Introduction to Teeth - Dental Biotribology - page 7

Fig. 1.3 Schematic drawing
of interoral movements of
teeth [ 27 , 28 ]

a

b

Open phase mastication Close phase mastication

d

c

Toothbrushing

Thegosis/bruxism

Fig. 1.4 Relationship
between sine curve and
masticatory loading patterns
[ 29 ]

(complete penetration of the food bolus, if present) contacting of the opposing teeth
surfaces [ 29 ]. A simplified drawing of the chewing cycle is displayed in Fig. 1.3 .
Literature shows that the shape of the occlusal force curve is similar to the posi-
tive half of a sine curve, but asymmetric mainly because of the irregularity of some
foods [ 30 , 31 ], as shown in Fig. 1.4 . During normal chewing, the loads applied to
the teeth are in the range of 10-20 N at the initial contact [ 32 ] and are increased to the
range of 50-150 N at the end of the chewing cycle [ 33 , 34 ]. The magnitude of the
force depends mainly upon the physical properties of food. Given the great variety
of foods, various forces can be expected. In addition, the maximum biting forces
vary according to gender, age, and muscle build. Typically, the maximum biting
load at the incisors is 100 N, gradually increasing as one moves posteriorly, to reach
around 500 N at the molars.
General chewing parameters [ 26 , 27 , 35 ] are listed in Table 1.3 . The total dura-
tion of a chewing cycle has been shown to be about 0.70 s, while the mean duration
of the occlusion is about 0.10 s [ 27 ], and these periods add up to 15-30 min of
actual contact loading each day [ 26 ]. The speed of teeth sliding ranges between
0.25-0.50 mm/s. Tooth-on-tooth sliding distances are around 0.9-1.2 mm [ 26 ].