Relationships between the root-crown ratio and the loss of occlusal contact and high mandibular plane angle in patients with open bite.
OBJECTIVE
To determine the root-crown (R/C) ratio and dental root length of teeth in patients with open bite and seek any relationships with occlusal contact (OC) and the mandibular plane (Mp) angle.


METHODS
Thirty-one patients with open bite with negative overbite of at least four anterior teeth and 31 control patients with clinically normal overjet and overbite were enrolled. R/C ratios, dental root length, OC, and Mp angle were measured using panoramic radiographs, dental casts, and cephalograms, respectively. Mean differences between the groups, and variations between the R/C ratio or root length and Mp angle in patients with open bite were statistically analyzed.


RESULTS
R/C and OC ratios from the incisors to premolars were significantly lower for patients with open bite than for controls, and some teeth had short dental roots. Relationships between low R/C ratio or root length and high Mp angle were significant in patients with open bite.


CONCLUSIONS
Patients with open bite, especially those with a high Mp angle, have an unfavorable R/C ratio and short dental roots in some teeth, which may be related to the loss of OC.
Department of Orthodontics, Field of Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
Sawako
S
Uehara
Aya
A
Maeda
Hiroshi
H
Tomonari
Shouichi
S
Miyawaki
D000293:Adolescent; D016022:Case-Control Studies; D002508:Cephalometry / Q000379:methods; D002648:Child; D005260:Female; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008297:Male; D008334:Mandible / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D024343:Open Bite / Q000000981:diagnostic imaging / Q000473:pathology*; D011862:Radiography, Panoramic / Q000379:methods; D019228:Tooth Crown / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D014092:Tooth Root / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D014716:Vertical Dimension