In orthodontics, no consensus exists on how to move teeth most efficiently.
The aim of the present study was to investigate the effect of two differen
t force regimes and two different force magnitudes on tooth displacement. A
split mouth design study was conducted in young adult beagle dogs. In each
dog, both mandibular third premolars were extracted, and orthodontic appli
ances were placed for bodily distalization of the second: premolars. The fo
rces (10 cN or 25 cN) were applied, either continuously (24 h a day) or dis
continuously (active 16 h daily from 17.00 till 9.00). Individual time-disp
lacement curves of the second premolars were constructed. Four phases of to
oth movement could be distinguished. Statistical analysis showed that the c
hoice of regime had an influence on the duration of the hyalinisation phase
, while force magnitude had not. The rate of tooth movement in the linear p
hase was mainly regime dependent. However, force magnitude also appeared to
have some influence. The individual tissue response in each dog appeared t
o have an influence on both the duration of the second phase and the rate i
n the fourth phase. It was concluded that under these experimental conditio
ns, force regime has more influence on the rate of orthodontic tooth moveme
nt than force magnitude.