This chapter reviews steps in the laboratory construction of basic appliances and discusses their indications and their mode of activation. For other appliances, whose fabrication is more complex, the finished appliance is presented.
This appliance, devised by Ricketts, consists of a palatal arch, shaped like a W, in which four helical loops are incorporated to increase its inherent flexible power.
For use in the primary dentition, we prefer to make the quadhelix with 0.032 blue Elgiloy wire; for the mixed and permanent dentitions, we use 0.036 wire. The quadhelix can be either removable or soldered. The construction of a removable quadhelix is shown in Fig 6-1.
For the soldered quadhelix, a clinical try-in stage is required. The orthodontist takes an alginate impression with the uncemented first molar bands in place in the mouth. The operator removes the bands and sets them carefully into the impression, which is then poured after a little sticky wax has been dropped inside the bands to secure them (Fig 6-2a). The technician constructs and adjusts the quadhelix and solders it to the bands on the working cast (Figs 6-2b to 6-2d).
There are two ways to activate the quadhelix before placing it in the mouth. Ricketts et al (1979) originally suggested that operators activate the appliance with a three-pronged pliers to incorporate expansion and molar-rotating force (Fig 6-3). The authors use another method proposed by Kholoki (1995). It employs an arch form chosen from a pentamorphic chart that serves as a pattern for regulating the quadhelix (Figs 6-4 to 6-7).
Construction of a Crozat quadhelix is shown in Fig 6-8.
Quadhelix with lingual spurs
Lingual spurs can be soldered to the quadhelix (Fig 6-9).
The alginate impression is poured with the tried-in molar bands set in place. This should be a good, deep impression that accurately reproduces the lingual area and the lingual frenum. The appliance is constructed in blue Elgiloy 0.036 wire in the same way as a soldered quad-helix without anterior loops.
The Crozat bihelix (Fig 6-10) is distinguished from a simple bihelix by the anterior springs soldered to the lateral arms that are used to move the mandibular incisors labially.
1. Distolingual rotation of maxillary molars so that they can occlude correctly with their mandibular counterparts
2. Recontouring of the mandibular alveolar shelf to provide increased arch length
3. Expansion of the anterior region to create space for labial movement of the incisors
4. Molar anchorage
5. Space maintenance