Discussion - References.
In the present study, the in vitro oestrogenic effect of the endodontic sealer AH 26 has been demonstrated. On the contrary, AH Plus did not show an oestrogenic effect.
Adverse in Đˆuences of endodontic materials on periapical tissues are attributed to either toxic or hypersensitivity reactions. Researchers often fail to ascertain other adverse biological reactions, such as effects upon endocrine or immune functions. This study demonstrated the possible effects of endodontic sealers on endocrine function and this issue must be borne in mind in the future.
It is controversial whether the dental resinous materials containing (bis GMA), which is synthesized from the oestrogenic compound BPA, include unreacted BPA and/or can mimic the effects of natural steroid hormones. However, the present study demonstrated that a bis GMA-based endodontic sealer, such as AH 26, shows an oestrogenic effect in vitro.
The leakage into the environment of oestrogenic monomers, suchas BPA and BADGE, from bisGMA-based composites and sealants (Pulgar et al. 2000) as well as the oestrogenic effect of BPA, a component of AH 26 (Olea et al. 1996, Hashimoto & Nakamura 2000, Pulgar et al. 2000) has been demonstrated. Thus, although it can be hypothesized that the oestrogenic effect of AH 26 showed in this study is due to its content in BPA, the oestrogenic effect of AH 26 also can be due to other unknown ingredients of the sealer. Tarumi et al. (2000) found that two commercially available sealants showed oestrogenic activity, although none of the tested materials contained BPA.
Cytotoxicity testing of endodontic materials must be viewed as an assessment of hazards, that is the potential of the material to cause periapical problems. In this context, bis GMA-based endodontic sealers are possible hazards to periapical tissues. The risks that these materials will cause periapical toxicity or endocrine effects in vivo can be partlyestimated by assessing the cytotoxicity or the endocrine activity of the substances which are released from these materials in vitro and comparing these cytotoxic concentrations with those concentrations that are present in vivo. In the case of AH 26 and BPA the endocrine activity of these substances incurrent tests, and therefore the risks of periapical or systemic effects, depends on the irability to leak through the apical foramen into periradicular tissues.
Imai & Komabayashi (2000) studied the leaching characteristics of BPA from composite resins. The same authors found that the elution of BPA was rapid during 6-h period, and then declined and continued steadily, suggesting that little or no oestrogenic effect due to long-term elution of BPA from commercial bisGMA based resins is expected in practice.
Lewis et al. (1999), using high-pressure liquid chromatography (HPLC), analyzed 28 different commercially available dental resins for the presence of BPA finding that only one resin, Delton II, had detectable levels of BPA. Likewise, eluates from Delton II were the only samples that elicited a significant proliferative response in two of the MCF-7 sublines tested. These authors concluded that dental resins in general do not represent a significant source of BPA exposure.
However, since there are no realistic estimates of the concentrations levels at which polymerized resin components mayoccur in the periradicular tissues following root canal treatment, no firm clinical conclusions can be drawn. Pulgar et al. (2000) showed the leaching of oestrogenic monomers into the environment by bisGMA based composites and sealants in concentrations at which biologic effects have been demonstrated in in vivo experimental models. Moreover, Kaplan et al. (1997) have shown that the endodontic sealer AH 26, containing BADGE, disintegrated and lost 1.22% of mass when stored at 37 8C and a relative humidity above 95% for 45 days. This result suggests that bisGMA based resins used in endodontics such as AH 26 could constitute a chronic source of BPA. Thus, although the results of this study are based on results in vitro and do not necessarily confirm any clinical activity, the oestrogenic effect of AH 26 in this work is evident.
AHPlus did not have an oestrogenic effect. Other properties and advantages of AH Plus are that it is eugenol and paraformaldehyde free, has a rapid setting time, higher radiopacity, improved removability, lower solubility and an acceptable biocompatibility (Whitworth & Boursin 2000, DeAlmeida et al. 2000). Conclusions AH 26 showed in vitro oestrogenic effect, but not AH Plus. The endodontist must consider the possible oestrogenic effect of AH 26, as well as the cytotoxic effects of root filling materials, in order to avoid the leakage of sealer through the apex during root canal treatment. The choice of AH Plus as endodontic sealer avoids the possibility of oestrogenic activity in the periradicular tissues.
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