Facial Growth Modification in Orthodontics

What is facial growth modification?

Facial growth modification is the use of orthodontic appliances to alter the size, position, or direction of growth of the jaws during the period of active facial development in childhood and adolescence. The principle is that growing bone — unlike mature adult bone — responds to prolonged mechanical force by remodelling at sutures, condyles, and periosteum. Appliances can therefore guide jaw growth in a desired direction if used during the relevant growth window. Growth modification is distinct from tooth movement: it targets the skeletal framework rather than the teeth themselves, though the two are often combined in a phased treatment plan.

How do twin block and Herbst appliances treat Class II jaws?

Class II Division 1 malocclusion — where the lower jaw is underdeveloped or positioned too far back relative to the upper jaw — is the most common indication for mandibular advancement appliances. The twin block, developed by William Clark and widely used in UK practice, consists of upper and lower acrylic blocks that lock together when the patient bites, holding the lower jaw in a forward position during all jaw activity including eating and speaking. Worn full-time for 9 to 12 months, twin blocks stimulate adaptive remodelling at the mandibular condyle and glenoid fossa, physically lengthening and repositioning the lower jaw. The Herbst appliance is a fixed alternative that achieves the same mandibular repositioning without relying on patient compliance, as it is cemented in place. Both are most effective during the pubertal growth spurt.

How does a reverse-pull facemask treat Class III jaws?

Where the problem is an underdeveloped upper jaw rather than an overgrown lower jaw — or a combination of both — a reverse-pull facemask (protraction facemask) applies forward traction to the upper jaw. The appliance consists of a forehead and chin rest connected by a central frame, with elastic hooks that attach to a palatal expander bonded to the upper teeth. Worn 12 to 14 hours daily, it pulls the upper jaw forward and downward, stimulating growth at the circummaxillary sutures. It is most effective between ages 8 and 10, before these sutures begin to ossify. Earlier treatment (age 6 to 7) is possible but anchorage in the mixed dentition can be challenging. After age 12, response to facemask therapy diminishes significantly.

What does rapid maxillary expansion (RME) do?

Rapid maxillary expansion uses a fixed palatal expander to widen the upper jaw by separating the mid-palatal suture, which remains mobile until late adolescence (early to mid-20s in females, mid-20s or later in males). RME is used to correct posterior crossbite caused by a narrow upper arch, to create space for crowded teeth without extractions, and as a component of facemask therapy for Class III treatment. There is evidence that successful palatal expansion in children can improve nasal airway resistance, which may benefit mouth breathers. Expansion is typically rapid (one quarter-turn of the screw per day for two to four weeks) followed by a retention period of four to six months to allow bone to consolidate across the opened suture.

What does headgear do for maxillary restraint?

Orthodontic headgear applies rearward (and sometimes downward) force to the upper jaw to restrain forward maxillary growth in Class II cases where the upper jaw is genuinely protrusive rather than the lower jaw being deficient. It attaches to upper molar bands and connects to a neck pad or head cap, applying force via elastic traction. Headgear has become less commonly prescribed in UK practice than previously, partly due to compliance challenges and partly because functional appliances address the more common scenario of mandibular deficiency rather than maxillary excess. Safety considerations — headgear should always incorporate a safety release mechanism — are important, and it should only be used under orthodontic supervision.

When is the optimal timing for growth modification?

The pubertal growth spurt is the most important window for mandibular growth modification. Activating a twin block or Herbst appliance before or at the peak of the growth spurt produces significantly better skeletal outcomes than starting after peak growth has passed. Clinicians use several tools to identify growth status: hand-wrist radiographs (less used now due to radiation exposure), and cervical vertebral maturation (CVM) assessment using the lateral cephalometric radiograph already taken as part of orthodontic records. CVM identifies five stages of maturation based on the shape and concavity of the lower cervical vertebrae — stage 3 (CVM3) represents peak growth velocity and is the ideal time to begin mandibular advancement. CVM assessment is now standard practice in UK specialist orthodontics.

What can growth modification realistically change, and what can't it change?

Growth modification can meaningfully change the jaw relationship in growing patients, reducing overjet, improving chin position, and reducing the skeletal discrepancy that would otherwise require surgery in adulthood. However, it cannot completely eliminate a genetic growth pattern — a patient genetically programmed to have a significant Class III skeletal pattern will continue to grow that way despite early treatment, though usually to a lesser degree. Growth modification does not change facial bones in adults, whose sutures are fused and whose condylar growth is complete. The improvements gained in childhood may partially relapse if adverse growth continues through adolescence, which is why comprehensive fixed braces are almost always needed after a phase of growth modification.

Is growth modification available on the NHS or privately?

NHS orthodontic treatment is available for children under 18 meeting IOTN eligibility thresholds. Functional appliances, facemasks, and palatal expanders are all available through NHS specialist orthodontic services. However, NHS waiting lists can mean that referral at the optimal growth window is delayed; parents should ask their child's GDP to refer as early as age 8 to 9 if a jaw discrepancy is present, rather than waiting until the permanent dentition is fully erupted. Private orthodontic practices can typically offer faster assessment and treatment start, with no waiting list constraint, which can be critical when timing is important. The cost of functional appliance therapy typically ranges from £1,500 to £3,000 privately, depending on complexity.

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