Condylographic evaluation in orthodontics: Study of the quantity of the opening and closing movement in patients with Juvenile Idiopathic Arthritis

Purpose: Juvenile Idiopathic Arthritis (JIA) is a rheumatic disease characterized by chronic joint inflammation, also involving the temporomandibular joint (TMJ) from the first year of life. Inflammation of the TMJ cam lead to signs symptoms of temporomandibular joint disease (TMD), like pain, reduced mouth opening, asymmetrical growth, and development of malocclusion. Therapeutic approach includes early recognition, prevention or blocking of the mechanism of the disease. Currently, the management of TMJ complications is based o a combination of pharmacological, orthodontic, physiotherapeutic and surgical treatments. The radiological exam for diagnosis and monitoring are CT and MRI. Condylography is a instrumental method that allows to simultaneously record and compare paths of both right and left condyles in the three dimensions of space. In this preliminary study the quality of function of TMJ as a sign of friction or interferences during the condylar movement was observed in a group of JIA patients. Materials and Methods: 16 patients suffering from JIA were recruited at the Orthodontic ward of IRCCS Cà Granda Policlinico Hospital Foundation of Milan. Patients with a history of facial trauma, previous orthognathic treatment or prosthetic rehabilitations were excluded. Data on symptoms and clinical pictures were collected: presence of pressure pain or spontaneous, joint noises and reduced oral opening. A series of arbitrary recordings was performed by means of the computerized axiograph CADIAX compact 2 system. This means that the registration of the movement of the mandibular joint was made on one point of the axis anatomically identified hinge. The reference coordinates of the system originate from the central point between the condyles, where the hinge axis, in the zero (centric) position, intersects with the median-sagittal plane. A kinematic face bow (Condylograph) was used for the recordings. All the recordings in their entirety, including the preparation phases and the determination of the hinge axis, were performed by the same operator. A complete axiographic exam was performed but a selection of non-guided open/close curves was tracked for the analysis. Each record therefore included: 1) Electronically recorded jaw movement tracks; 2) Measurement of the condylographic position (CPM); 3) X / Y/ Z coordinates of the tips of the cusps of the teeth of the mandible. The registration data was exported to GAMMA Dental Software and subsequently processed with CADIAX Analyzer. The data concerning the amount of total movement expressed in mm for the two condyles were extrapolated and compared with the average values reported in the literature. A value equal to 10 ± 2 mm has been defined as normal. Therefore, with values lower than 8 mm we will speak of a limitation of movement (hypomobility) and for values higher than 12 mm we will speak of hypermobility. Results and Conclusions: This investigation was performed in frankly dysfunctional patients, therefore the presence of an alteration of movement was foreseeable. Our data show an average mobility value of 5,536 ±1.885 mm. In conclusion, the results of this preliminary study should be verified in a larger population, however condylographic examination could be a valid support for the classification and monitoring of joint pathology as well as for the study of function during orthodontics treatments in JIA patients, thanks to its non-invasiveness, precision and reproducibility.