Hajime Wakabayashi

Effect of calcium hydroxide paste dressing on uninstrumented root canal wall

Dissolution of soft tissues on the uninstrumented root canal wall by an intracanal dressing of calcium hydroxide paste was examined by scanning electron microscopy (SEM). The roots of human extracted teeth were split longitudinally into halves, and the pulp tissue was removed by forceps. Then, the halves were divided randomly into three groups. Specimens in the control group were given no treatment. Specimens of the 1-wk group were stored for 7 days in calcium hydroxide-saline paste under the condition of 100% humidity and 37 degrees C. Specimens of the 4-wk group were stored for 28 days in the same manner, but washed and replaced into new paste every week. Root canal walls of these specimens were compared under a scanning electron microscope. A layer of odontoblasts was observed in the control group, whereas it had disappeared completely in the 1- and 4-wk groups. However, the predentin remained almost intact in the 1-wk group, and although the surface was eroded, in the 4-wk group. It was found that calcium hydroxide paste dressing could dissolve the odontoblastic cell layer, but had little effect on predentin.

A clinical technique for the retention of a rubber dam clamp

A simple method for supragingival retention of a rubber dam clamp on teeth without a supragingival undercut is presented. A small amount of self-curing resin mixture is placed at the gingival margin on the reciprocal surfaces of the tooth. After the resin is cured well, a standard calmp is set on the resin spots. With the use of this technique, a clamp can be applied to teeth, even partially erupted teeth and teeth prepared for complete veneer crown, without inducing adverse sequelae on the tooth surface and periodontal tissues.

Scanning electron microscopic study of dentin walls of the pulp chamber by a replica technique.

Precise replicas of the pulp chamber were made with a low-viscosity synthetic resin and examined with a scanning electron microscope. As a result, it was confirmed that the pulp horns and the pulp roof were clearly observed at both low and high magnification by this replica technique. Furthermore, interesting findings were made. That is, a vessel-like linear ridge or groove, measuring 5 micron in diameter, was observed on the surface of the replica. The ridge or groove ran across the top of the pulp horn to the pulp roof in the direction of the other horns. Such a linear ridge or groove was found in 32 of 50 specimens (64%). It may be interpreted that there was a stringy structure embedded in the calcospherites beneath the predentin. However, the origin of these structures could not be determined in this experiment.