Precision and SemiPrecision
Attachments
Where? When? Why?
George E. Bambara, MS, DMD
FACD, FICD
Objectives of the Program
• Understanding how attachments
preserve hard and soft tissue
• Selection of the appropriate
attachments
• Understand the uses of attachments
• Familarization with different
attachments
• Maintenance and hygiene
Properly Designed Clasps
Work
?????? Concerns ??????
•Uneven distribution of
forces
•Possible orthodontic
movement
•Periodontal compression
Removable Partial Dentures
Periodontal Status
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RPD’s WERE ASSOCIATED WITH
Increased periodontal pathology
Increased plaque and tarter
accumulation
Increased gingival inflammation
Increased probing depths
Increased recession
Increased abutment tooth mobility
Zlataric’ et.al., The Effect of Removable Partial Dentures on Periodontal Health
of Abutment and Non-Abutment Teeth. JPeriodontology, 2002, 73: 137-144
Clasps vs. Attachments
CLASPS:
• Less expensive.
• 5 to 6 year life.
• 30% loss of retention.
• Poor chewing
efficiency.
• 93% caries rate.
• 50% compliance.
ATTACHMENTS:
• 15 year + life.
• More expensive.
• 99% retention.
• Excellent chewing
efficiency.
• 8% caries rate.
• 100% compliance.
Rantanen, Wetherall and Smales, Feinberg et.al.
CLASS I LEVER
Class II Lever
CLASS III LEVER
Class III Lever
Indications for Attachments
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Aesthetics
Redistribution of forces
Minimize trauma to soft tissue
Control of loading and rotational
forces
• Non parallel abutmentsSegmenting
• Future salvage efforts- Segmenting
• Retention
Functional Classifications
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Class 1A- Solid, rigid, non-resilient
Class 1B- Solid, rigid- lockable
Class 2- Vertical resilient
Class 3- Hinge resilient
Class 4- Vertical and hinge resilient
Class 5- Rotational and vertical
resilient
• Class 6- Universal, omni-planer
Patient Dexterity and
Attachment Wear
• Insertion and removal cause wear
• Poor dexterity
• Avoid multiple attachments with
complex a complex path of insertion
• Use lingual “guiding arms”
What is a Precision
Attachment?
• An attachment that is fabricated from
milled alloys
• Tolerances are within .01mm
Precision Attachments
They are Generally
• Intracoronal
• Rigid = NonResilient
Benefits of Precision
Attachments
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Consistent quality
Controlled wear
Less wear
Easier repair
Standard parts are interchangeable
What is a Semi-Precision
Attachment?
• An attachment that is fabricated by
the direct casting of plastic, wax,
metal, or refractory patterns
• Their method of fabrication subjects
them to inconsistencies
Benefits of Semi-Precision
Attachments
• Less costly
• Easy fabrication
• May be cast in alloy
Semi-Precision Attachments
They Are Generally
• Extracoronal
• Non-rigid = Resilient
Resilient Attachments
• 0.1mm – 0.4 mm difference in the
displacement of the tissue and the
denture base, as opposed to the axial
intrusion of the abutment teeth
• Directs forces to the supporting tissues
and the abutment teeth
Selection of Attachments
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Location
Opposing arch
Function
Retention
Available space ( 3-5mm )
Cost
Criteria Selection for Resilient
and Non Resilient
Attachments
• Do not oppose two resilient attachments
unless teeth are very weak
• Opposing distal extensions with strong
abutments: upper - non resilient, lower
- resilient
• Lower distal extension vs.
– Natural dentition - resilient
– Full denture - non resilient
Coronal Attachments
INTRACORONAL:
EXTRACORONAL
• Placed within the
contours of the crown
form
• Needs more tooth
reduction
• Rigid connectors
• Placed outside the
contours of the crown
form
• Needs less tooth
reduction
• Stress redirectors and
are considered
resilient
Stud Attachments
A ball and socket type of attachment in
which one component is attached to an
abutment or implant, and the other
element is retained in the prosthesis
Advantages
Stud Attachments
• Low profile
• Easy hygiene maintenance
• Enhanced crown/root ratio
Dalla Bona
The Ball Attachment
A spherical, resilient, adjustable stud
attachment with vertical and rotational
movement for retaining partial and complete
overdentures
Advantages
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Low Profile - limited space
Easy path of insertion
Adjustable female
All adjustments done in prostheses
Can be rigid – vertical movement only
Can be resilient – vertical and rotational
Easy fabrication
Hygienically maintainable
Accessory Attachments
Plunger
Screw Type
Frictional
Magnetic Attachments
• Processing magnet- in denture
• Intraradicular keeper
All magnetic attachments should be
processed chairside in the denture
Magnetic Indications
• Overdentures
• Implant restorations
Magnetic Realities
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Provide little lateral stability
Used in limited applications
Heat curing will weaken magnets
Corrosion
Attachment Selection
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Overdentures- Ridge evaluation and esthetics
Fixed- Ridge evaluation, gingival esthetics
Number of implants
Anterior-Posterior spread
Opposing arch ??
Function
Fixed- Rigid, screw retained
Overdenture- Load bearing or nonload bearing
• Retention
• Available space
• Cost
Patient Considerations
• Parallel attachments for easier path of
insertion
• Less attachments – better
• Patient dexterity
• Hygiene – Stannous Fluoride rinses
• 3 month recall
Anterior/Posterior Spread
A line from the center of the most anterior
implant to a line joining the distal aspects
of the two most distal implants
Indicates the amount of cantilever that can
be reasonably placed
Usually, 2.5 times the A/P spread
A/P Spread
Actual Length of Cantilever Depends on:
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Stress factors
Parafunctional Habits
Crown heights
Implant width
Number of implants
Opposing teeth or denture
Controlling Stress
Stress=Force/Area
Force
Stress
Area
Torque=
Force x Perpendicular distance
from the line of force to the
center of rotation
Cuspal Inclination
Cuspal Inclination
Treatment Plan
Options
Fixed
Implant Supported
Removable
Soft Tissue Supported
Implant Retained
Treatment Plan
Option 1
Lower Edentulous
Fixed
5-6 Implants
Prosthetic Options-Lower
5-6 Implants
• Hybrid Denture
• Fixed Crown and Bridge
• Cantilever 10-15mm
6 Implants-Fixed
Implant Supported
24
23
22
X
X
25
26
27
X
X
5 Implants- Fixed
Implant Supported
B
A
X
X
C
D
E
X
X
Treatment Plan
Option 2
Lower Edentulous
Removable
5 Implants
Prosthetic Options- Removable
Overdenture-Implant Supported
• Gold Bar w/ O Rings
• Distalized O Rings
• Cantilever 10-20mm
• Gold Bar with Hader Clips
• Distalized ERA’S
• Cantilever 10-20mm
C
B
A
C
D
B
E
A
D
E
Treatment Plan
Option 3
Lower Edentulous
Removable
4 Implants
Prosthetic Options- Removable
Implant and Tissue Supported
• Gold Bar with O Rings
• Cantilever 5-10mm
b
a
• Gold Bar with Hader
Clips and ERA’S
• Cantilever 5-10mm
b
c
d
a
c
d
Treatment Plan
Option 4
Lower Edentulous
Removable
3 Implants
Prosthetic Options- Removable
Overdenture-Lower
Implant and Tissue Supported
• Gold Bar w/ 2- O RingsOverdenture
• No Cantilevers
3 Implants- Removable Overdenture
Implant and Tissue Supported
C
B
D
Treatment Plan
Option 5
Lower Edentulous
Removable
2 Implants
Prosthetic Options
Removable Overdenture-Lower
Tissue Supported
• Gold Bar w/ Hader Clip
• O Ring on each implant
• ERA attachment on each
implant
2 Implants-Removable
Tissue Supported
B
D
Treatment Plans
Upper
Edentulous
Four
Options
Treatment Plan
Option 1
Upper Edentulous
Fixed
8 Implants
Prosthetic Options
Fixed- Upper
Implant Supported
• Fixed Crown and Bridge
• Hybrid Denture
• No Cantilevers Necessary
8 Implants- Fixed
Implant Supported
X
7
6
X
4
3
X
10
11
X
13
14
Treatment Plan
Option 2
Upper Edentulous
Removable
8 Implants
Prosthetic Options- 8 Implants
Removable- Upper
Implant Supported
• Gold Bar w/ O RingsOverdenture
• Gold Bar w/ 3 Hader Clips
Overdenture- No Palate
• Cantilevers-Optional
8 Implants- Removable
Implant Supported
• Gold Bar Overdenture • Gold Bar Overdenture
w/ O Rings
w/ Hader Bar / Clips
7
10
6
7
11
4
6
13
3
14
Palate
10
11
4
13
3
14
No Palate
Treatment Plan
Option 3
Upper Edentulous
Removable
6 Implants
Prosthetic Options
Removable- Upper
Implant Supported
• Gold Bar w/ 4- O Rings and distal
to #s 4 and 13
• Gold Bar w/ Hader Clip- ERAS
distal on #4 and 13Overdenture-No Palate
• Cantilever 5-10mm
6 Implants- Removable
Implant Supported
• Gold Bar w/ O Rings
• 5-10mm Cantilever
7
5
4
• Gold Bar w/ Hader
clips and ERA’s
• 5-10mm Cantilever
10
7
12
13
5
4
10
12
13
Treatment Plan
Option 4
Upper Edentulous
Removable
4 Implants
Prosthetic Options
Removable- Upper
Tissue Supported
• Gold Bar w/4 O RingsOverdenture w/ No Palate
• Gold Bar w/ Hader Clip and 2
distalized ERA attachments w/
Overdenture- No Palate
• No Cantilever
Arch Form
4 Implants-Tissue Supported
Square Arch
6
4
Tapered Arch
11
6
13
11
5
Maximum contact with tissue – No contact with Bar
Attachments are for retention ONLY
12
Treatment Planning
• Design sensibility and flexibility in the
treatment plan
• Design and implant concepts will vary
• Plan ahead for success
• Have a disaster plan
• In most cases, less attachments are better
What Is an Overdenture
A complete denture
that is supported and often
retained by the underlying
teeth or implants and tissue
Abutment teeth or implants
may or may not
be connected to the denture
via attachments
Bars
Studs
Load bearing
Magnets
Copings
Implants
Overdenture Attachments
Teeth
Extraradicular
Combinations
Posts
Non-Load-bearing
Intraradicular
?????????????????????????????????
Overdenture Attachments
Radicular:
Bars:
• Extraradicular
• Bar joints
• Bar units
Studs, magnets,
ERA
• Intraradicular
Zaag, Zest,
Sterns
root
anchor
Round
Ovoid
Square
Rectangular
Objectives of the Program
• Understand how overdentures preserve
hard and soft tissue
• Maintain proprioception
• Understand the function of overdenture
attachments and simplify attachment
selection
• Increasing crown/root ratios to preserve
abutments
• Hygiene maintenance
Carlson and Persson, Odontologist Revy, Sweeden 1967
Anterior mandible
“average bone loss first year after extractions was 4mm”
Tallgren, JPD,1972
“Bone loss continues for at least 25 years”
Dentures vs Overdentures
• Natural
dentition
Chewing
90%
Efficiency
• Complete dentures
59%
• Overdentures
79%
Rissin and House, JPD, 1978
Indications for Overdentures
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Periodontal disease
Few remaining teeth
Insufficient crown/root ratios
Vertical space
Favorable path of insertion
Retention
Advantages of
Overdentures
• Maintenance of bone height around teeth by
preserving roots
• Attenuates resorption patterns of alveolar
ridges
• Gentler to the tissues
• Increases crown/root ratios
• Psychological security
• Enhanced speaking ability
• Maintains Proprioception
Disadvantages of Overdentures
• Esthetic Considerations –
Bulkiness
• Root canal therapy
• Increase space requirements:
-interarch
-interocclusal
• Increase costs
Crown / Root Ratios
Attachment Retained
Overdentures
All the advantages of Overdentures
PLUS
•Superior aesthetics
•Increases proprioception
•Stability and comfort
•Mechanical retention
•Rigidity or resiliency
•Support
•Increased psychological security
and patient acceptance
Overdentures
Attachment Considerations
Load Bearing
Solid / Rigid
• Transfers stress towards the retained
roots or implants and away from the ridge
• No vertical resiliency, some hinge or
rotational resiliency
• Shares the load of occlusion with the
mucosal surface
Magnets, Flexi ball, Dalbo Rotex, Bars
Overdentures
Attachment Considerations
Non- Load Bearing
Resilient
• Transfers stress away from the
retained roots or implants and towards
the tissue
• Vertical resiliency
• Selected frequently
Dalla Bona, Rotherman, Ceka, Uni Anchor, OSO,
ORS, ERA, Bars
Overdenture Evaluation
Partial Denture
Present
• Tooth position
• Occlusion
• Mount casts to vertical
dimension
No Partial Denture
• Mount cast to vertical
dimension
• Diagnostic denture wax
up – reestablish
occlusion
• Silicone matrix for
space evaluation
Direct Placement
• Male or female premanufactured attachment
is cemented into root
• Denture is made and inserted
• Corresponding male or female attachment is
inserted in root
• Attachment is picked up directly in the
overdenture with cold cure acrylic
Placed by Dentist
Indirect Placement
• Male or female attachment is cemented
into root or may need to be cast onto
coping
• Corresponding male or female transfer
analog is inserted into root attachment
• Transfer impression is taken and models
are poured with transfer in place
• Laboratory processes denture with
corresponding attachment in place
Placed by Laboratory
Proceedures To Follow
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5 mm or more root remaining in bone
Stable perio
Mount study models – evaluate space required
Select OD attachment – obtain reference manuals
Begin denture proceedings
Root canal therapy
Decoronate roots, extractions, insert temporary
denture – reline – allow time for healing
• Prep tooth for attachment and cement attachment
• Insert denture, make adjustments, post placement
reline
• Pick up male attachment in denture
Hader
Spark Erosion
Round
Andrews
Ovoid
Dolder
Bar Designs
Double Bar
Branson
Custom Milled
Rectangular
Square
Attachments and Bars
•Intra Bar
•Extra Bar
•Circum Bar
Extra Bar
Attachment placed on the superior aspect of
the bar
•Increases strength of bar
•Requires more interarch space
Intra-Bar
Connection between the two components
directs the forces of mastication closer to
the crest of the ridge
•Decreases lever arm mechanics
on the supporting teeth
•Bar strength may be
compromised
Circum-Bar
Attachment wraps itself around the bar
•Allows for rotation around bar
The Milled Bar
Main Advantage
Final prosthesis is extremely stable because
lateral forces are best managed by an
intimately fitting primary and secondary
bar
This minimizes stress on the attachments
The Bar Overdenture
Advantages
• Increased stability and retention than an
attachment retained overdenture
• Accomodates a wide variety of implant
angulations
• Bar splints implants together
• Provides better resistance to lateral forces when
in function
• Pose less of a chance of failure at
bone-implant interface
The Bar Overdenture
Disadvantages
• More costly
• More technique sensitive