Effect of different bleaching techniques on DNA damage biomarkers in serum, saliva, and GCF

Bleaching agents containing a high concentration of H2O2 in the dental market lead to formation of reactive oxygen species, which have genotoxic effects. However, ozone bleaching, one of the most effective oxidants known, stimulates blood circulation and immune response and thus it has strong antimicrobial activity against viruses, bacteria, fungi, and protozoa. For these reasons, one of our hypothesis was ozone bleaching would reduce local and systemic DNA damage in the body. Hence, we aimed to determine the oxidative DNA damage biomarker levels in serum, saliva, and gingival crevicular fluid (GCF) by measuring 8-hydroxy-2′-deoxyguanosine (8-OHdG) after different bleaching methods. Forty-eight volunteers who requested dental bleaching were divided into three treatment groups ( n = 16). Group 1: ozone bleaching with the ozone-releasing machine; Group 2: chemical bleaching with 40% hydrogen peroxide (H2O2) gel; Group 3: 40% H2O2 gel activated with the diode laser. Initial and post-operative (immediately after bleaching and two weeks later) color measurements were performed with a spectrophotometer. The color changes were calculated with the CIEDE2000 (Δ E00) formula. 8-OHdG levels in serum, saliva, and GCF samples were determined with ELISA. All three treatments resulted in efficient and statistically similar bleaching. The 8-OHdG levels in the serum and saliva were not affected by all bleaching methods ( p > 0.05), but a temporary increase was observed in the GCF for chemical and laser-assisted groups except the ozone group ( p > 0.05). According to the findings, chemical and laser-assisted bleaching can affect DNA damage locally but not systemically. Bleaching with ozone may eliminate this local DNA damage.

Improvement in selectivity of ozone bleaching using DTPA as carbohydrate protector for wheat straw pulp

Effect of using diethylenetriamine pentaaceticacid (DTPA) as carbohydrate protector in ozone stage on delignification efficiency, bleaching efficiency, selectivity, metal ions, strength, morphological properties and effluent properties of wheat straw pulp was studied. Using DTPA during ozone treatment viscosity of pulp was improved by 1.1 units, delignification efficiency improved by 13.8 % and pulp brightness improved by 2.5 units compared to that of control. Most importantly the selectivity of ozone treatment was improved by 124 %. Ozone treatment along with DTPA reduced the Fe, Cu and Mn content in the pulp by 52 %, 27 % and 70 %, respectively. Use of DTPA in ozone stage improved the bleached pulp viscosity by 9 %, post colour number by 27 % and reduced the pulp shrinkage by 5 % compared to control pulp. DTPA treated and control pulps have comparable physical strength and morphological properties.

Additives to decrease cellulose chain scission during ozone bleaching of wheat straw pulp

The efficacy of different chemical additives like acetic acid, ammonium molybdate, diethylene triamine pentaacetic acid (DTPA), mannitol, methanol, per acetic acid (PAA), sodium hypochlorite (NaOCl) and sulfamic acid as carbohydrate protector during ozone bleaching of wheat straw pulp was studied. DTPA was found the most effective additive for ozone bleaching followed by the methanol. Using DTPA during ozone treatment improved the delignification efficiency by 13.8 %, bleaching efficiency by 19.8 %, selectivity of ozone by 124 % and reduced the chain scission number of glycosidic linkages in cellulose by 55.3 % compared to that of control. Ozone treatment along with DTPA reduced the Fe, Cu and Mn content in the pulp by 52 %, 27 % and 70 %, respectively. Use of methanol improved the delignification efficiency by 9.0 %, bleaching efficiency by 12.2 %, selectivity by 32.4 % and reduced the chain scission number by 22.2 % compared to that of control. The NaOCl was found to be the most effective for improving the delignification efficiency followed by PAA, they improved the delignification efficiency by 29.3 % and 27.3 %, respectively. The PAA improved the bleaching efficiency to a maximum of 39.9 % followed by 30.2 % with NaOCl.