هو الحکیم. Presented by:Dr.Mehrak Amjadi Supervised by: Dr. Mansour Rismanchian And Dr.saied...
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Transcript of هو الحکیم. Presented by:Dr.Mehrak Amjadi Supervised by: Dr. Mansour Rismanchian And Dr.saied...
هو الحکیم
Stress Treatment Theorem for Implant Dentistry
Presented by:Dr.Mehrak AmjadiSupervised by: Dr. Mansour Rismanchian
And Dr.saied Nosouhian Dental of implantology
Dental implants research centerIsfahan university of mediacal science
Common complications related to the natural dentition (Biological)
CariesPeriodontal disease Endodontic problems
common complicationsfor three-unit fixed prostheses(Biomechanical & Biological)
CariesEndodontic problems
unretained prosthesis
porcelain fracture
The most common implant-related complications are biomechanical problems that occur after the implant is loaded.
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
implant failure
primarily occur within 18 months of initial implant loading
most often in the softest bone types or the shortest implant lengths picture
implant complication
most common causes for implant-related complications are centered around stress
the overall treatment plan should :
(1) assess the greatest force factors in the system
(2) establish mechanisms to protect the overall implant-bone-prosthetic system.
SURGICAL FAILURE
reasons for the failure of an implantintegration with the bone :
- primary causes :excessive heat excessive pressure at the time of implant insertion(tapered screw-type)
- Micromovement of the implant while the developing interface is established (20 microns)
99% of the time may obtain rigid fixations after surgical placementThe surgical component ofimplant failure is often the least risk of implant treatment.
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)
IMPACT OF OCCLUSAL OVERLOAD ONMECHANICAL COMPONENTS
Screw Loosening
Fatigue Fractures
Screw Loosening
6% of implant prostheses
Singletooth crowns highest rate (25%) in early screw designs
Cantilevers also increasethe risk of screw loosening
increase length of the cantilever
Increase the forces
Screw Loosening
The height or depth of an antirotational component of the implant body (higheror deeper the hex height, the less stress)
The platform dimension is more importantthan the hex height dimension
Larger-diameter implants, with larger platform dimensions, reduce the forces
Fatigue Fractures
if a lower force magnitude repeatedly hits an object, it will still fracture
Prosthesis screw fracture in bothfixed partial and complete fixed prostheses 4%
Abutment screws are usually larger indiameter fracture less often 2%
Metal framework fractures of fixed complete andoverdenture restorations 3%
Implant body fracture has the least incidence 1%
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.
MARGINAL BONE LOSS
range from loss of marginal bone to complete failure of the implant
For the one-piece bladeimplants, was described as a"saucerization" and occurred after implant loading
Loss of crestal Bone
Greater magnitude of bone loss during the first year 3.3 mm from crestal bone
The initial transosteal bone loss V- or aU-shaped pattern(described as ditching or saucerization)
hypotheses of crestal bone loss
hypotheses of crestal bone loss
reflection of the periosteum
Osteotomy
micromovement of the abutment
bacterial invasion
biological width
factors of stress
Periosteal Reflection Hypothesis
transitional change in theblood supply to the crestal cortical bone
osteoblast death on thesurface from trauma and lack of nutrition.
loss of the entire residual ridge reflectedgeneralized bone loss rarely is observedat the second-stage uncovery surgery
does notappear as a primary causal agent of crestalbone loss
Implant Osteotomy Hypothesis
osteotomy causes trauma to the bone in immediatecontact with the implant
devitalized bone zone of about 1 mm
crestal regionis more susceptible to bone loss
limited blood supply
Greater heat generated in this denser bone
Implant Osteotomy Hypothesis
bone loss of 1.5 mm from the first thread is not observed at Stage 11 uncovery.
bone often has grownover the first-stage cover screw
osteotomy hypothesiscannot be primarilyresponsible for this phenomenon.
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 thefirst year (1.5 mm) and less (0.1 mm) each successive year?
this hypothesis as the primarycausal agent for the early crestal bone loss cannot be substantiated.
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 implantis similar to the crevice ofthe abutment-implant connection
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
Biological Width Hypothesis
Occlusal Trauma
an injury to the attachment apparatus as a result of excessive occlusal force.
To establish further a correlation between marginalbone loss and occlusal overload
cellular biomechanics
engineering principles
mechanicalproperties of bone
physiology of bone
implantdesign biomechanics
clinical reports
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 bonerespond to minimal amounts of strain, and microstrainlevels 100 times less than the ultimate strength of bonemay trigger bone remodeling
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.
Cellular Biomechanics
Engineering Principles
The relationship between stress and strain determines the modulus of elasticity (stiffness)
when two materials of different elastic moduliare placed together , a stress contour increase will be observed where the two materials first come into contact.
marginal bone loss observed aroundimplants follows a similar pattern as the stress pattern
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 implantinsertion to uncovery was similar for all bone qualities
6 months after prosthesis delivery
the more dense bone, the less peri-implant bone loss
Animal Studies
Miyata placed crowns on integrated dental implantswith no occlusal contacts (control group)
Premature interceptive occlusal contacts of 100 , 180, and 250 11m in a monkey animal model
After 4 weeks of premature occlusal loads, theimplants were removed and evaluated
180 Micron premature contacts 250 Micron premature contacts
Clinical Reports
Clinical Reports
an increase in marginalbone 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
Clinical Reports
overload from parafunctional habits may bethe 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, butmay even be reversible when found early in the process
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)
more than the biologicalwidth, microgap position, and/or surgical causes areinvolved in bone loss
design and surface condition
Discussion
Discussion
Limited marginal bone loss during the first year offunction after Stage Il surgery has been observedaround the implant
that occlusal overload may be an etiologyfor crestal bone loss does not mean other factors are not present.
the microgap and the biologicalwidth often affect the marginal bone during the firstmonth after the implant becomes perrnucosal
Discussion
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
Bone PhysiologyThe bone is less dense and weaker at Stage 2 implantsurgery than it is 1 year later after prosthetic loading
The bone changed from a fine trabecularpattern after initial healing to a more dense and coarse trabecular pattern after loading
Implant Design Biomechanics
Implant design may affect the magnitude or type offorces applied to the bone-implant interface
A smooth collar at the crest module may transmit shear forces to the bone.
The first threador a roughened surface condition of the implant iswhere the type of force changes from primarily shearto compressive or tensile loads
EFFECT ON TREATMENT PLANNING
Stress-related conditions that affect the treatmentplanning 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
Understanding the relationships of stress andrelated complications provides a basis for a consistenttreatment system
EFFECT ON TREATMENT PLANNING
Patient Force Factors
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
Bone Densityis directly related to the strength of the bone
Dense cortical bone is 10 timesstronger than the soft, fine trabecular bone
Progressive bone loading :
changes the amount and density of the implant-bone contact.
increases the quantity of bone
Key Implant Positions &Implant/Abutment Number
more important from a stress management perspective
In one- or two-unit prostheses, an implant should beplaced in each prospective tooth position, without acantilever
In a three- to four-unitrestoration, the most important abutments are theterminal abutments
Key Implant Positions &Implant/Abutment Number
In a 5- to 14-unit prosthesis, intermediary abutmentsare also important to limit the edentulous spans to less than three pontics.
It is suggested :
multiple missing adjacent teeth bereplaced in a staggered position (tripod effect)
a larger intermediary implant be inserted
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
Key Implant Positions &Implant/Abutment Number
The overall stress to the implant system may be reducedBy :
increasing the area over which the force is applied
The most effective method :
increasing the number of implants used to support a prosthesis
Implant Size
extra length does little to decrease the stress at the crest of the ridge during occlusal loading
The surface area of each implant is directlyrelated to the width of the implant.
an increase in implant diametermay be more effective than implant staggering to reduce stress.
Implant Design
Implant macrodesign may affect surface area even morethan an increase in width
A cylinderimplant provides 30% less surface area than a conventionalthreaded implant of the same size
implant design may be theeasiest method to increase surface area and decrease overall risk to the implant interface
SUMMARY
etiology of implant complications has led to the developmentof a stress-based treatment plan theorem
Additional implants
increase in implant width or height
use of more implants to decrease the number of pontics
SUMMARY
To decrease stress :
Thanks for your attention !