Teeth keep moving throughout adult life. In one study, 20 years after treatment ended, only 10% of cases still held an alignment judged acceptable: the bonded wire or the retainer worn after orthodontic treatment should be discussed before you begin.
If you are considering orthodontic treatment, or if you want a second opinion on a plan you have been offered, Noria Health Hub can arrange a full check-up or a second medical opinion in Brussels, with a report within 24 h, coordinate your care where needed across more than 40 medical pathways in 48 h, then, if your medical condition allows, arrange surgery within 7 days.
Orthodontics: oral health benefits that have not been solidly demonstrated
We have to start there, because it is the most often asserted and the least often demonstrated.
| What is measured | The result |
|---|---|
| Effect of orthodontics on gingival recession | +0.03 mm, a small unfavourable effect |
| Effect on alveolar bone loss | +0.13 mm, unfavourable |
| Effect on pocket depth | +0.23 mm, unfavourable |
| Effect on caries | In young people, fixed appliances appear to reduce incidence. In adults, they raise it. Most studies find no difference |
| Psychosocial benefit under 18, 13 studies | Standardised difference of 0.75, emotional wellbeing 0.61, social wellbeing 0.62, low to moderate evidence |
The reference review concludes there is no reliable evidence of positive effects on periodontal health, and that small unfavourable effects exist. The only reasonably established benefit is psychosocial.
There is one functional exception with a solid epidemiological base, and it must be given. A large incisor overjet raises the risk of dental trauma, with an odds ratio of 2.01 beyond 3 to 4 millimetres and 2.24 beyond 6 millimetres. A meta-analysis of 54 studies estimates that 21.8% of the global burden of dental trauma is attributable to large overjet. It is the only quantified health indication we will put forward.
Aligners or fixed appliances: accuracy of movement and clinical effectiveness
Three syntheses conclude differently, and we prefer to explain why rather than pick the convenient one.
| The synthesis | What it finds |
|---|---|
| 11 studies, 887 patients, adults and broad cases | Lower final occlusal quality with aligners, a gap of 9.9 points, and 1.6 times more results judged unacceptable |
| 8 studies, including 2 randomised trials | Treatment 6.31 months shorter with aligners, occlusal quality at the edge of significance |
| 21 randomised trials, 970 patients, simple non-extraction cases | No difference in occlusal quality, alignment or duration |
The honest formulation is this. On a simple non-extraction case, equivalence. On a complex case, the advantage goes to fixed appliances. And the level of evidence is low to moderate in all 3 cases.
What is well documented, by contrast, is the gap between what the software promises and what is obtained. Across 37 patients and 401 anterior teeth, the mean accuracy of planned movements was 41%. A more recent study with a different material finds 50%. The breakdown by movement is the most useful part.
| The movement | Accuracy obtained against plan |
|---|---|
| Extrusion, pulling a tooth out of its socket | 29.6%, the worst movement |
| Rotation of a maxillary canine | 47.9% |
| Rotation of a mandibular canine | 49.9% |
| Rotation of mandibular incisors | 70.7% |
| Canine rotation beyond 15 degrees | Accuracy drops significantly |
These figures do not disqualify aligners. They explain why a treatment plan on a screen is not a result, and why refinements mid-treatment are the rule rather than the exception.
One methodological reservation. The 2 most cited accuracy studies come from the same lead author, on 37 and 38 patients, using the manufacturer’s proprietary software. They are reproduced but they are not independent.
Relapse: retention, meaning the bonded wire or the removable retainer that stops teeth shifting again, remains necessary in the long term
No patient should start treatment without knowing these 2 lines.
| What is measured | The result |
|---|---|
| Acceptable mandibular alignment 10 years after retention ends, 65 cases | About one third |
| Acceptable mandibular alignment 20 years later, 31 cases | 10% |
| Nature of the phenomenon, over 600 records followed 35 years | Crowding continuing to age 20 to 40, with no identified predictive variable |
| Bonded wire against full-time removable retention, alignment index at 12 months | A difference of 0.60 mm, below the threshold of clinical relevance |
| Gingival health, removable retention against bonded wire | Better with removable, bleeding risk ratio 0.53 |
Lower incisor crowding is a continuous phenomenon of adult life, in treated people as much as in those never treated. No pre-treatment variable predicts it. The practical consequence is simple, retention is not a phase, it is a state.
The most recent Cochrane review on retention covers 47 studies and 4,377 participants and concludes to low or very low certainty for every comparison. No strategy is demonstrated superior. And none of those studies includes aligners.
The risks: what the studies allow us to quantify
| What is measured | The result |
|---|---|
| Resorption of the root tips, 8 studies | Prevalence of 65.6% to 98.1%, mild to moderate severity, under 4 mm |
| Correlation with total apex displacement | 0.822 |
| Correlation with treatment duration | 0.852 |
| Resorption, aligners against fixed appliances, 6 studies, 392 patients | 0.50 mm less with aligners, low certainty |
| White demineralisation spots under fixed appliances, 14 studies | New lesion incidence 45.8%, prevalence 68.4% |
Almost everyone resorbs a little root, and it remains inconsequential in the vast majority of cases. What increases resorption is measured, it is the distance travelled by the apex and the duration of treatment, not the brand of the device.
We will not give a percentage of severe resorption, because reviews report that severity stays under 4 millimetres without giving a pooled proportion. And we will not give a percentage of patients in pain, because we found no verifiable meta-analytic figure on that point, despite an abundant literature.
Clear aligners ordered online: why a clinical examination remains essential
We cover this because it is a large phenomenon and because the official positions are clear and verifiable.
The British regulator points out that treatment with clear aligners remains a dental procedure. The decision must rest on a full assessment of the mouth; there is no effective substitute for a physical clinical examination as the basis of that assessment. Depending on the situation, recent radiographs and the medical history may also be needed.
On complications, only what is measured should be given. A survey of 470 users finds 87.5% satisfied and 6.6% who had to consult their dentist because of the severity of adverse effects. The 13% figure in circulation was not found in a primary source, and we will not quote it. Nor did we find a published official position from a French-speaking or Belgian professional body on this subject, and we flag that rather than invent it.
Three common beliefs the studies do not confirm
Orthodontics and the jaw joint. A prospective cohort of 1,018 people followed 20 years, from age 11 to 31, finds no association between orthodontic treatment and the onset of a joint disorder, nor with a persistent one. The only predictors at 31 are female sex and having had a disorder in adolescence. Orthodontic treatment neither causes nor prevents these disorders.
Wisdom teeth and late crowding. A randomised trial of 164 patients, 77 of whom were reviewed after a mean of 66 months, measures a reduction in crowding increase of 1.1 millimetres against 2.1 in the group where wisdom teeth were kept. The difference is neither statistically nor clinically significant, and the authors conclude that removing wisdom teeth to prevent crowding cannot be justified.
Premolar extraction and profile. On stability, a trial of 66 patients finds no difference in relapse at 5 years between extracting 2 and 4 premolars. On profile, the available evidence is of low to very low quality and we will not settle it with figures the literature does not provide.
Adult orthodontics: the state of the periodontium is decisive
The share of adults is rising, and the available figures come from professional surveys with a low response rate, around 6.6%. These are market data and we present them as such, about 1 orthodontic patient in 3 is over 18.
The clinical point that matters in adults is the interaction with the periodontium. A review of 15 studies and 528 patients shows that combined orthodontic and periodontal treatment on a reduced but healthy periodontium reduces pocket depths and gains attachment. The condition is in the word healthy. Moving teeth on an untreated inflamed periodontium is not the same operation.
Jaw surgery: indications, benefits and the limits of the data
When the discrepancy between the jaws is too great to be compensated by the teeth, surgery becomes the only option. It has a measured functional result that goes well beyond aesthetics.
| What is measured, maxillomandibular advancement for sleep apnoea | The result |
|---|---|
| Reduction in the apnoea index, 45 studies, 518 patients | Minus 47.8 events per hour, a fall of 80.1% |
| Share of patients improved | 98.8% |
| Surgical success, more than halved to under 20 events per hour | 85.5% |
| Cure, index under 5 | 38.5% |
| Share of patients who had already had other apnoea surgery | 73.5% |
The last line matters. These results were obtained in patients for whom other approaches had failed, which makes the figure more striking still, and which forbids transposing it to an unselected population.
On skeletal relapse after surgery, we found no recent quantified meta-analysis. The available sources are qualitative. We will therefore not put a percentage on surgical relapse.
What the studies do not allow us to claim
We will not claim that straight teeth decay less or last longer, because the reference review concludes to an absence of evidence and to small unfavourable periodontal effects. You will not read here that orthodontic treatment cures jaw pain, because a 20 year cohort says otherwise. Nothing entitles us to write that an aligner does as well as a fixed appliance on a complex case.
What we will say is that the psychosocial benefit is real and measured, that reducing a large overjet has a solid epidemiological base, and that at 20 years without retention, only 10% of alignments remain acceptable. That last figure should be given before starting, not after.
In practice, if this concerns you
You set out your problem, your symptoms or your question. Reports, test results and images already available can be studied before you arrive, so that the pathway is prepared. The aim is not to run every possible test, but to select those that can genuinely help confirm a hypothesis, rule out a risk or guide the decision. The results are then brought together and the next steps organised. Follow-up is coordinated from there.
Request an orthodontic opinion
Need a medical opinion quickly? For a concern that does not call for emergency services, you can ask to speak to a doctor at any time through Noria Health Hub. This on-demand medical consultation is billed separately from the work-up pathway.
Further reading
The companion articles.
Wisdom” rel=”noopener” target=”_blank”>https://noriahealth.com/blog/wisdom-teeth-jaws-and-cone-beam-what-the-evidence-says/”>Wisdom teeth, the jaw and cone beam CT: what the evidence shows
Caries” rel=”noopener” target=”_blank”>https://noriahealth.com/blog/caries-the-most-widespread-and-the-least-well-decided/”>Caries, the most widespread disease
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