Academic journal article American Academy of Gnathologic Orthopedics Journal

Force Activation and Biomechanical Effects of the Crozat and Quad Helix Appliances in the Maxillary Mixed Dentition

Academic journal article American Academy of Gnathologic Orthopedics Journal

Force Activation and Biomechanical Effects of the Crozat and Quad Helix Appliances in the Maxillary Mixed Dentition

Article excerpt

ABSTRACT

Arch length discrepancy problems have been a longstanding clinical dilemma facing most dentists who treat children. The Crozat appliance has been used in arch development for many years with great success. The quad helix is another appliance that has been utilized with great success in early expansion therapy. The objective of this investigation was to analyze the biomechanical and physical effects of the Crozat appliance when activated for transverse palatal expansion, and to compare these effects with the quad helix appliance. This study used a three-dimensional maxillary photoelastic model in the mixed dentition. Standard Crozat and quad helix appliances were constructed on a working model of the photoelastic maxillary model. The Crozat and quad helix appliances were used to achieve transpalatal expansion in the anterior and posterior quadrants. The stresses transmitted to the supporting structures with each appliance were recorded photographically in the field of a circular polariscope. In addition, each appliance was mounted on a split-stone maxillary cast and the force-activation levels were measured. Transverse palatal expansion was achieved with both appliances at varying adjustments. The stresses generated were localized along the palate, both anteriorly and posteriorly. The forces generated with each appliance suggested more activation of the quad helix appliance was needed to produce a force and resultant effect comparable to that of the Crozat appliance.

INTRODUCTION

Arch length discrepancy problems have been a longstanding clinical dilemma facing most dentists who treat children. A concerned parent will present their child with complaints of "crowded teeth" or "crooked teeth," resulting from arch length deficiency in the corresponding arch. These concerns become evident when the permanent incisors are beginning to erupt into the mouth and demonstrate a lack of adequate space and narrow arch width. McInaney et al. in 1980 stated numerous cases, having been diagnosed with space discrepancy problems in the deciduous and mixed dentitions, have shown great benefits from treatment by early expansion therapy. (1)

The Crozat appliance was introduced by Dr. George B. Crozat in the early 1900's. (2,3) It is a removable appliance made of stainless steel metal that has the mechanical potential to derotate and distalize molars, upright lingually inclined teeth, and expand the arch transversely when properly activated. The philosophy underlying the use of the Crozat appliance is guidance of arch development. (4) This appliance has been used in arch development for many years with great success. (5) The Crozat appliance has been reported to have great versatility and adaptability. (4)

The quad helix appliance is another treatment modality that is widely used in early expansion therapy. It evolved from the fixed "W" arch, with a total of four helical loops incorporated at the anterior and posterior segments of the palate, thus the name "quad helix". (6,7) The helical loops increase the flexibility and the range of force of the appliance by adding 25 mm of wire to the appliance per loop. (6,7) The appliance is constructed of stainless steel wire that is soldered to bands cemented to either the maxillary first permanent molars or the deciduous second molars. It has been successfully utilized in the expansion of the buccal segments and derotation of the banded molars by activating and/or expanding the anterior and palatal arms of the appliance prior to cementation. (7) Research has shown that the quad helix can produce clinical orthopedic effects to the maxilla in children during the mixed dentition, but only dental expansion in adults. (7) With this in mind, the quad helix can be a useful tool in early expansion therapy for a select pediatric patient population.

Many clinicians would prefer to use fixed appliances, such as the quad helix, for transpalatal expansion due to their more predictable results. …

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