Yumin Lee

Question

How much do everyday drinks stain the materials used in dental and orthodontic care, and does brushing help?

Method

A two-week immersion study: four beverages (coffee, coke, black tea, grape juice) against four materials (composite resin, PMMA, thermoplastic acrylic, orthodontic wax). I photographed samples daily and measured grayscale brightness, then used Raman spectroscopy to identify beverage-specific compounds.

Result

Black tea and grape juice stained the most, which went against my hypothesis that coffee would. Daily brushing slowed the discoloration but did not remove it.

Next

Photograph in color instead of grayscale so grape juice's red stain and coffee's brown can be told apart. Test several specimens per condition. Add saliva and pH cycling to get closer to a real mouth.

Read the abstract

Fixed orthodontic appliances make brushing harder, so I asked how much worse staining gets and whether some materials resist it better. I immersed composite resin, PMMA, thermoplastic acrylic and orthodontic wax in coffee, coke, black tea and grape juice for two weeks, tracked daily grayscale brightness in photographs, and used Raman spectroscopy to look for beverage-related compounds on the surfaces. I expected coffee to stain the most. Black tea darkened composite resin, PMMA and thermoplastic acrylic fastest, grape juice darkened wax fastest, coffee stained less, and coke left little visible color. The Raman results suggest coke acts differently from pigment deposition. Daily brushing slowed staining from grape juice and black tea but did not stop it.

Co-authors: Chungho Lee and Sungho Lee, EN Dental Clinic Center. The manuscript is under review at the Journal of Emerging Investigators, so only the abstract and selected figures are shown here.

Question

Could rising nighttime temperatures reduce sleep quality and, through that, change gut microbiome health?

Method

I measured warming from 1975 to 2025 using NASA GISTEMP and Berkeley Earth nighttime-minimum temperatures, read the human and animal literature on sleep and the microbiome, and built an exploratory projection under IPCC SSP scenarios in five-year steps to 2055.

Result

Nighttime minimums rose by roughly 0.207°C per decade. The review produced four testable hypotheses linking heat, sleep loss and microbiome function.

Next

Replace the simple proxy model with a Bayesian hierarchical model once cohort data that track temperature, sleep and the microbiome together become available.

Read the abstract

This study does not claim that climate change directly alters the gut microbiome. It reviews a hypothesized pathway: rising nighttime temperature, reduced sleep quality, an altered gut microbiome, and changes in gut health. I quantify warming from 1975 to 2025 with NASA GISTEMP and Berkeley Earth data, summarize large human sleep studies, separate human and animal findings on sleep loss and gut diversity, and present an exploratory model that projects temperature, sleep loss and microbiome risk in five-year steps to 2055 under IPCC SSP scenarios.

Read the full paper (PDF)