Retention in maxillofacial prosthesis copy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

• Contents
 Introduction
 History
 Anatomic retention
• Intraoral consideration
Support
Retention
Stability
• Extra oral consideration

Mechanical retention
Attachments
Adhesives
Magnets
Implants
Conclusion
References

• Introduction

HISTORY
 2500 B.C EGYPTIAN PERIOD
• First historical report of facial prosthetic replacement
was attempted during the fourth dynasty 2613/2494
B. C

 200 A .D
• In china prosthesis were fabricated in lacquer
supported by a specific type of metallic
substructures .

 Ambroise Pare
• Has given us an excellent description of a simple
but very practical obturators for closing a
perforation in hard palate .

• Pare recommended the use of prosthetic nose
made up of silver and attached to the face by
strings

• He also advocated the use of a prosthesis to
replace ear and eye as well .

 Pierre Fauchard
• Fauchard designs for a palatal obturators

• The wings are in the shape of propellers which
can be folded together while being inserted and
spread out after insertion with key .

• In another type the retaining features is in the form
of a butterfly wing which is made to open by a key
after the closed wings have been inserted through
the palatal perforation .

• Another of Fauchard inventions
• Is the special spring which he devised for the
retention of upper and lower denture .
JPD 1965 page 554- 568

• Branemark and his associated first placed
modified osseointegrated fixtures in the cranial
bone skeletal for the purpose of retaining a
prosthetic ear in 1977.

Retention

Anatomic Retention
Intraoral
consideration Extra oral
Consideration

Anatomic retention
Intra oral consideration

Anatomic retention
• The success of intraoral retention relates to the
size and location of the defect and outcome of
the surgery.

Anatomic retention
Support
• Support is the resistance to movement of a
prosthesis toward the tissue .
• Residual maxilla and within the defect .

Residual maxilla support
• Primary area available for support are
• Residual teeth
• The alveolar ridge
• Residual hard palate

• The alveolar ridge support
• The size and shape of the ridge should be
consider
• Large ,broad ridge or the ridge with square or the
ovoid provide better support
(JPD 1978 vol 39 no 4 424-435)

• Residual hard palate support
• Broad flat palate is more conducive to support
than the high , tapering palate

With in the defect support
Floor of the orbit
Bony structures of the Pterygoid plate
Anterior surface of temporal bone
Nasal septum may used if the defect extends
beyond midline

RETENTION
• Retention is the resistance to vertical displacement
of the prosthesis .
 Residual maxilla retention
 Alveolar ridge retention

Within the defect retention
 Residual soft palate
 Residual hard palate
 Anterior nasal apertures
 Lateral scar band
 Height of lateral wall

• Residual soft palate retention
 Palatal seal
 Extension on superior surface of soft palate is
limited by the extend of the defect .

• Residual hard palate
 Objective of prosthesis extension is to provide
resistance to vertical and horizontal displacement

• Anterior nasal apertures
 Entered unilaterally or bilaterally
 Depending on the extent of the defect or beyond
the midline

• Lateral scar band
 skin superior to the junction tends to stretch
 creating an area above the scar band that can be
engaged by the obturators
 Minimized vertical displacement

• Height of lateral wall
 In addition to the physical engagement of the floor
structures mentioned the lateral wall of the defect
can be utilized for indirect retention .

STABILITY
 Stability is the resistance of prosthesis displacement
by functional forces .
 Rotation of prosthesis around the horizontal plane is
seen in fulcrum line .

• Anteroposterior
• Mediolateral
• Rotational
• Combination of any or all these direction

• Residual maxilla stability
 If natural teeth are present prosthesis framework
can prevent the movement in all three direction
 In edentulous patient , maximum extension of
prosthesis will minimized the movement.

• Within the defect stability
 Maximum extension of the prosthesis
 Maximum contact with the medial , anterior and
lateral walls of the defect

Occlusion
 Unstable prosthesis results if the occlusal
relationship doesnot maintain intimate prosthesis
contact with the supporting and retentive structures.

ANATOMIC RETENTION
EXTRA ORAL CONSIDERATION

• This necessitates the use of both hard and soft
tissue .
• Retention depends on location and size of
defects
• Tissue mobility or lack of undercuts
• Weight of the facial prosthesis

• Hard tissue act as a base against which to seat
the prosthesis
• Soft tissue prove to be more trouble because of
their flexibility , mobility lack of support .

MECHANICAL RETENTION
Temporary permanent

• Temporary mechanical retention
 Stainless steel wrought wire of 18 gauge size .
 some preformed wire clasps can be readily
incorporated to acrylic plate of prosthesis.
 Preformed stainless steel wire clasps include
Adams , arrowhead , Akers or Hawley labial wire

Permanent mechanical retention
Cast clasp other forms
Circumferential clasp
Cast wrought clasp
Combination clasp
Roach Akers clasp
Ring clasp

Permanent mechanical retention
Cast clasp other forms
Attachments
Adhesives
Magnets
implants
Swing lock device
Spring
Screws
Suction cups

CAST CLASP
• The clasp extends into an undercut of the
supporting tooth in order to gain retention.

Circumferential clasp
• Indicated –
 class III
 Modification space
 On the side of the arch opposite a unilateral
edentulous space
• Contraindicated-
 Class I

CAST WROUGHT COMBINATION
CIRCUMFERENTIAL CLASP
• In 1965 , Dr O.C. Applegate introduced a
modified wrought wire clasp assembly known as
the combination clasp .
• Indicated – class I or class II

Advantages
• Has thin light contact
• Can flex in all planes
• Adjustable
• Rigid reciprocal arm can compensates for any
orthodontic force applied by the retentive arm

Disadvantages
• Tedious lab work
• Easily break or distort
• Poor stability

T bar cast circumferential combination or Roach
Akers clasp
• This clasp provides a cervical approach to the
tooth surface
• Take distobuccal distolabial undercut
• Indicated
• Unilateral or bilateral distal extension

Contraindicated
• When mesial undercuts are presents
• It should not be used when height of contour is
placed closer to occlusal or incisal surface.

Ring or ring around clasp
• Indication
 tipped molars
• The ring clasp engages undercut by encircling
almost entire tooth from its point of origin .

• Disadvantages
• Difficult to adjust or repair
• Increased tooth surface coverage
• Contraindication
• If the bracing arm have to cross a soft tissue
undercut

• The loss of support of a removable partial denture
by a patient who has had a maxillolectomy causes
increased pressure , torque and lever action on
the associated hard and soft tissue.

ATTACHMENTS

Prefabricated attachments

 Attachments can be placed into cast crowns for
the best esthetic and mechanical retention.
 Most useful in rehabilitating cleft lip and cleft
palate cases .

Intracoronal precision attachment
• Advantages
• Esthetic
• Less bulky
• Stable
• Less food accumulation
• Decreases stresses in abutment

• Disadvantages
• Preparation of crown
• Complicated procedure
• Repair and replacement is difficult

• Examples are

Extracoronal attachments
• Indication
• Adequate vertical space
• Disadvantages
• Damages the gingiva distal to distal abutment
tooth
• Small dead space under the male portion
• Not as precise as intracoronal attachmentwww.indiandentalacademy.com

STUD ATTACHEMENTS
• E.g. Dalla bona , Rotherman
• Advantages
• Easy to adjust
• Less leverage
• Disadvantages
• Cannot be use with limited space

BAR ATTACHMENT
• E.g. Dolder and header
• Indication
• Bone loss around abutment
• Advantages
• Rigid splinting and
• cross arch stabilization

Disadvantages
• Difficult to maintain oral hygiene

AUXILLARY ATTACHEMENT
 Screw units
 Bolts
 Frictional devices
 Hinged flanges

• First given by Gillette in 1923
• Advantages
a)Adaptability to wide variety of clinical situations
b)Variations in tooth size & shape accommodated
c)Better crown contour in gingival area
Semi precision attachment/custom made

DISADVANTAGES:
a) Greater lab skill
b) Repair & replacement difficult
c) Wear resistance less(made of gold alloys)

ADHESIVES

• Adhesive can provide both intraoral and extra
oral defects .
• they aid in intraoral retention when surgical
defect is large
• when palate is flat
• The anterior posterior lateral septal wall with no
undercut .

•Missing tuberosities
•Patient with diminished salivary flow due to pre
and post radiation therapy.
(JPD 1992 68 943-9)

• Most modern prosthetic replacement are secured
with adhesives.
• All are readily available ,easily applied and can
provide satisfactory retention for limited period of
time.
(JPD 1980 vol 43 no 5)

Five commonly used adhesive

• Most commonly used adhesive .
• Strongest bond with skin .
• Care should be taken while using on compromised
skin surface .
• Can easily removed from skin .
• Difficult to remove from silicone
Dow corning 355

PSAI and PROS AIDE
• Not easily removed from the skin surface

Technique
 Apply adhesive 6 to 7mm periphery of the surface
 Repeated cleaning might lead to breakage
 Not to apply at the edges of the prosthesis to
increase the life of the prosthesis

Adhesive remover
• Adhesive remover are used to remove adhesive
from the skin .e.g. plastic remover , acetone

• Cotton bud is socked in remover and apply slowly
under and around the fitting surface of the
prosthesis.
Technique to remove adhesive

• Some patient may develop allergic and irrigational
response .
• Poor hygiene may limit the effectiveness of a
prosthesis.
• Damage external pigmentation.
( JPD 1980 vol 43 no 5 )
Disadvantages of adhesive

• Difficulty in applying the adhesive or adhesive
retained prosthesis repeatedly to the proper
position.

Sebum – fatty substance release from gland can
cause barrier between skin and adhesive .
Moisture – can affect the action of adhesive
Hair- prevent adhesive layer contacting skin .
Solvent – continue use of removal solvent can be
allergic to skin
Problem with adhesive

To be continued…………www.indiandentalacademy.com

MAGNETS

History
• Magnets in maxillofacial
Prosthesis have been used for
decades to reconstruct large
defect .

• Federick rehabilitated a patient with large orofacial
defect using a 2-component obturator that was
locked to each other with the help of magnets.

• advances in technology have made avail-able a
new family of magnetic alloys based on cobalt and
other rare earth metals.
• They are small but strong and can be used for
dental purposes for retention.

• The mutual attraction of unlike poles has been
utilized successfully to assemble multicomponent,
maxillofa-cial prostheses and even sectional
dentures

• Magnets were first introduced for applications in
dentistry in the year 1953 in the field of
orthodontics.

• 1960 as retentive devices for over dentures,
removable partial dentures, and maxillofacial
prostheses.

• Magnets is the most efficient means of providing
combined prostheses with retention and stability in
patient with deformities requiring complex defect .
• Majority of prosthesis with magnets are sectioned
and have a magnet in each section .

• When section are assemble properly
• Magnets are attracted to each other and retain the
section
( The Journal of Contemporary Dental Practice Vol 8 No 7 2007)

• Ease of placement
• easy replacement
• small size with strong attractive forces
• Ease of cleaning
• Can be used with implant supported prosthesis
• They can be embedded on thin sections of
acrylic
Advantages of magnets

• Tissue undercuts can be used for additional
retention of prosthesis .
( JPD 1984 VOL 52 NO 4 page 556-558)

• Low corrosion resistance
• High cost
• Cytotoxic effect
Disadvantages of magnets

 The challenge in magnets as retentive elements
in MFP depends on ability to resist corrosion
 The development of samarium iron nitride as
magnetizeable material may offer better corrosion
resistance
 use of magnets in prosthodontics may be viewed
with much interest in future

IMPLANTS IN MAXILLOFACIAL PROTHESIS

History
• In 1975 Branemark considered that skin penetration
implant may be possible .
• In 1977 Branemark and his coworkers Installed
specifically designed Implants
• in the mastoid region.

• In 1979 these same workers placed the first
implants in the mastoid region to retain an
auricular prosthesis .
• Since these developments , craniofacial
osseointegration has become an accepted part of
head and neck reconstruction.

• Implants are placed into the residual bone and then
used for retention , support and stability of a
prosthesis .
• The use of similar implants in extra oral site is
growing popularity .

• Osseointegration technology offers the first real
promise for overcoming the disadvantages of
adhesive in the appropriate patient .
( JPD 1988 VOL 55 NO 5 page 600-605)

Indication
 Extra oral implants are used for retaining eye , ear
and nose maxillofacial prosthesis .
 Patient with cartilaginous or peripheral tissue or
thick layer of skin .

Contraindication
• Poor immune defense
• Use of steroids
• Neoplasm as a result of chemotherapy
• Uncontrolled endocrinopathy

• Relative contraindication
• Diabetes mellitus
• Irradiated bone or ongoing radiotherapy
• Inflammation of implant site

Retention system in extra oral implant
• Osseointegration implants in craniofacial
reconstruction improves prostheses retention ,
stability , comfort and safety for a patient .

Bar clip attachment
 Most commonly used
 metallic bar clip system
present expensive laboratorial procedure

• Advantages
 Good load distribution on the implants.
• Disadvantages
 risk of damaging the bar during construction of
prosthesis
( JPD 1996 vol 76 page 603)

Magnet systems
 Consists of a magnet cap that
is threaded onto the abutment
and a magnet is placed onto the
tissue surface of the prosthesis.

Indicated
 When abutment are not parallel
 In orbital and auricular prosthesis with or without bar
clip system
 Swallow defects with insufficient space for a bar and
clip attachment .

• Advantages
• Ease of removing and inserting
• Makes the wearing and daily care beneficial
• Easy hygiene control
• Reduce probability of infection

Ball attachment system
 Three implants creating
a tripod
 Provide satisfactory
retention and stability

• Indication
• Shallow defects as they occupy less space
behind the prosthesis .

• Advantages of ball system
• Induces less stress to implant
• Absence of bar optimizes more hygiene
• Provides freedom of movement
• Disadvantages
• Wear of the rubber ring

Slant lock system
• Based on active engagement

• System provides security to patient because the
prosthesis keeps in position until the system is
unlocked .
• Disadvantages
• Silicone tear

• Implant for orbital prosthesis
• Superior , lateral , and inferior rims are possible
site for implant
• 3 to 4mm implants are needed

• For the large defect it is best to connect the
abutment with a bar .
( JPD 1993 70 329-332)

Auricular defect

 Bar can be extended 10 to15mm
 Two retention system are used gold alloy bar ,
and magnets

 In gold bar system 2mm gold cylinder is
attached to the abutment .
retention clip system incorporated into
prosthesis providing attachment to the bar .

 Excellent retention for the prosthesis .
 However it may limit the access for performing
hygiene procedures , require extension of the
base of the prosthesis to cover the bar .

• Second retention technique is use of magnets .
• Magnets are connected to abutment.
• 6mm diameter and 2mm thickness .
• The bar structure must be designed to contain
housings to hold magnets
• Corresponding magnets are placed within the
silicone prosthesis .

• Alternative technique employed only the use of
magnets
• This technique employs a magnet keeper that
connects directly to the abutment thus elimination
the need for a retaining bar .

Nasal defects
 Implant can be placed in maxillary
or frontal bone
 4mm implant s are required
 Positioned in each lateral rounded nasal
eminence

• The prosthesis is completed before the placement
of implant .
• Position of the abutments and the retentive
elements do not compromise the contours of the
prosthesis

• Split thickness graft is needed .
• The septal cartilage must be reduced surgically
• Provide room for the prosthesis to engage the
lateral walls of the defect
• Increase stability of prosthesis

Implant design for maxillectomy defect
• Prosthetic rehabilitation  close oral & nasal
cavities, substitute teeth and anterior soft tissues
of the face.
• Anchorage - skeletal components are removed
- zygoma & pterygoid region used

Implant design for midfacial defect
• Midfacial defects often result from ablative
procedures used to control malignancies of nasal
& maxillary structures.
• As the size of defect increases, complexity of
prosthetic rehabilitation increases.

 Jenson DT et al (1992):
• Described available sites for the implant
placement in the midfacial region
• Suggested craniofacial site classification for the
osseointegrated implants – alpha, beta & delta
sites

BONE ANCHORED HEARING AIDS(BAHA)

• The Baha is a surgically implantable system for
treatment of hearing loss that works through
direct bone conduction

Indication
• chronic ear infections,
• congenital external auditory canal Artesia
• single sided deafness who cannot benefit from
conventional hearing aids

The Baha

• The titanium implant is placed during a short
surgical procedure and over time naturally
integrates with the skull bone

• One stage surgical procedure ↓LA.
• Placement of Ti implant & abutment in mastoid
cortex.
• Maintenance of hair free area around the
abutment is required.
• After osseointegration, abutment is loaded with
the mechano-electric transducer system.

• For hearing, the sound processor transmits
sound vibrations through the external
abutment to the titanium implant.
• The vibrating implant sets up vibrations
within the skull and inner ear that finally
stimulate the nerve fibers of the inner ear,
allowing hearing.

Advantages of implants
• Aesthetic is better
• Implant simplify the cleaning procedures
• Life of prosthesis is long
• Implant retained prosthesis have provided the
opportunity to participate in routine activities .
• Provide ability to function in society with
confidence
DCNA 1998 vol 42 num 1www.indiandentalacademy.com

Other types
• Screws, swing lock device, suction cups surgical
sutures, spectacles etc……..

• Conclusion

• References
• Varoujan A Chalian , Joe B Drane ,S Miles
Standish Maxillofacial prosthetics
• Beumer J, Curtis TA ,Firtell DN Maxillofacial
Rehabilitation
• HAROLD PRISKEL, Precision attachment in
prosthodontics
• JPD 1978 vol 39 no 4 ,424-435

• JPD 1992 vol 68 , 934-949
• JPD 1980 vol 43 ,
• JPD 1984 vol 52 no 4 556-558
• JPD 1984 vol 55 no 5 600- 605
• JPD 1996 vol 76 603
• JPD 1993 vol 70 329-332
• The journal of contemporary dental practice vol 8
no 7 2007

• JPD 1965 page 554- 568
• DCNA 1998 vol 42 num 1

Retention in maxillofacial prosthesis copy

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