Enamel pearls in permanent dentition: case report and micro-CT evaluation

Abstract

Objectives: To investigate the frequency, position, number and morphology of enamel pearls (EPs) using micro-CT (µCT) and to report a case of an EP mimicking an endodontic-periodontic lesion.

Methods: Cone beam CT (CBCT) was performed in a patient to evaluate a radio-opaque nodule observed on the left maxillary first molar during the radiographic examination. Additionally, 23 EPs were evaluated regarding frequency, position, number and morphology by means of µCT. The results were statistically compared using the Student's t-test for independent samples.

Results: 1 pearl was presented in 13 specimens, while 5 specimens presented 2 pearls. The most frequent location of the EPs was the furcation between the disto-buccal and the palatal roots of the maxillary molars. Overall, the mean major diameter, volume and surface area were 1.98 ± 0.85 mm, 1.76 ± 1.36 mm³ and 11.40 ± 7.59 mm², respectively, with no statistical difference between maxillary second and third molars (p > 0.05). In the case report, CBCT revealed an EP between the disto-buccal and the palatal roots of the maxillary first left molar associated with advanced localized periodontitis. The tooth was referred for extraction.

Conclusions: EPs, located generally in the furcation area, were observed in 0.74% of the sample. The majority was an enamel-dentin pearl type and no difference was found in maxillary second and third molars regarding diameter, volume and surface area of the pearls. In this report, the EP mimicked an endodontic-periodontic lesion and was a secondary aetiological factor in the periodontal breakdown.

Figure 1

(a) Swelling on buccal gingival of left maxillary first molar; (b) occlusal view of the maxillary left first molar; (c) periapical radiograph showing a narrow pulp chamber, deep composite resin restorations and severe bone loss, mainly in the distal aspect of the disto-buccal root of the maxillary left first molar. Gutta-percha cone tracing the sinus tract revealed the presence of a small, round radio-opaque structure in the distal aspect of the root; (d–f) coronal, sagittal and axial views, respectively of the maxillary left first molar obtained in the cone beam CT examination showing an enamel pearl (arrow) between the disto-buccal and the palatal roots; (g) three-dimensional volumetric view of the hard tissues of the maxillary left region showing the presence of an enamel pearl in the distal aspect of the first molar (arrow). MB, mesio-buccal; DB, disto-buccal; P, palatal

Figure 2

Three-dimensional reconstruction of 18 molar teeth showing the location of 23 enamel pearls (EPs). Specimen 4 was the only one presenting a true EP (black arrow). DB, disto-buccal; DP, disto-palatal; MB, mesio-buccal; ML, mesio-lingual; MP, mesio-palatal; P, palatal

Figure 3

Morphological features of the enamel pearls (EPs). (a–e) Five specimens showed two EPs located on the root surface; (f–i) four specimens with a cervical enamel projection connecting the pearl to the crown; (j–n) relationship between the EPs and the root canal system of five maxillary molars

Figure 4

Morphological features of the enamel pearls (EPs). (a) reconstruction of three-dimensional (3D) Specimen 4 showing a true EP (consisting entirely of enamel) between the palatal and the mesiobuccal roots; (b) axial view of the true EP; (c–e) Partial view of a 3D reconstruction of a mandibular second molar showing the presence of an EP in the mesial aspect of the mesial root containing a core of tubular dentine (enamel–dentine pearl); (f) axial view of the EP presenting a core of dentine; (g) internal and external aspects of the enamel–dentin pearl