Primary Study On The Discrepancy Of Condylar Position Between Centric Relation And Centric Occlusion For Malocclusion And Its Correlation Factors

Objective: The purpose of this study was to identify the differences of occlusion and condyle position between CO(Centric Occlusion) and CR(Centric Relation) in malocclusion patients, and investigate correlation factors of the difference; to discuss the dentofacial development and features of Fujian adults with normal occlusion by Jarabak cephalometric analysis, and provide reference for clinical diagnosis and treatment.Metheods: The occlusion records of 78 malocclusion patients seeking for orthodontic treatment at the Department of Orthodontics, Affiliated Stomatological Hospital of Fjjian Medical University were used. CR position was acquired by two-hand technique and then transfered to AD2 articulator by the AD2 facebow, bite fork and the wax record. The change of occlusion relation was tesed on mounted cast and condylar displacement between CO and CR was tested with AD2 articulator and MCD(Measures Condyle Displacement). Lateral projections of 90 Fujian adults with normal occlusion were analyzed by Jarabak cephalometric analysis using Winceph cephalometric software and the differences between male and female were compared. The normal values of measurement by Jarabak were established for the clinical reference..Results:(1)There was statistical difference between the mean of overbite at CO and CR, so was the same with overjet. The variance of overbite and overjet showed a negative correlation.(2)Nearly all patients had initial contacts in CR position, and 71.8% of the initial contacts occurred on molar. 38.5% patients displayed the transverse shift up to 0.5mm or greater at the level of the condyles. 47.3% patients experienced anteroposterior(AP) condylar displacement of at least 1mm on one or both sides, and 52.6% experienced superoinferior(SI) condylar displacement of at least 1mm on one or both sides, the amout of SI displacement was consistently greater than AP displacement. Weak correlation was found between three-dimensional condyle displacement and patient's gender,ANB angle, gonial angle, ratio of anterior/posterior facial height, the variance of overbite/overje(.3)The normal values of measurement by Jarabak in Fujian were established. The results of the study showed that all linear measurements showed significant differences between male and female. In Europe and Sounth Americal measurements, only the length of antero-basalis showed significant gender differences. This may be originated from the race and location difference. There was no difference between male and female adults in growth pattern this revealed that craniofacial growth was concordant in both genders.Conclusions: Discrepancy of CO-CR occurred in most malocclusion patients. The occlusion in CR position should be analyzed before treatment to reveal the disharmony between occlusion and jaw position, finding out the growth form of patients. According to that we can learn the real occluding relation, make a correct diagnosis and treatment plan, then we can establish the ideal functional occlution, and the therapeutic results will be stable for long term.