恒牙列拥挤的双生子研究

目的 通过双生子研究遗传和环境因素对恒牙列拥挤形成所起的作用，以进一步研究恒牙列拥挤的影响因素。方法 以48对双生子作为研究对象，应用卵型鉴定技术分为单卵双生子组（MZ）和二卵双生子组（DZ），采取牙牙合]石膏模型并进行测量，获取牙齿近远中径大小、牙弓弧长及牙列拥挤度等数据；采用Holzinger经典双生子法计算遗传度。结果 同卵与二卵双生于牙齿近远中径的平均值差别无统计学意义。说明牙齿近远中径在同卵．二卵双生子样本中平均水平接近。上下颌牙量遗传度较高。上颌为69．97％，下颌为75．73％；上颌牙弓弧长的遗传度（71．26％）明显高于下颌（31．33％）；单卵双生子和二卵双生子上下颌牙齿的拥挤度的对内相关系数较为接近，二卵双生子略低。遗传度很低，上颌为4．73％，下颌为10．3％。结论 上下颌牙量大小和上颌牙弓弧长受较强遗传控制。下颌牙弓弧长受弱遗传控制，恒牙列拥挤度遗传度很低，受环境因素影响较大。

A Twin Study of Dental Crowding on Permanent Dentition

Objective To study the effects of environmental and genetic factors on dental crowding, and to further study on the influencing factors on permanent dentition. Methods Forty-eight pairs of twins were collected. Twin zygosity diagnosis were made by micrsatellite DNA polymorphism. The collected data included clinical oral examination and measurements of dental model. The heritability of tooth mesiodistal diameter (MD), the length of dental arch and crowding factor were systematically analyzed. Results There was no statistical significance in MD between MZ and DZ, that indicated average values of all the dental traits were similar. The heritability of both maxillary (69.97%) and mandibular (75.73%) teeth MD were high. The heritability of maxillary arch length (71.26%) was higher than the mandibular one (31.33%). The intraclass correlation coefficients were similar in dental crowding between MZ and DZ, with the lower in DZ. Low heritability of dental crowding was found in both maxillary (4.73%) and mandibular (10.3%) teeth. Conclusion The maxillary teeth MD, the mandibular teeth MD and the length of maxillary dental arch are controlled under strong genetic factors. The length of mandibular dental arch is controlled under weak genetic factors. Both maxillary and mandibular crowding are influenced by the environmental factors.