Measurement of mechanical strain on mandibular surface with mastication robot: influence of muscle loading direction and magnitude.
OBJECTIVE
To investigate the mechanical effects of mastication on the mandible, we developed computational controlled mastication robot system with human dry skull and analyzed the strain distribution on the mandibular bone surface.


METHODS
In the mastication robot, the mandible was suspended by eight wires, which simulated masticatory muscles. A non-linear spring damper generated viscoelastic properties, and tension sensors for simulation of jaw reflection to avoid unusual biting force were applied as a biological feedback mechanism. By using this robot system, various patterns of muscle loading (change of wire direction and magnitude) were performed.


RESULTS
From the results, significant differences in the amount of principal strain and its distribution were demonstrated in each condition (ANOVA, post hoc test, and p < 0.05). The value of maximum principal strain ranged from 79.66 x 10(-6) [at anterior border of ramus (Buccal side), 128 N] to -1.42 x 10(-6) [at foramen mentale (Buccal side), 32 N].


CONCLUSIONS
These results suggested that the muscle loading generated the mechanical strain on the mandibular bone surface and it was affected by the changes in loading direction and magnitude.
Usui
T
T
Department of Orthodontics, Showa University, Tokyo, Japan. toshiro@senzoku.showa-u.ac.jp
Maki
K
K
Toki
Y
Y
Shibasaki
Y
Y
Takanobu
H
H
Takanishi
A
A
Hatcher
D
D
Miller
A
A
D000704:Analysis of Variance; D001732:Bite Force; D003198:Computer Simulation; D004548:Elasticity; D006801:Humans; D008334:Mandible / Q000502:physiology*; D008409:Mastication / Q000502:physiology*; D008410:Masticatory Muscles / Q000502:physiology*; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology; D012371:Robotics / Q000295:instrumentation*; D013314:Stress, Mechanical; D014783:Viscosity; D016474:Weight-Bearing / Q000502:physiology