What are the differences between a twin block appliance and a bionator?

BackgroundBoth these are removable orthodontic appliances, designed to influence jaw and tooth position during growth. The appliances are designed to treat primarily two problems

1: A jaw relationship where the lower jaw (mandible) has a retrusive position (behind) to the upper jaw (maxilla)

2: Correction of the Deep Bite where there is a to larger gap between the upper and lower front teeth and the lower front teeth tend to bite too deeply into the palatal area.

Both these appliances have variations that treat other problems for example the Prognath jaw relationship where the lower jaw is too large compared to the upper jaw and the lower front teeth tend to bite in front of the upper front teeth.

The Bionator was invented by the German Prof. Dr. Dr. Balters in the 1950s

The Twin Block was invented by the Scotsman Dr. Clark in the 1970s

Your answer

The differences between the two appliances are

The Bionator is a single appliance fitting between the upper and lower teeth moving the mandible forwards into a "normal" upper and lower relationship, encouraging different growth in the upper and lower and also encouraging the teeth to drift in the direction of normal occlusion.

The deep bite is treated through letting the side teeth develop and erupt thus opening the bite. The Bionator uses only the body's internal muscle forces to do its work, and does not exert a force of its own, it is generally accepted that the Bionator can not correct individual tooth position, for example a rotated front tooth.

The Twin Block is an appliance in two halves; one for the upper jaw and one for the lower jaw, each half have an inclined plane, possibly also an expansion screw for widening the jaws and springs or mini screws for adjusting the individual position of teeth.

The Twin Block works by having an inclined plane in the upper and one in the lower, when the patient bites together the upper plane pushes the lower plane and so the lower jaw forwards. The Twin Block exerts force and can correct the bite, correct the deep bite, expand the tooth arch and correct individual tooth position.

Your take home message

Both these appliances only work when worn