Keratinization of palatal mucosa beneath metal-based removable partial dentures

Exfoliative cytology provides a non-invasive method of examining changes in epithelial differentiation beneath dentures. Cell sampling by mechanical scraping may introduce errors due to collection of deeper epithelial cells, therefore an alternative sampling method was evaluated. Cells collected from the hard palates of 24 dentate subjects using either a wooden tongue depressor or transparent, adhesive-coated tape were fixed and stained by Papanicolaou's technique. The percentage of the total epithelial cells counted that were anucleate (the orthokeratinization index) was 99.95 per cent using the tape technique but 15 per cent lower using the smear technique. It appears that the tape technique gives a more accurate representation of the orthokeratinization of superficial cell layers. The tape technique was used to examine epithelial changes beneath tooth-supported removable partial dentures (RPDs). In 26 subjects, who had worn cobalt chromium based RPDs for at least 6 months, samples taken from beneath the metal denture base had a 50 per cent lower orthokeratinization index than those from uncovered areas of the palate.