While intraorally measuring condylar paths for complete dentures, Danish dentist Carl Christensen (1857-1921) observed a separation in coplanar occlusion rims and steep condylar paths. The phenomenon by which localized gaps appear between the rows of teeth during lateral or protrusive movements while partial functional contacts are maintained is named after him: Christensen's phenomenon (Fig 7-13).This phenomenon denotes the functional separation into working side and nonworking side, or selective tooth contact. In a fully dentate dentition, this is a necessary step to avoid premature contacts with unused teeth, which can lead to periodontal damage.
Sagittal Christensen's phenomenon denotes the separation in the area of the posterior teeth during protrusive movement when both condyles slide downward and forward and the mandible is depressed dorsally (see Fig 7-13).
Transverse Christensen's phenomenon arises during lateral movement when the nonworking condyle slides downward and forward onto the articular tubercle, the mandible is depressed on one side, and, on that side, the teeth come out of contact (Figs 7-14 and 7-15); meanwhile, on the laterotrusive side, the working condyle slides backward and outward in keeping with Bennett (lateral) movement, and full functional tooth contact is achieved.
If the difference in position is to be eliminated in the case of occlusion rims, these need to be shaped in curves that correspond to the course of the occlusal curves but are slightly more arched (Figs 7-16). These curves then compensate for the separation of the occlusion rims in the molar area and are therefore referred to as compensatory curves (Fig 7-17).