Postgraduate student of orthodontics, Faculty of Dentistry, Tehran University of Medical Sciences. Tehran, Iran



Aim: the prevalence of maxillary missing lateral incisor (MMLI) is 1-2% which is responsible for 20% of all missing teeth. Increased knowledge of causes and clinical manifestations of cases with this situation can be helpful in their diagnosis and treatment planning. The aim of the present study was to determine dental and skeletal features of patients with missing of maxillary lateral incisors. 
Materials and methods: The material consisted of pre-treatment dental casts and cephalograms of 26 patients (14 females and 12 males with average age of 17.5) with unilateral or bilateral MMLI. The following parameters were measured on the dental casts: the maxillary and mandibular intercanine width (ICW) and intermolar width (IMW), overjet, overbite, missing or anomalous of other teeth. Parameters that were measured on cephalogram including: SNA, SNB and ANB angle and Wits. The parameters were finally compared to a control group with normal occlusion by means of paired t-test. 
Results: Eight subjects out of 26 patients with MMLI had bilateral missing and from 18 subjects with unilateral missing, 66.67% (12 subjects) had lateral missing on the right side. MMLI was associated with other anomalous or congenital tooth absence in 12 subjects. In comparison with control group, the overjet was significantly lesser (p<0.05) and upper and lower ICW were smaller. Both ANB angle and Wits were significantly decreased in lateral missing group ((p<0.05).
Conclusion: Missing of maxillary lateral incisor was highly correlated with other tooth anomalies. Most of patient with this situation had skeletal and dental Class III tendency.