IMPLANTS-Biomechanics.ppt
- 1. RUBINA IBRAHIM II Year PG Student Department of Prosthodontia
- 2. Definition Process of analysis and determination of loading and deformation of bone in a biological system. Role Natural tooth and implants anchored differently in bone The loading of teeth, implant and peri implant bone of prosthetic superstructure Optimize the clinical implant therapy
- 3. Types Reactive Therapeutic Reactive Biomechanics Any prosthesis that increases implant loading.
- 4. Therapeutic Biomechanics Process of remediating each biomechanical factor in order to deiminish implant overlaoding
- 5. Interrelated Factors Analyzed during diagnosis and treatment planning and maintained in a state of equilibrium. Biomechanics Occlusion Esthetics
- 6. Methods of Analysis Finite element analysis – Siegele 1989, Chelland 1991 Determined the distribution and concentration of strain and deformation within implant and stated that force distribution to surrounding bone occurs at crestal bone and level of third screw thread.
- 7. Birefringence Analysis Done on plastic model utilizing polarized monochromatic light. Load Measurement : Lundreg 1989, Montag 1991 Precise data about forces exerted on Implant to supporting bone. Complicated - invivo Invitro- valuable Bond strength between implant and bone : Schmitz 1991 Done it by test of shearing, expulsion and torsion.
- 8. FORCE Definition Any application of energy, either internal or external to a structure, that which initiates, changes or arrests motion. Related Factors Magnitude Duration Type Direction Magnification
- 9. Magnitude Anatomic region and state of dentition. Craig, 1980 Molar - 390 – 880N Canine - 453N Incisor - 222N Parafunction - 1000Psi Colaizzi, 1984 Complete denture - 77 – 196N Carlsson & Haraldson, 1985 Denture with implant - 48 – 412N
- 10. Duration Mastication - 9mt/day with 20 to 30 psi Swallowing - 20mt/day with 3 to 5 psi Type Compressive, Tensile and Shear Cowin 1989 Bone - Strongest - Compression - 30% weaker - tension - 65% weakest – shear Compressive force - Maintain integrity Tensile and shear - Disrupts integrity
- 11. Direction On centric vertical contact Angle load Axial load Greater tensile & shear stress Greater compressive stress Misch 1994 30% offset load – Decreases compressive strength – 11% - Decreases tensile strength – 25%
- 12. Magnifying Factors Applied Load Torque Includes, Extreme angulation Cantilevers Crown height Parafunction Bone density Crown height - Increase in 1mm – 20% increase in torque. With same load, D1 Bone - Accommodate D4 Bone - Cannot accommodate
- 13. Torque / Moment Load / Bending Load Product of inclined resultant line of force and distance from center of rotation. Torque = Force x Distance Natural tooth - Apical 1/3rd Chelland, 1991 Implant - First third screw level. Force Vertical - towards supporting bone Lateral - away supporting bone – Creates lever arm - torque
- 14. FORCE DISTRIBUTION Chelland 1991, Weinberg, 1994 Reiger 1990 Implant Natural teeth Rigidly fixed Periodontal ligament Stiff Flexion Concentrates at crestal bone Even force distribution & 1st 3 thread level Increase Root length – increase in surface area - better force distribution. Implant length – Initial mobilization &
- 15. FORCE DISTRIBUTION PRINCIPLES System Components Vertical element – tooth or implant Connecting element Supporting medium – periodontal ligament or bone
- 16. Flexible Medium
- 17. Stiff Medium
- 18. Flexible and Stiff Medium
- 19. DIFFERENTIAL MOBILITY Qualitative difference between the flexion of periodontal ligament and stiffness of osseointegration. Micro movement Natural teeth with good bone Will move laterally approximately 0.5mm Measured occlusally. Micron Movement – Weinberg, Rangert, 1994 Implant can move laterally 0.1mm or less measured occlusally.
- 20. Natural Teeth Implant Periodontal ligament - flexion Rigidly fixed – stiff Even force distribution Concentration at crestal bone 0.5µm movement 0.1µm movement Shock absorber Rigid Reduces the magnitude of Increases the magnitude stress Occlusal trauma – No such warning signs only Signs of cold sensitivity, bone microfracture Wear facets, Pits, Drift away & mobility
- 21. Elastic modiolus similar to bone 5-10times different Therefore, with same load Increase stress, concentrates at crestal bone Surrounding bone formed childhood Forms rapid and intense Lateral force – exert Lateral force exert Movement No movement Dissipates to apex Concentrates at crestal bone
- 22. Forces acting on Implants Occlusal loads during function Para functional habits Passive Loads Mandibular flexure Contact with first stage cover screw and second stage permucosal extension. Perioral forces Non –passive prosthesis.
- 23. TRAUMATIC FORCES OR IMPLANT OVER LOADING Non passive prosthesis Parafunction Initial contact during maximum intercuspation Labial stresses generated during eccentric movements. Therefore, Eliminate posterior contact during protrusion and lateral excursion. Prosthesis come in contact only during intercuspation.
- 24. FORCE DISTRIBUTION IN MULTIPLE IMPLANT PROSTHESIS Splinting Natural tooth – Periodontal ligament – forced distribution Implant – stiff – no force distribution and only concentration at crestal bone
- 25. FORCE DISTRIBUTION IN COMBINED PROSTHESIS Supported by both natural teeth and implants Mode of attachment Flexible Stiff Flexible – internal attachment Stiff – when terminal abutments are implants
- 26. FLEXIBLE ATTACHMENT Tooth supported prosthesis – Female attachment Implant supported prosthesis – Screw retained Flexion Occurs Not Deleterious
- 27. STIFF ATTACHMENT Natural tooth – permanently cemented substructure telescopic crown Implant supported prosthesis – over crown, coping with temporary cement Tend to Loosen To eliminate, permanent cementation rather than fixed retrievability
- 28. DIAGNOSTIC FACTORS IN COMBINED PROSTHESIS Standard Prosthesis design Internal attachment placed in distal of natural tooth Differential mobility Natural tooth cannot support implant Increase in lever arm Increase Torque
- 29. Recommended Prosthesis Design One cantilever pontic from each segment Flexible internal attachment Drifting apart of segment Decreased Torque
- 30. FOUR CLINICAL VARIANT WITH IMPLANT LOADING Includes Cuspal inclination Implant inclination Horizontal Implant Offset Apical Implant Offset
- 31. Cuspal Inclination Increase in 10° increased 30% torque Implant Inclination Increase in 10° Increased 5% torque
- 32. Horizontal Implant Offset Increase in 1mm increased 15% torque Apical Implant Offset Increase in 1mm Increased 5% torque
- 33. Staggered Implant Offset – Rangert 1993 Staggered buccal and lingual offset Tripod Effect Compensates torque Implant placed 1.5mm bucal and lingual from centre line to achieve Tripodism.
- 34. Weinberg 1996 In maxilla, lingual offset - increased 24% torque Buccal offset - Decrease 24% torque Maxilla - Tripod –increase in 24% torque Mandibular - Tripodism Maxilla - As far as bucally
- 35. Weinberg, 1996 In posterior working side, occlusion. Produces buccally inclined resultant line of force on maxilla and lingually inclined resultant line of force on mandible. Reduces 73% of torque in mandible
- 36. THERAPEUTIC BIOMECHANICS Decrease cuspal inclination It reduces the distance between implant and resultant line of force.
- 37. Cross occlusion Buccolingual relation cross occlusion Reduces horizontal implant offset Reduces torque
- 38. Implant Position Implant head as close to center line of restoration – Reduces horizontal offset.
- 39. PHYSIOLOGIC VARIATION – CENTRIC RELATION Kantor, Calagna, Calenza, 1973. Centric relation record show physiologic variation of ± 0.4mm Weinberg 1998 Occlusal anatomy modified to 1.5mm horizontal fossa Produce vertical resultant line of force within expected range of physiologic variation.
- 40. Anterior Vertical Overlap Steep vertical overlap Less steep Extreme Torque Less Torque
- 41. BIOMECHANICS AND RESORPTION PATTERN Posterior Mandible Bone resorbs along root inclination Therefore, posterior mandible – bone resorb lingually Reactively Biomechancis Lingual position of restoration + Buccal implant placement - increased torque
- 42. Therapeutically Can be done by Reduced cusp inclination Implant head close to centre line of restoration Angulated abutment - parallelism
- 43. Posterior Maxilla Reactively Restricted maxilla Location of sinus Buccal cortical plate fracture Unfavourable biomechanics
- 44. Therapeutically Cuspal inclination – reduce Head of implant close to center of restoration Angled / custom – reangulated abutment Cross occlusion 1.5mm horizontal fossa.
- 45. Anterior Maxilla Reactively Esthetically - Labially Proclined - Steep vertical overlap
- 46. Therapeutically Lingual horizontal stop – redirect the force as vertically as possible. Angled abutment Implant head close to center of restoration
- 47. COMPLETE EDENTULISM AND BIOMECHANICS Screw loosening not common these patients Implant placed across and around arch Cross splinting Lateral forces –Vertical force Tripodism Excellent resistance to bending
- 48. WIDER IMPLANTS Developed by Dr.Burton Langer Advantages Increase in surface area Limited bone height Upon removal of failed standard size implant Wider implant - Abutment screw 2.5mm - Larger size – tighter joint – overall strength increases
- 49. BONE DENSITY AND BIOMECHANICS Density ∞ Strength ∞ Amount of contact with implant ∞ Distribution and dissipation of force Misch 1995 FEM study – stress contour is different for each bone density. With same load D1 - Crestal stress and lesser magnitude D2 - Greater crestal stress and along implant body D4 - Greatest stress and farther apically
- 50. BONE DENSITY AND TREATMENT PLAN MODIFIER Prosthetic factors Implant number Implant – Macrogeometry Implant – Design Coating Progressive loading
- 51. PROSTHETIC FACTOR As density decreases, biomechanical load should also decreased Shortened cantilever length Narrow oclusal table Offset load minimized RP4 > FP1, FP2, FP3, removal at night RP5 – force shared by soft tissue Force directed along long axis of implant
- 52. Implant Number Increase in number Increase in functional loading area Implant Macrogeometry Length D1 - 10mm D2 - 12mm D3 - 14mm with V-shaped thread screw Density decreased Length increased
- 53. Width Increase in width – increase in surface area 1mm increases 30% increase in surface area D3 & D4 wider implants Implant Design Smooth cylindrical implant – shear force at Interface – Coating with HA / Titanium Titanium alloy (Ti-6Al-4V) exhibit best biomechanical, biocompatible, corrosion resistance. Coating Increased bone contact area Increased surface area
- 54. Progressive Loading Misch 1990 Gradual increase in occlusal load separated by a time interval to allow bone to accommodate. Softer the bone increase in progressive loading period. Protocol Includes, Time Diet Occlusal Contacts Prosthesis Design
- 55. Time Two surgical appointments between initial implant placement and stage II uncovery may vary on density. D1 - 5 Months D2 - 4 Months D3 - 6 Months D4 - 8 Months Diet Limited to soft diet – 10 pounds Initial delivery of final prosthesis-21 pounds
- 56. Occlusal Material Initial step – no occlusal material placed over implant Provisional – Acrylic – lower impact force Final - Metal / Porcelain Occlusion Initial - No oclusal contact Provisional - Out of occlusion Final - At occlusion
- 57. Prosthesis Design First transititional – No occlusal contact No cantilever Second transititional - Occlusal contact with no cantilever Final restoration - Fine occlusal table and cantilever
- 58. SINGLE TOOTH IMPLANT AND BIOMECHANICS Requires good bone support Control of occlusal lever parallel to long axis Access for oral hygiene
- 59. When space exceeds 12mm When space less than 12mm
- 60. When space exceeds 8mm with limited width Should not be placed off center
- 61. Posterior Triangular Zone Active zone Occlusal loading parallel to long axis
- 62. Cantilever Prosthesis and Biomechanics It result in greater torque with distal abutment as fulcrum. May be compared with Class I lever arm. May extend anterior than posterior to reduce the amount of force It depends on stress factors Parafunction Crown height Impact width Implant Number
- 63. Arch form English 1993 – AP Spread Cantilever length = AP spread x 2.5 Tapering - canine and posterior implants with anterior cantilever Square - Anterior implant with posterior cantilever
- 64. Tapering Ovoid Square Less dense bone Anterior cantilever with prosthesis Distal implants, placed to increase AP-spread. Maxilla - more implants required than mandible
- 65. Sufficient bone height exist to place long implant, Avoid contact on central incisors during protrusion, labial excursion and maximum intercuspation CANTILEVER FIXED PARTIAL DENTURE
- 66. Group function - lateral movement Avoid loading on canine Lateral guidance provided by central and lateral incisor
- 67. Two implant supporting a first molar and 2nd premolar with 1st premolar cantilever Active cusp eliminated canine palatal structures.
- 68. Three implants placed with Two implants risky 2nd premolar as cantilever and /or contraindicated
- 69. MANDIBULAR FLEXURE Picton 1962 Stated that mandibular move towards midline on opening Because of external pterygoid muscle on ramus of mandible Medial movement occur distal to mental foramen and increases as it approaches ramus. James 1980 & Burch 1982 Movement - 0.8mm - 1st molar 1.5mm - Ramus area
- 70. FLEXION Implant - Natural teeth - mandible 0.1mm 0.5mm 10 to 20 times Complete cross arch splinting of posterior molar Mandible flexion Lateral force Bone loss around implant Loss of implant fixation Material fracture Unretained restoration Discomfort on openings
- 72. FATIGUE FAILURE Characterised by dynamic cyclic loadind Depends on – biomaterial geometry force magnitude number of cycles
- 73. Biomaterial Stress level below which an implant biomaterial can be loaded indefinitely is referred as endurance limit. Ti alloy exhibits high endurance limit Number of cycles Loading cycles should be reduced To eliminate parafunctional habit To reduce occlusal contacts
- 74. Implant geometry Resist bending & torsional load Related to metal thickness 2 times thicker – 16 times stronger Force magnitude Arch position( higher in posterior & anterior) Eliminate torque Increase in surface area
- 75. IMPLANT DESIGN & BIOMECHANICS Ti alloy offers best biomechanical strength & biocompatability Bending fracture resistance factor Wall thickness = (outer radius)4_ (inner radius)4 If outer diameter increases by 1mm & inner diameter unchanged 33% increase in bending fracture resistance If inner diameter decreases by 1mm & outer diameter unchanged 20% increase in bending fracture resistance
- 77. Thread pitch Thread depth
- 78. Depth –distance between major & minor diameter of thread
- 79. Implant macrogeometry Smooth sided cylindrical implants – subjected to shear forces Smooth sided tapered implants – places compressive load at interface Greater the taper – greater the compressive load delivery Taper cannot be greater than 30 degree Implant width Increase in implant width – increases functional surface area of implant Increase in 1mm width – increase in 33% of functional surface area
- 80. Implant length Increase in length –Bicortical stabilisation Maximum stress generated by lateral load can be dissipated by Implants in the range of 10-15mm Softer the bone –greater length or width Sinus grafting & nerve re-posititioning to place greater implant length Resistance to lateral loading
- 81. Crestal module design Smooth parallel sided crest –shear stess Angled crest module less than 20 degree- -Increase in bone contact area -Beneficial compressive load Larger diameter than outer thread diameter -Prevents bacterial ingress -Initial stability -Increase in surface area
- 82. Larger diameter & angulated crestal module design
- 83. Surface Coating -Titanium plasma spray -Hydoxyapatite coating Advantages -Increase in surface area -Roughness for initial stability -Stronger bone – implant interface Disadvantages -Flaking and scaling upon insertion -Plaque retention -Nidus for infection -Increased cost
- 84. IMPLANT PROTECTED OCCLUSION Occlusal load transferred within physiologic limit Misch,1993 width of occlusal table directly related to implant width Narrow occlusal table with reduced buccal contour permits sulcular oral hygiene Restoring occlusal anatomy of natural tooth -offset load -complicated home care
- 85. Narrow occlusal table + reduced Buccal contour permits oral hygiene, Axial loading & reduces fracture Posterior crest of maxilla medial to Mandibular crest
- 86. Apical Design Round cross-section do not resist torsional load Incorporation of anti –rotational feature -Vent hole- bone grow the hole -resist torsion -Flat sidegroove - bone grow against -places bone in compression
- 87. Maxillary lingual cusp & contour reduced Reduce offset load from opposing natural tooth Mandibular buccal cusp - in width & height
- 89. Occlusal material Porcelain,resin,gold Porcelain - esthetics, chewing efficiency Gold - Impact force,chewing efficiency,fracture resistance,wear,interarch space,accuracy Acrylic - Esthetics , impact force,static load
- 90. IMPLANT ORAL REHABILITATION Constitutes Muscle relaxation Absence of articular inflammation Stable condylar position Creating organic occlusion Absence of pain in stomatognathic system
- 91. Organic occlusion components Correct vertical dimension Maximum intercuspation in centric relation Adequate incisal & condylar guidance Stable bilateral posterior occlusal relation in equilibrium with long axis of implant Absence of prematurities Absence of interferences in eccentric movements
- 92. Bruxism patients Education & informed consent to gain co-operation in eliminating parafunction Use of night guard - anterior guided disooclusion - posterior cantilever out of occlusion - soft night guard releived over implant Soft tissue supported prosthesis - soft tissue tend to early load the implant & hence relieved over it Removable partial denture over healing abutment - 6mm hole diameter through metal is prepared
- 93. Final prosthesis - narrow occlusal table - centric occlusal contact aligned parallel to long axis Important criteria - additional implant - greater diameter implant
- 94. CONCLUSION Biomechanics is one of the most important consideration affecting design of the framework for an implant bone prosthesis.It must be analysised during diagnosis & treatment planning as it may influence the decision making process which ultimately reflect on the longevity of implant supported prosthesis
- 95. Bibliography Implant & restorative dentistry- Martin Dunitz Atlas of tooth & implant supported prosthesis-Lawrence A. Weinberg Atlas of oral implantology- A.Norman Cranin Contemprorary implant dentistry – Carl Misch Branemark implant system- John Beumer ITI dental implants- Thomas G.Wilson Implant prosthodontics- Fredrickson Dental implants- Winkelmann Oral rehabilitation with implant supported prosthesis - Vincente