Longitudinal study of time and sequence of primary teeth eruption in children, residents in Tehran, from birth (2000-2002) Dr. J. Mahmoodian * - Dr. M. Ghandehari ** - Dr. M. Khojani *** * - Associate Professor of Pedodontics Dept. - Faculty of Dentistry – Tehran University of Medical Sciences. ** - Assistant Professor of Pedodontics Dept. – Faculty of Dentistry – Tehran University of Medical Sciences. *** - Pedodontist Background and Aim: Having knowledge about the exact time and sequence of primary teeth eruption for dentists and especially pedodontists, to design an appropriate treatment plan is essential. The aim of this study was to determine the rime and sequence of primary teeth eruption among children residing in Tehran from birth (2000 – 2002). Materials and Methods: To achieve true statistics of time and sequence of primary teeth eruption, 542 newborn children, whose parents had lived for at least three years in Tehran, were selected randomly from five areas in Tehran. During more than two and half years follow–up,785 of them continued their co-operation. In this descriptive longitudinal cohort study, statistical analysis was performed using t–test at P<0.05 level of significance. Results: The time of tooth eruption, in right and left sides of both jaws, were similar. Mandibular central incisors and second molars, in both sexes, erupted faster than the same teeth in maxilla. The average duration of eruption, in both sexes, did not have any significant difference. Time and sequence of eruption of primary teeth in month were as follows: 1- Mandibullar central incisors (7.88) with S.D (2.4) 2- Maxillary central incisors (9.53) with S.D (2.26) 3- Maxillary central incisors (11.52) with S.D (3.25) 4- Maxillary central incisors (12.70) with S.D (3.42) 5- Maxillary first molars (15.72) with S.D (2.94) 6- Maxillary first molars (16.12) with S.D (2.85) 7- Maxillary canines (18.25) with S.D (3.12) 8- Maxillary canines (18.80) with S.D (3.42) 9- Maxillary second molars (24.74) with S.D (3.59) 10- Maxillary second molars(24.82) with S.D (3.47) The average time of maxillary central incisors and mandibular right incisor eruption was significantly earlier in boys than girls(P< 0.05). Conclusion: There is not any difference in the eruption of teeth quadrant, mandibular central incisors and second molars erupt faster than those in maxilla. No difference was found in the mean duration of eruption. Key words: Primary teeth – Sequence of eruption – Time of eruption | 
