The maxillary third molars, compared to the mandibular third molars, have a wider range of clinical applications as well as extraction options. In this study, we investigated the time of formation, morphological evaluation, and location of maxillary third molars using panoramic radiographs and CT images. We also studied the number of third molars in each age group and patients' awareness of those teeth. We found that about 90% of patients with one or more third molars had one or more maxillary third molars. The presence of maxillary third molars decreased with age, with 69.6% of patients in their 40s and 33.5% in their 70s. The percentage of patients who answered that they intentionally preserved their maxillary third molars was 5.2%. We also found that root formation of maxillary third molars progressed mainly from 19 to 21 years of age and was completed around 24 years of age. The eruption of the third molars progressed with the root formation. However, only 3.1% of the third molars reached the occlusal plane although the root formation was completed. CT images of the maxillary third molars showed that 25.7% had a mesial inclined tooth axis and 23.8% had a distal inclined tooth axis after the completion of root formation. Of these, 2.6% had a large medial inclination angle that could cause root resorption of the second molar. Regarding the number of cusps of the third molars, 31.2% had four cusps, 46.2% had three cusps, and 22.6% had another number of cusps. In conclusion, panoramic radiographs and three-dimensional data can be used to make more accurate clinical diagnoses after understanding the characteristics of maxillary third molars.

Recently, composite resin with self-etching systems have become widely accepted and used in pediatric dentistry. The aim of this clinical study was to evaluate the clinical performance of composite resin with S-PRG filler (Beautifil Kid's resin), which has the ability to release and recharge fluoride. In this study, two types of flowable resin composites with different flowability (Beautifil Kid's Low-Flow type and Zero-Flow) and one type of paste resin composite (Beautifil Kid's Paste) were used. In total, 249 restorations were performed in anterior teeth and primary molars using the three different restorative materials with self-etching systems. Restorations were assessed in eight categories: defluxion, fracture, secondary caries, blow-hole, marginal integrity, marginal discoloration, color change, and attrition. Assessments were done after six months and after one year. There were no significant differences in clinical performance between the three types of Beautifil Kid's resin in all parameters. The clinical performance by cavity forms showed little difference between Class III, IV and V in the anterior primary teeth, but the clinical performance in the primary molars was lower in Class II than in Class I and V.

Clinically, these data demonstrate that the three types of Beautifil Kid's resin are useful as restoration materials for caries of deciduous teeth.

Cases of abnormal eruption of permanent teeth are occasionally encountered in pediatric clinical dentistry. In many cases, eruption can be promoted by appropriate and timely interventions. However, in some cases, treatment is difficult and/or eruption cannot be achieved. This study assessed the time courses of treatment in two groups of subjects, and the pre-treatment test findings were compared between them.

Each group included four subjects and the groups were defined as follows : the “favorable group,” in which guided eruption was possible using the standard method, and the “unfavorable/refractory group,” in which ankylosis was suspected and traction was difficult or impossible. The study findings were as follows :

1. Ankylosis is suspected if preoperative radiography shows an unclear image of the periodontal ligament of the diseased tooth. Three-dimensional examination by CBCT is effective in such cases.

2. Despite the absence of obstacles to clear eruption, ankylosis is suspected if a part of the tooth crown is exposed at the gingival margin, and if tooth eruption has stopped.

3. Using detailed interviews, patients' dental history is obtained to determine whether they had experienced conditions that could have damaged the periodontal ligament of the diseased tooth, such as injury to the diseased tooth or injury to or extraction of the supernumerary teeth from the neighboring region. If deemed appropriate, consideration is given to whether these factors could complicate guided eruption.

4. The generally known characteristics of ankylosed teeth―change in percussion sound and loss of physiologic mobility―are difficult to detect at the early stages of ankylosis.

If guided eruption is expected to be difficult, it is crucial to select the optimal treatment method and also assess the invasiveness and effectiveness sufficiently. Furthermore, clinically, it is critical to provide full explanations to pediatric patients and their guardians about how treatment results cannot be reliably expected, and about the subsequent approaches that are necessary; this information should be shared with them as appropriate.

Gingival fibromatosis (GF) is a rare disease characterized by gingival hyperplasia that occurs in early childhood and progresses slowly. We report a case of canine impaction and embedded supernumerary teeth occurring bilaterally in the maxilla with GF.

The patient was a boy of six years and six months with delayed eruption of his permanent teeth. As oral findings, the crowns of the maxillary teeth were slightly erupted from the gingiva, which was enlarged remarkably. Because of similar oral findings in his brother, this GF was diagnosed as a hereditary disease.

Bilateral canine impaction and embedded supernumerary teeth in the maxilla were confirmed by panoramic radiography at age eight years and eight months. GF was treated by gingivectomy under general anesthesia and the impacted canines by fenestration at age nine years and eight months. The embedded supernumerary teeth were extracted under general anesthesia when the boy was ten years and six months. Because of periodic oral management that has contributed to good plaque control, gingival hyperplasia has not recurred after treatment.

In the future, the patient plans to undergo orthodontic treatment. Therefore, long-term observation and continued oral hygiene management are important to prevent the recurrence of GF.

Dentigerous cysts are developmental cysts that rarely occur in the anterior teeth of the mandible and are rarely reported in children younger than 5 years old. Here, we report a rare case of a dentigerous cyst caused by the left central incisor of the mandible with malposition of the adjacent tooth germs in a 3-year-old child.

A 3-year 10-month-old boy presented to our clinic with a chief complaint of swollen gingiva in the region of the mandibular anterior teeth. Upon examination, a bulge was observed in the oral cavity extending from the lingual gingiva of the anterior mandibular teeth to the floor of the mouth; the bulge had a parchment-like texture. Computed tomography (CT) findings revealed a transmission image of 17.8 × 12.9 × 14.7 mm size in the anterior teeth of the mandible, with clear boundaries and labiolingual protrusion of the cortical bone with discontinuity of the cortical bone in some parts. The transmission image contained the mandibular left central incisor tooth germ, which was compressed by the lesion and largely displaced and twisted centrifugally. After extraction of the mandibular left deciduous central incisor and deciduous lateral incisor under general anesthesia, the lesion including the mandibular left central incisor tooth germ was removed. A histopathological diagnosis of dentigerous cyst with inflammation was considered. Micro CT findings of the mandibular left deciduous central incisor indicated that the restoration found at the incisal margin reached the pulp, and an absorption fossa extending nearly half of the apical side was detected on the lingual side of the root. We believe that the dentigerous cyst was formed at an early stage and developed gradually, the inflammation from the dental pulp spread to the cyst through the apex, and the exudate rapidly entered the cyst and expanded. One year following the operation, no recurrence of the cyst was observed, and the position of the mandibular left lateral incisor tooth germ moved towards the central position with new bone formation; thus, the patient demonstrated a favorable clinical course.