Ankylosing Spondylitis and Orthodontics UK

What is ankylosing spondylitis and why it affects orthodontic treatment

Ankylosing spondylitis (AS), also known as axial spondyloarthritis (axSpA), is a seronegative inflammatory arthritis primarily affecting the sacroiliac joints and spine, with a tendency to cause enthesitis — inflammation at the insertion points of tendons and ligaments into bone. In the context of orthodontic treatment, AS matters because: the temporomandibular joint (TMJ) is a synovial joint that can be affected by the same inflammatory process as other joints; the medications used to manage AS significantly alter bone metabolism; long-term inflammation can change alveolar bone density; and jaw stiffness from TMJ involvement can create practical difficulties during clinical procedures. Understanding these factors allows an orthodontist and rheumatologist to plan treatment that is both safe and effective.

TMJ involvement in AS: how common and what it means

Studies report TMJ involvement in approximately 10 to 35 per cent of AS patients, with a wide range reflecting differences in diagnostic criteria and study populations. TMJ involvement in AS presents as jaw pain, stiffness, restricted mouth opening, crepitus, and asymmetric jaw movement. In some patients, active TMJ inflammation causes condylar resorption — progressive loss of the condylar head similar to that seen in rheumatoid arthritis — which leads to progressive anterior open bite and bite instability. For orthodontic planning, the critical question is whether TMJ disease is active and progressive or inactive and stable. Active condylar resorption is a contraindication to starting orthodontic treatment aimed at correcting the bite, because any correction will be undermined by ongoing joint destruction. Stability should be confirmed on serial imaging — typically MRI or CBCT — over at least 12 months before committing to treatment.

How TNF inhibitors affect bone remodelling during orthodontics

Tumour necrosis factor inhibitors (TNFi) — including adalimumab, etanercept, infliximab, certolizumab pegol and golimumab — are the most widely used biological therapies for AS. TNF-alpha plays a central role in the inflammatory cascade that drives both osteoclastic bone resorption and, through RANKL/OPG signalling, osteoblastic bone deposition. Blocking TNF alters the balance of bone remodelling in complex ways. In periodontitis models, TNFi therapy has been shown to reduce periodontal bone loss. However, the effect on orthodontic tooth movement — which depends on a precisely calibrated cycle of osteoclastic resorption on the pressure side and osteoblastic deposition on the tension side — is not fully characterised. Clinically, some patients on TNFi appear to have slower or less predictable tooth movement than expected, while others respond normally. There is no consensus guidance for force levels in TNFi-treated patients. The prudent approach is to start with lighter forces than standard, extend appointment intervals, and monitor tooth movement objectively at each stage.

NSAIDs, bone density and tooth movement

Non-steroidal anti-inflammatory drugs (NSAIDs) — including ibuprofen, naproxen, diclofenac, and selective COX-2 inhibitors such as etoricoxib — are the first-line analgesic and anti-inflammatory treatment for AS. Long-term NSAID use has well-documented effects on bone biology. NSAIDs inhibit cyclooxygenase (COX) enzymes and thereby reduce prostaglandin synthesis. Prostaglandins are key mediators of the inflammatory response required for normal bone remodelling, including the resorption and deposition cycle that underlies orthodontic tooth movement. Animal studies have shown that NSAID administration significantly reduces the rate of orthodontic tooth movement. Clinical data in humans are more limited, but consistent long-term NSAID use — as is typical in AS management — is associated with slower tooth movement and potentially longer treatment timelines. Patients should inform their orthodontist of their NSAID regimen so that treatment expectations and wire sequencing can be adjusted accordingly.

Jaw stiffness and limited mouth opening: practical management

AS can affect the cervical spine and TMJ in ways that limit neck extension and jaw opening. Reduced maximum mouth opening — trismus or restricted temporomandibular movement — creates practical difficulties for orthodontic appointments. Impression-taking, bracket bonding, wire placement, and aligner scanning all require adequate mouth opening. Patients should inform the orthodontic team of any jaw stiffness, pain on opening, or restricted opening before appointments. Adjustments can include: using narrower impression trays or digital intraoral scanning (which requires less sustained opening than conventional impressions); positioning the patient semi-upright rather than fully reclined to reduce cervical spine discomfort; breaking longer appointments into shorter sessions; scheduling appointments during periods of lower disease activity (avoiding days of flare); and pre-medicating with pain relief as appropriate. Some patients benefit from physiotherapy or gentle TMJ mobilisation exercises before orthodontic appointments.

Coordinating with your rheumatologist before treatment

Before starting orthodontic treatment, patients with AS should request that their orthodontist and rheumatologist communicate directly. Key information the orthodontist needs includes: current medication regimen and any planned changes; disease activity score (BASDAI or ASDAS); whether the disease is currently in remission or active flare; whether there is any TMJ involvement and its current status; and whether there are any contraindications to dental procedures, including guidance on antibiotic prophylaxis if applicable. Many rheumatologists are unfamiliar with the specific orthodontic considerations for their patients and will welcome the opportunity to provide a structured summary. A letter from the orthodontist to the rheumatologist outlining the proposed treatment and asking specific questions is the most efficient approach. This liaison is not optional — it protects the patient and ensures both clinicians are working from the same information.

NHS referral pathway for AS patients needing orthodontics

Patients with AS who require orthodontic treatment follow the same NHS referral pathway as other adults, but with additional considerations. NHS orthodontics is not routinely available to adults in England — the NHS prioritises patients under 18 with a significant IOTN need. However, where AS-related TMJ involvement has caused malocclusion severe enough to require orthognathic (jaw) surgery in addition to orthodontics, there is a pathway through NHS hospital-based maxillofacial and orthodontic units. The GP should be the first point of contact, as they can refer to NHS oral and maxillofacial surgery for complex cases. Patients managing privately should ensure their orthodontist has experience with medically complex adults, as AS cases require modified protocols that not all practices routinely offer.

Monitoring during orthodontic treatment with AS

Patients with AS require more frequent monitoring during orthodontic treatment than otherwise healthy patients. The orthodontist should check at each appointment for signs of TMJ change — new asymmetry, changes in bite, or patient-reported increase in jaw symptoms. Any significant change in jaw alignment or bite during treatment warrants imaging and rheumatology review before adjustments continue. Periodontal health should be actively monitored, as AS and its treatments alter the immune response in ways that can affect gingival inflammation. Patients taking immunosuppressants should have their gum health assessed at every orthodontic appointment, not just at routine dental check-ups. If disease activity increases significantly during treatment, deferring orthodontic adjustments until the flare resolves is the safer approach.

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.