Minimal invasive endodontics: A comprehensive review on access preparation and mechanical instrumentation strategies - Part I: access cavity design
Keywords:
conservative access cavity, minimally invasive endodontics, ninja access, truss access, ultra-conservative access cavityAbstract
Vertical root fracture (VRF) is a common contributing factor leading to extraction of endodontically treated teeth. Concerns regarding cracks and VRFs have therefore driven the development of minimally invasive endodontics (MIE), which initially focused on access cavity designs aimed at preserving coronal tooth structure and pericervical dentin (PCD) to enhance long term tooth survival.
Evidence from in vitro studies suggests that, from a mechanical perspective, MIE access cavities preserve more coronal tooth structure and upper PCD compared with traditional endodontic cavities (TEC), and are generally associated with lower cervical stress concentration. However, findings on fracture resistance and canal transportation are inconsistent, particularly in molars and structurally compromised teeth, where marginal ridge loss remains a dominant determinant of fracture risk regardless of access design.
From a biological perspective, evidence regarding cleaning efficiency remains inconclusive. Most studies report no significant differences between MIE and TEC in terms of remaining hard tissue debris or residual pulp tissue within the root canal system, whereas results concerning uninstrumented areas are conflicting. Importantly, increased access conservatism is associated with a higher risk of missed canals, especially in teeth with complex anatomy such as the second mesiobuccal (MB2) canal, likely due to reduced visibility. In addition, ultraconservative access designs are also consistently associated with greater root filling remnants in the pulp chamber, which may compromise coronal bonding and esthetics outcome.
Overall, while MIE access designs offer mechanical advantages through dentin preservation, their biological benefits and effects on fracture resistance remain uncertain. Access cavity design should therefore be case-dependent, considering residual tooth structure, anatomical complexity, operator experience, and the availability of adjunctive technologies. Further well-designed clinical studies are needed to clarify the long-term implications of MIE approaches.
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