ORTHO TRIBUNE | NOv./DEC. 2009 f OT page 9 Industry Clinical 11 Fig. 5: Cephalic lateral X-rays of a 5-year-old patient. The left X-ray shows the patient before treatment, the X-ray in the middle shows the patient at the end of treatment, and the X-ray on the right shows the patient one year after treatment with the mandible correctly positioned and with an ideal overbite and overjet for his age. This patient used the TRAINER Appliances for 15 months, starting with the T4I and then switching to the T4K when the first permanent molars erupted. An additional effect to stimulate transverse development of the dental arches with the Trainers is changing the posture of the tongue. When relaxed, the tongue stays in a physiological position (Fig. 4), which is encouraged by the lingual tab located on the upper-lingual side of all the appliances of the TRAINER System, including the MYOBRACE. It has been scientifically proven that the TRAINER System Appliances stimulate transverse development of the dental arches. A paper published in the Journal of Clinical Pediatric Dentistry (Ramirez-Yañez et al. 2007) shows the results of a study of the effect of the T4K on the dimensions of the dental arches of 60 children with Class II, Div 1. These results show that there is a significant increase in the intercanine, inter-premolar and intermolar distances when treatment was performed with the TRAINER Appliance. This effect is produced by posturing the tongue in a more physiological position and by the buccal shields in the appliance releasing the force produced by the muscles of the cheeks and lips. In other words, the effect with the TRAINER is similar to that reported in patients treated with the function regulator appliance (Frankel R. 1977). II fibers in the masseter muscle (Rowlerson et al. 2005), which has been associated with an increase in the average of bite force (Ringqvist 1973). The presence of the TRAINER in the mouth does not permit tooth contact because of the silicon surface between the upper and lower components of the appliance, which avoids contact between the teeth. As there is no contact between the teeth and maximum intercuspation is not reached, the increase in muscular activity when closing the mouth does not occur, reducing the loading at the teeth and their dentoalveolar units at maximum inter- cuspation. As the loading at maximum intercuspation is reduced, the dento-alveolar units can develop and teeth can come to that plane given by the occlusal surfaces of the appliance. Thus, an occlusal plane (Spee curve), which is generally g OT page 12 AD vertical growth and development Clinically, the TRAINER System Appliances produce an improvement in the vertical relationship between the upper and lower teeth (overbite) in patients that have either a deep or an open bite. This has been scientifically demonstrated in two studies (Usumez et al. 2004; Ramirez-Yañez et al. 2007) — one where it was reported that patients with deep bite have a significant increase in the vertical dimension (Fig. 5) and another where patients with open bite have a significant reduction in the negative overbite (Fig. 6). To explain the effect of the TRAINER System Appliances on the vertical development, it is necessary to use concepts from the physiology of the CMS. Furthermore, it is necessary to explain separately how the Trainers work to correct each of these problems, as the same appliance works in a different way when there is a deep bite or an open bite. Deep bite When the mouth is closed, the masticatory muscles, particularly the masseters (deep masseter) and temporalis (posterior fibers), increase their activity when the first teeth contact occurs. This is a physiological response that permits a higher force to move the teeth closer and smash any piece of food that may be between them. Patients with a deep bite have stronger muscles closing the mouth (Farella et al. 2003), and some reports have shown that deep-bite patients have more type