هو الحکیم

1. هو الحکیم

2. Stress Treatment Theorem for Implant Dentistry Presented by:Dr.MehrakAmjadi Supervised by: Dr. MansourRismanchian And Dr.saiedNosouhian 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 rigidfixations 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 4% Abutment screws are usually larger in diameter fracture less often 2% Metal framework fractures of fixed complete and overdenture restorations 3% Implant body fracture has the least incidence 1%

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 • 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 3.3 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 initialperi-implant bone loss from implant insertion to uncoverywas 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 250 11m in a monkey animal model After 4 weeks of premature occlusal loads, the implants were removed and evaluated

34. 180 Micron premature contacts 250 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 puzzling element Implant crown height 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 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 trabecularbone 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