{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T12:35:12Z","timestamp":1787661312855,"version":"build-2736575974"},"reference-count":51,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2025,10,22]],"date-time":"2025-10-22T00:00:00Z","timestamp":1761091200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"European Union-NextGenerationEU","award":["BG-RRP-2.004-0004-C01"],"award-info":[{"award-number":["BG-RRP-2.004-0004-C01"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Background: This study aimed to evaluate the impact of varying durations of ultrasonic condensation on the formation of internal and external voids and the microhardness of apical plugs created with premixed bioceramic putty Well-RootTM PT in standardized 3D-printed immature permanent teeth using micro-CT imaging and Vickers microhardness testing. Methods: Forty-eight 3D-printed upper incisors with simulated open apices (2 mm canal diameter) were divided into four groups (n = 12 each) based on apical plug condensation technique as follows: Group 1 (control, manual condensation), Group 2 (3-s Ultrasonic at 25 kHz), Group 3 (9-s Ultrasonic at 25 kHz), and Group 4 (15-s Ultrasonic at 25 kHz). Well-RootTM PT was used to form 5 mm apical plugs under a microscope. Samples were stored at 37 \u00b0C and 100% humidity for one week. Micro-CT imaging was used to quantify internal, external, and total void volumes (% of total material volume), while microhardness was measured using a Vickers tester (1 kgf load, 10 s) on polished apical plug sections. Statistical analysis was performed using ANOVA and Tukey post hoc tests. Results: Group 4 (15-s Ultrasonic) exhibited significantly higher external and total void volumes compared to Groups 1\u20133 (p &lt; 0.001), with no significant differences in internal voids across groups (p &gt; 0.05). Microhardness was highest in Group 1 (mean VHN: 76.95 \u00b1 3.73), followed by Group 2 (73.11 \u00b1 4.82), Group 3 (55.11 \u00b1 5.28), and Group 4 (51.25 \u00b1 7.73) (p &lt; 0.05). Shorter ultrasonic durations (3-s Ultrasonic) resulted in fewer voids and higher microhardness compared to longer durations (15-s Ultrasonic). There was no statistically significant difference in void size among the groups compared (p &gt; 0.05). Fractal dimension analysis showed that prolonged ultrasonic condensation results in less complex voids compared to shorter activation. Conclusion: Manual condensation of premixed bioceramic putty, by promoting denser particle packing without ultrasonic-induced disruptions, leads to higher microhardness. Brief ultrasonic activation (3-s Ultrasonic) optimizes the quality of Well-RootTM PT apical plugs by minimizing voids and maintaining higher microhardness, thus enhancing the apical seal. Prolonged ultrasonic activation (15-s Ultrasonic) increases void formation and reduces microhardness, potentially compromising the long-term integrity of the apical barrier.<\/jats:p>","DOI":"10.3390\/ma18214835","type":"journal-article","created":{"date-parts":[[2025,10,23]],"date-time":"2025-10-23T05:20:44Z","timestamp":1761196844000},"page":"4835","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Effect of Ultrasonic Condensation Time on Void Formation and Microhardness of Well-RootTM PT Apical Plugs in 3D-Printed Immature Teeth"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1577-4362","authenticated-orcid":false,"given":"Krasimir","family":"Hristov","sequence":"first","affiliation":[{"name":"Department of Pediatric Dentistry, Faculty of Dental Medicine, Medical University of Sofia, 1431 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ralitsa","family":"Bogovska-Gigova","sequence":"additional","affiliation":[{"name":"Department of Pediatric Dentistry, Faculty of Dental Medicine, Medical University of Sofia, 1431 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"188","DOI":"10.1111\/iej.13809","article-title":"Review of guidance for the selection of regenerative endodontics, apexogenesis, apexification, pulpotomy, and other endodontic treatments for immature permanent teeth","volume":"56","author":"Murray","year":"2023","journal-title":"Int. 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