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Expansion of the dental arch to avoid extractions
One of the principle methods used in orthodontics to avoid extractions is expansion of the upper and lower dental arches. Expansion is typically associated with palatal expansion in connection with cross-bites, but this type of expansion is not for correction of a cross-bite, but rather to increase room for alignment of permanent teeth.
The primary indication for expansion is generally lack of room for the permanent cuspids to erupt at age 12. Generalized crowding is another indication, but experience is the only teacher to make the decision to expand or not expand.
An indication to not attempt expansion is severe protrusion of both the upper and lower teeth beyond the normal bone positions. This is generally seen where the size of the teeth is abnormally large and the crowding severe.
The technique is relatively simple, but the trick is to know how much to expand to align the teeth. That knowledge comes from experience.
The typical methods we use are based on fixed appliances cemented to the upper first molars which provide controlled opening of the sutures of the face to increase the amount of bone available for alignment.
The lower arch is expanded to match the width of the upper arch after completion of expansion of the upper. This is accomplished by use of cross elastics stretched from the outside of the upper molars to the inside of the lower molars. The lower molars are then uprighted to match the width of the upper molars.
Another prime guideline is to be able use the 'E' space provided by the presence of the lower deciduous second molars. The 'E' space is the excess room left by loss of the deciduous second molars before eruption of the second permanent bicuspids. This is the reason to start treatment early rather than later. Once that 'E' space is gone, it's very difficult to regain.
