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Published on: January 12, 2017
Ultrastructural Evaluation of Newly Formed Dentine After Direct Pulp Capping With Mineral Trioxide Aggregate and
Bu'er Qi1, Yu Toida2, Rafiqul Islam2
1Department of Restorative Dentistry and Endodontology, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Hokkaido, Japan.
Aim:
To investigate the ultrastructure of the mineralised tissue after direct pulp capping (DPC) treatment using focused ion beam scanning electron microscopy (FIB-SEM) and stimulated emission depletion (STED) microscopy.
Methodology:
Eighteen male Wistar rats (36 maxillary first molars) were used in this study. Nine rats (18 M) were allocated for histological evaluation and immunofluorescence imaging (STED), six rats (12 M) for FIB-SEM observation, and three rats (6 M) served as untreated controls; control molars were used for both immunofluorescence imaging and FIB-SEM. For experimental allocation, two molars from each rat were randomly assigned to one of three groups: NEX MTA (NMTA), Dycal, or no-capping material (NC). After 4 weeks, teeth were collected for histological analysis, FIB-SEM observation and immunofluorescence imaging. Tubulin-b3 and nestin expression were examined by immunofluorescence staining and imaged with STED microscopy. The Kruskal-Wallis test followed by Dunn's multiple comparisons test and one-way ANOVA followed by Tukey's multiple comparisons test were performed to assess significant differences.
Results:
All experimental groups exhibited complete mineralised tissue formation near the exposure site. The NMTA group showed a significantly more regular odontoblastic layer than the Dycal and NC groups (p < 0.05). FIB-SEM demonstrated that NMTA induced a well-organised and continuous tubular structure, whereas Dycal and NC produced irregular, discontinuous, and poorly organised mineralised barriers. STED imaging of the NMTA group revealed strong and organised co-localization of tubulin-β3 and nestin resembling primary dentine, whereas the Dycal and NC groups showed weak, disorganised, or absent signals and lacked co-localised processes.
Conclusions:
NMTA showed superior performance compared with Dycal, consistently promoting well-organised dentine bridge formation, a continuous odontoblastic layer, and coordinated neural marker-positive processes. This indicates that NMTA more effectively supports structural formation of the pulp-dentine complex after DPC.
