1. هو الحکیم

2. Stress Treatment Theorem for Implant Dentistry
Presented by:Dr.Mehrak Amjadi
Supervised by: Dr. Mansour Rismanchian
And Dr.saied Nosouhian
Dental of implantology
Dental implants research center
Isfahan university of mediacal science

3. Caries
Periodontal disease
Endodontic problems
Common complications related
to the natural dentition (Biological)
Caries
Endodontic problems
common complications
for three-unit fixed prostheses
(Biomechanical & Biological)
unretained prosthesis
porcelain fracture
The most common implant-related complications are biomechanical problems that occur after the implant is loaded.

4. Biomechanical problems
Implant overdentures
attachment fracture
removable prosthesis fracture
implant-supported fixed Prostheses
acrylic resin veneer fracture
abutment or prosthetic screw loosening
porcelain fracture
prosthesis metal fracture

5. implant failure
primarily occur within 18 months of initial implant loading
most often in the softest bone types or the shortest implant lengths picture

7. implant complication
most common causes for implant-related complications
are centered around stress
the overall treatment plan should :
assess the greatest force factors in the system
(2) establish mechanisms to protect the overall
implant-bone-prosthetic system.

8. SURGICAL FAILURE reasons for the failure of an implant
integration with the bone :
excessive heat
excessive pressure at the time of implant insertion(tapered screw-type)
- primary causes :
- Micromovement of the implant while the developing interface is established (20 microns)
99% of the time may obtain rigid fixations after surgical placement
The surgical component of
implant failure is often the least risk of implant treatment.

9. EARLY LOADING FAILURE
- Within 6 to 18 months
- cause : excessive stress for the bone-implant interface.
- related to the amount of force and the density of the bone (15% of implant restorations)

10. IMPACT OF OCCLUSAL OVERLOAD ON MECHANICAL COMPONENTS
Screw Loosening
Fatigue Fractures

11. Screw Loosening 6% of implant prostheses Singletooth crowns highest
rate (25%) in early screw designs
Cantilevers also increase
the risk of screw loosening
increase length of the cantilever
Increase the forces

12. Screw Loosening
The height or depth of an antirotational component of the implant body (higher
or deeper the hex height, the less stress)
The platform dimension is more important
than the hex height dimension
Larger-diameter implants, with larger platform dimensions, reduce the forces

13. Fatigue Fractures
if a lower force magnitude repeatedly hits an object, it will still fracture
Prosthesis screw fracture in both
fixed partial and complete fixed prostheses %
Abutment screws are usually larger in
diameter fracture less often %
Metal framework fractures of fixed complete and
overdenture restorations %
Implant body fracture has the least incidence %

14. Uncemented restorations
when chronic loads are applied to the
cement interface
when shear forces are present
(as found with cantilevers)
Cement strengths are weakest in shear loads.

15. MARGINAL BONE LOSS For the one-piece blade
range from loss of marginal bone to complete failure of the implant
For the one-piece blade
implants, was described as a
"saucerization" and occurred after implant loading

16. Loss of crestal Bone
Greater magnitude of bone loss during the first year mm from crestal bone
The initial transosteal bone loss V- or aU-shaped pattern
(described as ditching or saucerization)

17. hypotheses of crestal bone loss

18. hypotheses of crestal bone loss
reflection of the periosteum
Osteotomy
micromovement of the abutment
bacterial invasion
biological width
factors of stress

19. Periosteal Reflection Hypothesis
transitional change in the
blood supply to the crestal cortical bone
osteoblast death on the
surface from trauma and lack of nutrition.
does not
appear as a primary causal agent of crestal
bone loss
loss of the entire residual ridge reflected
generalized bone loss rarely is observed
at the second-stage uncovery surgery

20. Implant Osteotomy Hypothesis
osteotomy causes trauma to the bone in immediate
contact with the implant
devitalized bone zone of about 1 mm
crestal region
is more susceptible
to bone loss
limited blood supply
Greater heat generated in this denser bone

21. Implant Osteotomy Hypothesis
bone often has grown
over the first-stage cover screw
bone loss of 1.5 mm from the first thread
is not observed at Stage 11 uncovery.
osteotomy hypothesis
cannot be primarily
responsible for this phenomenon.

22. Autoimmune Response of Host Hypothesis
primary cause of bone loss around natural teeth bacteria
Occlusal trauma may accelerate the process
why does most bone loss occur the
first year (1.5 mm) and less (0.1 mm) each successive year?
this hypothesis as the primary
causal agent for the early crestal bone loss cannot be substantiated.

23. Biological Width Hypothesis
For a natural tooth, an average biological width of 2.04 mm
biological width also occurs with implants and may contribute to
Some of the marginal bone loss(0/5 mm)
The crevice between the cover screw and the implant
is similar to the crevice of
the abutment-implant connection

25. Biological Width Hypothesis
The amount of bone loss from the biological width occurs within 1 month, whether the implant is loaded or not, and is related to the crest module implant design

26. Occlusal Trauma
an injury to the attachment apparatus as a result of excessive occlusal force.
cellular biomechanics
To establish further a
correlation between marginal
bone loss and occlusal overload
engineering principles
mechanical
properties of bone
physiology of bone
implant
design biomechanics
clinical reports

27. Cellular Biomechanics
Bone remodeling at the cellular level is controlled by the mechanical environment of strain
The amount of strain in a material is directly
related to the amount of stress applied
Mechanosensors in bone
respond to minimal amounts of strain, and microstrain
levels 100 times less than the ultimate strength of bone
may trigger bone remodeling

29. Cellular Biomechanics
bone fractures at 10,000 to 20,000 microstrain units
(1% to 2% deformation)
levels 20% to 40% of this value (4000 units), bone cells may
trigger cytokines to begin a resorption response.

30. Engineering Principles
The relationship between stress and strain determines the modulus of elasticity (stiffness)
when two materials of different elastic moduli
are placed together , a stress contour increase will be observed where the two materials first come into contact.
marginal bone loss observed around
implants follows a similar pattern as the stress pattern

31. Bone Mechanical Properties
In denser bone, there is less strain under a
given load compared with softer bone
less bone remodeling
The initial peri-implant bone loss from implant
insertion to uncovery was similar for all bone qualities
6 months after prosthesis delivery
the more dense bone,
the less peri-implant bone loss

33. Animal Studies Miyata placed crowns on integrated dental implants
with no occlusal contacts (control group)
Premature interceptive occlusal contacts of
100 , 180, and m in a monkey animal model
After 4 weeks of premature occlusal loads, the
implants were removed and evaluated

34. 180 Micron premature contacts

35. Clinical Reports

36. Clinical Reports an increase in marginal
bone loss around implants closest
to a cantilever used to restore the
lost dentition
Cantilever length and an increase in occlusal stress to the nearest abutment are directly related

37. Clinical Reports
overload from parafunctional habits may be
the most probable cause of implant loss and marginal bone loss after loading
occlusal loads on an implant may act as a bending moment, which increases stress at the marginal bone level and can cause implant body fracture
Bone loss from occlusal overload is not only possible,
but
may even be reversible when found early in the process

38. Implant Design Biomechanics
The design and surface condition of the implant body
may affect the amount of strain distributed to a
implant-bone interface.
bone loss around loaded screw-type implants with machined surfaced V-threads or a sandblasted/acid-etched square-thread design
the average bone loss was 2.4 mm
(v-thread) versus 1.6 mm (square thread)
design and surface condition
more than the biological
width, microgap position,
and/or surgical causes are
involved in bone loss

39. Discussion

40. Discussion Limited marginal bone loss during the first year of
function after Stage Il surgery has been observed
around the implant
that occlusal overload may be an etiology
for crestal bone loss does not mean other factors are not present.
the microgap and the biological
width often affect the marginal bone during the first
month after the implant becomes perrnucosal

41. Discussion if Implant crown height puzzling element
is a vertical cantilever, which may magnify the stresses if
Occlusal loading forces can cause crestal bone loss, the resulting increased moment forces should further promote the loss of bone until the implant fails
bone physiology
implant design mechanics

42. Bone Physiology The bone is less dense and weaker at Stage 2 implant
surgery than it is 1 year later after prosthetic loading
The bone changed from a fine trabecular
pattern after initial healing to a more dense and coarse trabecular pattern after loading

43. Implant Design Biomechanics
Implant design may affect the magnitude or type of
forces applied to the bone-implant interface
A smooth collar at the crest module may transmit shear forces to the bone.
The first thread
or a roughened surface condition of the implant is
where the type of force changes from primarily shear
to compressive or tensile loads

45. EFFECT ON TREATMENT PLANNING
Stress-related conditions that affect the treatment
planning in implant dentistry include :
bone volume lost after tooth loss
bone quaIity decrease after tooth loss
complications of surgery
implant positioning
initial loading of an implant
implant design

46. EFFECT ON TREATMENT PLANNING
Understanding the relationships of stress and
related complications provides a basis for a consistent
treatment system

47. Patient Force Factors force factors to consider : stress :
force divided by the area to which the forces are applied
force factors to consider :
(1) bruxism
(2) clenching
(3) tongue thrust
(4) crown height
(5) masticatory dynamics
(6) the opposing arch

48. Bone Density is directly related to the strength of the bone
Dense cortical bone is 10 times
stronger than the soft, fine trabecular bone
Progressive bone loading :
changes the amount and density of the implant-bone contact.
increases the quantity of bone

49. Key Implant Positions & Implant/Abutment Number
more important from a stress management perspective
In one- or two-unit prostheses, an implant should be
placed in each prospective tooth position, without a
cantilever
In a three- to four-unit
restoration, the most important abutments are the
terminal abutments

51. Key Implant Positions & Implant/Abutment Number
In a 5- to 14-unit prosthesis, intermediary abutments
are also important to limit the edentulous spans to less than three pontics.
It is suggested :
multiple missing adjacent teeth be
replaced in a staggered position (tripod effect)
a larger intermediary implant be inserted

52. Key Implant Positions & Implant/Abutment Number
An edentulous mandible :
Anterior and the bilateral posterior regions
A key implant position is one implant in each region
An edentulous maxilla :
anterior region (laterals and centrals), bilateral canines,
and the bilateral posterior
one implant in each region, or at least five key implants

55. Key Implant Positions & Implant/Abutment Number
The overall stress to the implant system may be reduced
By :
increasing the area over which the force is applied
The most effective method :
increasing the number of implants used to support a prosthesis

57. Implant Size an increase in implant diameter
extra length does little to decrease the stress at the crest of the ridge during occlusal loading
The surface area of each implant is directly
related to the width of the implant.
an increase in implant diameter
may be more effective than implant staggering to reduce stress.

58. Implant Design implant design may be the
Implant macrodesign may affect surface area even more
than an increase in width
A cylinder
implant provides 30% less surface area than a conventional
threaded implant of the same size
implant design may be the
easiest method to increase surface area
and decrease overall risk to the implant interface

59. SUMMARY

60. SUMMARY To decrease stress : Additional implants
etiology of implant complications has led to the development
of a stress-based treatment plan theorem
To decrease stress :
Additional implants
increase in implant width or height
use of more implants to decrease the number of pontics

61. Thanks for your attention !