Why Teeth Can Move After Braces: Jaw Growth, Explained by a Specialist

A finished orthodontic result is a photograph of one moment. The teeth are straight, the bite meets, everyone is pleased. Then the child keeps growing, because that is what children do, and a few years later the picture can look different. Parents understandably ask what went wrong. Often the honest answer is that nothing went wrong with the treatment: the jaws kept growing after it ended, in a direction nobody could have seen coming. This post explains how that happens, using the research rather than opinion.

The short answer

Teeth can move after braces for two reasons that often act together. The jaws keep growing after treatment ends, sometimes into the early twenties, and the direction of that growth cannot be predicted from a childhood x-ray. And teeth drift with age in everyone, braces or not, which is what retainers are for. Two growth patterns do most of the damage to a finished result: long-face growth, which can reopen the bite at the front, and Class III growth, where the lower jaw keeps growing ahead of the upper. Neither is caused by the treatment, and neither is anyone's fault. The rest of this post shows the evidence for each of those sentences.

Braces move teeth. Jaws grow on their own timetable.

Braces and clear aligners line the teeth up inside the jaws. The jaws themselves, the maxilla (upper jaw) and the mandible (lower jaw), keep growing during treatment and for years after the braces come off. How much they grow, in which direction, and for how long is different for every child.

In a study of 103 children with an untreated Class III pattern (lower jaw ahead of the upper), the adolescent growth spurt in the lower jaw came between 10 and 12 years in girls and between 12 and 15 years in boys, and there was still considerable lower jaw growth relative to the upper after the spurt had passed.¹ In a larger study of 1,091 Class III records, significant change in lower jaw length continued until young adulthood, 18 years on average.²

Change does not end at 18. In untreated adults followed from 25 to 46 years of age, all the measured linear dimensions of the face increased and the teeth became more crowded. The authors describe these changes as part of the normal maturational process.³ The American Association of Orthodontists' consent form says the same thing in one line: tooth position can change because of "growth and maturation that continue throughout life".⁴

Growth cannot be predicted from a childhood x-ray

The lower jaw does not simply get longer. As it grows it also rotates, forward in some people and backward in others. The classic implant studies by Björk and Skieller, carried out over 25 years, describe these rotations and show that the way they combine differs from one person to the next.⁵

Can an orthodontist read the future direction off the x-ray taken before treatment? This has been tested. A published method for predicting jaw rotation from a pre-treatment x-ray was applied to 40 untreated adolescents, with follow-up x-rays six years later. The predictor measurements together explained only 9 percent of the rotation that actually happened, and the authors concluded that the method "does not permit clinically useful predictions to be made in a general population".⁶ A separate study of long-faced and short-faced children from 4 to 18 years reached the same conclusion about the single most-used measurement, the mandibular plane angle, which it found "not adequate for assessment of diagnostic or prognostic predictive value in determining the pattern of growth".⁷

So an orthodontist plans from the growth pattern visible at the time and watches what unfolds. That is why we take new records at each stage, and why a plan can change.

Long-face growth

In some children the face grows more in height than in depth. The lower jaw rotates downward and backward as it grows, the lower face lengthens, and the front teeth can be carried apart until they no longer meet, which orthodontists call an anterior open bite.

Longitudinal x-rays of children from 3 to 18 years show that open-bite faces and deep-bite faces follow "typologically divergent patterns of development", with the timing of the growth spurt differing between the two and between girls and boys. The author notes this bears on the timing of treatment, on "the length of retention period", and on how well the adult bite can be predicted while a child still has baby teeth.⁸ The same author's study of facial angles found the open-bite pattern distinguishable from the deep-bite pattern throughout development and described the downward and backward rotation of the lower jaw in open-bite children as "precommitted".⁷

Treated open bites show what this pattern can do afterwards. Forty-one patients treated for an open bite were re-examined at least nine and a half years after their retainers were finished. More than 35 percent had an open bite of 3 millimetres or more again. The patients whose bite had reopened were the ones whose lower face had grown longer and whose back face height was shorter. "Neither the magnitude of pretreatment open bite, mandibular plane angle, nor any other single parameter of dentofacial form proved to be a reliable predictor of posttreatment stability."⁹

Class III growth: when the lower jaw keeps going

In a Class III pattern, the one behind an underbite, the lower jaw grows larger, or further forward, than the upper jaw, or the upper jaw is smaller than the lower. The lower front teeth can end up level with, or in front of, the upper front teeth, and the chin can look prominent. It is a pattern of bone growth, not a problem of tooth position alone.

Children with a Class III pattern followed from 6 to 16 years, compared with matched children with a normal bite, showed a jaw relationship that "worsens over time". The discrepancy was "primarily due to excessive mandibular growth", the gap in boys was larger than in girls, and it grew with age.¹⁰ The 103-child study reached the same finding: a "definite worsening of the relative mandibular prognathism and sagittal skeletal discrepancy between the jaws with growth".¹

The extra growth comes late. In the 1,091-record study, increases in lower jaw length between the late maturation stages were twice those of normal-bite girls and three times those of normal-bite boys, and the trend toward a more pronounced Class III profile and a longer face appeared at the stages when the second and third molars complete their eruption.² In Japanese boys and girls followed for three years after the pubertal growth peak, the features of the prominent lower jaw established before the peak were "strongly maintained".¹¹

Early treatment corrects the bite at the time. In the years afterwards, treated children have been found to grow in much the same way as untreated Class III children. Thirty-four children treated with an expander and a facemask before the growth spurt, then followed to an average age of 14 years 10 months, kept the correction gained during the ten months of active treatment; during the years afterwards, which included the growth spurt, they "grew similarly" to untreated Class III children, whose jaw discrepancy widened by a further 3 millimetres.¹² In another series, 41 children treated with a facemask were followed for five years, and 18 of them for ten. Seventy-five percent kept a positive overjet; 25 percent "outgrew the correction", mainly "because of increased horizontally directed and often late mandibular growth".¹³

So a child treated successfully at 8 or 9 can still grow into a Class III relationship at 14 or 15, because the jaw growth that creates it happens after the early treatment has finished. Where a significant jaw discrepancy remains once growth is complete, the profession's consent document describes the accepted options: further orthodontic treatment, or orthodontic treatment combined with jaw surgery.⁴

The Habsburg jaw: a famous family, a very common pattern

The best-known example of a Class III growth pattern is a royal one. The Habsburgs ruled much of Europe for centuries and were painted by the finest artists of their day, so their faces are on record in a way few families' are. Many of them share a forward lower jaw and a small upper jaw, a look so consistent across the generations that it has its own name, the Habsburg jaw. Philip IV of Spain, at the top of this page, carries it with real presence in Velázquez's 1644 portrait, and his great-grandfather Charles V, below, painted by Titian more than a century earlier, shows the same jaw.

In 2019 a team of surgeons and geneticists assessed 66 portraits of 15 members of the dynasty. They found a strong link between the forward lower jaw and the small upper jaw, which is why the two so often appear together, and a link between the degree of the forward lower jaw and how closely related the family's marriages had been over the generations.¹⁴ Outside royal families, a forward lower jaw runs in ordinary families too. A study of 2,562 people across 55 families found the trait clustering in families in a pattern consistent with a major gene, an inherited tendency that not every family member goes on to show.¹⁵

Two things about this are worth saying gently. The Habsburgs were painted, not chosen; the pattern is common, and most people who have it have never sat for a portrait. And a growth pattern is inherited, not caused. It is nobody's fault: not the child's, not the parents', not the orthodontist's. Knowing that it runs in a family is useful, because it tells us to watch growth closely, and for longer.

Teeth move in everyone, braces or not

Movement of the teeth after orthodontic treatment is common in every kind of patient, and the long-term studies find it unpredictable. Sixty-five patients treated with braces and premolar extractions were examined at least ten years after retention ended. Their long-term lower front alignment was "unpredictable; no variables, such as degree of initial crowding, age, sex, Angle classification, etc., were useful in establishing a prognosis", and two thirds had unsatisfactory lower front alignment.¹⁶ In a further 31 patients followed to twenty years after retention, crowding had continued to increase and only 10 percent had clinically acceptable lower alignment. The cases "responded in a diverse unpredictable manner with no apparent predictors of future success".¹⁷

People who never had braces show the same drift. Sixty-five untreated normal bites followed from 9 to 20 years of age showed decreasing arch length, decreasing width between the canines, and increasing crowding of the front teeth, changes "similar in nature but lesser in extent" than those seen after treatment.¹⁸ Over 45 years of follow-up, the width of the dental arches after all the adult teeth are through either stays the same or decreases slightly; the authors add that "both patients and clinicians should be aware of these limitations".¹⁹

This is why retainers are prescribed. The Cochrane review of retention states the starting point plainly: "Without a phase of retention after successful orthodontic treatment, teeth tend to 'relapse', that is, to return to their initial position."²⁰ And it is why the profession's consent form tells families before treatment starts that "completed orthodontic treatment does not guarantee perfectly straight teeth for the rest of your life", and that "late in life, most people will see their teeth shift".⁴

What we do when growth has changed a result

First, new records: photographs, a scan of the teeth and, where one is indicated, an x-ray, compared with the records from the day treatment finished. They show exactly what has moved, and whether the change is in the teeth, in the jaws, or both.

Second, we establish whether growth has finished. Skeletal maturity can be staged from the neck vertebrae on the side-on x-ray or from a hand-wrist x-ray, which is how the studies above timed the growth spurt.^{2, 11} While growth continues, the sensible course is to keep the retainers in and watch, rather than treat a moving target.

Third, once growth is complete, we choose. For a change in the teeth, a short course of treatment to realign them. For a change in the jaws themselves, a combined plan with an oral and maxillofacial surgeon. We refer, we plan the orthodontic side, and we time the surgery for after growth has finished so that later growth does not undo the result. Our jaw surgery page explains how that works.

Questions parents ask

Why have my child's teeth moved after braces?

Two reasons, often together. The jaws kept growing after treatment ended, and teeth drift in everyone with age, braces or not. New records compared with the records from the day the braces came off show which one is doing the moving.

Can jaw growth undo orthodontic treatment?

Yes. Braces move teeth; they cannot control how the jaws grow afterwards. In children treated early for an underbite with a facemask, one in four outgrew the correction because the lower jaw kept growing, often late in the teens.¹³

Did the braces fail?

If the teeth and jaws were aligned when the braces came off, and the records show the change since is in jaw growth, the treatment did what treatment can do. Braces move teeth. They cannot decide how a jaw will grow.

Should we have waited until growth finished?

For many problems waiting has its own costs, and early correction holds in most children. The difficulty is that no measurement taken beforehand reliably shows which child's growth will outrun it.^{6, 9}

Why wait until about 21 for jaw surgery?

Lower jaw growth in a Class III pattern can continue into young adulthood, and surgery done while growth continues can be undone by it. Waiting until growth has clearly stopped protects the result.²

What is the Habsburg jaw?

The forward lower jaw and small upper jaw seen across generations of the Habsburg royal family, recorded in their portraits. A 2019 study of 66 portraits found the two travel together and that the pattern is inherited. The same pattern runs in ordinary families and is nobody's fault.^{14, 15}

Do retainers still matter if the jaws are the problem?

Yes. Retainers hold the teeth where they are. They do not stop jaw growth, but they stop the teeth adding their own drift on top of it.²⁰

Talk to us

If your child finished treatment with us and something has changed, book a review. We take the records, compare them with the day the braces came off, and talk it through with you and your dentist together. If your child has not started treatment yet and you want an honest read on their growth pattern, book a free Smile Assessment with our Treatment Coordinator at Newmarket or Albany, online, or by video call. Call us on (09) 520 1880 or book online.

References

Numbered in the order they are first cited. Each source was checked against its PubMed record, the Cochrane Library record or the published form before it was used. Search the PMID at pubmed.ncbi.nlm.nih.gov.

1. Alexander AE, McNamara JA Jr, Franchi L, Baccetti T. Semilongitudinal cephalometric study of craniofacial growth in untreated Class III malocclusion. American Journal of Orthodontics and Dentofacial Orthopedics 2009; 135(6): 700.e1-14. PMID 19524825. doi 10.1016/j.ajodo.2008.06.025
2. Baccetti T, Reyes BC, McNamara JA Jr. Craniofacial changes in Class III malocclusion as related to skeletal and dental maturation. American Journal of Orthodontics and Dentofacial Orthopedics 2007; 132(2): 171.e1-12. PMID 17693366. doi 10.1016/j.ajodo.2005.07.031
3. Bishara SE, Treder JE, Jakobsen JR. Facial and dental changes in adulthood. American Journal of Orthodontics and Dentofacial Orthopedics 1994; 106(2): 175-186. PMID 8059754. doi 10.1016/S0889-5406(94)70036-2
4. American Association of Orthodontists. Informed Consent for the Orthodontic Patient: Risks and Limitations of Orthodontic Treatment. 2024 edition, form ICS200515. aaoinfo.org
5. Björk A, Skieller V. Normal and abnormal growth of the mandible. A synthesis of longitudinal cephalometric implant studies over a period of 25 years. European Journal of Orthodontics 1983; 5(1): 1-46. PMID 6572593. doi 10.1093/ejo/5.1.1
6. Leslie LR, Southard TE, Southard KA, Casko JS, Jakobsen JR, Tolley EA, Hillis SL, Carolan C, Logue M. Prediction of mandibular growth rotation: assessment of the Skieller, Björk, and Linde-Hansen method. American Journal of Orthodontics and Dentofacial Orthopedics 1998; 114(6): 659-667. PMID 9844205. doi 10.1016/s0889-5406(98)70198-2
7. Nanda SK. Growth patterns in subjects with long and short faces. American Journal of Orthodontics and Dentofacial Orthopedics 1990; 98(3): 247-258. PMID 2403077. doi 10.1016/S0889-5406(05)81602-6
8. Nanda SK. Patterns of vertical growth in the face. American Journal of Orthodontics and Dentofacial Orthopedics 1988; 93(2): 103-116. PMID 3422525. doi 10.1016/0889-5406(88)90287-9
9. Lopez-Gavito G, Wallen TR, Little RM, Joondeph DR. Anterior open-bite malocclusion: a longitudinal 10-year postretention evaluation of orthodontically treated patients. American Journal of Orthodontics 1985; 87(3): 175-186. PMID 3856391. doi 10.1016/0002-9416(85)90038-7
10. Wolfe SM, Araujo E, Behrents RG, Buschang PH. Craniofacial growth of Class III subjects six to sixteen years of age. Angle Orthodontist 2011; 81(2): 211-216. PMID 21208071. doi 10.2319/051010-252.1
11. Mitani H, Sato K, Sugawara J. Growth of mandibular prognathism after pubertal growth peak. American Journal of Orthodontics and Dentofacial Orthopedics 1993; 104(4): 330-336. PMID 8213653. doi 10.1016/S0889-5406(05)81329-0
12. Westwood PV, McNamara JA Jr, Baccetti T, Franchi L, Sarver DM. Long-term effects of Class III treatment with rapid maxillary expansion and facemask therapy followed by fixed appliances. American Journal of Orthodontics and Dentofacial Orthopedics 2003; 123(3): 306-320. PMID 12637903. doi 10.1067/mod.2003.44
13. Wells AP, Sarver DM, Proffit WR. Long-term efficacy of reverse pull headgear therapy. Angle Orthodontist 2006; 76(6): 915-922. PMID 17090164. doi 10.2319/091605-328
14. Vilas R, Ceballos FC, Al-Soufi L, González-García R, Moreno C, Moreno M, Villanueva L, Ruiz L, Mateos J, González D, Ruiz J, Cinza A, Monje F, Álvarez G. Is the "Habsburg jaw" related to inbreeding? Annals of Human Biology 2019; 46(7-8): 553-561. PMID 31786955. doi 10.1080/03014460.2019.1687752
15. Cruz RM, Krieger H, Ferreira R, Mah J, Hartsfield J Jr, Oliveira S. Major gene and multifactorial inheritance of mandibular prognathism. American Journal of Medical Genetics Part A 2008; 146A(1): 71-77. PMID 18074368. doi 10.1002/ajmg.a.32062
16. Little RM, Wallen TR, Riedel RA. Stability and relapse of mandibular anterior alignment: first premolar extraction cases treated by traditional edgewise orthodontics. American Journal of Orthodontics 1981; 80(4): 349-365. PMID 6945805. doi 10.1016/0002-9416(81)90171-8
17. Little RM, Riedel RA, Artun J. An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention. American Journal of Orthodontics and Dentofacial Orthopedics 1988; 93(5): 423-428. PMID 3163221. doi 10.1016/0889-5406(88)90102-3
18. Sinclair PM, Little RM. Maturation of untreated normal occlusions. American Journal of Orthodontics 1983; 83(2): 114-123. PMID 6572039. doi 10.1016/s0002-9416(83)90296-8
19. Bishara SE, Jakobsen JR, Treder J, Nowak A. Arch width changes from 6 weeks to 45 years of age. American Journal of Orthodontics and Dentofacial Orthopedics 1997; 111(4): 401-409. PMID 9109585. doi 10.1016/s0889-5406(97)80022-4
20. Martin C, Littlewood SJ, Millett DT, Doubleday B, Bearn D, Worthington HV, Limones A. Retention procedures for stabilising tooth position after treatment with orthodontic braces. Cochrane Database of Systematic Reviews 2023; Issue 5: CD002283. PMID 37219527. doi 10.1002/14651858.CD002283.pub5