Morphometric Assessment of the Cranial base in Children with Class II and Class III Malocclusions

Autor: Shu-Hui Hsieh, 謝淑慧
Rok vydání: 2005
Druh dokumentu: 學位論文 ; thesis
Popis: 93
The concept of the shape of the cranial base was formed earlier has been reported in reviewing papers. However, the association between cranial base morphology and malocclusions is still controversial. Besides, we didn’t establish the data base of our own nation. Clinically, we often meet the children at late mixed dentition and early permanent dentition. At these stages, they still have growth potential, therefore, the treatment of growth modification is possible to decrease skeletal discrepancy. If we know the cranial base morphology of the children at these stages, it might been mean that the finial skeletal pattern of jaw bones is knowned. Thus, the diagnosis and the treatment planning may be decided. The purpose of this study was to investigate the morphological characteristics of the cranial base in children with Class II and Class III malocclusions. Lateral cephalograms of 80 children with Class II division 1 malocclusion and of 80 children with Class III malocclusion both compared with 80 children with normal occlusion. The ages of the children were ranged from 9.1 years old to 11.7 years old. Fourteen landmarks were identified and digitized. Cephalometric analysis utilizing 20 linear and 14 angular measurements were undertaken. Before the undergoing of the Student’s t-test and multivariable analysis (Hotelling’s T2 test) of the measurements of the cranial base, the relationships of the maxilla and mandible between Class II and normal occlusion, Class III and normal occlusion were compared firstly to confirm that there’s some significant difference in the relationships of the maxilla and the mandible between groups. The conclusions are as followed: 1.There is some significant difference in the morphology of the cranial base between the children with Class II malocclusion and normal occlusion. The children with Class II malocclusion have longer total cranial base length (N -Ar, N-Ba) and more flattening cranial base angle (N-S-Ar, N-Pc-Ar, N-S-Ba, �Λ-Pc-Ba, N-S-Bo, N-Pc-Bo). The reasons of the flattening of the cranial base angle are the inclination of the anterior cranial base is more steep (the angle of SN/FH is larger) and that of the posterior cranial base is more flattening (the angle of BaS/FH and BoS/FH are larger). The above findings mean that the positions of Ba and Bo are more posteriorly. Besides, the results of the Hotelling’s T2 test show that linear and angular measurements are significant different between groups of Class II and normal occlusions. 2.There is some significant difference in the morphology of the cranial base between the children with Class III malocclusion and normal occlusion. The children with Class III malocclusion have shorter total cranial base length (N-Ar, N-Ba, N-Bo), anterior cranial base (S-N, S-Gl) and posterior cranial base (S-Ar, S-Ba). Linear mearsurements of Ar-PM, Ba-PM, Bo-PM, Se-Ar, Se-Ba are also shorter in the children with Class III malocclusion. The cranial base angles (N-S-Ar, N-Pc-Ar, N-S-Ba, N-S-Bo, N-Pc-Bo) are more acute. The main reason of the more acute cranial base angle is the inclination of the posterior cranial base is more steep (the angles of ArS/FH, BaS/FH, BoS/FH are larger). The above findings mean that the position of Ar, Ba an Bo are more anteriorly. Besides, the results of Hotelling’s T2 test show that linear and angular measurements are significant different between groups of Class III and normal occlusions. 3.There is indeed significant difference in the morphology of the cranial base between the children with Class II and normal occlusion, with Class III and normal occlusion in this study. However, the real relationship between the morphology of the cranial base and malocclusions still needs to evaluate the size and shape of the maxilla and the mandible. In this study, we didn’t analyze the maxilla and the mandible individually. Further study with geometric morphometric analysis is warranted.
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