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Molar Class II; Cuspids Class II Or Non-erupted
Aug 13, 2018

Apical base class I (wits=-2mm to +3mm)

These type cases usually present with molar class II as a result of the maxillary molars being positioned interior. The canines can be non-erupted or crowded out to the labial or, if the four incisors are flared, there can be sufficient arch length for the canines to be fully erupted but class II. The teeth in the mandibular arch are usually in rather good alignment. The key to successful treatment is the distal movement of the maxillary posterior teeth, thereby making enough arch space for the proper alignment of the maxillary anterior teeth and establishing a class I occlusion. Great care should be taken not to move the mandibular teeth anteriorly.

Anchorage preparation in the mandibular arch

The arch should be leveled with all teeth up-righted and all rotations corrected. A. 18*25 arch wire should be placed in the pre-adjusted edgewise slots in the mandibular arch. The mandibular arch will be come the anchorage arch. Once the above is accomplished , up to 4oz. Of class II elastic force can be utilized bilaterally, in association with asliding yoke on the maxillary arch wire. To move the maxillary posterior teeth distally without forward movement of the mandibular teeth.

Procedures for the maxillary arch

Brackets are placed only on the four incisors with buccal tubes only on the first molars. If the cuspids are fully erupted brackets should also be placed on them. While preparing the mandibular arch as the anchorage arch, align the maxillary arch so that a 0.018 stainless steel arch wire can be inserted into the interactive slot of the brackets and into the occlusion component of the buccal tubes. The 0.018 archwire is inserted through the eyelets of the sliding yokes and the the assembly is placed in the maxillary arch. (see illustrations 7 and 8) the archwire is allowed to project out from the distal surface of the buccal tubes as much as possible without causing irritation once turned in toward the molar. Depending on the amount of distal movement of the molars it may be necessary to replace the 0.048 arhcwire to allow for more distal movement of the molars. If the canines are erupted but crowded out to the labial adjust the 0.018 archwire is shaped to all for more distal movement of the molars. If the canines are erupted but crowded out to the labial adjust the 0.018 arch wire is shaped to allow for the maligned canines. The distal movement of the molars will not be bodily. Some degree of tipping occurs. Over-correction of molar class I is necessary to allow for slight mesial movement of the crowns of the molars later in treatment. Approximately 4 oz of bilateral elastic force is attached from the elastic hook on the buccal tube to the hook on the sliding yoke to distalize the molars. Once the molars have been distalized to an over-corrected class I. the brackets are placed on the bicuspids and canines, if erupted, and begin the finishing alignment of the maxillary arch. Care should be taken to insure that the maxillary molars are not tipped but up-tight and in a good class I relationship.

Cases with flared anterior teeth usually presents with considerable horizontal overbite. Not only do the molars and bicuspids have to be move distally, the anterior teeth have to be move distally as well. The sliding yokes, along with the 0.018 steel arch wire, are used in the same manner as discussed previously to distalize the maxillary molars. As the molar move distally the transseptal fibers tend to move the bicuspids distally as well. Do not try to move the anterior teeth distally at the same time as moving the molars. Once the molars are in an over-corrected class I , reduce the bi-lateral elastic force on the sliding yokes to two ounces of force and place an equal amount of force on the anterior teeth. This can be accomplished by holding the anterior teeth together with a wide power chain and hooking the elastic to the canine “T” hooks. Once the canines are in class I and the horizontal overbite is corrected, place the brackets on the bicuspids and proceed with finishing the case.

Fabrication of sliding yoke

The sliding yoke is fabricated from 0.022 stainless steel wire. An eyelet is formed at on of the wire. The eyelet is then bent at a 90 degree angle from the long axis of the wire. A second eyelet is formed a measured distance from the first eyelet. The distance from the mesial end of the first molar buccal tube to the canine region and the distance between the two eyelets should be the same. The second eyelet is then bent 90 degrees from the long axis of the wire to the same side as the first eyelet. After the second eyelet is fabricated, continue bending the wire to form a hook in the shape of a fish hook. The shaft of the hook should be as long as possible without causing occlusal interference and the end of the hook should be bent is such a fashion as to accept an elastic without causing tissue irritation. The hook is positioned to the facial side of the sliding yoke. Therefore, there are left and right sliding yokes. The fabrication of the sliding yoke is such that the elastic hook is positioned near the occlusal plane not gingical to the canine bracket. This design will greatly reduce the vertical component of force of the class II elastic and thereby reduce the extrusion force on both the mandibular molars and the maxillary anterior teeth.