Implant-supported prosthetics: what multi-unit abutments are for and what a passive fit means

Key points

• A multi-unit abutment is an intermediate part between the implant and the denture that moves the connection from the bone up to gum level and evens out the tilt of the implants.
• For a denture on several implants (All-on-4/5/6, implant-supported bridges), multi-unit abutments let the denture be screw-retained, removed for servicing, and kept from pressing on the implants.
• A passive fit means the denture framework seats on every support without tension or gaps. This is the main condition for keeping the screws from loosening, the framework from cracking, and the bone around the implants from being overloaded.
• A passive fit depends on the accuracy of the impression or scan, how the framework is made (a milled titanium bar versus casting), verification before final fixation, and the order the screws are tightened in.
• At Tursunov Clinic the multi-unit abutments are placed on the day of surgery, impressions are taken the same day, and in the clinic's cases a temporary restoration follows in 3 days, with a permanent denture on a titanium bar a week after the prosthetic stage begins.

What a tooth on an implant is made of, and where the multi-unit abutment fits in

An implant is a titanium 'root' in the bone. A connector attaches on top of it, and a crown or denture sits on that connector. When a single tooth is restored, that connector is called an abutment: it is custom-made, follows the shape of the tooth under the gum, and the crown sits on it like it would on a prepared natural tooth.

When a whole jaw or a large bridge rests on implants, the logic changes. Implants are never placed perfectly parallel to each other: bone quality differs from spot to spot, and the surgeon angles the implants toward wherever the bone actually is rather than wherever would be convenient for the prosthodontist. With All-on-4, the back implants are deliberately placed at an angle of up to 30–45° to avoid the sinus and the lower jaw nerve. Fitting regular abutments onto implants like that means a single denture simply will not seat on them.

A multi-unit abutment solves two problems at once. First, it comes in straight and angled versions (usually 17° and 30°) and 'redirects' a tilted implant so that all the denture's screw channels come out parallel. The clinic uses straight and angled multi-units about equally often — the choice depends on each implant's position, not on preference. Second, it raises the connection from bone level to gum level: the denture attaches not to the implant directly but to the multi-unit, so removing, cleaning or repairing the denture never touches the implant itself or the bone around it.

Why a full denture uses multi-unit abutments, not regular abutments

The clinic's surgeons take a clear position: for a denture on several implants, use multi-unit abutments. The reasons:

Screw retention instead of cement. A denture on multi-units is screwed in and out. It can be removed a year later for professional cleaning, to replace a broken tooth, or to be relined. A cemented denture cannot be removed without damage, and leftover cement under the gum is one of the causes of inflammation around implants.

Compensating for tilt. Angled multi-units let the screw channels exit through the palatal or chewing surface instead of through the front of the tooth.

A single level for every support. Every multi-unit in the same mouth sits on the same platform. The prosthodontist works with one type of connection instead of four abutments of different heights.

Protecting the implant. The implant-to-multi-unit connection is tightened once and never touched again. Everything that gets removed and reattached happens higher up, at the denture screws.

A temporary denture within days. The multi-units are placed during surgery itself, and impressions or a scan are taken from them right away. In the clinic's cases, a temporary restoration was ready three days after surgery, and a permanent denture on a titanium bar followed a week after the prosthetic stage began.

In the clinic's price list, the multi-unit abutment is a separate line by system: Izen — 25,000 ₸, MegaGen — 45,000 ₸, Neodent — 50,000 ₸, Straumann — 75,000 ₸ per unit. All-on-4 needs four, All-on-5 needs five.

What a passive fit is and why it matters most

Picture a metal denture framework with five holes for five screws. If the holes line up exactly with the five multi-units, the framework settles onto them on its own, with no force, and the screws turn freely. That is a passive fit. If even one hole is off by a fraction of a millimetre, the framework rests on four supports and the fifth has to be 'pulled in' by the screw. The denture looks fine and the patient feels nothing — but the structure is under constant strain.

What follows is known from clinical observation: screws holding that tension loosen or break; the framework cracks at its thinnest point; the bone around the implant that was 'pulled in' takes a constant load and can start to resorb. None of this shows up right away — it appears months later, and the patient arrives saying 'a screw just came loose,' when the real cause is the fit.

That is why a passive fit is not a detail — it is the condition for a long-lasting implant-supported denture. It is exactly what the clinic's doctors advise patients to ask about when choosing where to be treated.

What affects a passive fit

1. How accurately the implant positions are captured. A classic impression material with 4–6 implants introduces error: the material deforms, the transfer copings shift. That is why restorations on several implants use either splinted impressions (the copings rigidly linked together) or a digital scan. The clinic has a Primescan intraoral scanner for this; for longer restorations, the scan is supplemented with an accuracy check, the specifics of which the prosthodontist decides.

2. How the framework is made. A cast metal framework shrinks as it cools, making a passive fit hard to achieve. A titanium bar milled from a solid block, built from a digital model with no casting involved, is more accurate. In the clinic's cases, permanent All-on-5 dentures are made exactly this way, on a milled titanium bar.

3. Verification before the final fit. Before fixation the framework is tried in and checked: one screw is tightened at one edge and the opposite side is checked for a gap (the so-called single-screw test); an X-ray is taken if needed to reveal a gap between the framework and the multi-unit that is invisible to the eye. If the fit is not passive, the framework is sectioned, bonded back together in the mouth in the correct position, and remade — cheaper than replacing the denture a year later.

4. The order and torque of tightening. The screws are tightened with a torque wrench to the force the manufacturer specifies, in a set sequence — otherwise the framework skews right at the fixation stage.

The multi-units themselves. They are placed so the platforms sit at the same level relative to the gum, and angled ones are rotated the correct way. A crooked multi-unit placement cannot be fixed by the denture.

How this goes at Tursunov Clinic

Based on the clinic's cases, the stage looks like this. On the day of surgery, the surgeon places the implants and immediately fits the multi-units. Impressions or a scan are taken from them the same day. Three days later the patient receives a temporary screw-retained restoration — as in the cases 'Total All-on-4 rehabilitation' and 'Breakdown of teeth under crowns.' The permanent denture is made after integration; in the case 'All-on-5: a permanent denture on a titanium bar,' it was fitted a week after the prosthetic stage began. Arnur Tursunov and Almas Khamiyev lead the surgical part, Ruslan Grigoriev the prosthetic part.

What to ask at the consultation

Will the denture be retained on multi-unit abutments or with cement?

Will the framework be milled or cast?

How do you verify the fit of the framework before fixation?

Can the denture be removed for cleaning, and how often is that needed?

What does the estimate include: implants, multi-units, temporary denture, permanent denture — itemised separately?

Related services and guides

• Implant-supported prosthetics in Astana
• All-on-4 in Astana
• All-on-5 in Astana
• Full-arch implant restoration in Astana
• Dental implants in Astana

Frequently asked questions

Does a multi-unit abutment always cost more?

A multi-unit costs 25,000 to 75,000 ₸ per unit depending on the system. But it lets the denture be serviced without touching the implant; repairing a cemented restoration usually costs more.

Can a permanent denture be fitted onto multi-units right away?

A temporary one goes on first — it is light and lets the implants integrate without being overloaded. The permanent one is made after integration. The doctor gives the timeline.

What should I do if a screw comes loose?

Come to the clinic. Do not tighten it yourself: the cause may be in the fit, and tightening it further only makes that worse.

How much does a permanent denture cost?

Per the price list: 1,500,000 ₸ for All-on-4 (800,000 ₸ acrylic), 1,600,000 ₸ for All-on-5 (900,000 ₸ acrylic). Implants and multi-units are costed separately.