Expansion

Palatal expansion is used in cases of a narrow palate to help align the teeth and jaws. Expansion screws can be placed in removable, fixed and functional appliances and work to widen the roof of the mouth.

 

 

Arch expansion was first explained by the dentist Emerson C. Angell in 1860. He placed a jackscrew type of expansion device across the palate between two upper premolars and achieved expansion by 1/4 inch in 14 days. His work was not accepted at the time but later became part of orthodontic treatment.

In 1877 Walter Coffin developed a spring for arch expansion which worked by separating the mid-palatal suture. The first expansion screw consisted of a vulcanite base plate with a spring of piano wire bent in the shape of the letter W. The spring was activated by cutting the vulcanite down the middle of the palate and stretching the two halves of the appliance apart. Lower appliances used the same principles but with the wire bent in a U shape.

The pioneering orthodontist Edward H. Angle introduced a jackscrew in 1899 which was designed to push apart the sides of the arch. In early 1900 Angle developed his E-arch appliance, which had molar bands on either side of a heavy arch wire. The ends of the arch wire were threaded onto the molar band and could gradually be extended to increase the size of the arch.

Badcock presented his expansion screw to the BSSO in 1911. Bennett advocated the use of this screw made from nickel silver in removable appliances and in 1913 Mellersh introduced a modified version of the Badcock screw.

In 1956 the American orthodontist Dr Andrew Haas introduced his expansion device.

The Haas Expander consists of bands fitted to the first premolars and molars on each side of the mouth attached with support wires to an acrylic plate into which an expansion screw is fitted. The acrylic plate is cut along the middle allowing it to move apart as the screw is turned.