Characteristics Of Occlusal Contact In Subjects With Normal Dentition During Lateral Excursion

Lateral occlusal contact, as anterior guidance during lateral excursion, plays an important role in the mandibular functional movement. Canine protection and group function have been widely acknowledged as two basic patterns of lateral occlusal contact in the normal dentition for many years, and there is little uniform scientific evidence supporting the former in favor of the latter or vice versa. Nevertheless, several recent studies have noted that there were other patterns of lateral occlusal contacts besides canine protection and group function in the normal dentition, and the two basic occlusal patterns may have different effects on the stomatognathic system. Consequently, many investigators have suspected the existing theories of lateral occlusal contact, but they failed to present new classification of the lateral occlusal patterns, or clarify the different occlusal patterns' effects on the stomatognathic system. There is also little consensus on which pattern of lateral occlusal is involved in the clinical treatment of dentition defect,occlusal construction,implant-supported denture,occlusal adjustment,orthodontics and so on. In order to evaluate the validity of canine protection and group function as categories for the classification of lateral occlusal contact patterns in the normal dentition and the relationship between the mandibular position and the occlusal contact, the present study was performed to observe the distributive characteristics of dynamic occlusal contacts during the whole lateral excursion and classify the patterns of the occlusal contacts in the canine-to-canine position with T-Scanâ…¡occlusal imaging and analysis system. Since the occlusal force is an key indicator for the health of the stomatognathic system, the study was also carried out to compare the relative occlusal forces of the subjects with different lateral occlusal patterns in canine-to-canine position based on the classification of the lateral occlusal patterns so as to provide experimental evidence for further elucidating the relationship between lateral occlusal patterns and the stomatognathic system.Partâ… Patterns and distributive characteristics of occlusal contact in subjects with normal dentition during lateral excursionObjective: To observe the distributive characteristics of occlusal contact during lateral excursion in subjects with individual normal occlusion, and classify the patterns of occlusal contact in canine-to-canine position.Materials and Methods: Lateral occlusal contacts from intercuspal position through canine-to-canine position to the maximal lateral position in 85 undergraduates with individual normal occlusion were examined with T-Scanâ…¡occlusal imaging and analysis system, and the frequencies of occlusal contacts in three different positions were described in detail. The lateral occlusal patterns in canine-to-canine position were classified and analyzed.Results: Simultaneous tooth contact occurred on the working and nonworking side adjacent the intercuspal position. The lateral disclusion was observed later, close to the canine-to-canine position. The occlusal contact at that time showed a marked prevalence of canine and posterior tooth contacts on the working side. In canine-to-canine position, the occlusal contact mode was classified into six groups: canine protection(44.1%),group function (20.6%),simultaneous contacts of several anterior teeth on the working side (2.9%),only contact of first premolars on the working side(8.8%),simultaneous contacts of several anterior and posterior teeth on the working side (20.0%),simultaneous contacts of teeth on the working side and the nonworking side (3.5%). In the maximal lateral position, more maxilla-mandibular anterior tooth contacted reciprocally.Conclusion: The results indicate that using only canine protection and group function as categories for the classification of lateral occlusal contact patterns cannot accurately reflect the characteristics of lateral occlusal contacts in the normal dentition.Partâ…¡Comparative study of the relative occlusal forces in subjects with different lateral occlusal patterns in canine-to-canine position Objective: To compare the relative occlusal forces of subjects with different lateral occlusal patterns in canine-to-canine position.Materials and Methods: The occlusal forces of all subjects in Partâ… from intercuspal position to canine-to-canine position were examined with the T-Scanâ…¡occlusal imaging and analysis system. The occlusal forces in canine-to-canine position relative to that in intercuspal position were collected and analyzed by multiple regression analysis.Results: The occlusal forces of all the subjects decreased gradually from intercuspation position to canine-to-canine position during the whole process of lateral excursion. There was significant statistical difference in the relative occlusal forces regarding different lateral occlusal pattern in canine-to-canine position, and the occlusal forces of the subjects with canine protection or only contact of first premolars on the working side were the lowest.Conclusion: The results suggest that the canine has the ability of "stress breaking", and canine protection, comparing to other lateral occlusal patterns, may be the most preferable and beneficial for the stomatognathic system.