Abnormalities in number of teeth are occasionally noted in clinical cases. Many theories have been proposed as regards the causes of the occurrence of supernumerary teeth, including atavism theory, mechanical tooth germ separation theory, tissue induction theory, and dental laminar morphological disturbance theory. However, none of these theories alone offers a sufficient explanation for this phenomenon. The incidence of supernumerary permanent teeth is approximately 1-3%. These are the maxillary anterior teeth, the maxillary molars, and the maxillo-mandibular premolars in terms of descending order of site of occurrence. On the other hand, incidence in the mandibular anterior tooth area, of which there have been few detailed reports, is about 0.01%, a markedly low value. In this paper, we report two rare cases of supernumerary teeth in the mandibular incisor area. We discuss their etiology and orthodontic treatment, and detail a differential diagnosis between the normal and supernumerary teeth. We found that it was difficult to establish a clear etiology and differentiation between the normal and supernumerary teeth.

A rare case of birooted primary canines is reported. A male patient aged 6 years 4 months of age presented with pain and swelling related to the upper right first primary molar. Radiographic examination revealed an incidental finding of bifurcation of the roots of all four primary canines. This represents a rare finding. The prevalence of birooted permanent canines in the Japanese population has been reported, but the prevalence of this abnormality of primary canines in other populations is unknown. This report discusses the findings in the context of the available literature. The possible aetiology, possible inferences for the developing dentition, and the need for careful assessment prior to root canal therapy or extraction are highlighted.

Dental treatment for patients with physical or mental disability is often performed under general anesthesia due to level of cooperation with treatment, type and location of treatment, time required, or number of times patient is required to attend hospital.

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We present three cases of marginal periodontitis with alveolar bone loss due to the presence of a drinking straw-like plastic tube in the periodontal pocket of a lower deciduous incisor. The plastic tube was removed using diamond tweezers in all cases. The results suggest that the symptoms of periodontitis disappear quickly after removal of the plastic tube in such cases and that the affected tooth is normally replaced with the succedaneous tooth. However, while recovering to some extent, the alveolar bone supporting the affected tooth is unlikely to return to normal. This indicates the importance of raising awareness of this problem among dentists and encouraging manufacturers to improve the design and color of such tubes if this type of accident is to be avoided. plastic tubes in the periodontal pocket over the crown of a deciduous incisor in infants and assess the prognosis for periodontitis and alveolar bone loss. Case 1A Japanese girl aged 1 year 7 months was referred to the Pediatric Dental Clinic of Tokyo Dental College Chiba Hospital by her family dentist for treatment of traumatic injury to the lower anterior region of the mandible. At the age of 1 year 4 months, she had been taken to the same dentist for injury to the bilateral deciduous lower central incisors due to a collision with a table. However, at that time, no significant symptoms were observed and she had not undergone any treatment. The dentist had, however, pointed out a morphological defect in her lower left deciduous central incisor completely unrelated to the injury. Her mother informed us that the girl had become distressed and consequently began touching the lower anterior