Implant Survival vs Success Criteria & Prognosis

An implant that is still in the mouth has cleared only the lowest possible bar. Survival asks one binary question — is the fixture present and not yet removed? — and answers nothing about whether the bone and soft tissue around it are healthy. Success is a far higher and more clinically meaningful endpoint: it requires that the implant and the surrounding tissues be free of pain, mobility, progressive bone loss, and peri-implant pathology. The two are reported separately for a simple reason — survival rates flatter a cohort by counting diseased-but-retained implants among the wins, so a paper that reports only survival can mask a substantial burden of ailing and failing fixtures.¹²

This section sets out the vocabulary and the numbers that let you place any given implant on a defensible scale of health. It moves from the classic Albrektsson (1986) success criteria — still cited as the field's reference standard — through the marginal-bone-loss thresholds that anchor those criteria, to the ICOI Pisa (2007) Quality of Health Scale, which usefully subdivides the gray zone between frank success and outright failure into satisfactory survival and compromised survival. Throughout, one discipline governs the whole exercise: a finding is interpretable only against a known baseline radiograph. Bone loss measured from nothing is not bone loss; it is a guess.³

The criteria proposed by Albrektsson, Zarb, Worthington and Eriksson in 1986 remain the canonical definition of an individually successful implant, and four of their requirements still structure every modern scheme. The implant must be immobile when tested clinically; radiographs must show no peri-implant radiolucency; there must be no persistent pain, discomfort, or infection attributable to the implant; and marginal bone loss must stay below 1.5 mm during the first year of loading and below 0.2 mm per year thereafter.¹ A cohort in which 85% of implants meet these criteria at five years and 80% at ten was, in 1986, the proposed minimum standard for an acceptable implant system.

The bone-loss figures deserve a moment of context, because they are frequently quoted without their history. As originally described in 1986 the allowance was 1.5 mm in the first year after abutment connection, then 0.2 mm annually — a number derived from the machined-surface, externally connected fixtures of the era, which physiologically remodeled to the first thread. Contemporary bone-level and platform-switched designs are expected to remodel far less; little to no crestal change is the modern norm, and several authors now regard substantial first-year loss as a warning sign rather than an expected event.³ The clinically decisive distinction is therefore not the absolute millimetre but the trajectory: slow, self-limiting remodeling that plateaus is physiologic, whereas progressive loss accompanied by bleeding on probing or suppuration is peri-implantitis, not remodeling, regardless of how few millimetres have been lost.²

The binary of success-or-failure collapses too much useful information. The International Congress of Oral Implantologists, at its 2007 Pisa consensus conference (published by Misch and colleagues in 2008), adopted a modified James–Misch Quality of Health Scale that resolves implant status into four clinically actionable groups.² Two of these — Groups II and III — sit inside the survival category but describe very different prognoses, which is precisely the discrimination that a raw survival figure throws away.

Group I — Success (optimum health): no pain or tenderness on function, zero mobility, <2 mm of radiographic bone loss from placement, and no history of exudate. Group II — Satisfactory survival: no pain on function, zero mobility, 2–4 mm of bone loss, and no exudate — reduced but stable support. Group III — Compromised survival: possible sensitivity on function, no mobility, but >4 mm of bone loss (still <50% of implant length), probing depths typically >7 mm, and bleeding or recurrent exudate — in short, active peri-implantitis in a fixture that is still integrated. Group IV — Failure (clinical or absolute): any mobility, pain on function, bone loss exceeding 50% of implant length, or uncontrolled exudate; removal is indicated.²

The grouped scale is built from a handful of independent parameters, each with its own healthy and failing boundary. A successful implant satisfies every parameter on the left; a failing implant trips one or more on the right. The thresholds below combine the Albrektsson criteria with the ICOI Pisa cut-points, with the strength of evidence noted alongside each.

Combine pain and mobility, bone loss against baseline, probing depth, and BOP or exudate, then classify the implant on the ICOI Pisa scale. The thresholds follow Misch and colleagues (2008). Select the finding set that best matches the implant in front of you to reveal its classification and the management it implies.

Long-term data show that well-placed, well-maintained implants meet success criteria at high rates: Buser and colleagues, following 511 sandblasted, acid-etched implants, reported a 10-year survival of 98.8% and a success rate of 97.0%, with peri-implantitis affecting only 1.8% of fixtures — a useful reminder that survival and success can run close together when biology and maintenance are respected.³ The gap between the two figures widens precisely in the cohorts that accumulate Group II and Group III implants over time.

Classification is not an end in itself; it sets the management pathway and the prognostic conversation. Group I implants continue on routine supportive peri-implant care. Group II implants survive but are not optimal — document the reduced support, tighten the recall interval, reinforce home care, and hunt for the modifiable cause (occlusal overload, plaque control, prosthetic contour). Group III implants carry a guarded prognosis and require active peri-implantitis treatment, escalating from non-surgical to surgical therapy, with intensive monitoring of the response. Group IV implants are removed; the operative task then shifts to managing the resulting defect, identifying and correcting the cause, and renegotiating the treatment plan and its prognosis with the patient. The detailed disease-management algorithm is developed in its own section (see Peri-Implant Disease Management →), and the maintenance schedules that keep implants in Group I are covered under Supportive Peri-Implant Care →.