Histological in vitro evaluation of the effects of Er:YAG laser on oral soft tissues

In oral pathology, laser devices can provide important advantages, especially in the treatment of certain lesions. However, there is controversy about the use of some wavelengths in the analysis of suspected dysplastic or neoplastic lesions, raising doubt about the laser’s suitability for use in biopsy procedures. In recent studies, the KTP and diode lasers have been used in biopsy procedures without histological artefacts. The aim of this in vitro study was to evaluate the exact extent of peripheral thermal damage to oral soft tissues caused by an Er:YAG laser (λ 2,940 nm) without water cooling. The study was performed on five swine cadaver tongues. Nine samples from each tongue were taken by the same operator using the Er:YAG laser with increasing energies (from 60 to 150 mJ) and fluencies (from 21 to 53 J/cm²). In addition to the laser samples, a specimen obtained using a scalpel was used as control. The samples were placed in 10% formalin solution and were examined by optical microscopy by two blinded pathologists who assigned a thermal damage score (from 0 to 3) to each sample. The Er:YAG laser produced less damage at 80 and 100 mJ and 28 and 35 J/cm² (intermediate parameters). Although in some samples thermal damage was minimally visible, in all samples histological evaluation was clearly possible. The study demonstrated that the Er:YAG laser can be safely used in oral biopsy investigations while ensuring a successful histological evaluation, which is fundamental to correct clinical management.