[Study on development time of mandibular permanent teeth with Demirjian method in 928 children]
1Department of Pediatric Dentistry, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine; Shanghai Key laboratory of Stomatology; National Clinical Research Center of Stomatology. Shanghai 200011, China.
Purpose:
This study aimed to establish the developmental timetable of mandibular permanent teeth in children aged 5-15 years, and analyze the rapid developmental range of each permanent tooth and explore the gender differences in development of permanent teeth.
Methods:
Nine hundred and twenty eight children aged 5-15 years were included, the stage of each mandibular permanent teeth was recorded with Demirjian method. The developmental lines and the fitting curves of each tooth were drawn. The age of the important development nodes was summarized, and the slope of the developmental line was recorded. The similarities and differences between male and female were analyzed with SPSS 22.0 software package.
Results:
Mandibular permanent incisors were found to experience their developmental peak from 6.50 to 7.50 years old, while mandibular permanent premolars' developmental peak were 7.00-8.00 years old. Boys' mandibular first molar reached their peak from 6.50 to 7.50, 8.50 to 9.50 years old, while girls' teeth developed earlier than that of boys, but the developmental rate was similar.
Conclusions:
In this study, the developmental peak and developmental timetable of mandibular permanent teeth suitable for the domestic population were obtained, which was different from the data of other regions and ethnic groups. Females began their mandibular permanent teeth development earlier than males, but the development curve of each tooth was similar.
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