differences between natural tooth periodontium and implant bone connection, biomechanics of implants, implant protected occlusion , occlusal principles for single tooth implant prosthetics and implant supported prosthesis on edentulous arch, shortened arch concept, therapeutic occlusion

1. Piyali Bhattacharya
Dept of Prosthodontics and Crown
& Bridge
HIDSAR

2. Introduction
• Occlusion specific to implants is termed as
Implant Protective Occlusion. This scheme
reduces the forces at the crestal bone/implant
interface. The basis of this concept is formed
by the biomechanical principles
Occlusal Principles and Considerations for Implants: An Overview , Journal of Academy of
Dental Education , Vol 1 (2)| July–December 2014|

3. Five concepts important for an ideal occlusion had
been described by Dawson (1974):
1. Stable stops on all the teeth when the condyles are in
the most superior posterior position (Centric Relation)
2. An anterior guidance that is in harmony with the border
movements of the envelope of function
3. Disclusion of all the posterior teeth on the balancing
side.
4. Disclusion of all the posterior teeth in protrusive
movements
5. Non-interference of all posterior teeth on the working
side with either the lateral anterior guidance or the
border movements of the condyles.
Occlusal Principles and Considerations for Implants: An Overview , Journal of Academy of
Dental Education , Vol 1 (2)| July–December 2014|

4. LOADING ON TEETH VERSUS IMPLANTS
Natural tooth Implant
Connection PDL fibres Osseointegration or ankylosis
Proprioception Periodontal
mechanoceptors
Osseoperception
Tactile sensitivity high low
Axial mobility 25-100 micron 3-5 micron
Movement
phases
Two phases-
Primary: non linear and
complex
Secondary: linear and
elastic
One phase-linear and elastic
Movement
patterns
Primary: Immediate
Secondary: Gradual
Gradual
Fulcrum to lateral
force
Apical third of the root Crestal bone

5. Natural tooth Implant
Load bearing
characteristics
Shock absorbing function and
stress distribution
Stress concentration at
crestal bone
Signs of overloading Thickening of PDL , Fremitus,
wear facets, mobility ,
pain
Screw loosening, veneer
fracture, crestal bone
loss,
Implant failure
Misch CE. Occlusal considerations for implant-supported prostheses: Implant-protected
occlusion. Pp 874-912. Dental Implant Prosthetics (2nd ed), Misch CE. 2015. Mosby, Int.

6. 14 considerations for following the IPO scheme
that should be judiciously implemented before restoration -
1. Elimination of premature occlusal contacts
• Premature contacts are defined as occlusal contacts that
divert the mandible from a normal path of closure;
interfere with normal smooth gliding mandibular
movement; and/or deflect the position of the condyle,
teeth, or prosthesis
• Prior to the evaluation of occlusion on implant
reconstruction, the occlusion should be evaluated and
all occlusal prematurities should be eliminated during
maximum intercuspation and centric relation.
Verma, et al., Principles of occlusion in implant dentistry, Journal of the International Clinical
Dental Research Organization | Supplement 1 | Vol 7 | 2015

7. • Excessive lateral loads arising from premature contact
may cause bone loss and implant failure.
• While restoring an implant, a <25 µm articulating paper is
used , the patient occludes in centric relation, the
implant prosthesis barely makes contact which the rest of
the teeth exhibit greater contact initially.
• The occlusal contact should remain axial over the implant
body and may be of similar intensity on the implant
crown and adjacent teeth when under greater bite force.
• The harmonization under light occlusal loads is followed
by adjustment under heavy occlusal load.
Verma, et al., Principles of occlusion in implant dentistry, Journal of the International Clinical
Dental Research Organization | Supplement 1 | Vol 7 | 2015

8. 2. Provision of adequate surface area to sustain load
transmitted to the prosthesis
• Increased load can be compensated by increasing the
implant width; reducing crown height; ridge
augmentation if necessary; increasing the number of
implants; or splinting the prosthesis

9. 3. Controlling the occlusal table width
• The wider the occlusal table, the greater the force
developed to penetrate a bolus of food. a restoration
mimicking the occlusal anatomy of natural teeth often
results in offset load (increased stress), increased risk of
porcelain fracture, and difficulties in home care (due to
horizontal buccolingual offset/cantilever).

10. 4. Mutually protected articulation
• During centric occlusion the anterior teeth have only light
contact and, are protected by the posterior teeth, during
excursion the posterior teeth are protected by the
anterior guidance
• The rationale of mutually protected occlusion is that the
forces are distributed to segments of the jaws with an
overall decrease in force magnitudes.

11. The steeper the anterior guidance, the greater are the
anticipated forces on anterior implants. In case of a single
tooth implant replacing a canine, no occlusal contact is
recommended on the implant crown during excursion to the
opposite side.

12. 5. Implant body orientation and influence of load
direction
• Anisotropy refers to the character of bone whereby the
mechanical properties depend on the direction in which
the bone is loaded.
• The greater the angle of the
load, the greater is the shear
component of the load. The
cortical bone is the strongest
and most able to withstand
compressive forces. Its ability to
withstand tensile and shear forces
is 30% and 65% less, respectively.
Misch CE. Occlusal considerations for implant-supported prostheses: Implant-protected
occlusion. Pp 874-912. Dental Implant Prosthetics (2nd ed), Misch CE. 2015. Mosby, Int.

13. • The increase in the shear component of stresses
is by almost three times, which predisposes the
bone to increased crestal bone loss and impairs
successful bone growth.
• The implant body should
be placed perpendicular to
the occlusal plane and along
the primary occlusal contact.

14. • A force at a 30-degree angle decreases the bone strength
limit by 10% under compression and by 25% under
tension
• whenever lateral/
angled loads cannot
be eliminated, a
reduction in force
magnitude or
additional surface area
of the implant surface is
indicated to reduce the
risk of bone loss or of
implant component
fracture.

15. Prosthetic Angled Loads
An angled implant body or an
angled load on the implant crown
increases the amount of crestal
stresses on the implant system,
transforms a greater percentage of
the force to shear force, and
reduces bone, porcelain, and
cement strength.

16. Solution to Angled Loads
A reduction in the force magnitude additional surface area
of implant support is indicated
A. surgically:
1.Additional implant next to most angled implant
2.Increased diameter of the angled implant
3.Select implant design with greatest surface area
B. Restoratively:
1. Splinting implants together
2. Reducing occlusal load on angled implants
3. Eliminating all lateral or horizontal forces on angled
implants
Misch CE. Occlusal considerations for implant-supported prostheses: Implant-protected
occlusion. Pp 874-912. Dental Implant Prosthetics (2nd ed), Misch CE. 2015. Mosby, Int.

17. 6. Crown cusp angle
• the angle of force to the implant body may be influenced by
cusp inclination, which in turn will increase crestal bone
stress. The occlusal contact over an implant crown should,
therefore, ideally be on a flat surface perpendicular to the
implant body.
• This positioning is accomplished by increasing the width of the
central groove to 2-3 mm in posterior implant crowns, which
are positioned over the center of the implant abutment.

18. • Cantilevers are class-1
levers, which increase the
amount of stress on
implants.
• Twice the load applied at
the cantilever will act on
the abutment farthest from
the cantilever, and the load
on the abutment closest to
cantilever is the sum of the
other two components.
1020
25 lbs 50 lbs
75 lbs
For example, a 100-N force on the cantilever
equals a 200-N tensile or shear force on the
most distal abutment and a 300-N
Compressive force on the abutment
(the fulcrum) next to the lever.
7. Cantilevers and IPO

19. • Because cement and screws are weaker to tensile loads,
the implant abutment farthest from the cantilever often
becomes unretained, resulting in the fulcrum
abutment’s bearing the entire load. Because the
implant is more rigid than a tooth, it acts as a fulcrum
with higher force transfer.
• As a consequence, crestal bone loss, fracture, and
implant failure are often imminent after the distal
abutment becomes no longer connected to the
prosthesis.
• The greater the length of the cantilever, the greater the
mechanical advantage and the greater the loads on the
implants.

20. • The shorter the distance between the implants, the
greater the mechanical advantage and the greater the
force on the implant system.
• The goal of IPO relative to cantilevers is to reduce the
force on the pontics of the lever region compared with
that over and between the implant abutments.
• the occlusal contact force may be reduced on the
cantilevered portion of the prosthesis to reduce the
amount of force that is magnified by the cantilever.
• No lateral load is applied to the cantilever portion of the
prosthesis whether it is in the posterior or anterior
region.

21. 8. Crown height and IPO
• Crown height does not magnify the stress to the implant
system when the force is applied in the long axis of the
implant body.
• An increased crown height acts as a vertical cantilever, a
force magnifier when any lateral load, angled force, or
cantilever load is applied
15 mm Crown
Height
100 N
Angled load
E.g. A 100-N load at a 12-degree
angle increases the lateral or
shear force component by 20.79
N. A crown height of 15 mm
increases the 20.79-N force to a
311.85–N-mm moment force.
100 N Axial load

22. • If a load perpendicular to the curves of Wilson
and Spee is applied to an angled implant body,
the increase in load is not magnified by the
crown height.
• The angled implant will increase the force.
Hence, the angle of load to the occlusal surface
is more important to control than the angle of
the implant body position.

23. • A buccal or lingual cantilever in
the posterior regions is called an
offset load, and the same
principles of force magnification
from class 1 levers apply. The
greater the offset, the greater
the load to the implant system.
• The ideal occlusal contact is over
the implant body which leads to
the axial loading of implants.
• A posterior implant is hence
placed under the central fossa of
the implant crown
9. Occlusal contact position

24. • A marginal ridge contact is also a cantilever load, as the
marginal ridge may also be several millimeters away from
the implant body. The moment of force on the marginal
ridge may contribute to forces that increase abutment
screw loosening.
• Thus, the ideal primary occlusal contact should reside
within the diameter of the implant within the central
fossa. The secondary occlusal contact should remain
within 1 mm of the periphery of the implants to decrease
the moment loads.
• The marginal ridge contact is not an offset load when
located between implants splinted to one another.

25. • Wider root form implants can accept a broader range of
vertical occlusal contacts while still transmitting lesser
forces at the permucosal site under offset loads.
Narrower implant bodies are more vulnerable to
occlusal table width and offset loads.
• As posterior teeth are out of the esthetic zone, the
posterior implant crown should have a reduced occlusal
width compared with a natural tooth.
• A wide occlusal table favors offset contacts during
mastication or parafunction.

26. 10. Implant crown contour
• The narrower occlusal contour of an implant crown
reduces the risk of porcelain fracture. Also, The
narrower posterior occlusal table facilitates daily
sulcular home care.
• Thus, a narrow occlusal table combined with a
reduced buccal contour (in the posterior mandible)
and a reduced lingual contour (in the posterior
maxilla) facilitates daily care, improves axial loading
and decreases the risk of porcelain fracture.

27. • The posterior mandible
resorbs lingually as the
bone resorbs from division
A to B. As a result,
endosteal implants are
also more lingual than
their natural tooth
predecessors.
• The division C–h and D
mandibular ridge shifts
to the buccal compared
with the maxillary arch.
Endosteal implants typically
cannot be inserted because
the available bone above
the mandibular nerve is
inadequate for endosteal
implants
Mandibular crown contour

28. • The lingual contour of the mandibular implant crown
is similar to a natural tooth permitting a horizontal
overjet to exist and push the tongue out of the way
during occlusal contacts (just as natural teeth).
• In the posterior mandible, as the implant diameter
decreases, the buccal cusp contour is reduced which
decreases the offset length of cantilever load.

29. Maxillary Posterior Crowns
• In the esthetic zone (high lip position during smiling),
the buccal contour of the maxillary implant crown is
similar to a natural tooth.
• When maxillary posterior implants are in the esthetic
zone, they are positioned more facial than the center of
the ridge.
• The ideal functional position for the maxillary posterior
implant is under the central fossa when the cervical
region is not in the esthetic zone. Hence, the lingual
cusp is cantilevered from the implant similar to the
buccal cusp of the posterior mandible. Therefore, the
reduced lingual contour reduces the offset load to the
lingual

30. 11. Design of the prosthesis should favor the weakest arch
• Usually the maxilla is the weaker of the two arches,
predominantly due to less dense bone.
• To follow the weaker component theory, when cantilevered
pontics are in both arches, they should ideally oppose each
other.
• posterior cantilevers in the maxillary arch are less indicated
than in the mandible. When maxillary posterior implants
support cantilevered anterior teeth and mandibular anterior
implants support cantilevered posterior teeth, the occlusal
scheme cannot minimize forces on both.
• In this scenario, the weaker component is usually the anterior
maxilla, and reduced force in the region would be
appropriate.

31. Summary by Bone Volume
Division A bone

32. • Maxillary natural tooth vs mandibular implant-supported
prosthesis in division A bone-
• Maxillary lingual cusp is the primary
contacting cusp.
• Central fossa of implant crown is
broadened by 2-3 mm to receive the
contacting cusp of opposing tooth.
• The lingual cusp of the mandibular
implant crown should be out of
contact to eliminate offset load.
• Mandibular buccal cusps are
reduced to prevent offset load and
cheek bite

33. • Mandibular buccal cusp is the
primary contacting cusp
• Central fossa of implant crown is
broadened by 2-3 mm to receive
the contacting cusp of opposing
tooth
• The lingual cusp of the
mandibular implant crown
should be out of contact to
eliminate offset load.
• Maxillary buccal cusp maintains esthetics
• Maxillary implant-supported prosthesis vs mandibular
natural tooth in division A bone

34. Maxillary implant-supported prosthesis vs mandibular
implant-supported prosthesis in division a bone
• Favour the weaker arch when
axial loading is not possible
• Mandibular buccal cusp is the
primary contacting cusp
• Maxillary buccal cusp maintains
esthetics
• Central fossa of implant crown
is broadened by 2-3 mm to
receive the contacting cusp of
opposing tooth
• Lingual cusp of mandibular crown is maintained and lingual
cusp of maxilla is reduced to prevent offset load

35. Maxillary implant-supported prosthesis
vs mandibular natural tooth in division
B C and D bone, might require cross-
arch relation of teeth

36. • Maxillary lingual overjet
prevents tongue overbite
• Mandibular buccal overjet
prevents cheek bite
• Reduced width of maxillary
buccal cusp
• Primary occlual contact over
central fossa over implant
body
Verma, et al.: Occlusion in implantology, Journal of the International Clinical Dental Research
Organization | Supplement 1 | Vol 7 | 2015

37. 12. Parafunctional activity
• Naert et al. reported that overloading from
parafunctional habits such as clenching or bruxism
seemed to be the most probable cause of implant failure
and marginal bone loss.
• According to them, shorter cantilevers, proper location of
the fixtures along the arch, a maximum fixture length,
and night-guard protection should be prerequisites to
avoid parafunctional habits or the overloading of
implants in these patients.
Falk H, Laurell L, Lundgren D. Occlusal interferences and cantilever joint stress in implant-
supported prostheses occluding with complete dentures. Int J Oral Maxillofac Implants
1990;5:70-7.

38. 13.Timing of loading
• Implant loading can be either delayed (submerged),
progressive bone loading or immediate bone loading.
• Progressive bone loading is specifically indicated for less
dense bones. Progressive bone loading allows a
“development time” for load-bearing bone and allows
bone adaptability to loading via the gradual increase in
loading.
• The concept is based on incorporating time intervals of
3-6 months, avoiding chewing with a soft diet, then
progressing to harder food, gradually intensifying the
occlusal contacts during prosthesis fabrication
,prosthesis design, and occlusal materials (from resin to
metal to porcelain) for poor bone quality conditions

39. 14. Occlusal guidelines for different clinical situations
Group function or mutually
protected occlusion with
shallow anterior guidance is
recommended when opposing
natural dentition or a full-arch
fixed prosthesis.
In case of a full-arch fixed
prosthesis, if the opposing
arch is a complete denture,
balanced occlusion is
recommended.

40. • In case of overdentures, bilateral
balanced occlusion. In case of
severely resorbed ridges,
monoplane occlusion should be
used.
• If the posterior arch is
rehabilitated with a fixed
prosthesis, Where necessary, the
posterior occlusion must be
placed in crossbite
• Occlusal concept when
rehabilitating the edentulous
mandible with oral implants have
been suggested by Quirynen M et
al
B L

41. • In case of the fully edentulous maxilla, whether the
mandibular rehabilitation is done on an overdenture
supported on two implants or on a mucosal-implant
supported overdenture (four implants with a bar
attachment), a balanced occlusal scheme
(bilateral/lingualized/monoplane) is recommended.
• Where a Kennedy class I partially edentulous condition is
present in the maxillary arch and mandibular mucosa
implant supported (four implants with a bar attachment) or
an implant-supported prosthesis is planned for the
mandibular arch, balanced occlusion is recommended.
• Kennedy’s class I in maxillary arch that has been restored
with fixed denture prosthesis (FDP) or with implants, and
a mandibular implant-supported prosthesis is advised, it
is recommended to follow group function or mutually
protected occlusion.

42. Modern Concept In Implant Occlusion
The current criteria for a healthy or physiologic occlusion
as developed by Mohl et al. and Ash and Ramfjord reflect
this shift:
(a) Absence of pathologic manifestations
(b) Satisfactory function
(c) Variability in form and function
(d) Adaptive capacity to changing situations
Fernandes and Chitre: An alternative to management of the partially dentate patient- The SDA
Concept, The Journal of Indian Prosthodontic Society | September 2008 | Vol 8 | Issue 3

43. • The shortened dental arch (SDA) concept, first discussed
internationally by the Dutch prosthodontist Professor
Käyser in 1981-
• shortened dental arches comprising anterior and
premolar teeth in general fulfill the requirements of a
functional dentition
• In the original Brånemark implant treatment, a
moderate SDA concept was applied-
• In spite of the lack of complete molar support, excellent
long-term functional outcome has been demonstrated
• subjects with extreme SDA may exhibit functional
problems
Gunnar E. Carlsson, Dental occlusion: modern concepts and their application in implant
prosthodontics, Odontology (2009) 97:8–17

44. • How many teeth are required cannot be
answered in general but must be evaluated
individually with respect to the wide variation in
occlusal morphology and individual adaptability
present in the population.
• Comparisons of two options for treatment of
SDA, a removable partial denture and small fixed
dental prostheses, have demonstrated several
advantages for the fixed prostheses in spite of the
fact that they did not provide molar support. The
patients liked them better than the removable
denture,

45. • It has also been found that removable partial
dentures do not provide better chewing comfort
and stability of occlusion or prevent or cure
temporomandibular disease (TMD) problems.
• In a unilateral SDA, where a removable partial
denture is admittedly difficult to fabricate and use,
an implant restoration would ideally be the
treatment of choice

46. Therapeutic occlusion
• A therapeutic occlusion has been defined as one
modified by various therapeutic measures so that it
falls within the parameters of a physiological
occlusion.
• Some general guidelines for a therapeutic
occlusion-
• Acceptable vertical facial height after treatment
• Acceptable interocclusal distance with the
mandible at rest

47. • Stable jaw relationship with bilateral contact after
relaxed closure leading into maximal intercuspation as
well as after retruded closure
• Well-distributed contacts in maximal intercuspation,
providing axially directed forces
• Multidirectional freedom of contact movements
radiating from maximal intercuspation
• No disturbing or harmful intermaxillary contacts during
lateral or protrusive excursions
• No soft tissue impingement during occlusal contact

48. Conclusion
• By application of biomechanical principles such as
reducing the cantilever length, passive fitting of
prostheses, narrowing the buccolingual/ mesiodistal
dimensions of the prosthesis, reducing cusp inclination,
eliminating excursive contacts, and centering occlusal
contacts, these complications can be prevented.
• Implant occlusion be adjusted periodically and re-
evaluated to prevent them from developing potential
overloading clinical sequelae, thus providing implant
longevity.
Occlusal Principles and Considerations for Implants: An Overview , Journal of Academy of
Dental Education, Vol 1 (2)| July–December 2014|

49. References
1. Occlusal Principles and Considerations for Implants: An Overview ,
Journal of Academy of Dental Education , Vol 1 (2)| July–
December 2014
2. Misch CE. Occlusal considerations for implant-supported
prostheses: Implant-protected occlusion. Pp 874-912. Dental
Implant Prosthetics (2nd ed), Misch CE. 2015. Mosby, Int.
3. Verma, et al., Principles of occlusion in implant dentistry, Journal
of the International Clinical Dental Research Organization |
Supplement 1 | Vol 7 | 2015
4. Gunnar E. Carlsson, Dental occlusion: modern concepts and their
application in implant prosthodontics, Odontology (2009) 97:8–17
5. Fernandes and Chitre: An alternative to management of the
partially dentate patient- The SDA Concept, The Journal of Indian
Prosthodontic Society | September 2008 | Vol 8 | Issue 3