Dental Apical Inflammation Score (DAIS): Histopathological scoring for the evaluation of the apical inflammatory activity and local bone destruction

•The Dental Apical Inflammation Score (DAIS) can classify apical lesions in four types.•With significant differences regarding their inflammatory cell infiltration, bone tissue, epithelium, bacteria infiltration.•Bacterial osteitis in apical lesions is reported for the first time. The purpose of this study was to evaluate 210 periapical lesions with a newly created Dental Apical Inflammation Score/DAIS with regard to their inflammatory cell infiltration, bone tissue, epithelium, bacteria and foreign material. Specimens were obtained from 51 different dental practices over a period of 11 months. These specimens were then sent in for histopathological routine diagnostics. The DAIS classified 81 cases of Type 1 (acute inflammation = low, chronic inflammation = low), 79 cases of Type 2 (acute inflammation = low, chronic inflammation = high), 46 cases of Type 3 (acute inflammation = high, chronic inflammation = low) and 4 cases of Type 4 (acute inflammation = high, chronic inflammation = high). Bone tissue was found in 141 cases, signs for bacterial osteitis in 49 cases, cyst epithelium in 40 cases and foreign material in 27 cases. In 210 cases, cyst epithelium was evident in 27.2 % of Type 1, 15.2 % of Type 2, 8.7 % of Type 3 and in 50 % of Type 4 (p = .019). The 141 cases containing bone tissue showed signs of bacterial osteitis in 16.1 % of Type 1, 29.8 % of Type 2, 77.8 % of Type 3 and in 100 % of Type 4 (p < .001). In 64 cases, Bacteria was evident in 30 % of Type 1, 25 % of Type 2, 55 % of Type 3 and in 100 % of Type 4 (p = .013). The DAIS could classify apical lesions with statistically significant differences. Bacterial osteitis in apical lesions was reported for the first time.