The Surface and Material of Dental Implants

Transcription

1 The Surface and Material of Dental Implants Conrado Aparicio, PhD Minnesota Dental Research Center for Biomaterials and Biomechanics Dpt. of Restorative Sciences. School of Dentistry University of Minnesota - Twin Cities apari003@umn.edu

2 Contents 1 st and 2 on generation of dental implants Microrough titanium dental implants Osseointegration Palmquist et al. Critique of dental implants New surfaces for dental implants Nanorough surfaces Superhydrophilic surfaces Chemical coatings Biocoatings New materials Summary Wennerberg et al. Junker et al. Aparicio et al. Chiapasco et al. Further recommended reading

3 Palmquist et al. (2010)

4 Dental Implant Restoration Implant is firmly fixed in the surrounding bone Abutment is attached to the implant body by abutment screw. Crown is cemented onto the abutment Adjacent teeth have not been affected Adapted from a slide courtesy of Dr. Osorio

5 Base(2)_pt1 Base(2)_pt2 C Atom % Osseointegration O Ca Direct structural and functional connection between ordered living bone and the surface of a load-carrying implant. Brånemark P-I, et al. (1977) Scand J Plast Reconstr Surg 11(supp 16), 1. P Ti 1.45 Au pt2 pt1 There is no progressive relative movement between the implant and the bone with which it has direct contact. Compare with Figure 3 in Palmquist et al. Brånemark P-I. (1983) 50,399 Depends on the ability of healing, repair, and remodeling of bone tissue around implant Ti Bone Work in collaboration with Dr. W-J Seong

6 Factors affecting osseointegration Albrektsson T and Jacobsson M (1987) J Prosthet Dent 60, Material of implant Macroscopic shape Surface quality Bone bed Surgical technique Loads applied Commercially Pure Titanium Biocompatible Appropriate mechanical properties Adequate strength Low Elastic modulus Excellent corrosion resistance 1st Generation of dental Implants

7 Factors affecting osseointegration Material of implant Macroscopic shape Surface quality Bone bed Surgical technique Loads applied Albrektsson T and Jacobsson M (1987) J Prosthet Dent 60, Naturally, titanium is coated with stable layer of TiO 2 Rough Surfaces mechanical interlocking Hydroxyapatite Plasma-Sprayed Coatings Bioactivity Image adapted from Bjursten L-M (1991). In: Rydevik B et al, editors. Int. Workshop on Osseointegration in Skeletal Reconstruction and Joint Replacement. Göteborg, Sweden, p. 25.

8 Dental Implant Surface Modifications to Improve Osseointegration Schliephake H. and Scharnweber D. J Mater Chem (2008) 18, 2404

9 Surface Topography Modification Several approaches have been used to optimize the surface topography (microroughness and micro/nanoroughness) in order to improve the bonematerial integration, among them: Acid etching Particle Blasting Electrochemical Combinations Wennerberg and Albrektsson (2009) Osseotite TiOBlast TM SLA TM TiUnite TM Roughness, R a 1-4 m 2 on Generation of dental Implants Pictures courtesy of Biomet3i, AstraTech, Straumann, Nobel Biocare

10 SHOCKING!!! Further, somewhat surprisingly, there is yet not enough hard evidence (randomized clinical trials) to tell whether the second generation of implants has a better clinical performance than the machined implants used earlier. Palmquist et al. (2010)

11 HOWEVER experimental evidence from in vitro and in vivo studies strongly suggests that some types of surface modifications promote a more rapid bone formation than do machined surfaces. This could depend on an altered surface chemistry and/or an increased texture on the micrometre scale. Palmquist et al. (2010)

12 Implants critique Microrough titanium implants - Very successful (95-97 % after years in normal patients and surgical situations) BUT Need of improvement for immediate loading and compromised bone conditions trauma, infection, systemic disease, lack of bone volume, elderly patients, smokers -Buser D. In Titanium in Medicine (2001) Schiliephake H et al. J Mater Chem (2008) 18, 2414

13 Is it possible? Recent studies on early osseointegration (hours days) have demonstrated that the upregulation of genes responsible for bone formation ALP and OC was coupled with upregulation of genes expressed by osteoclasts indicating that the bone remodelling phase is triggered much earlier than what has previously been assumed. Taken together, results suggest that active bone resorption and bone formation are processes taking place over a wide time range and starting already during the first days after implantation. Indeed, studies evaluating the gene expression of interfacial cells in combination with other structural and biomechanical data, also at later time points, are needed to further explore the role of early interfacial events for longterm functional performance of the implant. Palmquist et al. (2010)

14 Implants critique Other non bone-related complications leading to implant failure Difficulties for achieving permucosal sealing. Soft tissue healing is compromised. Peri-implantitis (might be as high as 14%). Bacteria colonization of implant surface. More prevalent in coronal part of the implant. Leads to immflation and thus, loss of bone. Norowski and Bumgardner (2009) J Biomed Mater Res B 88B, 530 Picture courtesy of BioHorizons

15 Is this important? More implants with rough surfaces were affected by periimplantitis (RR 0.80; 95% CI ) meaning that turned implant surfaces had a 20 per cent reduction in risk of being affected by peri-implantitis over a 3 year period (figure 4). Based on the available results of RCTs, there is limited evidence showing that implants with relatively smooth (turned) surfaces are less prone to lose bone owing to chronic infection (peri-implantitis) than implants with rougher surfaces. On the other hand, there is no evidence showing that any particular type of dental implant has superior long-term success. These findings are based on a few RCTs, often at high risk of bias, with few participants and relatively short follow-up periods. Palmquist et al. (2010)

16 Titanium is not bioactive Surface-related issue!! Kasemo B. Surf Sci (2002) 500, 656

17 Wennerberg and Albrektsson (2009)

18 New Dental Implants Surfaces Nanoroughness (All) Hydrophilicity (SLActive, Straumann) Chemical changes Fluoride (Osseospeed, AstraTech) Calcium Phosphates (Nanotite, Biomet, 3i)

19 Micro- NANO-roughness Recent studies also show that surfaces with nanoscale features show additional biological effects in vitro and in vivo, e.g. by producing an integration. Palmquist et al. (2010) J Biomed Mater Res A 92A, 1476 Aparicio, C. et al. (2007) J Biomed Mater Res A 82A, 521 Such surfaces,intentionally modified with respect to microscale and nanoscale features, may represent the next generation of oral implant systems. Palmquist et al. (2010)

20 An important question Microroughness Physicochemical Effects Nanoroughness Wennerberg and Albrektsson (2009)

21 Nanopattern!! Rationale?

22 Micro- NANO-roughness Micro- and Nano-fabricated surfaces have not reached the clinical evidence stage, yet. Palmquist et al. (2010) Aparicio, C. et al. (2007) J Biomed Mater Res A 82A, 521

23 An important question Microroughness Physicochemical Effects Nanoroughness Wennerberg and Albrektsson (2009)

24 Dental Implant Surface Modifications to Improve Osseointegration Schliephake H. and Scharnweber D. J Mater Chem (2008) 18, 2404

25 Superhydrophilic Surfaces

26 Ultrahigh wettability/surface free energy SLActive TM -Straumann Blasted + etched + plasma cleaning? + N 2 - protecting atmosphere until storage in vial with saline water Increase in protein adsorption and healing factors Rupp F et al. (2006) J Biomed Mater Res A 76A, 323

27 Ultrahigh wettability/surface free energy SLActive TM -Straumann Superhydrophilic surfaces will attract blood and thus, all biological components that blood incorporates? It has to be something more than nanoroughness. Blasted + etched + plasma cleaning? + N 2 - protecting atmosphere until storage in vial with saline water Increase in protein adsorption and healing factors Rupp F et al. (2006) J Biomed Mater Res A 76A, 323

28 Dental Implant Surface Modifications to Improve Osseointegration Schliephake H. and Scharnweber D. J Mater Chem (2008) 18, 2404

29 F-containing Surfaces

30 F-incorporated fast integration surface OsseoSpeed TM -AstraTech F incorporated in oxide layer with a hydrofluoric acid etching Increases hydrophilicity of the surface

31 F-incorporated fast integration surface OsseoSpeed TM -AstraTech Hydrophilicity? F stimulates bone growth as stimulates remineralization of teeth? Nanoroughness? F incorporated in oxide layer with a hydrofluoric acid etching Increases hydrophilicity of the surface

32 Calcium-Phosphate Coatings

33 Crystaline CaP nanophase of titanium Nanotite Biomet 3i 14 m 2,5 m 800 nm Discrete nanocrystals of calcium phosphate adsorbed on the surface of the implant. Confusing information about the method for adsorption: direct on Ti surface, or after silanization (APTES), or after chitosan deposition?

34 Crystaline CaP nanophase of titanium Nanotite Biomet 3i 14 m 2,5 m 800 nm Nanoroughness? Hydroxyapatite, the mineral in bone is a calciumphosphate. Calcium-phosphates will signal cells to grow bone. Discrete nanocrystals of calcium phosphate adsorbed on the surface of the implant. Confusing information about the method for adsorption: direct on Ti surface, or after silanization (APTES), or after chitosan deposition?

35 Research evidence? According to Junker et al. (2009) animal experiments showed better integration of dental implants with this new surfaces (Osseospeed, SLActive, Nanotite) at EARLY stages than their previous counterparts.

36 Clinical success? For two new implant surfaces, Nanotite and SLActive, the PubMed search exhibited a minimal number of reports. Most of the results for these two were preclinical and in vitro studies, with few relevant Randomized Clinical Trials (one for SLActive; none for Nanotite). This is not unusual, given that both these surfaces have been just recently introduced in the market, and reflect ongoing research, which has not yet been published in a peer-reviewed journal. Bhatavadekar, N (2010) Int Dental J 60, 359

37 An alternative: Aparicio et al. (2011)

38 Aparicio et al. (2011) What is unique? What is the most important conclusion? Are there any group control missing?

39 Biomimetic inorganic surface modification Aparicio et al. J Biome Mater Res (2008); Aparicio et al. (2010)

40 Biomimetic inorganic surface modification Aparicio et al. J Biome Mater Res (2008); Aparicio et al. (2011)

41 Biomimetic inorganic surface modification Aparicio et al. J Biome Mater Res (2008); Aparicio et al. (2011)

42 Bio-Inspired Coatings Synthetic molecules that mimic biomolecules know to be biologically active for mineralization, cell recruitment, cell differentiation, bone growth, soft tissue growth, antimicrobial They can be combined to target different bioactivities in the same surface

43 Dental Implant Surface Modifications to Improve Osseointegration Incorporation of biologically active molecules Schliephake H. and Scharnweber D. J Mater Chem (2008) 18, 2404

44 The future!! Although the clinical success of monolayer modified implants remains to be demonstrated, it can be anticipated that different types of monolayer coatings with, for example, proteins or other biologically active substances designed to target specific biological mechanisms and signalling pathways will be a strong line of development towards the next generation of implants. Palmquist et al. (2010)

45 Alternatives to Titanium Aestethics Zirconia, ZrO 2 Narrow diameters: Ti6Al4V TiZr - Roxolid, Straumann Trabecular metal: Tantalum+Ti6Al4V, Zimmer

46 Zirconia implants

47 Mechanical properties of some ceramics used in dentistry c.p. Titanium s fracture toughness is near 40 MPa. m 1/2 Zirconia (Y-TZP) is still too brittle and degrades with time

48 TiZr alloy Roxolid by Straumann for small diameter implants J. Gottlow, M. Dard, F. Kjellson, M. Obrecht, L. Sennerby. Academy of Osseointegration, 23rd Annual Meeting, Boston, MA, February 28 March 1, 2008; Abs OS-5.

49 Chiapasco et al. (2011) CONCLUSION: Within the limits determined by the small patient and implant sample, and the short follow-up, preliminary results obtained in this study seem to demonstrate that narrow diameter (3.3 mm) implants fabricated with a titanium zirconium alloy may predictably bear the mechanical stresses generated by occlusal loading and masticatory function in the lateral-posterior areas of the jaws and/or in case of complete prosthetic rehabilitations.

50 Chiapasco et al. (2011). Discussion More recently, some studies proposed the use of narrow diameter implants also in the posterior areas of the jaws or in totally edentulous patients, as an alternative treatment option to horizontal bone reconstruction/regeneration, reporting implant survival rates consistent with those published for standard diameter implants

51 Chiapasco et al. (2011). Discussion However, caution has been suggested in the interpretation of these results and in the use of narrow diameter implants in cases of high occlusal loading, such as fixed rehabilitations of the posterior sectors of the jaws or prosthetic rehabilitation of totally edentulous jaws, due to the risk of fatigue fracture of traditional titanium implants, as reported in some studies.

52 Ta Trabecular Metal Implant Issues?

53 Summary What s new? Nanoroughness Some in the market, still research Superhydrophilic surfaces Some in the market, still research Calcium-phosphate coatings Some in the market, some almost there Bio-inspired coatings Research Antimicrobial coatings Research Promoting permucosal sealing Research

54 Recommended further reading Schliephake and Scharnweber (2008) Chemical and biological functionalization of titanium for dental implants. J. Mater. Chem. 18, Kim et al. (2008) Biomimetic Approach to Dental Implants. Current Pharm Design 14, Bhatavadekar (2010) Helping the clinician make evidence-based implant selections. A systematic review and qualitative analysis of dental implant studies over a 20 year period. Int Dental J 60, 359=369 Norowski and Bumgardner (2009) Biomaterial and Antibiotic Strategies for Peri-implantitis. J Biomed Mater Res Part B: Appl Biomater 88B:

55 Thanks for your attention!