Page 47 - REMOVABLE ORTHODONTIC APPLIANCES

Chapter 6

Anchorage

'Anchorage' is the term used to describe the for example, may hold the appliance in place
resistance to those reactionary forces generated (retention) while, at the same time, resisting
by the active components of the appliance. The forces of reaction to the retraction of the upper
orthodontic movement of one or more teeth is canines (anchorage). The two concepts must be
achieved by the apphcation of a force. The considered separately during appliance design
reaction to this force will tend to produce and adjustment as well as in the monitoring of
movement of other teeth in the opposite direc- treatment progress. Clasps sufficient for appli-
tion. Anchorage control is concerned with ance retention may provide inadequate anchor-
maximizing the desired tooth movements while age, while an appliance with excellent
minimizing unwanted tooth movements. It is anchorage - for example to correct an incisor in
important to distinguish anchorage from reten- crossbite - may be deficient in retention.
tion (the resistance of the appliance to dis- Anchorage may be provided either intraorally
placement) even though some appliance or extraorally, but the majority of cases treated
components fulfil both requirements (Figure with removable appliances employ intraoral
6.1). Clasps on upper first permanent molars, anchorage.

Figure 6.1 The Adams' clasps on the upper
first molars and the double Adams' clasp on
the central incisors provide retention and also
anchorage to resist forces of retraction on the
upper canines. This is an example of
intramaxillary anchorage.