Abstract
Aim and background
The quad helix is well known for its ability to treat posterior crossbites in children with maxillary deficiency. A few authors have also used it for the treatment of unilateral crossbite due to unilateral maxillary deficiency by incorporating modifications in the appliance. The aim was to treat a unilateral crossbite using a newly modified quad helix.
Case description
An 8-year-old female patient had presented with multiple missing teeth and a unilateral posterior crossbite due to an asymmetric maxillary arch. The amount of unilateral asymmetry was measured using a unique method over the cast. A modified quad helix was cemented to treat the unilateral posterior crossbite, and correction was obtained in 30 days. A Nance palatal arch was cemented which functioned as a space maintainer and a retention appliance.
Conclusion
The posterior unilateral crossbite was treated successfully with the modified quad helix.
Clinical significance
This article highlights a new modification of the quad helix for treating unilateral posterior crossbite and a new method of measuring maxillary asymmetry. The modification has been termed as a “bi helix” since it eliminates two helices from the classic quad helix design.
How to cite this article
D’souza OK, Chalakkal P, de Noronha de Ataide I. A Modification of the Quad Helix: The “Bi Helix”. Int J Clin Pediatr Dent 2024;17(7):822–825.
Keywords: Bi helix, Case report, Modification, Modified, Quad helix, Unilateral crossbite
Introduction
The quad helix (QH), introduced by Ricketts in 1975 for slow maxillary expansion, is a modification of the Coffin’s W-spring and may be used during the mixed dentition period for treating posterior crossbite.1,2 It is also recommended for treating unilateral posterior crossbites (UPC). In two previous articles, the authors had modified the classic design of the QH in order to direct forces toward teeth on the side of the maxillary deficiency, while using the contralateral side for anchorage.3,4 However, this case report highlights the use of a modified QH design that has not been reported before for the treatment of UPC.
Case Description
An 8-year-old female patient reported to the Department of Pediatric and Preventive Dentistry for comprehensive dental treatment. Intraoral examination revealed multiple missing maxillary teeth and root stumps, bilateral class I molar relationship, normal overjet and overbite, with no evidence of skeletal disharmony. Stainless steel crowns were placed on 65 and 75 following endodontic treatment, and a band and loop space maintainer was placed on 46, following extraction of 85 (Figs 1A and B).
Figs 1A to D:
(A) Pretreatment occlusal view of the maxillary arch; (B) Pretreatment occlusal view of the lower arch; (C) Pretreatment left lateral view; (D) Pretreatment right lateral view
A unilateral single-tooth crossbite was present involving 26 and 36, with normal occlusion in the first quadrant (Figs 1C and D). This finding was confirmed by carrying out the following cast analysis: A glass plate was positioned on the maxillary cast (occlusal surface facing upward) for drawing lines. A line (black line) was drawn on the glass plate along the midpalatal raphe. Perpendicular lines were drawn from the black line on either side till the tips of the mesiopalatal cusps of 16 (red line) and 26 (blue line). The length of the red line was found to be 24.59 mm, while that of the blue line was found to be 22.79 mm (Fig. 2). These measurements confirmed a unilateral maxillary deficiency in the second quadrant. The distance between the red and blue lines was found to be 4 mm indicating, that 16 was situated ahead of 26.
Fig. 2:
Cast analysis
In this case, the upper appliance design had to be one that would correct the unilateral single-tooth crossbite (26 and 36) while simultaneously maintaining space on the opposite side by preventing the mesial migration of 16. Therefore, a modified QH (“bi helix”) was designed. Orthodontic bands were adapted on the upper molar, and an alginate impression was made. The bands were placed in the impression and poured with dental stone. The wire component was designed using a 0.038″ round stainless steel wire. It comprised two helices on the side of the crossbite. The anterior helix at the level of the primary canine upon activation corrected the crossbite by providing a buccally directed force on 26, while the posterior helix derotated 26. The helices on the opposite side of the arch were eliminated as no arch expansion was needed. An acrylic plate was fabricated on the palatal mucosa of the opposite side. The ends of the wire were then soldered to the molar bands on either side. The appliance was then finished and polished (Fig. 3A).
Figs 3A and B:
(A) The completed “bi helix” appliance; (B) The “bi helix” after cementation
Prior to cementation, the appliance was preactivated by opening the anterior helix by 5.0 mm such that the molar band was halfway past the buccal surface of 26. The appliance was then cemented onto the molars (Fig. 3B). Bite opening was carried out by placing glass ionomer cement on the occlusal surfaces of mandibular posterior teeth, bilaterally. Necessary instructions were given to the patient. Recall appointments were scheduled after 24 hours and after 30 days. After the completion of 30 days, correction of the crossbite was observed, while the opposite side was unaffected (Figs 4A and B). The appliance was discontinued, and posttreatment retention was achieved with a Nance palatal arch, which also functioned as a space maintainer (Fig. 5).
Figs 4A and B:
(A) Posttreatment left lateral view; (B) Posttreatment right lateral view
Fig. 5:
Nance palatal arch after cementation
Discussion
Unilateral posterior crossbites are classified as either functional or true. In this case, it was diagnosed as a true UPC since the mandibular path of closure was observed to be normal in both centric relation and centric occlusion without any functional shift or midline deviation.5
The use of a QH was preferred over a removable appliance incorporating jackscrews, since a fixed appliance would have better compliance with a child patient. A removable appliance leaves the clinician at the mercy of the patient’s cooperation.6 Moreover, the risk ratio of a QH when compared with a removable expansion plate has been found to be 1.29.7,8 Elastics were not used either, since the maxillary insufficiency needed expansion rather than UPC correction alone.
The present modification utilized only two helical loops (one each anteriorly and posteriorly) on the side where expansion was desired due to maxillary deficiency. On the opposite side, an acrylic plate was incorporated, covering the palatal slope of the edentulous ridge in order to derive anchorage and minimize unwanted arch expansion on the unaffected side. The modified QH by Chebolu et al. contained acrylic that covered the hard palate extending till the gingival margins,3 while O’Malley et al. used an acrylic button on the opposite sides of the quadrants that needed UPC correction.4 The arms of the QH exert a fan-like sweeping action. However, an armless QH design was used in this case because there were no teeth present on the side of expansion for the arms to engage. If teeth were present and were in crossbite, the outer arm could be incorporated.
The desired expansion and correction of UPC was achieved with a single activation before cementation of the bands, similar to that carried out in two previous case reports.9,10 The anterior location of 16 by 4 mm when compared with 26 could have been the result of asymmetrical arches rather than the result of mesial drift since there was a class I molar relationship present bilaterally.
Conclusion
The bi helix may be used for the correction of unilateral permanent molar crossbites with missing primary teeth.
Clinical Significance
This article highlights a new modification of the QH for treating UPC and a new method of measuring maxillary asymmetry. The modification has been termed as a “bi helix” since it eliminates two helices from the classic QH design.
Orcid
Olando K D’souza https://orcid.org/0009-0002-4420-696X
Paul Chalakkal https://orcid.org/0000-0002-6631-2280
Ida de Noronha de Ataide https://orcid.org/0000-0002-6174-0542
Footnotes
Source of support: Nil
Conflict of interest: None
Patient consent statement: The author(s) have obtained written informed consent from the patient’s parents/legal guardians for publication of the case report details and related images.
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