Precision attachment

ASWATI SOMAN
PG RESIDENT
PCDS
Prabhakar B. Angadi, Meena Aras, Cecil Williams, Suresh Nagaral
Journal of Evolution of Medical and Dental Sciences/Volume 1/Issue 6/December-
2012
1

• The precision attachment is sometimes called as a
connecting link between fixed and removable partial
dentures as it incorporates features common to both
types of construction.
• An attachment is defined as “A mechanical device for the
fixation, retention, and stabilization of prosthesis”.
• Precision attachments are two precocious metal
components which are manufactured to form an
articulate joint.
• Precision attachments can be made out of precious metal
alloys, titanium, chromium-nickel, chrome-cobalt and
Stellite.
2

• First component or matrix is a receptacle or keyway,
which is positioned within the normal clinical contours of
a cast restoration or attached to the abutment
• The second component of patrix is attached to the
removable partial denture.
• When the removable partial denture is placed in the
patient’s mouth, the two components interlock in a sliding
joint configuration. This sliding joint resides within the
normal clinical contours of an abutment and functions to
retain, support, and stabilize the removable partial
denture
• The matrices can be made out of metal or plastic.
• Plastic matrices can be made of poly-oxy-methylene
(POM) or poly-ether-ether-ketone (PEEK).
3

• Internal attachments
• Frictional attachments
• Slotted attachments
• Parallel attachments
• Key and keyway attachments
4
Patrix
Flange
Insert
Key
Fitting part
Matrix
Slot
Crypt
Keyway
Receptac
le
MALE COMPONENT FEMALE COMPONENT

• Long-span replacements
• As stress breaker in Free-end saddles
• Periodontal involvement that contraindicates fixed partial
dentures
• Situations which require maximum esthetics
• Movable joints in fixed movable bridge work
• As contingency devices for the extension or conversion
of existing fixed appliances.
• Sections of a fixed prosthesis may be connected with
intra coronal attachments
5

• Teeth with short clinical crowns (this can be overcome
with periodontal surgery).
• Teeth that are narrow faciolingually.
• Teeth that have extremely large pulps (young people).
• Any patient who has a contraindication for a partial
denture (health, non co-operative).
• Patient’s lack of dexterity or ability to use the hands.
• Severe periodontitis
• In high caries index patients
6

1) Improved esthetics and elevated psychological
acceptance of the prosthesis → conventional clasp
assemblies and rests may be visible and unaesthetic.
• Clasp arm direct retainers placed on canine and
pre- molar abutments may be esthetically objectionable,
and appropriate use of attachments may eliminate the
need for facial clasp arm and improving esthetics.
7

• Compared to conventional clasp retained partial
denture, they give better retention and stability,
less liable to fracture than clasp, less bulk, and
reduced incidence of secondary caries.
• Precision attachments provide better vertical
support and better stimulation to the underlying
tissue through intermittent vertical massage.
8

2) Lateral forces in the abutment during the insertion
and removal are eliminated, and more axial force
during functions is achieved as force application is
more close to the fulcrum of the tooth than in case
of occlusal rest or incisal rest ; therefore,
decreased lever arm reduces non-axial loading
and decreases torquing forces and rotational
movement of the abutment.
9
When compared to occlusal rests, the
apical extension of an intracoronal
attachment reduces non- axial loading and
diminishes rotational movement of the
abutment during occlusal loading (L arrow).

• In case of distal extension base, removable partial
denture prosthesis attachment positioned between the
abutment and extension bases incorporates broken
stress philosophy that limits the potentially damaging
forces (stress transfer) imparted to the abutment as these
attachments permit vertical, horizontal/rotational
movement of the denture bases during function relative
to the abutment.
10

• Stress equalization approach to partial denture design
emphasize that the vertical displaceability of a natural
tooth is not as great as that of the soft tissues covering
the edentulous ridge.
• Advocates of this school believe that forces applied to a
removable partial denture are transmitted to the
abutments. As a result, proponents believe that rigid
connections between denture bases and direct retainers
are damaging, and that stress directors are essential to
protect the abutments
11

3) Cross arch load transfer/force transmission and
prosthesis stabilization may also be improved with
attachments particularly when rigid precision
attachments are used.
12

• Complexity of design, complex principles, and
procedures for fabrication and clinical treatment.
• Expensive increased overall cost of the treatment.
• Requires high technical expertise for successful
fabrication experience and knowledge on the part of
dentist and laboratory technician are essential.
• Increased demand on oral hygiene performance.
13

• The tooth may have to be extensively prepared to
provide required space to accommodate
intracoronal attachment.
• The attachment is subjected to wear as a result of
friction between metal parts; as wear occurs, male
portion fits more loosely, thus permitting excessive
movement leading injury to abutment teeth.
14

• The extra coronal type of retainer extends out from
the tooth near the gingival border, so there may be
gingival irritation followed by usual inflammatory
sequel.
• The extracoronal type of attachment must occupy
the space immediately adjacent to abutment tooth,
which is precisely where a replacement tooth
should ideally be positioned.
15

• While prefabricated attachments are called as precision
attachments, those fabricated in laboratory are called as
semiprecision attachments.
• Precision attachment is made of precious metal and fit of
two working elements is machined to very close
tolerances, hence is more precise than laboratory
fabricated attachment.
• Semiprecision attachments are usually fabricated in base
metal alloys.
• The semiprecision attachment is also called as precision
rest, milled rest or the internal rest.
16

• Based on their method of fabrication and the tolerance of
fit between the components
a. Precision attachment
b. Semi precision attachment
17

• According to their relationship to the abutment teeth
a. Intracoronal/internal attachment
18

a. Extracoronal/external attachment
19

a. Radicular/intraradicular stud type attachments
b. Bar Type
20

• Based on function or movement
a. Solid/rigid
• Subclassified into a two types: Non-lockable and
lockable
b) Resilient:
• Based on modes of retention
a. Frictional
b. Mechanical
c. Frictional and Mechanical
d. Magnetic
e. Suction types
21

• Depending on the geometric configuration and design of
the attachment system.
a. Key and keyway.
b. Ball and socket.
c. Bar and clip or bar and sleeve.
d. Telescope.
e. Hinge.
f. Push button.
g. Latch.
h. Screw units.
i. Interlock.
22

• 1. MC Mensor (1973): An attachment classification
according to shape, design, and primary area of
utilization of attachment [
23

Gerardo Beccera and others (1987)
a. Intradental attachment
 Frictional
 Magnetic
b. Extradental attachments.
 Cantilever attachment.
 Bar attachment.
Good kind and Baker (1976)
a. Intracoronal
• Resilient
• Non-resilient.
b. Extracoronal
• Resilient
• Non-resilient.
24

25
REQUIREMENTS FOR THE ABUTMENT TEETH
Axial space requirement
Adequate space between the pulp and th
normal contour of the tooth
Sufficient clinical crown length – for minimum of 4mm attachment
length
Minimum attachment length
4mm
Inadequate attachment
length < 4mm Maximum
attachment length 6-7 mm
Buccolingual space requirement

• The two parts of an intracoronal attachment consist of a
flange and a slot.
• The flange is joined to one section of the prosthesis and
the slot unit embedded in a restoration forming part of
another section of the prosthesis.
26

Two types of intracoronal attachments are
available
• a. Those whose retention is entirely frictional
E.g. McCollum intra coronal unit.
• b. Those whose retention is augmented by a
mechanical lock.
E.g. Schatzmann unit Additional retention is
provided by a spring loaded plunger.
27

Depending on the cross sections intra coronal
attachments can be classified into
1. H-Shaped flanges - The external frictional flange
of H-Shaped unit strengthens the attachment,
without increasing the size of the female part.
2. T-shaped flanges E.g. Chayes attachment
3. Attachments with a circular cross section. They
are suitable only for joining two sections of a fixed
prosthesis.
28

• The friction fit intracoronal attachments with adjustment
potential are:
a) Chayes
b) Crismani attachments
c) McCollum unit
d) Ancra attachment.
e) T-Geschiebe 123
30

• Auxiliary retentive features are incorporated in some
attachments in an effort to provide more retention for a
given frictional area although no extra stability is
provided.
• A minimum of 4 mm vertical space is necessary.
• E.g.: Crismani units, Stern gingival latch attachment and
Micro
31

• Lack of adjustment potential renders this type of unit
unsuitable for removable prosthesis, as repeated
insertion and removal will cause the attachment to wear.
• They are useful for joining a series of crowns without a
common path of insertion.
• Round profiles are useful when anterior teeth are
concerned.
• E.g.: Beyler.
32

1)Retainers: Intra coronal attachments are effective and
almost invisible retainer for bilateral and unilateral
prostheses.
2)Connectors: Sections of a fixed prosthesis may be joined
with intracoronal attachments. This possibility can be
useful where;
33

a. Prostheses do not share a common path of insertion
yet can be connected rigidly in the mouth.
b. The operator prefers to limit the length of individual
castings while making a large span fixed prosthesis.
c. The prognosis of a distal abutment is dubious.
Connecting the posterior segment with an attachment
allows subsequent removal without damage to the main
restoration. The attachment slot can be used for later
construction of an attachment retained denture
34

• These attachments have part or all of their mechanism
outside the crown of a tooth.
• Many of these units allow a certain amount of movement
between the two sections of the prosthesis.
• Their main application is for distal extension prosthesis.
• They may be used to retain restorations for bounded
spaces.
35

Extracoronal attachments can be subdivided into following
groups.
a. Projection units : The units are attached to the proximal
surface of a crown. These groups can be divided in turn
into;
1. Those that provide a rigid connection.
Eg. Conex attachment
2. Those that allow play between the components.
Eg. Dalbo extracoronal projection unit, Ceka system with
retaining ring.
b. Connectors :These units connect two sections of a
removable prosthesis and allow a certain degree of
play. 36

38
CEKA REVAX ATTACHMENT ROACH
ATTACHMENT
PIN TUBE ATTACHMENT

• These attachments are so called because of the shape of
the male units that are usually soldered to the diaphragm
of a post crown.
• Ball attachments are the most commonly used type of
attachments for non-splinted implants.
• They are very easy to install and can be used to stabilize
a pre-existing denture, keeping the prosthetic costs
lower .
• The advantages of ball attachments include their small
size, allowing more space for the acrylic, and in turn
increasing the strength of the denture.
• In case of limited vertical dimensions, their use can be
impaired, producing discomfort for the patient
39

• Few stud attachments are entirely rigid, since their size
makes it difficult to prevent a small amount of movement
between the two components.
• In some attachments springs or other devices are
specifically incorporated to allow a controlled degree of
movement.
• Dalbo, Conod’s unit, Rothermann unit, Baer and Fah
units are few examples of stud attachments.
40

• Ball attachments are able to prevent horizontal
movement of the denture on the mucosa, but it is not
possible to prevent the vertical axial movement of the
balls in the matrix.
• Ball attachments are available with different angulations,
giving the clinician the possibility of using them in cases
of divergent implants up to 10 degrees
41

42
ZEST ANCHOR
ATTACHMENT
DALBO ATTACHMENT

• Bar attachments consist of a bar spanning an edentulous
area joining together teeth or roots.
• The denture fits over the bar and is connected to it with
one or more sleeves.
• Bar attachments are of 2 categories.
1) Bar joints
2) Bar units
43

• These units allow play between denture and bar.
• The bar is usually attached to diaphragms on root filled
teeth, locking the roots together and improving the crown
/ root ratio.
• A common path of insertion for the retaining posts is
desirable although divergence can be overcome by
mechanical means.
• Alternatively the abutment teeth can be crowned and
these crowns connected by the bar.
44

Single sleeve bar joints
• The Dolder bar joint is an excellent example of this
attachment.
• This well tried bar is produced from wrought wire, pear
shaped in cross section and running just in contact with
the oral mucosa between the abutments.
• An open sided sleeve is built into the impression
surface of the denture and engages the bar when the
denture is inserted.
45

Multiple sleeve joints
• If several short sleeves are substituted for the continuous
one, there is no need for the bar to run straight and it can
be bent to follow the vertical contours as well as the
antero-posterior curvature of the ridge.
• Gilmore, Ackerman, Hader are few commonly used bar
joints.
• Multiple sleeve bar joints are more versatile than the
single sleeve units, but the bars seem to have slightly
less rigidity.
46

• Bar units
• Bar units are comparatively rigid allowing no movement
between the sleeve and bar.
• Although some load may be distributed to the mucosa
these prostheses are mainly tooth borne.
• Bar units may be useful where;
1. There are 4 or more abutment teeth and large
edentulous spaces.
2. The number and distribution of the teeth does not allow
construction of a satisfactory clasp retained partial
denture.
3. There are edentulous areas with considerable
resorption.
4. Rigid splinting is required for remaining teeth or roots.
48

Advantage
• Bar units provide excellent retention and stability for a
denture while rigidly splinting the abutments.
• Artificial mucosa can be provided by the denture flange
• The removable section can be rebased or repaired like
clasp retained prosthesis.
Disadvantage
• Drawbacks are that the bar provides a medium for
accumulation of plaque and the patient must maintain a
good standard of hygiene.
• Other contra indications are patients with poor manual
skills and those with limited vertical or bucco lingual
space.
49

M.P. CHANNEL SYSTEM:
• These MP channels are extremely slim and save the
operator and technician the problems and expense of
milling.
• Additional retention between the two sections of the unit
can be provided by incorporating a plunger in the sleeve.
• Guiding flanges should be incorporated to prevent
rotation around the plunger and to obtain maximum
retention.
51

• MECHANISM OF ACTION:
• Retainers must hold the prosthesis securely in place
during chewing, swallowing, speaking and other oral
functions.
• Therefore, male and female portions must fit together
precisely.
• Resistance to separation within the attachment is by
following mechanisms.
i) Friction
ii) Binding
iii) Wedging of conical bodies
iv) Internal spring loading
v) Active Retention 52

• Occurs when parallel walls of closely fitting bodies pass
over one another.
• Friction occurs between contacting parallel walled
bodies.
• 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.
53

Binding:-
• Occurs when a parallel walled body tips within its
receptor site. Eccentric loads on frictional elements
produce tipping movement, which create an additional
binding effect significantly increasing resistance to
withdrawal.
Wedging of conical bodies:-
• Friction comes into play only in the terminal position and
is lost as soon as the bodies begin to separate.
54

Internal spring loading-:
• as produced by a clip within a cylinder. The friction within
retainers is often increased by loading with internal spring
clips. A slot in the male portion allows the pressure to be
adjusted.
55

Active Retention:-
• 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.
• Active retention by means of a bulge at the end of a
resilient slotted post.
• Active retention from ring spacing.
56

ATTACHMENT SELECTION:
• In 1971, 126 attachments were listed and classified by
Dr. Merrill Mensor;
• This is called as E. M. attachment selector
• It has 5 charts giving specification as to
• type, vertical dimension (Minimal and Maximal), whether
it is for anterior and posterior teeth, whether the
assembly is simple or complex, whether the function is
rigid or resilient, type of resilience, size of movement and
type of retention.
• It shows if the attachment is interchangeable or
replaceable and finally what type of alloy and material it
is made of.
57

• E.M. attachment selector system utilizes a colour coded
millimeter attachment gauge to define the vertical
clearance available in the edentulous regions of occluded
casts for attachment selection.
• The gauge is made of plastic and measuring 75 mm in
length.
• It is graduated from 3 to 8 mm in 1 mm increments with a
corresponding colour code.
• Red designates 3 to 4 mm, yellow designates 5 to 6 mm
and black designates 7 to 8 mm.
58

• The gauge is placed between the occluded casts
adjacent to a tooth that will carry an attachment.
• The measurement is thus read numerically and according
to colour.
• The vertical limits measured by the EM gauge are the
common area of concern for all connector systems.
• The available space will govern the type of attachment
system that can be used.
• A closed vertical space will narrow the selection of
available or recommended attachments.
• Where vertical intermaxillary space is abundant, the
choice of attachment systems is less restricting.
60

In selecting an attachment system;
i) The first decision that must be made is whether to use
an intracoronal or extracoronal attachment
ii) ii) The second decision to be made is whether to use a
resilient or a nonresilient type
iii) iii) The third consideration is that the largest attachment
can be used within the given space should be chosen
to gain maximum stability, retention and strength for the
prosthesis.
61

• The precision attachment in combination with other
aspect of advanced partial denture construction offers us
the possibility of making prosthesis that are esthetic,
retentive, strong and problem free and that are
undetectable by and will not compromise the oral health
of the our patients.
• The clinician who familiarize himself with precision
attachments will add a new dimension to his treatment
options and this will also broaden his referral base.
62

• Advanced removable partial dentures. James S. Brudvick quint int. Pub pg.
115-152.
• Stewart’s-clinical-removable-partial-prosthodontics-4th-edition
• Attachments in prosthodontics: different systems of classification: a review
h. M. Khuthija khanam, M. Bharathi, K. Rajeev kumar reddy, S. V. Giridhar
reddy4
• Precision attachments: A review to guide clinicians precyzyjne elementy
retencyjne – przegląd piśmiennictwa
• Precision attachment- an overveiw dr. K sounder raj, dr. Kalavathi, M., dr.
Manisha minz, dr. Divya chandra, S. And dr. Moh. Ajmal, B.
• Precision attachments- an overview Reeta jain1, swati aggarwal
• Precision attachments; applications and limitations prabhakar b. Angadi,
meena aras, cecil williams, suresh nagaral
• An insight into various attachments used in prosthodontics: A review Dr.
Hema kanathila, dr. Mallikarjun H doddamani and dr. Ashwin pangi
• Precision attachments in prosthodontics: A review arti, ajay gupta, gagan
khanna, mohit bhatnagar, giby M markose, satvik singh
63

Precision attachment

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