Grade 4, grade 5 and titanium-zirconium: what the numbers on implant titanium mean

Why titanium in the first place

Titanium became the standard implant metal after Brånemark's group showed that it could form a firm, direct and lasting connection with living bone (Adell et al., 1981). It is light, highly resistant to corrosion and fatigue, and forms a thin, stable oxide layer on its surface the moment it meets air. That oxide layer is what bone cells actually meet. A 2015 review of implant materials described titanium as still the gold standard for oral implants (Osman and Swain, in the sources).

When people talk about "titanium implants", though, they can mean several different materials. Engineering standards for surgical implants recognise four grades of commercially pure titanium and two closely related alloys, and newer alloys such as titanium-zirconium have been added since. Here is what distinguishes them.

Commercially pure titanium: grades 1 to 4

"Commercially pure" (cp) titanium is unalloyed, but it is never 100% titanium. It contains small amounts of oxygen, iron, carbon and nitrogen, called interstitial elements because they sit in the gaps of the metal's crystal structure. More oxygen and iron make the metal stronger and slightly less ductile. Grade 1 has the least, grade 4 the most.

The table below uses the values published in the Osman and Swain review, which in turn cites the American Society for Testing and Materials standards. Exact figures vary with manufacturing, so treat them as typical rather than exact.

Two things stand out. Strength more than doubles from grade 1 to grade 4, and nearly doubles again in the alloy. Stiffness, on the other hand, barely changes. All titanium materials are stiffer than bone; the review notes that the alloys' stiffness is closer to bone than most other implant materials apart from pure titanium itself, which helps spread load to the surrounding bone.

Grade 4 is the strongest pure grade, which is why it is common for implant bodies. The product documentation for a given implant line will say exactly which material and treatment is used.

Titanium alloy: Ti-6Al-4V ("grade 5")

Ti-6Al-4V is titanium with about 6% aluminium and 4% vanadium. It is the workhorse alloy of aerospace and orthopaedics, and it is often called grade 5. A version with lower oxygen, known as ELI (extra low interstitial), is used for medical implants because it is tougher.

The alloy's main advantage is strength. Where a component is thin or highly stressed, such as abutment screws, multi-unit abutments, narrow implants or the milled bar inside a full-arch bridge, that strength gives a larger safety margin. Its trade-off is a small amount of aluminium and vanadium. The Osman review notes that the clinical relevance of titanium sensitivity is not yet clear, and that alloys free of vanadium and aluminium, using elements such as niobium and zirconium, have been developed.

Titanium-zirconium: stronger narrow implants

Narrow implants (around 3.3 mm in diameter or less) are useful when bone is thin, but a narrow pure-titanium implant has less metal to resist bending, and fracture risk rises. One answer was an alloy of titanium with roughly 13–17% zirconium, introduced commercially by Straumann under the name Roxolid. The Osman review reports the manufacturer's tensile strength figure of 953 MPa, higher than both pure titanium and Ti-6Al-4V, though that figure comes from the manufacturer's own testing.

A 2016 systematic review pooled nine clinical studies of narrow titanium-zirconium implants: 607 patients and 922 implants. Mean survival was 98.4% at one year and 97.7% at two years, with average bone loss of 0.36 mm at one year and 0.41 mm at two (Altuna et al., 2016). The authors noted that these results matched regular-diameter titanium implants in the short term and that long-term data were still needed.

Straumann is one of the brands Precious Dental uses, alongside MegaGen and Neodent. We mention it here only to explain the alloy; we are not affiliated with any implant maker, and brand names belong to their owners.

Does the grade affect how bone grows onto the implant?

Bone responds to the surface more than to the bulk metal underneath. All of these titanium materials form a similar oxide surface layer, and modern implants have a deliberately roughened surface. Experimental research has shown that surface roughness at the micrometre scale has a much clearer effect on bone response than small differences in composition (Wennerberg, 2009). We cover that in our article on implant surface treatments.

Where the grade does matter is mechanics: how thin an implant can safely be, how a narrow implant copes with chewing forces over decades, and how components and screws behave. In the Swedish population data, implants shorter than 10 mm were linked to higher odds of early loss (Derks et al., 2015), a reminder that geometry and bone matter at least as much as the alloy.

Fatigue: the slow way metal fails

Teeth are loaded many times a day for decades. Even a load well below a material's tensile strength can, over millions of cycles, start a microscopic crack that slowly grows. This is fatigue, and the Osman review notes that the proposed mechanism of titanium implant fracture in the literature is metal fatigue from high cyclic chewing loads (Osman and Swain, 2015).

Implant fractures are uncommon, but they are more likely when an implant is narrow, when it carries a long overhang of bridge (a cantilever), when the person grinds their teeth heavily (bruxism) or when bone has been lost around the top so that the implant flexes more. That is why stronger materials matter most in exactly the places where geometry is least favourable, and why planning the number and position of implants on a 3D scan is as important as the alloy. Manufacturers test implant designs for fatigue under standard laboratory conditions before sale, which is where figures such as fatigue strength in newtons come from.

Questions worth asking

• Which implant brand and product line will be used, and what is it made of?
• Will I get the batch numbers in writing, in an implant passport or similar?
• If a narrow implant is planned, why, and is it pure titanium or an alloy?
• What is the bridge framework made of?
• Do I have any known metal allergies that should be considered?

None of these questions is awkward for a clinic that plans properly. At our clinic the number of implants and the brand are set out in your written plan after the 3D scan, and the implant passport records what was placed.

Titanium, zirconia, or both?

Zirconia (a ceramic) is increasingly used for the teeth of full-arch bridges and, less often, for the implants themselves. For the implant body in full-arch treatment, titanium still has far more long-term evidence. For the visible teeth, zirconia offers strength and appearance. See our zirconia page and the main titanium page for the bigger picture, and the glossary for short definitions.

Common questions

Is pure titanium better than titanium alloy for implants?

Neither is simply better. Commercially pure titanium has a long clinical record and excellent bone response. Alloys are stronger, which helps for narrow implants and small components. Both are used successfully.

What does grade 5 titanium mean?

In everyday use, grade 5 refers to the alloy Ti-6Al-4V: titanium with about 6% aluminium and 4% vanadium. An extra-low-interstitial version (ELI) with less oxygen is used for medical devices.

Can I find out what my implants are made of?

Yes. Ask for the implant brand, product line and batch (lot) number. The manufacturer's documentation states the material. At Precious Dental, every implant patient receives an implant passport recording the implants used.

Does the titanium grade affect allergy risk?

True titanium allergy appears to be rare and its clinical relevance is debated. Alloys contain small amounts of other metals such as aluminium and vanadium. If you have known metal allergies, tell your dentist before planning, and ask about zirconia options.

Is the titanium bar in a full-arch bridge the same material as the implants?

Not necessarily. Frameworks and screws are often milled from titanium alloy blocks for strength, while the implant body may be pure titanium. See our frameworks and bars page.

Sources

1. Osman RB, Swain MV. A critical review of dental implant materials with an emphasis on titanium versus zirconia. Materials (Basel) 2015. PMID 28787980 (free full text, Table 2 for mechanical properties)
2. Altuna P, Lucas-Taulé E, Gargallo-Albiol J, Figueras-Álvarez O, Hernández-Alfaro F, Nart J. Clinical evidence on titanium-zirconium dental implants: a systematic review and meta-analysis. Int J Oral Maxillofac Surg 2016. PMID 26852292
3. Derks J, Håkansson J, Wennström JL, Tomasi C, Larsson M, Berglundh T. Effectiveness of implant therapy analyzed in a Swedish population: early and late implant loss. J Dent Res 2015. PMID 25503901
4. Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981. PMID 6809663
5. Wennerberg A, Albrektsson T. Effects of titanium surface topography on bone integration: a systematic review. Clin Oral Implants Res 2009. PMID 19663964

Checked October 2026. Where we give our own view as a clinic, we say so.