###### Abstract  
Revascularization has been incorporated into endodontic practice and become a viable treatment alternative for immature teeth with pulp necrosis. Thorough disinfection of the root canal is a key factor for successful revascularization. An erbium: yttrium-aluminium-garnet (Er: YAG) laser has been proved advantageous for efficient root canal disinfection. This article reports one case of periapical periodontitis caused by a fractured occlusal tubercle. Revascularization assisted by Er: YAG laser irrigation was carried out with long-term follow up. During the process of treatment, we opened drainage to relieve the acute symptoms first. The necrotic pulp was removed, and then the root canal was rinsed with 0.5% sodium hypochlorite (NaOCI) solution assisted by Er: YAG laser irrigation, dried, and filled with a triple-antibiotic paste. After two weeks, the intracanal medication was removed, and 9 mL of whole vein blood was taken from the patient to prepare concentrated growth factor (CGF) after failing to induce enough blood into the canal system by over-instrumenting. The newly prepared CGF was transferred into the root canal. A 3 mm mineral trioxide aggregate (MTA) was placed directly on the thrombus of the CGF and then restored with glass-ionomer cement (GIC). The case was followed up for more than four years to record the clinical symptoms and imaging manifestations. Er: YAG irrigation is an efficient root canal disinfection protocol with the advantages of easy operation and minimal risk, which might be applicable to the revascularization of necrotic immature permanent teeth. erbium laser; irrigation; immature permanent teeth; periapical periodontitis; concentrated growth factor; regenerative endodontics +
Footnote †: journal: _Scienced Reviews of Applied and Computational Intelligence_  
**Copyright** © 2022 by the authors. Liconse MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/py/4.0/](https://creativecommons.org/licenses/py/4.0/)]([https://creativecommons.org/licenses/py/4.0/](https://creativecommons.org/licenses/py/4.0/))). **Featureued Application: Er: YAG irrigation is an efficient root canal disinfection protocol with the advantages of easy operation and minimal risk, which might be applicable to revascularization of necrotic immature permanent teeth. **  
**Citation:** [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Revascularization of an Immutative Permanent Tooth with Periapical Periodontitis Using Concentrated Growth Factor Assisted by Erbium Laser (2940 nm) Irrigation: A Case Report. _Appl. Sci._**2022**, 12**, 4751. [[https://doi.org/10.3390/appl2094751](https://doi.org/10.3390/appl2094751)]([https://doi.org/10.3390/appl2094751](https://doi.org/10.3390/appl2094751))  
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**Revascularization of an Immutative Permanent Tooth with Periapical Periodontitis Using Concentrated Growth Factor Assisted by Erbium Laser (2940 nm) Irrigation: A Case Report**  
**[PERSON]** 1,1, [PERSON]** 2,1, 2, 1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54,resulting in tooth extraction [2]. The traditional treatment for immature necrotic teeth is apexification [3]. However, the process requires several visits and a long treatment course. Additionally, the dressing may be absorbed gradually into the root canal. Recently, more attention has been paid to apical barrier technology, but it has high technical sensitivity and involves a complex operation process. Currently, there are increasing cases of revascularization due to its the advantages, including a simple operation and a better clinical effect on the thickening of canal walls and closure of the apex [4,5].