The Hawley Appliance: Advantages, Disadvantages, Indications, Components, Fabrication, Adjustments
- It is a removable wire and acrylic palatal appliance.
- A Hawley appliance can be used both as a passive retainer (for retaining or stabilizing teeth in their new position following orthodontic treatment) and as an active appliance in order to achieve minor tooth movements.
- As the Hawley is a removable appliance, it can be removed for brushing, flossing and special social occasions.
- The palatal acrylic offers a significant anchorage.
- Like any other removable appliance, the success or failure depends entirely on patient compliance.
- Speech might be affected.
- Only tipping movements can be achieved.
- Rotated teeth are extremely difficult to correct.
- To hold teeth in a new position after orthodontic correction and to prevent relapse until bone fill around the moved teeth is achieved.
- To move teeth mesio-distally and buccally (minor, tipping movement)à can be used to correct simple anterior crossbites
Components of the Hawley Appliance
- Supports all the elements of the appliance
- Assures the retention of the appliance
- Fabricated with 0.7 mm wire engaging the mesio-buccal and disto-buccal undercuts of the posterior teeth
- Do not tend to separate teeth it is clasping
- Provides some anterior stabilization for the appliance
- Controls the position of incisors that are not meant to move
Finger-spring: only for active Hawley appliance
- Active component of the Hawley appliance
- Not included in Hawley appliance if used as a retention appliance (a passive appliance)
- Only tipping movement can be achieved by the spring
- The design must ensure adequate springiness and range while retaining acceptable strength
- Spring must be guided so that its action is exerted only in the appropriate direction
Fabrication of the Hawley Appliance:
- Alginate impression of the maxillary arch (impression of the mandibular arch may also be required if a Hawley appliance is being fabricated for retention purposes)
- Pour up alginate impression
- Lab Prescription- include:
- Student’s name
- Patient’s name
- Orthodontist’s signature
- Instructions to laboratory:
Insertion & Adjustments:
- The posterior of the appliance should be inserted first, then the anterior
- The appliance should be placed by pressing on the occlusal surfaces of the teeth
- To remove the appliance, a simple pull with a fingernail on the back clasps is sufficient.
- NEVER pull on the springs or the labial bow (front wire)à this will bend the wires and result in undesired tooth movements.
- If the appliance does not seat properly upon insertion, some acrylic surrounding the teeth may be removed. A straight handpiece with acrylic burs should be used.
Finger spring activation (when Hawley used as an active appliance)
- The fingerspring is activated 1.5 to 2 mm per month for a tooth movement of approximately 1 mm (within that time frame)
- Greater activation will slow the tooth movement due to excessive force being exerted on the tooth.
- Treatment is aimed at a slight over-correction of the crossbite until overbite is adequate is adequate to retain the corrected tooth position
- One or two months of retention with a passive appliance should follow the crossbite correction
Instructions to the Patient:
- Wear the appliance day and night (while sleeping)
- Remove the appliance while eating
- To avoid breakage, place the container in a protective container
- After each meal and before bedtime, clean teeth and the appliance with a toothbrush and toothpaste.
- Do not rinse the appliance under hot water
- Avoid chewing gum, candy or anything hard such as crusty bread or nuts
- Once the teeth are in the desired correct position, the appliance is only worn at night.
- If the appliance is broken or becomes uncomfortable, an appointment should be made to fabricate a replacement.
Recall Schedule and Adjustments
- Recall visits of 4 to 6 week intervals are indicated to assess the tooth movement and to perform the required adjustments.
- The following adjustments may be necessary: