Implant occlusion and failures./ stomatology and dentistry

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Contents
•Introduction
•Definition of implant failure
•Signs and Symptoms
•Criteria for successful Implants
•Failing and Failed Implants
•Peri implantitis
•Classification of implant failures
•Factors affecting Implant Failures
a. surgical factors
b. host factors
c. implant factors
d. prosthetic factors

• Force Delivery and Failure Mechanism
- Moment arm
- Fatigue Failure
• Basic Considerations for Occlusion for Implants
• Review of Occlusal Schemes
• Factors Affecting Selection of Occlusal Scheme
• Prescribed Occlusion
a)Edentulous Situations
b)Partially Edentulous situations
• Important Guidelines to Follow
• Conclusion
• References

INTRODUCTIONINTRODUCTION
• Branemark definedBranemark defined
osseointegration asosseointegration as
“the direct structural“the direct structural
and functionaland functional
connection betweenconnection between
ordered living boneordered living bone
and the surface of aand the surface of a
load carrying implantload carrying implant

Implant failure
Definition:An implant failure may be defined as the
first instance at which the performance of the implant,
measured in some quantitative way falls below a
specified acceptable level.
Or can be defined as an implant that has a hopeless
prognosis.

Signs and symptoms of implant failure
1) Horizontal mobility beyond 0.5mm or any clinically observed vertical movement under
<500g force
2) rapid progressive bone loss regardless of the stress reduction and peri implant therapy
3) Pain during function or on percussion
4) Dull sound on percussion
5) Continued exudation inspite of surgical attempts at correction
6) Generalized radiolucency around an implant
7) >1/2 of the surrounding bone is lost
8) SLEEPERS -Implants inserted in poor position making them useless for prosthetic support
9) Pocket depth of 5mm and increasing
10) Bleeding on probing(BOP) Index of 2 or abovewww.indiandentalacademy.com

Failing and failed implants
Definition- Failure
process is in early
stages and is reversible
Clinical features-
• Progessive Marginal
Bone
loss(Saucerization)
• absence of mobility
• peri implant infection
(peri implantitis
Failure process has
reached the
irreversible state
Marginal bone loss
reaching the
apical 1/3 of implant
mobility
Thin peri fixtural
radiolucency
Failing Implant Failed Implant

Peri Implantitis
Def-American Academy of Periodontology
Defines Peri implantitis as “progressive Peri
implant bone loss in conjunction with a soft
tissue inflammatory lesion.”
Causes
Bacterial Accumulation
Overloading or
Combination

Clinical Signs-
Progression of pocket
depth
Radiographically
detectable bone loss
Inflammatory Reaction
of Mucosa

Classification of Implant Failures
1.According to Branemark et al
• Loss of bone anchorage
- Mucoperiosteal perforation
- Surgical trauma
• Gingival problems
- Proliferative gingivitis
- Fistula formation
• Mechanical complications
- Fixture fractures
- Fracture of prostheses, gold screws, abutment screws

2. According to Misch
Surgical failure inability to place the abutment at the time
of surgery
Osseous healing failure period from implant placement to
abutment connection,is related to
healing ability of bone
Early loading failure the first year the implant serves as a
prosthetic abutment
Intermediate implant failure time period after the 1st yr of loading upto
following 5yrs of function
Late implant failure after the implant and prosthesis have been
loaded for >5yrs but <10yrs.
Long term failure failures after 10 yrs.

Complications/factors leading to implant
failures
. Surgical factorsSurgical factors (early failures)(early failures)
Stage I surgery
1) Overheating of bone - necrosis,osteomyelitis
2) Lack of primary stability - bone loss
3) Infection
4) Lack of osseointegration
5) Poor placement or angulation, slips, eccentric drills
6) Damage to vital structures
7) Implant fracture
8) Inadequate no. of implants

Stage II surgery
• Loose abutment
• poor fixtures
• early loading by
prosthesis
• poor abutments

Prosthetic factors
(late failures)
1.Improper design, shape, contours
2.Poor fit of prostheses
3.Occlusal forces
4.Inaccurate framework
5.Cantilever extension
6.Framework fracture, prosthesis fracture
7.Functional problems eg speech

Implant related factors
1.Screw design:
conical screws - loosen
flat head screws - better
2.Implant body design:
smooth cylinder implant - shear force at implant-bone interface
threaded implant - can transform and change the direction of
force through thread geometry

a) Shape of thread Standard v
Thread
Square
Buttress thread

b) Thread pitch:
smaller the pitch more
will be the surface
c) Thread depth:
increases surface area
3. Implant length : increases surface
area4. Implant width : increases surface area

Host factors
• Patient dissatisfaction with the result.
• Inadequate patient follow-up
• Failure to maintain hygiene leading to periodontal breakdown
• Parafunctional habits
• Systemic health( medical complications)
• Medications- alter tissue metabolism and repair
• Social habits like smoking, stress,alcohol abuse affect wound healing
• Poor bone quality and quantity - avascular bone,bone density,
type of bone,etc.

Force delivery and failure mechanisms
Moment loads (torque or torsional loads):
is defined as a vector,the magnitude of which equals the product
of force magnitude and the perpendicular distance from the
implant
to the line of action of force.

Possible rotations
A total of six rotations may develop about three clinical co ordinate axes.

Clinical Moment Arms
1.OCCLUSAL HEIGHT MOMENT ARM
2.CANTILEVER LENGTH MOMENT ARM
3.OCCLUSAL WIDTH MOMENT ARM

Fatigue failure
Four factors influence fatigue:
1. Biomaterial
2. Geometry of the structure -Twice thicker material have sixteen times
more fatigue resistance .
3. Force magnitude
4. Number of loading cycles.

BASIC CONSIDERATION
– OCCLUSION CONCEPTS AND PHILOSOPHIES ARE NOT
BASED UPON SCINTIFIC RESEARCH AND EVIDENCE.
– THE CONCEPT THAT HAVE BEEN POPULAR FOR THE
RESTORATION OF NATURAL TEETH HAVE BEEN JUSTIFIED
BY PURELY EMPIRICAL METHODS AND HAVE HELD UP
WELL TO THE TEST OF TIME. FOR IMPLANTS THE SAME
CONCEPTS HAVE BEEN USED WHICH SERVE AS A GUIDE
LINES TO ACHIEVE OPTIMUM OCCLUSION .
IMPLANT OCCLUSION

--TRULSSON AND GUNNE IN 1998TRULSSON AND GUNNE IN 1998 : CONCLUDED THAT THE RANGE: CONCLUDED THAT THE RANGE
OF “FOOD- HOLDING” FORCES FOR THE PATIENTS WITH IMPLANTSOF “FOOD- HOLDING” FORCES FOR THE PATIENTS WITH IMPLANTS
IS SIGNIFICANTLY HIGHER THAN THOSE FOR PATIENTS WITHIS SIGNIFICANTLY HIGHER THAN THOSE FOR PATIENTS WITH
NATURAL TEETH.NATURAL TEETH.
THE KEY FEATURES OF AN OCCLUSION FOR IMPLANTS SHOULDTHE KEY FEATURES OF AN OCCLUSION FOR IMPLANTS SHOULD
DEPEND UPON THE TYPE OF PROSTHESIS GIVEN- SINGLE TOOTHDEPEND UPON THE TYPE OF PROSTHESIS GIVEN- SINGLE TOOTH
IMPLANTS/FPD/CD/OVERDENTURE ,AS THE REQUIREMENT ANDIMPLANTS/FPD/CD/OVERDENTURE ,AS THE REQUIREMENT AND
BIOMECHANICS OF EACH ARE DIFFERENT.BIOMECHANICS OF EACH ARE DIFFERENT.

Flocken (1984) stated that to help alleviate the potential impact forces , the teeth should
contact
simultaneously when the mandible closes into maximum intercuspation.Natural teeth can
function
effectively from this position.
Lundgren , Laurell (1984) suggested the need to minimize horizontal forces created by
premature
contacts or steep cusps.
Albrektsson,et al., (1986) emphasized the need to distribute the load mainly over the areas
supported directly by fixtures.
Jemt (1986) described that when Osseo integrated implants are used in short span FPDs
and single
tooth replacements , the occlusion should be distributed in maximum intercuspation and
all cusp
interferences should be eliminated in eccentric positions.
Lucia (1987) advocated the application of gnathological principles in development of
occlusion
in implants.
Review of occlusal scheme

Misch (1991) developed IPO ‘Implant protective occlusion’ for implant supported
restorations.
IPO - Medial positioned lingualized occlusion
is based on :
- Narrow occlusal table.
- occlusal table width similar to width of implant body.
- Increasing surface area.
- Design of occlusion in favour of weakest arch.
- Decreasing force of occlusal contacts.
- Eliminating or reducing all shear loads to implant to bone interface.
- Posterior disocclusion by anterior components.
- Initial contacts on only natural teeth and later on multiple contacts on both
teeth and implants.
Norton (1995) recommended an ideal occlusal scheme for fixed implant supported
prostheses :
- A centric occlusion ‘cusp to central fossa’ contact which is light.
- An ideal anterior guidance : that is canine-guidance or group function; no posterior
interferences.
- Axial loading of the implants.

Factors affecting choice of occlusal
scheme1.Arch form:
- Curve arch is favorable for less stresses
- Influences no. of implants to be placed
- Opposing arch form affects occlusion
2.Interarch distance and jaw relations :
- May prevent development of particular
occlusal scheme
- May force to adapt a particular scheme
- Affects biomechanical aspects
3. Orientation of the occlusal plane :
- Arch in which is implant is placed becomes the dominant
arch and opposing edentulous arch becomes weaker arch.
- plane should favor weaker arch.www.indiandentalacademy.com

4. Abnormal mandibular movements
5. Bone support and bone mechanics :
Sullivan (1990) stated that the final form of
restoration should be development
maintaining progressive loading.
Good bone support - occlusal contacts can be increased.
6. Occlusal material :
- affects the transmission of forces.
- affects the maintenance of occlusal contacts.
Acrylic has higher wear rate, so if acrylic is to be used then heavy occlusal
contacts can’t be given. www.indiandentalacademy.com

6. Zarb (1985): stated that acrylic teeth have shock absorbing effect and can be
modified for use very easily.
They should be used to decrease overloading of implants.
However selection of occlusal material depends upon :
- Opposing occlusion.
- Remaining dentition.
- Arch to be restored.

7. Attachment to natural teeth
•Hobo in 1986 recommended a non rigid attachment and a
Key and Key way type of attachment between teeth and
implant.
•Lundgren in 1986 recommended the use of Semi –
precision attachment which detaches the teeth from the
implant prosthesis allowing a tooth to move downward.

• The IMZ implant system uses a Intra mobile element [IME] to
act as a shock absorber during function.
It can act as a PDL analogue.
However, Gracia in 1998 reported intrusion of the natural
supporting teeth.
•Misch: stated that biomechanical concern and difference in
Support should be understood and applied before attaching
natural teeth to implants.
He advocates initial occlusal contacts on the natural teeth.(Thin
articulating paper of 25 m should be used for this.
Once the equilibrium with a light bite force is completed, a
heavier CR occlusal force is applied to have contacts on teeth as
well as implant also, thus harmonizing the occlusal forces.

Heavy bite force is used because it depresses the natural teeth positioning
them close to infra occluded or depressed implant position and equally
sharing the load.
Only possible advantage is additional support to convert
cantilever design to fixed one.
8. Quality of Osseo integration
Its is the ability of implant to bear occlusal load .
It depends upon:
1. Implant length , width, design, surface coatings.
2. Number of implants, position of implants, orientation of implants.

1.Implants opposing implants with cantilevers
Onlight closure
ØMultiple even , simultaneous contact between all opposing
restorations except the distal cantilever unit , where 100 microns
clearance is required .
On firm closure
ØDistal cantilever will remain out of contact .
Prescribed occlusion
Edentulous situations

FIXTURES SUPPORTING OVER
DENTURES.
• BALANCED OCCLUSION
• LINGUALIZED OCCLUSION

FIXTURES SUPPORTED BRIDGES
OPPOSING COMPLETE DENTURES.
• BALANCED / LINGUALIZED
OCCLUSION.

FIXTURES SUPPORTED OVERDENTURES
OPPOSING NATURAL TEETH WITH
BRIDGE
 MUTUALLY PROTECTED OCCLUSION
CANINE GUIDED
OR
ANTERIOR GROUP FUNCTION.
 BALANCED OCCLUSION.

PARTIAL EDENTULOUS
CASES
SINGLE TOOTH IMPLANT
 LIGHT LOAD ( INFRA- OCCLUSION BY 30 MICRONS )
UNDER HEAVY CLENCHING .
 AXIAL LOADING
 LIGHT OR NO ECCENTRIC CONTACTS
 NO GUIDANCE ON SINGLE IMPLANT

FIXTURES SUPPORTED BIDGE
AGAINST NATURAL DENTITION.
• CANINE PROTECTED / GROUP FUNCTION –
LATERAL GUIDANCE.

•M P O ( MUTUALLY PROTECTED OCCLUSION )
•ORGANIC OCCLUSION

FIXTURES SUPPORTED BRIDGE HAVING
CANTILEVER EXTENSIONS OPPOSING
COMPLETE DENTURES
• BALANCED OCCLUSION
• NO CONTACT ON CANTILEVER UNITS.

KENNEDY CLASS I
• ANTERIOR GUIDANCE BY NATURAL
TEETH AND POSTERIOR DISCLUSION.
Canine guidance / anterior group function .
• MPO

KENNEDY CLASS II
• CONFIRM TO EXISTING OCCLUSION
WITH 30 MICRONS CLEARANCE AT
FREE END SADDLE
• MPO

KENNEDY CLASS III
WITH INFRA OCCLUSION AT
IMPLANT SITE.
• MPO/ GROUP FUNCTION

KENNEDY CLASS IV
WITH INFRA OCCLUSION OF
IMPLANT.
• ANTERIOR GUIDANCE WHICH
ACHEIVES POSTERIOR DISCLUSION.
• GROUP FUNCTION

IMPORTANT GUIDELINES TO
FOLLOW
• INFRAOCCLUSION UPTO 30 MICRONS OF
IMPLANT SUPPORTED RESTORATION
• NO BALANCING CONTACTS ON CANTILEVERS.
• NO GUIDANCE ON SINGLE IMPLANTS.
• FREEDOM IN CENTRIC.
• OCCLUSAL TABLE DIRECTLY PROPORTIONAL TO
IMPLANT DIAMETER.
• NARROW OCCLUSAL WIDTH.

•IMPLANT LENGTH – CROWN RATIO
ideal – 1:2
acceptable – 1:1 for removable denture.
•AVOIDANCE OF CANTILEVER LENGTH.
maximum 10 and 20 mm is advised.
7 mm is optimum .
•SHALLOW CENTRAL FOSSAE WITH TRIPODAL CUSPAL
CONTACTS.
•NO CONTACT IN LATERAL EXCURSION.
•SLIGHT CONTACT IN CENTRIC OCCLUSION.

Conclusion

The surgeon’s tale
‘The implants were successfully integrated , but failed because
of excess loads.’
or
The Restorative Dentist’s tale
‘The implants were poorly integrated and so failed under normal
masticatory loads.’
either way
The Patient’s tale
‘My implants have failed!’

References
1.Carl.E.Misch : Implant Dentistry, 2nd ed.,pp 609-629,1999
2.Cury P.R.,Sendyk W.R.,Sallum A.W. Factors associated with early and late failure of
osseointegrated implant.Braz J Oral Sci.2003;2
3. Davies S.J.,Gray R.J.M.,Young M.P.J.:Good occlusal practice in the provision of implant
borne prosthes8es.BDJ 2002;192:79-88
4. Esposito M.,Hirsch J.M.,Lekholm U.,Thomsen P. Biological factors contributing to
failures of osseointegrated oral implants.Euro.J.of Oral Sc.1998;106:527-551
5. Hobo, Ichida, Garcia: Osseointegration and Occlusal Rehabilitation,1st ed. pp.239-47,1988
6. Michael D.Wise : Failure in the Restored Dentition:Management and Treatment,1st ed.
pp.489-564,1995
7. Palmer R,Palmer P,Howe L Dental implants: Part 10.Complications and maintenance.
BDJ 1999 ; 187:653-658
8.Vincent Jimenez-Lopez : Implant-supported prostheses:Occlusion,Clinical Cases,and
laboratory procedures, 1st ed.pp. 23-44,1995
9. Weinberg L A Reduction of implant loading using a modified centric occlusal anatomy.
Int J Prosthodont 1998 ; 11:55-69www.indiandentalacademy.com

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