[Study on thermal pulp testing of immature permanent teeth].

The duration of reaction to cool stimulation was investigated in 185 normal maxillary right and left central and lateral incisors from 55 pediatric patients aged from 6 to 15 years, who were brought to the Department of Pedodontics of Nippon Dental University Hospital, and from 9 students aged from 19 to 20 years in the School of Dental Technology and Hygiene affiliated with Nippon Dental University by using Dichloro-Difluoro-Methane coolants [PULPER (G-C Dental Industrial Corp.) and PULPOFLUORANE (Septodont Co.)] in order to determine the efficacy of thermal pulp testing for mature and immature permanent teeth. The results obtained are as follows: 1) The mean duration of reaction to cool stimulation according to the type of teeth was 0.93 sec for the maxillary left lateral incisors, 0.91 sec for the maxillary left central incisors, 0.88 sec for the maxillary right central incisors and 0.95 sec for the maxillary right lateral incisors, showing no statistically significant difference in the duration between the tooth types. 2) The duration of reaction to cool stimulation according to age was shortened with aging except for the 6-year-old patients. 3) The patients were divided into those 10 years old or younger and those older than 10 years because the tooth roots of the maxillary anterior teeth are developed at 10 years of age. The mean duration of reaction to cool stimulation was 1.02 sec in the group with immature permanent teeth, which consisted of patients aged 10 years or younger, while it was 0.82 sec in the group with mature permanent teeth, which consisted of patients aged 11 years or older.(ABSTRACT TRUNCATED AT 250 WORDS)

[Experimental study on the effect of replantation of immature permanent teeth on the periapical and periodontal tissues].

Replantation and semi-rigid fixation were performed on canine immature permanent teeth, and one week after replantation the teeth were treated by root filling with calcium hydroxide. The root apex and periodontium of the teeth with replantation were examined for changes regularly during the experiment by microradiographic, fluorescence microscopic, polarizing microscopic and X-ray observation of undecalcified horizontal continual ground sections. The results obtained were as follows: 1) Immediately after replantation, root formation was observed, but its formation was found to cease at a relatively early time. No site of the root showed any inflammatory resorption. 2) The dentine of the teeth with replantation was narrow, and the whole tooth substance showed discoloration due to penetration of calcium hydroxide. 3) the periodontal space surrounding the teeth with replantation was decreased daily by new bone actively formed from the alveolar bone proper and by a thin cementum layer added on the periodontal surface. This change occurred from one week after replantation. 4) The width of the periodontal space of the teeth with replantation, which had been wider than that of a control tooth, was increased and decreased daily at the cervix and root apex and the central part of the root, respectively. 5) Collagen fibers of the periodontal membrane were present in the periodontal space of the teeth with replantation, together with regeneration of the periodontal membrane that had been cut by extraction. 6) There were no changes due to replantation in the two teeth adjacent to the tooth with replantation or the lateral jaw.