Tooth Crown and Root Length Index Measurement of First Maxillary Molar in Western Areas of Liaoning Province

Objective To establish comprehensive crown and root length measurement index through the observation and measurement of the first permanent maxillary molar tooth morphology so as to provide data of crown and root length for further clinical,teaching and scientific research.Methods Fifty first maxillary molars were collected in western areas of Liaoning and the length of the tooth crown and root was measured and the relevant data and ratio were calculated.Results Crown length was(6.95 ± 0.70) mm,root length(14.22 ± 1.97) mm,tooth length(20.56 ± 1.42) mm,crown width was(10.29 ± 0.76) mm,crown thickness(11.53 ± 0.83) mm,neck width(7.72 ± 0.71) mm,neck thickness(10.07 ±1.02) mm,and the ratio of crown and root was(0.49 ± 0.09).Crown was(1.30 ± 0.08) mm wider and(1.11 ±0.06) mm thicker than the neck.Transverse section of crown was(119.15 ±16.61) mm2.Conclusion The full-length and the ratio of the crown and root of the first maxillary permanent molars in the west region of Liaoning Province is slightly below the average level of China,while slightly above that in the Guanzhong region and Wenzhou.