Size, ultrastructure, and microhardness of natal teeth with agenesis of permanent successors

Natal and neonatal teeth may occur in conjunction with other oral anomalies, including anomalous development of succedaneous teeth. Our purpose was to examine the size, ultrastructure, and microhardness of two natal teeth without permanent successor germs, and compare them with the characteristics of normal primary teeth.

The dimensions of two natal mandibular incisors extracted from a healthy 7-year-old child were measured with a digital sliding caliper. The crown dimensions of normal primary mandibular central incisors were established from dental casts of 102 children. Since the natal teeth were nearly completely devoid of enamel, the average enamel thickness determined on a sample of 19 normal primary mandibular incisors was added to the values measured. External surfaces and transverse sections of the natal teeth were examined under a scanning electron microscope. Vickers microhardness of radicular dentine was assessed for the natal teeth and for 11 normal primary mandibular incisors.

Only remnants of enamel were present. All crown dimensions corrected for enamel loss were within the normal range. The ultrastructure of hard dental tissues was normal. The radicular dentine hardness of the natal teeth was similar to that of the normal primary mandibular incisors.

The results indicate that the natal teeth were prematurely erupted regular primary mandibular central incisors. In our case, the occurrence of natal teeth associated with agenesis of their primary successors appears to be related to an accelerated or premature pattern of dental development, rather than to superficial positioning of the tooth germs.