Prader-Willi Syndrome and Orthodontics UK

How hypotonia shapes the bite in PWS

Low muscle tone (hypotonia) is a defining feature of Prader-Willi syndrome and has direct consequences for dental development and bite. Weak orbicularis oris (the lip muscle) and tongue tone allow the tongue to rest low and forward in the mouth, applying persistent outward pressure on the lower front teeth and failing to provide the balancing inward lip pressure that normal muscle tone delivers. The result is a tendency toward anterior open bite — a gap between the upper and lower front teeth when the back teeth close — and anterior spacing as teeth spread under tongue pressure. Posterior crossbite may also develop because the upper arch narrows without adequate cheek and tongue muscle equilibrium. These are not unusual presentations of orthodontic problems; they are the direct muscular consequence of the syndrome and should be monitored from early childhood.

Hyperphagia, rampant caries, and why oral health must come first

The compulsive food-seeking behaviour characteristic of PWS — hyperphagia — is driven by a neurological failure of satiety signalling, not appetite in the conventional sense. Children and adults with PWS may consume food continuously when access is uncontrolled, and this has severe dental consequences. Frequent sugar exposure feeds the bacterial acid production that causes dental decay. In the context of PWS, this is further complicated by thick, viscous saliva that is less effective at neutralising acid and rinsing food residue from tooth surfaces. Rampant dental caries (rapid, widespread decay affecting multiple teeth simultaneously) is common in PWS, particularly in adolescence when dietary supervision may be less complete. No meaningful orthodontic treatment can proceed without first stabilising dental health — every active cavity must be treated, and a preventive regime of fluoride, diet counselling, and plaque control must be in place before and throughout any orthodontic phase.

Delayed and ectopic tooth eruption

Tooth eruption is commonly delayed in PWS, meaning that the normal sequence of dental development does not occur on the expected timeline. This affects treatment planning in several ways. First, fixed brace treatment is usually initiated once sufficient permanent teeth have erupted — if eruption is delayed, the window for interceptive or comprehensive orthodontics shifts later than in typically developing peers. Second, the abnormal position of the jaws and soft tissues can cause teeth to erupt in ectopic positions — outside the dental arch, in unusual angles, or impacted beneath the gum. Panoramic X-ray monitoring from approximately age 7 to 8 allows the orthodontic team to track eruption and plan timely intervention where needed. The treating orthodontist should communicate closely with the paediatric dentist and paediatric physician managing the child's wider care.

Class II skeletal tendency and growth hormone therapy

Many individuals with PWS have a Class II skeletal tendency — the lower jaw is relatively underdeveloped compared with the upper jaw, resulting in a significant overjet (prominent upper front teeth) and a receding chin profile. This reflects the hypotonic effect on mandibular growth during development. Growth hormone (GH) therapy, increasingly prescribed for children with PWS in the UK to improve stature, muscle mass, and metabolic function, also has a positive effect on mandibular growth. Published data suggest GH treatment improves lower jaw development, potentially reducing the severity of the Class II skeletal discrepancy. Orthodontists managing children with PWS should be aware of whether the child is on GH therapy and, if so, coordinate treatment timing to align comprehensive orthodontic care with the period of GH-stimulated growth. Functional appliances (twin block, Herbst, Forsus) used in growing Class II patients may be more effective during the growth phase supported by GH therapy.

Bracket adhesion challenges and thick saliva

Thick, viscous saliva in PWS reduces the effectiveness of the dry-field isolation needed for reliable composite bonding of orthodontic brackets. Standard moisture control techniques (cotton rolls, cheek retractors, air drying) remain appropriate, but clinicians should anticipate that brackets may debond more frequently in PWS patients than in the general orthodontic population. This has practical consequences: more repair appointments, potential disruption to the treatment plan if teeth are not consistently engaged, and additional chairside time per visit. Some clinicians prefer to use bands rather than bonded brackets on molar teeth in PWS patients, as bands do not rely on composite adhesion to enamel. Glass ionomer cement used as a fluoride-releasing bonding adjunct can also be considered. Families should be prepared for a higher incidence of bracket-related problems and factor this into scheduling plans.

Behavioural considerations and appointment management

Prader-Willi syndrome affects behaviour through several pathways. Rigidity (difficulty with changes to routine), impulsivity, food-related anxiety (particularly if the appointment is at or near a mealtime), and low frustration tolerance are common. These are not defiance — they reflect the neurological features of PWS and should be anticipated by the orthodontic team. Strategies that help include: scheduling appointments away from mealtimes, keeping appointment duration short where possible, using the same clinician and nurse throughout treatment to maintain familiarity, using clear advance warnings of what will happen at each visit, and involving carers fully in preparation and communication. If the child attends a specialist residential or day placement, liaising with that team about preparation strategies is often highly valuable. General anaesthesia for dental procedures is required more frequently in PWS than in the general population due to behavioural challenge — this has an important knock-on effect on treatment planning, as any planned extractions or restorative work that cannot be completed under local anaesthetic may need to be co-ordinated into a GA list.

Low pain threshold and sensitivity

Despite being known for a high pain threshold in some aspects (skin picking without apparent distress, for example), individuals with PWS can show heightened sensitivity in oral and peri-oral areas, particularly to unexpected tactile stimuli. Orthodontic treatment involves significant oral contact — fitting bands, placing brackets, taking impressions, inserting removable appliances. Many individuals with PWS have heightened sensitivity to mouth sensation and may resist instrumentation that neurotypical patients tolerate readily. Preparation through visual and social stories, slow introduction of new appliances at home before fitting, and a desensitisation schedule agreed with the clinical psychology team (if involved) can significantly improve cooperation. If a patient is unable to tolerate standard orthodontic procedures under normal clinical conditions, a clinical psychology referral or referral to a specialist paediatric or special care orthodontist with experience in complex needs management is appropriate.

Coordinated care with the PWS multidisciplinary team

PWS is managed by a multidisciplinary team that typically includes a paediatric endocrinologist (for GH therapy, obesity, and metabolic management), a paediatric psychiatrist or clinical psychologist (for behavioural support), a dietitian (for dietary restriction planning and hyperphagia management), a speech and language therapist, and where applicable an adult physician as the child transitions to adult services. The orthodontist is rarely at the core of this team but should communicate with it — particularly the endocrinologist regarding GH therapy timing and the clinical psychologist regarding behavioural support. In the UK, regional PWS clinical networks and the Prader-Willi Syndrome Association UK (PWSA UK) provide support and can facilitate information sharing between specialist teams when families request it.

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.