Implant screw loosening: causes and what to do

Why do implant screws come loose?

An implant screw comes loose when its preload, the tension created at tightening that clamps the restoration to the implant, drops below the forces trying to pull that joint apart during chewing. Low torque, a restoration that never fully seated and lateral loading all eat into that margin.

It is one of the most common technical complications. In Jung and colleagues’ systematic review (Clinical Oral Implants Research, 2012) of 46 studies on implant single crowns, the cumulative five-year incidence of screw loosening was 8.8%.

Huang and Wang (Journal of Esthetic and Restorative Dentistry, 2019) reviewed 99 papers on the mechanism. Internal connections and abutments with conical, anti-rotational designs resist loosening better; cantilevers raise the risk. Their clinical advice: torque to the recommended value, avoid tightening and loosening the same screw over and over, and shorten recall intervals so loose screws get caught early.

Is it the screw, the crown or the implant?

A loose screw, a debonded crown and a mobile implant all produce the same complaint, “my crown moves”, and each needs a different response. In Stilwell’s review (British Dental Journal, 2024), patients often notice a loose screw early, as a slight click when they bite or chew. Clinical signs are subtle at first: a gap or fluid at the margin and movement of the restoration in excursions.

A zirconia restoration bonded to a Ti-base can debond from the base while the screw stays tight. Pitta and colleagues (The International Journal of Prosthodontics, 2021) report that failure on a multi-unit prosthesis on Ti-bases after short service, and note that lab studies had already flagged the risk. The restoration spins or comes off; the base stays on the implant.

A radiograph sorts out the rest, as long as the beam is perpendicular to the connection. In an in vitro study by Sharkey and colleagues (The International Journal of Oral & Maxillofacial Implants, 2011), gaps of 12.7 µm were reliably seen with the beam up to 5° off perpendicular. At 15° off, only gaps of 51 µm or more were reliably detected.

What makes a screw loosen again?

A screw that loosens twice in the same place has a cause beyond torque. The table lists the causes described in the literature, the sign each one leaves and what to do.

On a full-arch bridge, a screw that keeps loosening on one abutment is a reason to test passive fit. In Katsoulis and colleagues’ review (European Journal of Oral Implantology, 2017), misfit slightly raised the risk of screw-related complications, with no confirmed effect on bone. The guide on full-arch bridges that won’t seat shows how to test.

Retighten or replace the screw?

Retighten a screw that has loosened once if its threads and head are intact; replace it when it shows wear or has already been tightened and loosened many times. In Xiao and colleagues’ systematic review (The International Journal of Oral & Maxillofacial Implants, 2017), the literature was thin. Still, the 44 loose screws reported in two studies stayed tight after a single retightening.

The authors don’t recommend routine screw replacement. The limit shows up in lab testing. In Shui and colleagues’ review (Journal of Dentistry, 2026) of 16 in vitro studies, removal torque dropped after five tightening and loosening cycles. After ten it dropped further, and the threads showed wear.

Count every opening over the restoration’s life, not just the loosenings: try-ins, adjustments and repairs are cycles too. For a screw that has been through several, consider a new one.

When does a loose screw point to the occlusion?

A loose screw points to the occlusion when it comes back after correct retightening and a radiograph with no gap. In Hsu and colleagues’ review (The International Journal of Oral & Maxillofacial Implants, 2012), occlusal overload was considered the main cause of biomechanical complications, screw loosening among them. It was linked to bruxism.

Bruxism shows in the numbers. In Vidal and colleagues’ meta-analysis (Journal of Prosthodontics, 2025) of 13 studies, bruxism raised the odds of screw loosening 3.4-fold and of screw fracture 7.1-fold.

Before you retighten a third time, review the occlusal scheme. The guide on implant crown occlusal adjustment sets out the contact targets. For patients who brux, Stilwell’s review recommends a hard night-time appliance, such as a milled occlusal splint.

What should you tell the lab for a repair?

Talk to the lab before you ship and give the history: when the restoration went in, how many times the screw has loosened, the torque you used and what the radiograph showed. That way the case arrives with the right question.

Send the lab:

• The crown or bridge with its Ti-base and screw, each labeled.
• The radiograph taken perpendicular to the connection.
• Photos of the contacts marked in light closure, firm closure and excursions.
• Implant brand, system and platform, and the component model.
• If the restoration is being remade, a new scan with scan bodies, opposing arch and bite.

We work with Neodent and Titaniumfix components, both made in Brazil. If we made the restoration, give us the case in the portal (its screens are in Portuguese): the order holds the brand and platform you sent. If a full-arch acrylic bridge also has a broken or worn tooth, that goes in as a repair.

Ask how adjustments and remakes work before your first case. What you can prevent on the Rx, from scan bodies to the opposing arch, is in why implant crowns get remade. The restoration itself is on the zirconia implant crown page.