Biomehanics of dental implants and factors affecting it.

1. Biomechanics of dental implants
By
Mohamed Mahmoud Abdul-Monem
Assistant lecturer
Dental Biomaterials Department
Faculty of Dentistry
Alexandria University

3. Dental Implants

4. Osseointegration
• Functional ankylosis
(bone adherence)",
where new bone is laid
down directly on the
implant surface and
the implant
exhibits mechanical
stability (also known
as primary stability )

5. 0sseointegration

6. Importance of studying the
biomechanics of dental implants
• The possibility of stress-generated implant
failures has created an interest in mechanical
and biomechanical studies of oral implant
systems.

7. Failures of dental implants
• Failures can be split into
early and late failures.
• Early failures occur
during the healing and
remodelling period.
• Late failures occur after
that healing period,
namely under loading

8. • The etiological factors of the implant failure
can be pathological (under-) or overload
and/or bacterial infection
• Implants are more “rigid” than teeth and
consequently are more prone to failure.
• Teeth have mechanoreceptors to tune occlusal
forces via the central nervous system .

10. Biomechanics
• Biomechanics can be defined as the
application of engineering mechanics (statics,
dynamics, strength of materials and stress
analysis) to the solution of biological
problems.
• Biomechanics plays a role in dentistry because
the teeth and jaw perform biomechanical
activities during mastication.

11. • Any oral implant will be exposed to intra-oral
forces and moments.
• Mastication induces both vertical and transverse
forces in the dentition
• Transverse forces are mainly created by
horizontal motion of the mandible and the
inclination of the cusps .
• Implants have to deal with axial forces and
bending moments which exert stress gradients in
the implant as well as in the bone.

13. • The force versus moment
by arrangement of class-I
lever.
• To balance the beam, the
product of force lever
arm, must be equal at
both sides of the fulcrum.
• The product of force and
length of the lever arm is
called the bending
moment.

14. Measuring biting forces

15. Specific biomechanical considerations
1.Implant inclination
• The maximum
compressive stresses,
generated in an
osseointegrated
implant, increase as the
inclination of the
implant towards the
load direction increases

16. 2.Implant preload
• When a screw is
tightened to fix a
prostheses, a tensile force
(preload) is built up in the
stem of the screw.
• The preload should be as
high as possible because
it creates a contact force
between the abutment
and the implant

17. 3. Prothesis material
• The use of an alloy with
a low elastic modulus
for the superstructure
(predicts larger stresses
at the bone-implant
interface on the loading
side than the use of a
rigid alloy for a
superstructure with the
same geometry

18. 4.Implant design
• Increasing the length of an
implant reduces the
transfer of horizontal forces
to the surrounding bone.
• The optimum length for an
endosteal implant would be
in the range of 8–12 mm for
support against the
horizontal components of
occlusal loads, with bone
adaptation at the bone-
implant interface.

19. 5.Quality & Quantity of the
surrounding bone
• As stress concentrations
occur around the neck of
the implants, cortical
bone is required.
• Under lateral loading the
stress levels in cancellous
bone surrounding the
neck are so high that it is
likely to cause fatigue
failure and therefore
resorption of the
surrounding bone.