Abstract
The purpose of this study was to clarify the anatomical forms and occurence of accessory foramina. The pulp chamber floors of 85 permanent molars obtained from 11 adult beagle dogs were examined histologically by optical microscopy. The results were based on a comparison between matured and immatured permanent teeth. The following conclusions were obtained.
1) Dentine in the pulpal chamber floor of the matured permanent molar was separated into two layers by terminal line, but in the immatured permanent molar dentin, this two layer structure was not detectable.
2) Sixty-six accessory foramina were observed in 50 molars (58.8%) out of 85 molars with an average of 1.3 per teeth. There was no significant difference in occurrence or number of accessory foramina.
3) Accessory foramina were classified into five patterns. Accessory foramina which opened to furcation area were most frequent (47.0%). The percentage of accessory foramina which penetrated into the pulpal floor (10.6%) was significantly lower than that of the non-penetrated foramina (89.4%). Significantly more penetrated foramina were observed in the immatured permanent molars than in the matured permanent molars.
