## 3 Discussion and Conclusions
Our case confirmed the previous observation where the resorptive pattern has been related to factors like trauma, poor oral health, malocclusion, and parafunctional activity. Indeed, these are described as risk factors for developing a local hypoxic micro-environment that can affect the local vascular supply [13]. An observational clinical study on replanted ankylotic teeth reported an overall reduction of the buccal cortical bone thickness not corresponding to a reduction in the palatal bone, as observed in this study in tooth 21 [14]. On the other side, the complete resorption of the buccal cortical bone observed in tooth 11 and the development of a different resorptive pattern can be explained by the diverse weight of risk factors, like the cortical bone fracture and the local trauma during the avulsion. This was confirmed by the different percussion sound of the two incisors: dull on 11 and high on 21. To note, no data are reported on alveolar fractures as local risk factors for the prognosis of avulsed and replanted teeth. In addition, we cannot exclude a possible role for systemic risk factors such as Th2 immunologic profile and macrophages type 1 and 2 (M1 and M2) ratio. In fact, several studies have evaluated the influence of a patient's Th2 immunologic profile on the occurrence of root resorption in avulsed and replanted teeth, both in cases managed with and without accordance to the guidelines. The results showed that after 1 year of follow up, the 82.98% of atopic patients did not exhibit root resorption, versus the 58.54% of the nonatopic ones [15; 16; 17]. Moreover, a recently published study showed the association between the macrophages type 1 and 2 (M1 and M2) ratio and root resorption. The M1s were associated with proinflammatory cytokines and the M2s to anti-inflammatory cytokines. Root resorption was enhanced by a higher M1/M2 ratio but was partially reduced by a lower M1/M2 ratio [18]. No data on Th2 immunologic profile and macrophages type 1 and 2 (M1 and M2) ratios are available for the herein presented case report. Despite the availability of official research, there is still some uncertainty on the clinical outcome of cases treated in accordance with the guidelines and of cases treated using alternative techniques and protocols. We believe that the preventive identification of local risk factors can be clinically relevant for the therapy over time and to obtain higher rates of good outcomes. However, the individual variability deserves further exploration to highlight other risk factors beyond those already known. Conceptualization, M.M., R.M. ; methodology, L.O. ; software, F.C., I.V. ; validation, E.C., A.N. ; formal analysis, A.Z., I.V. ; resources, E.C. ; data curation, M.M., A.N. ; writing--original draft preparation, M.M. ; writing--review and editing, R.M., L.O. ; visualization, A.Z., F.C. ; supervision, E.C. ; project administration, A.N. ; funding acquisition, E.C., A.N., A.Z. All authors have read and agreed to the published version of the manuscript. This research was funded by the European Research Council, ERC Starting Grant Project HIDDEN FOODS, grant number 639286 awarded to [PERSON]. [PERSON], [PERSON] and [PERSON] acknowledge funding received for this project through the European Research Council (ERC Starting Grant Project HIDDEN FOODS, G.A. 639286 awarded to [PERSON]). SEM analysis performed at the Laboratory of Technological and Functional Analyses of Prehistoric Artefacts (LTFAPA), Department of Classics, Sapienza University of Rome. The authors confirm that they have no conflict of interest. The case report was approved by the local institutional ethics committee (approval n.3493). This article was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. Informed consent was obtained from the individual participant included in this article.