Mechanism of bioactive molecular extraction from mineralized dentin by calcium hydroxide and tricalcium silicate cement

Xue qing Huang, John Camba, Li sha Gu, Brian E. Bergeron, Domenico Ricucci, David H. Pashley, Franklin R. Tay, Li na Niu

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Abstract

Objectives: The objective of the present study was to elucidate the mechanism of bioactive molecule extraction from mineralized dentin by calcium hydroxide (Ca(OH)2) and tricalcium silicate cements (TSC). Methods and results: Transmission electron microscopy was used to provide evidence for collagen degradation in dentin surfaces covered with Ca(OH)2 or a set, hydrated TSC for 1–3 months. A one micron thick collagen degradation zone was observed on the dentin surface. Fourier transform-infrared spectroscopy was used to identify increases in apatite/collagen ratio in dentin exposed to Ca(OH)2. Using three-point bending, dentin exposed to Ca(OH)2 exhibited significant reduction in flexural strength. Using size exclusion chromatography, it was found that the small size of the hydroxyl ions derived from Ca(OH)2 enabled those ions to infiltrate the intrafibrillar compartment of mineralized collagen and degrade the collagen fibrils without affecting the apatite minerals. Using ELISA, TGF-β1 was found to be extracted from dentin covered with Ca(OH)2 for 3 months. Unlike acids that dissolve the mineral component of dentin to release bioactive molecules, alkaline materials such as Ca(OH)2 or TSC released growth factors such as TGF-β1 via collagen degradation. Significance: The bioactive molecule extraction capacities of Ca(OH)2 and TSC render these dental materials excellent for pulp capping and endodontic regeneration. These highly desirable properties, however, appear to be intertwined with the untoward effect of degradation of the collagen matrix within mineralized dentin, resulting in reduced flexural strength.

Original languageEnglish (US)
Pages (from-to)317-330
Number of pages14
JournalDental Materials
Volume34
Issue number2
DOIs
StatePublished - Feb 2018

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Keywords

  • Calcium hydroxide
  • Collagen degradation
  • Dentin
  • Flexural strength
  • Size congruity
  • Tricalcium silicate cement

ASJC Scopus subject areas

  • Materials Science(all)
  • Dentistry(all)
  • Mechanics of Materials

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