply (5%)
(DCNA)

PROBLEMS WITH ADHESIVES -
• Patients with poor manual dexterity may not be able to apply/position the adhesive in a
consistent manner.
• Margins adjacent to the mobile tissue may require constant reattachment with facial
movements.
• Allergic or irritational responses may persist.
(DCNA)

PROBLEMS WITH ADHESIVES -
• Poor hygiene may limit the wearing of a prosthesis because of interference with adhesive
qualities.
• Some aromatic base adhesives may curl the thin prosthesis margins.
• Routine removal may also remove the external pigmentation.
(DCNA)

CHOICE OF ADHESIVE
• The choice of a skin adhesive involves the status of a tissue and the material of the prosthesis
that it contacts. Some adhesives bond more strongly with certain materials.
Udagama determined the best combinations to be -
• Polyvinylchloride with Epithane – 3 adhesive,
• Acrylics with Medico, and
• Polyurethane with Davol.
(DCNA)

CHOICE OF ADHESIVE
According to Krill,
• Silicone adhesive type B is most effective for silicones.
• Pressure sensitive tape is most effective for Polyvinylchloride.
• Butyl apha-cyanoacrylate is most affective adhesive for Polyurethane.
MATERIALS AND TECHNIQUES IN MAXILLOFACIAL PROSTHODONTIC REHABILITATION – HUBER H AND STUDER S
(DCNA)
106

CARE AND MAINTAINENCE
• Avoid direct sunlight exposure.
• Avoid application of water or cosmetics/makeup on prosthesis
• Avoid smoking to increase the life of the prosthesis.
• Use of isopropyl alcohol to clean prosthesis.
• Use hats and sunglasses to increase life of the prosthesis.
• Patient should be trained on how to insert and remove prosthesis.

CARE AND MAINTENANCE
• UV absorbers may be used to help increase color stability in facial prosthesis.
• UV protection internally to silicone prosthesis, external protection with a UV inhibitor spray
should be investigated.
• Research needs to be directed towards minimizing the degree of color changes and effect of
human environment (sebum, alkaline perspiration etc) on color stability of maxillofacial
prosthesis.
108

LIMITATIONS -
109
• No single maxillofacial material is ideal for every patient.
• Continued effect of sunlight and vascular dilatation & contraction on the natural tissues
cannot be duplicated in the prosthesis.
• 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.
• The prosthesis cannot duplicate the full facial movement of the non defective side.

LIMITATIONS -
110
• 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.
• Inflammation caused by recent surgery, which subsides with time -- necessitates remaking
the prosthesis.
• Lack of predictability of the life of the prosthesis, because of variations among patients (i.e.,
secretions, smoking, and environment.)

RECENT ADVANCES IN
FABRICATION
TECHNOLOGIES
111

3D PRINTING PROCESSES IN MAXFAC PROSTHETICS
ADVANCEMENTS IN SOFT-TISSUE PROSTHETICS PART A: THE ART OF IMITATING LIFE – R. CRUZ 113

• 3D Surface Scanning - Use x-rays and nuclear magnetic effects to produce 3D images of tissue
structures within the body, hence obtaining 3D models of patient anatomy.
• Laser scanning - directs a laser onto the patient and the reflected light is used to determine 3D
geometry.
• 3D photography has been applied in producing 3D surface models of patient anatomy (Zardawi et al.,
2015b).
• The 3dMD systems (3dMD LLC, Atlanta, GA, United States) use images taken simultaneously from
cameras of known distances and angles to produce accurate 3D models.
114

• Photogrammetry - uses many photographs of the patient’s anatomy taken from different
locations to reconstruct a 3D point cloud of significant features which are then stitched together
to produce a 3D model.
• One advantage over other scanning techniques - ability to use accessible cameras such as
those found in smart-phones.
• Structured light scanning - A light pattern is projected onto the patient and the reflected
pattern is observed from several cameras.
115

Regardless of the scanning technique used, post-processing is required; such as –
• model alignment if there are multiple scans,
• elimination of abnormalities by deleting/editing mesh geometry,
• smoothing of bumps,
• scaling the scan to the correct dimensions,
• hole filling and remeshing.
116

CAD/CAM
• After scans are obtained and converted into a polygon mesh, the software is used to produce a
3D model of the required prosthesis.
• In some cases, scanned patient anatomy is mirrored and forms the basis for the prosthetic
computer model.
• In other cases, a library of anatomical models are available to be used. (Ciocca et al., 2010c; De
Crescenzio et al., 2011)
117

118
FLEXIBILITY OF IMPLANT PROSTHESIS
PROVISIONAL PROSTHESIS
Laser scanning, CAD/CAM
and Rapid Prototyping

119
INTRA ANATOMY AIRWAY REPLICATION DESIGN 3D SURFACE IMAGE 3dMD face™ system

120
HDPE CRANIAL HEMISPHERE IMPLANT
High-density porous polyethylene (HDPE)
BURN MASK
Insignia - 3D motion laser scanning
and CAD Software

REFERENCES
• Maxillofacial Prosthetics – Chalian
• Clinical maxillofacial Prosthetics - Thomas D Taylor
• Oral and maxillofacial rehabilitation - Buemer
• Textbook of Prosthodontics – D. Nallaswamy
• Materials of facial prosthesis: History and advance - International Journal of Contemporary Dental
and Medical Reviews · January 2015
• Classification, History, and Future Prospects of Maxillofacial Prosthesis – Hindawi International
Journal of Dentistry Volume 2019
127

REFERENCES
• Materials used in Maxillofacial Prosthesis – Barhate AR - Pravara Med Rev
• Maxillofacial prosthetic materials – S.S. Khindria et al, The Journal of Indian Prosthodontic Society /
January 2009 / Vol 9 / Issue 1
• An assessment of recent advances in external maxillofacial materials - Lewis and Castleberry,
Southern Research Institute and the University of Alabama, Birmingham, Ala.
• Materials and techniques in maxillofacial prosthodontic rehabilitation – Huber H and Studer S (DCNA)
• Pigments and their application in maxillofacial elastomers: A literature review - John J. Gary
128

REFERENCES
• Intrinsic and Extrinsic Stains & Colour Bleeding in Maxillofacial Prosthesis – P. Srivastava
• Retentive Aids Used In Maxillofacial Prosthesis – Yashwante B (IJCDS)
• Maxillofacial prosthesis : an insight into their retention and support – Sethi T and Kheur M
• Anaplastology – Padmaja – Journal of Dental Research and Review ● Apr-Jun 2015 ● Vol. 2 ●
Issue 2
• Maxillofacial Prosthetic Materials - An Inclination Towards Silicones – A. Mitra
129

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