Retention of maxillofacial prosthesis./cosmetic dentistry course

Retention In Maxillofacial
Prosthodontics
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

In maxillofacial prosthetics there exists a
broad variety of types of methods for
gaining retention, stabilization, and
immobilization as required. Close
evaluation of a case with the surgeon
before and during surgery helps in finding
means to create irregular defects for
enhancing anatomic retention.17
The following methods of retention are
discussed for intraoral and extraoral
prostheses. www.indiandentalacademy.com

Intraoral Prosthesis and Its Retention
Anatomic Retention
Intraoral retention includes the use of both
hard and soft tissues, that is to say, teeth
and mucosal and bony tissues. The success
of intraoral retention relates to the size and
location of the defect and the outcome of the
surgery.
Anatomic undercut areas are a welcome
feature in the postsurgical case. These may
be found in the palatal area, cheek,
retromolar, labial, septal, posterior nasal
pharyngeal, or anterior nasal spine areas.www.indiandentalacademy.com

Large alveolar ridges and high palatal vaults
generally provide more retention than flatter ridges.
This anatomy may still not provide a completely
stable replacement, depending upon the presence of
lower natural teeth or previously acquired undesirable
denture habits by the patient.
In the larger defect cases encompassing both the
maxilla and mandible, as in a commando operation,
skill, ingenuity, and the operator's thoroughness,
coupled with the patient's adaptive ability, can result
in a "one of a kind" successful prosthesis.
Additional aids to anatomic retention include proper
occlusion, proper post dam, and surface adhesion.www.indiandentalacademy.com

A melanoma of the palate. B. Postsurgical view of the excised palate with anterior
ridge intact for retention purpose. C. obturator inserted and retained by existing
soft and hard tissues. D. prostheses in occlusionwww.indiandentalacademy.com

Mechanical Retention
Under this category, the operator has a myriad of
devices and proven techniques to consider and use
as the case demands.
Temporary Mechanical Retention
This may be a stainless steel wrought wire of 18-
gauge size which can be quickly adapted to a cast of
the remaining teeth to retain the temporary
prosthesis during the healing period. Some wire
clasps come preformed and can be readily
incorporated into the acrylic palate of an obturator or
saddle in a lower prosthesis or a previously existing
denture.
Other preformed stainless steel wire clasps include
Adams, Arrowhead, Akers, Roach, or Hawley labial
wires. www.indiandentalacademy.com

Preformed stainless steel bands or crowns may be
adapted to a child or adult to increase retentive form
of a mutilated or conical tooth. Extra soldered lugs
or bands with prewelded brackets can be used to
provide undercuts on these crowns for better clasp
retention.
Orthodontic bands
and prewelded
brackets to retain
temporary prosthesis

When a maxillofacial prosthesis is not available, an
old denture can be wired in place to obdurate a
maxillary hemisection. This wire extension is internal
to the infraorbital or zygoma bones.
Intraoral temporary retention may also be
illustrated by the construction and insertion of a
tantalum tray to help retain a rib graft or fractured
mandibular segments during healing.
Bilateral
perforated
tantalum trays
used for
immobilization of
mandibular
segmentswww.indiandentalacademy.com

Permanent Mechanical Retention:
Cast Clasps.
The most common method for retaining
prosthesis uses a cast metal clasp which enters an
undercut. The properly designed and fabricated clasp
will provide stability, splinting, bilateral bracing, and
reciprocation, as well as retention.
Various qualities of clasp design influence the degree
of retention. These include the length, the diameter,
the taper, the material and the general contours of the
retentive clasp, as well as the depth of the undercut
used. www.indiandentalacademy.com

RECIPROCATING CLASP ARM :
A retentive clasp is designed to deform as it
passes over the height of contour on the abutment
tooth and to return to its original passive state upon
coming to place in the infrabulge area. The lateral
component of force necessary to cause the clasp arm
to flex is counteracted by an equal and opposite force
against the tooth surface.

Occlusal Rest :
This part of the direct retainer is that unit of the
partial denture frame designed specifically to fit
within a prepared rest seat in the abutment tooth. It
serves several purposes to provide a positive point of
orientation between the partial denture and its
abutment; to resist overseating the partial denture
and subsequent impingement of the periodontal
tissues; and to serve as a point for the transmission
of stress to the abutment tooth as nearly along its
long axis as possible

TYPES OF EXTRACORONAL DIRECT RETAINERS
Cast Circumferential Clasp:
The cast circumferential clasp, of Akers clasp as
it is sometimes called, is one of the most frequently
used clasp because of its reliability, ease of fabrication,
and adaptability..

Cast circumferential clasp

Cast-wrought Combination Circumferential Clasp
This is an adaptation of the first clasp from described,
and it substitutes a contoured wrought wire for the
cast clasp on the retention side. It may be used
whenever the fully cast circumferential clasp is
indicated but, in addition, it may be used in a free end
saddle situation.

Wrought - cast combination Akers clasp

T-Bar Cast Circumferential Combination or
Roach-Akers Clasp
This clasp provides a cervical approach to the
tooth surface and affords the opportunity to take
advantage of an existing distobuccal or distolabial
undercut. It is indicated in either unilateral or
bilateral distal extension situations.
Cast Roach -
Akers
combination
clasp.

.
Ring or Ring-around Clasp
This clasp form also uses an undercut
adjacent to the edentulous area but reaches it by
circumnavigating the tooth. It is especially
applicable for use on lone-standing molar
abutments distal to the edentulous space that are
tipped or tilted to an exorbitant degree.

Mandibular molar
ring clasp and
modification
There are other clasp forms, and modifications
thereof, that lend themselves to certain situations;
however, those illustrated can serve adequately as a
rather complete armamentarium for the restorative
dentist. www.indiandentalacademy.com

Prefabricated Precision Attachments
These attachments can be placed into cast
crowns for the best in esthetic and mechanical
retention. Construction problems exist here, and
much more precise measures are necessary for
success.
.
Semiprecision Attachments, Custom-made
This attachment is formed in the wax pattern,
using a specially shaped mandrel mounted on the
parallelometer. A reciprocal arm is always necessary.

Snap-on Attachment
This is also a preformed precious-metal precision
piece designed to retain and to stabilize a prosthesis.
A Baker bar or Anderson bar is the rod connecting
two abutment crowns, and the clip engages this rod.
A. Baker snap-on attachments soldered to the cast frame work. B. cross-arch
splinting, using 11,gauge barwww.indiandentalacademy.com

Overlay (Telescoping) Crown and Thimble
Crown
This is often used when an overlay denture is
planned or an extremely malposed tooth is
needed for stability but is not considered for
orthodontia. It is also used when a major
change in the vertical or centric dimension is
indicated, as in cleft lip-cleft palate, prognathic
mandibles or resected mandibles.

A thimble crowns cemented on
prognatic patient. B. telescoping
crowns imbedded in the denture.
C. superimposed denture inseted
in the mouth to correct the vertical
and centric dimensions.
(Courtesy of Dr. J. Borkowski).www.indiandentalacademy.com

Magnets AB
Magnetized metal discs in denture teeth or magnetized metal
rods can be inserted into the edentulous ridge and the
overlying saddle extension or can be easily inserted into the
dentures themselves. Magnetic retention is at the most an aid
but not of itself an effective method to properly retain a
nonstabile denture. This consideration may be useful in a
hemimaxillectomy case or extremely atrophied ridges.
A. Stock repelling magnets. B. Magnets invested and waxed under
the occlusal surface.

Gate Type or swing Lock Device:This retentive aid helps gain
partial retention for many loose or periodontally involved teeth.
This retentive means can be used when most other methods
should be considered first.
obturator is retained in the mouth by a gate type device.

Intermaxillary "George Washington" Springs
These come preformed and can be inserted into
an upper and lower set of dentures to help stabilize
them on the ridges during function.
A."George Washington" spring inserted in the buccal flanges of
maxillary and mandibular dentures. B. maxillary obturator is retained
by "George Washington" springs.www.indiandentalacademy.com

Auxiliary Retentive Devices
These include buccal-lingual continuous clasp, valve seal.
Furchard wing device for clefts, guide planes, surface
adhesion, and denture surface adhesion, devices such as
Porcelene and Durabone.
Screws
These are specially made custom parts.
Implants
Implants include tantalumtray, acrylic mandible and wire, and
intraosseus wire.
Suction Cups
Inflatable balloon suction cups are used for maxillary resection.
Adhesives
These become necessary to aid retention when the surgical
wound is large, the palate is flat, the anterior –posterior lateral
septal wall is not undercut but rather angles away from the
natural palate, the maxillary tuberosities are nonexistent, the
soft tissue undercuts in the

EXTRAORAL RETENTION
Anatomic Retention
Hard tissue
Soft tissues

A, right orbital exenteration.
B. tissue side of orbital
prosthesis and ocularrosthesis.
C. orbital prosthesis retained by
tissue undercuts and auxillary
nasal extension

MECHANICAL RETENTION
Additional retention is mostly needed in unusual
cases such as large defects involving half of the face
or heavily radiated tissues when the use of adhesives
is not feasible. It is advisable to use eyeglasses as an
indirect mechanical retention which at the same time
hides the margins of the prosthesis. The eyeglasses
should be free of and not a part of the prosthesis, In
addition to eyeglasses, an elastic strap may be of use
to hold the glasses on and help retain the prosthesis.

Eyeglasses are seated
over the auxillary nasal
extension. Also note lateral
button and rod for
additional support when
adhesive is
contraindicated.www.indiandentalacademy.com

A, extensive left facial defect. B. facial prosthesis retained by
eyeglasses, button, rod and nasal
extension.

Magnets
These may be imbedded in a nasal prosthesis or
orbital prosthesis to help secure it to a maxillary
obturator which may be in contact with the above
prosthesis.
Highton R60 produced magnetic systems were
chosen for testing, five closed field systems and one
open field system. The closed field systems were (1)
Innovadent, (2) Magnedent (large and medium), and
(3) Jackson (Solid State Innovation) regular and mini
magnets.
Six magnet-keeper systems were tested to
determine the relationship between an air gap and the
resulting breakaway force. The maximum retention
was obtained, when the magnet and keeper were in
apposition.

Snap Buttons and Straps
These are also used on a large extraoral
prosthesis.
Adhesives
Retention can be enhanced and may rely
entirely on the use of a surgical grade extraoral
adhesive. In general, each material provides its own
adhesive because of its inherent physical and
chemical properties. The adhesives aid retention,
marginal seal, and border adaptation. This secures
the prosthesis against accidental dislodgment.
Most modern prosthetic replacements are
secured with adhesives. These may include
interfacing pastes, liquids, sprays, or double-coated
tapes. All are readily available, easily applied, and
can provide satisfactory retention for limited periods of
time.

Mucosal Inserts:
The patient who has been edentulous and has
an atrophic maxilla has few alternatives for the
security and function of a prosthesis. The atrophy of
the alveolar ridge, in the maxilla, does not usually
allow sufficient depth of bone in the posterior region
in relation to the floor of the maxillary sinus for the
placement of endosteal implants. Similarly, atrophic
resorption of the mandibular alveolar ridge precludes
endosteal implant reconstruction due to the proximity
to the inferior alveolar canal and its contents.

Two rows of inserts are usually fabricated into the
tissue-bearing surface of the denture. One row is on
the crest of the ridge from the bicuspid region
posteriorly and the other is on the palatal slope.
Fourteen inserts are usually inserted. The inserts
should be placed sufficiently apart so there is no
tissue impingement between them, therefore, god
hygiene can be maintained.
Combination of anatomic, Mechanical, and
Adhesive Retention
Large facial replacements need to use all
available means of retention, The prudent use of
some or all available retentive means plus any
original improvisation by the prosthodontist can lead
to better stability and retention.www.indiandentalacademy.com

Resilient lining material for the retention of
maxillofacial prostheses
Resilient lining materials have taken their place
in complete denture prosthodontics since their first
reported clinical application in 1943. On denture-
bearing areas (basal seat) where thin mucosa is
located over sharp residual alveolar ridge crests, the
stresses of mastication tend to be localized, resulting
in tissues which are overloaded. Such tissues are
frequently painful and subject to recurrent traumatic
ulceration. When resilient denture liners cover these
tissues they artificially replace the missing connective
tissue of the submucosa, which when present permits
a more equal distribution of the occlusal loads
imposed on the basal seat.www.indiandentalacademy.com

Retention of maxillofacial prosthesis./cosmetic dentistry course

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