Implant biomechanics / crown and bridge dentistry

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Implant biomechanics / crown and bridge dentistry

  1. 1. 11www.indiandentalacademy.comwww.indiandentalacademy.com
  2. 2. 22 Clinical biomechanics inClinical biomechanics in implant dentistryimplant dentistry INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
  3. 3. 33 ContentsContents www.indiandentalacademy.comwww.indiandentalacademy.com
  4. 4. 44 1.1. What is biomechanics ?What is biomechanics ? 2.2. Why study biomechanics ?Why study biomechanics ? 3.3. Forces acting on dental implantsForces acting on dental implants 4.4. Moment loads and moment armsMoment loads and moment arms 5.5. Biological response to mechanical loadsBiological response to mechanical loads 6.6. Biomechanical based bone remodeling theories.Biomechanical based bone remodeling theories. www.indiandentalacademy.comwww.indiandentalacademy.com
  5. 5. 55 8.8. The biomechanical responseThe biomechanical response 9.9. Scientific rationale for dental implant designScientific rationale for dental implant design 10.10. Implant macro geometryImplant macro geometry 11.11. Surface coatingsSurface coatings 12.12. ConclusionConclusion 13.13. ReferencesReferences www.indiandentalacademy.comwww.indiandentalacademy.com
  6. 6. 66 What is biomechanics ?What is biomechanics ?  Biomedical engineering : It is the application ofBiomedical engineering : It is the application of engineering principles to living systemsengineering principles to living systems  One aspect of this field is biomechanicsOne aspect of this field is biomechanics  Biomechanics is concerned with the response ofBiomechanics is concerned with the response of biological tissues to applied loadsbiological tissues to applied loads www.indiandentalacademy.comwww.indiandentalacademy.com
  7. 7. 77 Why study biomechanics ?Why study biomechanics ? www.indiandentalacademy.comwww.indiandentalacademy.com
  8. 8. 88 Issues to be consideredIssues to be considered Mechanical loading on the implants in vivoMechanical loading on the implants in vivo Transmission of the loadings to the interfacialTransmission of the loadings to the interfacial tissuestissues Biological reaction of interfacial tissues to theseBiological reaction of interfacial tissues to these loads transmittedloads transmitted www.indiandentalacademy.comwww.indiandentalacademy.com
  9. 9. 99 Loads applied to the dentalLoads applied to the dental implantsimplants Dental implants are subjected to occlusal loadsDental implants are subjected to occlusal loads when placed in functionwhen placed in function Such loads vary in magnitude , frequency &Such loads vary in magnitude , frequency & duration depending on patients parafunctionalduration depending on patients parafunctional habitshabits www.indiandentalacademy.comwww.indiandentalacademy.com
  10. 10. 1010 Forces acting on the dentalForces acting on the dental implantsimplants Forces may be described by magnitude,Forces may be described by magnitude, duration, direction, type and magnificationduration, direction, type and magnification factorsfactors Forces acting on dental implants are vectorForces acting on dental implants are vector quantities and poses both magnitude andquantities and poses both magnitude and directiondirection Three dominant loading axes existThree dominant loading axes exist www.indiandentalacademy.comwww.indiandentalacademy.com
  11. 11. 1111www.indiandentalacademy.comwww.indiandentalacademy.com
  12. 12. 1212 Types of forcesTypes of forces Forces may be compressive, tensile or shear inForces may be compressive, tensile or shear in naturenature Shear forces the most destructiveShear forces the most destructive Compresses forces are best accommodated andCompresses forces are best accommodated and should be dominant In implant prostheticshould be dominant In implant prosthetic occlusionocclusion www.indiandentalacademy.comwww.indiandentalacademy.com
  13. 13. 1313www.indiandentalacademy.comwww.indiandentalacademy.com
  14. 14. 1414 Stresses acting on implantsStresses acting on implants Mechanical stress can be defined as the mannerMechanical stress can be defined as the manner in which the force is distributed over a surfacein which the force is distributed over a surface Internal stresses that develop in an implant andInternal stresses that develop in an implant and surrounding tissue have an effect on the long termsurrounding tissue have an effect on the long term successsuccess Magnitude of stress depends on force magnitudeMagnitude of stress depends on force magnitude and cross sectional area of the Implantand cross sectional area of the Implant www.indiandentalacademy.comwww.indiandentalacademy.com
  15. 15. 1515 Force magnitude is not completely controlled by theForce magnitude is not completely controlled by the operatoroperator The operator however has control over the functionalThe operator however has control over the functional surface area over which force is distributedsurface area over which force is distributed Functional surface areaFunctional surface area can be defined as that surfacedcan be defined as that surfaced that participates significantly in load bearing and stressthat participates significantly in load bearing and stress dissipationdissipation FSA can be optimized by increasing the number ofFSA can be optimized by increasing the number of implants and selecting well designed Implant geometryimplants and selecting well designed Implant geometry www.indiandentalacademy.comwww.indiandentalacademy.com
  16. 16. 1616 Deformation and strainDeformation and strain Load application may induce deformation of bothLoad application may induce deformation of both implant and surrounding tissuesimplant and surrounding tissues Biological tissue interprets deformation and it’sBiological tissue interprets deformation and it’s manifestations and responds with remodelingmanifestations and responds with remodeling www.indiandentalacademy.comwww.indiandentalacademy.com
  17. 17. 1717 Stress - strain relationshipStress - strain relationship The closer the modulus of elasticity of theThe closer the modulus of elasticity of the implant to the bone, less the likelihood of relativeimplant to the bone, less the likelihood of relative motion at the tissue to implant interfacemotion at the tissue to implant interface It is more important to decrease stress in softerIt is more important to decrease stress in softer bone because of greater elastic difference andbone because of greater elastic difference and lower ultimate strengthlower ultimate strength www.indiandentalacademy.comwww.indiandentalacademy.com
  18. 18. 1818 Impact loadsImpact loads When two bodies collide in a very small intervalWhen two bodies collide in a very small interval of time, relatively large reaction forces developof time, relatively large reaction forces develop Such collisions are called impactsSuch collisions are called impacts Example : occlusal loadsExample : occlusal loads Cause deformation of implants and surroundingCause deformation of implants and surrounding tissuetissue www.indiandentalacademy.comwww.indiandentalacademy.com
  19. 19. 1919 Impact loads can be decreased byImpact loads can be decreased by - Using acrylic teeth – ShalakUsing acrylic teeth – Shalak - Weiss advocated fibrous tissue to implant interfaceWeiss advocated fibrous tissue to implant interface for shock absorptionfor shock absorption - Use of intramobile element to lower the stiffnessUse of intramobile element to lower the stiffness than rest of the implantthan rest of the implant - Misch advocates and acrylic provisional withMisch advocates and acrylic provisional with progressive occlusal loading to improve B-I interfaceprogressive occlusal loading to improve B-I interface before final restorationbefore final restoration www.indiandentalacademy.comwww.indiandentalacademy.com
  20. 20. 2020 Moment loadsMoment loads Moment of force about a point tends to produceMoment of force about a point tends to produce rotation or bending about that pointrotation or bending about that point M = F x perpendicular distance (moment arm)M = F x perpendicular distance (moment arm) from the point of interestfrom the point of interest Also called torque or torsional loadAlso called torque or torsional load www.indiandentalacademy.comwww.indiandentalacademy.com
  21. 21. 2121www.indiandentalacademy.comwww.indiandentalacademy.com
  22. 22. 2222 Clinical moment arms and crestalClinical moment arms and crestal bone lossbone loss Six moments may develop about the 3 clinicalSix moments may develop about the 3 clinical coordinate axes .coordinate axes . Such loads induce microrotation and stressSuch loads induce microrotation and stress concentration at the crest of alveolar ridge – implantconcentration at the crest of alveolar ridge – implant – bone interface and leads to crestal bone loss– bone interface and leads to crestal bone loss Three clinical moment arms exist in implantThree clinical moment arms exist in implant dentistry, minimization of each is necessary todentistry, minimization of each is necessary to prevent failureprevent failure www.indiandentalacademy.comwww.indiandentalacademy.com
  23. 23. 2323www.indiandentalacademy.comwww.indiandentalacademy.com
  24. 24. 2424 Occlusal height moment armOcclusal height moment arm Acts as aActs as a moment armmoment arm for a forcefor a force componentscomponents directed alongdirected along faciolingual andfaciolingual and mesiodistalmesiodistal axisaxis www.indiandentalacademy.comwww.indiandentalacademy.com
  25. 25. 2525 Cantilever length moment armCantilever length moment arm Large moments from vertical axis forceLarge moments from vertical axis force component is seen in prosthetic environmentscomponent is seen in prosthetic environments designed with cantilevered extensions or offsetdesigned with cantilevered extensions or offset loads from rigid implantsloads from rigid implants Discal cantilever should not extend 2.5 x the A-PDiscal cantilever should not extend 2.5 x the A-P distance under ideal conditionsdistance under ideal conditions www.indiandentalacademy.comwww.indiandentalacademy.com
  26. 26. 2626 Occlusal width moment armOcclusal width moment arm Wide occlusal tables increase moment arm forWide occlusal tables increase moment arm for any offset occlusal loadsany offset occlusal loads Faciolingual rotation can be reduced by narrowFaciolingual rotation can be reduced by narrow occlusal tables and adjusting occlusion toocclusal tables and adjusting occlusion to provide more centric contactprovide more centric contact www.indiandentalacademy.comwww.indiandentalacademy.com
  27. 27. 2727 Bone response to mechanical loadsBone response to mechanical loads www.indiandentalacademy.comwww.indiandentalacademy.com
  28. 28. 2828 The biological responseThe biological response Interface is defined as a plane forming theInterface is defined as a plane forming the common boundary between two parts of mattercommon boundary between two parts of matter or spaceor space It may be a discrete boundary or a region ofIt may be a discrete boundary or a region of interaction between two materials (interface thatinteraction between two materials (interface that exists between implant and bone)exists between implant and bone) www.indiandentalacademy.comwww.indiandentalacademy.com
  29. 29. 2929 The biomechanical environment plays anThe biomechanical environment plays an immediate role in the quality and compositionalimmediate role in the quality and compositional outcome of the new interfaceoutcome of the new interface Relative movement (micro motion) betweenRelative movement (micro motion) between implant and bone at the time of placement leadsimplant and bone at the time of placement leads to the development of fibro osseous interfaceto the development of fibro osseous interface www.indiandentalacademy.comwww.indiandentalacademy.com
  30. 30. 3030 Bone responds to hormonal and biomechanicalBone responds to hormonal and biomechanical regulation [functional loading]regulation [functional loading] These two are often in opposition with eachThese two are often in opposition with each otherother The objective of good implant design would beThe objective of good implant design would be to establish and maintain a strain environmentto establish and maintain a strain environment within the host bone tissue and interface thatwithin the host bone tissue and interface that favors osseointegration of the implantfavors osseointegration of the implant www.indiandentalacademy.comwww.indiandentalacademy.com
  31. 31. 3131 Biomechanical based boneBiomechanical based bone remodeling theoriesremodeling theories www.indiandentalacademy.comwww.indiandentalacademy.com
  32. 32. 3232 1887 Meier1887 Meier 1892 Wolff1892 Wolff 1895 Roux1895 Roux H M Frost proposed theory of mechanostat andH M Frost proposed theory of mechanostat and `Flexure drift hypothesis``Flexure drift hypothesis` Cowin proposed potential mechanism by whichCowin proposed potential mechanism by which bone cells sense mechanical loadbone cells sense mechanical load www.indiandentalacademy.comwww.indiandentalacademy.com
  33. 33. 3333www.indiandentalacademy.comwww.indiandentalacademy.com
  34. 34. 3434 The biomechanical responseThe biomechanical response www.indiandentalacademy.comwww.indiandentalacademy.com
  35. 35. 3535 Strain has been generically defined in relation toStrain has been generically defined in relation to deformation and applied stressdeformation and applied stress The mechanical properties of trabecular andThe mechanical properties of trabecular and cortical bone found within the oral environmentcortical bone found within the oral environment exhibit a high degree of variation as a function ofexhibit a high degree of variation as a function of load direction, rate and durationload direction, rate and duration The mechanical strain exhibited in bone IsThe mechanical strain exhibited in bone Is ultimately a function of bone densityultimately a function of bone density www.indiandentalacademy.comwww.indiandentalacademy.com
  36. 36. 3636 Dependence on direction of loadingDependence on direction of loading The degree to which the mechanical propertiesThe degree to which the mechanical properties of cortical bone are dependent on its structure isof cortical bone are dependent on its structure is referred to as anisotropyreferred to as anisotropy A material is said to be orthotropic if it exhibitsA material is said to be orthotropic if it exhibits different properties in all three directionsdifferent properties in all three directions Isotropic if its properties are same in all threeIsotropic if its properties are same in all three directiondirection www.indiandentalacademy.comwww.indiandentalacademy.com
  37. 37. 3737 Transversely isotropic describes the material inTransversely isotropic describes the material in which two of the three directions exhibited thewhich two of the three directions exhibited the same mechanical propertiessame mechanical properties Example cortical bone of human mandibleExample cortical bone of human mandible Ashman & Van Bushirk suggest that corticalAshman & Van Bushirk suggest that cortical bone of mandible functions as the long bone thatbone of mandible functions as the long bone that has been molded into a curved beam geometryhas been molded into a curved beam geometry www.indiandentalacademy.comwww.indiandentalacademy.com
  38. 38. 3838 Dependence on the rate of loadingDependence on the rate of loading A material is said to be viscoelastic if itsA material is said to be viscoelastic if its mechanical behavior is dependent on the rate ofmechanical behavior is dependent on the rate of load applicationload application Bone fails at a higher load but with lessBone fails at a higher load but with less allowable elongation (deformation) at higher asallowable elongation (deformation) at higher as compared with lower strain stresscompared with lower strain stress Thus bone behaves in a more brittle fashion atThus bone behaves in a more brittle fashion at higher strain ratehigher strain rate www.indiandentalacademy.comwww.indiandentalacademy.com
  39. 39. 3939 Dependence on duration of loadingDependence on duration of loading Carter and Caylor have described bone damageCarter and Caylor have described bone damage or fracture caused by mechanical stress as theor fracture caused by mechanical stress as the sum of both the damage caused by creep orsum of both the damage caused by creep or time dependent loading and cyclic of fatiguetime dependent loading and cyclic of fatigue loading and the relative interaction of these twoloading and the relative interaction of these two types of damagetypes of damage CreepCreep Fatigue strengthFatigue strength www.indiandentalacademy.comwww.indiandentalacademy.com
  40. 40. 4040 Dependence on species anatomic locationDependence on species anatomic location Dependence on side constraintDependence on side constraint Dependence on structural densityDependence on structural density www.indiandentalacademy.comwww.indiandentalacademy.com
  41. 41. 4141 Scientific rationale for dentalScientific rationale for dental implant designimplant design Implants function to transfer to load theImplants function to transfer to load the surrounding biological issuesurrounding biological issue Biomechanical load management Is dependentBiomechanical load management Is dependent on two factors:on two factors: - Character of the applied forceCharacter of the applied force - Functional surface area which the load isFunctional surface area which the load is dissipateddissipated www.indiandentalacademy.comwww.indiandentalacademy.com
  42. 42. 4242 Design process for implant begins with theDesign process for implant begins with the identification of clinical problems to beidentification of clinical problems to be addressedaddressed Scientific principles related to the force andScientific principles related to the force and surface area are combined with engineeringsurface area are combined with engineering solutions to pursue the desire to clinical goalssolutions to pursue the desire to clinical goals www.indiandentalacademy.comwww.indiandentalacademy.com
  43. 43. 4343 Character of forces applied toCharacter of forces applied to dental implantsdental implants Forces applied to dental implants may beForces applied to dental implants may be characterized in terms of five distinctcharacterized in terms of five distinct although related factors, namely :although related factors, namely : - MagnitudeMagnitude - DurationDuration - TypeType - DirectionDirection - MagnificationMagnification www.indiandentalacademy.comwww.indiandentalacademy.com
  44. 44. 4444 Force magnitudeForce magnitude www.indiandentalacademy.comwww.indiandentalacademy.com
  45. 45. 4545 Physiologic constraints on designPhysiologic constraints on design:: - Magnitude of byte for some eighties As a function ofMagnitude of byte for some eighties As a function of anatomical region and state of dentitionanatomical region and state of dentition - After sustained period of edentulism bone foundationAfter sustained period of edentulism bone foundation becomes less dense and may not be able to supportbecomes less dense and may not be able to support normal physiological bite forces on the implantsnormal physiological bite forces on the implants - Careful treatment planning & appropriate implant designCareful treatment planning & appropriate implant design selection is imperative to lower magnitude of loads I-Bselection is imperative to lower magnitude of loads I-B interfaceinterface www.indiandentalacademy.comwww.indiandentalacademy.com
  46. 46. 4646 Influence on biomaterial selection:Influence on biomaterial selection: - Many biocompatible materials unable to sustainMany biocompatible materials unable to sustain the magnitude of parafunctional loads imposedthe magnitude of parafunctional loads imposed - Si , hydroxyapatite , C have tensile strength toSi , hydroxyapatite , C have tensile strength to low for primary implant material, hence uselow for primary implant material, hence use escort things on a stronger substrate materialescort things on a stronger substrate material www.indiandentalacademy.comwww.indiandentalacademy.com
  47. 47. 4747www.indiandentalacademy.comwww.indiandentalacademy.com
  48. 48. 4848 - Ti and Ti alloys have excellent biocompatibilityTi and Ti alloys have excellent biocompatibility - Titanium has closest approximation to boneTitanium has closest approximation to bone stiffness than any other metal ( 6x )stiffness than any other metal ( 6x ) - Low modulus of elasticity (stiffness) lead toLow modulus of elasticity (stiffness) lead to failure of carbon implantsfailure of carbon implants - Excessive stiffness ( 33x ) led to disuse atrophyExcessive stiffness ( 33x ) led to disuse atrophy and failure of ceramic implantsand failure of ceramic implants www.indiandentalacademy.comwww.indiandentalacademy.com
  49. 49. 4949 Force durationForce duration www.indiandentalacademy.comwww.indiandentalacademy.com
  50. 50. 5050 Force typeForce type www.indiandentalacademy.comwww.indiandentalacademy.com
  51. 51. 5151 Physiological constraints on design :Physiological constraints on design : - Bone is strongest in compressive > tensile >Bone is strongest in compressive > tensile > shearshear - Endosteal implants load bone - implant interfaceEndosteal implants load bone - implant interface in pure shear, unless surface features arein pure shear, unless surface features are incorporated in design to transform shear loadsincorporated in design to transform shear loads to more resistant force typesto more resistant force types www.indiandentalacademy.comwww.indiandentalacademy.com
  52. 52. 5252 Influence on Implant body design :Influence on Implant body design : - Smooth cylinder body results essentially in shearSmooth cylinder body results essentially in shear type of force at the interfacetype of force at the interface - Threaded implants can transform the type ofThreaded implants can transform the type of force at bone implant interfaceforce at bone implant interface - Three types of thread implants are square, VThree types of thread implants are square, V shaped and buttressshaped and buttress - V shaped and buttress exert ten times greaterV shaped and buttress exert ten times greater force than square threadforce than square thread www.indiandentalacademy.comwww.indiandentalacademy.com
  53. 53. 5353 Force directionForce direction www.indiandentalacademy.comwww.indiandentalacademy.com
  54. 54. 5454 Physiological constraints :Physiological constraints : - Normal anatomy and bone resorption of theNormal anatomy and bone resorption of the edentulism poses angulation challengesedentulism poses angulation challenges - Bonus most resistant to compressive forcesBonus most resistant to compressive forces falling along the long axisfalling along the long axis - A 30° offset load reduces the compressiveA 30° offset load reduces the compressive strand of the borne by 11% and tensile strengthstrand of the borne by 11% and tensile strength by 25%by 25% www.indiandentalacademy.comwww.indiandentalacademy.com
  55. 55. 5555 Influence on Implant body design :Influence on Implant body design : - As angulation of load increases stress aroundAs angulation of load increases stress around the implant Increases particularly in thethe implant Increases particularly in the vulnerable crestal regionvulnerable crestal region - As a result all implants are designed forAs a result all implants are designed for placement perpendicular to the occlusal planeplacement perpendicular to the occlusal plane - The face of thread or plateau can change theThe face of thread or plateau can change the direction of load from prosthesis to abutmentdirection of load from prosthesis to abutment connection, to a different force direction at theconnection, to a different force direction at the bonebone www.indiandentalacademy.comwww.indiandentalacademy.com
  56. 56. 5656 Force magnificationForce magnification Extreme angulation and parafunctional habitsExtreme angulation and parafunctional habits exceed the capability of the dental implantexceed the capability of the dental implant design to withstand physiological loaddesign to withstand physiological load Cantilever send crown heights are levers andCantilever send crown heights are levers and force magnifiersforce magnifiers Careful treatment planning and multiple implantsCareful treatment planning and multiple implants had indicated in case of force magnificationhad indicated in case of force magnification www.indiandentalacademy.comwww.indiandentalacademy.com
  57. 57. 5757 Surface areaSurface area www.indiandentalacademy.comwww.indiandentalacademy.com
  58. 58. 5858 Anatomical constraints on surfaceAnatomical constraints on surface area optimizationarea optimization Bone vol : external architecture of boneBone vol : external architecture of bone - Width is greater in the posterior regionWidth is greater in the posterior region - In general 6 to 8mm bone is available in theIn general 6 to 8mm bone is available in the anterior region and 4mm implant is usedanterior region and 4mm implant is used - 7mm width is available in the posterior region7mm width is available in the posterior region and 5mm implant is usedand 5mm implant is used - Therefore implant width may increase asTherefore implant width may increase as amount of force magnification increases fromamount of force magnification increases from anteriors to post. regionanteriors to post. region www.indiandentalacademy.comwww.indiandentalacademy.com
  59. 59. 5959 - On the contrary born height usually decreasesOn the contrary born height usually decreases from anterior mandible, compared with thefrom anterior mandible, compared with the anterior maxilla, the posterior mandible, to theanterior maxilla, the posterior mandible, to the least in the edentulous posterior maxillaleast in the edentulous posterior maxilla - Hence as occlusal force increases bone heightHence as occlusal force increases bone height and vol decreasesand vol decreases www.indiandentalacademy.comwww.indiandentalacademy.com
  60. 60. 6060 Bone quality : internal architecture of boneBone quality : internal architecture of bone - four distinctly different bone densityfour distinctly different bone density classifications exist within the max and mandclassifications exist within the max and mand - Greater failure rate has been documented inGreater failure rate has been documented in porous bone compared with dense boneporous bone compared with dense bone - Additional implants or implants with greaterAdditional implants or implants with greater surface area have to be used in porous bonesurface area have to be used in porous bone www.indiandentalacademy.comwww.indiandentalacademy.com
  61. 61. 6161 Functional surface area forcesFunctional surface area forces vs.vs. Total surface areaTotal surface area For a given bone vol, implant surface area mustFor a given bone vol, implant surface area must be optimized for functional loadsbe optimized for functional loads FSA: defined as the area that actively serves toFSA: defined as the area that actively serves to dissipate compressive and tensile non sheardissipate compressive and tensile non shear loads through the I-B interface and providesloads through the I-B interface and provides initial stability of the implant following its surgicalinitial stability of the implant following its surgical placementplacement www.indiandentalacademy.comwww.indiandentalacademy.com
  62. 62. 6262 Functional thread surface area: portion of the thread thatFunctional thread surface area: portion of the thread that participates in compressive load transmission under theparticipates in compressive load transmission under the action of a axial or near axial occlusal loadaction of a axial or near axial occlusal load Total surface area : may Include a passive area thatTotal surface area : may Include a passive area that does not participate in load transferdoes not participate in load transfer Example : plasma spray coatings have 600% more TSAExample : plasma spray coatings have 600% more TSA but less than 30% is actually exposed to the bonebut less than 30% is actually exposed to the bone Since most stress to the I-B interface Is in the crestal 1/2Since most stress to the I-B interface Is in the crestal 1/2 of the implant, the crestal zone is most important toof the implant, the crestal zone is most important to distribute stresses appropriatelydistribute stresses appropriately www.indiandentalacademy.comwww.indiandentalacademy.com
  63. 63. 6363 Design variables in SA optimizationDesign variables in SA optimization www.indiandentalacademy.comwww.indiandentalacademy.com
  64. 64. 6464 Implant macrogeometryImplant macrogeometry Smooth sided cylindric implants provide surgicalSmooth sided cylindric implants provide surgical ease however B-I interface is subjected toease however B-I interface is subjected to significantly large shear conditionssignificantly large shear conditions Smooth sided , tapered implants allows for aSmooth sided , tapered implants allows for a component of compressive load to be deliveredcomponent of compressive load to be delivered to bone B-I interface depending on the degree ofto bone B-I interface depending on the degree of tapertaper www.indiandentalacademy.comwww.indiandentalacademy.com
  65. 65. 6565 Threaded implants with circular cross sectionThreaded implants with circular cross section provide ease of surgical placement and allow forprovide ease of surgical placement and allow for >FSA optimization to transfer compressive>FSA optimization to transfer compressive forces to the B-I interfaceforces to the B-I interface Also gives initial rigid fixation to limit microAlso gives initial rigid fixation to limit micro movement during healingmovement during healing Smooth sided cylinder depends on coating ourSmooth sided cylinder depends on coating our micro structure for load transmission to bonemicro structure for load transmission to bone www.indiandentalacademy.comwww.indiandentalacademy.com
  66. 66. 6666 Implant widthImplant width Over the years implants have graduallyOver the years implants have gradually Increased in widthIncreased in width Scientific principle being > the width greater theScientific principle being > the width greater the surface areasurface area 4mm implants have 33% > SA than 3mm4mm implants have 33% > SA than 3mm implantsimplants Largest the width better the emergence profile ofLargest the width better the emergence profile of the crownthe crown www.indiandentalacademy.comwww.indiandentalacademy.com
  67. 67. 6767 Crestal bone anatomy limits implants to <Crestal bone anatomy limits implants to < 5.5mm except in limited situations5.5mm except in limited situations Thus implant design innovations in crestalThus implant design innovations in crestal region are required to provide increase in FSAregion are required to provide increase in FSA in this vulnerable regionin this vulnerable region www.indiandentalacademy.comwww.indiandentalacademy.com
  68. 68. 6868 Thread geometryThread geometry FSA for unit length of the implant may beFSA for unit length of the implant may be modified by varying three geometric parametersmodified by varying three geometric parameters of implantof implant - Thread pitchThread pitch - Thread shapeThread shape - Thread depthThread depth www.indiandentalacademy.comwww.indiandentalacademy.com
  69. 69. 6969 Thread pitch is defined as the distanceThread pitch is defined as the distance measured parallel with its axis between adjacentmeasured parallel with its axis between adjacent thread forms ( for V type threads ), for thethread forms ( for V type threads ), for the number of threads per unit length in the samenumber of threads per unit length in the same axial plane and on the same side of the axisaxial plane and on the same side of the axis Smaller / finer pitch : more threads on theSmaller / finer pitch : more threads on the Implant body for given unit length and thusImplant body for given unit length and thus greater surface area per unit lengthgreater surface area per unit length www.indiandentalacademy.comwww.indiandentalacademy.com
  70. 70. 7070www.indiandentalacademy.comwww.indiandentalacademy.com
  71. 71. 7171 Thread shape:Thread shape: • V shapedV shaped • SquareSquare • ButtressButtress - Dental implant applications dictates the needDental implant applications dictates the need for a thread shape optimized for a long-termfor a thread shape optimized for a long-term function ( load transmission ) under occlusalfunction ( load transmission ) under occlusal intrusive ( opposite of pull out ) load directionsintrusive ( opposite of pull out ) load directions www.indiandentalacademy.comwww.indiandentalacademy.com
  72. 72. 7272www.indiandentalacademy.comwww.indiandentalacademy.com
  73. 73. 7373 The square thread provides an optimum surfaceThe square thread provides an optimum surface area for intrusive & compressive loadarea for intrusive & compressive load transmissiontransmission Shear loading most detrimental to boneShear loading most detrimental to bone Shear force on V thread face its ten timesShear force on V thread face its ten times greater than on square threadgreater than on square thread Buttress has similar shear component as VButtress has similar shear component as V under occlusal loadunder occlusal load www.indiandentalacademy.comwww.indiandentalacademy.com
  74. 74. 7474www.indiandentalacademy.comwww.indiandentalacademy.com
  75. 75. 7575 Thread depth : refers to the distance betweenThread depth : refers to the distance between the major and minor diameter of the threadthe major and minor diameter of the thread It may be varied for the length of the implant toIt may be varied for the length of the implant to increase FSA in the region of highest stress,increase FSA in the region of highest stress, example : crestal regionexample : crestal region Reverse taper leads to a dramatic increase inReverse taper leads to a dramatic increase in functional surface area at the crest of the bonefunctional surface area at the crest of the bone where stresses are highestwhere stresses are highest www.indiandentalacademy.comwww.indiandentalacademy.com
  76. 76. 7676www.indiandentalacademy.comwww.indiandentalacademy.com
  77. 77. 7777 Implant lengthImplant length As length of the implant increases so does theAs length of the implant increases so does the overall total surface areaoverall total surface area Once I-B interface is formed excessively longOnce I-B interface is formed excessively long implants do not receive stress transmission toimplants do not receive stress transmission to the apical region and are not neededthe apical region and are not needed D3, D4 bone in the posterior region have lessD3, D4 bone in the posterior region have less available bone heightavailable bone height www.indiandentalacademy.comwww.indiandentalacademy.com
  78. 78. 7878 Nerve repositioning is cited as an acceptableNerve repositioning is cited as an acceptable clinical treatment to facilitate longer implants inclinical treatment to facilitate longer implants in the posterior mandiblethe posterior mandible Maxillary sinus grafts done for posterior maxillaMaxillary sinus grafts done for posterior maxilla Longer implants have been suggested toLonger implants have been suggested to provide greater stability under lateral loadingprovide greater stability under lateral loading Studies show that majority of stress generatedStudies show that majority of stress generated by lateral load can be dissipated by implant inby lateral load can be dissipated by implant in the range of 10 -15 mm length compared withthe range of 10 -15 mm length compared with implant of 20 – 30 mm lengthimplant of 20 – 30 mm length www.indiandentalacademy.comwww.indiandentalacademy.com
  79. 79. 7979 Crest module configurationCrest module configuration Crest module of implant body is the transostealCrest module of implant body is the transosteal region from implant body and is characterized asregion from implant body and is characterized as a region of high concentration of mechanicala region of high concentration of mechanical stressstress Many crest modules have been designed toMany crest modules have been designed to reduce plaque accumulation once bone loss hasreduce plaque accumulation once bone loss has occurredoccurred However design of crest module contributes toHowever design of crest module contributes to crestal bone losscrestal bone loss www.indiandentalacademy.comwww.indiandentalacademy.com
  80. 80. 8080 Angulated crest module > 20° with surfaceAngulated crest module > 20° with surface texture that increases bone contact causestexture that increases bone contact causes slightly beneficial cumbersome stress toslightly beneficial cumbersome stress to adjacent bone and decreased bone lossadjacent bone and decreased bone loss Crest module should be slightly larger than outerCrest module should be slightly larger than outer thread diameterthread diameter Crest module height is often 2 mmCrest module height is often 2 mm A polished collar of minimum height should beA polished collar of minimum height should be designed on the superior portion just below thedesigned on the superior portion just below the prosthesis platform (0.5 mm)prosthesis platform (0.5 mm) www.indiandentalacademy.comwww.indiandentalacademy.com
  81. 81. 8181www.indiandentalacademy.comwww.indiandentalacademy.com
  82. 82. 8282 Apical design considerationsApical design considerations Most root form implants are circular in crossMost root form implants are circular in cross sectionsection Around cross section does not resist shearAround cross section does not resist shear forcesforces As a result anti - rotational feature isAs a result anti - rotational feature is incorporated in apical region of implant bodyincorporated in apical region of implant body www.indiandentalacademy.comwww.indiandentalacademy.com
  83. 83. 8383 Another anti - rotational feature flat sides orAnother anti - rotational feature flat sides or gross along the body or apical the region of thegross along the body or apical the region of the implant bodyimplant body When bone grows against flat end it is keptWhen bone grows against flat end it is kept under compression with rotational loads , thusunder compression with rotational loads , thus apical end must be flat than pointedapical end must be flat than pointed www.indiandentalacademy.comwww.indiandentalacademy.com
  84. 84. 8484 Abutment designAbutment design Abutments for flat surfaced implants: implantsAbutments for flat surfaced implants: implants that do not have any anti rotational elementsthat do not have any anti rotational elements are flat surfaced and usually demandare flat surfaced and usually demand attachment of one piece abutmentsattachment of one piece abutments These implants are used only when multipleThese implants are used only when multiple units are to be cemented by connecting themunits are to be cemented by connecting them with overlay bars or crownswith overlay bars or crowns Should not be used for replacing single to theShould not be used for replacing single to the restorationsrestorations www.indiandentalacademy.comwww.indiandentalacademy.com
  85. 85. 8585 Abutments for implants with anti-rotationalAbutments for implants with anti-rotational features: anti - rotational features arefeatures: anti - rotational features are - The External hexThe External hex - The Internal hexThe Internal hex - The Spline attachment and variations , splinesThe Spline attachment and variations , splines are fin to groove configurations with long andare fin to groove configurations with long and successful history in engineeringsuccessful history in engineering - The Park starThe Park star - The Morse taper ( cold weld ) attachmentThe Morse taper ( cold weld ) attachment www.indiandentalacademy.comwww.indiandentalacademy.com
  86. 86. 8686 Abutments are commonly available into pieces ,Abutments are commonly available into pieces , which demands that the abutment be seated onwhich demands that the abutment be seated on the implant their by engaging the anti-rotationalthe implant their by engaging the anti-rotational component , a retaining screw is used to tightencomponent , a retaining screw is used to tighten the abutment to the implantthe abutment to the implant A critical factor that requires consideration whenA critical factor that requires consideration when a retaining screw is fastened is thea retaining screw is fastened is the `phenomenon of thread stretch`.`phenomenon of thread stretch`. www.indiandentalacademy.comwww.indiandentalacademy.com
  87. 87. 8787 This is caused by relaxation of the screw metalThis is caused by relaxation of the screw metal after it has been tightened . To ensureafter it has been tightened . To ensure continuing screw tightness, retorque the screwcontinuing screw tightness, retorque the screw subsequently with the proper force for upto foursubsequently with the proper force for upto four additional procedures over a one week period.additional procedures over a one week period. Two piece designs permit angulated abutmentsTwo piece designs permit angulated abutments (10 to 30° )(10 to 30° ) Three piece designs are available , consist of anThree piece designs are available , consist of an angled abutment , an interposed collar ( eachangled abutment , an interposed collar ( each with Its own anti-rotational component ) and awith Its own anti-rotational component ) and a fixation screw .fixation screw . Custom cast abutments are made when preciseCustom cast abutments are made when precise angulations are required for proper prostheticangulations are required for proper prosthetic positionposition www.indiandentalacademy.comwww.indiandentalacademy.com
  88. 88. 8888 Surface coatingsSurface coatings Titanium plasma spray ( TPS )Titanium plasma spray ( TPS ) - Implant body may be covered with a porousImplant body may be covered with a porous coating , two materials commonly used for thiscoating , two materials commonly used for this purpose titanium and hydroxyapatitepurpose titanium and hydroxyapatite - Both are plasma sprayed on to implant bodyBoth are plasma sprayed on to implant body - TPS increases B-I surface area and acts similarTPS increases B-I surface area and acts similar to three dimensional surface rates may stimulateto three dimensional surface rates may stimulate adhesion osteogenesisadhesion osteogenesis www.indiandentalacademy.comwww.indiandentalacademy.com
  89. 89. 8989 - There is 600% increase in total surface areaThere is 600% increase in total surface area - FSA increases by 25 to 30% which is significantFSA increases by 25 to 30% which is significant - Improved initial fixation of implant is seen specially inImproved initial fixation of implant is seen specially in softer bonesofter bone Hydroxyapatite coatings :Hydroxyapatite coatings : - Similar roughness as TPS and increase FSASimilar roughness as TPS and increase FSA - Direct bonding to bone which is of greater strengthDirect bonding to bone which is of greater strength - Enhanced gap healing in hydroxyapatite coating is seenEnhanced gap healing in hydroxyapatite coating is seen www.indiandentalacademy.comwww.indiandentalacademy.com
  90. 90. 9090 Advantages of surface coatings:Advantages of surface coatings: - Increased surface areaIncreased surface area - Increased roughness for initial stabilizationIncreased roughness for initial stabilization - Stronger B-I interfaceStronger B-I interface Additional advantages of HA over TPSAdditional advantages of HA over TPS - Faster healing of B-I interfaceFaster healing of B-I interface - Increased gap healing between B & HAIncreased gap healing between B & HA - Stronger interface than in TPSStronger interface than in TPS - Less corrosion of metalLess corrosion of metal www.indiandentalacademy.comwww.indiandentalacademy.com
  91. 91. 9191 Disadvantages of surface coatings :Disadvantages of surface coatings : - Coatings may be damaged when beingCoatings may be damaged when being inserted in dense boneinserted in dense bone - Increased surface roughness with the riskIncreased surface roughness with the risk of bacterial contamination when presentof bacterial contamination when present above boneabove bone - HA : increased plaque retention whenHA : increased plaque retention when exposedexposed - Increased costsIncreased costs www.indiandentalacademy.comwww.indiandentalacademy.com
  92. 92. 9292 ConclusionConclusion www.indiandentalacademy.comwww.indiandentalacademy.com
  93. 93. 9393 ReferencesReferences Contemporary implant dentistry – Carl E. Misch , 2Contemporary implant dentistry – Carl E. Misch , 2ndnd editionedition Dental materials – Philips 11Dental materials – Philips 11thth editionedition Fundamentals of implant dentistry, Weiss and WeissFundamentals of implant dentistry, Weiss and Weiss Implants in restorative dentistry, ScortsessiImplants in restorative dentistry, Scortsessi Journal of dental education vol 52 no 12 pg 755, 1988Journal of dental education vol 52 no 12 pg 755, 1988 Jpd 1985 : 54; 410-14Jpd 1985 : 54; 410-14 Jpd 1983 : 49; 843-49Jpd 1983 : 49; 843-49 www.indiandentalacademy.comwww.indiandentalacademy.com
  94. 94. 9494 Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com

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