Dental Education Lecture: Tooth Repair
We discuss tooth structure as related to cavity, wear and tear and chip in our last lecture. It is time to know how to fix them.
Fig.1 shows the cross section of a lower front tooth. The pulp (so called nerve) is protected by three hard tissue structures (enamel, dentin and cementum). When we have a small chip as shown in the upper drawing of Fig.2, white filling can easily fix the defect (bottom drawing of Fig.2, arrow). When the chip is big without involvement of the nerve (upper Fig.3), simple filling may be not stable. We need a crown to protect the remaining tooth structure (including nerve). Let me show you every step of crown fabrication. First, use white filling material to restore the basic shape of the crown (gray, bottom Fig.3). Second remove an even, very thin layer of the outermost crown structure to make room for an artificial crown (Fig.4), take an impression and send to lab for fabrication of a crown. Once the latter (arrowhead in Fig.5) is ready, we seat it on the shaved tooth structure (arrow, Fig.5) and cement it (bottom Fig.5). The crown will stay in place for a long time.
When chip is extensive with exposure of nerve (arrow, Fig.6), we need to do root canal (removing inflamed nerve, and placing a filling material inside the canal: 1 in Fig.7), use white filling to restore basic shape (2 in Fig.7) before grinding for a crown (3 in Fig.7). In Lecture Cases of Filling, we show you real cases of tooth repair we have just mentioned.
When our crown is destroyed by a big blow (arrow, Fig.8) with exposure of nerve, simple filling like 2 in Fig.7 may not hold itself and crown (3 in Fig.7) in place. Instead, we need to remove more of root canal filling material (1 in Fig.9) to make space to place a post (2 in Fig.9, so called prefabricated post). After cementing the post in the canal, we build-up crown structure with white filling (3 in Fig.9) around the upper end of the post. Finally cement the crown in place (4 in Fig.9). When the crown destruction is more severe, we need to make a so called cast post (to combine 2 and 3 in Fig.9).
Xin Wei, DDS, PhD, MS 1st edition 1/27/2009, last revision 04/18/2012