Talking about cracked teeth is sometimes confusing. There are several types of cracked teeth. The treatment and prognosis of a cracked tooth depends on the type, location & severity of the crack.
Types of cracked teeth include: craze lines, fractured cusps, cracked tooth (restorable type and non-restorable type), split tooth & vertical root fracture.
A split tooth is caused by a cracked tooth that has gone untreated over a period of time. The tooth is literally split into two pieces by a crack that runs through the tooth. A tooth can be split mesio-distally or linguo-buccally. The crack of a split tooth includes damage to the root itself. The crack of a split tooth can be seen crossing the floor of the pulpal chamber. This is a sure sign of a non-restorable tooth.
The following case is an example of a split tooth.
This patient presented for endodontic therapy. #15 had a small occlusal amalgam. The tooth is diagnosed as necrotic with symptomatic apical periodontitis.
Close examination of the occlusal surface shows a stained crack on the mesial & distal marginal ridges. You can see that the lingual and buccal surfaces of the tooth have been flexing for an extended period of time. The clinical appearance of this tooth strongly suggests a split tooth. In this case, the patient was informed of the probable non-restorability of this tooth.
Removal of the amalgam shows the connection between the MMR & DMR cracks. The argument for a split tooth becomes even stronger.
After access into the pulpal chamber, the cracks can be traced down the mesial and distal walls and then connecting across the pulpal floor. The diagnosis of split tooth is now confirmed.
Just for fun, transillumination is used to show the cracks.