Cleft lip and/or palate (CLP) is among the most common congenital human malformations. Failure of fusion of the maxillary and medial nasal prominences or between the palatal processes results in clefts of varying extent, unilaterally or bilaterally. CLP affects between one and seven out of 1000 newborns [1, 2]. The frequency of cleft is higher in Asian people than in other races [3, 4].
Tooth agenesis, also known as hypodontia or congenital absence of teeth, is the most frequently observed developmental anomaly of the human dentition. The prevalence of congenitally missing teeth in the general population has been reported within a range of 0.027 to 10.1 %, which varies greatly according to geographic location and race [5–7]. Clefts of all types are often associated with congenitally missing teeth, and when compared with the general population, subjects with CLP have always been found to have a higher prevalence of dental anomalies, such as variations in tooth number and position, and reduced tooth dimensions, most of which are localized in the area of the cleft defect [9–11]. Rullo et al. examined the prevalence of different types of dental anomalies in children with cleft and found that congenital absence of the cleft-side lateral incisor was observed in 40 % of the samples and a total of 30 % patients showed supernumerary teeth at the incisors region .
Baek and Kim  investigated the differences in the congenital missing teeth pattern in terms of tooth type and cleft sidedness in Korean CLP patients and found that boys had more congenital missing maxillary lateral incisors on the cleft side than girls, but on the non-cleft side, the congenital absence of the maxillary second premolar was more frequent in girls.
To date, few researches have individually studied the different types of cleft including unilateral or bilateral cleft lip, cleft palate, cleft lip and palate, and cleft alveolus and the incidence of tooth agenesis in each type. Therefore, the aim of this study was to investigate the prevalence of different cleft types, cleft sidedness, and congenitally missing teeth in each cleft type.