Association of advanced hypodontia and craniofacial morphology in Japanese orthodontic patients

Abstract

The purpose of this study was to examine the effects of advanced hypodontia on craniofacial morphology in Japanese patients. We defined advanced hypodontia as a congenital absence of four or more permanent teeth, excluding the third molars. Lateral cephalometric radiographs of 20 female orthodontic patients (age range, 8.5 to 19 years; mean age, 13.9 years) were examined. Twentyeight angular and 37 linear measurements were taken from each cephalogram, and these cephalometric data were statistically analyzed and compared with the Japanese cephalometric standards. The most frequently missing teeth were the mandibular and maxillary second premolars, followed by the maxillary first premolars and the maxillary first molars, in that order. Compared with the Japanese standards, a smaller cranial base length and angle, a shorter maxillary length, a slightly prognathic and upward-rotated mandible, and retroclination of the upper and lower incisors were found in the patients studied.These craniofacial anomalies should be taken into consideration in treatment planning and mechanotherapy.

Congenitally Missing Mandibular Incisors and Mandibular Symphysis Morphology

“…The most striking finding of craniofacial morphology in this study was the significantly greater retroclination of the mandibular incisors in group 1M as compared with group C. Similar findings have been reported by other researchers investigating individuals with severe hypodontia, 12,15,16 and with anterior and/or posterior hypodontia. 14 The mandibular incisor retroclination found in our study may have been due to a disturbance in a tongue-lip pressure balance and a lack of lingual support as a consequence of mandibular incisor agenesis.…”

“…[12][13][14][15][16][17][18][19][20][21][22] In the present study, we made an extensive investigation of the possible influences of the congenital absence of mandibular incisors on the mandibular symphysis morphology using area measurements in addition to traditional measurements. The mandibular symphysis area was significantly smaller in groups 2M and M than in group C, although neither mandibular symphysis height nor thickness showed any significant differences between the groups.…”

“…All the points and lines except for Id, LId, Idm, U1a, L1a, and the z-axis were described previously. 12,14 The definitions of these measurements were as follows: Id indicates infradentale; LId, lingual infradentale; Idm, a midpoint of Id and LId; U1a, upper incisor root apex; L1a, lower incisor root apex; and z-axis, a line perpendicular to the mandibular plane through menton.…”

“…Thirteen angular measurements, the definitions of which were described previously, 12,14 were selected for quantitative cephalometric evaluation of craniofacial morphology. For each cephalometric evaluation of mandibular symphysis morphology, four angular and eight linear measurements were made with digital calipers and a protractor, and three area measurements were made with a computer system including a Scion Image software program (Scion Corp, Frederick, Md; Table 2).…”

“…Several studies have shown the association of hypodontia with smaller cranial base length [12][13][14] and angle, 12,15 more retrognathic [15][16][17][18] and shorter maxilla, [12][13][14]17,19 more prognathic mandible, [12][13][14]20 smaller mandibular plane 13,15,20 and sagittal jaw relationship angles, 15,16 straighter facial convexity, 15,17,18 greater retroclination of maxillary 12,[14][15][16]18 and mandibular incisors, 12,[14][15][16] larger interincisal angle, 12,14,15,18 and shorter lower anterior facial height. 13,15 However, some other studies have revealed that hypodontia has little or no effects on craniofacial morphology.…”