Post on 06-Jul-2015
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.