Tooth impaction is defined as any tooth that fails to erupt into a normal functional position and remains unerupted beyond the time at which it should normally erupt. Reports of impaction and eruption failure in primary teeth are relatively rare compared to permanent teeth. We report 2 rare cases where the second premolar was located on the occlusal side of the impacted mandibular second primary molar. In the first case, the succedaneous permanent tooth erupted after extraction of the primary tooth, fenestration, and traction. In the second case, the succedaneous permanent tooth erupted without fenestration or traction. Although the etiology of the tooth displacement was unknown in both cases, inhibition of the eruptive movement of the primary molar may have been associated with displacement of the succedaneous permanent premolar.
Tooth impaction is defined as any tooth that fails to erupt into a normal functional position and remains unerupted in the jaw beyond the time when it should normally erupt [
A 7-year-10-month-old female patient was referred to the Pediatric Dentistry Department of Niigata University Medical and Dental Hospital by a dentist at another clinic. The chief complaint was the eruption failure of the mandibular right second primary molar. Family and medical history were unremarkable. Intraoral examination confirmed absence of the mandibular right second primary molar. No redness or swelling of the overlying gingiva was apparent. A panoramic radiograph revealed complete impaction and mesiolingual inclination of the mandibular right second primary molar in the mandibular bone (Figure
Initial panoramic radiograph: case 1. Complete impaction and mesiolingual inclination of the mandibular right second primary molar in the mandibular bone.
Axial computed tomography image: case 1. A small calcium deposit (
The impacted mandibular right second primary molar was extracted and the calcium deposit eliminated. The patient was followed and underwent periodic radiographic examinations. The permanent mandibular right second premolar failed to erupt, although it showed slight movement distally. Therefore, when the patient was 10 years and 2 months old (2 years and 4 months after surgical treatment), fenestration was performed, followed by immediate traction of the unerupted tooth (Figure
Intraoral photographs: case 1. (a) Fenestration was performed and traction applied to the permanent second premolar at age of 10 years and 2 months. (b) The permanent mandibular right second premolar has erupted into occlusion 14 months after traction at age of 11 years and 4 months.
A 6-year-4-month-old female patient presented to Pediatric Dentistry Department of Niigata University Medical and Dental Hospital with the chief complaint of a missing mandibular right second primary molar that was pointed out during a school dental health examination. Family and medical history were unremarkable. Intraoral examination confirmed absence of the mandibular right second primary molar. A panoramic radiograph revealed complete impaction and distal inclination of the mandibular right second primary molar in the mandibular bone (Figure
Initial panoramic radiograph: case 2. Complete impaction and distal inclination of the mandibular right second primary molar in the mandibular bone.
Sagittal reconstruction computed tomography: case 2. The root apex of the impacted primary molar is extremely close to the mandibular canal and mandibular plane.
Panoramic radiographs showing growth changes of the dental germ: case 2. The formation stages of the impacted permanent tooth were approximately (a) Ri at age of 9 years and 2 months, (b) R1/2 at age of 11 years and 0 months, and (c) R3/4 at age of 12 years and 6 months. (d) At age of 16 years and 7 months, most of the tooth crown of the second permanent premolar had erupted, but the second primary molar remained impacted.
In the present cases, the most characteristic finding was the location of the second premolar on the occlusal side of the impacted mandibular second primary molar. To date, there have been relatively few reports of impaction and tooth eruption failure in primary teeth compared to permanent teeth [
Tooth eruption takes place in several stages [
The etiology of tooth impaction includes systemic and local factors such as dental germ abnormality, eruption cyst, odontoma, tooth displacement, ankylosis, gingival hyperplasia, and eruption space deficiency [
In case 1, unfortunately histopathological findings of calcium deposit were not available, since consent on the pathological examination was not obtained from the patient. However, the radiographic features showed a well-defined smooth border and a tooth-like appearance of radiopaque structure that typical images of odontoma [
On the other hand, in case 2, second primary molar was not extracted and remained impacted deep down in the mandible, because the root apex was extremely close to the mandibular canal and mandibular plane. If the follicular space of impacted teeth exceeded 5 mm a dentigerous cyst was more likely [
In cases where the permanent first molar has erupted and the eruption space for the impacted second primary molar and/or premolar is insufficient because of mesial inclination and mesial displacement of the permanent first molar, distalization of the first molar is required to procure sufficient eruption space for the deciduous molar and/or premolar. It is important that pediatric dentists detect the impaction of primary molars during primary dentition to prevent disturbing the complete and sound eruption of permanent dentition and avoid treatment complications. Delayed detection and treatment of primary tooth impaction might cause delayed eruption, impaction, and displacement of the succedaneous permanent tooth.
Impaction and eruption failure of primary teeth might be associated with a disturbance of the permanent successors. Unfortunately, in case 2, second primary molar remained impacted deep down in the mandible, but orthodontic traction or extraction might be applied if impaction was discovered early. It is important that pediatric dentists detect the impaction of primary molars during primary dentition to prevent disturbing the complete and sound eruption of permanent dentition and avoid treatment complications. Furthermore, a long-term observation is necessary until the permanent successors erupt.
The authors declare that there is no conflict of interests regarding the publication of this paper.