Precision attachments1 /certified fixed orthodontic courses by Indian dental academy

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


Contents
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Introduction
History
Uses
Goals
Mechanism of action
Indications
Contraindications
Advantages
Disadvantages
Classification

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Materials used in attachment fabrication
Treatment planning
The free end saddle
The bounded saddle
Over dentures
Auxiliary attachments
Milling using a precision parallelometer
Use of precision attachments with implants
Conclusion
Bibliography

Introduction
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Precision attachments offer considerable
advantages in dentistry because of their
flexibility.
Nevertheless they have in the past been largely
ignored by most dental professionals for
understandable reasons.
Precision attachments consist of two halves, a
matrix and a patrix, that form a precise but
separable joint.

Precision attachments are defined as ;
A retainer used in fixed and removable
prosthesis construction consisting of a metal
receptacle and a closely fitting part. The
former is usually contained within the normal
or expanded contours of the crown and the
later is attached to the pontic or denture
framework.
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Synonyms
Internal attachments
 key and key-way attachments
 parallel attachments
 slotted attachment
Male attachment
female attachment
-patrix
-matrix
-flange
-slot
-insert, fitting part
-receptacle
-key
-keyway, crypt
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History
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Prior to 1888, both winder and parr invented devices
which were clearly attachments in principles and
construction.
In 1906 Dr. Herman E.S. Chayes invented a
detachable suspender device which formed the
fundamental feature of his dental attachment.
In 1912 he designed the Chayes attachment called
bucco-lingual attachment which forms the basic
pattern for the modern frictional grip attachment.
1951 Mc collum made the greatest progress in the
development of precision attachment.

Uses
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They are used to overcome alignment
problems where abutments have differing
paths of withdrawal.
As connecters in fixed partial denture
construction.
To retain removable partial dentures.
To retain overdentures.

Goals
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To provide an efficient masticatory
replacement of lost dental organs.
To relate the designed platform to the available
tooth support.
To allow normal anatomic forms to the
abutment teeth.


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Should be removable and replaceable without
stress and strain on the abutment teeth.
Should be capable of being tissue supported in
a controlled manner.
Should allow for various Occlusal patterns.
Should provide many years of comfortable
service.

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To have minimum amount of tooth structure
removed.
To place minimum amount of strain on
abutment teeth.
To be esthetically acceptable.


Mode of action of precision
attachments
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Friction
Binding
Wedging of conical bodies
Internal spring loading
Active retention


Friction:
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It occurs when parallel walls of
closely fitting bodies pass over one
another.
The frictional force is directly related
to the area of the opposing surfaces
as well as to the length of axial walls.
The shape of the passage also plays a
substantial role.


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The holding ability of the frictional
attachments can be enhanced by addition of
active retention elements .

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They are
spring loaded bolts or plungers.
Ring springs
Leaf springs
Bolts
Rubber devices.

Binding:
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It occurs when a parallel walled
body tips with in the receptor site.

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Eccentric loads or frictional
elements produce tipping
movement,which enhances trans
additional binding effect
significantly increases resistance to
withdrawal.

Wedging of conical bodies:
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Friction comes to play only
in the terminal position and
is lost as soon as the bodies
began to separate.


Internal spring loading
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This is produced by a clip with in
a cylinder.
The friction with in retainers is
often increased by loading with
internal spring clips.
Slots in the male portion allows
the pressure to be adjusted.


Active retention:
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That is when one body must be
temporarily deformed to be
withdrawn from its fully seated
position.
Active retention means a physical
obstruction to separation of other
parts.
One part must undergo elastic
deformation before separation can
occur.

Indications
Depending on what the attachment is designed
to accomplish.
 Primary indication is for clasp elimination
when esthetics is of prime importance.
 For patients with reduced periodontal support.
 In patients where cross arch stabilization is
desired.

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The attachment is indicated in combination with
fixed and removable prostheses.

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The attachment is indicated where removable
partial denture design require stress equalization
which is of paramount importance.

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Long span edentulous areas.

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To stabilize unilateral saddles.

Contraindications
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Poor mental attitude of the patient is a definite
contraindication.
Poor oral hygiene.
One of the primary contraindications for these
prosthesis is space, whether it be vertical,
bucco-lingual, mesio-distal, circumferential, or
interproximal.
In healthy mouths not requiring restoration for
other reasons.

Advantages
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The principal advantage of attachments for
removable partial denture is esthetics.
Retention is an advantage for overdentures
abutments.
Stress distribution.
Cross arch stabilization.


Disadvantages
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The cost of the service is major factor.
Attachments are expensive.
Additional post-insertion care is required.
Additional chair and laboratory time is needed.
Greater experience and knowledge on the part
of the dentist and laboratory technician are
essential.
Require repair and replacement.

Classification


Classified in number of ways:
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Based on fabrication
1.Semi precision
2.Precision.
Based on function
1.Resilient
2. Non-resilient.
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By Ray
Active attachments
e.g.: split patrix, crismani.
Passive attachments
e.g.: passive mega attachments


By Collin. R. Corwell.
Based on the shape and location
1.coronal-Intracoronal ---frictional
mechanical
-Extra coronal eg:Dalbo hinge
- circumcoronal eg:Telescopic crown
2.Radicular-eg:Rotherman
3.Interdental-eg:Ackerman
4.Auxiliary-eg:Ipsoclip
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Based on location or placement [by preiskel]
1.Intracoronal
2.Extracoronal
3.Studs
4.Bars
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According to Gareth Jenkins
1.Extra Coronal
2.Intra Coronal
3.Auxiliary
4.Achors
5.Bars


Extra Coronal Precision
Attachments:
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It can be Rigid or
Resilient.
Distributes the potential
harmful forces away
from the abutment to the
edentulous ridges.
This is useful with free
end saddles.
The Patrix is completely
outside the normal
contour of that retainer.
The Matrix is housed
with in the prosthesis.

Extra coronal Rigid Slide Attachments:
Bi-Nat Attachments
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Height : 4mm.
Application: Bilateral free
end saddles,Removable and
fixed partial dentures.
Activation:There is a
synthetic friction buffer
housed in the patrix , turn the
locking screw to expand the
synthetic friction buffer and
increase the retention.

Extra coronal resilient attachment:

Dalbo-s resilient joint:
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Height : 5mm.

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Application: Bilateral
and unilateral free end
saddles,long denture
saddles.

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Activation:Bend
lamellae of the matrix
towards the center with
an instrument. www.indiandentalacademy.com

PR Hinge Attachments:
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Height : 4.5mm.

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Application: Bilateral
and unilateral free end
saddles.

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Activation:To increase
retention ,screw in the
locking screw which is
housed in the matrix.

Intra Coronal Precision Attachment
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Here the matrix is contained with in the
contour of the crown.
It is useful during the preparation to have
either the attachment or plastic dummy to help
ensure that sufficient space is provided.
There are two groups of intra coronal
attachments, non adjustable and adjustable.


Non adjustable intra coronal Attachments:
Rod and tube attachments
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Application:Fixed partial
dentures with a minor alignment
problem of the abutments.
Used as a connector for dentures
and to support one end of the
removable partial denture which
is retained at the other end by an
adjustable retentive attachment.


Key and Keyway Laboratory made
attachment:
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Application: used to
correct minor alignment
problems in fixed partial
dentures and in fixed
and semi fixed dentures
when minor and major
retainers are used.


Adjustable Intra Coronal Attachments:
Ancra Attachments
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Application : Removable
fixed partial dentures,Cross
arch stabilization,partial
dentures and minor
alignment problems with
posterior abutment teeth.

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Activation: Expand the slot
with a suitable instrument.

Anchors
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These attachments are used on either roots or
implants to retain overdentures or removable
partial dentures.
The patrix is soldered to the diaphragm of a
cast post and the matrix contained in the
denture.
There are two basic types-Rigid and Resilient.
Rigid attachments are used in bounded
unilateral or bilateral saddle cases.
Resilient attachments are used in bilateral free
end saddle cases.

Rigid Anchors:
eccentric rothermann attachment
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Height: 1.1 mm
Application: to retain
rigid hybrid dentures.
Activation: bend the
clasp arms of the matrix
towards the centre.


Resilient Anchors
compact anchors:
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Height: 2.85mm
Application: To retain
over dentures.
Activation: bend the
lamellae of the matrix
towards the centre.


Bar Attachments
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The bar being in the patrix is attached to the
retainers while the matrix sleeve or clips or
riders are processed into the dentures.
They are used to retain overdentures or
removable partial dentures.
They can also be used in conjunction with
crowns and implants.
They are either commercially or laboratory
manufactured.
Bars can be Resilient or Rigid.

Rigid Bars
Rigid Dolder bar:
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Height: 3.5mm

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Application:
partial, hybrid and
implant dentures.

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Activation: Bend both
sides of the sleeve
towards the centre with
an activating tool.

Resilient bar:
Ackermann Bar and Clip:
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There are two types of
Ackerman bar:

1] round
2] egg shaped
The round bar is most frequently
used as it can be bend more
easily to follow the contour of
the ridge and arch.

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Applications: Partial dentures,over dentures
and implant dentures.

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Activation: Bend both sides of the clip towards
center with an instrument.


Auxiliary Attachments
This group of attachments covers a wide range
of applications.
 They serve these situations ;
a.] Allows planning which will enable the
clinician to remove the prostheses for repair or
conversion.
b.] Overcome alignment problems which arise
when abutments converge, making it
impossible to prepare them so that they can be
mutually withdrawn when constructing fixed
partial dentures.
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c.] Replace the loss of soft tissue in anterior
fixed partial dentures. Supplements retention
on bars and telescopic crowns.


Presso -Matic:
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Application: To supplement
the retention on milled
laboratory- made bars and
telescopic crowns used to
retain removable partial
dentures and over dentures.

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Activation:Replace the plastic
cushion and plunger.

Screw and Tube Attachments:
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Applications : To overcome
minor and major withdrawal
problems where abutments
cannot be paralleled and to
provide contingency planning
for long span fixed partial
dentures and full arch
restorations when used in
conjunction with inner thimble
crowns.

Materials used in attachment
fabrication
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Platinum
Iridoplatinum
Gold and platinum
Gold and palladium


Treatment planning
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Essential information which must be obtained
for an adequate treatment plan includes:
Medical and dental history
Discussion of patient expectations
Extra oral examination.


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Intraoral examination
Periodontal survey
Occlusal analysis
Radiographs
Study models


Medical and dental history
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It is important to know significant previous
history.
If the patient has already undertaken
restorative work of a complex nature that has
failed, then the reasons for such failure must
be examined.
The ability of the patient to withstand long
clinical procedures should be assessed at this
early stage.

Discussion of patient expectations
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Patient should be encouraged to comment on
the appearance of their existing teeth, and to
discuss their desires for the new ones.
These are always the most difficult to satisfy
and careful counselling may be necessary to
achieve an acceptable compromise.


Extra oral examination
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An appraisal can be made almost before the
patient is seated in the dental chair.
Any asymmetry should be noted.


Intraoral examination
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This must include a meticulous examination of
all soft tissues, shape of the ridges, and the
amount of bone loss.
Where gross bone loss precludes the use of
conventional fixed partial dentures, precision
attachments can often overcome the problem.


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The teeth should be examined for caries, the
extent of
restorations, colour, vitality, angulations, mobi
lity and bony support, tenderness.
Consideration should be given to increase the
length of crown sufficient for the provision of
a fixed partial denture or precision attachment.
A full periodontal survey should be carried
out.

Occlusal analysis
The basic principles of occlusion should be
applied to the analysis of each case. These are ,
 There should be a stable co-ordinated occlusal
contact of the maximum number of teeth in
centric relation.
 Forces ideally be in line with the long axis of
each teeth.


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There should be no non working incline
contacts.
There must be a balance of anterior and
posterior inclines.


Radiographs
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Radiographs are essential for assessing the
suitability of teeth and their supporting
structures for abutments and the retainer of
precision attachments.


The free-end saddle
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These are classified in to
Bilateral free-end saddle
And unilateral free-end saddle
Extracoranal attachments are preferred against
intracoronal attachments.


Bilateral free-end saddle dentures


Unilateral free-end saddles
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Unilateral saddles can be used in an otherwise
intact arch ,or in combination with a bounded
saddle on the opposite side of the arch.


Case


The bounded saddle
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Bounded saddles can arise in either the
anterior or posterior part of the mouth.
They can be found in combination with freeend saddles or with bounded saddles on the
same arch.
These are easier to treat than free-end saddles.


Anterior bounded saddles
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Problems which might arise in this situation
and complicate the provision of conventional
fixed partial dentures could be due to:
Bone loss
Unit spacing
Lack of parallelism of abutment teeth and
preparation.

Bone loss
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Where bone loss has been only slight and a
gum fitted fixed partial denture is acceptable in
appearance, no problem arises.
Small deficiencies can be corrected by adding
pink porcelain between the pontics.


Bone loss
case 1

case 2


Posterior bounded saddles


Case-1


Over dentures
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Anchors or stud attachments:
Are made in rigid form for bounded saddle
situations and in resilient form for free –end
saddles.
They are generally used in conjuction with
posts and diaphragms placed in root canals
following root canal therapy.
Anchors are usually retained by means of
posts with diaphragms.

Bar attachments
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Spaced teeth which are splinted by a bar are mutually
supportive.
Burnout resin patterns are available and custom-made
bars can be milled in the laboratory.
There are two types of bar—round and egg shaped.
One advantage of round bar is that it can be bent in
all directions.
The egg shaped bar has extra rigidity making binding
more difficult.

Case-2


Auxiliary attachments
a wide variety of attachments all in to this
category.these are:
1.screw and tube
2.key and keyway
3.presso-matic or ipsoclip
4.sectional denture
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Key and keyway


Pressomatic or ipsoclip


Sectional dentures


Milling using a precision
parallelometer
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The milling of crowns is
a precise procedure for
creating bracing, ledges
and rests in full or
partial veneer crowns
which serve to retain
conventional removable
partial dentures.


Milling process


The use of precision attachments
with implants
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Use of precision attachments , in conjunction
with the Esthetic cone abutment and the SteriOss PME abutment, to overcome alignment
problems between implants and teeth.


EsthetiCone abutments
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The estheticone abutment has an overall height
of 6.7mm and the abutment collars are either
1, 2 or 3mm in height so that marginal
placement can be varied to give the best
esthetic results.
The interocclusal space must be sufficient to
accommodate the height of the abutment as
well as the superstructure, otherwise it cannot
be used.

Short cantilever fixed partial
dentures and overdentures:
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If short implants are placed in the anterior part
of the mandible in a very shallow curvature, it
is unwise to cantilever more than a single unit
distally as stresses would be transferred to the
screw and fixtures.
The design in the following case allows for a
complete restoration of the mandibular arch.


PME abutments
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The PME abutments
comes in the lengths of
2, 3, 4, 5 or 6mm.
It is made of titanium
alloy and is capable of
as much as 40
misalignment correction
between implants.


Applications are:
1.Fixed-removable full arch reconstructions on
six or more attachments.
2.Overdentures supported on implants attached
to bar on four to six implants.
3.Tissue supported overdentures attached to a
bar on two implants.
4.Fixed-removable partial denture on two or
more implants.
5.Fixed-removable partial denture attached to
natural teeth with precision attachment.

Interlocks
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Interlocks are extremely useful in restorative
dentistry as they allow a degree of both
splinting and retrievability.
They are also relatively inexpensive.
It is necessary to consider the extent and
direction of the added force, the length and
diameter of the implant, the quality of the bone
and the angulation of the implants in that bone.

Conclusion
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The success of prostheses depends on careful
treatment planning and attention to the Prosthodontic
problems. Careful use of precision attachments with
emphasis on
advantages, disadvantages, indications, contraindicati
ons and mode of action is important for the success of
treatment.
The dental surgeon who familiarizes himself with
precision attachments will add new dimension to his
treatment options.

Bibliography
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Precision attachments-a link to successful
restorative treatment---Gareth Jenkins.
Precision attachments in Prosthodontics--preiskel.
Removable Partial Prosthodontics –
Ernest L. Miller & Joseph .E.Grasso.
Essentials of complete denture Prosthodontics
– Sheldon Winkler 2nd edition.

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Theory and Practice of Fixed Prosthodontics- Tylman.
Prosthodontic treatment for edentulous Patients –
-Zarb & Bolender.
Removable Partial Prosthodontics- Mc.Cracken’s.
Removable Partial Prosthodontics- Stewart.

Thank you


Precision attachments1 /certified fixed orthodontic courses by Indian dental academy

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