Er:YAG激光工作尖插入深度对根管内氢氧化钙清除效果的影响OA

Objective:To investigate the effect of Er:YAG laser tip insertion depth on the removal efficacy of intra-canal calcium hydroxide Ca(OH)2 dressing,and to provide experimental evidence for optimizing clinical laser-activated irri-gation technology.Methods:A total of 30 isolated single premolars meeting the inclusion criteria were selected,and all crowns were sectioned to a uniform length of 18 mm.After routine root canal preparation,the root canals were filled with Ca(OH)2 paste,stored in a constant temperature and humidity environment at 37℃for 7 days.The samples were randomly divided into three groups(n=10 each),and root canal laser-activated irrigation was performed using an Er:YAG laser in SWEEPS mode,with the laser tip insertion depths set at 4 mm(Group A),7 mm(Group B),and 10 mm(Group C),respec-tively.Cone-beam computed tomography(CBCT)scans were performed on all samples before and after Ca(OH)2 removal.The DICOM data were imported into Mimics software for three-dimensional reconstruction to calculate the intracanal Ca(OH)2 volume before removal(V1)and after removal(V2),the removal rate was calculated.Scanning electron microscopy(SEM)was used to observe the residual Ca(OH)2 on the root canal walls in the apical region of each group,and the cleanliness was scored according to standard criteria.Results:CBCT results showed residual Ca(OH)2 in the root canals of all three groups,mainly concentrated in the apical region,presenting as hyperdense radiopaque images.The Ca(OH)2 removal rates of Groups A,B,and C all exceeded 97%,a statistically significant difference was observed between group A and group C(P<0.05),while no significant differences were found among the other comparisons.SEM observations demonstrated varying degrees of Ca(OH)2 residue on the inner root canal walls of the three groups;Group C exhibited the fewest Ca(OH)2 particles on the surface and the most fully exposed dentinal tubules.Semi-quantitative scoring results indicated that the cleanliness of Group C was significantly superior to that of Groups B and A(P<0.05),while no significant statistical difference was found between Group A and Group B.Conclusion:The insertion depth of the Er:YAG laser tip exerts a"proximal advantage"effect on the removal of intracanal Ca(OH)2 dressing,with a deeper insertion corresponding to a better removal efficacy.