Histological evaluation of the surgical margins of oral soft tissue incisions using a dual-wavelength diode laser and an Er, Cr:YSGG laser; an ex vivo study.

OBJECTIVE: This study compared a dual-wavelength diode laser and an Er, Cr:YSGG laser in oral soft tissue incisions to determine the most effective and safest laser system at the histopathological level. METHODOLOGY: The (810 and 980 nm) dual-wavelength diode laser was used at 1.5 W and 2.5 W (CW) power settings, and the (2780 nm) Er, Cr:YSGG laser was used at 2.5 W and 3.5 W (PW) power settings. Both laser systems were used to incise the tissues of freshly dissected sheep tongue pieces to obtain the following histopathological criteria: epithelial tissue changes, connective tissue changes, and lateral thermal damage extent by optical microscopy. RESULTS: The epithelial and connective tissue damage scores were significantly higher in the dual-wavelength diode laser groups than in the Er, Cr:YSGG laser groups (P<0.001), and there was a significant difference between some groups. The extent of lateral thermal damage was also significantly higher in the diode laser groups than in the Er, Cr: YSGG laser groups (P<0.001), and there was a significant difference between groups. Group 2 (2.5 W) of the diode laser was the highest for all three criteria, while group 3 (2.5 W) of the Er, Cr:YSGG laser was the lowest. CONCLUSION: The Er, Cr:YSGG laser with an output power of 2.5 W is, histologically, the most effective and safest laser for oral soft tissue incision. The dual-wavelength diode laser causes more damage than the Er, Cr:YSGG laser, but it can be used with a low output power and 1 mm safety distance in excisional biopsy.

No-core fiber interferometry pH sensor based on a polyvinyl alcohol/polyacrylic acid and silica/polyvinyl alcohol/polyacrylic acid hydrogel coating.

In this paper, we present an investigation on the sensing performance of a pH sensor based on a modal interferometer formed by a simple NO-core fiber interferometer (NCFI) that operates in transmission mode. The fundamental configuration of this sensor encompasses a single-mode-no-core-single-mode fiber (SMF-NCF-SMF "SNCS") segment chain. The chemical etching method has been used with hydrofluoric (HF) acid to prepare diverse NCF diameters. This was proposed to expand the evanescent fields and enhance sensor sensitivity. Then, the two diverse segments of etched NCF were cladded with polymeric composite fabricated by polyvinyl alcohol/polyacrylic acid (PVA/PAA) hydrogel and pure silica nanoparticles embedded in polyvinyl alcohol/polyacrylic acid (SiO2@PVA/PAA) hydrogel, respectively, for more sensing enhancement. Our results reveal that the PAA/PVA coating is a candidate coating material for acidic sensing, while SiO2@PVA/PAA is more appropriate for the base sensing, in which these coating materials show enhancement in the sensitivity above the NCF structure before an uncoated sensor due to greater enhancement of the evanescent field affected by the coating layer. The experimental results demonstrate a high average sensitivity of 3.42 nm/pH unit for the 11 w.t.% PVA/PAA coated sensor in the pH range from 1 to 7 and 3.2 nm/pH unit in the pH range from 8 to 14. The sensor also displays high repeatability and stability and low cross-sensitivity to temperature. The simple fabrication and high sensitivity of this sensor may prompt many potential applications in the fields of biology and chemistry.