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AimTo evaluate the influence of ultraconservative endodontic cavities (UEC) on canal shaping and filling ability, cleaning of the pulp chamber, time required to perform root canal treatment and fracture resistance of 2‐rooted maxillary premolars in comparison with traditional endodontic access cavities (TEC) in extracted teeth placed in a phantom head to simulate clinical conditions.MethodologyTwenty extracted intact 2‐rooted maxillary premolars were scanned in a micro‐computed tomographic device, matched based on similar anatomical features of the canals and assigned to UEC or TEC groups (n = 10). Then, teeth were mounted on a mannequin head and their pulp chamber accessed. After canal preparation, filling and cavity restoration, the time required to perform root canal treatment was recorded and the specimens were loaded to fracture in a universal testing machine. The maximum load at fracture was recorded. The sample was scanned after root canal instrumentation, filling and restoration procedures. Untouched canal areas, accumulation of hard‐tissue debris (AHTD), voids in root fillings and cleaning of the pulp chamber were analysed. Data were analysed statistically using Shapiro–Wilk and Student's t‐tests with a significance level of 5%.ResultsThe percentage of untouched canal area did not differ significantly between UEC and TEC groups (P > 0.05). However, UECs were associated with a greater percentage of AHTD after canal preparation (P < 0.05). No differences were observed in terms of voids in root fillings between the groups (P > 0.05). Nonetheless, UEC had a greater percentage of root filling remnants in the pulp chamber after cleaning procedures (P < 0.05). The time required to perform root canal treatment was significantly longer in the UEC group (P < 0.05). There was no difference regarding the mean load at fracture between the groups (P > 0.05). Unrestorable fractures were observed in all specimens of both groups.ConclusionsThere was no true benefit associated with ultraconservative endodontic cavities. UEC resulted in more AHTD remaining inside the root canals. UEC did not influence the quality of root fillings; however, UEC made the cleaning procedure of the pulp chamber more difficult, thus increasing the total time required to perform root canal treatment. Moreover, UEC were not associated with an increase in fracture resistance of root filled 2‐rooted maxillary premolars.

The preparation techniques resulted in the same level of accumulated hard-tissue debris. Compared to the other tested systems, BioRace was associated with more untouched canal walls and Reciproc produced the greatest amount of removed dentine. Although it touched more of the root canal walls, the SAF system removed less dentine, whereas TRUShape had intermediate results for these same parameters. None of the systems tested were able to provide optimal shaping ability in oval-shaped canals.