Influence of the dentin rewetting with chitosan after selective removal of carious lesion by Er: YAG: longitudinal clinical analysis, photographic evaluation, marginal adaptation of the replica of the restoration and microbiological analysis

Abstract

The Er: YAG laser is a feasible alternative to the conventional method of caries removal, however, in front of their possible interference in the adhesion process of resinous materials, it becomes relevant to assess the incorporation of a biopolymer (chitosan) in caries-affected dentin to allow an improvement in structural integrity and longevity of the restorations performed in laser-prepared cavities. This study aims to evaluate the effect of Er: YAG laser in the treatment of primary teeth and the influence of dentin rewetting with a bio modified compound (chitosan) through longitudinal analysis of restorations, evaluation of marginal adaptation of the replica of the restoration and microbiological analysis. The sample will consist of 40 children between 7 and 9 years old that have 4 active carious lesions, reaching dentin located on the occlusal surface (Class I) of deciduous molars counterparts. The selective removal of carious lesions will be performed with Er: YAG laser (250mJ/4 Hz) or contra-angle (conventional method). The teeth of each child will be randomly assigned into two groups according to the surface treatment: 1) without rewetting (control) and 2) chitosan 2.5%. Cavities will be etched with phosphoric acid at 35% and washed. For the chitosan group, immediate after the acid etching, chitosan will be applied on dentin for 15 seconds and the surface will be dried with absorbent paper. Then, specimens will be restored with adhesive (Single Bond 2 - 3M) and composite resin (Z250 - 3M). The clinical analysis of the restorations will be performed by three calibrated and experienced professionals using the modified United States Public Health Service (USPHS) criteria in the periods of 7 days (after polishing), 6 months, 12 months and 18 months of the end of restorations. The marginal adaptation of the replica of the restoration will be analyzed by scanning electron microscopy, followed by calculating the percentage of the marginal integrity in the same periods proposed for clinical analysis. The microbiological analysis will be performed using dentin scraps, collected in three periods: before removal of caries, after removal of caries and after treatment with chitosan. The colony forming units (CFUs) will be counted and the results will be expressed as CFU/mg of remaining dentin. The data will be analyzed and the appropriate statistical method will be used. (AU)