Hypophosphataemia and Orthodontics UK

What is X-linked hypophosphataemia?

X-linked hypophosphataemia is a rare inherited condition caused by a mutation in the PHEX gene, leading to overproduction of a hormone called FGF23. Excess FGF23 causes the kidneys to waste phosphate, resulting in chronically low blood phosphate levels. Because phosphate is essential for mineralising bone and teeth, XLH causes rickets-type bone changes in growing children and a characteristic pattern of dental defects that are present in the vast majority of people with the condition, regardless of how well their bone disease is managed.

Spontaneous dental abscesses without caries

One of the most distinctive dental features of XLH is the development of spontaneous tooth abscesses in teeth that have no cavities and appear otherwise structurally sound. This happens because the pulp chamber and root canals in XLH teeth are often abnormally large, with the pulp tissue extending close to the outer surface of the tooth (a pattern sometimes described as pulp horns reaching almost to the enamel-dentine junction). This makes the pulp vulnerable to bacterial infection through microscopic defects in the enamel and dentine that would not normally allow bacteria through, causing abscesses to form without the usual warning sign of visible decay.

Enamel hypoplasia and dentine defects

Alongside the abscess risk, XLH commonly causes enamel hypoplasia — enamel that is thinner or less well mineralised than normal — and interglobular dentine, a defect in dentine mineralisation that leaves microscopic channels through which bacteria can track towards the pulp. Together, these defects mean XLH teeth are structurally more fragile and more vulnerable to pulp infection than typical teeth, even with good oral hygiene and a low-sugar diet. This is a direct consequence of the underlying mineralisation defect rather than a sign of neglect.

Why dental assessment must come before orthodontic forces

Because XLH teeth carry an elevated risk of spontaneous pulp infection, applying orthodontic forces to teeth with undiagnosed pulp involvement can be more likely to provoke or worsen an abscess. For this reason, a thorough dental assessment — including radiographs to check for early signs of pulp pathology — and treatment of any teeth needing root canal treatment or restoration is generally completed before starting orthodontic treatment, rather than proceeding directly to braces or aligners. Ongoing dental review continues throughout orthodontic treatment given the lifelong abscess risk.

Impaired mineralisation and orthodontic tooth movement

Some evidence and clinical experience suggests that the underlying mineral metabolism disturbance in XLH can also affect the alveolar bone that orthodontic forces act on, which may influence the pace or predictability of tooth movement in some patients. This is not a reason to avoid orthodontic treatment, but orthodontists managing XLH patients typically build in closer monitoring and may adjust force levels or treatment timelines based on how teeth are responding, rather than assuming standard rates of movement will apply.

Burosumab and its relevance to dental and orthodontic care

Burosumab is an anti-FGF23 monoclonal antibody available on the NHS for children and, more recently, some adults with XLH, and it directly targets the underlying hormonal cause of the condition rather than just replacing lost phosphate. By normalising phosphate handling, burosumab has been associated with improved bone mineralisation in some studies, and there is growing interest in whether it also improves dental mineralisation, particularly when started early in childhood. This is an evolving area, and whether or how burosumab affects dental defect severity or orthodontic planning is a conversation to have with the patient's metabolic bone specialist and dentist together.

Coordinating XLH dental, medical, and orthodontic care

XLH is managed by a metabolic bone or endocrinology team, often within a specialist NHS centre, and effective dental and orthodontic care depends on good communication across this multidisciplinary group. Sharing information about current treatment (conventional phosphate and vitamin D therapy, or burosumab), recent dental abscess history, and any planned changes in medical management helps the orthodontist time treatment appropriately and stay alert to the abscess risk that is specific to XLH rather than treating it as a routine malocclusion case.

Useful related pages

This guide is for general information only. It is not a diagnosis, treatment plan, or substitute for advice from a registered dentist or orthodontist.