IN THE NAME OF GOD

1. IN THE NAME OF GOD m.akouchekian

2. Implant body size:A biomechanical and esthetic rationale Presented by:Dr.m.akouchakian Supervised by: Dr. MansourRismanchian And Dr.saiedNosouhian Dental of implantology Dental implants research center Isfahan university of mediacal science m.akouchekian

3. Implant body size:A biomechanical and esthetic rationale m.akouchekian

4. Introduction • The initial treatment plan for implan dentistry: include the ideal implant size(based primarily on biomechanic and esthetic considerationse) • primarily:existing bone volume in height, width and length determined The size of implant m.akouchekian

5. Ideal treatment plan sequence • The prothesis first is planned • The patient force factors are considered to evaluated the magnitude and type of force • The bone density is evaluated in the regions of the potential implant sites • The key implant positionsand the implant numberare selected • The next consideration is the implant size m.akouchekian

6. Biomechanical load management based on: • The character of the applied forces • The functional surface area over which the load is dissipated The implant size directly affects the functional surface area m.akouchekian

7. Character of forces applied to implantStress and strain • Although several conditions may cause crestal bone loss, one of these may be prosthetic overload. • Excessive loads on an osteointegrated implant may result in mobility of the supporting device, even after a favorable bone-implant interface has been obtained. m.akouchekian

8. Character of forces applied to implantStress and strain • Excessive loads on the implant result in increased strain in the bone • Microstrains on the bone may affect the bone remodeling rate ,which result in bone loss • The amount of bone strain is directly related to the amount of stress applied to the implant-bone interface m.akouchekian

9. Five distinct forces factors • Type • Magnitude • Duration • Direction • Magnification m.akouchekian

10. Force magnitude • The magnitude of bite force varies as a function of anatomical region and state of dentition(10 to 350 Ib) • The magnitude of force is greater in molar region, less in canine area and least inincisor region • The average bite forces increase with parafunction (approach 1000 Ib) m.akouchekian

11. Force duration • Under ideal condition, the teeth come together during swallowing and eating ( less than 30 minutes) • In parafunctional habits, teeth may be in contacts in several hours each day • Increase in force duration directly increases the risk of fatigue damage to cortical bone (e.g, shin splints in runners) m.akouchekian

12. Force duration • Although fatigue damage to alveolar bone has not yet been reported in the literature. • Roberts et al. Report: the bone around an implant may be remodeled at a rate of 500% each year after loading, compared with normal trabecular physiologic remodeling around a tooth of 20% to 40% per year • The dramatic increase in remodeling rates may eventually lead to fatigue damage and resultant bone IOSS. m.akouchekian

13. Force type • Three type of forces may be imposed on dental implants: • compression • tension • shear m.akouchekian

14. Force type • Bone is strongest when loaded in compression, 30% weaker when subjected to tensile and 65% weaker when loaded in shear m.akouchekian

15. Force type • An attempt should be made to limit shear forces on bone • Increased width of implant: • decrease offset loads and • Increase the amount of the implant-bone interface m.akouchekian

16. Force direction • The forces to an implant body are typically greatest at the crestal bone interface • Angled loads to the implant produce angled loads to the crest module of the implant • the direction of the load has a significant effect on the magnitude of compressive and lateral load components. m.akouchekian

17. Force direction • By increasing the angle of the load by only 6degrees , the lateral load is increased by 233% m.akouchekian

18. Force direction • Angled loads increase the amount of shear loads to the bone • The implant should be inserted perpendicular to the curve of wilson and spee • The anatomy of the mandible and maxilla places significant constraints • Bone undercuts further constrain implant placement and thus load direction imposed on the implant • The premaxilla is 12 to 15 degrees off the long axis of load • To decrease the effect of angled load on the implant , the implant may be increased in diameter m.akouchekian

19. Force magnification • Cantilevered prosthesis • Crown height greater than normal • Parafunction Force magnification increases the stress m.akouchekian

20. Force magnification • D4 bone may be more than 10 times weakerthan D1, and 70% weaker than D2 bone • Implant failure rates are 35% in D4 bone • The most important factor to decrease stress: • increase in implant number=> increases the effective surface area=> decreases stress • increase implant size m.akouchekian

21. Surface area • Stress = Force / Surface area • To decrease stress: • the force must decrease • surface area must increase • Increase in implant size is beneficial to decrease stress m.akouchekian

22. Rationale for longer implant length • The length of the implant is directly related to the overall implant surface area • A 10 mm cylinder implant: • increases surface area 30%> 7 mm implant • 20%< 13 mm long implant m.akouchekian

23. Rationale for longer implant length • A common axiom has been to place an implant as long as possible • The length of implant corresponds to the height of available bone The available • in the anterior mandible: • bone height is greater • Bite forces are lower • bone density is greater • The posterior have less bone height and the implant cannot engage the dense opposing cortical plate • ThePosterior maxilla associated with the highest failure rate because less height and less dense m.akouchekian

24. Rationale for longer implant length • Implants longer than 15 mm provide greater stability under lateral loading • Increasing the length beyond a certain dimension may not reduce force transfer proportionately. m.akouchekian

25. Rationale for longer implant length • The length of the implant in favorable bone quality and crown height may range from 10to 15 mm,and 12 is usually ideal • length of 12 mm:usually ideal under most patient force and bone density conditions • 15 mm :suggested in softer bone types m.akouchekian

26. Rationale for longer implant length • All implant lengths exhibited 80% to 100% of the stress in the crestal 40% of the implant length m.akouchekian

27. Disadvantages of longer implants • Overheating because preparation a longer osteotomy(D1,D2) • Threaded implant may not readily engage the denser bone of the apical cortical plate(D3,D4) • Implant threads may strip along the rest of osteotomy especially in D3 or D4 bone • Excessively long implants do not transfer stress to the apical region (most of the stresses are transmitted within the crestal 7 to 9 mm of bone ) • Advanced surgical procedures may be needed (nerve repositioning and sinus graft) • The apical end of implant will not benefit from the sinus bone graft m.akouchekian

28. Rationale for shorter implant length • The posterior region of jaws usually have the least height of existing bone and have higher bite forces • Under some clinical conditions, stresstransfer patterns may be similar between a short and a longer implant m.akouchekian

29. Advantages of short implants • Less bone grafting in height • Less time for treatment • Less cost for treatment • Less discomfort • Less surgical risk of : • Sinus perforation • Paresthesia • Osteotomy trauma from heat • Damage to adjacent tooth root • Surgical ease: • decreased inter arch spaces • Less inventory/ cost m.akouchekian

30. Disadvantage of short implants • In the majority of articles, implants 10 mm or smaller have increased failure rates • Implants shorter than 10 mm had a survival rate of 81.5% whereas longerimplants had higher than 95% m.akouchekian

31. Disadvantage of short implants • The failures associated with short implants, often occurred after prosthetic loading (especially within the first 12 to 18 months) • the surgical success was not affected by implant length m.akouchekian

32. Why the posterior short implants have higher failure rate • Higher bite forces • Low bone density in the region • Increased crown height • Implant design considerations m.akouchekian

33. IDEAL IMPLANT SIZE • The softer the bone: the greater the implant body length and diameter suggested m.akouchekian

34. m.akouchekian

35. Implant diameter • Over several decades, implants have gradually increased in wide(scialom wereless than 2 mm wide) • Branemark first introduced an implant body diameter of 3.75 mm • The larger diameter implants were primarily used to improve emergence profile • The wide diameter implant presents surgical, loading and prosthetic advantages m.akouchekian

36. Surgical advantages • Surgical rescue implant • Failed implant /immediate • Tooth extraction/immediate m.akouchekian

37. Loading advantages • Because occlusal stress to the implant interfere at concentrated at the crest of ridge , width appears more important than height • Increased surface area • Compensate unfavorable patient force factors • In cantilevers , reduce the risk of overload • Compensate for poor bone density • Enhance surface for short implants m.akouchekian

38. Prosthetic advantages • Improve emergence profile • Decrease screw loosening • Minimize component fracture • Facilitate oral hygiene(decrease interproximal space) m.akouchekian

39. Disadvantages of wide diameter implants • Bone trauma- drill sequence • Decreased facial bone thickness may lead to recession (Because closer than 1.5mm to the adjacent teeth or facial or palatal bone ) • Increased surgical failure rate • May too close to adjacent tooth, PDL encroachment • Stress shielding: the implant is so wide that strain may be too low to maintain bone m.akouchekian

40. In anterior:implant should not be wider than 5 mm • in the posterior:implant should not be greater than 6 mm(when adequate mesiodistal space is present and force magnitude is also observed) • When larger diameter implants can not be used in the molar region , two 4 mm implants for each molar should be considered m.akouchekian

41. Natural teeth • PDL complex is a very effective organ that distributes occlusal loads along the entire root surface • The smallest diameter roots are in the mandibular anterior region • The canines have a greater surface area than premolars, because they receive a lateral loads more than premolars m.akouchekian

42. Natural teeth • The maxillary molars have more roots than mandibular molars (because the maxillary posterior region has the least bone density) m.akouchekian

43. Natural teeth m.akouchekian

44. Anterior tooth replacement • The diameter of natural teeth in 2 mm below the CEJ. • the implant body should not be as wide as the natural tooth or clinical crown it replaces =>The emergence contour and interdentalpapilla can not be established properly • Implant should be at least 1.5mm from the adjacent teeth • When in doubt, smaller size diameter implant should be selected m.akouchekian

45. Multiple anterior implants • When implants are adjacent to each other, a minimum distance of 3mm is suggested • The size dimension of two adjacent anterior implants should most often be reduced compared with single implant m.akouchekian

46. Implant size selection criteria in posterior maxilla • The implant dimension should correspond to the natural tooth(2mm below the CEJ) • The implant should be at least 1.5 mm from the adjacent teeth • The implant should be at least 3 mm from adjacent implant • The implant should be at least 4 mm in diameter m.akouchekian

47. the mandibular incisors and the maxillary lateral incisor: 3- to 3.5-mm diameter • the maxillary anteriors, premolars in both arches,and canine:4-mm diameter implants • The molars:5- or 6-mm diameter • The implant dimension in question is the size of the crest module, not the implant body dimension m.akouchekian

48. The number of implants should be increased : • When the diameters of molar implants do not provide sufficient surface area • Very soft bone types • Unfavorable force factors (i.e, parafunction) • Multiple adjacent posterior teeth are missing m.akouchekian

49. For You’r Attention m.akouchekian