Removable Orthodontic Appliances: Hawley Plate and Functional Devices
Hawley Plate: Removable Appliance and Passive Function
The Hawley plate is a removable appliance with a passive function. Its key components include:
Parts and Retainers
Retainers: These are wire elements that hold the plate in the mouth. A 0.9 mm vestibular arch wire is placed in the anterior region, contacting the most prominent part of the vestibule. The wire ends are shaped into omega loops near the canines.
Resin: The resin occupies the palatal vault, providing stability to the appliance.
Expansion Plate: Active Device
The expansion plate is an active device similar to the Hawley plate, but it includes an expansion screw. This screw generates forces transmitted through the resin, facilitating transverse maxillary expansion in the upper jaw. It can also be used to correct asymmetric compressions by raising the bite on the opposite side of the crossbite.
Springs
Springs are elastic wire elements that exert force on teeth in a buccal, palatal, or lingual direction.
Facial Patterns
- Dolichofacial: Predominantly vertical parameters, giving the illusion of an elongated face and highlighting lateral compression.
- Brachyfacial: Horizontal parameters, creating a square face appearance. Individuals with strong buccinator muscles and well-developed jaw muscles often exhibit overbite and Class IIsub2 malocclusion.
- Mesofacial: Balanced vertical and horizontal parameters, making them susceptible to various malocclusions.
Space Maintainers
Space maintainers are fixed orthodontic appliances, such as bands or crowns, placed on teeth to maintain space after premature tooth loss. They serve a corrective function.
Substitution Plate
A partial resin prosthesis placed in the mouth when most teeth are lost prematurely. It restores masticatory function and esthetics.
Band-Handle
A steel band with a handle welded to it, contacting the mesial aspect of the adjacent tooth where the band is placed.
Crown-Handle
A steel crown cemented onto a primary molar, with a handle welded to it, saving space for a molar and/or primary canine.
Functional Devices: Modeling Function
Frankel Regulator
The Frankel regulator operates on the theory that external and internal forces influence the dental arches. External forces include lip and buccinator muscles, while internal forces are primarily from the tongue. An equilibrium of these forces maintains the arch form, while imbalances lead to changes. This device features resin shields in the lateral vestibular depth and anterior segment to eliminate external forces.
Bimler Appliance
The Bimler appliance features a thick omega-shaped wire arch extending from the mesial buccal aspect of a molar and turning forward. It also includes two simple springs, each acting on one or two teeth.
Nance Button
The Nance button is a fixed appliance consisting of bands on the first permanent molars. It can be used to derotate molars distally. It features a resin button providing anterior support, with wires extending to the first molars, forming loops, and attaching to the bands via soldering. Its function is anchorage and can be combined with other appliances.
Transpalatal Bar
The transpalatal bar consists of a wire positioned 3 mm away from the palatal mucosa, with an omega loop pointing posteriorly in the center. It can be slightly expanded.