The Crozat appliance has been used in arch development for many years with great success.
8-10) One of the characteristics of the Crozat appliance is its effective clasp modification.
Standard Crozat with no auxilliaries and standard quad helix appliances were constructed by Ortek Orthodontic Laboratory (Duarte, CA) on a working model of the photoelastic maxillary model (Figure 1) The Crozat appliance was made with 0.
The Crozat appliance was adjusted for 2 mm of anterior and posterior expansion, while the quad helix appliance was adjusted in subsequent increments to provide 2, 4, 6 and 8 mm of anterior and posterior expansion.
These figures revealed the stress patterns produced with the Crozat appliance when activated for 2 mm of expansion were much higher and more concentrated than the stress patterns generated with 2 mm of expansion with the quad helix appliance.
Upon further evaluation of the occlusal figures, the stress patterns produced by the transpalatal activation of the Crozat appliance were uniformly distributed in the anterior and posterior palatal areas.
The Crozat appliance activated 2 mm resulted in a force of 530 gm, while the Quad Helix activated at 2 mm produced a force of 110 gm.
The objective of this study 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 biomechanical and physical characteristics of the Quad Helix appliance.
Most of the research performed with the Crozat appliance addresses case reports and clinical discussions.
By the 6 and 8 mm activation, much of the palate shows stress patterns, as well as the anterior region which is similar to the 2 mm activation of the Crozat appliance.