Tooth agenesis discovered in adulthood

Around one person in four worldwide is born without at least one wisdom tooth. They have not lost it: they never had it. A meta-analysis published in 2026 in Archives of Oral Biology, covering more than 87,000 people, estimates the global prevalence of third molar agenesis at 23.07 per cent (Angelakopoulos et al., 2026). It is one of the most common variations in human development, and those affected often discover it by chance on an X-ray taken for an entirely different reason, perhaps years or decades later.

The third molar is a borderline case, and its absence rarely changes anything in a person’s life. But the same mechanism, a tooth that never formed during intrauterine life, also affects teeth with a far more visible role. The upper lateral incisor. The second premolar. When one of these is missing, the story changes, and above all the way it is experienced changes. It is not an inconsequential absence. It is an absence that shows, or that should have been seen, had someone noticed it early.

A common absence, but rarely recognised

The most robust reference on the prevalence of agenesis of permanent teeth, excluding third molars, remains a 2004 meta-analysis of Caucasian populations in North America, Europe and Australia (Polder et al., 2004). The figures vary by continent and by sex: in Europe prevalence is 4.6 per cent in males and 6.3 in females, in Australia it rises to 5.5 and 7.6 per cent respectively, and in North America it falls to 3.2 and 4.6. In every population considered, women present with agenesis about 1.37 times more often than men.

The most useful figure for understanding why this condition is missed so often is a different one: in 83 per cent of cases, people with agenesis are missing one or two teeth, no more. The tooth most frequently absent is the lower second premolar, followed by the upper lateral incisor and the upper second premolar. When the lateral incisor is missing, it is often missing symmetrically: in this specific case bilateral agenesis is more common than unilateral, while still involving only one type of tooth.

An isolated absence, in a mouth that otherwise develops normally, is the kind of anomaly an untrained eye does not notice. If the space closes on its own, if a canine drifts sideways to fill it, if a baby tooth never falls out and stays there for years, unobtrusive, the visual result can be acceptable as long as no one asks the right question, which is not “why is this tooth missing?” but “did this tooth ever exist?”.

Why it happens to only one or two teeth, and not to all of them

The biology behind this selectivity is more interesting than the symptom it produces. The development of a tooth depends on a cascade of molecular signals, in particular the Wnt/beta-catenin, BMP, FGF and Sonic hedgehog pathways, which regulate the interaction between epithelium and mesenchyme in the first weeks of intrauterine life. A review published in 2026 proposes a threshold model: a tooth is initiated when the combined intensity of these signals exceeds a threshold specific to that region of the arch (Kuc et al., 2026). Different regions have different thresholds. The teeth that form last in each group, such as the lateral incisor compared with the central incisor, or the second premolar compared with the first, are those with the narrowest margin between development and failure to develop.

This explains why agenesis is rarely an all-or-nothing phenomenon: a minimal fluctuation in the signal can block a single borderline tooth without affecting the others. Among the most studied genes in non-syndromic forms are PAX9, MSX1 and WNT10A, alongside less well-known pathways linked to TNF receptor signalling and the mTOR pathway, as a recent review of the genetic picture of tooth agenesis indicates (Fallea et al., 2025). In most isolated cases, however, a genetic test is not needed: the diagnosis remains clinical and radiographic, and genetics helps to understand why the condition exists, not to decide how it is managed.

The cost of absence

In children and adolescents, the psychosocial impact of tooth agenesis has been measured with validated instruments. A 2013 study conducted at Birmingham Dental Hospital on eighty-six young people aged between eleven and fourteen compared oral quality of life, using the Child Perceptions Questionnaire, between those with agenesis and a control group with a complete dentition (Kotecha et al., 2013). The agenesis group reported significantly worse scores for oral symptoms, functional limitations and social and emotional well-being. What is interesting is that this gap was not correlated with the number of missing teeth: a single visible absence weighed as much as a more extensive condition.

On equivalent data in adulthood the literature is thinner, and it is right to say so openly rather than extend, by analogy, an unverified conclusion in the same way. What can be said, with caution, is that the underlying psychological mechanism, the association between visible dental appearance and self-perception, has no reason to disappear once a person comes of age. What changes, if anything, is the way it is managed: often through a silent form of compensation, a restrained smile, a habit of avoiding photographs that the adult has learned not to name even to themselves.

When the discovery comes late

An isolated agenesis, especially of the lateral incisor, can remain undiagnosed until adulthood for a wide variety of reasons: a space that closes spontaneously during growth, a baby tooth that stays in the arch without falling out, or simply the absence of a radiographic check at a time when it would have been useful. When the diagnosis comes late, the clinically relevant question is no longer “what is missing” but “how much biological and bone space remains available for treatment”. The facial skeleton continues to change until growth is complete, and an implant placed before this process has ended risks producing a progressive misalignment of the replaced tooth relative to the surrounding natural teeth, which instead continue to “move” with the bone.

This is one of the reasons why, in clinical practice, implant-prosthetic options are generally evaluated after skeletal growth is complete, a milestone that females tend to reach earlier than males, and which must in any case be verified case by case. For those who discover agenesis as adults, this constraint is no longer an issue. The window is already open. What remains is to decide how to go through it.

Close the space or reopen it? A decision that is not only clinical

When a lateral incisor is missing, the two main routes are orthodontic space closure, moving the canine into its place and reshaping it aesthetically, or keeping the space open with a prosthetic replacement that today, in most cases, is anchored to an implant. These are two different approaches, not just two techniques: the first accepts a permanent change to the oral architecture in order to simulate continuity, the second preserves the original oral anatomy by filling the gap with an artificial element.

Outcome data help, but they do not simplify the choice as much as one might wish. A 2023 systematic review of patients with lateral incisor agenesis associated with cleft lip and palate reports a five-year survival rate of 96.4 per cent for implant-supported prostheses (Clerc et al., 2023): an encouraging figure, to be read bearing in mind that the population studied had an associated condition, not isolated agenesis, and that the meta-analysis is based on case series, not on randomised controlled trials. A study from the same year instead compared the overall societal costs, direct and indirect, of the two strategies over a twelve-year period, finding a significant advantage, in both the short and the long term, in favour of orthodontic space closure, although the study is based on a limited sample of thirty-two patients, was conducted within the Swedish healthcare and tax system, and the authors themselves point out that the transferability of the economic data to other settings may be limited (Hedmo et al., 2023).

Taken together, this body of evidence does not point to a single answer, and it would be wrong to make it look as if it did. Rather, it indicates that the decision depends on factors that go beyond the clinical picture alone: the starting occlusion, the degree of dental crowding, the shape, colour and size of the canine to be adapted, the person’s aesthetic expectations, and the time and resources they are willing to invest in one path rather than the other. It is a decision that resembles the irreversible ones we make in life with incomplete information, where neither path is wrong, but only one will actually be taken and the other will remain a hypothesis that can never be tested.

The director behind the reconstruction

When the choice falls on the implant-prosthetic solution, the treatment pathway rarely involves a single professional. A study conducted in Beijing on ten patients with multiple agenesis, treated with an integrated approach combining orthodontics, prosthodontics and, where necessary, orthognathic surgery, followed the results for an average of just over nine years after completion of the prosthetic phase, with limited marginal bone resorption and only two minor complications, both resolved, across the ten patients (Hu et al., 2011). The interesting point in studies like this one is not so much the success rate as the sequence: the orthodontic diagnosis defines the available space, surgery intervenes if the bone or the jaws require it, and the prosthetic phase comes last, giving form and function to a plan built step by step by several different hands.

In these cases the prosthodontist often takes on a role that goes beyond technical execution alone: they are the figure who holds the sequence together, who decides when a phase is truly complete and the next one can begin. A role closer to that of a director than to that of a single actor. This is not an organisational detail. It is what distinguishes a case that is well managed from one that is simply completed.

A true absence

There is a way of looking at all this that is worth making explicit. When adults discover that they have agenesis, they are not losing something: they are learning a fact that has always concerned them, ever since intrauterine life, when that tooth should have begun to form and did not. The diagnosis is not a physiological event. It is an event of knowledge. The body does not change at the moment an X-ray is taken: only what the person knows about themselves changes.

It is a distinction with practical consequences, not only philosophical ones. Someone facing an agenesis discovered late is not chasing a recent loss, with the emotional urgency that often comes with it, but is receiving, a few decades late, information that had always been there, written in their genetic make-up even before it was written in their mouth. Perhaps this is also why many people, faced with this late diagnosis, react not with alarm but with a kind of relief: at last someone has put a name to something that, in a corner of their awareness, they had always known they could not fully explain.

How many other features of our bodies, present from the very beginning, are simply waiting for someone to ask the right question before they are seen?

Frequently asked questions

Is a missing wisdom tooth a problem that needs treatment? In almost every case, no: it is a borderline case, the most common form of agenesis of all, and it rarely changes anything in a person’s life.

Why can agenesis go unnoticed for decades? Because in 83 per cent of cases only one or two teeth are missing, and the space may close on its own, be taken up by a canine that drifts sideways, or be masked by a baby tooth that stays in the arch without falling out.

Can someone who discovers agenesis as an adult still be treated? Yes: the skeletal growth constraint, which in younger patients means waiting before an implant can be placed, has already been passed in an adult. What remains is to assess the available biological and bone space and to choose, case by case, between orthodontic space closure and prosthetic replacement.

Who coordinates the treatment pathway when several specialists are needed? In cases treated with an implant-prosthetic solution, the prosthodontist often acts as the director of the sequence: deciding when one phase is complete and the next can begin, together with orthodontics and, where necessary, surgery.

Tooth agenesis: when it is discovered in adulthood