Chemical removal of necrotic periodontal ligament on delayed replanted teeth by sodium hypochlorite: morphological analysis and microhardness indentation test of cementum

AimTo compare the efficacy of sodium hypochlorite (NaOCl) used at different concentrations and working times for removing necrotic periodontal ligament (PDL) from delayed replanted teeth and to observe the effects of NaOCl on surface structure and microhardness of cementum. MethodologyA total of 88 healthy premolars with a single root extracted for orthodontic purposes were selected and kept dry at room temperature for 1h. The teeth were divided into 11 groups: group 1 (control): roots were untreated; group 2: necrotic PDL was removed with gauze; groups 3-11: teeth were immersed in NaOCl at different concentrations (1, 2.5 and 5.25%) and for different working times (5, 10 and 15min). The specimens in each group were inspected separately for cementum integrity and the presence of PDL remnants by histomorphometric analysis, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Another 14 healthy premolars with roots divided into two pieces were selected for Vickers microhardness indentation tests before and after NaOCl treatment. The data were analysed statistically using Wilcoxon signed-rank test of two-related samples (P=0.05). ResultsIn teeth treated with 1% NaOCl for 15min or 5.25% NaOCl for 5min, the cementum remained morphologically intact without cracks, and PDL remnants were absent. In the 1% NaOCl for 15min group, the microstructure of cementum was arranged more regularly, as observed x8000 magnification by SEM. Teeth in each of the other groups displayed cementum damage and/or the presence of PDL remnants. Microhardness tests revealed that treatment with 1% NaOCl for 15min or 5.25% NaOCl for 5min significantly decreased microhardness of root cementum (P<0.05). ConclusionsUse of either 1% NaOCl for 15min or 5.25% NaOCl for 5min was effective at removing necrotic PDL from the delayed replanted teeth whilst having a minimal influence on cementum integrity. However, 1% NaOCl for 15min was less damaging to cementum.