Brief outline of different activators

Monobloc activator

The monobloc activator is an appliance developed as an exercise device that embraces both jaws at once for correcting occlusal anomalies. It comprises an acrylic block for the maxilla and the mandible that is joined interocclusally (Fig 10-78).

In the maxilla, the greatly reduced acrylic base covers the palate in a horseshoe shape. The base is about 12 mm wide and flattens out. In the anterior region, the acrylic extends up to the incisal edges, and in the posterior region the occlusal surfaces are more than half covered.

In the mandible, the alveolar process is covered as far as the border of the floor of the mouth. Undercuts are blocked out. Anterior and posterior teeth are engaged as in the maxilla, with the occlusal surfaces two-thirds covered with an occlusal guard at least 3 mm thick.

The labial bow of the activator is used to retract the anterior teeth in the maxilla and is made of 0.9-mm spring hard wire. The transition of the labial bow into the acrylic block is kept free-moving to prevent fracture of the bow.

The monobloc activator can be used for widening the dental arches by means of a centrally positioned expansion screw. The sawn cut is placed sagittally in the middle.

Bimler appliance

This appliance (Bimler's "elastic occlusion former") differs considerably from a rigid form of activator. It is shaped from 0.9-mm strong steel wire. Only two thin acrylic plates lie palatally to the maxillary incisors, and a cap-shaped acrylic plate lies lingual to the mandibular anterior teeth (Fig 10-79). The palatal guide plates only fit closely to the maxillary incisors and anchor all the wire brackets. A Coffin spring links the two guide plates; the labial bow with a small buccinator loop is passed between the canines and first premolars. Lastly, a wire bracket as a replacement for a mandibular plate extends to the mandibular incisors, which it contacts below their equators. This wire then runs back down between the canines and first premolars over the dentition labially into the acrylic caps. Two wire brackets extend from the cap lingually behind the anterior teeth. The wire loops are guided differently depending on the aim of the treatment.

The stimulating body of this elastic occlusion-shaping appliance induces involuntary muscle reactions. Transverse mandibular movements are exploited for widening the dental arch, while vertical movements help to stretch the arch. The appliance is worn day and night for a quick outcome because it does not interfere with speech. It has to be adjusted in line with treatment progress, which is very difficult given the complicated wire bracket guidance.

Klammt's elastic open activator

The open activator is a maxillomandibular appliance comprising two lingual, lateral acrylic bodies that are joined by a transverse expansion screw or by a palatal bar (Fig 10-80).

The standard appliance comprises the lateral acrylic bodies, a palatal bar or a transverse screw, labial bows paired for the maxilla and the mandible (with possible lip bumpers), and intraoral guide wires.

The acrylic bodies extend from the canine to the last posterior tooth; guide planes can be worked in, while the occlusal surfaces remain clear. The palatal bar made of 1.2-mm hard steel wire joins the two acrylic bodies. The palatal bar must not contact the mucosa or impede the tongue.

The labial bows made of 0.9-mm hard steel wire are passed between the canines and first premolars in a vestibular direction; they are formed into loops distally over the premolars and run over the anterior teeth.This means the labial bows take on the following functions:

• Shaping the dental arch from the incisors through to the premolars
• Controlling lip tone to shape the ideal dental arch
• Shielding the posterior teeth from the cheeks
• Vestibular guidance of the erupting canines and premolars

The intraoral guide wires made from 0.9-mm hard steel wire lie against the lingual surfaces of the incisors in pairs. The lip bumpers can replace the labial bows in the maxilla or mandible and lie deep in the vestibular fornix.