Edentulous Mandible - Overlay Oentures

4. Edentulous Mandible
Overdentures

John Beumer III DDS, MS, Robert Faulkner DDS
and
Hiroaki Okabe CDT
Division of Advanced Prosthodontics, Biomaterials and
Hospital Dentistry, UCLA
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Table of Contents
!  Conventional dentures vs implant retained dentures.
!  Which patients benefit from implant retention
!  Patient satisfaction: Conventional dentures vs implant retained dentures
!  Treatment choices
!  Clinical outcomes studies
!  Fixed vs removable
!  Issues of concern
!  O Rings and similar type attachments
!  Advantages vs disadvantages
!  Prosthodontic procedures
!  Complications
!  Hader bars Prosthodontic procedures
!  Prosthodontic procedures
!  Complications
!  Magnetic attachments
!  Mini-Implants
!  Implant supported tissue bars
!  Treatment of the severely resorbed mandible
!  The 4 implant assisted tissue bar

Conventional Dentures: Pt. Satisfaction
Most patients are satisfied with their dentures in spite
of the difficulties referred to in the previous slides.

Dissatisfied
7.7 %

Moderately
Satisfied Fully Satisfied
25.6 % 66.7 %

Berg E (1998); Smedley TC et al
(1989); Kapur KK et al (1997)

Problems with mandibular dentures
!  Lack of stability, lack of retention, poor support and poor
neuromuscular control make it difficult for many patients to
efficiently manipulate the food bolus along with the lower
denture sufficiently well to masticate at levels consistent with
their expectations.

! Implants can overcome these problems in many patients
! However implants may not be necessary and may not improve
the overall level of function if the patients present with favorable
mandibular denture bearing surfaces.

Edentulous Mandible-Overlay Dentures
Conventional dentures vs implant
retained overdentures.
1.  Which patients will most likely be capable of
functioning effectively with conventional
dentures?
2.  Which patients will benefit from implant
retention?
3.  Does the addition of implants improve the
mastication efficiency of patients using
complete upper and lower dentures?

Characteristics of favorable denture bearing surfaces
Floor of Mouth Posture and Tongue Position
1.  Which patients will most likely be capable of
functioning effectively with conventional dentures?

! Floor of mouth posture and tongue position (depth of retromylohyoid space) affect
stability and retention
! Broad – rounded alveolus covered with attached keratinized mucosa enhance support
! Patients with favorable floor of mouth contours and anterior tongue position as seen
above permits development of a longer lingual flange.
! Result: Improved stability and retention of the mandibular denture
! Such patients have a good prognosis for effective use of conventional dentures

Characteristics of favorable denture bearing surfaces

!  Patients presenting with a favorable floor of mouth contour, and anterior tongue
position and a reasonable zone of attached keratinized mucosa available to
engage for support as seen in these patients are excellent candidates for
conventional complete dentures.
!  In such patients significant lingual flange extensions can be developed facilitating
stability and retention. With coverage of the retromolar pad, proper extensions
onto the buccal shelf and good adaptation with attached keratinized mucosa of the
alveolus, sufficient support will be provided.
!  Implant retention will most probably not enhance the functionality of such patients
as compared to conventional complete dentures.

Characteristics of unfavorable denture bearing surfaces
Which patients benefit from implant retention?
Patients with unfavorable floor of mouth posture and tongue position (a, b).
The tip of the tongue has lost its definition and is retruded and the floor of
mouth is elevated.

a b

Result:
! Length of the lingual flange of the denture will be limited, compromising
stability, retention and the ability of the patient to control the lower
denture and compromising the prognosis for conventional complete
dentures.
! Such patients will benefit the most from implant retained overlay dentures.

Patients with unfavorable floor of mouth contours and
retruded tongue position

!  In such patients retention and stability is provided by the
implants.
!  Support anteriorly is provided by the implants
!  Support posteriorly is provided by engagement of the
retromolar pad and buccal shelf (dotted line)

! This patient presented with a retruded tongue position, unfavorable floor of
mouth contours but a wide zone of keratinized attached mucosa on the
alveolus. Support is excellent but stability and retention will not be ideal
because the length of the lingual flange will be relatively short.

! Such patients will probably derive functional benefit from implant retention.
! The implant will enhance support but the primary benefit is improved stability and
retention,
! In addition maintenance of healthy peri-implant soft tissues will be relatively easy
because of the wide zone of keratinized attached mucosa.

Unfavorable floor of mouth contours lacking keratinized
attached mucosa
Patient (a) presented with retruded tongue position, unfavorable floor of mouth
contours and a very narrow zone of keratinized attached mucosa on the
alveolus.

Such patients would stand to gain significant functional improvement with the
addition of implants to retain and stabilize the lower denture. However with so
little attached keratinized tissue remaining, widening the zone of keratinized
attached tissue with a palatal graft should be considered in such patients.

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 overdentures.

Neuromuscular Control
Some patients have the ability to manipulate their lower
denture and control the food bolus simultaneously, regardless
of the quality of the design and construction of the denture or
the quality of the denture bearing surfaces.

The opposite is also true and those with poor neuromuscular
control will benefit from implant retention. Such patients can
focus their attention exclusively on manipulation of the food
bolus since the denture is effectively retained and positioned
with the implants.

Conventional Dentures: Masticatory Performance
Effect of Improvements in Fit or New Dentures
!  Improvements in chewing function were perceived by most
pts. despite the lack of improvement in masticatory
performance. Denture wearers may perceive chewing ability
in terms of chewing comfort rather than the ability to
comminute food, an objective measure of chewing
performance.
Garrett et al. 1996

!  Results indicate that dentists cannot rely on asking denture
wearers about chewing problems and clinical responses with
respect to oral conditions and denture quality for predicting
patient s , masticatory abilities. Masticatory ability is
determined by many factors.
Slagter et al. 1992

Conventional Dentures: Pt. Satisfaction
" Outcome from the pt s point of view is only in part related to
technical aspects of the treatment modality
Vervoorn 1988, Van Waas 1990

" The technical denture quality accounts for less than half of
the total success
Miller, 1960; Devan, 1963

" Denture satisfaction is influenced by various factors,
including denture quality, the denture bearing area available,
the quality of dentist-patient interaction, previous denture
experience and the patient s personality & psychologic well
being. Berg, 1991

Patient satisfaction is primarily based on denture retention

Treatment choices
Implant Supported Implant Assisted Fixed Edentulous Bridge
Overdentures Overdentures

Evidence Based Dentistry
!  Aremandibular dentures retained with dental implants
the best treatment for the edentulous patient (better
than conventional dentures)?

!  Functional
(objective) and perceptual (subjective)
outcomes of treatments
!  Conventional dentures
!  Implant assisted overlay dentures
!  Implant supported overlay dentures
!  Fixed implant supported prostheses

A Randomized Clinical Trial Comparing
Implant Overdentures and Conventional
Dentures in Diabetic Patients

Purpose
!  To determine whether a two implant mandibular overdenture
(IOD) is an effective treatment alternative to a conventional
complete denture (CD) in diabetic edentulous patients
treated with insulin and/or dietary therapy.

Two implants
•  Hader Bar
•  2 clips
•  Experienced denture wearers (15 yrs)
•  Good ridge height (20 mm)

Purpose
!  To determine whether a two implant mandibular overdenture
(IOD) is an effective treatment alternative to a conventional
complete denture (CD) in diabetic edentulous patients
treated with insulin and/or dietary therapy.

Treatment effectiveness was based on improvements in
treatment success rates, masticatory efficiency, food selection
patterns, dietary intake, patient satisfaction, and cost of initial and
maintenance care.

! It is important to not that the patients selected for this study
were excellent candidates for successful outcomes with
conventional complete dentures.
! They were experienced denture wearers and did not present
with advanced resorption of the mandible
! In the following studies not that the patients selected
demonstrated more severe resorption of the mandibular body.
It is therefore not surprising that the outcomes with the implant
retained overlay dentures were more favorable.

"  95 pts., balanced allocation method, including a control group

Inclusion criteria
"  Severely resorbed mandible (<15 mm)
"  Persistent problems in wearing a conventional
denture (>90% of patients dissatisfied at entry)
Results
"  Increasedsatisfaction with IOD (2 implant overdenture)
"  Improved masticatory performance with IOD
Geertman et al, 1994, 1996

Patient Selection and Treatment Planning
Treatment Options Implant assisted
" Fixed Edentulous Bridge overlay denture
" Overdenture
" Implant Supported
" Implant Assisted

Fixed edentulous bridge
Implant supported overlay denture (Fixed hybrid prosthesis)

Which is the best option from a functional perspective?

Implant Assisted Overdentures vs
Implant Supported Overdentures
"  95 pts., balanced allocation method, including a control
group

Results
" The differences with respect to satisfaction, complaints &
subjective chewing ability were not significant.

" No significant difference in chewing ability were noted
between the implant assisted and implant supported
groups Geertman et al, 1994, 1996

Within-subject Comparison Of Mandibular Long-bar and
Hybrid Implant-supported Prostheses: Evaluation Of
Masticatory Function. Tang et al. J Dent Res 1999

Conclusion: No change in function with increased implant support,
but some perceptual changes are reported

Within-subject Comparisons of Implant-supported
Mandibular Prostheses: Choice of Prostheses
Feine et al. J Dent Res 1994

! 
! 
! 
!

Summary of Clinical Outcome Data

!  The primary factor in impaired mastication is tooth loss, which will continue
to be a problem and require prosthetic restoration for the immediate future

!  Neither conventional, implant-assisted or implant-supported mandibular
dentures restore masticatory function to dentate levels.

!  Most patients with reasonable denture bearing surfaces can function
effectively with conventional complete dentures.

!  Little well-controlled evidence exist to support a functional benefit of increased
implant support.


!  Mostpatients with reasonable denture bearing
surfaces can function effectively with conventional
complete dentures.

!  Thereare only limited advantages of one type of
implant treatment over the other for the general
population.
!  The
two implant assisted overlay denture will improve
mastication efficiency in patients with severe resorption and
compromised mandibular denture bearing surfaces.


!  The two implant assisted overdenture will improve mastication
efficiency in patients with severe resorption and compromised
mandibular denture bearing surfaces.

!  There is no difference in implant success rates between tissue
bar clip retention systems and O ring type attachments
without splinting.

!  Most bone loss around implants used with this application take
place the first year. Thereafter, bone levels appear to stabilize.

!  There is no evidence to indicate that the bone loss around
implants is affected by the type of implant assisted attachment
systems used.

Indications for Implant Supported
Overlay Denture

!  Replacement for a fixed prosthesis as age and dexterity make
it difficult to properly manipulate hygiene aids
!  Patients with exposure of the inferior alveolar nerve

Fixed vs Removable
Dictated by:
! Estheticdemands
! Psychological demands
! Need for hygiene access
! Oralcompliance
! Quality of the soft tissues

! Cost

Fixed vs Removable
Esthetics
Some patients require the presence of a properly
contoured and extended denture flange in order to
establish proper lip contours.

Fixed vs Removable
Esthetics
Note the poor facial contours because of lack of
support for the lower lip in this patient who was
fitted with a fixed hybrid prosthesis.

Fixed vs Removable
Need for hygiene access
" Quality of soft tissues surrounding the implants

When implants emerge through poorly keratinized
unattached mucosa removable overlay dentures are
recommended because oral hygiene access is easier.

Fixed vs Removable
Amount of Keratinized Attached Mucosa

!  Both these patients have little or no attached keratinized
mucosa
! Oral hygiene procedures are much easier to perform when the
implants are surrounded by keratinized attached mucosa.
! Creating a zone of attached keratinized tissues anteriorly would
be beneficial regardless of whether the patient chose fixed
or removable

Fixed vs Removable

!  Thispatient presented with ample residual keratinized
attached mucosa. Note that almost both of these
implants have well formed gingival cuffs. If the patient
is capable and willing to properly use the hygiene aids,
fixed also would have been a suitable choice.

Fixed vs Removable

!  These implants emerge through poorly keratinized unattached mucosa.
Previously the patient had been fitted with a fixed edentulous bridge.
Hygiene measures were difficult to perform because of tissue sensitivity.
A removable overlay denture was eventually fabricated. The enhanced
hygiene access allowed by tissue bars design permitted the patient to
maintain healthy peri-implant soft tissues.

Fixed vs Removable
Oral Compliance

!  It is difficult to manipulate the hygiene aids used in patients
with fixed edentulous bridges. If the patient has impaired vision
or impaired motor skills, removable overlay dentures are
recommended.

Fixed vs Removable
Oral Hygiene

!  Oral hygiene must be maintained meticulously. Otherwise
chronic peri-implant gingival infections develop which can
result in considerable morbidity and may even lead to loss of
the implants.

Hypertrophy of peri-implant tissues

Secondary to a combination of:
!  Plague
!  Poor quality peri-implant tissues

Implants in the Edentulous Mandible
Issues of concern
"  Severe resorption
•  Buccal-lingual dimension most important. Less than 5-6 mm requires
bone augmentation
" Lack of attached keratinized tissue
•  Hygiene compromised when the implants are surrounded by poorly
keratinized unattached mucosa
•  Palatal grafts are favored over skin grafts
" Lack of interocclusal space
•  Limits design choices
•  Compromises prosthodontic procedures
•  Commonly encountered when a patient still retains residual dentition in
either the maxilla or mandible
•  Seen in some recently edentulated patients

Severe Resorption
Anatomic Limitations
Severely resorbed mandibular body
a)Vertical height – less than 7 mm
b)Buccal lingual dimension - less
than 5 mm

Mandibles that are smaller than the above are at risk for
fracture during or immediately after implant placement
and should be augmented with a bone graft.

Severe Resorption

Mandibles that are smaller than the above
are at risk for fracture during or immediately
after implant placement and should be
augmented with a bone graft.

Courtesy Dr. H Davis

Severe Resorption
Mandibular Fractures
The mandible fractured through the left posterior implant
site two weeks following implant placement.

It was reduced and repaired as
shown and healing progressed
normally. An implant assisted
overlay denture was later
fabricated and used successfully
by the patient.

Severe Resorption
Mandibular fractures
!  The use of 5mm diameter implant
was a poor choice for this patient
!  Nothing was to be gained from the
use of a wide diameter implant in
a patient scheduled to receive an
implant assisted overlay denture
!  The appropriate choice would
have been an implant 3.75 mm in
diameter
This patient illustrates the consequences of
poor communication between the surgeon
and the referring dentist and a lack of
understanding of by the surgeon of the
primary means of support provided implant
assisted overlay dentures.

Lack of Keratinized Attached Tissue
"  Palatal grafts are preferred over skin grafts
"  They are best performed at second stage implant
surgery

Lack of Keratinized Attached Tissue
A palatal graft was used to establish a zone of keratinized
attached tissue around these implants. The procedure was
performed at the time of implant uncovering. A surgical stent,
secured to the implants with gold screws, held the graft in
position during the healing period.

Lack of interocclusal space
"  Recently edentulated patients
"  Patients to be fitted with an immediate denture followed by an implant
supported fixed edentulous bridge
"  Patients with supereruption of anterior teeth prior to extraction

! Note the supereruption of the mandibular teeth.
! When these teeth are removed an aggressive alveolectomy needs to be
performed prior to placement of implants.
! Implants should be placed combatable with the plane of occlusion.

Cost Advantage
The most bang for the buck
for edentulous patients is
obtained with a two implant
assisted overlay denture. The
edentulous maxilla is restored
with a conventional complete
denture.

Advantages:
a)  Predictability – Implant
failure rates for this
application are virtually
zero
b)  Patient acceptance is very
favorable
c)  Cost effective
d)  Simplicity

Types of attachment systems
!  Bar clip (tissue bar)
!  Hader
!  Dolder Bar clip

!  Individual attachments
!  “O” ring O Ring
!  Individual attachments
!  ERA
!  Locator Locator

!  Magnetic attachments
Magnetic

!  Mini-implants

Mini-implants

Individual attachments and O Rings (ball type)
Advantages
"  Favorable stress distribution patterns (ball type only)
minimize the risk of implant loss secondary to implant
overload
"  Simple to use
"  Less initial cost than a tissue bar

Note: Implants must parallel to one another

Disadvantages
!  Less retention and stability
!  Implants must be parallel or constant insertion and removal
accelerates attachment fatigue and wear
!  Higher profiles may prevent proper positioning of the lower anterior
teeth and predispose to fracture of the overlying acrylic resin.
!  Misaligned implants difficult to overcome and require custom abutments
!  More maintenance required which leads to higher costs (Walton, 2003)

Tissue bars
Advantages
!  Better support anteriorly
!  Less attachment fatigue
!  Less maintenance cost
!  Easier to accommodate divergent implants or a labially
inclined implant
Disadvantages
!  Higherinitial cost
!  More complex prosthodontic procedures

Tissue bars vs individual attachments
We favor bar clip type attachments. Why?
!  Lower maintenance costs (Walton, 2003; Stoker et al,
2007)
!  Less attachment fatigue leads to better long term
retention
!  Can easily accommodate diverging or labially inclined
implants
!  Anterior support is provided with the bar extension
when the implants are placed to far posteriorly or
when the arch is severely tapered.
!  Since the implants are splinted together there is less
chance of implant overload.

O ring (ball) and individual attachments
!  Two types
!  “O” ring type
! They permit a pure rotation

!  Individualattachments
such as the “ERA” or
“Locator type”
! Moe retentive but do not
permit a pure rotation

Types of O ring (ball) attachments
Ball types are preferred because they allow a pure rotation
around the patrix portion of the attachments.
Straumann gold clip
Straumann 2.25 mm (matrix)
retentive anchor (patrix)

Straumann titanium
matrix with stainless
steel spring (matrix)

Steri-Oss ball patrix

Steri-Oss rubber
matrix

! Less wear of patrix portion of the attachments
! Less stress on the implants with less chance of mechanical
or implant failures.

O Rings (ball type)
Plastic or rubber attachment matrix is preferred
over the metal type. Why?
! Less wear of matrix and patrix.
Brånemark 2.25 Brånemark gold
mm ball patrix matrix

Southern 3.25 mm Southern plastic
ball patrix matrix

Individual attachments
! Locators
! Single tooth ERA
!  Initial retention at delivery is good with these two attachments a
but after a couple of hundred insertions and removals
attachment fatigue significantly decreases the retention
!  If the implants are divergent and not parallel to one another as
in these patients, excessive wear during functional rotation,
insertion and removal will lead to excessive wear of the
abutment portion of the attachment.

Individual attachments
Locators
!  When occlusal forces are applied unilaterally in the posterior
region these forces are concentrated around the implant on that
side.
!  In patients with poor support the risk of implant overload
becomes greater.
!  This phenomenon increases the risk of implant overload as
seen in this photo-elastic study assessing locator attachments.

Prosthodontic Procedures
Requirements
! Implants must be placed anteriorly (20 mm apart
from center to center)
! Implants must be parallel to one another
! Impressions must be border molded to extend the
denture to cover the retromolar pad and the
buccal shelf

Support provided by:
!  Implantsanteriorly
!  Buccal shelf and retromolar pad posteriorly

Properly extended denture Under-extended denture

Therefore impressions must be border molded

Individual attachments – O Rings (ball type)
Upper denture mounted with facebow transfer jig.

The dentures are
completed and delivered
in the usual manner.

Lower denture with
remount cast

Delivery and Post-Insertion Care
!  Pressure indicating paste
!  Disclosing wax
!  Clinical remount
!  24 and 48 hour followup
!  Leave dentures out at night
!  Educate the patient

Clinical Remount

Occlusion is refined in centric, and to permit unencumbered
sliding functional tracking between working, balancing and
protrusive.

Clinical Remount

Why is bilateral balanced occlusion so important
when a patient is fitted with an implant assisted
overdenture?
!  Thesetypes of dentures move during function. The
more the dentures move and rock during function the
more rapidly the attachments wear.

Design of the surgical template
! The implants must be parallel to one another so it is
imperative that the surgeon use a surgical template (drill guide)
while inserting the implants.

! The mandibular denture is duplicated
and altered as shown to create the
surgical template.
Courtesy Dr. S. Esposito

Surgical Templates
Implants must be positioned anteriorly –
approximately 20 mm from center to center

Connecting the matrix portion of the
attachment to the denture base

When the implants are osseointegrated they can
be either related to the denture by one of two
methods
!  Directly intra-orally
!  By means of a reline impression.

Pick up attachments directly

!  Healing abutment is removed and a depth gauge
used to select an attachment – abutment (patrix) of
proper length.
!  The abutment must project 1-2 mm above the level
of the tissue.


!  Secure the abutments (the patrix portion of the attachment), to
the implant fixtures
!  Tighten to 20 Newton Cm but no more.
Why?
!  These attachment systems are subject to wear and periodically need to
be replaced. If they are tightened to an excessive degree the screw may
become swedged to the abutment6 and it may not be possible to
remove them.


!  Secure O rings as shown
to the abutments in order to
block out the undercuts.
!  Secure the metal housing
of the matrix portion to the
abutment
!  In some situations wax may
need to be added.


!  In
this instance the abutment projected far
above the tissue levels. Wax was added
beneath the washier to insure all undercuts
have been effectively blocked out.


!  Using PIP or disclosing wax as
an indicator, room is created in
the denture base for the metal
housing of the matrix portion of
the attachment.
!  Pressure indicating paste is
used to ensure that the denture
is properly seated before the
attachments are picked up.


!  Separating medium is applied
the denture base adjacent to
where the metal housing will
be positioned
!  Resin is applied to the metal
housing and the denture base.


!  Thedenture is seated and the resin
allowed to polymerize.


Attachment

!  Resin flash is removed with a sharp instrument
!  There should no contact between the acrylic resin and the
peri-implant tissues.
!  The processing attachments are replaced by the plastic
attachments of desired retention


! Attachment systems come in varying degrees of retention as indicated by
the color. However, studies indicate after the initial period of use,
attachment fatigue occurs and little difference in retention is noted between
attachments of different colors.

! Some clinicians recommend that at delivery the denture be inserted and
removed 15-20 times so the patient has a realistic view of the retention after
a few weeks of wear.

Impression Method
A reline impression can be used to secure the
female portion of the O ring to the denture base.

Retentive
Anchor Analog

Final Rubber Base Impression with Laboratory
Retentive Anchor Analogs Positioned in Impression.

O ring retained overlay dentures
Completed Denture

! Relined Denture deflasked with analogs and acrylic flash still
present.
! Completed Denture with the female portion imbedded within
the denture base.

Complications
Individual and ball type attachments

!  Wear, attachment breakage and
fatigue
!  Diverging implants and labially
positioned implants
!  Poor oral hygiene
!  Tissue hypertrophy
!  Rocking of the denture

Complications
Individual attachments and O Rings (ball
type)

Wear
!  Note the wear (as indicated by the shiny
surfaces) associated with these
“Locator” type attachments. When
implants are divergent (not parallel to
one another) wear and loss of retention
is accelerated when individual
attachments are used (Al-Ghafli et al,
New attachment- Worn attachment-
2009; Evtimovska et al, 2009)) abutment abutment

Complications
Individual attachments – the Locator type

!  Note the significant wear on the anterior
portion of the Locator attachments
!  This is caused by the movement of the
denture when occlusal forces are applied
posteriorly.
!  The Locator attachment does not
permit as free a rotation as the O ring
type and as a result will wear more rapidly
than other attachments.
!  It is best used for implant supported type
tissue bars where there is no movement
of the overdenture during function.

Complications
Delrin matrix

!  Note the wear (as indicated by the shiny surfaces) associated with these
“Locator” type attachments. When implants are divergent (not parallel to one
another) wear and loss of retention is accelerated when individual
attachments are used (Al-Ghafli et al, 2009; Evtimovska et al, 2009). Locator
type attachments are particularly prone to wear.

!  Why does the “Locator” wear so rapidly when used to retain
implant assisted overdentures?
!  The plastic matrix attachment is made of “Delrin” a very hard plastic
!  The “Locator” type attachment does not permit a free rotation like “O” ring type
designs.

Complications

Locator type attachments are best used with milled tissue
bars that are designed to be implant supported. Why?
!  There is no movement of the overdenture during function since this
is an implant supported design
!  The “Locator” attachments have a low profile and permit the proper
positioning of the denture teeth.
!  The “Locator” attachments have excellent retention.

Complications
type)
!  When implants are divergent or an implant is positioned or
inclined to the labial it will not be possible to properly position
the denture teeth without excessively thinning the acrylic resin
over the attachment.
!  This will predispose the resin to crazing and fracture
!  Solution
!  Tissue bars - the tissue bar can be tapered anteriorly to
accommodate the denture teeth as seen in this example.

Complications
type)

!  Attachment fatigue
!  Withina very short period of use, retention values
are reduced by up to 50% and then stabilize.
!  Attachment fracture
!  Fracture
of the plastic portion of the attachment, as
shown here, is relatively rare

Complications
Poor oral hygiene and food impaction
!  Predisposes to peri-implantitis
!  Damages the attachments
!  Accelerates wear of the abutment and the attachments

Dental plague

Note accumulation of
plague and food debris

Complications

Tissue irritation and hypertrophy – Secondary to:
!  The acrylic resin in contact with the peri-implant
mucosa
!  Poor oral hygiene
!  Wearing the dentures at night

Complications

Tapered arch

Tapered arch

Patient complaint: Anterior–posterior rocking of the
denture due to lack of anterior support
!  Reason: Implants placed to far posteriorly
!  This is a common problem in tapered arches when
individual attachments are used

Complications

Solution
!  Tissue bar with an anterior cantilever

Note: This solution is less than ideal biomechanically but fortunately the
anterior forces are only ¼ to 1/5 of those delivered posteriorly during chewing
and so risk of implant overload and mechanical failures is very low.

Immediate loading
Overdentures using Individual attachments
or O Rings (ball type)

This procedure is easily accomplished but
should not be used (contra-indicated)
!  Implant
loss rates the first year after placement
approach 20% (Kronstrom et al, 2010)

If you permit the implants to osseointegrate before employing
the attachments the implant success rates are close to 100%.

Tissue Bars

Tissue Bar Design
We favor two implants splinted together with a Hader bar,
with the bar aligned parallel to the axis of rotation. The denture
rotates around the bar when the patient generates a posterior
occlusal load. With this design the implant loss rates after
loading are virtually zero.

The anterior, or incisal forces are borne by the implants while
the posterior occlusal loads or born by the primary denture
support areas (retromolar pad and the buccal shelf).

Tissue Bar Design
Hader bar design
In cross section the “Hader” bar is a complete circle and
permits the denture to rotate around it.
Hader clip rotates
Clip around the bar
housing

Plastic burnout pattern
for the Hader bar

This is an implant assisted type tissue bar design. When posterior occlusal forces are
applied, the denture rotates around the bar. As a result the posterior occlusal forces
are supported by the buccal shelf and retromolar pad. The anterior forces are
supported by the tissue bar. Hence support is shared between the implants and the
denture bearing surfaces. The bar provides retention and stability for the denture.

Implant position – Hader Bar Design

!  In most patients there are five implant positions available in
the anterior mandible anterior to the mental foramen.
!  We prefer to place implants in the cuspid positions or between
the cuspid and the 1st premolar so that the bar can be
configured parallel to the axis of rotation with little or no
cantilever extension.

These implants are too posterior and too far apart. Since the
denture is only connected to the bar via the clips no clinical
advantage is gained.

The tissue bar fabricated
will have an excessive
anterior cantilever.

Implant position
These implants are in ideal position

The implants are wide enough apart to accept two
Hader clips and an anterior cantilever is not
necessary to fit the tissue bar within the contours of
the denture.

Implant position and angulation
!  These implants are in ideal position. They are at least 20 mm
apart but are far enough anteriorly minimize the anterior
cantilever.
!  They exit through the crest of the ridge.
!  Implants must not emerge through the mobile tissues of the
floor of the mouth. The tissue mobility at this site is such that
the peri-implant tissues will be in a perpetual state of irritation.
!  Angulation is less important than when O ring or similar
type attachments are employed for retention.

Implant position
These implants are a bit too close together even
though room is available for the use two Hader clips.

The wider the Hader segment of the bar, the
better the stability of the denture. Ideally, the
Hader segment should be at least 14 mm.

These implants are too close together. Room
is available for only one Hader clip.

Stability of the overlay denture was not ideal
and retention was also suboptimal

Soft tissue problems following 2nd stage
surgery: Solutions:
Peri-implant tissues excessively thick lacking
keratinized mucosa
"  Repeat submucosal resection
"  Free palatal grafts can be used to replace poorly keratinized tissue with
keratinized mucosa
Graft

1 week postop

1 month postop

Impressions
Types of impression copings
!  Transfer type (closed tray)
!  Bordermolded impression with
corrected impression made with
silicone impression material.
!  Pickup type (open tray)
!  Impressioncopings are linked
permitting the use of a corrected
impression made with polysulfide.

Preliminary Impressions
Preliminary impressions are made with transfer type copings
and stock trays.

After the impression is made abutment
analogues or fixture analogues, as
appropriate, are connected to the transfer
impression copings and positioned in the
impression.

Preliminary Impressions
Preliminary impressions are made with transfer type copings
and stock trays.
Removed the transfer
copings from the mouth
and attach them to a
fixture analogue.

The impression analogue with
the fixture analogue attached is
inserted into the impression and
the preliminary cast is made.

Preliminary Cast

!  Thetransfer impression copings are removed
from the preliminary cast in preparation for
making the master impression tray.

Pickup type ( open tray)
Impression copings are linked permitting the use
of a corrected impression made with polysulfide.

Impression copings are secured to
the fixture analogues imbedded in
the preliminary cast


The impression copings are linked together with floss and
Duralay*. They are sectioned and then reconnected intra-
orally with Duralay or cyanoacrylate.


!  A separating disc is used to separate
each of the impression copings from
one another.
!  They are labeled.
!  They will be reunited with pattern
resin in mouth just prior to making
the final master impression.


The copings, undercuts and relief
areas are blocked out with wax.


The master impression tray is
completed in the usual manner. The
guide pins must project 1-2 mm
above the level of the tray.

Master Impression
Linked pickup type impression copings
Clinical steps:
!  The impression tray is border molded in the usual
fashion
!  The pick up impression copings are screwed onto
the fixtures and linked together with pattern resin
!  The impression is corrected in the usual manner

Completed border
molded impression

Master Impression
Linked pickup type impression copings
A light body polysulfide
impression material can be used
to refine the border molded
impression when linked
imbedded type copings are used.

Appropriate analogues are now
secured to the pickup type
impression copings that are
imbedded in the master impression.
The impression is boxed and
poured in the usual fashion.

Impressions with transfer type copings

!  When transfer copings for master impressions they must be
inspected carefully to ensure they are free of imperfections.
!  When transfer copings are used the corrected impression
must made with silicone. Polysulfide is insufficiently
accurate if transfer coping are used.

Pouring the Master Cast

! 

! 

!

Master Cast
The master cast.
The land of the cast
is slightly wider than
normal.

Why?

"   A silicone template with the denture teeth imbedded within
the template will need to be fabricated and this is supported
by the land of the cast .

Record Bases

!  Secure healing abutments of identical lengths
found in the patient, to the master cast.
!  Block out undercuts around the healing
abutments and master cast as needed.

Record Bases

!  Fabricate the record base and wax rims in the usual
manner.
!  The record bases will positively engage the healing
abutments in the patient helping to stabilize the
record base during the making of the centric relation
records.

Facebow Transfer Record

Make the facebow record and secure the maxillary
cast to the articulator.

Maxillo-mandibular records

Make the centric relation
record and mount the
mandibular cast onto the
articulator in the usual
manner

Occlusion - Bilateral Balance

Working position

! 
! 
!

Try-in Appointment
"  Verify the vertical dimension of
occlusion
"  Prove centric relation record
"  Make protrusive record and transfer
to the articulator
"  Address the esthetic concerns of
the patient

Try-in appointment
Prove centric
relation record

With the record in
position the condyles
should be locked in
their fossae.

Try–in Appointment
The protrusive record is made and transferred to the
articulator.

The condylar inclination is
established and recorded
in the patient s chart.

Fabricating the Tissue Bar
A silicone template is made using a silicone putty

Only the anterior teeth need
be recorded in the silicone
template.


The anterior teeth are removed from the record base
and attached to the silicone template. A small amount
of sticky wax will help connect the denture teeth to the
template.

In this example
the tissue bar will
be fabricated with
the use of the
Ucla abutment.

Begin by attaching the Ucla abutment to a fixture analogue with a
long guide pin (screw). Apply a thin layer of of pattern resin to the
Ucla abutment and extend it 2-4 mm onto the guide pin.

Secure the Ucla abutments to the
fixture analogues in the master cast
with an abutment screw.

The silicone template can be repositioned as
necessary when developing the wax pattern
for the tissue bar.

!  The cast is surveyed and a proper path of insertion is
selected
!  The plastic pattern is attached to a specially designed
instrument that in turn is attached to the surveyor.
!  The plastic pattern can then be secured to the Duralay so
as to be compatible with the chosen path of insertion

!  A plastic burnout Hader bar
pattern is cut and shaped to fit
between the two implants
!  The bar should be positioned
beneath the denture teeth so as
. not to displace them or alter the
contours of the denture base

Tissue Bars
Summary of Design Principles
The tissue bar is designed to be implant assisted
!  The denture should rotate freely around the bar when posterior
occlusal forces are delivered
!  To idealize this rotation the bar should be perpendicular to the midline
and parallel to the plane of occlusion

There should be space beneath the bar and the
tissue to ensure appropriate hygiene access
!  If the bar touches the tissue bar bacterial plagues will form on the
undersurface of the bar which will irritate the tissue and ultimately lead
to hypertrophy of these tissues

The portion directly associated with the implants may
need to be tapered anteriorly to allow for proper
placement of denture teeth

Design of the Tissue Bar
Configuration of the bar
"  Parallel to the plane of occlusion
"  Perpendicular to the midline
"  There should be ample space beneath the bar to provide
for proper hygiene access

Occlusal
plane

Midline


"   Parallel to the plane of occlusion
"   Perpendicular to the midline
"   There should be ample space beneath the bar
to provide for proper hygiene access

The left implant is slightly more posterior than desired

However the configuration of the bar remains the same
"  Parallel to the plane of occlusion
"  Perpendicular to the midline
"  There should be ample space beneath the bar to provide for
proper hygiene access

The left anterior implant is more labial than desired

The basic configuration of the bar remains the same
! Parallel to the plane of occlusion
! Perpendicular to the midline
! There should be ample space beneath the bar to provide for proper
hygiene access

However, the tissue bar portion over the left implant is tapered
to accommodate the positioning of the denture teeth.

Fabrication of the Tissue Bar
Tissue bars must be parallel to the plane of
occlusion and perpendicular to the midline.

Note how the labial portion of the bar is tapered over the left
implant bar. This allows for proper positioning of denture teeth.


!  When implants are positioned or inclined
excessively to the labial the area over the
implants can be tapered to allow for proper
positioning if the denture teeth
!  Note the hygiene access below the tissue bar

Completed tissue bar.

Note the hygiene access beneath the bar.

Processing
!  Priorto processing the clip housings are secured
to the bar and the rest of the bar is blocked out
with plaster or stone.

! This will ensure that the denture rotates freely around the tissue
bar when occlusal forces are applied posteriorly during function.

Completed dentures-Delivery Sequence

!  Insert clips into the
denture.
!  Orange clips are more
retentive initially but
after a couple of weeks
of wear retention
becomes the same as
the yellow clips

Completed dentures-Delivery Sequence

!  Ensure that the denture rotates
properly around the tissue bar
as designed
!  Connect the tissue bar to the
implants
!  Two stage tightening procedure –
At delivery and 1-2 weeks later
!  Pip denture bases
!  Use disclosing wax to verify
border extensions
!  Clinical remount and refine the
occlusion

Delivery Sequence
Check to ensure the bar fits properly within
the denture base

Make sure the bar rotates freely within the retentive clips.
This ensures that the overly denture will indeed be implant
assisted rather than implant supported.

Connect the tissue bar to the implants
!  Use gold alloy screws
(Do not use titanium
screws because they
tend to loosen and
have a propensity to
fracture)
!  Torque to no more than
20 Neuton cm. Why?
!  The tissue bars wear
over time and may need
to be removed and
replaced.

Note: Mechanical Torque drivers are notoriously inaccurate

Delivery Sequence
Pressure Indicating Paste (PIP)

Using pressure indicating paste (PIP) to eliminate areas of
excessive tissue displacement or undercut areas that may be
traumatized during insertion and removal of the denture.
The most critical undercuts relative to the path of insertion in an
implant retained denture are generally located anteriorly.

Delivery Sequence
Pressure Indicating Paste (PIP)

The mylohyoid area is always an area of
concern and must be carefully adjusted.

Delivery Sequence
Disclosing wax is used to check the length, thickness
and contour of the denture border
This border slightly This border is of
overextended and proper length but
a little thick excessively thick

Clinical Remount

Using remount casts and
a facebow transfer
record, mount the upper
cast, obtain and new
centric relation record and
mount the lower cast.

Clinical Remount
These are anatomic posterior denture teeth

Equilibrate in centric

Clinical Remount
These are anatomic posterior denture teeth

Balancing position Working position
Equilibrate in working, balancing
and protrusive. Why is this so
important.
!  Excessive rocking and tipping of the
denture will accelerate wear of the
attachments and the tissue bar.

Patient instructions
! Leave dentures out at night
! Hygiene of the tissue bar and the dentures
! Follow every 4-6 months

!  Clips need to changed about every 12-18 months
!  Denture teeth wear out 7-10 years
!  Tissue bars wear out 12-15 years.

Complications
Tissue bars
!  Poor oral hygiene and tissue irritation
!  Wear of the bar
!  Attachment fatigue
!  Fracture of the resin of the denture base
!  Excessive wear of the denture teeth

Complications
Tissue irritation and hypertrophy secondary to poor
oral hygiene
Note that the bar does not touch the tissue. As a result, only
the tissues around the implants have hypertrophied and the
tissues beneath the bar remain healthy.

Complications
Tissue irritation and hypertrophy secondary to poor oral
hygiene
Note that the bar touches the tissue. As a result, the tissues
around the implants and beneath the tissue bar have
hypertrophied.

Complications
Wear of the tissue bar

Tissue bar after
21 years of wear

New tissue bar

Cracking and fracture of the denture base


Reinforce denture base with metal
substructure if resin overlying the tissue
bar is thin.
!  Impression and cast. Bar is represented by a
plastic burn out pattern
!  Wax pattern developed with pattern resin and wax
!  Note that the metal housings are incorporated
with the pattern


Cast framework is incorporated
within the denture base.

Excessive wear of denture teeth

!  Denture teeth wear more rapidly when support is enhanced
with implants.
!  Solution
!  Replace denture teeth as needed (usually every 7-10 years)
!  Gold occlusals

Excessive wear of denture teeth

Gold occlusals - There are disadvantages
!  Highcost
!  Technical challenges

Other designs
Hader - ERA

!  This design is implant assisted but the addition of ERA
attachments to the posterior extension of the bar will improve
retention.
!  Risk:
!  If followup is not maintained and the denture bottoms out on the ERA
attachments cantilever forces are introduced which could lead to
mechanical failures

Other designs
Hader - ERA
Implant fracture cause:
Functional load exceeds load bearing capacity leading to implant
fracture

Magnetic attachments

Advantages
! Simple to use
! Low cost
! Advantageous when implants are divergent
! Ease of insertion for debilitated patients
! Oral hygiene is simple
! No attachment fatigue


Previous generation of magnets were less than ideal
(Aluminum-nickel-cobalt)
! Retention was poor and the source of patient
dissatisfaction
! Corrosion limited their life span (2-3 years)


New generation of magnets (samarium and
neodymium)
! Retention is 4 times as powerful
! Laser welded keepers may eliminate corrosion
! Followup time is limited (1 year, Cerutto et al, 2010)
! Clinicians should be cautious before employing this
method until there is longer followup

Mini-Implants

Courtesy E. LaBarre

!  Originally
designed to retain transitional
(temporary) prostheses

Mini-Implants

Courtesy E. LaBarre

!  Patient presents with mobile, periodontally
compromised canine teeth.
!  The canines are removed and the existing
removable partial denture is adapted to serve as a
transitional prosthesis.

Mini-Implants

Courtesy E. LaBarre

!  When the canines are removed the mini-implants are
placed
!  The matrix portion of the attachment is incorporated
within the denture to retain the transitional prosthesis

Mini-Implants

Courtesy E. LaBarre

!  The rubber O rings are incorporated within the metal
housing
!  The housing is secured to the implants
!  The housings are incorporated within the denture base
with a chairside pick up procedure

Mini-Implants

Courtesy E. LaBarre

!  Existingremovable partial denture has been
altered and can be used as a temporary
overdenture.

Mini-Implants

Courtesy E. LaBarre

!  These implants are not recommended for long
term use for overdentures
!  Failure rates in the edentulous mandible are
unacceptably high (10% at two years followup;
Krenmair et al, 2003)

Single implant placed in the midline
Overdenture retained with an O ring type of attachment

!  Several authors have suggested this approach in order to
reduce treatment times and component costs
!  The implant is placed on the midline
!  Patient satisfaction appears to be equivalent to the 2 implant
retained overdenture (Walton et al, 2009)
!  Some clinicians have reported a high risk of the acrylic resin
fractures overlying the single implant (Harder et al, 2001).

Treatment of the
Severely Resorbed Mandible

Issues
!  Exposure of the inferior
alveolar nerve (arrows)
!  Pathologic fracture of the
mandible

Treatment of the
Exposure of the inferior alveolar nerve

If the inferior alveolar nerve is exposed and
the mandible is not at risk of fracture an
implant supported prosthesis is
recommended.
! Two options
! Implant
supported
overdentures

! Fixed prostheses

Definitions
Implant assisted prosthesis
The forces of occlusion are
shared between the implants and
the denture bearing surfaces.
Always removable overdentures.

Implant supported prosthesis
All the forces of occlusion are
borne by the implants. Can be
either fixed prostheses or
removable overdentures.

Biomechanical requirements
Implant supported prostheses
Implant number and arrangement

Anterior – Posterior Spread

If an implant supported prosthesis is
planned, 4-5 implants are required with
at least 1 cm of A-P spread.

Indications for Implant Supported
Overdenture

!  Replacement for fixed as patients age and experience
difficulty manipulating hygiene aids
!  Patients with exposure of the inferior alveolar nerve

Biomechanical requirements
Minimum of 4 implants
Minimum of 1 cm of Anterior Poster A-P) spread

Design Considerations
!  The tissue bar requires more bulk between the implants
because of the increased forces delivered.
!  Hygiene access between the implants and beneath the bar
is required
!  We prefer Hader attachments because of their low profile

!  Bite force of patients with implant supported prostheses is
greater
!  Therefore it may be advisable to provide metal reinforcement
particularly if interocclusal space is compromised

Implant Supported Overlay Dentures

! Anatomic posterior teeth
! Bilateral balanced occlusion

Treatment of the
Exposure of the inferior alveolar nerve
!  Fixed hybrid prosthesis
!  In these patients the cantilever extension must be 4 mm
above the level of the tissue. Why?

4 mm

Deposition of new bone on top of the nerve.

Treatment of the severely resorbed mandible

! Implants are placed if there is sufficient bone for
placement of implants 7 mm in length and 3.75
mm in diameter.

! A fixed hybrid prosthesis was fabricated for the patient

! In some patients there is a significant increase in bone
mass of the mandibular body posterior to the implants


!  Notethe significant increase in bone over
the inferior alveolar nerve 8 years
following delivery of the prosthesis.

Note the significant increase in
bone over the inferior alveolar
nerve in another patient 10 years
following delivery of the
prosthesis.


Treatment of the

Role of bone grafting
!  To prevent pathologic fracture of the mandible

!  If there is insufficient bone volume available to place
implants into the anterior region of the mandible bone
grafting followed by implant placement is recommended.

Placement of implants will prevent resorption of the bone graft

Treatment of the severely resorbed
mandible preop
Reconstruction of the
mandible with bone grafts
Many methods have been used
!  Rib grafts
3 mths
!  Iliac crest grafts
!  Visor osteotomy

Regardless of the method used
unless implants are placed, the 5 yrs
grafts resorb within a few years
when conventional dentures are
worn by the patient. This result
is typical.



If implants are placed and put into
function, the graft does not resorb.

Treatment of the

Preferred method
!  Particulatemarrow with
HA particles
!  The marrow provides
the osteogenic
potential and the HA
Courtesy Dr. H Davis provides a scaffold

Treatment of the

!  Another patient with severe
resorption whose mandible
was reconstructed prior to
placement of implant.

!  A fixed hybrid prosthesis
was fabricated for this
Courtesy Dr. H Davis patient.

The 4 implant assisted overlay denture

!  Four implants splinted together
with a implant assisted overlay
denture.
!  In this design the Hader
segment anteriorly serves as the
axis of rotation. The resilient
ERA attachments posteriorly
allow the prosthesis to rotate
around the Hader segment when
posterior occlusal forces are
applied.

Inadequate A-P spread for fixed

We only recommend this approach when there is
inadequate A-P spread or when the implant sites are
dramatically compromised.
!  For example: Patients treated with cancero-cidal levels of
radiation
!  When there is insufficient A-P spread to fabricate an
implant supported prosthesis

Note the minimal A-P spread in this
case. Therefore the tissue bar
design is implant assisted.


Completed tissue bar with
Hader and ERA type
attachments.


Tissue bar is secured to the
implants with gold alloy screws an
tightened to no more than 20 N/cm.


Completed prosthesis.

Note: the support for the
prosthesis is shared between
the implants in the anterior
region and the retromolar pad
and buccal shelf in the posterior
region. Therefore the master
impression was border molded.


Completed and inserted prosthesis.


Inserted prosthesis

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Edentulous Mandible - Overlay Oentures

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