Microplastics in Dentistry—A Review
167
2.4 Toothpastes and Microplastics
Ustabasi and Baysal [55] conducted a study on 20 toothpaste samples to identify
and quantify the type of microparticles present. They found that 4 out of 20 samples
showed the presence of polyethylene type MPs in the concentration range of 0.4–1%.
Another study by [28] identified the presence of 0.17% of polyethylene type MPs
in a single sample they tested. Praveena et al. [42] found polyethylene type MPs in
the concentration of 7% in the sample tested. Bråte et al. [7] conducted a study on
100 ml of a popular toothpaste brand and extracted 100 mg of polyethylene MPs. In
contrary to these studies, the studies by [35] reported the absence of MPs in all the
samples tested.
Ustabasi and Baysal [56] attempted to find the effect of toothpaste derived MPs
on bacterial strains found in sea water. The bacterial strains studied were B. subtilis,
S. aureus, P. aeruginosa, and E. coli. The bacteria were studied under laboratory
conditions and in sea water. In the standard condition, only P. aeruginosa was affected
significantly with a growth inhibition of 20–35%. In sea water, B.subtilis was affected
significantly with a growth inhibition of 20–30% while S. aureus showed a slight
growth inhibition of 0–30%. This study also showed the discrepancy in results when
studied under laboratory and actual marine environments.
Polyethylene is the most common MP worldwide and toothpaste contain up to
1.8% polyethylene [10]. Similar MPs were also found in effluent of waste water treatment plant [WWTP]. Though the WWTPs remove MPs efficiently, their concentration in effluents is still high [38]. MPs in seawater get coated with a bacterial biofilm
called slime or conditioning film. They are also subjected to physical stresses, varying
temperatures, UV-radiation, oxidation, and salinity. The weathered or conditioned
MPs have an altered surface morphology and increased density and they sink to
bottom. This makes their availability more for a variety of marine organisms [51].
Mussels are considered as indicators of microplastic pollution in marine environment. A study was conducted by Bråte et al. [7] to identify the effects of PE MPs on
M. galloprovincialis. They observed that weathered PE microparticles were ingeted
more compared to virgin PE particles. The various histopathological changes in the
exposed mussels include a decrease or complete absence of contacts between filaments in the gills, haemocyte infiltration in gills, replacement of ciliated epithelium
by squamous epithelium in the digestive glands. In organs like mantles and gonads
severe tissue necrosis was noted.
3 Polymer Degradation and Impacts
3.1 Saliva Components
Water forms the largest proportion of saliva. RBC being a polar material, water
molecules percolate into the polymer network causing diffusion of uncured
167
2.4 Toothpastes and Microplastics
Ustabasi and Baysal [55] conducted a study on 20 toothpaste samples to identify
and quantify the type of microparticles present. They found that 4 out of 20 samples
showed the presence of polyethylene type MPs in the concentration range of 0.4–1%.
Another study by [28] identified the presence of 0.17% of polyethylene type MPs
in a single sample they tested. Praveena et al. [42] found polyethylene type MPs in
the concentration of 7% in the sample tested. Bråte et al. [7] conducted a study on
100 ml of a popular toothpaste brand and extracted 100 mg of polyethylene MPs. In
contrary to these studies, the studies by [35] reported the absence of MPs in all the
samples tested.
Ustabasi and Baysal [56] attempted to find the effect of toothpaste derived MPs
on bacterial strains found in sea water. The bacterial strains studied were B. subtilis,
S. aureus, P. aeruginosa, and E. coli. The bacteria were studied under laboratory
conditions and in sea water. In the standard condition, only P. aeruginosa was affected
significantly with a growth inhibition of 20–35%. In sea water, B.subtilis was affected
significantly with a growth inhibition of 20–30% while S. aureus showed a slight
growth inhibition of 0–30%. This study also showed the discrepancy in results when
studied under laboratory and actual marine environments.
Polyethylene is the most common MP worldwide and toothpaste contain up to
1.8% polyethylene [10]. Similar MPs were also found in effluent of waste water treatment plant [WWTP]. Though the WWTPs remove MPs efficiently, their concentration in effluents is still high [38]. MPs in seawater get coated with a bacterial biofilm
called slime or conditioning film. They are also subjected to physical stresses, varying
temperatures, UV-radiation, oxidation, and salinity. The weathered or conditioned
MPs have an altered surface morphology and increased density and they sink to
bottom. This makes their availability more for a variety of marine organisms [51].
Mussels are considered as indicators of microplastic pollution in marine environment. A study was conducted by Bråte et al. [7] to identify the effects of PE MPs on
M. galloprovincialis. They observed that weathered PE microparticles were ingeted
more compared to virgin PE particles. The various histopathological changes in the
exposed mussels include a decrease or complete absence of contacts between filaments in the gills, haemocyte infiltration in gills, replacement of ciliated epithelium
by squamous epithelium in the digestive glands. In organs like mantles and gonads
severe tissue necrosis was noted.
3 Polymer Degradation and Impacts
3.1 Saliva Components
Water forms the largest proportion of saliva. RBC being a polar material, water
molecules percolate into the polymer network causing diffusion of uncured