Patient-friendly definition from the DentistsDirectory.org dental glossary.
A dental implant is a small titanium post — roughly the size and shape of a tooth root — that is surgically placed into the jawbone to serve as an artificial foundation for a dental restoration. Titanium is used because of its exceptional biocompatibility: the body does not reject it, and over several months the surrounding bone grows directly onto its textured surface in a process called osseointegration, anchoring the implant as firmly as a natural root.
The term "dental implant" is often used colloquially to refer to the entire tooth replacement — but technically the implant is just the root portion. The complete system has three components: the implant (the titanium post placed in the bone); the abutment (a connector piece that attaches to the implant and protrudes above the gum line); and the crown, bridge, or denture that attaches to the abutment and provides the visible, functional tooth surface. Each component is custom-designed for the individual patient.
Unlike bridges, implants do not require grinding down adjacent healthy teeth. Unlike dentures, they are fixed in place and function like natural teeth. Most importantly, they are the only tooth replacement option that preserves jawbone — the mechanical stimulus from biting through an implant into bone prevents the bone resorption that inevitably follows tooth loss and that causes the sunken facial appearance associated with long-term tooth loss. With proper care, implants can last decades and are the most cost-effective tooth replacement over a lifetime despite higher upfront cost.