A critical analysis of research methods and experimental models to study dentinal microcracks

Area of Science:

• Endodontics
• Dental Materials Science
• Biomaterials

Background:

• Reports in 2009 suggested root canal preparation causes dentinal microcracks, potentially leading to vertical root fractures (VRFs).
• This presumed link lacked scientific evidence, and studies on extracted teeth yielded inconsistent results.
• The high incidence of reported microcracks contrasted sharply with clinical VRF rates, questioning study reliability.

Purpose of the Study:

• To review scientific advancements in understanding root dentinal microcracks.
• To clarify the relationship between micro-computed tomography (micro-CT), experimental models, and dentinal defects.
• To re-evaluate the role of dentinal microcracks in the etiology of VRFs.

Main Methods:

• Narrative review of scientific literature.
• Analysis of studies utilizing micro-computed tomography (micro-CT).
• Evaluation of experimental models, including close-to-mouth and in-situ approaches with fresh cadavers.

Main Results:

• Micro-CT studies revealed pre-existing defects in extracted teeth, refuting a causal link between root canal preparation and microcracks.
• In-situ studies on sound, non-extracted teeth found no evidence of microcracks.
• Dentinal microcracks in extracted teeth are artifacts of dehydration and storage, not a natural phenomenon.

Conclusions:

• Dentinal microcracks observed in extracted teeth are laboratory-induced artifacts.
• These microcracks are not the initiating factor for vertical root fractures (VRFs).
• Recent scientific findings challenge the clinical relevance of laboratory-derived outcomes regarding dentinal microcracks and VRFs.