INFLUENCE OF DENTAL MALOCCLUSIONS AND THEIR ORTHOGNATHODONTIC TREATMENT ON MASTICATION AND POSTURE

This Ph.D. thesis presented and critically discussed scientific papers published (or, in one instance, submitted and currently under peer review) during the course of the four years of the program. These papers were grouped together because a thread runs through them all: the functional approach to clinical orthodontics. Malocclusions negatively affect the functions of the stomatognathic system, and an in-depth understanding of their functional consequences is necessary if long-term stability of their correction is desired. At the same time, treatment strategies that disregard correcting the functional alterations alongside the dental features of malocclusions are inevitably set for failure down the line. Furthermore, it is now clear from multiple studies that the masticatory function has implications that go well beyond the traditional goals of Dentistry and Orthodontics. Indeed, animal studies have demonstrated that masticatory alterations have direct adverse effects on hippocampal neuronal populations, reducing memory and spatial orientation. More recently, large-scale clinical studies have shown that a loss of masticatory efficiency earlier in life was significantly associated with an increased risk of cognitive decline later in life. In this context, a functional approach to clinical Dentistry and Orthodontics is of great importance. The objectives of this Ph.D. research were 1) to evaluate the characteristics of the masticatory function and the effects of functional treatment in patients with different malocclusions; 2) to evaluate the effects of functional treatment of unilateral posterior crossbite on the growth of the jaws; and 3) to evaluate the association between the masticatory function and posture. The research papers presented in this Ph.D. thesis reached the following conclusions: 1) The percentage of reverse chewing patterns in bilateral posterior crossbite patients was significantly increased compared to control subjects, and the symmetric or asymmetric features of the malocclusion were significantly correlated to the masticatory alterations . Moreover, functional treatment of bilateral posterior crossbite was significantly associated with a reduction in the percentage of reverse chewing patterns. 2) The electromyographic activity of masticatory muscles was significantly increased in patients with deep bite compared to control subjects, and functional treatment of this malocclusion was significantly associated with a reduction in muscular hyperactivity as well as improvement of mandibular kinematics during chewing. 3) Patients with juvenile idiopathic scoliosis showed a significantly increased percentage of reverse chewing patterns compared to control subjects. 4) Functional treatment of posterior crossbite was associated with significant increase of maxillary intermolar and intercanine distances. Moreover, maxillary interdental distances were very stable after follow-up, and the maxillary intermolar distances showed a further significant increase. 5) Patients with unilateral posterior crossbite showed significantly more condylar asymmetry compared to patients with symmetric occlusion. Moreover, functional treatment of unilateral posterior crossbite with the FGB appliance was associated with a significant improvement in condylar asymmetry. 6) Functional treatment of unilateral posterior crossbite was associated with control of the vertical dimension and with a significant improvement in the orientation of the occlusal plane, as well as significant improvement in the position of the mandible, which was showed significant pre-treament clockwise rotation. 7) Unilateral posterior crossbite was significantly associated with postural alterations, as evidenced by significant differences in side-to-side flexion of the spine, which were correlated with the side of the malocclusion. Moreover, occlusal contact reduced postural balance in patients with unilateral posterior crossbite but not in control subjects.