Polymorphisms in sequence of permanent tooth emergence: a cross-sectional study on Jordanian children and adolescents

This study aimed at providing the norms of polymorphic gender- variation in the sequence of permanent tooth emergence in Jordanian children and adolescents.

A total of 2650 Jordanian children and adolescents (1232 males and 1418 females) aged 4-16 years were examined for permanent tooth emergence. By counting the cases of present-absent and absent-present across all possible intra-arch tooth pairs, the frequencies of sequence polymorphisms were calculated and expressed as percentages in and arch-specific matrices.

Sequence polymorphisms were more common in tooth pairs in phase II than in phase I of permanent tooth emergence and only rarely did teeth in phase I reverse sequence with teeth in phase II. In addition, maxillary and mandibular polymorphisms were most common in the sequences of canine-second premolar and first premolar-canine, respectively. Furthermore, central incisor-first molar and second molar-second premolar sequences were much more common in the mandible than in the maxilla. It was noticed that males and females had more similar frequencies of polymorphic sequences in the maxillary than in the mandibular tooth pairs.

This study presented the norms of pairwise sequence polymorphisms in permanent tooth emergence in the Jordanians. Such norms are adequately useful for the evaluation and prediction of tooth emergence sequence in individual children and valuable in the assessment of emergence sequence problems in pediatric dentistry and in planning and following-up orthodontic treatment.