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Spectrophotometric evaluation of the efficacy of natural versus commercial bleaching agents

Kohli S, Al-Haddad A, Siew AY, Nam WL, Hamdan HD, Roslan QA

Am J Dent, 2021 04;34(2):75-79.
PMID: 33940663

PURPOSE: To compare the bleaching efficacy of in-office (Opalescence), professional home (LumiBrite), over the counter (WhiteLight) and natural (strawberry extract) bleaching agents.
METHODS: 80 teeth were selected and divided into two groups which were stained with black coffee and red wine respectively. The stained specimens were subdivided into four subgroups to be bleached with Opalescence, LumiBrite, WhiteLight and strawberry extract. Color measurements were made using spectrophotometer at baseline level, after staining, after bleaching and 1 week after bleaching. The ΔE₀₀ was calculated post bleaching (ΔE₀₀1), after 1-week follow up (ΔE₀₀2) and color changes between 1-week follow up and baseline (ΔE₀₀3). Data were analyzed by paired t-test and ANOVA with a significant difference of P< 0.05.
RESULTS: Paired t-test showed significant differences in ΔE₀₀1 and ΔE₀₀2 for both stained specimens (P< 0.001). For black coffee stained specimens, Whitelight had significantly higher ΔE₀₀2 compared to the other bleaching agents (P< 0.05). For red wine stain, Whitelight also showed the significantly lowest ΔE₀₀1 (P< 0.001) and the highest ΔE₀₀2 (P< 0.001) compared to other groups. LumiBrite showed the significantly lowest ΔE₀₀3 for red wine stained specimens (P< 0.05). Whitelight had the poorest bleaching efficacy with deterioration effect after 1-week follow up. Opalescence, LumiBrite and strawberry extract had clinically perceptible and comparable bleaching efficacy. Strawberry extract appeared to be a potential natural bleaching agent with a desirable effect.
CLINICAL SIGNIFICANCE: Commercial tooth bleaching agents can cause several undesirable side effects such as damage to enamel, hypersensitivity and even affecting the pulp. Strawberry extract is a natural, effective bleaching agent that may have reduced side effects.
Fulltext OSC47: Efficacy of Four Different Types of Bleaching Agents on Stained Natural Teeth using Spectrophotometer

Kohli S, Yin ASY, Nam WL, Hamdan HD, Roslan QA

J Indian Prosthodont Soc, 2018 Oct;18(Suppl 1):S28.
PMID: 30532438 DOI: 10.4103/0972-4052.244640
Production of bio-fertilizer from microwave vacuum pyrolysis of palm kernel shell for cultivation of Oyster mushroom (Pleurotus ostreatus)

Nam WL, Phang XY, Su MH, Liew RK, Ma NL, Rosli MHNB, et al.

Sci Total Environ, 2018 May 15;624:9-16.
PMID: 29245037 DOI: 10.1016/j.scitotenv.2017.12.108

Microwave vacuum pyrolysis of palm kernel shell (PKS) was performed to produce biochar, which was then tested as bio-fertilizer in growing Oyster mushroom (Pleurotus ostreatus). The pyrolysis approach produced biochar containing a highly porous structure with a high BET surface area of up to 270m2/g and low moisture content (≤10wt%), exhibiting desirable adsorption properties to be used as bio-fertilizer since it can act as a housing that provides many sites on which living microorganisms (mycelium or plant-growth promoting bacteria) and organic nutrients can be attached or adsorbed onto. This could in turn stimulate plant growth by increasing the availability and supply of nutrients to the targeted host plant. The results from growing Oyster mushroom using the biochar recorded an impressive growth rate and a monthly production of up to about 550g of mushroom. A shorter time for mycelium growth on one whole baglog (21days) and the highest yield of Oyster mushroom (550g) were obtained from cultivation medium added with 20g of biochar. Our results demonstrate that the biochar-based bio-fertilizer produced from microwave vacuum pyrolysis of PKS shows exceptional promise as growth promoting material for mushroom cultivation.
A review on valorization of oyster mushroom and waste generated in the mushroom cultivation industry

Wan Mahari WA, Peng W, Nam WL, Yang H, Lee XY, Lee YK, et al.

J Hazard Mater, 2020 12 05;400:123156.
PMID: 32574879 DOI: 10.1016/j.jhazmat.2020.123156

A review of valorization of oyster mushroom species and waste generated in the mushroom cultivation is presented, with a focus on the cultivation and valorization techniques, conditions, current research status and particularly the hazard mitigation and value-added recovery of the waste mushroom substrate (WMS) - an abundant waste in mushroom cultivation industry. Based on the studies reviewed, the production rate of the present mushroom industry is inadequate to meet market demands. There is a need for the development of new mushroom cultivation methods that can guarantee an increase in mushroom productivity and quality (nutritional and medicinal properties). This review shows that the cylindrical baglog cultivation method is more advantageous compared with the wood tray cultivation method to improve the mushroom yield and cost efficiency. Approximately 5 kg of potentially hazardous WMS (spreading diseases in mushroom farm) is generated for production of 1 kg of mushroom. This encourages various valorization of WMS for use in agricultural and energy conversion applications, mainly as biocompost, plant growing media, and bioenergy. The use of WMS as biofertilizer has shown desirable performance compared to conventional chemical fertilizer, whilst the use of WMS as energy feedstock could produce cleaner bioenergy sources compared to conventional fuels.
Applying microwave vacuum pyrolysis to design moisture retention and pH neutralizing palm kernel shell biochar for mushroom production

Wan Mahari WA, Nam WL, Sonne C, Peng W, Phang XY, Liew RK, et al.

Bioresour Technol, 2020 Sep;312:123572.
PMID: 32470829 DOI: 10.1016/j.biortech.2020.123572

Microwave vacuum pyrolysis of palm kernel shell was examined to produce engineered biochar for application as additive in agriculture application. The pyrolysis approach, performed at 750 W of microwave power, produced higher yield of porous biochar (28 wt%) with high surface area (270 cm2/g) compared to the yield obtained by conventional approach (<23 wt%). Addition of the porous biochar in mushroom substrate showed increased moisture content (99%) compared to the substrate without biochar (96%). The mushroom substrate added with biochar (150 g) was optimal in shortening formation, growth, and full colonization of the mycelium within one month. Using 2.5% of the biochar in mushroom substrate desirably maintained the optimum pH level (6.8-7) during the mycelium colonization period, leading to high mycelium growth (up to 91%) and mushroom yield (up to 280 g). The engineered biochar shows great potential as moisture retention and neutralizing agent in mushroom cultivation.