166
T. Chandran et al.
cured adhesive resins was compared by [18]. It was noted that the eluents containing
particles of resins could not induce any proliferation in the active estrogen-sensitive
MCF-7 breast cancer cells and the MB-231 adenocarcinoma cells which served as
the control. Another study by [23] compared the estrogenicity of heat cured and light
cured dental adhesives which were collected during the debonding process of fixed
orthodontic appliances. It was observed that BPA in self-cured resins increased the
proliferation of MCF-7 breast cancer cells by 160% while there was a 128% increase
by BPA released from light cured resin adhesives.
Regarding the in vivo effects of BPA there has been a controversy in the safely
tolerated levels. While the European Food Safety Authority has proposed a level
of 50 µg/kg/day, study by [53] mentioned that levels lesser than 50 µg can alter
biological activities of cells.
Reccomendations to decrease the exposure to residual monomers include keeping
the light cure tip as close as possible to the adhesive resin, using indirect polymerization across the bracket edge to ensure minimal amount of unpolymerization, making
the patient rinse the mouth in the first hour after placement of brackets or bonding
the retainer and removing the unpolymerized layer by doing a pumice prophylaxis
[32].
Evidences from in vivo studies are limited and more studies are needed to elaborate
the effects of resins used in orthodontic appliances.
2.3 BIS Phenol A from Composites and Pit and Fissure
Sealants
BPA by itself is not a component of sealants or composite restorations. It is the
starting material of Bis-GMA, which is a common monomer used in composites.
Hence it is present in trace amounts in these monomers. Another common source of
release of BPA is through hydrolydid of Bis-DMA by salivary esterases. Bis-DMA
is another commonly used monomer. Unlike Bis-DMA, Bis-GMA does not undergo
hydrolysis by salivary esterases. On exposure to Oxygen, the superficial layer of the
sealants remain unolymerized. This causes leaching of the unpolymerized monomer
into the saliva. This leaching is maximum during the initial hours following the
sealant placement which gradually decreases. Studies measuring the BPA levels in
urine levels following sealant placement, have shown an increase in urine BPA for
up to 30 h [31].
The resin-based composites are made of filler particles, matrix composed of resins,
and coupling agents. The matrix is composed of monomers like UDMA, Bis-GMA,
EGDMA, TEGDMA, etc.
T. Chandran et al.
cured adhesive resins was compared by [18]. It was noted that the eluents containing
particles of resins could not induce any proliferation in the active estrogen-sensitive
MCF-7 breast cancer cells and the MB-231 adenocarcinoma cells which served as
the control. Another study by [23] compared the estrogenicity of heat cured and light
cured dental adhesives which were collected during the debonding process of fixed
orthodontic appliances. It was observed that BPA in self-cured resins increased the
proliferation of MCF-7 breast cancer cells by 160% while there was a 128% increase
by BPA released from light cured resin adhesives.
Regarding the in vivo effects of BPA there has been a controversy in the safely
tolerated levels. While the European Food Safety Authority has proposed a level
of 50 µg/kg/day, study by [53] mentioned that levels lesser than 50 µg can alter
biological activities of cells.
Reccomendations to decrease the exposure to residual monomers include keeping
the light cure tip as close as possible to the adhesive resin, using indirect polymerization across the bracket edge to ensure minimal amount of unpolymerization, making
the patient rinse the mouth in the first hour after placement of brackets or bonding
the retainer and removing the unpolymerized layer by doing a pumice prophylaxis
[32].
Evidences from in vivo studies are limited and more studies are needed to elaborate
the effects of resins used in orthodontic appliances.
2.3 BIS Phenol A from Composites and Pit and Fissure
Sealants
BPA by itself is not a component of sealants or composite restorations. It is the
starting material of Bis-GMA, which is a common monomer used in composites.
Hence it is present in trace amounts in these monomers. Another common source of
release of BPA is through hydrolydid of Bis-DMA by salivary esterases. Bis-DMA
is another commonly used monomer. Unlike Bis-DMA, Bis-GMA does not undergo
hydrolysis by salivary esterases. On exposure to Oxygen, the superficial layer of the
sealants remain unolymerized. This causes leaching of the unpolymerized monomer
into the saliva. This leaching is maximum during the initial hours following the
sealant placement which gradually decreases. Studies measuring the BPA levels in
urine levels following sealant placement, have shown an increase in urine BPA for
up to 30 h [31].
The resin-based composites are made of filler particles, matrix composed of resins,
and coupling agents. The matrix is composed of monomers like UDMA, Bis-GMA,
EGDMA, TEGDMA, etc.