M. Redlich et al., THE RESPONSE OF SUPRAALVEOLAR GINGIVAL COLLAGEN TO ORTHODONTIC ROTATION MOVEMENT IN DOGS, American journal of orthodontics and dentofacial orthopedics, 110(3), 1996, pp. 247-255
An orthodontically rotated tooth relapses toward its pretreatment posi
tion. Explanations for this phenomenon have been given after light mic
roscopic studies, according to which it lad been assumed that stretche
d supraalveolar gingival fibers pulled back the tooth and brought abou
t relaxation of the stretched fibers. The rotational relapse, however,
can be prevented by supraalveolar fiberotomy of the gingiva around th
e tooth. This investigation was initiated to reevaluate the validity o
f the hitherto assumed causes for the relapse, by obtaining ultrastruc
tural data on the response of collagen fibers after orthodontic interv
ention, Lateral maxillary incisors in the dog were rotated with bonded
fixed appliances. The teeth were divided into groups according to dif
ferent orthodontic procedures. Scanning and transmission electron micr
oscopic analyses were performed on gingival samples after proper proce
ssing. Analyses of the untreated control samples showed well-organized
, parallel, and densely packed thick bundles of collagen fiber;, inter
connected with thin fibers. After rotation-followed-by-retention, the
gingival fibers were torn, ripped, disorganized, and laterally spaced
and of increased diameter. Thus it was concluded that all these patter
ns are incompatible with stretching. Also, an increased number of elas
tic: fibers were seen in proximity to the torn collagen fibers. After
gingival fiberotomy, most fibers resumed the appearance of the organiz
ed pattern of large fiber bundles similar to those seen in tie control
s.