Access related endodontic mishaps
Treatment of the Wrong Tooth
Treatment of the wrong tooth can be so easily prevented. One should make sure through inquiry, testing, examining, and radiography that one has confirmed which tooth requires treatment and then mark it with a felt-tip pen (Figure 1).
Additional canals in the mesial roots of maxillary molars and the distal roots of mandibular molars are the most frequently missed. Second canals in lower incisors, and second canals and bifurcated canals in lower premolars, as well as third canals in upper premolars are also missed. One must be diligent and prepare adequate occlusal access! Always expect there will be an extra canal.
Magnification with either telescopic lenses or a surgical microscope is indispensable (Figure 2).
Damage to an Existing Restoration
Porcelain crowns are the most susceptible to chipping and fracture. When one is present, use a water-cooled, smooth diamond point and do not force the stone. Let it cut its own way (Figure 3). Also, do not place a rubber dam clamp on the gingiva of any porcelain or porcelain-faced crown.
Access Cavity Perforations
Often the first sign of an access cavity perforation is blood in the cavity or the patient complaining of a taste of NaOCl. This most frequently happens in the floor of molar preparations when one is searching for a third or fourth canal. The site of the perforation must be found, the floor of the preparation cleansed, the bleeding stopped, and mineral trioxide aggregate (MTA) applied to the perforation (Figure 4).
Because it takes MTA more than 3 hours to set, it should be covered with a fast-setting cement. The other canal orifices should be protected by placing paper points or an instrument in the canals to prevent blockage. In the event MTA cannot be immediately applied, it is best to stop the bleeding, place calcium hydroxide over the “wound,” place a good temporary filling, and set an appointment with the patient, the sooner the better. The perforation area will be dry at the next appointment; then MTA can be applied and treatment continued.
Remember, preparing an endodontic access cavity in a tooth, particularly a molar or premolar with a large restoration, materially weakens the crown. Infrequently the crown fractures, either during preparation or at a subsequent appointment. One of the frequent causes is failure to relieve the occlusion. If the fracture is chisel shaped and a cusp breaks off down to the periodontal ligament, the tooth can usually be salvaged. If the fracture extends through the pulp chamber and down into the root, however, the case is hopeless and
the tooth should be extracted.