Is the Enamel Smooth? 

Our teeth look beautiful, because they are white and smooth.  Is it true?  Our teeth may look smooth from distance (Fig.1 *, central incisors of a 8-year-old girl), but the close-by photo shows that the surface of other permanent teeth (Fig.2 <) have seemingly countless wavy lines.  This feature is more distinct in a 8-year-old boy: almost every of recently erupted permanent front teeth having wavy lines (Fig.3).  It suggests that our teeth consist of millions of thin segments.  During their development, thin segments deposit layer by layer in a sequence as indicated by an arrow in Fig.4.  If our teeth look bad in a particular area as discussed below, the doctor may estimate when enamel formation is disrupted.  Why do most of our teeth look smooth?  Probably as we age and eat, food smoothens the tinny tiny lines.

The teeth in Fig.5 do not look so beautiful.  The front teeth have several horizontal unsighted white bands, at the similar patterns as the horizontal lines mentioned above.  The enamel below the black dashed line appears relatively normal.  In contrast, the portion of the enamel immediately above the dashed line is affected (messed up) most severely.  There is a broad white band or yellow stain (Fig.6, not best shown).  In fact this condition can be treated by whitening.

Xin Wei, DDS, PhD, MS 1st edition 08/08/2012, last revision 08/08/2012