ORTHO TRIBUNE | NOv./DEC. 2009 Industry Clinical 9 The TRAINER System in the context of treating malocclusions By German Ramirez-Yañez, DDS, MDSc, PhD Part three A nother effect reported with the TRAINER System™ Appliances is transverse development of the dental arches. All the Frankellike appliances, which have a buccal shield in their structure, move the cheeks away from the buccal aspect of the upper and lower posterior teeth. This action produces two effects on the craniomandibular system (CMS). First, the presence of the buccal shields releases a force produced by the buccinators (muscles of the cheeks) on the buccal aspect of the posterior teeth, which normally is of about 2.7 g/cm2, but can increase up to 20 g/cm2 in patients with a digital sucking habit or tongue thrust. In the same way, these buccal shields in the appliance release excessive force (up to 80 g/cm2) that can be produced at the corner of the mouth on the cuspid teeth, which can be present in those patients with the same habits. Such a force tends to reduce the inter-canine distance, badly affecting the shape of the dental arches and crowding the dentition (Lindner and Hellsing 1991; Mew 2004). Second, the presence of the buccal shields in the appliance stretches the buccinators and orbicularis oris (muscles of the lips), creating a tension zone at the area of insertion of those muscles. As it has been extensively explained in the literature (most orthodontics and cranio-facial growth books), on the tension zone there is bone apposition (Frost 2004). Therefore, by creating a tension zone by stretching the muscles (buccinators and orbicularis) through the buccal shield in the appliance, there is an increase in bone apposition at the maxilla and mandible. The presence of the buccal shield at the anterior area of the mouth encourages the patient to produce a better lip seal, which will be explained later. Be aware that this effect is higher in the MYOBRACE®. As explained in part two, one of the assets of the MYOBRACE is the inner-core embedded in the buccal shields. This inner-core provides more resistance to the appliance and counteracts the force released by the buccinators and orbicularis muscles when they are hyperactive. The first effect referred to above permits that the force produced by the tongue on the lingual aspect of the posterior teeth (about 1 g/ cm2) stimulates the development of the dento-alveolar units of those teeth toward buccal. Due to this, there is no force counteracting in an opposite way as it has been neutralized by the presence of the buccal shields. In this way, transverse development is stimulated. The other effect regarding creating a tension zone at the insertion area stimulates bone apposition at the borders of the mandible and maxilla, thus stimulating further development of the jaws with bone formation that will give more space for tooth alignment. g OT page 11 Fig. 4: Patient, age 7. In this case, there is also a mandibular advance and an improvement in the inclination of the upper incisors. Furthermore, a significant improvement in lip seal (right side) can be observed in this patient after treatment during 14 months with a TRAINER Appliance (T4K). AD