|Year : 2017 | Volume
| Issue : 2 | Page : 67-68
Free - Should we take notice?
Sridevi Padmanabhan Prof. and HOD
Department of Orthodontics, SRMC, Porur, Chennai, Tamil Nadu, India
|Date of Web Publication||17-Apr-2017|
Department of Orthodontics, SRMC, Porur, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Padmanabhan S. BPA
Free - Should we take notice?. J Indian Orthod Soc 2017;51:67-8
Bisphenol A (BPA), a synthetic compound, forms the basis of a very busy industry which produces clear and tough plastic, a sector that thrives and grows annually. BPA, first produced in 1891, was identified as an estrogen mimic early on and its endocrine-disrupting properties have been recognized for decades. Endocrine disruptive chemicals (EDCs) are a recognized group of chemicals listed by the WHO  which are mostly human-made, found in various materials such as pesticides, food contaminants, and personal care products, thus facilitating human exposure through food, dust, water, and through skin.
BPA being one of the most extensively studied and well-known EDCs is known to bind and stimulate estrogen receptors and alters the response of tissues to normal estrogen. It has widely received bad press because of the potential hazards it poses to the brain causing behavioural effects, alters immune response, affects the action of other hormones and increases the risk of cancer. A variety of clinical conditions are linked to BPA, but the most important concern seems to be the long-term effect it has on the reproductive organs causing early onset puberty in females, feminization in males, and the long-term effect it can have on the fetus, since even in small doses, it is detected in adult and fetal blood, amniotic fluid, placental tissue, breast milk, and saliva.
BPA is commonly found in hard reusable plastic bottles and the epoxy lining of canned foods. Its release is said to increase several folds on heating and on exposure to acidic foods such as canned tomatoes. Thus, many countries have banned baby bottles which contain BPA, several products now carry the BPA-free tag, and lifestyle changes are advocated which include switching to glass, ceramic, or metal crockery, avoiding heating BPA-based plastic in microwaves and so on.
With so much environmental exposure of BPA, the additional exposure from dental products is a cause for concern.
In dentistry, BPA is a startup material of the bisphenol A glycidyl methacrylate, bisphenol A dimethacrylate, and bisphenol A ethoxylate dimethacrylate monomers found in dental sealants, adhesive resins, and composite resins and these have been studied for BPA release. In orthodontics, BPA release is detected not only in products that are used during active treatment but also during retention. A recent study evaluating a wide variety of orthodontic products found that thermoformed Biocryl acrylic resin retainer material and a fully cured Transbond XT orthodontic adhesive released BPA. While we may take comfort from the fact that orthodontic resins release BPA below the reference dose for daily intake, we are also reminded that complete polymerization is important not only for bond strength but also to minimize material degradation and leaching of toxic products. Bonding protocol including minor details such as position of the curing light plays a role in complete polymerization and therefore BPA release. It is also important to remove excess resin around the brackets and ask the patient to rinse thoroughly after bonding.
Hawley retainers which have been in use for several decades are also a source of BPA since the inhibitor (hydroquinone) present in the liquid component of the base plate material releases BPA. Vacuum-formed retainers (VFR) which are very popular and made of polypropylene/polyethylene are also suspect since BPA is added to polymers to make them clear and tough; however, this has escaped the radar of researchers till now. Recently, our team published findings comparing BPA release in the saliva of orthodontic patients between VFR retainers and heat-cured and chemical-cured Hawley retainers. All retainers significantly increased the concentration of BPA in saliva, but this was maximum with VFRs followed by self-cured resins and the least was in heat-cured resins. The results of this study could be extrapolated to other removable appliances that orthodontists use including the wide usage of functional appliances for the susceptible population of growing children.
In addition to previously mentioned health problems, concern has been expressed that BPA release in dental resins causes psychosocial problems in children. The increased BPA release from VFRs could be a cause for concern since polymeric aligners made of polyurethane have recently become extremely popular. Preliminary in vitro studies have revealed mixed results when evaluating the effect of invisalign appliances on oral epithelial cells., With many more aligner companies flooding the market more clarity in their composition and long term in vivo studies are required.
The jury is still out on the position of BPA exposure. On the one hand, BPA released from orthodontic materials is less than the recommended safety levels. The US human exposure limit and the European Food Safety Authority have set the tolerable daily intake level of BPA to 50 mg/kg/day., Moreover, the concentration of the released BPA is reduced because it is diluted by saliva and other fluids in the oral cavity. On the other hand, there is emerging research which implies that a low-dose effect exists that can alter cellular level signaling and cell functions., These may be examples of nonmonotonic dose responses, which are common for hormones and EDCs that mandate a new risk assessment for BPA.,
In the light of this information, the dental and orthodontic community cannot be complacent in the use of BPA-containing products. Till clarity emerges, we need to limit if not eliminate BPA release from orthodontic appliances by listening to the cautionary tales that research tells us.
“Primum non nocere”
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