Evaluation of the permeability and morphological alteration of the dental surface after apicoectomy, treatment and preparation with Er:YAG and Nd:YAG lasers

One of the objectives of endodontic treatment is to resolve pathological periapical processes caused by microbial contamination of the dental pulp. Correct execution of the necessary chemical preparation prior to surgery generally results in positive outcomes. However, a percentage of cases do not respond favorably and therefore require retreatment, a conservative therapeutic option. There are meanwhile a number of treatment failures which do not respond to these conservative measures and must therefore be subjected to paraendodontic surgical procedures. One of the principal problems of this therapeutic conduct is linked to the surface permeability of the dentin after apicoectomy and the lack of adequate marginal adaptation between the retrofilling material and the cavity walls. This permits the percolation of microorganisms and their metabolic by products from the system of root canals to the periapical region, thereby compromising the necessary tissue repair. The present work proposes the evaluation of the surface and marginal permeability of cut dentin after apicoectomy and treatment with Er:YAG and Nd:YAG lasers with fiber optics and then retrofilled with intermediate restorative material (IRM). A total of 24 single rooted teeth whose canals were endodontically treated were divided into 3 experimental groups: group I, whose apices were sectioned with an Er:YAG laser and the resulting cavity and the cut dental surface were irradiated with this laser via a 50/10 type fiber; in group II the apicoectomy was conducted with an Er:YAG laser and the resulting cavity and the cut surface were irradiated with a Nd:YAG laser; in group III, the samples were apicoectomized and the cavities were treated with a high speed bur (control group). Analysis of the infiltration of the dye methylene blue throughout the cut dental surface and the reconstruction demonstrated that the samples in the irradiated groups presented lower indices of infiltration than the control group. The Group I samples, meanwhile, did not present statistically significantly better results than the control group. Group II presented statistically significantly less infiltration than the other experimental groups. This result is compatible with the morphological and structural alterations evidenced by scanning electron microscopy: the group I samples (Er:YAG) presented clean, irregular surfaces with the presence of some cratering, without a smear layer and with the dental tubules exposed. The group II samples (Er:YAG and Nd:YAG) presented smoother, clean surfaces, without a smear layer, with fusion and resolidification of the dentin which sealed the dental tubules. Under the conditions of the study, apicoectomy with the Er:YAG laser followed by subsequent treatment of the cut surface and resulting cavity with a Nd:YAG laser, have shown as an option capable of reducing the permeability of the dentin to methylene blue dye. (author)