How do grades of titanium, as well as their processing and surfaces, impact strength, osseointegration, restorative ease, and success rates?
Dr Mike Norton wrote ‘Dentists rely on the word of manufacturers’ that implants are manufactured to a high standard- ‘often this is not the case’
Titanium
Discovered in Cornwall, Great Britain, by William Gregor in 1791 and named by Martin Heinrich Klaproth after the Titans of Greek mythology titanium is a chemical element with the symbol Ti and atomic number 22. It has a silver colour, low density, and high strength and is resistant to corrosion in seawater and chlorine.
Titanium Grading
A simple grading system describes the purity levels of titanium and can be summarised as:
- Grade 1: carries the highest impurity level.
- Grade 2: is the choice for watch manufacturing.
- Grade 3: is used in industrial and commercial applications.
- Grade 4: is used in marine sectors and by many implant manufacturers.
- Grade 5 alloy: Titanium with 6% aluminium, 4% vanadium, 0.25% iron and 0.2% oxygen.
- Grade 23 alloy: is a high purity version of Grade 5 titanium alloy.
The importance of Ti alloy for greater loading.
Masa & Braunitzer reported that ‘titanium alloy is 60% stronger than Grade 4 Titanium, making it suitable for orthopaedic and dental implant applications’
Grade 23 (Ti 6AL-4V ELI)
Grade 23 titanium alloy provides an excellent combination of high strength, light weight and good corrosion resistance.
Dental Implant Fractures are increasingly noted.
Users of a grade 3 or grade4 titanium system should take note of the higher risk of fracture compared to systems products from Grade 5 or Grade 23. This is especially seen in the abutment screw, which typically receives a significant degree of abutment loading, especially in angled cases. Implant Store supplies implant screw removal kits to UK practices and notes that the users requesting these kits are typically those using grade 3 or grade 4 titanium. See the article on implant screw removal. These issues were typically, but not only, limited to molar cases.
- Aesthetic advantage. Using a system produced in Grade 23 alloy means a narrower implant can be placed with the same loading potential as a wider one.
- Molar advantage. Sometimes even a 5mm wide implant has a narrow neck, increasing the probability of fractures. Producing such a system in grade 4 increases this two-fold. Employing an angled restoration on such a system creates a threefold risk of fracture with loading concentrated onto the weakest area around the collar or screw.
The Importance of a rough surface.
Dental Implant manufacturers enhance osseointegration by employing various processes to enhance the surface with the objective of improving bone response and increasing bone-to-implant contact (BIC) area.
Surface roughness is typically created by bombarding the surface with aluminium oxide, titanium oxide, calcium phosphate and biphasic calcium phosphates. This process creates what is known as an SLA surface (Sandblasted, Large grit, Acid-etch) and creates a rough titanium oxide layer that enhances osseointegration (fusion with bone).
After SLA surface treatment, it is important to remove the impurities from the implant surface. Manufacturers employ an array of differing technologies to achieve this. Some, like Paltop, use ultra-pure water washing.
Powerbone employs a newer process which plasma treats the surface, presenting the implant in a hydrophilic state immersed in fluid.
The importance of a clean implant.
Machining and SLA process impurities are reported as significant factors in poor healing and implant failure.
Dr Dirk U. Duddeck, Head of Research at the CleanImplant Foundation reports “many implants of inferior quality are contaminated with residues from the production and packaging process’. He acknowledged that ‘some companies set themselves apart and meet the quality demands of users and patients‘.
Dr Duddeck observed that ‘obtaining a macro- and micro-textured surface…by etching alone without sandblasting is highly desirable from a biological point of view’.
Bioner, an independently owned Spanish manufacturer, has achieved this by eliminating surface impurities with its patented Bioetch* process. When applied to Grade 23 Titanium alloy, the process creates macro and micro-textured surfaces without SLA blasting. The process is shown to stimulate osseointegration and shorten loading time.
Examined under the electron microscope, a rough honeycomb surface is observed, more regular in pattern than on other implant surfaces.
Even without SLA processing, the average roughness of the Bioner TopDM Dental Implant is 1.3 microns – well within the scale recognised by international literature. Bioner says its TopDM implant range is ‘the only system commercially available which offers this combination of macro and micro-texture without sandblasting. Independent authors described it as a ‘unique breakthrough‘
Bioner Top DM is available from Implant Store.
Powerbone Dental Implant is available from Implant Store
ask@implant-store.co.uk
*Trade Mark, Bioner SA.