How Should the Retentive Components Be Positioned?

Two key points:

The overall layout of the distribution, e.g. what shape the distribution should form, such as a rectangle or triangle.
Whether there is space and where the space is to move the teeth we want to move. For example, consider the situation where a lateral incisor is to be pushed over the bite. If there is only just enough space for the tooth to move between U1 and U3 or UC, then a clasp must not be put on either of the teeth adjacent to U2. This is because the fly-overs (the wire from the clasps that passes between the contact points) will encroach on the space needed for U2 to move forward and this will prevent U2 from moving.

Overall Layout of Retention Distribution

Remember: the golden rule is that there must always (there are no exceptions) be anterior and posterior retention. Placement of the anterior retention on the upper central incisors is often ideal as it maximally reduces the chance of the appliance rocking.

This means that retention can be placed so the clasps take up roughly any of the following shapes:

Rectangular
Square
Triangular configuration. In this case the base of the triangle should always be between UR6 and UL6 or, in unusual circumstances, between an U6 on one side and an U7 on the other.
For example, depending on the circumstances, Adams’ clasps (or other types of retentive clasp) could be placed on both U6s and both U4s or UDs (rectangular configuration); both U6s and both U3s or UCs (a squarer configuration); or both U6s and UR12 (a variety of the triangular configuration). Other possibilities are essentially variations on this theme. Examples of possible retention layouts are shown diagrammatically  and as they could appear on a laboratory card.

A: Anchorage

Now the second ‘A’, which stands for anchorage. This has been discussed above and you should revise this section. Remember that Newton’s Third Law of Motion states that ‘To every action there is an equal and opposite reaction’ and that anchorage can be defined as the resistance to unwanted tooth movement. Anchorage should be planned as part of the overall treatment plan. A more detailed description of anchorage is beyond the scope of this book, although some brief details are given for the specific URA designs