CCN2 and Tooth abscess: In the periapical abscess group, we found the expression of ANGPT and CTGF to be significantly down-regulated in the healing group (ANGPT: healing at 6 months: − 4.66, healing at 12 months: − 4.73; CTGF: healing at 6 months: − 4.49, healing at 12 months: − 5.02), while upregulated in the non-healing group (ANGPT: 3.26 and CTGF: 4.23; Fig. 4).