PRECISION
ATTACHMENTS
CONTENTS
 Introduction
 History
 Definition and synonyms of attachments
 Classification
 Indications / Applications of precision attachments
 Contraindication
 Advantages
 Disadvantages
 Selection of the abutment teeth
 Requirement of the abutment teeth
 Selection of the retainer
 Selection of the attachment
 Intracoronal attachment
•
Precision / Semiprecision attachments
•
Mechanics of retention
 Extracoronal attachment
•
Rigid / Resilient attachment
•
Extracoronal resilient attachment (ERA)
•
O-ring attachment
 Role of attachment as stress breaker : “Broken stress
philosophy”
 Bar attachments
 Stud attachments
 Magnets as attachment
 Auxillary attachments
 Conclusion
INTRODUCTION
• The desire to balance between functional stability
and cosmetic appeal in partial dentures gave rise to
the development of Precision Attachments
• Precision
Attachments have
surrounded by an aura of mystery.
always
been
• The use of Precision Attachments for partial denture
retention is
• A practice builder for the better class of dentistry
• It helps to elevate the general standard of partial denture
prosthetics.
• The
precision attachment is sometimes said to be a
connecting link between fixed and removable partial denture
as it incorporates features common to both types of
construction.
HISTORICAL BACKGROUND
Winder
“Winders design”
Screw joint retention
Parr (1886)
Extracoronal socket attachment
Stair
Telescopic abutment restoration
Ash (1912)
Split bar attachment system
Late 19th century :
Dr.Herman, ES Chayes
“T shaped”
Precision Attachment
(1906)
“H shaped”
Chayes Attachment
(1912)
First attachment to be available in the general market
Precision – quality or state of being precise
Attachment – Mechanical device for the fixation, retention and
stabilization of dental prosthesis.
Pin slot
chayes
Ceka &
dallabona
• Precision Attachment (GPT-8) :
• A retainer consisting of a metal receptacle (matrix)
and a closely fitting part (patrix); the matrix is usually
contained within normal or expanded contours of
the crown on the abutment tooth and the patrix is
attached to a pontic or the removable partial
denture framework.
• An interlocking device, one component of which is
fixed to an abutment or abutments, and the other is
integrated into a removable prosthesis to stabilize
and/or retain it.
Mechanical device – Direct retainer
• They are designed to replace occlusal rest, bracing arm, and
retaining arm of the conventional clasp retained partial denture.
• They function to retain, support and stabilize the removable
partial denture.
SYNONYMS OF ATTACHMENTS
Internal attachments
Frictional attachments
Parallel attachments
Slotted attachments
Key and Key way attachments.
Male attachments
Patrix
Flange
Insert
Key
Fitting part

Female attachments
Matrix
Slot
Crypt
Keyway
Receptacle

CLASSIFICATION OF ATTACHMENTS
Based on method of fabrication and the tolerance of fit
I.
Precision attachment (prefabricated types)
II.
Semiprecision attachment (custom made / laboratory made
types)
Prefabricated wax / plastic / nylon patterns

According to their relationship to the abutment teeth
Intracoronal (Internal attachment) Extracoronal (External attachment)

Based on stiffness of the resulting joint
Rigid attachments
Resilient attachments (Non rigid)
Based on geometric configuration and design of the attachment.
Key and Keyway
Interlocks
Ball and socket
Bar and clip / sleeve
Hinge
Telescopic
Push button
Latch
Screw units
Classification used in literature :
M.C. Mensor (1973)
Classification according to shape, design and primary area of
utilization of attachment.
Coronal
Intracoronal
Extracoronal
Radicular
Telescope studs (pressure
buttons)
Bar attachment
(Bar joints and Bar units)
Accessory
Auxillary
Screw units
Bar connectors
Bolts
Stabilizers
Balances
Interlocks
Gerardo Beccera and others (1987)
Intradental attachments
-
Frictional
-
Magnetic
Extradental attachments
-
Cantilever attachment
-
Bar attachment
ADVANTAGES
Improved esthetics and elevated psychological acceptance
Mechanical advantage
- Direct the forces along the long axis of the teeth / more apically
- Force application closer to the fulcrum of the tooth
Reduces Non axial loading
Decreases Torquing forces
Rotational movement of the abutment
In Distal extension base cases – “Broken stress philosophy”
Reduced stress to the abutment
Stress free rotational/vertical movements
Cross arch load transfer and prosthesis stabilization
Compared to conventional clasp retained partial denture
Less liable to fracture than clasp
Less bulky and more esthetics
Better retention and stability
Less food stagnation
DISADVANTAGES
Complexity of design, procedures for fabrication & clinical
treatment
Minimum occlusogingival abutment height (4-6mm)
To incorporate attachment without overcontouring
Enough length of parallel contact
Anatomy of the tooth – Limited faciolingual tooth width
(incisor and canine areas)
Expensive
Complexity of laboratory and clinical procedure
Attachment maintenance (repair or periodic replacement)
Wearing of attachment components
Require high technical expertise – Dentist and laboratory
technician
Requires aggressive tooth preparation
Cooperation and manual dexterity on the part of the patient
Difficult to insert and remove
Visually or manually challenged patient
Increase demand on oral hygiene performance
INDICATION / APPLICATIONS OF PRECISION
ATTACHMENTS
Removable Prosthodontics
As a retainer in a removable tooth supported partial denture
4 large well rounded abutments are available
For esthetic concern in the anterior part of the mouth
Stress Breakers – Free end saddles/Distal Extension Base cases (DEB)
– When cantilevered pontic is to be used as abutment
For movable joints in sectional dentures
Periodontal involvement of the tooth
Contraindicates rigid FPDs
Most efficient bilateral bracing and support are essential
 Divergent abutment teeth with high survey lines – parallel path
of placement.
 As a retainers in tooth supported over denture
Fixed Prosthodontics
 As a connector in fixed partial denture construction
(long span bridges)
 To overcome alignment problems where abutments have
differing path of withdrawal.
IMPLANT PROSTHODONTICS
Implant supported over denture
They are used for connection between the tooth and the implant
CONTRAINDICATIONS OF PRECISION ATTACHMENTS

Poor periodontal support.

Poor crown to root ratio

Poor oral hygiene habits

Abnormally high carious rate

Inadequate space / room to employ the
attachment

Compromised endodontic and restorative
conditions
SELECTION OF THE ABUTMENT TEETH
Factors :
Condition of abutment teeth
Number of the abutment teeth
Location of the abutment teeth
Periodontal condition
– Crown root ratio
– Periodontal support
Pulpal status
– Vitality of the pulp
– Size of the pulpchamber
REQUIREMENTS FOR THE ABUTMENT TEETH
Axial space requirement
Sufficient clinical crown length – for minimum of 4mm attachment length
Maximum attachment
length 6-7 mm
Minimum attachment length
4mm
Buccolingual space requirement
Inadequate attachment
length < 4mm
Adequate space between the pulp
and the normal contour of the tooth
SELECTION OF THE TYPE OF RETAINER
Full crown retainers
Partial coverage retainers
Intracoronal attachments
Kennedys Cl III partial denture
More retentive / rigid
Splinted abutment teeth
Ideal contours
Most vulnerable
Caries protection
Inadequate retention
Marginal leakage
Inlays / onlays / pin ledges
Not used for intracoronal attachments
Lack of retention
Marginal caries
Less life
Selection of the attachments
Intracoronal
vs
Extracoronal
Resilient
vs
Non resilient
EM attachment gauge (Matsuo (1970)
75 mm in length
Red
 3-4 mm
Yellow  5-6 mm
Black  7-8 mm
EM attachment selector (Dr. MC Mensor (1973)
105 attachments
30 points of information
Quick reference
Communication between the dentist
& laboratory technician
INTRACORONAL ATTACHMENTS
Precision attachment
(prefabricated type)
Semiprecision attachments
(custom made)
Intracoronal precision attachment
(Dr. Herman E.S Chayes)
Conventional attachment
T shaped attachments
Modern attachment
H shaped attachments
Head
Tube
Contact plate
Adjustment slot
Rein forcing
plate
MECHANICS OF RETENTION
Frictional : Preiskel group I
Retention – Surface area contact
Function of the length – Controlled by height of clinical crown
– Intermaxillary space available
Function of cross sectional dimensions
Mechanical : Preiskel group II
Auxillary mechanical retentive features
Ex. Spring loaded plunger / clips
DEPENDING ON ARTICULAR RETENTION
Passive attachment
Active attachment
Locked precision attachment
Passive Attachment :
Matrix : Simple channels closes at one end to provide stop
Patrix : Solid slide
Channels of passive attachment may be round / elliptical slides
Omega
Beyeler
ACTIVE ATTACHMENT
Active friction grip attachment
McCollum
Crismani
Active snap grip attachments
Crismani
Locked precision attachment
Attachments bolted by means of a sliding bolt or latch
Pinned or screwed together
Latch retained
Mc Collum attachment :
H shaped attachment
Single adjustment slot
Retention  expanding the adjustment slot
Stern attachment
Two adjustment slots
Stern Gold latch retained
Crismani attachment :
Available as
Rigid / Resilient
Rigid crismani attachment
Frictional grip
Mechanical  Spring clip
Ney’s attachment :
Conventional
H shaped
Ney loc split
lingual
Latch retained
Bakers attachment
Schatzmann attachment
Frictional retention
Mechanical retention
(spring loaded plunger & coil spring)
Semiprecision attachments
Semiprecision rest – intracoronal rest seat and resilient lingual arm.
“Laboratory fabricated rigid metalic extension (patrix) of a fixed or
removable dental prosthesis that fits into a slot type key way (matrix)
in a cast restoration allowing some movement between the
component”.
- GPT8
Gillete (1923) : The first semiprecision attachment
Rectangular deep rest with buccal and lingual wrought clasps arms
Ira D Zinner (1979)
Locking semiprecision
attachment
Non locking semiprecision
attachment
Louis blatter fein (1969) : Four aspects of rest seat preparation
Occlusal form / outline form – controls amount of rotation
Circular
Dove tail
Rectangular
Mortice
(Rigid – locking type)
Resilient
Some resiliency
(Non-locking type)
Proximal form / side walls – lateral force control
Parallel outline
Tapering outline
The angle of the proximal wall with the gingival floor
Gingival floor form : serves the function of reciprocation
Added
reciprocation
Flat
Inclined
Channeled
Mortice occlusal
form
Rectangular
occlusal form
Locking Semiprecision Attachments
Neurohr – Williams No. 1 (Mortice rest)
Ney‟s MS Intracoronal attachment (circular rest)
Advantages :
Versatility for clinical situations – employing various rest seat
outline forms.
Variation in tooth size and shapes are easily accommodated.
Better crown contour compared to prefabricated type
Disadvantages :
Long term wear is more – softness of alloy used.
No standardization of sizing : Lack of interchangiability of
male and female attachment.
Greater degree of laboratory skill and attention in detail.
EXTRACORONAL ATTACHMENTS
Introduced by Henry R. Boos (1900)
Modified by F Ewing Roach (1908)
Application
Kennedy‟s class I and class II
Boitel (1978)
 Rigid attachments
 Resilient attachments
 Bar attachments
EXTRACORONAL ATTACHMENT
Rigid attachments
Hinged attachments
(Stress breaking action)
Resilient
attachments
ERA
O-ring
Advantages :
• No alteration of contour of the abutment crown
• Can be used in short abutment teeth
• Greater freedom in the design
• Ease of insertion and removal
Disadvantages (Wolf RE 1980) :
Lack of occlusal satability
Bulky
Rebasing problems
Improper control of force distribution
Encroachment on the gingival papilla – use of mini attachment
RIGID EXTRACORONAL ATTACHMENTS
Roach attachment (ball and tube attachment)
Oldest attachment
Patrix – round ball
Matrix - tube
Pin and tube attachment
The simplest
Patrix - pin
Matrix – tube
Stabilex attachment
Two retention pins
Disadvantage is increased length
Patrix
Conex attachment
Matrix
Assembled
(Smaller version)
Two types pins
Frictional retention
Mechanical locking
RESILIENT EXTRA CORONAL ATTACHMENT
•Dalbo / Dallabona attachment
a) Patrix
b) Matrix
Assembled
Dalbo stress breaker
Rotational
Matrix and patrix
and Vertical movement
Ceka attachment
Developed by karl cluytens (1951)
Two types
- Ceka NV attachment
- Ceka revax
Matrix  metal ring retainer
Patrix  Attachment pin
(split metal post)
Functional aspect : Mark E, Waltz 1973
A) Support
B) Bracing
C) Retention
• Insertion and removal
• Reduces frictional wear
Attachment pin / split post
Ceka Revax
ROLE OF ATTACHMENTS AS STRESS BREAKER
Broken stress philosophy
Rigid system
Non-rigid system
Stress breaker
Mensor  stress can only be selected, altered or blocked
“Stress director”
Shohet (1969) Kratochvil (1981)
Low intensity forces on abutment teeth in contrast to rigid
attachments.
Rationale of stress breaker  movement should be strictly only
to displaceable tissue
Disadvantages of stress director :
More complex, increased wear and breakage
Increased bone resorption and trauma
Occlusal contacts difficult to maintain
Spring like device  tendency to fatigue
STRESS BREAKER DESIGNS
ASC-52
attachment
Extracoronal resilient attachment
Patrix and Matrix
Crismani resilient
attachment
“Hinge stress breaker”
Neys distal extension
stress breaker
Stern stress breaker
Anchorvis attachment
Extracoronal resilient attachment (ERA) :
(ERA)
Colour coded retention caps
Most flexible
White > Orange > Blue > Gray
Most rigid
Two types of ERA
Standard
Reduce vertical (ERA – RV) – male part is 0.5mm shorter
Use of ERA in
DEB cases
Matrix
Patrix
 Vertical resiliency of 0.4mm
 Universal joint hinge action
Use in over denture
Yen Chen Ku et al (2000) : ERA provides esthetics, vertical
resiliency, easy replacement of worn dentures
O-SO ring / O-ring attachment
Patrix - post with the groove
or undercut.
Matrix – O-ring synthetic
polymer gaskets + encapsulator
O-ring are made up of
Silicone
Nitrile
Fluorocarbon
Ethylene propylene
Advantages of O-ring
Ease in changing the attachment
Wide range of movement
Low cost
Different degrees of retention
Elimination of the time / cost of the superstructure
STUD ATTACHMENTS (ANCHORS)
“Anchor the roots”
Simplest of all the attachment
Partrix – dowel / post retained restoration
Matrix – denture base of the prosthesis
Classified as :
 Rigid stud unit
 Resilient stud unit
 Extraradicular units
 Intraradicular units
Extraradicular Intraradicular
Space requirement of these attachment
is intermediate between dome shaped
coping and thimble shaped coping.
These should be placed parallel to the
long axis of the tooth.
DALBO STUD ATTACHMENT
Rigid unit
Nylon ring – protects the lamella
Ball and socket unit
  Retention – altering the positions
of free ends of the lamella
(Vertical and
rotational movement)
ROTHERMAN ECCENTRIC ATTACHMENT
Button shaped attachment
Patrix – eccentric cylinder
with undercut or groove
Matrix – Clip or clasp arm
Activation : Bending the
clasp arm towards center
Rigid units
Resilient unit
ZEST ANCHOR ATTACHMENT
Polyethylene – Nylon stud
Patrix
Funnel shaped tube
Matrix
Advantages :
Reduce
vertical
space requirement
Instrumentation kit
Loads are transferred
more apically.
GERBER ATTACHMENT
Largest of the stud unit
Resilient – spring controlled
vertical plane
Patrix – threaded post
Matrix – retention spring and ring
Resilient gerber
Rigid gerber
Disadvantages :
Complex attachment system
Requires more space
Permits little rotation
CEKA ATTACHMENT
Patrix – metal ring
Matrix – attachment pin
(split metal post)
Ceka revax
Extra radicular
Intra radicular
SPACER RING
Vertical movement of the
prosthesis
SCHUBIGER ATTACHMENT
Patrix : threaded post / screw
Matrix : recessed collar, cap nut / lock nut
Cut section
BAR ATTACHMENTS
Gilmore clip system (1913) - metal bar with retaining sleeve / clip.
Bar can be attached to the :
Coping or crowns over the vital teeth
Post coping on endodontically treated teeth
Screwed down into the coping (implant system)
Types of bar attachments :
Customised bar
Dolder bar
Ackermann’s bar
CM rider bar
Hader bar
Andrews bar
Two groups of bar attachments :
1) Bar units - rigid
2) Bar joints – permits rotation
BAR JOINTS
Single sleeve bar joints
Multiple sleeve bar joints
Depending on cross section
Round / circular
Oval / egg shaped
„U‟ shaped /
parallel sided bars
DOLDER BAR
Egg shaped bar in cross section
Open sided sleeve
Two sizes 3.5mm x 1.6mm,
3.0mm x 2.2mm
Spacer – degree of movement
MOVEMENTS SEEN IN DOLDER BAR
Rest position
Vertical translation
Implant supported over denture
Sagittal rotation
ACKERMANN BAR
Available in different cross
section
Circular cross section – can
be bent in all planes
CM BAR
 Made up of precious /
semiprecious alloy
 Retention tags in long axis
of the bar
HADERBAR
Helmut Hader in 1960
Available as a prefabricated plastic pattern
Notable feature
 Resin / plastic sleeve
 No spacer- more
support
English, Donnel & Staubli (1992)
Hader EDS system
System with 3mm height (8.3mm).
Clips with metal encapsulator
Advantage
 Prefabricated plastic pattern – no need for soldering.
 Precise fit, simplicity, versatility
Advantages of bar attachments :
Rigidly splint the teeth
Provides good retention, stability and support
Provides cross arch stabilization
Positioned close to the alveolar bone (exhibit less leverage)
Disadvantages :
Bulk of bar
Plaque accumulation
Wearing
Soldering procedure
Manual dexterity
MAGNETS AS ATTACHMENT
Since 1950
To retain maxillofacial prosthesis
Alu, Ni, Iron,Cobalt alloy (alnico)
Limited use – larger size
1960 “use of rare earth element” – High field strength
– Can be used in smaller size.
Somarium cobalt (Sm-Co) (Joseph Becker Hoffer 1967)
Neodymium iron boron (Nd-Fe-B) – 20% stronger
Somarium iron nitride – High magnetization
Used for retention of mandibular overdentures (tooth and implant
supported over dentures)
Gilling’s magnetic attachment
(cobalt somarium alloy magnets)
“Split pole paired magnets”
Closed field magnetic system
Magnetic retainer with magnets
Magnetic keeper
Jackson magnetic attachment
(cobalt somarium alloy magnets)
Cemented in keeper
Screwed in keeper
SANDWICH DESIGN
Encapsulated magnetic retainer
and magnetic keeper
Assembled attachment
Attractive breaking force  4.9 N (500 gm)
Advantages of magnetic attachment :
Smaller size and strong attractive force
Produce constant force – constant retention
Easy to incorporate into the prosthesis
Automatic reseating
Boon for elderly patients (Parkinsonism, arthritic patient)
Less lateral force to the abutment tooth
Disadvantages :
Loss of retention due to corrosion or heat instability
Requires encapsulation within inert alloys
Cant be repaired
High cost
Short track records
Limited force transmission - Magnets can slide on their keepers.
AUXILLARY ATTACHMENTS
 Screw and tube attachment
 Key and keyway / interlocks
 Presso Matic or Isoclip
 Bar connectors
 Attachments for sectional dentures / bolts
Screw and tube attachment
Indications :
To overcome alignment problems
Connecting one restoration of fixed partial denture to another
Allowing the removal of long span fixed partial denture for
repair and examination of abutment.
ATTACHMENT USED FOR SECTIONAL DENTURES
Two part dentures : One part - chrome cobalt base
Second part - removable acrylic flange with teeth
Advantage of superior esthetics and improved retention
Method of union :
Physical interference : Bolt retained prosthesis
Frictional resistance : Split post retained prosthesis
SECTIONAL DESIGNS
Individual sections / separate sections : uses mesial and distal
surface of the abutment teeth as guiding planes.
Bolt retain two parts prosthesis
Hinged sections : Buccal and lingual path of insertion
CONCLUSION