An experimental study of the effect of extraction and retention of canine primary intruded teeth to the permanent successors

Abstract

Objective: To compare the influence of extraction and retention of the intruded dogs' teeth on permanent successors. Methods: Nine healthy 45-days-old Chinese rural puppies were selected, and six were submitted to the intrusion of the bilateral canine. Intruded teeth on the left side were extracted 30 minutes later and the teeth on the right side were kept in their sockets. After 8 months, all dogs were sacrificed. General observation, periapical radiograph and cone beam CT were used to observe the preoperative and postoperative deciduous teeth, permanent germs and permanent teeth development. The structure and content of successors' enamel were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Results: In the extraction groups, the enamel hypoplasia was found in 19 permanent successors, ectopic eruption in 2 cases and abnormal teeth were in 19 cases in total (79%). In the retention groups, enamel hypoplasia of the permanent successors occurred in 2 cases, root dilaceration in 6 cases, and ectopic eruption in 5 cases, retained deciduous teeth in 3 cases, and there were 22 abnormal teeth in total (92%). In blank control group, there was no abnormal teeth. The major effect of intruded deciduous teeth on the permanent successors exhibited enamel hypoplasia [85% (41/48)], presented as enamel coloration and enamel defect (P=0.416). Conclusions: The intruded deciduous teeth should be removed early in order to reduce the effect on the permanent teeth.