Biocompatibility: What Really Belongs in Your Mouth?

In recent years our patients have been arriving with the same question. Not "which crown looks most natural?" but "which material will my body accept for the next twenty years?" This article explains how we approach that question at İ-Klinik.

The word biocompatible is used generously in dental marketing. At İ-Klinik it has a precise definition, borrowed from European regulation: a material is biocompatible if it can perform its function in contact with living tissue without producing an unacceptable adverse reaction. The standard governing this, DIN EN ISO 10993, runs to thousands of pages. It is not just a slogan.

In plain language, what does that mean for you? Three things. First, the material must not release ions or particles in harmful concentrations. Second, it must not trigger an allergic or inflammatory response in the surrounding gum, bone or systemic tissue. Third, it must remain mechanically and chemically stable for decades in a mouth that is warm, acidic and constantly in motion.

Why we took amalgam off the shelf

Amalgam, the dark grey mercury-silver alloy that filled our parents' molars, was the workhorse of the twentieth century. It was cheap, quick to place and reasonably durable. It is also a material that European regulators have progressively banned, and one we removed from our materials catalogue years earlier.

The clinical evidence on amalgam is more nuanced than the headlines suggest, but the direction is clear. As of January 2025, the European Union has prohibited the use of dental amalgam under EU Regulation 2017/852, apart from limited exceptions of medical necessity. The reasons are both environmental and biological. We read that signal early and made the transition ahead of time.

"The most honest answer we can give a patient is that the materials we use today are the same ones we would choose for our own mouths. Anything less is unacceptable."

In place of amalgam we use modern composite resins that are free of bisphenol-A, light-cured and applied in layers thinner than two millimetres. Placed under the right conditions they are colour-matched, mercury-free and equal or superior to amalgam in durability. Those right conditions matter, because composite is technique-sensitive. A poorly placed composite is worse than a well-placed amalgam. This is why we never rush a restoration at İ-Klinik.

Titanium: an unlikely member of the periodic table

If you receive implant treatment at our clinics, the implant body placed in your jawbone is almost certainly commercially pure grade-4 titanium or a titanium-zirconium alloy. Both are manufactured to ASTM F67 and F136 standards and supplied by the two most established names in implantology: Straumann or Nobel Biocare.

Titanium has a remarkable property called osseointegration: living bone forms a direct structural and functional bond with the titanium surface, without any intervening soft tissue. The phenomenon was first observed in the 1960s by the Swedish surgeon Per-Ingvar Brånemark, and it underpins every modern implant system. Properly placed titanium implants show 10-year survival rates above 95% in published long-term studies.

Allergic reaction to titanium is extremely rare (a few cases per million) but not zero. For the small number of patients with documented sensitivity, we offer ceramic (zirconium dioxide) implants as an alternative.

Zirconia: the ceramic that behaves like metal

The most significant development in restorative dentistry over the past decade is the maturing of yttria-stabilised zirconium dioxide as a structural material. Zirconia is technically a ceramic, but its mechanical properties rival metal alloys, with flexural strength above 1,200 MPa in high-strength formulations. It is white. It is chemically inert. It does not corrode. It is visible on X-rays. And it can be milled from a monolithic block in under an hour in our in-house CAD/CAM laboratory.

For crowns, bridges and increasingly implant abutments, zirconia is İ-Klinik's default material. It eliminates the dark grey gumline that appears over time with metal-ceramic crowns. It transmits light more like natural enamel. And for our most biocompatibility-conscious patients, it removes metal from the visible restoration entirely.

What we use where

• Implant body: Straumann SLActive titanium-zirconium (Roxolid®) or Nobel Biocare TiUnite titanium.
• Implant abutment: Zirconia (default) or titanium where chewing forces demand it.
• Crowns & bridges: Monolithic zirconia (Zirkonzahn Prettau®) or layered E-max lithium disilicate.
• Veneers: Hand-pressed E-max or feldspathic ceramic, depending on tooth structure.
• Fillings: Bulk-fill composite resin, BPA-free, layered under rubber dam isolation.
• Cementation: Self-adhesive resin cements with documented biocompatibility profiles.

Questions to ask whichever clinic you visit

Wherever you receive treatment, in London, İstanbul, Berlin or Milan, these are reasonable questions to put to your dentist before any restorative work:

• Who manufactures the implant or crown being placed, and may I see the product certificate?
• Is the material CE-certified for the indication you are recommending?
• What is the published survival rate of this material in cases like mine?
• Where is the laboratory work done, and by whom?
• What is your guarantee period, and what does it cover?

A clinic that welcomes these questions and answers them with documentation deserves your trust. Walk away from one that does not.

Sources: ISO 10993-1:2018 (Biological evaluation of medical devices); Regulation (EU) 2017/852 of the European Parliament and of the Council on mercury; Schwarz F. et al., "Long-term retrospective evaluation of survival rates of zirconia ceramic implants", Clinical Oral Implants Research, 2021.