Restoration of posterior quadrants

1. John Beumer III DDS, MS
Robert F. Faulkner, DDS
Kumar C. Shah DDS, MS
Division of Advanced Prosthodontics, UCLA
Restora(on
of
posterior
quadrants
Pa(ent
selec(on,
and
treatment
planning
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2. Table of Contents
Treatment options
– RPD’s
– Fixed dental prostheses
– Endodontic therapy
Implant biomechanics
– Number of implants per unit
– Staggered vs. linear configurations
– Length, implant diameter
– Cantilevers
– Occlusal factors
– Parafunctional activity
– Strategies to avoid biomechanical related problems
Anatomic limitations and the role of preprosthetic surgery
– Grafting
– Distraction osteogenesis
– Socket augmentation and ridge preservation
– Placement of implants into fresh extraction sites

3. Implants vs RPD’s
v Cost
v Mas(ca(on
efficiency
(Kapur
et
al,
1987,
1989.
1991a,
1991b,
1997)
Implants may not always be the best
choice for the patient

4. RPD’s and Implants
Position and lengths
• Implant site most favored – 1st molar position
• Lengths vary but in recent times some clinicians have
reported successful outcomes when using implants as
short as 6 mm in length (Gates et al, 2012).
In
extension
base
RPD’s
(Kennedy
Class
I
and
II)
to
supplement
the
support,
stability
and
reten(on
provided
by
the
exis(ng
den((on.

5. RPD’s and Implants
• Unanticipated implant failures
• Poor quality bone
• Unfavorable biomechanics

6. Endodontics vs Implants
v High level of predictability
v Extraction of the tooth and
replacement with an implant
is based on volume and
integrity of tooth structure
remaining
v Cost advantages to endo plus
restoration
v Esthetics – Retention of bone
and soft tissue

7. Conventional fixed vs implants
o Predictable
when
abutments
in
good
condi(on
(Pietursson
et
al,
2007;
Walton,
2009)
o Cost
effec(ve
o Implants
preferred
when
abutments
are
virgin
or
near
virgin
15 year follow-up

8. Things can go wrong with implants
Biomechanics – Partially Edentulous Patients
! Because of the curve of Spee and the distal angulation of the implants, the
occlusal loads (arrow) are nonaxial.
! Note the bone loss around the implants. Linear configurations in the posterior
region, such as in this patient, are particularly vulnerable to the effects of
nonaxial loading, particularly brachycephalic individuals.
Nonaxial loads and implant overload in posterior
quadrants
Semi-precision attachments
usion of the natural tooth abutment
ears after delivery the patient noticed the premolar
o intrude. Exam revealed that the screw retaining the
ad become loose, hence the rotation of this crown.
Bruxism - Case Report
This is a five year followup x-ray of
a patient with an implant
supported fixed partial denture.
Closer exam revealed
both implants to be
fractured .
The patient was a heavy bruxer.
Six months later he presented
with significant bone loss around
both implants.
Bruxism - Case Report
This is a five year followup x-ray of
a patient with an implant
supported fixed partial denture.
The patient was a heavy bruxer.
Six months later he presented
with significant bone loss around
both implants.
Implant overload
Bone loss
Implant fractures
Peri-implantitis
Impaction of
cement
Implant
loss

9. How can we avoid these complications?
Biomechanics – Partially Edentulous Patients
! Because of the curve of Spee and the distal angulation of the implants, the
occlusal loads (arrow) are nonaxial.
! Note the bone loss around the implants. Linear configurations in the posterior
region, such as in this patient, are particularly vulnerable to the effects of
nonaxial loading, particularly brachycephalic individuals.
Nonaxial loads and implant overload in posterior
quadrants
Semi-precision attachments
usion of the natural tooth abutment
ears after delivery the patient noticed the premolar
o intrude. Exam revealed that the screw retaining the
ad become loose, hence the rotation of this crown.
Bruxism - Case Report
This is a five year followup x-ray of
a patient with an implant
supported fixed partial denture.
Closer exam revealed
both implants to be
fractured .
The patient was a heavy bruxer.
Six months later he presented
with significant bone loss around
both implants.
Bruxism - Case Report
This is a five year followup x-ray of
a patient with an implant
supported fixed partial denture.
The patient was a heavy bruxer.
Six months later he presented
with significant bone loss around
both implants.
Implant overload
Bone loss
Implant fractures
Peri-implantitis
Impaction of
cement
Implant
loss

10. Implant Biomechanics and
Treatment Planning
Why should we be concerned with
implant biomechanics when we develop
a plan of treatment?
Because if we are not, we risk implant
overload and prosthesis failures such
as fracture and screw loosening.
Implant overload can lead to bone loss around
implants and eventually implant failure.

11. Bone
is
a
dynamic
structure.
Excessive
loads
lead
to
a
resorp(ve
remodeling
response
Hoshaw et al (1994) observed a resorptive remodeling of the
bone around implants subjected to excessive axial loads (300N).
Bone loss was observed at the crest around the neck of the
implant and in the zone of bone adjacent to the body of the
implant
Brunski et al, 2000
Recent studies by Myata et al (1998, 2000, 2008) and Nagasawa
et al, (2013) have reconfirmed Hoshaw and Brunski’s original
hypothesis
Is it possible to overload the bone anchoring an
osseointegrated implant?

12. Implant Overload - Basic
Mechanism
v Excessive
occlusal
loads,
off
angle
loads,
bending
moments
v Resul(ng
microdamage
(fractures,
cracks,
and
delamina(ons)
v Resorp(on
remodeling
response
of
bone
is
provoked
v Increased
porosity
of
bone
in
the
interface
zone
secondary
to
remodeling
v Vicious
cycle
of
con(nued
loading,
more
micro-­‐damage,
more
porosity
un(l
failure

13. Implant overload
l Implant
alignment
must
consider
the
curve
of
Spee
and
the
curve
of
Wilson
l In
both
situa(ons
the
implants
will
be
exposed
to
bending
moments
and
predispose
to
implant
overload.
Occlusal force

14. Implant
overload
• In posterior quadrants when implants are aligned in a linear
fashion they should be aligned consistent with the curve of
Spee and the curve of Wilson
Curve of Wilson

15. Implant Biomechanics
What
is
the
load
bearing
capacity
of
osseointegrated
implant
supported
restora(ons?
Is
the
load
carrying
capacity
of
implant
prostheses
influenced
by
the
quality
of
the
bone
sites?
What
factors
control
the
magnitude
of
the
loads
that
are
delivered
through
the
implant
into
the
surrounding
bone?
What
loads
should
implant
borne
restora(ons
be
designed
to
resist?

16.
Karnak The Great Wall Pont
de
Gard
You must over engineer your implant restorations, particularly
when restoring posterior quadrants with linear configurations in
order achieve predictable long term results.
Implant Biomechanics

17. Implant
Biomechanics
LOAD BEARING CAPACITY
1.
Quality
of
bone
site
2.
Quality
of
bone
implant
interface
3.
Implant
microsurfaces
Machined
vs
microrough
vs
nano-­‐enhanced
surfaces
4. Implant
Number and
Arrangement
Linear vs Curvilinear
Length and diameter
Angulation
ANTICIPATED LOAD
(Affected by)
Occlusal factors
Cusp angles
Width of occlusal table
Guidance type
Anterior guidance
Group function
Cantilever forces
Connection to natural
dentition
Size of occlusal table
Cantilevered prostheses
Parafunctional habits
(bruxism)
Brachycephalics

18. Load
bearing
capacity
Implant
number
and
arrangement
• Both
the
number
and
arrangement
of
implants
affect
the
load
carrying
capacity
of
any
par(cular
implant
supported
restora(on.
• Curvilinear
arrangements
withstand
more
load
than
linear
arrangements

19. Load
bearing
capacity
Linear
vs
Curvilinear
o Curvilinear
arrangements
have
the
greatest
load
bearing
capacity.
o Cross
arch
stabiliza(on

20. Load
bearing
capacity
Linear
vs
Curvilinear
v Curvilinear
arrangements
such
as
seen
in
this
pa(ent
are
very
predictable
v This
PFM
fixed
prosthesis
is
12
years
post
inser(on.
Occlusion: Group function
12 year follow-up12 year follow-up

21. Load
bearing
capacity
Linear
vs
Curvilinear
Linear configurations restoring the cuspid region, such as the
patient on the right, are unpredictable, whereas curvilinear implant
arrangements such as shown on the left are very predictable.
Predictable Not predictable

22. Maxilla vs Mandible
Bone quality
v The
size
and
shape
of
the
trabeculae
is
different
in
the
mandible
as
compared
to
the
mandible.
v This
may
be
one
of
the
reasons
why
the
load
carrying
capacity
of
implant
supported
prostheses
restoring
posterior
quadrants
in
the
mandible
appears
to
be
superior
to
those
in
the
maxilla.
Courtesy
Dr.
C.
Stanford

23. Number of Implants per Unit Posterior Maxilla
When
restoring
posterior
quadrants
with
implants
we
are
forced
to
use
linear
arrangements
by
anatomic
necessity.
Therefore
in
most
instances:
*The third implant
dramatically improves the
biomechanics of the
restoration
One
implant
for
each
dental
unit.
At
least
three
where
possible
in
extension
areas.
One dental unit = premolar

24. Number of Implants per Unit Posterior Maxilla
The distal implants failed 30 months after loading in
both these patients because of implant overload.

25. Number of Implants per Unit Posterior Maxilla
o The distal implant failed 30 months after loading in
both these patients because of implant overload.
o The patient was a bruxer

26. Number of Implants per Unit Posterior Maxilla
These implants failed 66 months after
loading because of implant overload.
Group function was used to restore this patient. Result:
Application of excessive lateral forces
Implant failure
Another problem: Cusp angles too steep
and the occlusion was tripodized

27. Number of Implants per Unit
Posterior Maxilla
Space allowed only two implants to be placed in
this patient. However, note anterior guidance.
Design the occlusion to minimize the delivery of nonaxial forces

28. Number of Implants per Unit
Posterior Maxilla
Only two implants were placed.
Note anterior guidance

29. Bone Augmentation – Horizontal Deficiencies
Predictable
Less
occlusal
force
Fixa(on
of
the
grae
is
easy
to
accomplish
The
blood
supply
to
the
grae
is
usually
quite
good

30. Bone Augmentation
Vertical Defects
Less
predictable
Problems:
Tension
on
the
wound
secondary
to
closure
of
(ssue
flaps
Poor
blood
supply
Difficulty
in
achieving
fixa(on
Result:
Relapse
(resorp(on)
rate
is
75%

31. Sinus Augmentation
Advantages
over
onlay
gra7s
Resorp(on
probably
less
than
25%
Challenge
Elevate
the
sinus
membrane
without
perfora(on
Sinus
membrane
Bone graft
Bone of the residual
allveolar ridge

32. Sinus
Augmenta(on
• Implants can be placed simultaneous when there is 4-5
mm over the sinus and primary immobilization of the
implants can be achieved
• Otherwise implant placement delayed for 6-9 months

33. Sinus augmentation
Predictable
(Jensen
et
al,
1997;
Aghaloo
and
Moy,
2007)
Sources
of
grae
material
include
chin,
ramus,
and
iliac
crest
some(mes
mixed
with
bone
subs(tutes.
Complica(ons
Loss
of
grae
material
Blockage
of
the
os(um
Incomplete
eleva(on
of
the
sinus
prevent
normal
sinus
drainage

34. PRE-OP
4M POST-OP
2M POST-OP

35. Sinus augmention
This patient was restored following a sinus lift
and graft. Autogenous chin bone was used.
She is 10 years post treatment and doing well.
Note: Best results achieved when there is 4-5 mm
of normal bone over the sinus before the procedure

36. Sinus augmentation
§ This
pa(ent
was
restored
following
a
bilateral
sinus
lie
and
grae.
§
Freeze
dried
bone
was
used
to
grae
the
lee
maxillary
sinus.
§ The
implants
placed
in
this
grae
failed
18
months
following
delivery
of
the
implant
supported
fixed
par(al
denture.

37. Crestal
Augmenta(on
Augmenta(on
of
ver(cal
defects
in
posterior
mandibular
quadrants
with
free
autogenous
bone
graes
has
been
unpredictable.
Following
surgery
the
relapse
rate
is
about
75%
and
further
bone
loss
is
also
seen
aeer
loading.
Why?
a) Tension
on
the
wound
upon
closure
b) Poor
blood
supply
c) Difficulty
is
achieving
proper
fixa(on
of
the
grae

38. Pterygoid implants
• As an alternative to sinus
augmentation
• Success rates in excess
of 90%
Courtesy Dr. A. Pozzi

39. *Removable Partial Dentures*
Removable partial dentures properly designed and fabricated
provide the patient with masticatory function equivalent to that
obtained with an implant supported fixed partial dentures
(Kapur, et al, 1992) and this service should be offered to the
patient before grafting is considered.

40. Number of Implants per Unit
Posterior Mandible
Two is sufficient for most patients
Why?
v The trabecular bone is more dense
v Cortical layer is thicker

41. Number of Implants per Unit
Posterior Mandible
v There is bone over the nerve for only short implants
v Bone quality is poor
v When restoring four dental units
Three are recommended when:

42. Number of Implants per Unit
Posterior Mandible
Three implants were used to
restore four units in this patient

43. Posterior Mandible – Limiting Factors
v Inferior alveolar nerve(arrow)
v Insufficient bone over the nerve to permit
placement of a 10 mm or longer implant
v Uni-cortical anchorage (arrow)

44. Many patients such as this one, present with moderate
to severe resorption precluding placement of implants
unless the inferior alveolar nerve displaced.
Posterior Mandible – Limiting Factors

45. Displacement of the Inferior Alveolar Nerve
This
procedure
enables
placement
of
implants
of
sufficient
length
with
bicor(cal
anchorage.
Although
the
risk
of
nerve
injury
is
rela(vely
small
the
morbidi(es
associated
with
injury
may
be
severe.
Therefore,
these
issues
must
be
thoroughly
discussed
with
the
pa(ent
before
proceeding
with
the
procedure.

46. Crestal Augmentation
Augmenta(on
of
ver(cal
defects
in
posterior
mandibular
quadrants
with
free
autogenous
bone
graes
(A)
has
been
unpredictable.
Following
surgery
the
relapse
rate
is
about
75%
and
further
bone
loss
is
also
seen
aeer
loading
(B).
Why?
a)
Tension
on
the
wound
upon
closure
b)
Poor
blood
supply
c)
Difficulty
is
achieving
proper
fixa(on
of
the
grae
BA
Presently,
distrac(on
osteogenesis
is
the
only
reasonably
predictable
method
for
enhancing
this
site
ver(cally.

47. Mandibular Onlay Grafting
Patients = 13 Total grafts = 21
• Follow-up: 3 mos – 72 mos Avg. = 26 mos
• Avg. height gained with block graft = 4.21 mm
• Avg. height of graft remaining on f/u = 1.05 mm
• Overall, 75% of initial graft height was lost
• Complication(s)
– 6 of 21 sites demonstrated wound dehiscence
• 28.6% complication rate

48. Distraction Osteogenesis
§ 4-5 mm of bone required over the nerve
§ Distract 1mm per day
§ Relapse rate is 25 %
§ Wait 6 months for consolidation before implant placement

49. Horizontal vs vertical augmentation
Predictable

50. Use of Short Wide Diameter
Implants in the Posterior Mandible
This practice has not been predictable. The short implants are
particularly prone to occlusal overload and bone loss. This is a
2 and 7 year follow-up x-ray of two 6 mm diameter implants.

51. Use
of
Short
Wide
Diameter
Implants
in
the
Posterior
Mandible
The implants failed 15 years after insertion.

52. If implants of adequate length cannot be
used, consider removable partial dentures
Mastication efficiency of distal extension RPD’s is
equivalent to implant supported fixed partial dentures.

53. When in doubt add the 3rd implant in posterior
quadrant cases.
Minimize the length and width of the occlusal
table
Linear
configura(ons
Over engineer your cases

54. Over-engineer your linear quadrant cases
v When in doubt re: the quality of
the implant site bone, history of
parafunction etc., add the third
implant

55. Over-engineer your linear quadrant cases
v Minimize the width of the occlusal surfaces. They should
be no wider than a premolar
Note: The buccal-lingual dimension is excessive
However,
there
is
a
flaw
in
the
design
of
this
case.
What
is
it?

56. Staggered vs linear configuration in
posterior quadrants
This has been studied using a photoelastic model
by Itoh, et al, 2003
Staggered implant configuration
1.5 mm
1.5 mm 1.5 mm
Straight line implant configuration

57. Staggered vs linear configuration
Staggered implant configuration
1.5 mm
1.5 mm 1.5 mm
Straight line implant configuration
Itoh and Caputo, et al 2003
Is
it
biomechanically
more
favorable?
v Yes,
par(cularly
with
specific
chewing
cycles.
Nonlinear
arrangements
resist
lateral
forces
more
effec(vely
v Is
the
improvement
clinically
significant?
This
is
unknown

58. Staggered vs linear configuration
Staggered implant configuration
1.5 mm
1.5 mm 1.5 mm
Straight line implant configuration
Probably not. In the posterior
quadrants you can’t get enough
stagger to make much of a
difference biomechanically. Itoh and Caputo, et al 2003
Is
it
feasible
in
the
posterior
quadrants?

59. Implants in Compromised Sites
Posterior maxilla
Posterior mandible over the
inferior alveolar nerve in partially
edentulous patients
Craniofacial application
Theore(cally
perhaps.
However
we
need
well
designed
clinical
outcome
studies
to
determine
predictability
Can
we
use
shorter
implants?

60. Length and diameter of Implants
v Short implants, such as this 7 mm screw
shaped implant, demonstrate unfavorable
stress distribution patterns as seen in this
study performed with finite element analysis.
Longer implants distribute stresses more
favorably.
v Given the bone anchorage achieved with
modern surfaces, failures are most likely to
occur in the trabecular bone
v Failure rates approach 25% for machine
surface implants 7 mm in length (Wyatt and
Zarb, 1998; Winklet et al, 2000)
Avoid the use of implants less than 10 mm in length
and 4mm in diameter when restoring posterior
quadrants.
Cho et al, 1993

61. • Two year followup data from Moy and Sze,’93
• Note the high failure rates with the 7 mm and
10 mm implants in the posterior maxilla.
Length
and
diameter
of
Implants

62. Implant length vs diameter
Using a photoelastic model,
Caputo et al, 2002 attempted
to determine whether
increasing the diameter of the
implant or increasing the length
of the implant had a significant
impact on stress distribution.
They concluded that:
Does increasing the
diameter compensate for
the lack of sufficient
length?

63. Implant length vs diameter
Lingual
load
Axial
load
Buccal
load
Most equitable load transfer
with axially directed loads.
Under comparable loading
conditions, the stresses
transferred by the wide
diameter implant were only
slightly lower than the same
length narrow implant.
For implants tested,
increased length was more
important than diameter in
stress reduction.
Caputo
et
al,2002

64. Implant length vs width
§ Failure rates of short wide diameter
implants approaches 20%.
2 years 8 years
Cho,In
Ho
et
al,
1992
14 years

65. Implant
length
vs
width
l Over-­‐prepara(on
and/or
over
hea(ng
of
the
osteotomy
site.
This
may
precipitate
early
loss
of
bone,
par(cularly
around
the
neck
of
the
implant.
l Implant
overload.
l Insufficient
trabecular
bone
encasing
the
implant
on
its
buccal
and
lingual
aspect
leading
to
progressive
bone
loss.

66. Ideal Implant Diameter
4-5 mm in diameter
Less than 4 mm the rate of implant
fracture is unacceptably high
Implants 3.75 mm in diameter have a 5-7%
fracture rate
More than 5 mm the higher the
failure rate.
Implants 6 mm in diameter have a 20%
failure rate
Implants 4-5 mm in diameter have a less than
5% failure rate

67. Implant Angulation – Posterior vs Anterior
v Implants in the posterior
quadrants should be placed so
that occlusal loads can be
directed axially in the posterior
quadrants.
v In the anterior region, anatomic
necessity precludes implant placement
perpendicular to the occlusal plane.
v However, the forces used to incise
the bolus are only about ¼ of those
used posteriorly to masticate the
bolus. For this and other reasons
implant overload is rarely seen in
the anterior regions.

68. v Nonaxial loads result in load magnification. Kinni et al
(1987), using photoelastic analysis and Cho et al (1993),
using finite element analysis, demonstrated that nonaxial
loads concentrated potentially clinically significant stresses
around the neck and at the tip of the implant.
Implant angulation
Cho,In
Ho
et
al,
1992

69. Curve of Wilson
Implant
Angula(on
Curve of Wilson Curve of Spee

70. Implant angulation
v Implant
alignment
must
consider
the
curve
of
Spee
and
the
curve
of
Wilson
Nonaxial
loads
and
implant
overload
in
posterior
quadrants

71. Implant
Angula(on
CAC-­‐CAM
technologies
permit:
l Development
of
virtual
diagnos(c
wax-­‐ups
l Surgical
drill
guides
which
permit
controlled
direc(onal
drilling
as
opposed
to
free
hand
drilling

72. Implant
Angula(on
• Controlled directional drilling is preferred
because it results in few errors in implant
angulation and position as opposed to free
hand drilling

73. Implant
Angula(on
• CAD-CAM can also be used to design and mill
custom abutments and prototype restorations

74. Cantilevers and Linear Configurations in
Posterior Quadrants
• They are particularly detrimental and are therefore
contraindicated when using linear configurations to restore
posterior quadrants. They cause subject the implants to
bending, load magnification and overload the bone around
the implant adjacent to the cantilever.
Mesial
and
distal
canClevers

75. They
are
well
tolerated
when
implant
supported
restora(ons
are
used
to
restore
the
edentulous
mandible,
so
long
as:
– The
can(levered
sec(on
is
within
a
reasonable
limit
– The
implants
are
arranged
in
a
reasonable
arc
of
curvature.
– Rigid
frameworks
with
cross
arch
stabiliza(on
are
used
Cantilever forces
Cantilever
section

76. Cantilevers – Implant Overload
• Note the bone loss around the dental implants adjacent
to the cantilever.
Restorations designed in this fashion, especially
in the posterior maxilla, have a poor prognosis.

77. Limit buccal, lingual and cantilevers
The occlusal tables are
excessively wide in this
case. Buccal and lingual
cantilever forces may
lead in selected patients
to:
Prosthesis failures
• Porcelain fractures
• Screw fractures
Implant overload and
bone loss

78. Occlusal Anatomy and Biomechanics
v Narrow occlusal table
Goal: Reduce the buccal - lingual cantilever effect

79. Avoid
buccal
and
lingual
can(levers
The occlusal table must be narrowed
to avoid buccal and lingual cantilevers.
Molars should be no wider than
premolars as shown in these two
examples.

80. Solitary implants restoring single molars –
Cantilever effect
When the food bolus is applied to the marginal ridge (B), the
restoration is easily tipped because the crown is supported by
such a narrow platform.
Result: Cantilever forces lead to screw loosening, implant
fracture and overload the bone anchoring the implant.
BA

81. Fracture
Implant fractured after 30 months of function
Solitary implants restoring single molars
Cantilever effect

82. Single tooth restorations in the molar
region – Cantilever effect
This implant was too short and too narrow to
withstand occlusal loads and bone loss caused by
the resorptive remodeling response led to its loss.
4 mm
diameter
implant
Mesial
canClever

83. Single Tooth Restorations Distal
Extension Defects

84. Distal Extension Defects

85. Restoration of single molar sites - Solutions
In this patient a wide diameter implant was used to
restore the first molar.
Eliminate
the
can(lever
by
using
Wide
diameter
Mul(ple
implants

86. Restoration of single molar sites
Custom abutment Lingual set screw
In
this
pa(ent,
two
4
mm
diameter
implant
were
used
to
restore
the
first
molar.
The
width
of
the
occlusal
table
was
limited
to
the
width
of
the
natural
premolar,
thereby
elimina(ng
any
possible
buccal
or
lingual
can(levers.

87. Restoration of single molar sites
Note:
Hygiene access for proxy brush
Note width of occlusal table

88. Splinted vs Nonsplinted
Pa(ent
presented
with
a
failed
endodon(cally
treated
#30.
This
tooth
was
extracted
and
the
space
restored
with
an
implant.
Several
years
later
the
endodon(c
therapy
on
#29
failed
and
this
too
was
replaced
with
and
implant
restora(on.

89. Splinted
vs
Nonsplinted
• These
implants
were
not
splinted
• Note
the
anterior
group
func(on
• Mandibular
bone
sites
favorable
• Pa(ent
did
not
demonstrate
evidence
of
parafunc(onal
ac(vity
• Long
implants

90. Splinted
vs
Nonsplinted
From a theoretical biomechanical perspective
splinted designs are more favorable than unsplinted
designs, but whether this difference is clinically
significant has yet to be determined with properly
desinged clinical outcome studies.

91. Criteria for splinting
• If the patient shows signs of parafunctional activities.
• If the quality of bone anchoring the implants is questionable (type
IV bone, or if the implants are in grafted sites).
• Misangled implants ie, implants that are not perpindicular to the
plane of occlusion.
• If relatively short implants have been employed (less than 10 mm
in length).
• If the patient presents with or is to be restored with group
function. Linear configurations of implants lack cross arch
stabilization and are less able to resist bending moments
(nonaxial loads) and implant angulations that are not ideal result
in the application of bending moments.
• All maxillary posterior quadrant cases.

92. l When
implants
of
10
in
length
or
longer
are
placed.
l When
the
quality
of
bone
is
good.
l Implants
placed
with
perfect
angula(on
(perpendicular
to
the
plane
of
occlusion)
l Absence
of
parafunc(onal
ac(vity.
Nonsplinted
designs
are
used
when
restoring
posterior
quadrants
only
in
the
mandible
and
under
the
following
circumstances:

93. Connecting Implants to Natural Dentition
How do you minimize cantilever forces?
Semiprecision (nonrigid) vs rigid attachments

94. Connecting Implants to Natural Dentition
Posterior
implant
apached
to
anterior
abutment
Rigid
apachment
Nonrigid
apachment
Nishimura
et
al,
1999
Loads applied in the pontic area

95. Connecting Implants to Natural Dentition
Rigid
vs
non
rigid
apachments
No
difference
as
long
as
the
nonrigid
(semi-­‐precision)
apachments
remain
fully
seated

96. Semi-precision Attachments
Problems
v Intrusion of the natural tooth
leading to:
v Cantilever affect
v Load magnification
v Resorptive remodeling response
v Bone loss (arrows)
Semi-precision
attachment

97. Semi-precision attachments
Intrusion of the natural tooth abutment
• Eleven years after delivery the patient noticed the premolar
began to intrude. Exam revealed that the screw retaining the
molar had become loose, hence the rotation of this crown.

98. Rigid Attachments*
Intrusion is prevented with
rigid attachments
Screw retained tube
lock attachment
*Shared support

99. Rigid Attachments*
Screw
retained
tube
lock
apachment
*Shared support

100. Occlusal Anatomy and Biomechanics
• Narrow occlusal table
• Flat cusp angles
• Lingualize or buccalize

101. Occlusal Anatomy and Biomechanics
v Narrow occlusal table
Goal: Reduce the cantilever effect

102. Parafunctional activity
This
is
a
five
year
followup
x-­‐ray
of
a
pa(ent
with
an
implant
supported
fixed
par(al
denture.
Closer exam revealed
both implants to be
fractured .
The patient was a heavy bruxer.
Six months later he presented
with significant bone loss around
both implants.

103. Parafunctional activity
This patient did well with this
implant supported fixed partial
denture for more than four years
(note 4 year follow-up x-ray).
However, soon thereafter, the
anterior implant fractured, the
bridge was removed and a
trephine used to remove the
implant.

104. Occlusion
Partially edentulous patients when restoring
posterior quadrants with implants
– Anterior guidance
– Anterior group function
– Group function
Courtesy Dr. M. Hamada

105. Implants in the Maxillary Cuspid Region
Mutually Protected Occlusion (Group
Function)
Patient in right working position.
Note lateral guidance is provided
by the premolars and the central
incisor.
Result: Lateral forces
on the implants are
minimized. Courtesy Dr. M. Hamada

106. Anterior (canine) guidance
Space allowed only two implants to be placed in
this patient. However, note anterior guidance.
Design the occlusion to minimize the delivery of nonaxial forces

107. Mutually Protected Occlusion
Only two implants have been placed to restore the corner of the arch in
this patient. (b,c) The implants were inclined towards the labial and
milled customized abutments were used. Note that the minimal height
of the buccal wall of the posterior abutment. As a result retention was
designed to be achieved with lingual set screws as opposed to cement.

108. Mutually Protected Occlusion
(d)
The
finished
prosthesis.
(e)
It
is
adjusted
so
that
contact
during
lateral
excursion
is
provided
by
the
natural
den((on
and
not
the
implants.

109. Anterior Group
function with Centric Only Contact
Note: The cusp
angles are flat
and the occlusal
tables are
narrow
Result: Lateral
forces on the
implants are
minimized

110. Restoring the Cuspids: Mutually Protected
Occlusion (Group Function)
Patient in right and left working position.
Note lateral guidance is provided by the
premolars and the central incisor.
Result: Lateral forces on
the implants are minimized.
Right working Left working

111. Restoring the corner of the arch : Mutually
protected occlusion plus implants
Group function
was used to
distribute lateral
loads as widely as
possible in order
to reduce the risk
of implant
overload

112. Materials for the occlusal surfaces
o Layered porcelains
o Susceptable to fracture
o Milled monolithic zirconia
o Metal occlusal surfaces

113. • Metal
• Ceramic
• Resin
Materials for the occlusal surfaces

114. Strategies to Avoid Implant Complications
Place implants
perpendicular to the
occlusal plane (Note that
the occlusal plane is not
flat – Curve of Wilson,
Curve of Spee)
Posterior quadrants of partially edentulous patients
Place
implants
in
tooth
posi(ons
When in doubt,
always add the third
implant
Avoid use of cantilevers in
linear configurations

115. Strategies to Avoid Implant Complications
Restore anterior
guidance
Posterior
quadrants
of
parCally
edentulous
paCents
If required to attach to
natural dentition, do so with
a rigid attachment system
Control the occlusal factors
(cusp angles, width of the
occlusal table)
Avoid use of
short implants
(less than 10 mm

116. Preservation of bone
and soft tissues following extraction
l Socket
augmenta(on
-­‐
treatment
of
fresh
extrac(on
sockets
with
intact
buccal
and
lingual
bone
walls.
l Ridge
preserva(on
-­‐
treatment
of
fresh
extrac(on
sockets
with
deficient
bone
walls
in
order
to
maintain
ridge
contours.
l Ridge
augmenta(on
-­‐
augmen(ng
edentulous
sites
that
are
insufficient
for
implant
placement.

117. Socket augmentation
Socket
augmenta(on
is
defined
as
treatment
of
fresh
extrac(on
sockets
with
intact
buccal
and
lingual
bone
walls.
v Many methods attempted
v No consensus re: its value
or the best method
Courtesy
Dr.
T.
Han

118. Socket
augmenta(on
v When successful, following healing implants can be
placed in ideal positions with proper angulation
v Many methods attempted
v No consensus re: its value or the best method
Courtesy
Dr.
T.
Han

119. Ridge preservation
Ridge
preserva(on
is
defined
as
treatment
of
fresh
extrac(on
sockets
with
deficient
bone
walls
in
order
to
maintain
ridge
contours.
v Many methods
attempted
v No consensus re:
its value or the
best method
Courtesy
Dr.
D.
Krill

120. Ridge preservation
Ridge
preserva(on
is
defined
as
treatment
of
fresh
extrac(on
sockets
with
deficient
bone
walls
in
order
to
maintain
ridge
contours.
v Problematic in
patient presenting
with active
infection.
Courtesy
Dr.
D.
Krill

121. Ridge augmentation
l Ridge
augmenta(on
is
defined
as
augmen(ng
edentulous
sites
that
are
insufficient
for
implant
placement.
• Appears to the most predictable
Courtesy
Dr.
P.
Moy

122.
Loss of vertical and horizontal bone volume following
extraction can be significant
v 3-4 mm of resorption can occur during the first 6 months post-
extraction (Atwood et al, 1971 and others)
v Probably secondary to expession of specific genes in oral mucosa to
promote wound contraction and closure (Sukotjo et al, 2002;
Suwanwela et al, 2011)
Placement of Implants
into Fresh Extraction Sites

123. Placement
of
Implants
into
Fresh
Extrac(on
Sites
Will placement of an implant impact the process of
resorption?
It appears not. There will still be resorption of the
facial plate of bone even in the presence of an implant
placed immediately upon exstraction
Radiographic finding
of root resorption
Courtesy Dr. TL Chang

124. Implants in fresh extraction sites
Atrauma(c
extrac(on
and
flapless
surgery
l Remember
that
the
vasculature
of
the
labial
plate
associated
with
the
PDL
has
been
significantly
compromised
by
the
extrac(on
l Even
under
the
best
of
circumstances
there
will
be
resorp(on
of
the
facial
plate
of
bone
Courtesy
Dr.
T.
Han

125. Mucosal advancement flaps
• Facilitates hygiene
• The more keratinized tissue the better because over
time the patient slowly loose the attached tissue,
particularly on the buccal side of the mandibular molars

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