Bite opening at the start of treatment is very important in the Begg technique. The premolars are usually not banded. This was expressed by Cadman.1 For extraction cases, he wrote,". . . many operators delay banding the premolars until the extraction spaces are almost closed to avoid interference of the premolar brackets with the archwire." For nonextraction cases he remarked, "as in extraction treatment, interference of premolar brackets with the archwires impedes the bite-opening action of the appliance which, in turn, prolongs the use of Class II elastic traction with consequent loss of anchorage." To prevent possible lingual or buccal crowding of the premolars, he recommended the use of molar loop stops. He added, however, that the loop stops constitute an increase in total length of the archwire with decreasing intruding effect on the anterior teeth, and also that they may contribute to a loss of molar control because of the increased flexibility of the unsupported archwire.2
Sims3 disagreed with the use of loop stops. He wrote, "A classical example of mistaken therapy with this appliance has been the use of an omega loop as a substitute for the simple anchorage bend just mesial to the buccal tube. Unfortunately, as many operators have found to their dismay, prolonged use of this loop variation results in efficient but unexpected rotation and lingual displacement of the anchor teeth. This loop modification significantly reduces anchorage potential."
The same disapproval was expressed by Dr. Begg when I attended his Begg Course at Adelaide in 1969.
If the use of molar stops is out and the placement of premolar bands creates difficulty, how do we solve this problem? How can we have the freedom of movement of the archwire without interfering with its biteopening action and yet have control of the arch length? The answer is in the use of a sliding yoke.
The Sliding Yoke
A sliding yoke has been used in edgewise technique for many years. Its application to the Begg technique is new. The yoke can be made by forming a small circle at right angles to both ends of a measured length of .016'' wire. The yoke serves the purpose of maintaining space for the premolars while, at the same time, allowing freedom of movement of the main archwire. If you are using an .016'' slot bracket, you may have to open the bracket somewhat for engagement.
The use of the sliding yoke can be extended to extraction cases, especially in cases of mandibular anterior crowding, deep overbite, and strong mentalis activity. Some colleagues are apprehensive about prescribing premolar extractions at the start of treatment, fearing that the mentalis may tip the lower incisors excessively lingually. They would rather postpone extractions, treat the case
nonextraction at the start, and "blow" the incisors forward to effect bite opening. But Dr. Begg says4 that when anterior teeth are depressed in their sockets during the first stage of treatment in Begg technique, the apices of the roots actually move posteriorly in addition to being depressed. Therefore, it would appear more logical to provide room for such movement by extraction right at the start.
Fig AThe sliding yoke in position.
The yoke can be placed about 2-4mm short of the canine brackets, depending on the amount of crowding. Bite opening and unraveling can be allowed to occur simultaneously, and the possibility of excessive lingual tipping of lower incisors can be controlled when the canine brackets come into contact with the yoke. It is a simple device, but it works.
