2Stress Treatment Theorem for Implant Dentistry Presented by:Dr.Mehrak AmjadiSupervised by: Dr. Mansour RismanchianAnd Dr.saied NosouhianDental of implantologyDental implants research centerIsfahan university of mediacal science
3CariesPeriodontal diseaseEndodontic problemsCommon complications relatedto the natural dentition (Biological)CariesEndodontic problemscommon complicationsfor three-unit fixed prostheses(Biomechanical & Biological)unretained prosthesisporcelain fractureThe most common implant-related complications are biomechanical problems that occur after the implant is loaded.
4Biomechanical problems Implant overdenturesattachment fractureremovable prosthesis fractureimplant-supported fixed Prosthesesacrylic resin veneer fractureabutment or prosthetic screw looseningporcelain fractureprosthesis metal fracture
5implant failureprimarily occur within 18 months of initial implant loadingmost often in the softest bone types or the shortest implant lengths picture
7implant complicationmost common causes for implant-related complicationsare centered around stressthe overall treatment plan should :assess the greatest force factors in the system(2) establish mechanisms to protect the overallimplant-bone-prosthetic system.
8SURGICAL FAILURE reasons for the failure of an implant integration with the bone :excessive heatexcessive 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 placementThe surgical component ofimplant failure is often the least risk of implant treatment.
9EARLY 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)
10IMPACT OF OCCLUSAL OVERLOAD ON MECHANICAL COMPONENTS Screw LooseningFatigue Fractures
11Screw Loosening 6% of implant prostheses Singletooth crowns highest rate (25%) in early screw designsCantilevers also increasethe risk of screw looseningincrease length of the cantileverIncrease the forces
12Screw LooseningThe 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 dimensionLarger-diameter implants, with larger platform dimensions, reduce the forces
13Fatigue Fracturesif a lower force magnitude repeatedly hits an object, it will still fractureProsthesis screw fracture in bothfixed partial and complete fixed prostheses %Abutment screws are usually larger indiameter fracture less often %Metal framework fractures of fixed complete andoverdenture restorations %Implant body fracture has the least incidence %
14Uncemented restorations when chronic loads are applied to thecement interfacewhen shear forces are present(as found with cantilevers)Cement strengths are weakest in shear loads.
15MARGINAL BONE LOSS For the one-piece blade range from loss of marginal bone to complete failure of the implantFor the one-piece bladeimplants, was described as a"saucerization" and occurred after implant loading
16Loss of crestal BoneGreater magnitude of bone loss during the first year mm from crestal boneThe initial transosteal bone loss V- or aU-shaped pattern(described as ditching or saucerization)
18hypotheses of crestal bone loss reflection of the periosteumOsteotomymicromovement of the abutmentbacterial invasionbiological widthfactors of stress
19Periosteal Reflection Hypothesis transitional change in theblood supply to the crestal cortical boneosteoblast death on thesurface from trauma and lack of nutrition.does notappear as a primary causal agent of crestalbone lossloss of the entire residual ridge reflectedgeneralized bone loss rarely is observedat the second-stage uncovery surgery
20Implant Osteotomy Hypothesis osteotomy causes trauma to the bone in immediatecontact with the implantdevitalized bone zone of about 1 mmcrestal regionis more susceptibleto bone losslimited blood supplyGreater heat generated in this denser bone
21Implant Osteotomy Hypothesis bone often has grownover the first-stage cover screwbone loss of 1.5 mm from the first threadis not observed at Stage 11 uncovery.osteotomy hypothesiscannot be primarilyresponsible for this phenomenon.
22Autoimmune Response of Host Hypothesis primary cause of bone loss around natural teeth bacteriaOcclusal trauma may accelerate the processwhy 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.
23Biological Width Hypothesis For a natural tooth, an average biological width of 2.04 mmbiological width also occurs with implants and may contribute toSome 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
25Biological 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
26Occlusal Traumaan injury to the attachment apparatus as a result of excessive occlusal force.cellular biomechanicsTo establish further acorrelation between marginalbone loss and occlusal overloadengineering principlesmechanicalproperties of bonephysiology of boneimplantdesign biomechanicsclinical reports
27Cellular Biomechanics Bone remodeling at the cellular level is controlled by the mechanical environment of strainThe amount of strain in a material is directlyrelated to the amount of stress appliedMechanosensors in bonerespond to minimal amounts of strain, and microstrainlevels 100 times less than the ultimate strength of bonemay trigger bone remodeling
29Cellular 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 maytrigger cytokines to begin a resorption response.
30Engineering 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
31Bone Mechanical Properties In denser bone, there is less strain under agiven load compared with softer boneless bone remodelingThe initial peri-implant bone loss from implantinsertion to uncovery was similar for all bone qualities6 months after prosthesis deliverythe more dense bone,the less peri-implant bone loss
33Animal Studies Miyata placed crowns on integrated dental implants with no occlusal contacts (control group)Premature interceptive occlusal contacts of100 , 180, and m in a monkey animal modelAfter 4 weeks of premature occlusal loads, theimplants were removed and evaluated
36Clinical Reports an increase in marginal bone loss around implants closestto a cantilever used to restore thelost dentitionCantilever length and an increase in occlusal stress to the nearest abutment are directly related
37Clinical Reportsoverload from parafunctional habits may bethe most probable cause of implant loss and marginal bone loss after loadingocclusal loads on an implant may act as a bending moment, which increases stress at the marginal bone level and can cause implant body fractureBone loss from occlusal overload is not only possible,butmay even be reversible when found early in the process
38Implant Design Biomechanics The design and surface condition of the implant bodymay affect the amount of strain distributed to aimplant-bone interface.bone loss around loaded screw-type implants with machined surfaced V-threads or a sandblasted/acid-etched square-thread designthe average bone loss was 2.4 mm(v-thread) versus 1.6 mm (square thread)design and surface conditionmore than the biologicalwidth, microgap position,and/or surgical causes areinvolved in bone loss
40Discussion Limited marginal bone loss during the first year of function after Stage Il surgery has been observedaround the implantthat 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
41Discussion if Implant crown height puzzling element is a vertical cantilever, which may magnify the stressesifOcclusal loading forces can cause crestal bone loss, the resulting increased moment forces should further promote the loss of bone until the implant failsbone physiologyimplant design mechanics
42Bone Physiology The bone is less dense and weaker at Stage 2 implant surgery than it is 1 year later after prosthetic loadingThe bone changed from a fine trabecularpattern after initial healing to a more dense and coarse trabecular pattern after loading
43Implant Design Biomechanics Implant design may affect the magnitude or type offorces applied to the bone-implant interfaceA 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
45EFFECT ON TREATMENT PLANNING Stress-related conditions that affect the treatmentplanning in implant dentistry include :bone volume lost after tooth lossbone quaIity decrease after tooth losscomplications of surgeryimplant positioninginitial loading of an implantimplant design
46EFFECT ON TREATMENT PLANNING Understanding the relationships of stress andrelated complications provides a basis for a consistenttreatment system
47Patient Force Factors force factors to consider : stress : force divided by the area to which the forces are appliedforce factors to consider :(1) bruxism(2) clenching(3) tongue thrust(4) crown height(5) masticatory dynamics(6) the opposing arch
48Bone Density is directly related to the strength of the bone Dense cortical bone is 10 timesstronger than the soft, fine trabecular boneProgressive bone loading :changes the amount and density of the implant-bone contact.increases the quantity of bone
49Key Implant Positions & Implant/Abutment Number more important from a stress management perspectiveIn one- or two-unit prostheses, an implant should beplaced in each prospective tooth position, without acantileverIn a three- to four-unitrestoration, the most important abutments are theterminal abutments
51Key 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
52Key Implant Positions & Implant/Abutment Number An edentulous mandible :Anterior and the bilateral posterior regionsA key implant position is one implant in each regionAn edentulous maxilla :anterior region (laterals and centrals), bilateral canines,and the bilateral posteriorone implant in each region, or at least five key implants
55Key Implant Positions & Implant/Abutment Number The overall stress to the implant system may be reducedBy :increasing the area over which the force is appliedThe most effective method :increasing the number of implants used to support a prosthesis
57Implant Size an increase in implant diameter extra length does little to decrease the stress at the crest of the ridge during occlusal loadingThe 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.
58Implant Design implant design may be the Implant macrodesign may affect surface area even morethan an increase in widthA cylinderimplant provides 30% less surface area than a conventionalthreaded implant of the same sizeimplant design may be theeasiest method to increase surface areaand decrease overall risk to the implant interface
60SUMMARY To decrease stress : Additional implants etiology of implant complications has led to the developmentof a stress-based treatment plan theoremTo decrease stress :Additional implantsincrease in implant width or heightuse of more implants to decrease the number of pontics