Edentulous Maxilla - Overlay Dentures

6. Edentulous Maxilla
Overlay Dentures

John Beumer III DDS, MS
Hiroaki Okabe CDT
Division of Advanced Prosthodontics, Biomaterials and
Hospital Dentistry, UCLA
This program of instruction is protected by copyright ©. No portion of
this program of instruction may be reproduced, recorded or
transferred by any means electronic, digital, photographic, mechanical
etc., or by any information storage or retrieval system, without prior
permission.

Patient selection and treatment planning
Implant Assisted vs Implant Supported
Fixed vs Removable Overlay Dentures
!Fixed detachable
!Implant assisted prosthesis (Implant
! Fixed prosthesis overdentures supported overlay
dentures with milled bars)

Definitions
Implant assisted prosthesis
The forces of occlusion are shared
between the implants and the
mucoperiosteum. Always
removable overlay dentures.

Implant supported prosthesis
All the forces of occlusion are
borne by the implants. Can be
either fixed partial dentures or
removable overlay dentures.

Edentulous Maxilla
Most patients are best served with
implant assisted overlay dentures. Why?

Treatment Planning and Patient Selection
Edentulous Maxilla
! Bone quantity and quality
! Resorptive patterns
! Maxillomandibular relations
! Sinus architecture
! Esthetics/lip support
! Phonetics
! Hygiene access and patient compliance
! Cost
! Predictability of surgical interventions
In most patients careful consideration of these factors will favor
implant assisted removable overlay dentures.

Resorptive patterns and maxillo-
mandibular relationships
Fixed vs Removable
The normal patterns of
resorption result in pseudo
class III jaw relations.

Overlay dentures (either
implant supported or
implant assisted) are
preferred over fixed
prostheses. Why?

Removable overlay dentures with properly extended and contoured
denture flanges provide better lip support and facial contours.

Esthetics/Lip Support

Most elderly patients require
the lip support provided by the
labial flange of an overlay
denture particularly if they have
been wearing a maxillary
denture for an extended length
of time.

Esthetics - Lip Support
Fixed vs Removable
!   Fixed in retrospect was a poor choice
!   As the patient aged and lost tonus of
the lip musculature lip contours became
deficient

Fixed vs Removable
Fixed was an appropriate choice
for this patient
!   More favorable jaw relationship. Lip support
from the prosthesis is not required to same
degree as the previous patient.
!   Low smile line meant the proximal spaces
designed for hygiene access are not visible.

Fixed vs Removable
Lip line
v  If
the patient presents with a high lip line they
are probably best served by an overdenture

Phonetics – Fixed vs Removable

!   This design was used frequently in the 80’s. Note the spaces beneath
the bridge. These spaces facilitate hygiene but during speech air
escapes through these spaces adversely affecting speech articulation.
Removable overlay dentures prevent this problem.

Fixed vs Removable
The speech vs hygiene dilemma
v  If you close the spaces and provide lip support
access for oral hygiene is compromised
v  If you provide hygiene access, you compromised
lip support and speech articulaion

Phonetics and esthetics vs hygiene
access

Fixed vs removable
! Hygiene access requires space between the implants and underneath the fixed
bridge.
! In a fixed prosthesis these spaces may compromise speech articulation (because
of air flow beneath the prosthesis) and esthetics
! Much easier to clean beneath tissue bar than beneath fixed partial denture
! These spaces are closed with an overlay denture and speech articulation is close
to normal and hygiene access is maintained

Implant Supported Prostheses
Edentulous maxilla
Minimum requirements from a biomechanical
perspective
!   Six or more implants
!   Minimum of 2 cm of A-P spread
!   Distal implant must be at least 10 mm in length

Few patients qualify and if these conditions cannot
be met implant assisted designs are recommended.

Implant Supported Prosthesis
Arrangement of implants
!  Maxilla - Anterior-Posterior Spread required for
implant supported prosthesis - 2 cm or more

Less than the above
dictates use of an implant A-P Spread
assisted prosthesis

Sinus architecture
Pneumatized sinuses in most patients do not permit
the placement of implants posterior to the cuspid – 1st
premolar region.

As a result, A-P spread is insufficient to
fabricate an implant supported prosthesis.

Fixed vs Removable
Masticatory Function

v  No difference in chewing efficiency

Fixed vs Removable
Patient Compliance

v  Fixed prostheses are very difficult to clean properly
v  If the patient has difficulty manipulating hygiene aids
they are best suited for a removable overdenture

Cost: Fixed vs Removable Overdentures

Fixed is double to triple the cost of implant
assisted removable overlay dentures.

Most expensive Least expensive
Fixed prosthesis Implant supported Implant assisted
a) More implants overlay dentures overlay dentures
b) Time consuming a)More implants a)Fewer implants
and costly to b)Bars need to be milled b)Less labor for
manufacture which adds to the manufacture
cost of manufacture.

Implant assisted overlay dentures

Implant assisted
with resilient
attachments
posteriorly

Advantages
a)  Phonetics
b)  Hygiene access
c)  Favorable biomechanics
d)  Better lip contours
e)  Cost

Prosthodontic Designs
and Procedures

Four Implant Assisted Overlay Denture

l  Preferred choice in most patients
l  Implant assisted designs must be used
l  If A-P spread is adequate and length of implants
is adequate, a palateless denture is permitted

Implant assisted design developed at UCLA
The anterior two implants should
be 12-20 mm apart
! This segment is restored with a
Hader Bar

v ERA attachments are positioned adjacent to the distal implants. This attachment
permits the overlay prosthesis to be compressed into the mucoperiosteum in the
extension areas when posterior occlusal forces are applied to the overlay denture. As a
result, the denture bearing tissues absorb the posterior occlusal forces
v This combination of attachments provides excellent retention while at the same time is
biomechanically sound (Williams et al, 2003).

Maxillary Retention Methods

Retention of maxillary implant overdenture bars of different designs.
Williams BH, Ochiai KT, Hojo S, Nishimura R, Caputo AA.
PURPOSE:
The purpose of this study was to evaluate the initial retention characteristics of 5 implant
maxillary overdenture designs under in vitro dislodging forces.

MATERIAL AND METHODS:
A simulated edentulous maxilla was fabricated with 4 screw-type 3.75 x 13-mm implants
anteriorly. Five overdenture designs with the following attachments were evaluated: 4
plastic Hader clips with an EDS bar; 2 plastic anterior Hader clips with an identical EDS
bar; 2 Hader clips with 2 posterior ERA attachments; 3 Zaag attachments on a bar; and
4 Zaag attachments with no bar. Overdentures were fabricated with full palatal coverage.
Each design was subjected to 10 consecutive retention pulls on a universal testing
machine. Data were subjected to analysis of variance and t tests to determine
differences.

RESULTS:
The highest average value after 10 pulls was 19.8 lb for the combination ERA and Hader
clip design. The lowest retentive values were recorded for the 2 and 4 Hader clip
designs (5.08 +/- 0.89 lb and 5.06 +/- 0.67 lb, respectively). Retention decreased over
the course of consecutive pulls for all designs, especially for the most retentive designs.
The smallest retention decrease occurred with the least retentive designs.

26

24

Retentive Force (lb)

22

20

18

16

14

12

10

8

T
h
e
i
T
h
m e

6

a
g
e
c
i
m
a
g
a e
n

4

c
n a T
ot n h
b n e
e o i
di t m T

2

s
pl
a
y
b
e
d
is
a
g
e
c
h
e
i
m
T
h
e
T
h
i e

0

ERA/Had

4 Zaag

dir

3 Zaag/

bar

4 Clip

2 clip

Locator

Snap

Snap/bar

Implant Supported vs. Implant Assisted

The distance
Factors Determining between the
Implant Supported vs. Assisted-AP of the
center Spread
most anterior
4 Implant Assisted Overlay Denture
VS. implant and the
4 Implant Rotation”
“Axis of Bar Design-Axis distal of the most
ERA
of Rotation
Hader
Attachment
posterior implant
Implant Assisted
Clip
Overlay Denture

Relatively Favorable

Why are implant assisted designs preferred
when only four implants are placed?
v  To minimize the possibility of implant overload and implant
failure
v  At UCLA when implant supported designs were used the
distal implants often failed after 3-6 years of service
v  When we switched to implant assisted designs the failures of
posterior implants ceased.

Implant supported design Implant assisted design

vs

Implant Overload – Implant Supported Designs

Overlay Dentures in Edentulous Maxilla
Four implanted supported overlay dentures with nonresilient
(Hader) attachments (arrows) and distal cantilevers
Patients # Implants Followup Failures Position Time of
of failed failure
implants

10 40 5-12 yrs. 4 all distal 39-73 mths.

***Failures were attributed to implant overload, causing loss
of bone around the implants and eventual implant failure.

Four implant supported design
Case Report

l  Hader bar attachments
had been placed adjacent
to the distal implants

After 4 years of use the retention bar
fractured . Further exam revealed that the
distal implant had lost lost osseointegration.

Four implant assisted design
Implant placement
v  Implants should exit at the ridge crest
v  The two anterior implants should be a minimum of 20
mm apart (measured from the center of the implants)
v  The posterior implants should be placed as posteriorly
as possible to maximize A-P spread.

At least
20 mm
Maximize
A-P Spread

! Implant position in this patient is ideal.

Four implant assisted design*
Implant angulation
! The two anterior implants exit the mucosa at the ridge crest. This is ideal
angulation because the bar fabricated will not distort the palatal contours.

*Ucla design

!The labial inclination of the two anterior implants is of little
consequence with respect to the application of occlusal load
since this will be an implant assisted design.

Four Implant Assisted Overlay Denture*
! These two anterior implants are in ideal position.

!The distance between the two implants is sufficient
for placement of two clips. As a result the denture
will be more stable and the rate of clip wear will be
reduced.

*Ucla design

Four Implant Assisted Overlay Denture*
! Implant position
*Ucla design

! These two anterior implants are too close together and
will allow for the placement of only one Hader clip.
! Insufficient A-P spread
This implant arrangement will result in a less stable denture
and the anterior clip will wear more rapidly than if two clips
had been possible.

Four Implant Assisted Design*
Implant angulation
! Note the palatal position and angulation of these implants.

!In such a patient it will be difficult to design a bar
which does not distort palatal contours and impair the
tongue space. *Ucla design

Four Implant Assisted Overlay
Denture*
! Implant position
! Good A-P spread
! Sufficient space between the two anterior
implants

Implant angulation and position
Position and angulation of the
implants in these patients are
unfavorable but with a tissue bar
these discrepancies can be
overcome.

Four Implant Assisted
Design*
Unfavorable implant angulation

Problems
v Unfavorable biomechanics
v Increased cost of the laboratory Short narrow diameter implant
procedures used as a posterior stop.

Implant angulation

v The anterior two implants are too close together and angled excessively to
the labial.
v The anterior portion of the “Hader” bar is placed palatal to the implants and
the portion over the implants is tapered to allow for proper positioning of the
denture teeth.
v Palatal positioning of the bar allows placement of two “Hader” clips.

Four Implant Assisted Denture
Implant Placement

Surgical templates, generally a duplicate of the
existing denture, will ensure proper implant position
and angulation.

Four Implant Assisted Overlay Denture
Healing Abutments

! Tapered configuration prevents the
mucosa from collapsing over the fixture
upon removal of the abutment facilitating
impressions, verification of metal
l  Tapered healing frameworks etc.
abutments with polished
surfaces are favored
l  Smooth surfaces retain
less plague facilitating
more rapid mucosal
healing

Four Implant Assisted Design

Impression copings
!   Transfer type (closed tray
!   Pick up type (open tray)

Impressions
v  Border mold with dental compound in order to develop
proper thickness and extension of the labial-buccal
flange.
v  The posterior palatal seal area need not be recorded
v  Materials used for corrected impression
v Polysulfide
v  Light body polysulfide is preferred by many prosthodontists
impressions of the edentulous arch because of its flow and minimal
tissue displacement
v  Permitted when the pickup (open tray) impression copings are linked
and are designed to remain in the impression when removing the
impression from the mouth
v Polysiloxane
v  Canbe used with transfer type copings because of its rigidity and
better accuracy

Rubber Base (Polysulfide)
v  Advantages
v  Good edge strength
v  Moderately inexpensive
v  Optimal flow
v  Minimal tissue displacement
v  Disadvantages
v  Does not recover well from deformation upon removal
v  The material must be held still during the impression making
procedure because the material does not have a snap set
v  Requires carefully fabricated custom trays that ensure uniform
thickness of the impression material
v  Unpleasant odor
v  Stains clothing

Silicones
Advantages
v  More accurate than polysulfide
v  Less polymerization shrinkage
v  Low distortion
v  High tear strength
v  Fast recovery from deformation
v  Short working times (3-5 minutes for addition reaction types and 5-7
minutes for condensation types)
v  Can be used in a stock tray
v  Available in both hydrophilic and hydrophobic forms
v  Available in automixing devices
v  Multiple pours are possible if poured within 1 week

Disadvantages
v  More expensive compared to polysulfide
v  Displaces tissues

Impressions with linked “pick up” type
impression copings and polysulfide

!Pickup impression copings are secured to
the analogues imbedded in the preliminary
cast with long guide pins.


!Impression copings are linked together
with resin.


A thin separating disc is used to separate each of the
copings from one another. These will later be luted
together on the patient.

impression copingsand polysulfide

The impression copings are blocked out with baseplate wax.
The top of the guide pins are left exposed,


v Separating medium is applied to
the cast
v The tray is fabricated of tray
resin taking care to expose
the tops of the guide pins


v The long guide pins are removed.
v The screw access holes are widened
to ease insertion of the tray
v The portion over the screws is
thinned to minimize the bulk of
the tray

Impressions with “pick up” type impression
copings and polysulfide
v  Border molded impressions made with a custom tray need to be made in
order to record the thickness, contour and length of the buccal and labial
flange of the overlay denture.
v  Custom impression tray must be terminate 1-2 mm short of the depth of
the vestibule.

!The posterior palatal seal area need not be displaced and recorded
because a palateless denture is being fabricated.

Impressions with “pick up” type
v  Once the border molding is completed the impression copings are secured to
the implants
v  The impression copings are connected together with cyanoacrylate or Duralay
v  The impression is corrected with a poly sulfide impression material

Note: Since this is to be a palateless
denture, the posterior palatal seal area was
not recorded in the usual fashion.

Impressions with “pick up” type
v  Once the border molding is completed the impression copings are secured to
the implants
v  The impression copings are connected together with cyanoacrylate or Duralay
v  The impression is corrected with a poly sulfide impression material

Note: Since this is to be a palateless denture, the posterior palatal seal
area was not recorded in the usual fashion.

Impressions with “pick up” type impression
copings

Fixture analogues are attached and the impression is
boxed and poured in the usual fashion

Impressions with transfer type impression
copings and polysiloxane
v  If transfer type impression copings are used
we recommend making the corrected
impression with a polysiloxane because of its
rigidity and accuracy.
v  Before use these copings must be carefully
inspected for nicks and indentations that may
prevent appropriate seating into the
completed impression.

Impressions with transfer type
impression copings and polysiloxane

v  This impression was made with transfer type copings
v  It was border molded with dental compound and corrected
with polysiloxane

Master cast
v  Note land area. This is useful if a land indexed matrix is used
to develop the contours of the bar.
v  Fixture analogues were imbedded in this cast.
v  Healing abutments of sizes equivalent to those in the patient
were secured in preparation for fabrication of a record base.

Record Bases

The cast undercuts and those
around the healing abutments,
are blocked out with wax,
separating medium is applied and
the record base completed with
tray resin.

Face bow transfer record is made and the
maxillary cast is made

Centric relation records
! Centric relation records are made following a face
bow transfer and mounting of the maxillary cast.

Trial dentures

! At try in the vertical dimension of occlusion and the centric
relation record need to be verified, and a protrusive record
made and transferred to the articulator.
! The teeth are arranged to achieve bilateral balanced occlusion

Land based dental matrix
v  The land must be 4-5 mm wide if
the matrix is to be sufficiently
stable.
v  The matrix is made of silicone
putty.

v  Thedenture teeth are
attached to the silicone
template with sticky
wax.

v  Thetemplate positively engages the cast during
fabrication of the tissue bar

Alternative method
l  Occlusal index is made and is
mounted on the lower member of
the articulator

Tissue Bar Fabrication

! The path of insertion is determined with a
surveyor. Beware of undercuts associated with
the alveolar ridge anteriorly.

Ucla abutments
! The UCLA abutment technique is favored
because there is a lack of interocclusal
space in most patients.
! Fabrication begins by attaching a UCLA
abutment to a fixture analogue with a guide
pin and coating guide pin and the top of the
UCLA abutment with pattern resin.
! Abutment–pattern resin units are attached
to fixture analogues imbedded master
cast. Non-hexed UCLA abutments are
used.

! The Hader bar is used
anteriorly, determines the
axis of rotation and
provides retention.

! The metal housings will
eventually become
imbedded within the
denture base (arrow).

! Note that in cross section
the bar is circular, thus
permitting free rotation
around the axis of rotation.

v  The Hader bar segment is shaped to
the proper contour and length and
attached to the anterior implant
abutments consistent with the path of
insertion and the planned axis of
rotation using a specially prepared
surveyor rod.
v  The bar should not touch the tissues
of the alveolar ridge

v  Extracoronalresilient
attachments (ERA) are
connected to the distal
portions of the tissue bar

v  TheERA attachments
provide retention and
allow the prosthesis to
rotate around the
“Hader” bar anteriorly
when posterior occlusal
forces are delivered to
the overlay denture

! The female portion of the attachment should be
secured to the posterior implants with a surveyor.

! The path of insertion of the of the Hader bar
attachment and the ERA attachments should be
identical.

! The bar must fit within the confines of the denture
base and not distort the palatal contours.

Hader bar is parallel to the occlusal plane and perpendicular to
the midline

The ERA
attachment should
be 1-2 mm above
the tissues

v Hader segment should be perpendicular to the midline and
parallel to the occlusal plane. This will ensure a pure rotation
around the Hader bar when occlusal forces are generated
posteriorly.
! Wax contours are completed
making sure there is proper
hygiene access
! Space should be sufficient to
accept a prophy brush


v The anterior portions of the bar is often tapered to
accommodate the anterior denture teeth.
v Note the hygiene access beneath the bar and
between the implants

Completed pattern

v Note the hygiene access between the implants and
underneath the bar
v Note that the ERA attachment is 1-2 mm above the level of
the tissue
v The tissue bar has been tapered so as to accommodate
the proper positioning of the denture teeth
v At this point the pattern can either be invested and cast or
scanned and milled


Finished casting. Note the hygiene access. If proper hygiene
access is not provided the gingival tissues will likely
hypertrophy and envelop the tissue bar and the ERA
attachments.

Completed bar
v  The Hader segment is
perpendicular to the midline
and parallel to the occlusal
plane. It serves as the axis
of rotation

v  The path of insertion for the
Hader bar and ERA
attachments are identical

Completed bar
! Note hygiene access beneath bar and between the implants

Completed bar

! Metal housing for the
! ERA attachment ERA attachment

! Metal housing
for Hader clips

Completed bar

The bar must fit passively, otherwise it must be sectioned and soldered

Processing
v Prior to processing a metal casting is fabricated to
provide rigidity for the overlay denture
v The metal reinforcement framework is secured in
its proper position

Processing
v The metal housings for the attachments are secured to the
tissue bar. The black processing attachment is used for the
ERA .
v The tissue bar is blocked out with plaster.

Insertion of attachments
The processing attachment
is removed with the
provided tool and replaced
with an ERA of light to
medium retentive value.

Finished prostheses with attachments
inserted

In these cases the housings for the attachments are
incorporated within the cast metal of the framework.

Delivery Sequence

v Attach the tissue bar with gold alloy screws
v Torque the screws to 20 N/cm but no more

Delivery Sequence

! Secure the tissue bars to the implants
! Pressure indicating (PIP) used to eliminate areas
of excessive tissue displacement
! Check borders with disclosing wax
! Clinical remount

Delivery Sequence

Pressure indicating paste (PIP) is used to identify and remove
areas of tissue displacement during insertion, removal and when
occlusal forces are generated anteriorly.

Note the undercut
associated with the denture
border on the right side
(arrow). This must
removed to avoid abrading
the tissues in this area
during insertion and
removal of the prosthesis.

Delivery Sequence

Disclosing wax is used to verify the length and
thickness of the denture borders

Delivery Sequence
Clinical remount
Purpose
To Correct for the fact that:
!   The completed prosthesis seats more accurately than record
bases
!   Accommodate for errors made during the
making of centric relation records

Completed Overlay Denture Opposing
Fixed Hybrid Prosthesis

This maxillary overlay denture is
opposed by a fixed hybrid
prosthesis. Note the hygiene
access beneath the mandibular
prosthesis and between the
implants.

Completed maxillary overlay
opposing mandibular overlay

•  Clips need to changed about every 12-18 months
•  Denture teeth wear out 7-12 years
•  Tissue bars wear out 12-15 years.

Four implant assisted overlay
dentures
Problems
! Fracture of acrylic resin overlying the bar
! Wear of denture teeth
! Wear of the tissue bar

Problems:
!  Resin crazing and fracture

Problems
Solution:
•  Metal reinforcement – Prevents flexure of the
prosthesis and crazing and subsequent fracture
of acrylic resin overlying the bar

Problems
The resin is too thin (arrows) overlaying the tissue
bar in this case. As a result the resin in this region
will be susceptible to fracture. The solution is to
cover the tissue bar with resin

Preventing Resin Fractures

Metal frameworks that cover the tissue bar
! When lack of inter occlusal space results in resin
covering the tissue bar to be excessively thin
! Bruxers and clenchers
! Brachycephalics
! Opposing natural dentition

Metal framework designs

Metal housings for ERA and
Hader attachments have been
incorporated within the cast
metal framework

Bruxers and Brachycephalics

v  Patient with brachycephalic facial form with
evidence of chronic buxism presented with
edentulous maxilla opposing dentate mandible
v  Implants were used to restore posterior occlusion in
the right mandible

Bruxers and Brachycephalics

Completed prostheses
v  Occlusion – Bilateral
balance

Lack of Interocclusal Space

! Incorporate the metal
housings within the metal
framework

Excessive occlusal wear
A B C

Wear of denture teeth with implant assisted
overlay dentures. Figures A, B,and C (12
D
years of wear) represent an overlay denture
opposing a fixed hybrid prostheses with
resin composite denture teeth. Figure D
(21 years of wear) represents an overlay
denture opposing natural dentition.


Amalgam stops
! These have been relatively ineffective. Note the
wear around the amalgam stops.


Metal occlusals
! Chrome cobalt
! Gold occlusals

Fifty-five y/o male, presented with a spark-erosion implant supported overlay
denture done delivered in the 80’s. Further tooth loss in the mandibular
posterior quadrants were replaced with implant-supported FPD.

Exam revealed the maxillary posterior denture teeth to be worn down excessively by the
opposing mandibular implant-supported FPD (porcelain occlusals). Solid centric
occlusal contacts were found only on anterior teeth. Lack of posterior contact resulted in
recurrent fractures and loss of anterior denture teeth associated with the overlay
denture. The precision of fit between the metal substructure of the overlay denture and
the spark erosion milled bar remained quite good.


A new overlay denture was fabricated using the
existing metal substructure.

Solution:
Custom gold onlay on the maxillary posterior
functional cusps

Functional cusps were prepare and waxed up to
achieve proper contour and occlusal contacts.

v  Gold onlay restoring the posterior quadrants were
cemented.
v  Occlusion was refined. Occlusion was bilateral
balance

Completed prosthesis

Lessons Learned
v  The probability of rapid and excessive occlusal wear when resin denture teeth are
opposed by natural dentition or restorations fabricated with porcelain occlusal
surfaces
v  Custom gold occlusals will reduce the rate of wear and maintain the VOD and solid
occlusal contacts.
v  Osseointegrated implants outlasts the prosthodontic material. Maintenance and
replacement costs need to be discussed during initial consult.


Opposing mandibular dentition
was restored with porcelain
occlusal surfaces. Gold
occlusals were used to restore
maxillary lingual cusps to
minimize wear and prevent loss
of VDO.

Excessive wear of the
Hader bar and ERA attachments

This implant assisted tissue bar was
fabricated of type V gold alloy. It
has been in function 21 years.
Excessive wear of both the Hader
bar and ERA female attachments
has made the overlay denture
nonretentive.

v  Note the excessive wear of the ERA attachment (a)
as compared to a newly fabricated tissue bar and
attachment (b). This attachment has become
nonretentive. This represents 21 years of wear.

a b

a b

v  Note the excessive wear of the Hader bar (a) as
compared to a newly fabricated Hader bar (b).
This tissue bar has become nonretentive. This
represents 21 years of wear.

Other implant assisted designs
“O” ring type attachments
Used when
• When implants cannot be splinted together

!Non parallel implants results in uneven wear of the
attachments and loss of retention.

Other implant assisted designs
“O” Ring Attachments are used when:

! Solitary implants
! Implants are so far apart that they cannot be splinted together

! Implants are short

! Implants in poor quality bone where there is high risk of implant
overload

Other Implant Assisted Designs
Maxillectomy Defects

Note the rests on the bar. The axis of
rotation pass through these rests and
permits the ERA attachments to function
in a way for which they were designed.

Patient presents with a repaired bilateral cleft of the lip
and palate

Note:
! The premaxillary segment is missing
! The cleft has not been reconstructed
with a bone graft
! The profound Class III jaw relation
!Three implants were placed
on each side of the cleft.

Bar design uses ERA attachment anteriorly
and Hader attachments posteriorly

Note:
v  The extreme class III jaw relation and the lack of anterior support
v  The implant bar does not cross the cleft. These segments move
independent of one another during function
v  The bar is designed to accommodate the anterior extension
v  When occlusal loads are applied anteriorly, the prosthesis rotates around
the posteriorly situated Hader attachments. The ERA attachments permits
the prosthesis to be impacted into the anterior extension area. This design
will limit the force delivered to the anterior implants on each side.

Bar design uses ERA attachment anteriorly
and Hader attachments posteriorly

Note:
Implant the implant assisted design of the tissue bar in the
mandible. The bar has been configured to be perpendicular to
the midline to enable a more pure rotation when posterior
occlusal forces are applied to the denture.


Completed prostheses
Note:
v Implant assisted designs were used in
both arches
v Full palatal coverage to facilitate support
in the maxilla
v Occlusion is bilateral balance


! Similar problem in a normal patient
! Premaxilla resorbed but bone available posteriorly for placement of
relatively short implants (8 mm in length)
! Opposing natural dentition in the mandible
! A bar crossing the arch and splinting both sides together would have
created an extensive cantilever predisposing the bar and the anterior
implants to a high risk of fracture or implant overload and bone loss.
! Occlusion was lingualized with bilateral balance
! Note: Some of the fixed in the mandible was redone to idealize tooth contours
and the plane of occlusion

v  Visitffofr.org for hundreds of additional lectures
on Complete Dentures, Implant Dentistry,
Removable Partial Dentures, Esthetic Dentistry
and Maxillofacial Prosthetics.
v  The lectures are free.
v  Our objective is to create the best and most
comprehensive online programs of instruction in
Prosthodontics

Edentulous Maxilla - Overlay Dentures

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (20)

En vedette

En vedette (20)

Similaire à Edentulous Maxilla - Overlay Dentures

Similaire à Edentulous Maxilla - Overlay Dentures (20)

Plus de www.ffofr.org - Foundation for Oral Facial Rehabilitiation

Plus de www.ffofr.org - Foundation for Oral Facial Rehabilitiation (20)

Dernier

Dernier (20)

Edentulous Maxilla - Overlay Dentures