## 2 Materials and Methods
### AMCOP(r) Bio-Activators Description  
In this study, AMCOP bio-activators were adopted.  
The acronym AMCOP(r) (Armonizzatori Multifunzionali Cranio-Occluso Posturali) stands for:  
* HARMONIZER: harmonically reshapes the dental-cranial-facial structures;
* MULTIFUNCTIONAL: suitable for the treatment of various dysfunctional problems;
* CRANIAL-OCCLUSION-POSTRURAL: acts on the relationship between the skull and jawbones, and between occlusion and posture, by acting on the first cervical vertebrae.  
The AMCOP(r) devices are made of an elastic and a thermoactivable material derived from a polymer-elastomer combination. This is soft, comfortable, and adaptable to different kinds of arches. During treatment, it is possible to expand the device by immersing it in hot water at 70\({}^{\circ}\) for 30 sec and to make retouching or shortenings using rubber, brush, and heat-appropriate instruments. The size of the activator is chosen by measuring the transverse distance between the outermost point of the vestibular cusps of the first two upper molars. The measurement can be made on the plaster model or on a wax bite. This second option is advantageous for young children as it avoids impression-taking, which children often do not appreciate. All the AMCOP(r) devices are equipped with two high flanges, one on the vestibular side and one on the lingual side, eliminating any muscular interference on the teeth. A central area links the flanges without indentures where the teeth can move. A lingual ramp and a button help to guide the tongue on the palate. The activators are available in different colors, referred to arch shapes and skeletal classes.  
In this research three specific devices were used:  
AMCOP Integral:  
It is indicated for treating first-class malocclusions with basal skeletal disharmonies responsible for horizontal (e.g., transverse insufficiencies) or vertical (e.g., open or deep bites) deficits. It is used in all kinds of dentition (deciduous, mixed and permanent) and ideal for early and interceptive treatments. Furthermore, it is adopted for its orthopedic action, for therapy in the presence of occlusal curve alterations (anterior and/or lateral open bite) and for a proper balance of the dental arches. The occlusal plane functions as a stabilizer of the mouth balance. The flat occlusal planes are made with appropriate functional Spee and Wilson curves for correct mandibular growth. First class bio-activators (Figure 1) are subdivided into four types of arch form in relation to the kind of cranial conformation of the patient (brachycephalic, dolichocephalic, and mesocephalic).  
AMCOP Second Class (SC):  
It is indicated for the treatment of mandibular retrognathia by repositioning it in a first-class ratio and using deciduous, mixed and permanent dentitions. It has a mandibular anterior sliding plane that promotes the advancement of the mandible (in retrusion) by positioning the incisors head-to-head, providing a lengthening of the mandibular bone base, the retro inclinations of the lower incisors and the pronunciation of the upper ones (overjet). It is also used to treat TMJ dysfunction and improve lip competence and, therefore, facial aesthetics (Figure 1).  
AMCOP Open:  
It is indicated for the anterior skeletal open-bite treatment due to atypical swallowing habits and a specific skeletal craniomalibular imbalance (Figure 1). The specific orthodontic-orthopedic action provided by the device takes place through the unblocking of specific craniofacial skeletal structures in antero-flexion movement with the restoration, in equilibrium, of the occlusal plane and resolution of the anterior open bite.