Effect of clenching level on mandibular displacement in Kennedy Class II partially edentulous patients.
OBJECTIVE
Forceful clenching in the intercuspal position has the potential to cause significant mandibular displacement. Such a displacement can be expected to be exaggerated in patients without molar support. The appropriate clenching level for intercuspal position registration or evaluation in these patients has never been clarified. The aim of this study was to clarify the effect of clenching level and absence of posterior occlusal support on mandibular displacement.


METHODS
Thirteen women with a unilateral edentulous area posterior to the first premolar were enrolled in this study. They were asked to perform intercuspal clenching at various occlusal force levels, and 3-D mandibular displacements were measured by an optoelectronic method. The effects of "clenching force level" and "side of molar tooth loss" on the displacements of the condylar and second molar points were analyzed.


RESULTS
The mandible was elevated without substantial horizontal displacements during each clenching task. The effect of clenching level on vertical mandibular displacement was significant, with a clenching level > or = 50% of maximal voluntary contraction causing significantly greater elevations (P < .05). Clenching > or = 50% of maximal voluntary contraction caused consistent tipping of the mandible, with greater elevation on the edentulous side (P < .05).


CONCLUSIONS
The clenching level should not surpass 50% of maximal voluntary contraction for registration or evaluation of intercuspal position in Kennedy Class II patients.
Yamazaki
Mayumi
M
Department of Masticatory Function Rehabilitation, Division of Oral Health Sciences, Tokyo Medical and Dental University, Japan. m.yamazaki.rpro@tmd.ac.jp
Yugami
Kei
K
Baba
Kazuyoshi
K
Ohyama
Takashi
T
D000368:Aged; D000704:Analysis of Variance; D001732:Bite Force; D003768:Dental Occlusion, Centric; D004576:Electromyography; D004581:Electronics / Q000295:instrumentation; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007574:Jaw Relation Record; D007576:Jaw, Edentulous, Partially / Q000145:classification* / Q000503:physiopathology; D008334:Mandible / Q000503:physiopathology*; D008335:Mandibular Condyle / Q000503:physiopathology; D008875:Middle Aged; D008963:Molar; D009068:Movement; D009119:Muscle Contraction / Q000502:physiology*; D055095:Optics and Photonics / Q000295:instrumentation; D016388:Tooth Loss / Q000503:physiopathology; D014716:Vertical Dimension