Dental Education Lecture: Formation of Cervical Defects
Cervical (meaning neck) defect is quite common (Fig.1: ), causing tooth sensitivity. It is found in the neck of the tooth immediately above the crown (actually enamel, arrowheads). The neck (i.e., root) needs to be exposed before it becomes worn off. Root exposure is due to gum recession. The latter is caused by improper oral hygiene and tartar (T). The basis of gum recession is bone loss. Let us look at cross sections to see how the defect forms. We cannot see the gums in CT. We instead use bone level (red arrowheads:< in Fig.2-7) to tell how badly our tooth (root) gets exposed over the time. When our tooth just erupts, bone (red <) is close to the crown (Fig.2: white <). Crown is covered by enamel (E, particularly white area), whereas the majority of the tooth is the dentin (d in Fig.2). Inside the dentin is the nerve (N in Fig.3). If we practice good oral hygiene, bone does not recede much (Fig.3 at age of 20, Fig.4 at the age of 36). If we do not, bone recedes a lot (a large separation between red and white <, Fig.5,6 at ~50) with formation of cervical defect (D, compare to Fig.1). The distance between the defect and the inner surface of the dentin (yellow line in Fig.5) is less (compare to Fig.2-4). It is the basis of tooth sensitivity. Our nerve is closer to outside would! But our body never sits without a fight. After the nerve is irritated, more dentin forms (bulging yellow line in Fig.6, as compared to that in Fig.5) to make tooth less sensitive. Sometimes such fight is in vain. Filling is required to relieve pain (Fig.7: F). Bone recession in this patient (at ~ 40) is quite severe (red <), suggesting that age is not the most important factor for root exposure. Let us make section through this tooth (white lines in Fig.7) to see how tightly the filling (F) binds to the defect (Fig.8).
Xin Wei, DDS, PhD, MS 1st edition 03/2/2011, last revision 04/07/2011