The purpose of this investigation was to study the prevalence of C‐shaped roots, root canal orifices, and root canals in the mandibular second molars of a Chinese population. A total of 581 second mandibular molars were collected in Hong Kong and Taiwan. The teeth were demineralized and placed in methyl salicylate to induce transparency. The pulp chamber floor was examined to ascertain the number of root canal orifices. Chinese ink was then injected into the root canal system to demonstrate the root canal anatomy. The mandibular second molars had separate roots in 66.4%, cone‐shaped roots in 2.1% and C‐shaped roots in 31.5%. The C‐shaped roots had C‐shaped canal orifices in 68.3% (21.5% of whole material). True C‐shaped root canals were observed in 65.8% of the teeth with C‐shaped orifices and in 13.9% of the whole material. Separate root canals were seen in 34.2% of the teeth with C‐shaped orifices. Separate canal orifices were found in 31.7% of the C‐shaped roots and 7.4% of these roots had true C‐shaped canals. In the whole material 0.9% of the roots with individual canal orifices had C‐shaped canals. In conclusion, C‐shaped root canals were common in mandibular second molars in the Chinese subjects studied. The C‐shaped root canals were often, but not always recognized because of a C‐shaped canal orifice.

The purpose of this investigation was to study the prevalence of fused roots, C‐shaped roots, C‐shaped root canal orifices and C‐shaped root canals in the maxillary molars of a Chinese population. A total of 305 first molars and 309 second molars were collected in Taiwan. The teeth were demineralized and placed in methyl salicylate to make them transparent. Root fusion was examined and the pulp chamber floor was checked for C‐shaped orifices. Chinese ink was then injected into the root canal system to demonstrate possible C‐shaped canals. The maxillary first molars had the palatal root fused with the mesiobuccal root in 0.3% of the cases, and with the distobuccal root in 2.0%. Teeth with C‐shaped roots existed in only 0.3% of maxillary first molars, while 6.2% of the maxillary first molars and 40.1% of the maxillary second molars had fused roots. The maxillary second molars had the palatal root fused with the mesiobuccal root in 18.1% and with the distobuccal root in 2.6%; the palatal root was fused with the mesiobuccal and distobuccal root in 8.1% of the material. The maxillary second molars had a C‐shaped root in 4.5% and C‐shaped root canal orifices with C‐shaped root canals in 4.9% of the cases. Fused roots or incompletely separated roots are common in the maxillary second molars amongst Chinese people, while C‐shaped roots and root canals in maxillary molars are not frequently seen.

A case report is presented in which continuing root formation occurred in an immature mandibular second premolar after calcium hydroxide apexification treatment. An apical hard tissue barrier was accompanied by a separate disto-apically growing root 18 months posttreatment. Histologic evaluation of the root revealed immature hard tissue mixed with calcium hydroxide, connective tissue and bone, apically in the original root canal. In the separate new formed part of the root, pulp tissue, odontoblasts, predentin, cementum and an apical foreman could be identified.

It was the purpose of this investigation to study the suitability of a controlled release delivery system for endodontic medicaments, making it possible to maintain a constant concentration of a medicament in the root canal for an extended period of time. The delivery system comprised an inner core matrix containing the medicament surrounded by a polymeric membrane allowing a controlled release of the active ingredient. Controlled release preparations containing formocresol, camphorated paramonochlorphenol, Creation, and a quaternary ammonium compound (dodecyl‐dimethyl‐benzylammonium chloride) were manufactured and applied to root canals of dogs' teeth. In control experiments the same medicaments were applied to root canals by means of cotton pellets. After 1, 3, 7 and 45 clays the pieces of polymeric materials and the cotton pellets were removed from the root canals and tested for antibacterial effect. After 1 d in the root canal none of the medicaments on cotton pellets had an effect. Of the controlled release preparations, the quaternary ammonium compound had a fairly constant effect on bacterial growth for the duration of the experiment (45 d). The results suggested that the idea of improving the effect of endodontic medicaments by means of controlled release delivery systems is valid, and may gain clinical importance in the future.

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