Authors' response

We thank Dr Wang Jing for his interest in our article and his comments. We set out to investigate patients with buccal displacement of canines before treatment. Thus, no preventive or therapeutic measures had been taken. Nature had generated the buccal displacements, and our aim was to search for clues to any association of this phenomenon with crowding or spacing and with lateral incisor anomaly, and to suggest possible explanations for the occurrence. Crowding was not a factor in the experimental group, since the inclusion criteria provided for a spaced dentition, a priori. Overretained deciduous teeth are most probably the result of the displacement, rather than the cause, and abnormal tooth bud locations could have been found in any of the 3 groups of patients. There was no evidence to implicate pencil biting as an etiologic factor, any more than to blame weight-lifting or vegetarianism.

Dr Jing pointed to the mesial movement of molars after eruption of the premolars and before canine eruption as a factor that might lead to buccal ectopy of the canine because of crowding. This will obviously place such a patient in the BDC-c group, but 1 characteristic of a spaced dentition is a relative lack of mesial migration after the shedding of deciduous teeth—defining the case as a BDC-nc.

We agree that it is equally valid and pertinent, as Dr Jing suggests, to look at patients with spacing or lateral incisor anomaly as the prime grouping agent and then investigate the frequency of crowding or spacing and lateral incisor anomaly. This will likely add new insights into this entire area, but it is a different study!

We set out to contrast crowding (as a cause) with spacing (as a cause); we believe that we achieved it in this study.