One-piece vs two-piece dental implants: what the micro-gap really changes

An implant restoration has two functional parts: the screw in the bone and the abutment that carries the crown or bridge. In a two-piece system they are separate components held together by a small internal screw. In a one-piece system, also called monoblock or single-piece, they are machined from one block of titanium. The part that sits in the bone and the part that sticks through the gum are the same body.

That single fact explains almost every trade-off. A two-piece implant can be placed, left to heal under the gum, and fitted later with an abutment of any angle or height, a flexibility described on our types of dental implants page. A one-piece implant goes into the bone with its abutment already attached, so the surgeon must place it in the right position and angle on the first attempt.

The bridge is built around what the surgeon achieved.

Where two parts meet, a hairline space remains. In two-piece implants this micro-gap sits near the bone crest. Laboratory and animal work links it with micromotion and bacterial leakage, and the authors of a 2017 meta-analysis of eight clinical studies describe it as the main negative influence on crest bone (Wang et al. 2017).

That is the strongest argument for one-piece designs.

The clinical evidence is thinner than the argument. A systematic review of animal and human studies, all at high risk of bias, found that crest bone changes differed by about 0.5 mm (weighted mean difference 0.479 mm) depending on where the gap sat relative to the bone crest, favouring a position below it.

It concluded that the effect of the connection type itself lacks documentation (Schwarz et al. 2014). So the micro-gap is real, but how much it matters in patients is not settled.

The table sets out the comparisons that could be checked against open full texts.

Read the Pirc row with care. In the Zurich trial the one-piece arm was a Straumann implant, not a basal or bendable-neck design, and the two-piece arm was an earlier-generation Brånemark implant. The authors warn against applying the results to modern two-piece systems, and 21 of the 60 patients missed the final visit (Pirc et al. 2026).

The zirconia row is a different material and a lopsided comparison, with 199 two-piece implants against 3,818 one-piece, and most cases were followed for only a few years. Neither row shows that one design lasts longer in titanium today.

The two largest developer-linked series (Lazarov 2019 and Patel 2025) report no peri-implantitis. In Lazarov's series of 5,100 implants followed for up to 57 months, none was reported (Lazarov 2019).

Those are encouraging results, with the usual limits of observational work: the patients were followed rather than randomised, and part of the follow-up was a patient interview. Independent long-term comparisons are still limited.

The randomized Zurich trial gives a less favourable picture. After 15 to 17 years, peri-implantitis was diagnosed in 12 of 65 one-piece implants (7 of 30 patients) and 8 of 86 two-piece implants (5 of 30 patients), reported descriptively without a statistical test, and the implants lost in both arms were lost to peri-implant disease.

The abstract reports higher rates in the one-piece group, while the discussion calls the prevalence in the two groups comparable and warns that too few patients remained to detect differences (Pirc et al. 2026).

The finish of the neck seems to matter too. In the developer's report on a single patient followed for 20 years, polished shafts kept their bone level while roughened shafts developed crater-like loss (Ihde and Ihde 2018).

The practical limit of a one-piece implant is its angle. If two implants in a bridge are not parallel, the abutments will not line up. A two-piece system solves this with angled abutments. A one-piece system solves it by bending the neck during surgery, a step the surgeon plans from the scan.

Bending is built into some designs. One prospective cohort found no significant effect on survival: on radiographic follow-up 97.5% of bent implants survived against 96.1% of unbent ones (p = 0.413), and the difference was also not significant by clinical inspection or patient report (Lazarov 2019).

In a 2019 series by Pałka and Lazarov, which appears to describe the same 87 patients as the Lazarov cohort, 376 of 1,019 implants (36.9%) had bent necks (Pałka and Lazarov 2019). The two papers are one data set, not two confirmations. So bending is routine in these protocols, which is why accurate planning, a well-adjusted bite (occlusion) and regular check-ups matter.

Because the abutment is fixed, the position chosen at surgery also shapes the final bridge.

A one-piece design suits adults who want a rigid, fixed bridge within days, especially when bone is thin or sloping and a graft would add months. It also suits people who want to avoid an abutment screw that can loosen, and whose dentist has real experience with the system. For a suitable patient the benefit is a shorter route to fixed teeth with fewer parts to maintain.

One-piece implants are usually restored with a cemented bridge, locked together in a rigid splint soon after surgery. This removes the abutment screw, but it also makes the bridge hard to remove.

In the largest recent series, retrieving a cemented prosthesis was described as painful and time-consuming, and the authors suggested screw-retained designs instead (Patel et al. 2025).

A 2022 review of prosthetic failures adds that excess cement is difficult to remove even at shallow margins, and recommends screw retention to reduce that risk (Sailer et al. 2022).

Two-piece implants offer screw-retained bridges that a dentist can take off for cleaning or repair, which also helps when a single implant is lost. When a fixed bridge can be placed on two-piece implants depends on the protocol, either after a healing period or with immediate loading, which our immediate loading guide covers. Neither approach is simply better.

The right question is which one fits the plan for your jaw. Clinics try to manage the limits of both designs in the same way: planning from a CBCT scan, bite adjustment after surgery and control appointments, plus a clear agreement on how the bridge is fixed.

A one-piece implant is always a one-stage implant, because the abutment is part of it and passes through the gum from day one. A two-piece implant can follow either route.

In two-stage surgery the implant is placed below the bone crest and soft tissue and the flap is closed over a cover screw; in one-stage surgery a healing abutment is placed at the time of surgery (Gheisari 2017).

A randomized trial of 310 implants in 140 patients measured 0.76 mm and 0.842 mm of marginal bone loss six months after loading with the one-stage and two-stage approaches, and the authors found no significant difference (Gheisari 2017). It came from one centre, followed patients briefly, and the groups were unequal in size.

Flapless placement, with no gum flap lifted, is a separate question. A meta-analysis of 23 publications found failures 1.75 times as likely with flapless surgery (95% CI 1.07 to 2.86), but 16 studies were at high risk of bias and the result changed when high-risk and low-risk studies were pooled separately (Chrcanovic 2014).

Screw loosening is the most frequent technical problem of single implant crowns, with a cumulative five-year rate of 8.8%, while abutment screw fracture is rare. Rates fell after 2000, from 3.9% to 26.2% in earlier studies to 3.1% to 10.8% in later ones, but no design has removed the problem (Sailer 2022).

A one-piece implant has no abutment screw, which removes that failure point and moves the weak spot to the cemented bridge: Patel 2025 recorded fractures of ceramic and acrylic bridges and decementation of bridges.

Implant fracture is the other concern. In a review of zirconia implants, 26 of 4,017 (0.65%) fractured, most of them narrow-diameter, and fractures were more frequent when the one-piece abutment had been ground with a drill (18 of 746, 2.4%) than when it had not (8 of 3,245, 0.2%) (Mohseni 2023). The sources cited here give no fracture rate for one-piece titanium implants.

The Zurich trial's higher technical complication rate for one-piece implants (35.4% against 5.8%) does not show that modern designs break more often.

Most zirconia implants in clinical studies are one-piece. In a 2023 review of 25 studies (4,017 implants in 2,083 patients), 95.0% were one-piece and 5.0% two-piece, and ten-year cumulative survival was 95.1%. The authors caution that most cases were followed for only a few years and that zirconia has been studied less than titanium.

Two-piece zirconia implants failed more often (7.5% against 4.1%, p = 0.017), though that rests on 199 implants. The authors suggest manufacturers were at first wary that thin connection parts would tolerate load, which would explain why the one-piece type came first (Mohseni 2023).

Ask a clinic offering ceramic implants which model it uses and what follow-up data exist for that model. Our zirconia vs titanium guide covers the material question.

This table is a map for the conversation with your dentist. The "Why" column is general clinical reasoning, not a finding from the studies cited here, except where a source is linked. The final call depends on your scan, your bite and your dentist's experience with each system.

Nexwell coordinates treatment and does not perform it. The 72-hour route offered by Nexwell's partner team is built on the IHDE corticobasal concept, whose devices in the cited studies are mostly one-piece.

The 72-hour full mouth implants page explains who may be assessed for it, and the corticobasal guide shows how to vet any clinic offering it. For cases that suit a conventional two-piece plan, see All-on-4 and All-on-6.

If a fixed bridge within days sounds right for you, the 72-hour page is the natural next step. If you are weighing the whole range of implant options, the full mouth implants overview is the better starting point.

Ask which system is planned and why that design suits your case. Ask how the bridge is fixed and whether it can be removed. Ask what happens if one implant fails. Ask the clinic's own record: how many implants of that type it has placed, and how many it has followed for five years. A clear written answer is a good sign. A vague one is information too.

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Prepared by the Nexwell Team on 31 October 2026. Medically reviewed by Dt. Mehmet Salih Yıldırım, DDS, PhD.