Conservative endodontic access (Ninja access)
Conservative endodontic access or ninja access is basically an access to complete a root canal that is very small. My bias is that most root canals we see fail do so from infection and likely ineffective cleansing. To limit ones ability to effectively clean out the inside to reduce the risk of fracture is something only the those with exemption skill should even bother attempting.
Ninja access research
The conservative endodontic cavity or access, basically the ninja access, improves fracture strength in lower molars at the expense of instrumentation efficiency. Krishan JOE 2014 In maxillary molars the conservative endodontic access appears to have no benefit or some depending on the study. Moore JOE 2016 Zhang JOE 2019 Worse yet it results in more transportation and less canals found with no gain in fracture resistance. Rover JOE 2017
The contracted endodontic cavity results in greater apical transportation. In general the ninja access results in less preservation of the original canal anatomy. Alovisi JOE 2018
It appears the roots and any isthmus are just as clean in the ninja access as traditional but the chamber is not. Neelakantan JOE 2018
The cervical dentin is what is important not the occlusal enamel and dentin as you can see from this stress concentration image under loading. The conservative endodontic access cavity has no impact on fracture resistance in comparison to a traditional access. Sabeti 2018 JOE
Truss endodontic access cavity
This is similar to above ideas and shows similar results, which means does not appear to be helpful. Corsentino JOE 2018 found the truss did not increase fracture resistance of the tooth. Truss did help increase fracture resistance in MOD cut teeth Abou-Elnaga JOE 2019
Other synonyms in the literature
As with many techniques there are multiple authors publishing research with different names. Many are attempting to get nomenclature that they like for the technique. Ninja access is slang and conservative endodontic cavity (CEC) or conservative endodontic access are the main terms seen. However, orifice-directed dentin conservation access is another term that is seen in the research.