Abstract
The influence of defective anterior guidance on occlusal function has been broadly studied; however, the effect of the lack of the anterior component of anterior guidance in some patient populations is unclear. The objective of this study was to investigate the state of oral function in open bite patients (OBPs) in order to determine the physiological importance of anterior guidance. Thirteen female open bite patients (age range 15-27) were selected for this study from the Orthodontics Clinic of this University prior to treatment. The following parameters of oral function were evaluated: 1) occlusal contacts in the intercuspal position (IP) and lateral eccentric position, 2) analysis of skeletal patterns with lateral cephalometry, 3) distribution of signs and symptoms of temporomandibular disorder (TMD), 4) bite force, as measured with the Dental Prescale, 5) analysis of tridimensional jaw and condylar movements with a 6-degree-of-freedom measuring device (JKN-1) .
OBPs with occlusal contact points only in the molar teeth in IP were classified as M Type (7 OBPs), and those with molar and premolar contact points as MP Type (6 OBPs) . Five M Type OBPs showed Class II skeletal patterns, but the skeletal patterns of the MP Type OBPs varied between Class I and Class III; this implies that the skeletal pattern may affect the number of contacting teeth. Five M Type OBPs, who had Class II skeletal patterns, were diagnosed as TMD patients.
Mandibular stability was determined from the convergence and the paths of the incisal and condylar points in the sagittal and frontal planes during tapping and clenching; although it was reduced in both groups, the jaw movements in the M Type, particularly the Class II OBPs, were considered much more unstable than in the MP group. It was assumed that this was due to the finding that the M Type showed significantly shorter moment arms between the condyles and the guiding teeth. The latter suggests that, aside from the neurophysiological properties of the teeth, the longer the moment arm between the condyles and the guiding teeth becomes, as in canine guidance or group function, the finer the control of lateral jaw movements might be. It was concluded that such occlusal schemes of anterior guidance are essential for mandibular stability and smooth functional jaw movements, and therefore it should be restored in all patient populations.
