“I have heard about the advantages at two consultations already. Tell me what nobody has told me.”
A remark of this kind is sometimes made towards the end of an appointment, once the patient has a treatment plan in front of them. Information about full-arch restoration on four implants deals mainly with what the method delivers: a fixed bridge instead of a removable denture, restoration within a short time, a predictable functional result. The compromises it calls for appear less often — although they are described in the literature and are no secret.
In short, there are five of them: the extractions are irreversible, the bridge is a single unit that can be serviced only at the surgery, the transition line may be visible in a patient with a high smile line, hygiene becomes a condition of success, and control of biting force is weaker than with natural teeth. The All-on-4 compromises are not arguments against the method — they are boundary conditions that have to be accepted before treatment begins. In conversations with patients attending Modern Dental & Orthodontics (Klinika MDO), the question that keeps returning concerns what nobody mentioned earlier. It usually relates to precisely this list.
Compromise #1: a one-way decision
Qualifying for a full-arch restoration almost always means extracting teeth that are still standing in the arch. Some of them have no prospects. Others, however, have a questionable rather than a hopeless prognosis: teeth weakened by periodontal disease that could still serve for years with appropriate treatment.
The difference matters. In a thirty-year observation of one hundred and fifty-four patients with periodontitis, treated and then seen for supportive appointments every three to six months, about five teeth in every hundred were lost during that phase; teeth judged unsuitable for treatment had been extracted earlier, during active therapy. The risk of loss was higher for molars, deep periodontal pockets and advanced bone loss.
This does not mean that every mobile tooth should be saved. It means that “this tooth will not last long anyway” is a prognosis rather than a fact — and the consequence of that prognosis is irreversible. The procedure usually also involves adjusting the height of the bone at the site of the planned restoration, that is, reducing it in a controlled way — equally impossible to undo.
If the treatment plan includes teeth about which the clinician says “we can try, but…”, it is worth asking for the alternative to be set out: how long they might realistically be kept, at what cost and with what risk of failure. A second opinion before the extractions costs incomparably less than an attempt to repair the decision afterwards. Of all the All-on-4 drawbacks, this one alone is irreversible: the others can be mitigated through the design of the restoration, through hygiene or with an occlusal splint, whereas this one cannot be undone once treatment has begun.
A separate matter is what happens between the extractions and the definitive restoration — several months with a temporary prosthesis, a soft diet and speech adaptation. We describe that stage in full in our article on the temporary prosthesis after All-on-X, and the course of the whole treatment in the guide to an implant bridge step by step.
Compromise #2: the restoration is a single unit
A full-arch bridge is not made up of separate crowns. It is one piece of prosthetic work screwed to the implants and spanning the entire arch — which is its greatest mechanical advantage and the source of a specific inconvenience.
This is visible even in the literature: a pooled review of studies on full-arch restorations analyses complications at the level of the whole restoration rather than the individual tooth. When a single tooth is damaged — a fragment of veneering material chipping off, for example — the entire restoration is serviced. Only the clinician removes the bridge, unscrewing it at the surgery. The patient has no access to it and cannot take it out, unlike a removable denture, which is taken out at home.
In practice every repair means an appointment, and sometimes several if the work has to go to the laboratory; a temporary solution is occasionally needed for that time. Servicing is therefore worth planning — a longer trip away is an argument for not postponing a review appointment.
For many people this is an acceptable compromise: the restoration is fixed and free of clasps, but there is no access to it. We describe the method itself under full-arch restorations on implants, and the scope of review appointments and servicing in our article on the durability of All-on-4.
Compromise #3: the transition line and a high smile line
The transition line is the boundary between the patient’s own gingiva and the pink part of the bridge, known as prosthetic gingiva. That pink part is not decorative — it restores the tissues lost together with the teeth and provides lip support.
The problem arises when a patient exposes gingiva on a broad smile. This is what we call a high smile line. The boundary between the patient’s own tissue and the prosthetic material may then be visible, and where the colours differ it can be noticed even at ordinary conversational distance. The extent of gingival display can be measured — the aesthetic literature describes a standardised way of recording lip dynamics and gingival display, precisely so that the restoration can be planned on a measurement rather than an impression.
There are three typical ways out and each is a compromise. Reducing the bone during surgery so that the transition line is hidden beneath the lip — effective, but irreversible: tissue once removed cannot be restored. Lengthening the tooth part of the bridge — this hides the boundary at the cost of proportion, because the teeth become longer than natural ones. A restoration without the pink part — possible only where tissue loss is slight.
There are three typical ways out and each is a compromise. Reducing the bone during surgery so that the transition line is hidden beneath the lip — effective, but irreversible: tissue once removed cannot be restored. Lengthening the tooth part of the bridge — this hides the boundary at the cost of proportion, because the teeth become longer than natural ones. A restoration without the pink part — possible only where tissue loss is slight.
Compromise #4: hygiene beneath the pontics stops being a recommendation
A space remains between the underside of the bridge and the gingiva. It is necessary — without it the area could not be cleaned — but it means that daily hygiene calls for tools most patients have not used before.
This limitation has direct clinical consequences. In papers on the prevention of peri-implant diseases in edentulous patients, access for cleaning is treated as a design criterion for the restoration rather than a matter of convenience. European implantology consensus statements list restricted access for hygiene among the factors that increase the risk of peri-implantitis — inflammation that leads to bone loss around the implant.
This changes the status of hygiene. With natural teeth, neglected brushing ends in caries and gingivitis, both of which can be treated. With an implant-supported restoration, hygiene becomes a condition for the success of the entire treatment. If somebody knows that they will not keep up a daily routine or attend review appointments, that is a substantive argument in the discussion about eligibility. Techniques and the choice of accessories are covered separately in our article on hygiene for implant-supported restorations.
Compromise #5: the absence of proprioception and what it means in bruxism
A natural tooth is suspended in its socket by the periodontal ligament (a thin layer of connective tissue joining the root to the bone). It contains receptors that report the force of pressure and allow it to be limited reflexively. An implant fuses directly with bone and has no such ligament.
The body compensates in part: osseoperception — sensation received through receptors in the periosteum, the mucosa, the masticatory muscles and the temporomandibular joint — restores some of that feedback. Some of it, not all. This means weaker control of biting force: a patient may load the bridge more heavily than they realise, and the warning discomfort appears later than it would with natural teeth.
This matters most in people with bruxism, that is, habitual clenching and grinding of the teeth. A 2025 systematic review with meta-analysis found that bruxism increases the risk of mechanical complications in implant-supported restorations — screw loosening or fracture, and chipping of the veneering material. The difference between patients with bruxism and the rest was pronounced enough that chance is an unlikely explanation.
Bruxism does not rule out treatment. It changes the plan: it calls for a discussion about the restorative material, about occlusal control and about a night-time occlusal splint, which with this method is not an optional extra but part of the treatment.
The All-on-4 compromises in a table: who is affected and how to manage them
| Compromise | Who is actually affected | What can be done |
| Irreversibility of the decision | Patients in whom some teeth have a questionable rather than a hopeless prognosis | Set out the alternative of keeping the teeth; a second opinion before the extractions |
| Single-unit construction | Everybody — it is a feature of the method | Plan for servicing; be aware that only the clinician removes the bridge |
| Visible transition line | Patients with a high smile line who expose gingiva | Measure the display before treatment; reduce the bone or change the design of the restoration |
| Demanding hygiene | Everybody, and critically: smokers, people with a history of periodontal disease and those who attend irregularly | Hygiene instruction before surgery; a restoration designed with access for cleaning |
| Absence of proprioception | Above all people with bruxism and a strong bite | Occlusal splint, occlusal control, choice of restorative material |
Contraindications to All-on-4 — a three-flag system
The All-on-4 compromises are one thing and contraindications to the procedure another, and in conversation both are often mixed up with risk factors. The division below separates these situations. A green flag does not mean consent to treatment — it says only that the factor in itself does not settle the matter against it.
Red flag — treatment ruled out or requiring postponement. Active malignant disease during head and neck radiotherapy. Antiresorptive treatment at oncological doses — intravenous bisphosphonates and denosumab at the oncological dose — because of the risk of osteonecrosis of the jaw. The same medicines at doses used in osteoporosis belong to the orange flag rather than the red one; we discuss the differences in our article on antiresorptive medication and implants. Recent myocardial infarction or stroke, where elective surgery is postponed. Uncontrolled diabetes with persistently high blood glucose. Skeletal immaturity, before growth of the facial skeleton is complete.
Orange flag — requires correction before treatment. Smoking. A systematic review with meta-analysis published in 2024 found that early implant failure — loss of the fixture before it has been loaded with prosthetic work — occurs markedly more often in smokers than in non-smokers. Reducing or stopping smoking around the time of surgery is part of the preparation, not a suggestion. In people who smoked in the past and no longer smoke, the risk is lower than in current smokers. Type 2 diabetes — with good glycaemic control the outcomes approach those seen in people without diabetes, whereas with persistent hyperglycaemia bleeding of the peri-implant tissues and greater marginal bone loss occur more often. Bruxism. Untreated periodontitis. Osteoporosis and oral antiresorptive medication, which in most situations do not rule out treatment but call for separate assessment — we write about this in our article on implants in osteoporosis. Anticoagulants and antiplatelet medication, which require the approach to be agreed with the treating physician and never stopped by the patient alone.
Green flag — factors that do not in themselves rule out treatment, although they call for individual assessment. Advanced age, if general health allows. Controlled hypertension. Many years of wearing a removable denture. None of these factors is in itself an indication for treatment.
Whatever the flag: before eligibility is assessed, the clinician must be given a full list of the medicines being taken, together with their doses — in particular bisphosphonates, denosumab, anticoagulants and antiplatelet agents, glucocorticoids and immunosuppressants. From the perspective of the clinical team at Modern Dental & Orthodontics (Klinika MDO), what matters is that the eligibility discussion devotes more time to the limitations of the method than to its advantages — because it is the limitations that determine how a patient will judge the treatment five years on.
Checklist: what to ask at the consultation
The questions below follow from the compromises described above and from the way care is organised after treatment.
- Which teeth have a questionable prognosis and which are hopeless? Ask for the reasoning separately for every tooth scheduled for extraction.
- What would the alternative of keeping the teeth look like? How long it might last, at what cost and with what risk of failure
- How much gingiva shows when I smile broadly? If nobody has measured it, the aesthetic assessment is incomplete.
- Does the design of the restoration allow access for cleaning? And who will teach me the hygiene routine.
- Have I been diagnosed with bruxism, and what follows from that for the plan? A question about an occlusal splint and occlusal control.
- How quickly does the clinic deal with an urgent removal of the restoration? And what happens if the damage occurs outside surgery hours.
- Which implant system and which abutments will be used? With that information another practice will be able to service the restoration should life circumstances change.
Frequently asked questions
What are the main drawbacks of All-on-4?
Five: the irreversibility of the decision to extract, a single-unit restoration that has to be serviced as a whole, possible visibility of the transition line with a high smile line, demanding hygiene requirements, and weaker control of biting force resulting from the absence of the periodontal ligament. Each of these limitations has established ways of being managed.
Can All-on-4 treatment be reversed?
Not in the sense of returning to the starting point. Extracted teeth and reduced bone height cannot be restored. What can be changed is the restoration itself — replacing the bridge with a new one or, if needed, moving to an overdenture on the same implants.
Who is not eligible for All-on-4?
Absolutely: patients undergoing head and neck radiotherapy, those taking antiresorptive medication at oncological doses, those with uncontrolled diabetes, and those whose facial skeleton has not finished growing. Situations requiring correction before treatment — untreated periodontitis, smoking or undiagnosed bruxism, for example — are assessed separately.
Does smoking rule out treatment?
It does not rule it out, but it markedly increases the risk of early implant failure, that is, loss of the fixture before it has been loaded. Reducing or stopping smoking around the time of surgery is regarded as part of the preparation for treatment. A smoker who does not change this should know the difference in risk before deciding.
Can All-on-4 be carried out in bruxism?
It can, provided that the bruxism is diagnosed before treatment and taken into account in the plan. Habitual clenching increases the risk of mechanical complications in the restoration. Management includes occlusal control, the choice of restorative material and a night-time occlusal splint — treated as part of the treatment rather than an option to consider.
Is the join between the bridge and the gingiva visible?
It depends on the smile line. With a low or average one the boundary stays hidden beneath the lip. With a high one, where a band of gingiva is exposed on smiling, it may be visible. The extent of display is assessed before treatment, because it determines the design of the restoration and the extent of surgery.
Does All-on-4 bite like natural teeth?
Functionally a fixed restoration performs incomparably better than a removable denture, but control of pressure remains weaker than with natural teeth. The reason is the absence of the periodontal ligament together with its receptors. Some of the feedback returns through osseoperception, though not to the full extent.
Do healthy teeth have to be extracted?
Healthy teeth are not extracted. The issue concerns teeth with a questionable prognosis that could still serve with periodontal treatment. If the plan includes extracting such teeth, it is worth asking for the reasoning for each of them separately, and for a quotation for the alternative of keeping them.
Is age a contraindication?
Age alone is not. What matters is general health, the medicines being taken and the ability to maintain hygiene and attend review appointments. Skeletal immaturity is a contraindication: treatment is not carried out before growth of the facial skeleton is complete, because an implant does not move with growing bone.
Summary
The compromises described above are not arguments against the method. They are arguments for making the decision in full awareness of the boundary conditions — and the only one of them that cannot be revisited later is the extractions.
A patient who knows about these matters before treatment judges the result differently from one who discovers them afterwards. That is usually the whole difference between satisfaction and disappointment.
Read more:
- Full-arch restorations on implants — All-on-X
- All-on-4 or All-on-6 — what determines the number of implants
- Hygiene for implant-supported restorations
- Temporary prosthesis after All-on-X — the healing phase
- How long does All-on-4 last — durability and servicing
Content and liability disclaimer
This article is informational and educational in nature and does not constitute medical advice, a diagnosis or a therapeutic recommendation — it does not replace a consultation with a specialist. If you are experiencing symptoms, have doubts or are facing a decision about treatment, consult a dentist. The methods described and the data cited are general in nature. The results of scientific studies relate to populations, not to an individual patient. The course and outcome of therapy depend on the individual clinical situation and may vary between patients. No information contained in this article constitutes a guarantee of result. The content has been prepared with due care, based on publicly available medical knowledge and the scientific publications indicated in the Sources section. We do not advise taking or refraining from any health-related action solely on the basis of the content of this article, without prior consultation with a doctor.
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