| Background:Orthodontists and patients all focus on the outcome of the orthodontic treatment. The improved patients' profile, stable occlusion are the pursuing goals of the orthodontists. Facial beauty depends on the form, proportion and position of its various units. The chin is the most prominent element of the lower third of the face. The coordination of nose, lips, and chin is an important symbol of the beauty facial standard. The relationship between mental region and facial profile is the problem to which the orthodontists pay great attention.Objective:In order to determine if the mental region presents with any unusual appearance, one must study the morphology of the mental region. Morphology may vary from individual to individual, and the establishment any abnormal standards will aid in the process of eliminating any abnormality in such important region. The purpose of this study was to describe and analysis the profile and morphometric of the chin and measure the size and shape of the mental region to determine differences due to gender, age or subjects with skeletal types. Methods:Lateral cephalometric radiographs of 174 individuals (81 males and 93 females) with an age range of 12 - 30 years were selected and distributed according to tendence of skeletal facial pattern ( 63 Class I, 61 Class II, and 50 Class III). Each radiograph was analyzed and measured to determine the profile and morphometric of the chin. Three angular and five linear measurements were constructed for the morphometric chin analysis. One-way analysis of variance was performed to study the relationship among gender, age and skeletal type and a multiple comparison test was used to further distinguish which skeletal pattern tendence suggested significant difference in introcession of the mental region. Regression analysis was also used to test the interrelationship of the variables of gender, age, and skeletal type; with the linear measurements of the chin (significance was calculated at the 0.05 level).Results:The results indicate that the profile of chin presented with prominent profile in the majority of index (70%), regardless of gender, age, or skeletal type. The significant differences existed between height of chin and genders, the average height of chin for males was 32.443±3.063mm, while female 30.542±2.230mm. When age was evaluated, significant differences in height of chin was found between the older (17 years or more) and the younger (12 - 15 years) age groups (P < 0.01). The height of chin in the older age group was higher than that in the younger age group. Introcession of chin in the older age group was lower than that in the younger age group. When skeletal type was compared with mental region, a significant difference was found in the introcession of chin between the Class II and Class III subjects (P < 0.05). Introcession of hard tissue and soft tissue in Class II group were 2.896±0.672mm and 4.517±1.229mm, while 2.432±0.865mm and 4.114±1.246mm in Class III group. If gender, age, and skeletal type were all compared with regression analyses, the result revealed that age was significantly related to a change of introcession of hard and soft tissue (P < 0.01) and height (P< 0.01). Conclusion:With regard to chin morphology, difference emerged in factor of gender, age, and skeletal facial pattern, which deserves to be taken into consideration in orthodontic treatment planning. The height of chin was increased while aged, and there was difference in male and female. Male had greater height from age 15 than female. This suggested that the gender and age difference in height of chin Profile of chin reported in the current study can be used as reference standards for further investigations involved the mental region in Chinese subjects. |
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