Retention in maxillofacial prosthesis copy

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Transcript of Retention in maxillofacial prosthesis copy

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INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

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• Contents

Introduction

History

Anatomic retention

• Intraoral consideration

Support

Retention

Stability

• Extra oral consideration

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Mechanical retention

Attachments

Adhesives

Magnets

Implants

Conclusion

References

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• Introduction

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HISTORY

2500 B.C EGYPTIAN PERIOD

• First historical report of facial prosthetic replacement

was attempted during the fourth dynasty 2613/2494

B. C

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200 A .D

• In china prosthesis were fabricated in lacquer

supported by a specific type of metallic

substructures .

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Ambroise Pare

• Has given us an excellent description of a simple

but very practical obturators for closing a

perforation in hard palate .

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• Pare recommended the use of prosthetic nose

made up of silver and attached to the face by

strings

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• He also advocated the use of a prosthesis to

replace ear and eye as well .

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Pierre Fauchard

• Fauchard designs for a palatal obturators

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• The wings are in the shape of propellers which

can be folded together while being inserted and

spread out after insertion with key .

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• 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 .

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• Another of Fauchard inventions

• Is the special spring which he devised for the

retention of upper and lower denture .

JPD 1965 page 554- 568

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• Branemark and his associated first placed

modified osseointegrated fixtures in the cranial

bone skeletal for the purpose of retaining a

prosthetic ear in 1977.

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Retention

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Anatomic Retention

Intraoral consideration

Extra oralConsideration

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Anatomic retention

Intra oral consideration

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Anatomic retention

• The success of intraoral retention relates to the

size and location of the defect and outcome of

the surgery.

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Anatomic retention

Support

• Support is the resistance to movement of a

prosthesis toward the tissue .

• Residual maxilla and within the defect .

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Residual maxilla support

• Primary area available for support are

• Residual teeth

• The alveolar ridge

• Residual hard palate

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• 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)

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• Residual hard palate support

• Broad flat palate is more conducive to support

than the high , tapering palate

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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

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RETENTION

• Retention is the resistance to vertical displacement

of the prosthesis .

Residual maxilla retention

Alveolar ridge retention

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Within the defect retention

Residual soft palate

Residual hard palate

Anterior nasal apertures

Lateral scar band

Height of lateral wall

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• Residual soft palate retention

Palatal seal

Extension on superior surface of soft palate is

limited by the extend of the defect .

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• Residual hard palate

Objective of prosthesis extension is to provide

resistance to vertical and horizontal displacement

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• Anterior nasal apertures

Entered unilaterally or bilaterally

Depending on the extent of the defect or beyond

the midline

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• 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

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• 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 .

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STABILITY

Stability is the resistance of prosthesis displacement

by functional forces .

Rotation of prosthesis around the horizontal plane is

seen in fulcrum line .

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• Anteroposterior

• Mediolateral

• Rotational

• Combination of any or all these direction

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• 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.

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• Within the defect stability

Maximum extension of the prosthesis

Maximum contact with the medial , anterior and

lateral walls of the defect

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Occlusion

Unstable prosthesis results if the occlusal

relationship doesnot maintain intimate prosthesis

contact with the supporting and retentive structures.

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ANATOMIC RETENTION

EXTRA ORAL CONSIDERATION

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• 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

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• 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 .

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MECHANICAL RETENTION

Temporary permanent

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• 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

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Permanent mechanical retention

Cast clasp other forms

Circumferential clasp

Cast wrought clasp

Combination clasp

Roach Akers clasp

Ring clasp

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Permanent mechanical retention

Cast clasp other formsAttachments

Adhesives

Magnets

implants

Swing lock device

Spring

Screws

Suction cups www.indiandentalacademy.com

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CAST CLASP

• The clasp extends into an undercut of the

supporting tooth in order to gain retention.

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Circumferential clasp

• Indicated –

class III

Modification space

On the side of the arch opposite a unilateral

edentulous space

• Contraindicated-

Class I www.indiandentalacademy.com

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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

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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

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Disadvantages

• Tedious lab work

• Easily break or distort

• Poor stability

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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

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Contraindicated

• When mesial undercuts are presents

• It should not be used when height of contour is

placed closer to occlusal or incisal surface.

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Ring or ring around clasp

• Indication

tipped molars

• The ring clasp engages undercut by encircling

almost entire tooth from its point of origin .

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• Disadvantages

• Difficult to adjust or repair

• Increased tooth surface coverage

• Contraindication

• If the bracing arm have to cross a soft tissue

undercut

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• 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.

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ATTACHMENTS

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Prefabricated attachments

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Attachments can be placed into cast crowns for

the best esthetic and mechanical retention.

Most useful in rehabilitating cleft lip and cleft

palate cases .

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Intracoronal precision attachment

• Advantages

• Esthetic

• Less bulky

• Stable

• Less food accumulation

• Decreases stresses in abutmentwww.indiandentalacademy.com

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• Disadvantages

• Preparation of crown

• Complicated procedure

• Repair and replacement is difficult

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• Examples are

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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 attachment www.indiandentalacademy.com

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• Examples are

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STUD ATTACHEMENTS

• E.g. Dalla bona , Rotherman

• Advantages

• Easy to adjust

• Less leverage

• Disadvantages

• Cannot be use with limited space

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BAR ATTACHMENT

• E.g. Dolder and header

• Indication

• Bone loss around abutment

• Advantages

• Rigid splinting and

• cross arch stabilization

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Disadvantages

• Difficult to maintain oral hygiene

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AUXILLARY ATTACHEMENT

Screw units

Bolts

Frictional devices

Hinged flanges

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• 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

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DISADVANTAGES:

a) Greater lab skill

b) Repair & replacement difficult

c) Wear resistance less(made of gold alloys)

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ADHESIVES

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• 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 .

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•Missing tuberosities

•Patient with diminished salivary flow due to pre

and post radiation therapy.

(JPD 1992 68 943-9)

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• 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)

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Five commonly used adhesive

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• 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

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PSAI and PROS AIDE

• Not easily removed from the skin surface

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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

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Adhesive remover

• Adhesive remover are used to remove adhesive

from the skin .e.g. plastic remover , acetone

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• Cotton bud is socked in remover and apply slowly

under and around the fitting surface of the

prosthesis.

Technique to remove adhesive

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• 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

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• Difficulty in applying the adhesive or adhesive

retained prosthesis repeatedly to the proper

position.

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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

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

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MAGNETS

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History

• Magnets in maxillofacial

Prosthesis have been used for

decades to reconstruct large

defect .

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• Federick rehabilitated a patient with large orofacial

defect using a 2-component obturator that was

locked to each other with the help of magnets.

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• 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.

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• The mutual attraction of unlike poles has been

utilized successfully to assemble multicomponent,

maxillofa-cial prostheses and even sectional

dentures

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• Magnets were first introduced for applications in

dentistry in the year 1953 in the field of

orthodontics.

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• 1960 as retentive devices for over dentures,

removable partial dentures, and maxillofacial

prostheses.

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• 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 .

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• 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)

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• 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

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• Tissue undercuts can be used for additional

retention of prosthesis .

( JPD 1984 VOL 52 NO 4 page 556-558)

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• Low corrosion resistance

• High cost

• Cytotoxic effect

Disadvantages of magnets

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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

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IMPLANTS IN MAXILLOFACIAL PROTHESIS

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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.

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• 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.

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• 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 .

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• 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)

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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 .

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Contraindication

• Poor immune defense

• Use of steroids

• Neoplasm as a result of chemotherapy

• Uncontrolled endocrinopathy

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• Relative contraindication

• Diabetes mellitus

• Irradiated bone or ongoing radiotherapy

• Inflammation of implant site

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Retention system in extra oral implant

• Osseointegration implants in craniofacial

reconstruction improves prostheses retention ,

stability , comfort and safety for a patient .

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Bar clip attachment

Most commonly used

metallic bar clip system

present expensive laboratorial procedure

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• Advantages

Good load distribution on the implants.

• Disadvantages

risk of damaging the bar during construction of

prosthesis

( JPD 1996 vol 76 page 603)www.indiandentalacademy.com

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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.

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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 .

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• Advantages

• Ease of removing and inserting

• Makes the wearing and daily care beneficial

• Easy hygiene control

• Reduce probability of infection

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Ball attachment system

Three implants creating

a tripod

Provide satisfactory

retention and stability

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• Indication

• Shallow defects as they occupy less space

behind the prosthesis .

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• 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

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Slant lock system

• Based on active engagement

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• System provides security to patient because the

prosthesis keeps in position until the system is

unlocked .

• Disadvantages

• Silicone tear

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• Implant for orbital prosthesis

• Superior , lateral , and inferior rims are possible

site for implant

• 3 to 4mm implants are needed

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• For the large defect it is best to connect the

abutment with a bar .

( JPD 1993 70 329-332)

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Auricular defect

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Bar can be extended 10 to15mm

Two retention system are used gold alloy bar ,

and magnets

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In gold bar system 2mm gold cylinder is

attached to the abutment .

retention clip system incorporated into

prosthesis providing attachment to the bar .

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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 .

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• 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 .

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• 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 .

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Nasal defects

Implant can be placed in maxillary

or frontal bone

4mm implant s are required

Positioned in each lateral rounded nasal

eminence

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• 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

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• 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

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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

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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.

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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

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BONE ANCHORED HEARING AIDS(BAHA)

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• The Baha is a surgically implantable system for

treatment of hearing loss that works through

direct bone conduction

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Indication

• chronic ear infections,

• congenital external auditory canal Artesia

• single sided deafness who cannot benefit from

conventional hearing aids

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The Baha

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• The titanium implant is placed during a short

surgical procedure and over time naturally

integrates with the skull bone

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• 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.

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• 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.

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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

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Other types

• Screws, swing lock device, suction cups surgical

sutures, spectacles etc……..

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• Conclusion

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• 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 ,424-435www.indiandentalacademy.com

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• 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 2007www.indiandentalacademy.com

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• JPD 1965 page 554- 568

• DCNA 1998 vol 42 num 1

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