Osseointegration

Osseointegration derives from the Greek osteon, bone, and the Latin integrare, to make whole. The term refers to the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant. Osseointegration has enhanced the science of medical bone and joint replacement techniques.

Definition

Osseointegration is also defined as : "the formation of a direct interface between an implant and bone, without intervening soft tissue".^[1] Osseointegrated implant is a type of implant defined as "an endosteal implant containing pores into which osteoblasts and supporting connective tissue can migrate".^[2] Applied to oral implantology, this thus refers to bone grown right up to the implant surface without interposed soft tissue layer. No scar tissue, cartilage or ligament fibers are present between the bone and implant surface. The direct contact of bone and implant surface can be verified microscopically.

Osseointegration may also be defined as :

1. Osseous integration, the apparent direct attachment or connection of osseous tissue to an inert alloplastic material without intervening connective tissue.
2. The process and resultant apparent direct connection of the endogenous material surface and the host bone tissues without intervening connective tissue.
3. The interface between alloplastic material and bone.

History

Titanum implant (black) integrated into bone (red): Histologic section

In 1952, Per-Ingvar Brånemark of Sweden conducted an experiment where he utilized a titanium implant chamber to study blood flow in rabbit bone. At the conclusion of the experiment, when it became time to remove the titanium chambers from the bone, he discovered that the bone had integrated so completely with the implant that the chamber could not be removed. Brånemark called the discovery "osseointegration," and saw the possibilities for human use.

In dental medicine the implementation of osseointegration started in the mid-1960s as a result of Brånemark's work.^[3][4][5][6] In 1965 Brånemark, who was at the time Professor of Anatomy at the University of Gothenburg, placed dental implants into the first human patient - Gosta Larsson. This patient had a cleft palate defect and required implants to support a palatal obturator. Gosta Larrson died in 2005, with the original implants still in place after 40 years of function.^[7]

In the mid-1970s Brånemark entered into a commercial partnership with the Swedish defense company Bofors to manufacture dental implants and the instrumentation required for their placement. Eventually an offshoot of Bofors, Nobel Pharma, was created to concentrate on this product line. Nobel Pharma subsequently became Nobel Biocare.^[7]

Brånemark spent almost 30 years fighting the scientific community for acceptance of osseointegration as a viable treatment. In Sweden he was often openly ridiculed at scientific conferences. His university stopped funding for his research, forcing him to open a private clinic to continue the treatment of patients. Eventually an emerging breed of young academics started to notice the work being performed in Sweden. Toronto's Professor Zarb, a Maltese dentist working in Canada, was instrumental in bringing the concept of osseointegration to the wider world. The 1983 Toronto Conference is generally considered to be the turning point, when finally the worldwide scientific community accepted Brånemark's work. Today osseointegration is a highly predictable and commonplace treatment modality.^[7]

More recently the procedure has been introduced for cranial and maxillofacial reconstruction as well.

Applications

• Dental implants, including Mini dental implants, are by far the main field of application
• Retention of a craniofacial prosthesis such as an artificial ear (ear prosthesis), eye (orbital prosthesis), or nose (nose prosthesis)
• Bone anchored hearing conduction amplification (Bone Anchored Hearing Aid)
• Knee and joint replacement

Theories

Two theories regarding the chemical mechanism by which endosteal implants integrate with bone have been proposed. Osseointegration, as defined above. That type of integration contrasts with fibrosseous integration, in which soft tissues such as fibers and/or cells are interposed between the two surfaces.^[8][9]

Brånemark’s theory of osseointegration

Brånemark proposed that implants integrate such that the bone is laid very close to the implant without any intervening connective tissue. The titanium oxide permanently fuses with the bone, as Brånemark showed in 1950s.

Weiss' theory of fibro-osseous integration

Weiss' theory states that there is a fibro-osseous ligament formed between the implant and the bone and this ligament can be considered as the equivalent of the periodontal ligament found in the gomphosis. He defends the presence of collagen fibres at the bone-implant interface. He interpreted it as the peri-implantal ligament with an osteogenic effect. He advocates the early loading of the implant.

Osseointegration versus Biointegration

In 1985, Dr. C. de Putter proposed two ways of implant anchorage or retention as mechanical and bioactive. Mechanical retention can be achieved in cases where the implant material is a metal, for example, commercially pure titanium and titanium alloys. In these cases, topological features like vents, slots, dimples, threads (screws), etc. aid in the retention of the implant. There is no chemical bonding and the retention depends on the surface area: the greater the surface area, the greater the contact.

Bioactive retention can be achieved in cases where the implant is coated with bioactive materials such as hydroxyapatite. These bioactive materials stimulate bone formation leading to a physico-chemical bond. The implant is ankylosed with the bone.

Technique

For osseointegrated Dental implants, metallic, ceramic, and polymeric materials have been used,^[2] in particular titanium.^[10] To be termed osseointegration the connection between the os and the implant needs not be 100 per cent, and the essence of osseointegration derives more from the stability of the fixation than the degree of contact in histologic terms. In short it represents a process whereby clinically asymptomatic rigid fixation of alloplastic materials is achieved, and maintained, in bone during functional loading.^[11] When osseointegration occurs, the implant is tightly held in place by the bone. The process typically takes several weeks or months to occur which is well enough for the implant dentist to complete the restorations. The fact is that the degree of osseointegration of implants is a matter of time. First evidence of integration occurs after a few weeks, while more robust connection is progressively effected over the next months or years.^[12] Though the osseointegrated interface becomes resistant to external shocks over time, it may be damaged by prolonged adverse stimuli and overload, which may result in implant failure.^[13][14] In studies performed using 3M™ ESPE™ MDI Mini dental implants, it was noted that the absence of micromotion at the bone-implant interface was necessary to enable proper osseointegration.^[15] Further, it was noted that there is a critical threshold of micromotion above which a fibrous encapsulation process occurs, rather than osseointegration.^[16] Already Brånemark stated that the implant should not be loaded and left out of function during the healing period for osseous integration to occur.

Other complications may arise even in the absence of external impact. One issue is the growing of cement.^[17] In normal cases, the absence of cementum on the implant surface prevents the attachment of collagen fibers. This is normally the case due to the absence of cementum progenitor cells in the area receiving the implant. However, when such cells are present, cement may form on or around the implant surface, and a functional collagen attachment may attach to it.^[18]

Advances in materials engineering: metal foams

Since 2005, a number of orthopedic device manufacturers have introduced products that feature porous metal construction.^[19][20][21] Clinical studies on mammals have shown that porous metals, such as titanium foam, may allow the formation of vascular systems within the porous area.^[22] For orthopedic uses, metals such as tantalum or titanium are often used, as these metals exhibit high tensile strength and corrosion resistance with excellent biocompatibility.

The process of osseointegration in metal foams is similar to that in bone grafts. The porous bone-like properties of the metal foam contribute to extensive bone infiltration, allowing osteoblast activity to take place. In addition, the porous structure allows for soft tissue adherence and vascularization within the implant. These materials are currently deployed in hip replacement and knee replacement surgeries.

See also

• Mini dental implants
• Osseoincorporation
• Abutment (dentistry)
• Dental implant
• Periodontology
• Oral and maxillofacial surgery
• Oral Surgery
• Prosthesis
• Dentistry
• European Association for Osseointegration
• British Society of Oral Implantology

Notes and References

1. ^ Miller, Benjamin F.; Keane, Claire B. (1992). Encyclopedia and dictionary of medicine, nursing, and allied health. Philadelphia: Saunders. ISBN 0-7216-3456-7. ^{[page needed]}
2. ^ ^{a b} Mosby's medical, nursing, & allied health dictionary. St. Louis: Mosby. 2002. p. 1240. ISBN 0-323-01430-5. 
3. ^ Brånemark PI (September 1983). "Osseointegration and its experimental background". The Journal of Prosthetic Dentistry 50 (3): 399–410. doi:10.1016/S0022-3913(83)80101-2. PMID 6352924. 
4. ^ Brånemark, Per-Ingvar; Zarb, George Albert; Albrektsson, Tomas (1985). Tissue-integrated prostheses: osseointegration in clinical dentistry. Chicago: Quintessence. ISBN 978-0-86715-129-9. ^{[page needed]}
5. ^ Albrektsson, Tomas; Zarb, George A. (1989). The Branemark osseointegrated implant. Chicago: Quintessence Pub. Co. ISBN 978-0-86715-208-1. ^{[page needed]}
6. ^ Beumer, John; Lewis, Steven (1989). The Branemark implant system: clinical and laboratory procedures. St. Louis: Ishiyaku EuroAmerica. ISBN 0-912791-62-4. ^{[page needed]}
7. ^ ^{a b c} Close to the Edge - Brånemark and the Development of Osseointegration, edited by Elaine McClarence, Quintessence 2003.
8. ^ Bernard, George W.; Carranza, Fermin A.; Jovanovic, Sascha A., eds (1996). "Biological Aspects of Dental Implants". Clinical periodontology. Philadelphia: Saunders. p. 687. ISBN 0-7216-6728-7. 
9. ^ Weber HP, Cochran DL (January 1998). "The soft tissue response to osseointegrated dental implants". The Journal of Prosthetic Dentistry 79 (1): 79–89. doi:10.1016/S0022-3913(98)70198-2. PMID 9474546. 
10. ^ Natali, Arturo N., ed (2003). Dental biomechanics. Washington, DC: Taylor & Francis. pp. 69–87. ISBN 978-0-415-30666-9. 
11. ^ Zarb, George A.; Albrektsson, Tomas (1991). "Osseointegration: A requiem for the periodontal ligament?". International Journal of Periodontology and Restorative Dentistry (11): 88–91. 
12. ^ Albrektsson, Tomas; Berglundh, Tord; Lindhe, Jan (2003). "Osseointegration: Historic Background and Current Concepts". In Lindhe, Jan; Karring, Thorkild; Lang, Niklaus P.. Clinical Periodontology and Implant Dentistry. Oxford: Blackwell Munksgaard. p. 815. ISBN 1-4051-0236-5. 
13. ^ Albrektsson, Tomas; Berglundh, Tord; Lindhe, Jan (2003). "Osseointegration: Historic Background and Current Concepts". In Lindhe, Jan; Karring, Thorkild; Lang, Niklaus P.. Clinical Periodontology and Implant Dentistry. Oxford: Blackwell Munksgaard. p. 816. ISBN 1-4051-0236-5. 
14. ^ Isidor F (June 1996). "Loss of osseointegration caused by occlusal load of oral implants. A clinical and radiographic study in monkeys". Clinical Oral Implants Research 7 (2): 143–52. doi:10.1034/j.1600-0501.1996.070208.x. PMID 9002833. 
15. ^ Brunski, JB (1999). "In vivo bone response to biomechanical loading at the bone/dental implant interface.". Adv Dent Res 13: 99–119. 
16. ^ Szmukler-Moncler, S; Salama H, Reingewritz Y, Dubruille JH (1998). "Timing of loading and effect of micromotion on bone-dental implant interface: Review of experimental literature.". Journal Biomed Mater Res 43: 192–203. 
17. ^ Pauletto N, Lahiffe BJ, Walton JN (1999). "Complications associated with excess cement around crowns on osseointegrated implants: a clinical report". The International Journal of Oral & Maxillofacial Implants 14 (6): 865–8. PMID 10612925. 
18. ^ Bernard, Carranza, and Jovanovic (1996), pp. 688-689.^{[verification needed]}
19. ^ Biomet Orthopedics, Regenerex® Porous Titanium Construct, http://www.biomet.com/orthopedics/productDetail.cfm?category=2&product=231
20. ^ Zimmer Orthopedics, Trabeluar Metal Technology, http://www.zimmer.com/ctl?template=CP&op=global&action=1&id=33
21. ^ Zimmer Cancellous-Structured Titanium Porous Coating, http://www.zimmer.com/ctl?op=global&action=1&id=7876&template=MP
22. ^ Osseointegration with Titanium Foam in Rabbit Femur, YouTube: http://www.youtube.com/watch?v=hdscnna5r1Q

Further reading

• Zarb GA, Schmitt A (July 1990). "The longitudinal clinical effectiveness of osseointegrated dental implants: the Toronto Study. Part II: The prosthetic results". The Journal of Prosthetic Dentistry 64 (1): 53–61. doi:10.1016/0022-3913(90)90153-4. PMID 2200880. 
• Apse P, Zarb GA, Schmitt A, Lewis DW (1991). "The longitudinal effectiveness of osseointegrated dental implants. The Toronto Study: peri-implant mucosal response". The International Journal of Periodontics & Restorative Dentistry 11 (2): 94–111. PMID 1718917. 
• Chaytor DV, Zarb GA, Schmitt A, Lewis DW (1991). "The longitudinal effectiveness of osseointegrated dental implants. The Toronto Study: bone level changes". The International Journal of Periodontics & Restorative Dentistry 11 (2): 112–25. PMID 1938184. 
• Barber AJ, Butterworth CJ, Rogers SN (January 2010). "Systematic review of primary osseointegrated dental implants in head and neck oncology". The British Journal of Oral & Maxillofacial Surgery 49 (1): 29–36. doi:10.1016/j.bjoms.2009.12.007. PMID 20079957. 
• Hultin M, Gustafsson A, Klinge B (February 2000). "Long-term evaluation of osseointegrated dental implants in the treatment of partly edentulous patients". Journal of Clinical Periodontology 27 (2): 128–33. doi:10.1034/j.1600-051x.2000.027002128.x. PMID 10703659. 
• Olivé, Jordi; Aparicio, Carlos (1990). "The periotest implant as a measure of osseointegrated oral implant stability". The International Journal of Oral & Maxillofacial Implants 5 (4): 390–400. 
• Holmgren EP, Seckinger RJ, Kilgren LM, Mante F (1998). "Evaluating parameters of osseointegrated dental implants using finite element analysis--a two-dimensional comparative study examining the effects of implant diameter, implant shape, and load direction". The Journal of Oral Implantology 24 (2): 80–8. doi:10.1563/1548-1336(1998)024<0080:EPOODI>2.3.CO;2. PMID 9835834. 

External links

• Academy of Osseointegration
• Bioimplants Lab - Osseointegration
• Bicon Dental Implants
• Clinical research on osseointegrated dental implants
• Failure mechanisms of osseointegrated oral implants
• A system for the universal identification of osseointegrated dental implants. A proposal