Although the number of congenitally missing teeth tends to be substantially greater in the permanent dentition than in the primary dentition, the most frequently missing teeth in the primary dentition are the incisors, while the premolars of the permanent dentition are most commonly absent, if one excludes the third molar teeth [41]. The early-developed tooth tends to behave as an environmental

factor for the adjacent later-developing tooth [42]. Grüneberg [43] learn more stated that if the first molar of the mouse, which was the largest and the earliest developed in the molar row, was reduced, then the second and third molars tended to grow larger than in a normal mouse. Sofaer et al. [44] showed that when a lateral incisor was missing on one side, the central incisor adjacent to the missing tooth tended to be larger than the central incisor on the other side. These researchers also proposed that agenesis of a tooth might lead to an increased growth potential of neighbouring teeth, reflecting a compensatory effect in growth of adjacent developing tooth germs. Hanihara [3] analyzed the relationship in the mesiodistal crown diameters between the maxillary lateral incisor and the other permanent

selleck compound teeth, and showed the size of lateral incisor was highly correlated with the size of the other teeth, i.e. when the lateral incisor is reduced, remaining teeth also tend to be reduced. Garn et al. [45] and [46] showed that agenesis of the third molar tooth was not an isolated anomaly, but rather a polymorphism related to the frequency of other missing teeth. Mizoguchi [47] tested the compensatory interaction hypothesis by using path analysis in a Japanese AZD9291 cost population and he concluded that there was no, or little, compensatory growth of the later-developing teeth in the tooth row from central incisor to second molar in each jaw, but only the third molar grew to compensate for a whole dentition of certain length. Yamada et al. [48] demonstrated that tooth size of the

remaining teeth was greater in a sample with third molar agenesis than in a group where all four third molars were present, with the exception of the maxillary lateral incisor. Their results could be explained to some extent by compensatory interactions within molar tooth row, but it is interesting that the maxillary lateral incisor was reduced in individuals with third molar agenesis. Thus, the maxillary lateral incisor and the third molar are reduced synchronously. There is a tendency for the size of remaining teeth to be more reduced as the number of missing teeth increases, but tooth size in individuals with one or two teeth missing is generally larger than in individuals with all 32 permanent teeth [49].