A pilot study comparing optical coherence tomography, radiography, clinical photography, and polarisation microscopy for studies of hypomineralisation disturbances in enamel

Aim

To investigate the use of optical coherence tomography (OCT) as a tool to assess general and localised hypomineralisation defects in the enamel.

Design and Materials

Ten extracted permanent teeth (four teeth with localised hypomineralisation, four teeth with general hypomineralisation, and two healthy controls) were used in this study. In addition, four participants who underwent OCT served as living controls for the extracted teeth.

Methods

The OCT results were compared with clinical photographs, digital radiographs, and polarising microscopy images of tooth sections (considered the gold standard) to determine the method with the most accurate information regarding the extent of enamel disturbances: 1) visibility of enamel disturbance (visible yes/no); if yes, 2) extent of the disturbance in the enamel; and 3) determination of the plausible involvement of the underlying dentin.

Results

OCT was more accurate than digital radiography and visual assessment. OCT could provide information about the extent of localised hypomineralised disturbances in the enamel that was comparable to that with polarisation microscopy of the tooth sections.

Conclusion

Within the limitations of this pilot study, it can be concluded that OCT is suitable for investigating and evaluating localised hypomineralisation disturbances; however, it is less useful in cases with generalised hypomineralisation of the enamel. In addition, OCT complements radiographic examination of enamel; however, more studies are necessary to elucidate the full extent of the use of OCT in case of hypomineralisation.

Characterization of the rat myometrial contractile response to neuropeptide Y

The in vitro contractile effect of neuropeptide Y (NPY) on rat myometrial strips was for the first time demonstrated and characterised, and the EC50 value estimated to be 267 +/- 87 nM. This effect is presumably mediated by the NPY1 receptor being responsible for postsynaptic effects throughout the peripherial nervous system, thus indicating a direct uterotonic effect of NPY. Further, the effect was demonstrated to the dependent on extracellular Ca2+. Short-term exposures to NPY markedly desensitized the tissue affecting subsequent responses to NPY as well as to oxytocin (OT). This desensitization was time and concentration-dependent, but lasted less than three hours. However, long-term infusions of NPY for 5 days increased to response to both NPY and OT. Long-term infusions of OT caused a marked decrease of the NPY response, and it is concluded that common pathways for up and down regulation of the myometrial responsiveness to several peptide hormones may exist.

Tachykinins induce secretion of prolactin from perifused rat anterior pituitary cells by interactions with two different binding sites

Substance P and the two other mammalian tachykinins, neurokinin A and B, are accepted to have direct regulating effects at the anterior pituitary level. We have examined the effects of substance P (SP) and neurokinin B (NKB), alone and in combination, on prolactin release from cultured anterior pituitary cells grown on collagen-coated micro beads and placed in a perfusion system. Prolactin (Prl) secretion was observed within 25 s after exposure to either secretagogue and reached a maximum within 60-80 s. Furthermore, the prolactin response induced by SP and NKB was dose-dependent. Prl secretion remained constant for up to 4 h when SP or NKB were perifused and then fell gradually towards basal levels. Simultaneous addition of submaximal concentrations of SP and NKB resulted in an additive response compared with the responses of either secretagogue alone. Continuous (8 h) perifusion with SP did not prevent a normal prolactin response by NKB or TRH. These results indicate that the tachykinins, substance P and neurokinin B, release Prl from perifused female rat anterior pituitary cells by interaction with two different receptors, possibly the NK1 and NK3 tachykinin receptor subtypes.