上顎第 1 大臼歯の 4 根管について

Abstract

The authors encountered two extracted molars with four root canals determined to be the left maxillary first molars during an oral treatment practice for the third-year dental student. For these teeth, access cavity preparation and root canal enlargement were performed. One tooth was given root canal filling and the other was investigated radiographically. Clinically also, we encounted two cases of the right maxillary first molar with four root canals, and performed root canal enlargement and root canal filling. The conclusions reached were as follows : 1. Case I : Access cavity preparation was done slightly more extensively than is normally done. Preparation of the mesiobuccal and mesial walls revealed two canals in the mesiobuccal root. These two canals showed complete bifurcation and were highlevel complete bifurcation root canals. 2. Case II : Access cavity preparation was done quite more extensively than is normally done. Extensive preparation of the mesiobuccal wall showed two root canals in the mesiobuccal root. These two root canals were low-level incomplete bifurcation root canals. 3. Casee III : Access cavity preparation was done quite more extensively than is normally done. Careful exploration of the pulp chamber floor after opening the cavity outward revealed bleeding from the orifice of the secondary mesiobuccal canal. These mesiobuccal root canals were high-level complete bifurcation root canals. 4. Case IV : Careful exploration of the pulp chamber floor with an explorer after complete removal of soft dentin revealed two root canals in the mesiobuccal root. These mesiobuccal root canals were high-level complete bifurcation root canals. 5. About 50 to 70% of the maxillary first molars are considered to have four root canals. In treatment of these teeth, therefore, extensive preparation of the cavity without injuring the pulp chamber floor and subsequent careful exploration of the pulp chamber with an explorer are deemed necessary.