Cervical Defect Leading to Tooth Snap
Cervical defects are quite common, but we do not know why it happens. What we know is that they often occur in the premolars (Fig.1: #12,13), the teeth in front of molar teeth. The defects are usually the most severe when the molars are missing (Fig.1,2: *). Mr. Chen visits our office, complaining that the tooth #13 is mobile (Fig.1). Closer look at Fig.1 shows that the defect is pretty deep. The nerve is exposed (arrowhead: <). Besides there is a crack line (arrow: -->), suggesting that the tooth has snapped. Why does the tooth break?
X-ray demonstrates that the teeth #12 and 13 have root tip infection (Fig.2: >). It means that the nerve inside these two teeth is dead. After the nerve is exposed through the cervical defect, it is dying. The tooth with dead nerve is brittle and weak. Under undue pressure (because of missing two molars), the tooth with a large cervical defect finally gives up, snapping.
Fig.3 is the side view of the tooth #13 after extraction. It reveals a large cervical defect (white arrowheads) and an oblique fracture line (black arrowheads). Cervical (latin) means the neck, a special area of a tooth, between the crown (C) and root (R). The typical cervical defect is V-shaped. Or it looks like a wedge.
When the cervical defect is shallow at early stage, we should place white filling to stop the process. The filling prevents nerve exposure and tooth fracture. Furthermore, the missing molar teeth should be replaced as soon as possible.
Xin Wei, DDS, PhD, MS 1st edition 02/14/2012, last revision 02/14/2012