*3.1.1 Position of cleft-sided lateral incisor*

When the permanent maxillary lateral incisor is present in CLP patients, it is usually located on the distal side of the cleft [17, 44, 47–50] and is often reported to be delayed in formation and eruption when compared to the antimeric lateral incisor on the non-cleft side [17, 20, 22, 36, 47, 51].

Tsai et al. reported on the discrepancy in distribution patterns of the cleftsided maxillary lateral incisors in the primary and permanent dentition [46]. In the primary dentition, the lateral incisor was located most commonly on the distal side of the alveolar cleft (82.4%), followed by missing cleft-sided maxillary lateral incisor (9.9%), one tooth present on each side of the alveolar cleft (5.5%), and lastly, the lateral incisor was located mesial to the alveolar cleft (2.2%). However, in the permanent dentition, the most predominant pattern was the missing cleftsided maxillary lateral incisor (51.8%), followed by the lateral incisor positioned distal to the alveolar cleft (46%), lateral incisor positioned mesial to the alveolar cleft (1.5%) and the least common finding of one tooth present on each side of the alveolar cleft (0.7%). Due to the difference in the distribution patterns between the primary and permanent dentition, the authors proposed that there may be two odontogenic origins (maxillary and medial nasal process) for the maxillary lateral incisors. Failure of fusion between the two processes could have resulted in unequal mesenchymal mass in each of the segment, hence giving rise to different distribution patterns.
