Histological evaluation of hard tissue formation after direct pulp capping with a fast-setting mineral trioxide aggregate (RetroMTA) in humans
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To histologically evaluate the morphology of the newly formed mineralized tissue and of the adjacent cells, in intact human teeth subjected to mechanical pulp exposure and capping with a fast-setting mineral trioxide aggregate (RetroMTA).
Materials and methods
Seven caries-free third molars from three adults were subjected to pulp exposure, direct capping with RetroMTA, and restoration with a composite resin. Seven months later, the teeth were clinically and radiographically evaluated, extracted, and subjected to histological processing and evaluation.
All teeth were clinically and radiographically inconspicuous and showed no presence of severe inflammatory reactions. Bacteria were absent in all teeth. All cases exhibited some degree of mineralized tissue in the area of exposure to varying extent. This newly formed mineralized tissue was mostly atubular and did not display the features of regular dentine in any of the cases. No cells exhibiting the features of odontoblasts or odontoblast-like cells were observed. Instead, the cells exhibited a flat or cuboidal shape, resembling fibroblasts.
When the exposed pulps were directly capped with RetroMTA, the new calcified hard tissue was not “regular dentine,” and did not seem to be the product of genuine odontoblast differentiation. These results suggest that the formation of calcified tissues after direct pulp capping with RetroMTA may be more appropriately regarded as a reparative process than as a genuine regeneration response.
This is the first histological study on humans showing that regular dentine was not regenerated when a bioactive pulp-capping material (RetroMTA) was placed over exposed pulp tissue.
KeywordsDirect pulp capping Hard tissue formation Histology Humans RetroMTA
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed and all treatments in these studies involving human participants were conducted strictly in full accordance with the ethical principles and standards of the institutional and national research committee and with the 1964 World Medical Association Declaration of Helsinki and its later amendments (version 2008) or comparable ethical standards.
All experimental protocols were independently reviewed and approved by the Local Ethics Committee of the Pomeranian Medical University, Szczecin, Poland (approval number KB–0012/27/13). This study was registered as a clinical trial (ClinicalTrials.gov Identifier: NCT03631511).
Informed written consent was obtained from all individual participants included in the study.
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