The ratio of the parameters of microhardness and elastic plastic deformation of natural teeth as a starting point for experimental studies on minimizing the weakening of the root structure during endodontic treatment

AIM. Evaluation of the parameters of microhardness and elastoplastic deformation of the dentine of the roots of untreated teeth for further use in experimental studies devoted to the search for protocols that minimally weaken the root structures during endodontic treatment.

MATERIALS AND METHODS. 14 premolars (9 upper and 5 lower) with a straight root, removed according to orthodontic indications, were selected for the study. The root of each tooth was divided into three parts (oral, middle, and apical), then the parameters of microhardness and elastic plastic deformation were determined for each of the parts. Measurements were carried out in three areas: at the channel, in the middle part of the sample and in the outer part of the sample.

RESULTS. Microhardness parameters: the middle segment has the highest microhardness values for all thirds of the root: in the mouth – 95.02 (91.97–99.31) HV, 1026.05 (993.03–1072.37) (MPa), average – 97.34 ± 12.45 HV, 1051.11 ± 134.47 (MPa) and apical-100.08 ± 12.35 HV, 1080.69 ± 133.33 (MPa). Parameters of elastoplastic deformation: the middle segment has the highest modulus of elasticity in all thirds of the root, the highest index is in the apical third of the root – 24.25 (24.01–25.30) (MPa), the lowest is in the middle third (21.87 ± 1.55 MPa); the highest relative work of elastic deformation is in the middle third of the root, the lowest is in the mouth a third. At the same time, it increases from the mouth to the middle third, and decreases from the middle third to the apical third. The greatest relative work of plastic deformation is in the estuarine third, the smallest is in the middle third, while it decreases from the estuarine to the middle third, and increases from the middle third to the apical third.

CONCLUSIONS. The apical third of the root is the hardest, while the middle third is the most elastic. When considering the wall in a cross-section, the middle is the hardest, while the segments at the channel and at the outer edge are less hard and more elastic.  

1. Zagorskiy V.A., Makeeva I.M., Zagorskiy V.V. Strength properties of the hard tissue of teeth. Part II. Russian Journal of Dentistry. 2014;(1):9–12. (In Russ.) Available at: https://rjdentistry.com/1728-2802/article/view/39219 (accessed: 27.03.2025).

2. Massarsky I.G., Abolmasov N.N., Adayeva I.A., Kovalkov V.K., Solovyev A.A., Statenina E.A. Clinical and laboratory substantiation of the method used to prepare pulpless teeth for prosthetics. Vestnik Vitebskogo Gosudarstvennogo Meditsinskogo Universiteta. 2015;14(5):87–99. (In Russ.) Available at: https://vestnik.vsmu.by/archive/2015/14-5/2015-5-87-99.html (accessed: 27.03.2025).

3. Geogi C.C., Dubey S., Singh P., Rajkumar B., Samant P.S., Rawat A. A Comparative evaluation of the effect of different endodontic irrigating solutions on microhardness of root canal dentin: An in vitro study. J Dent. 2024;25(3):236–242. https://doi.org/10.30476/dentjods.2023.98298

4. Patil C.R., Uppin V. Effect of endodontic irrigating solutions on the microhardness and roughness of root canal dentin: an in vitro study. Indian J Dent Res. 2011;22(1):22–27. https://doi.org/10.4103/0970-9290.79969

5. Reutov A.S., Skvortsova E.N., Efremova A.V., Frolova K.E., Konovalova E.V. Dentistry: Errors and complications in endodontics. Modern Science: Actual Problems of Theory & Practice. Series: Natural and Technical Sciences. 2023;9(2):155–159. (In Russ.) Available at: http://www.nauteh-journal.ru/files/7c4f0dbd-8c8f-41f8-93b0-8f1207e4331c (accessed: 27.03.2025).

6. Patel S., Bhuva B., Bose R. Present status and future directions: vertical root fractures in root filled teeth. Int Endod J. 2022;55(S3):804–826. https://doi.org/10.1111/iej.13737

7. Serdar Eymirli P., Eymirli A., Uzunoğlu Özyürek E. The effect of intracanal medication variations on microhardness of simulated immature root dentin. Aust Endod J. 2021;47(3):616–623. https://doi.org/10.1111/aej.12532

8. Sarkisyan N.G., Kataeva N.N., Khokhryakova D.A. Medicinal treatment of root canals in endodontics: problems of using modern agents. I.P. Pavlov Russian Medical Biological Herald. 2025;33(1):123–132. https://doi.org/10.17816/PAVLOVJ568734

9. Saghiri M.A., Rahmani B., Conte M., Nath D., Peters O., Morgano S. Diabetes mellitus affects the microhardness of root dentine: An in-vitro study. Eur Endod J. 2022;7(2):122–128. https://doi.org/10.14744/eej.2022.37029

10. Elika V., Kunam D., Anumula L., Chinni S.K., Govula K. Comparative evaluation of Chloroquick with Triphala, sodium hypochlorite, and ethylenediaminetetraacetic acid on the microhardness of root canal dentin: An in vitro study. J Clin Transl Res. 2021;7(1):72–76.

11. El-Banna A., Elmesellawy M.Y., Elsayed M.A. Flexural strength and microhardness of human radicular dentin sticks after conditioning with different endodontic chelating agents. J Conserv Dent. 2023;26(3):344–348. https://doi.org/10.4103/jcd.jcd_173_23

12. Zagorskiy V.A., Makeeva I.M., Zagorskiy V.V. Functioning of the hard tissues of the tooth. Part III. Russian Journal of Dentistry. 2014;(1):12–15. (In Russ.) Available at: https://rjdentistry.com/1728-2802/article/view/39222 (accessed: 27.03.2025).

13. Schneider S.W. A comparison of canal preparations in straight and curved root canals. Oral Surg Oral Med Oral Pathol. 1971;32(2):271–275. https://doi.org/10.1016/0030-4220(71)90230-1

14. Vertucci F.J. Root canal morphology and its relationship to endodontic procedures. Endodontic Topics. 2005;10(1):3–29. https://doi.org/10.1111/j.1601-1546.2005.00129.x

15. Naeem M.M., Sarwar H., Nisar A., Ahmed S., Shabbir J., Khurshid Z., Palma P.J. Effect of propolis on root dentine microhardness when used as an intracanal medicament: An in vitro study. J Funct Biomater. 2023;14(3):144. https://doi.org/10.3390/jfb14030144

16. Amonkar A.D., Dhaded N.S., Doddwad P.K., Patil A.C., Hugar S.M., Bhandi S. et al. Evaluation of the effect of long-term use of three intracanal medicaments on the radicular dentin microhardness and fracture resistance: An in vitro study. Acta Stomatol Croat. 2021;55(3):291–301. https://doi.org/10.15644/asc55/3/6

17. Byakova S.F., Novozhilova N.E., Makeeva I.M., Grachev V.I., Kasatkina I.V. The accuracy of CBCT for the detection and diagnosis of vertical root fractures in vivo. Int Endod J. 2019;52(9):1255–1263. https://doi.org/10.1111/iej.13114

18. Aslantas E.E., Buzoglu H.D., Altundasar E., Serper A. Effect of EDTA, sodium hypochlorite, and chlorhexidine gluconate with or without surface modifiers on dentin microhardness. J Endod. 2014;40(6):876–879. https://doi.org/10.1016/j.joen.2013.10.041

19. Keine K.C., Kuga M.C., Coaguila-Llerena H., Palma-Dibb R.G., Faria G. Peracetic acid as a single endodontic irrigant: effects on microhardness, roughness and erosion of root canal dentin. Microsc Res Tech. 2020;83(4):375–380. https://doi.org/10.1002/jemt.23424

20. Makeeva I.M., Biakova S.F., Kazakov Ia.V., Novozhilova N.E. The resistance of teeth to vertical root fractures after mechanical preparation and irrigation of root canal (pilot study). Stomatology. 2016;95(1):14–17. (In Russ.) https://doi.org/10.17116/stomat201695114-17

21. Durmus B., Hale A.A., Oguz E., Sema B. The effect of different irrigation protocols on elastic modulus of dentine and biomechanics of single-rooted premolar tooth: A nano-indentation and finite element analysis study. Niger J Clin Pract. 2019;22(1):101–107. https://doi.org/10.4103/njcp.njcp_85_18

22. Cuy J.L., Mann A.B., Livi K.J., Teaford M.F., Weihs T.P. Nanoindentation mapping of the mechanical properties of human molar tooth enamel. Arch Oral Biol. 2002;47(4):281–291. https://doi.org/10.1016/s0003-9969(02)00006-7

23. Balooch G., Marshall G.W., Marshall S.J., Warren O.L., Asif S.A., Balooch M. Evaluation of a new modulus mapping technique to investigate microstructural features of human teeth. J Biomech. 2004;37(8):1223–1232. https://doi.org/10.1016/j.jbiomech.2003.12.012

24. Wang Z., Wang K., Xu W., Gong X., Zhang F. Mapping the mechanical gradient of human dentin-enameljunction at different intratooth locations. Dent Mater. 2018;34(3):376–388. https://doi.org/10.1016/j.dental.2017.11.001

25. Sahebi S., Mofidi H., Abbaszadegan A., Gholami A., Eskandari F. The effect of nanobased irrigants on the root canal dentin microhardness: an ex-vivo study. BMC Oral Health. 2023;23(1):581. https://doi.org/10.1186/s12903-023-03298-z

26. Patri G., Lath H., Jena D., Banka A., Bajoria A.A. Effect of herbal intracanal medicaments on microhardness of root dentin: An in vitro study. Cureus. 2024;16(6):e63165. https://doi.org/10.7759/cureus.63165

27. Jíra A., Němeček J. Nanoindentation of human tooth dentin. Key Engineering Materials. 2014;606:133–136. https://doi.org/10.4028/www.scientific.net/KEM.606.133

28. Grudyanov A.I., Makeeva M.K., Pyatigorskaya N.V. Modern concepts of etiology, pathogenesis and treatment approaches to endo-perio lesions. Annals of the Russian Academy of Medical Sciences. 2013;68(8):34–36. (In Russ.) https://doi.org/10.15690/vramn.v68i8.721

29. Tsimbalistov A.V., Surdina E.D., Shtorina G.B. The condition of the pulp in intact teeth with severe generalized periodontitis. Actual Problems in Dentistry. 2007;(4):5–9. (In Russ.)