Influence of different irrigation protocols on microhardness and flexural strength values of young and aged crown dentin

Gerodontology. 2020 Mar;37(1):53-58. doi: 10.1111/ger.12444. Epub 2019 Nov 19.


Objective: To investigate the effect of different irrigation protocols on microhardness (MH) and flexural strength (FS) values of young and aged crown dentin.

Background: In addition to ageing, root canal irrigation might also affect the mechanical properties of coronal dentin walls.

Materials and methods: One hundred and twenty dentin bars (2 mm × 2 mm × 8 mm) were obtained from the crowns of extracted, non-caries, human molars of young and older patients (n = 60 bars; average patient ages: 16.7 and 65.4, respectively). Subgroups were formed as follows: 2.5%NaOCl(sodium hypochlorite)+5%EDTA(ethylenediaminetetraacetic acid), 2.5%NaOCl + 15%EDTA, 2.5%NaOCl, 5%EDTA, 15%EDTA and Saline. NaOCl and saline were used for 20 minutes and EDTA solutions for 1 minute. MH values of each sample were measured before and after the irrigation protocols. The same samples were also submitted for FS analysis. The data were statistically analysed.

Results: Young samples had lower MH values at pre- and post-treatment compared to aged samples (P < .05). A significant decrease was observed in MH values of aged samples exposed to 2.5%NaOCl and both NaOCl + EDTA combinations (P < .05). FS values of the young saline-treated group were statistically higher than aged ones (P < .05). Both NaOCl + EDTA combinations caused a significant decrease in FS values of young samples compared to saline (P < .05).

Conclusion: Ageing has a significant effect on the MH and FS values of crown dentin samples. 5% EDTA solutions revealed similar results to 15%EDTA regarding MH and FS values of crown dentin in both age groups. The NaOCl + EDTA combination had a prominent effect than EDTA alone, on MH values of young-, and FS values of aged dentin samples.

Keywords: age; biomechanics; chelating agents; endodontics; root canal irrigation.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Crowns
  • Dental Pulp Cavity*
  • Dentin
  • Flexural Strength
  • Humans
  • Middle Aged
  • Root Canal Irrigants*
  • Sodium Hypochlorite
  • Young Adult


  • Root Canal Irrigants
  • Sodium Hypochlorite