functional basis of dental implants.pptx

functional basis of dental implant

1. Functional Basis for Dental Implant Design Dr. Bhavin Patil PG 2 nd Year

2. Contents Introduction Function and implant design Factors affecting the implant Implant geometry Implant features Implant materials Conclusion References

3. Introduction Implant design Refers to the 3D Structure of the implant With all the element and Characteristics that compose it Dental implants are subjected to various forces direction & magnitude during function. Dental implant designs have progressed from early sub periosteal, blade type, and press-fit cylinder implants to the straight and tapered threaded implants of today. Their design remains an area of intense activity even now

4. Dental Implant Therapy : Widely accepted for restoration in edentulous patients. Treatment planning considers prosthesis type, bone density, occlusion, function, bone volume, and medical factors. Compromising Factors and Mitigation : Factors: Compromised bone density, large occlusal loads, parafunction. Mitigation: Bone grafting, lateral compression with osteotomes, implant site localization with prosthesis design, and use of specialized implants. Implant Design Evolution : Progression from press-fit blade designs to press-fit cylinders, and now to straight and tapered threaded implants. Press-fit cylinders: Easy to place but lower primary stability and bone-implant contact. Press-fit blade implants: Easier placement in thin alveolar crests, avoids bone grafting.

5. Osseointegration and Long-Term Success : High osseointegration success rates before loading, but long-term functional success can be lower. Common complication: Marginal bone loss after uncovering/loading. Study: 28% of patients at Brånemark Clinic showed progressive bone loss. Factors Influencing Implant Failure : Bone quality, implant diameter, and length affect failure rates. Softer bone, smaller diameter, and shorter implants show higher failure rates due to inadequate support. Implant Survival and Bone Maintenance : Success rates vary significantly between implant designs. Malmqvist et al.: 37.2% success rate for Core-Vent Implants. Albrektsson et al.: 10.7% failure rate for Nobel Direct implants after 1 year. Ormianer et al.: Marginal bone loss study with different thread designs showed mean bone loss between 1.90 and 2.02 mm.

6. Fig. 3.1 Illustration of the macro features of a contemporary dental implant . (Image courtesy of Glide well Dental, Newport Beach, California)

7. Function and Implant Design Dental implants provide support for the prosthesis and transfer the occlusal forces to the supporting bone. The transfer of the forces is determined by the resultant force transferred from the prosthesis to the implant And amount of implant area available to transfer the force to the supporting bone. Implants are designed to combine the features that are robust for their intended purpose

8. FACTORS AFFECTING THE IMPLANT DESIGN Force Type Force Magnitude Force Direction Force Duration

9. Force Type Bone response to occlusal forces varies with the magnitude and the direction of the forces applied. Mainly 3 Different type of forces Compressive :- Occlusal forces along the axis of the implant. Tensile & Shear :- They are due the force applied in transverse direction.

10. Ability of Bone to resist the various type of forces . Compressive Force > Tensile Force > Shear Force Load transfer to the supporting bone is most efficiently accomplished by the implant surfaces perpendicular to the axis of the implant. Implant surfaces that are not perpendicular or parallel to the implant axis will transfer shear forces, along with compressive and tensile forces, to the supporting bone.

11. Force Magnitude Unless a force of 50 microstrainis applied on a routine basis to the bone, it will begin to resorb. Material used for the implant must be of stiffness that is not a great deal higher than that of bone in order to adequately transfer an applied force to the bone. Ceramics are too stiff and will therefore not transmit the force adequately to the bone causing stress shielding of the bone. Titanium, on the other hand, has a modulus of elasticity of approx. 100 GPa(closer to that of bone = 20 GPa; although still high) …… physiologic loading of bone.

12. Force Direction Forces that diverge from the axis of the implant, the load-bearing capabilities of the supporting bone are compromised. The non isotropic behavior of bone under different loading conditions further exacerbates the adverse effect of angled loads of bone. The greater the divergence of the direction of the load from the implant axis, the greater the stresses at the implant-bone interface. Ideally, the implant should be placed with the implant axis loaded as near to vertical as possible Prosthesis design, such as the avoidance of excessive distal cantilevers, minimizes non axial load transfer to the implant and supporting bone.

13. Force Duration Duration of Bite Forces : Teeth come together briefly during swallowing and eating under ideal conditions. Sheppard et al. study: No tooth contact during most of mastication. Approximately 19.5% of mastication time involves possible tooth contacts for three foods. Total time of tooth contact during mastication is estimated to be less than 30 minutes per day. Bruxism : Increases force duration. Contributing factor to dental implant and prosthetic complications. Contributes to dental implant failure.

14. Implant Geometry Implant Shape Implant Diameter Implant Length

15. Implant Shape Geometric features that extend outward from the axis of the implant transfer stresses to the surrounding bone.

16. The shape of the implant determines the surface area available for stress transfer and governs the initial stability of the implant. Inc. BIC  dec. stress on the bone The transmission of occlusal forces to the supporting bone can be variable as per the area beneath the alveolar crest. Force transfer is not uniform across crestal and trabecular bone. Crestal bone stresses are highest when crestal bone thickness is less than 2 mm. Implant design in cortical area and crestal area dictates force transmission in there respective region.

17. Tapered VS Parallel Vandamme et al. Study : Conclusion: Well-controlled immediate implant loading accelerates tissue mineralization at the bone-implant interface. Adequate bone stimulation via mechanical coupling results in a larger bone response around screw-type implants compared to cylindrical implants. Ormianer and Palti Study : Found that tapered implants maintained crestal bone levels even in compromised conditions. Concerns about tapered implants being more prone to crestal bone loss than cylinder designs were unsupported. Atieh et al. Review : Reviewed implant stability of tapered and parallel-walled dental implants. Found greater implant stability at insertion and after 8 weeks for tapered implants Failure rates were not significantly different between tapered and parallel-walled implants. Marginal bone loss was significantly less for tapered implants compared to parallel-walled implants.

18. Influence of Implant Diameter Increased Surface Area : Larger diameter implants increase surface area for force transfer to bone. Better resistance to occlusal forces, especially in the molar region. Clinical Studies : Krennmair et al.: Failure rates for CAMLOG tapered implants: 3.7% (3.8mm), 1.4% (4.3mm), 1.0% (5/6mm). No difference in peri-implant marginal bone resorption. Javed and Romanos: Implant diameter has a secondary role in long-term survival; key factors are surgical protocol, primary stability, and oral hygiene.

19. Implant Diameter and Stress Distribution Stress at Bone-Implant Interface : Wider implants decrease stress; smaller diameter implants show increased stress. Stress = Force / Cross-sectional area; wider implants have more surface area, thus lower stress. Resistance to Fracture : Wider implants are more resistant to occlusal overload and fatigue fractures. Abutment screw bore increases stress; wider implants still have greater wall thickness and fracture resistance.

20. Implant Diameter And Length

21. Implant Length Implant length is the dimension from the platform to the apex of implant. Most common lengths are between 8 and 13 mm. The significance in increased implant length or its ability to achieve osseointegration is not found at the crestal bone interface. The increased length can provide resistance to torque or shear forces when abutments are screwed into place. Greater implant length is beneficial in decreasing stress and strain in the supporting bone; However, a larger implant diameter is more effective ,Implant length alone may be insufficient to compensate for diameter, particularly if bone quality is poor.

22. Implant Features Implant Collar Implant Prosthetic Connection Implant Threads Implant Apical Region

23. Implant Collar Connects prosthesis to implant body, influencing stress distribution and tissue interface. It is a major determinant for the overall implant design, because it has: I.-Surgical influence II.-Bacterial plaque concern III.-Biological width influence IV.-Loading profile consideration Connects prosthesis to implant body, influencing stress distribution and tissue interface.

24. Implant Collar Supragingival Design: Protrudes above gingival tissue, smooth surface, larger diameter than implant body. Minimal need for healing abutments and tissue-forming components. Bone-Level Design: Subgingival considerations, possible supracrestal contact with gingival tissue. Smooth surface preferred to minimize peri-implantitis risk during epithelial wound healing.

25. Crestal Bone Interaction : Larger collar surface area reduces stress at crestal bone level. Subcrestal implants and taper in collar increase stress in crestal bone. Microthreads : Help maintain marginal bone levels by distributing stress in cortical bone. Microthreads result in perpendicular stress distribution, reducing shear stress. Animal studies show higher bone-implant contact with microthreaded implants. Platform Switching : Abutments with smaller diameter than implant collar preserve marginal bone levels. Shifts stress concentration away from cervical bone-implant interface. No conclusive microbiota differences, but significant effect on marginal bone preservation

26. Mechanism of platform switching a. Inward positioning of the implant‑abutment interface allowed the biologic width to be established horizontally, as an additional horizontal surface area is created for soft tissue attachment. b. The PS design increases the distance between the inflammatory cell infiltrate at the micro gap and the crestal bone, thereby minimizing the effect of inflammation on marginal bone remodeling. c. Reduction in stresses, especially in the crestal region, by shifting the stresses away from the bone-implant interface.

27. Biologic width & transitional zone The transition zone represents the area between the prosthetic crown and the implant.

28. Implant Prosthetic Connection

29. Implant Prosthetic Connection There are many different designs for implant-abutment prosthetic connections. External Connection . Internal Connection. External prosthetic connections, mostly hexagonal, place the connection external to the implant body. Internal implant connections have the connection geometry inside the implant body.

30. Functions : Junction between implant and prosthesis. Transmits insertion forces for implant placement. Orients prosthetic component geometry. Must withstand clinically relevant forces . Influence of Design : Implant diameter and cross-section affect connection strength. Abutment screw is crucial for stability and strength .

31. Evolution of Prosthetic Connections External Connections : First widely used on screw-type implants. Brånemark external hex design: 0.7-mm-tall external hex. Ideal for edentulous arch restoration, less so for single-crown or partially edentulous restorations. Subject to lateral loading; increased height interferes with angled abutments . Internal Connections : Developed to address complications of external hex in partially edentulous cases. Early design: Internal hex below a 45-degree lead-in bevel. Mitigated issues with angled abutments and improved stability, reducing screw loosening .

32. Conical internal connection Design and Features : Conical implant connections are positioned deeper within the implant body. The angle of the abutment interface is smaller, enhancing stability, fit, and seal performance. Peri-Implant Bone Loss : Caricasulo et al. found that conical connections have lower peri-implant bone loss in the short to medium term compared to external connections. Finite Element Analysis (FEA) by Quaresma et al. : Comparison between internal hexed and conical connection implants. Conical connection implants showed lower stresses on alveolar bone and prosthesis,

33. Advantages of Conical Connections : Provides a stable abutment connection. Exhibits lower peak bone stresses when placed at the marginal bone level. Shows high resistance to axial loads. Clinical Implications : Conical prosthetic connections enhance overall implant performance. Effective for reducing peri-implant bone loss and distributing stress efficiently.

34. Thread Geometry Threads on an implant body are designed to maximize initial fixation and bone contact, enhance surface area, and facilitate dissipation of loads at the bone-implant interface.

35. Thread Geometry

36. Thread Shape

37. Thread shape is geometric characteristic that has bearing on the distribution of forces into the supporting bone. In conventional engineering applications, the V-thread design is called a fixture and is primarily used for fixating metal parts together. original Brånemark implant of Nobel Bio Care was called a “fixture” rather than being referred to as an implant. The buttress thread shape was initially designed for pullout loads by Krupp The square thread (called a power thread in engineering) provides an optimized surface area for intrusive, compressive load transmission.

38. Thread Shape The V-shaped and buttress thread shapes had similar BIC percent. The square thread had the highest BIC percent. Thread shape may also be a parameter in an implant design for the initial healing phase.

39. Thread Depth

40. Thread depth directly affects the compressive load-bearing surface of the implant thread. The deeper the thread, the larger the surface area available for stress transmission. Increasing thread depth also increases the insertion torque and primary stability in low-density bone. In denser bone the increased insertion torque of implants with greater thread depth may require the use of a bone tap. If implant becomes wider, the depth of the thread increases without decreasing the body wall thickness.

41. Thread Pitch

42. The height of the threaded portion of the implant body divided by the pitch equals the threads per unit length. The smaller (or finer) the pitch, the more threads on the implant body, if all other factors are equal. The thread pitch may be used to help resist the forces to bone with poorer quality. The thread pitch may be decrease to increase the thread number and increase the functional surface area.

43. Implant Apical Region The apical region of the implant has features to facilitate insertion. The tip of the implant is tapered to allow some of the axial length of the implant to enter the implant site before the threads come into contact. The implant taper typically matches the apical portion of the implant drill used to prepare the hole.

44. The apical end of conventional implants should be flat to rounded in shape to minimize the probability of perforating sinus. The apical end on small-diameter implants typically tapers to a sharp point to advance into the bone. More often the apical region of the implant incorporates flat region or grooves circumferentially arranged on the implant body.

45. Implant Materials Materials suitable for dental implants and their prosthetic components must meet several specific criteria. The material must be biocompatible The material must have sufficient tensile & compressive strength. The material should have excellent fatigue resistance and fracture toughness. Corrosion resistance and modulus of elasticity should be as close to as to that of the surrounding bone.

46. Biocompatibility A number of materials are suitable for dental implants from a biocompatibility standpoint of view. commercially pure titanium, titanium alloys, and zirconia (zirconium dioxide, ZrO2) ceramic implants. Commercially pure titanium has the longest history of use for dental implant applications. The most often used titanium alloy is grade 5 titanium, which contains 6% aluminium and 4% vanadium as alloying elements.

47. Strength Tensile, compressive, and fatigue strength properties vary between commercially pure titanium, titanium alloy, and zirconia ceramic materials. Titanium and titanium alloy specifications are defined in ASTM International specification B348

48. Zirconia has much larger compressive strength than titanium; however, it has relatively poor tensile strength, and it is vulnerable to bending loads. Titanium and zirconia implant materials have sufficient ultimate strength to resist clinically relevant loads provided the implant cross section is sufficient. Implants fail because of fatigue fractures than from loads that exceed the ultimate strength of the material. Fatigue strength is affected to a large degree by loading conditions such as cantilever length, force direction.

49. Corrosion Resistance Titanium and its alloys have outstanding corrosion resistance under physiologic environmental conditions. They spontaneously form a passive titanium oxide passive film at the surface that resists corrosion very well. Zirconia ceramic is essentially inert in the oral environment and not susceptible to metallic corrosion.

50. Modulus of Elasticity When the modulus of elasticity of the implant and the surrounding bone are not matched, the stress transfer between the implant and the bone is compromised. The mean modulus of elasticity (a measure of stiffness) of dense cortical bone is approximately 16GPa. Whereas Mean Modulus of elasticity for Grade 4 Titanium alloy is ( 105GPa) Grade 5 Titanium alloy(Ti-6Al-4V)y is (109GPa) Grade 23 (Ti-6Al-4V ELI) (114 GPa). Zirconia ceramic is very stiff (200 GPa)

51. Conclusion Clinicians should choose implants based on scientific data rather than advertisement. The Rationale should be taken into consideration for every implant before using it.

52. References Dental Implant Prosthesis , Carl E.Misch 4 th Edition. Preeti Yadav et al. Implant Design and Stress Distribution , International Journal of oral implantology & clinical research, May-August 2016; 7(2) : 34-39. Implant thread designs: An overview. The Implant Supracrestal Complex and Its Significance for Long-Term Successful Clinical Outcomes December 2020International Journal of Prosthodontics DOI:10.11607/ijp.7201IF: 2.1 Q2 Biological Responses to the Transitional Area of Dental Implants: Material- and Structure-Dependent Responses of Peri-Implant Tissue to Abutments Materials 2020, 13(1), 72; https://doi.org/10.3390/ma13010072

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