Exfoliative cytology of the oral mucosa under free end saddles recorded by two different impression techniques, muco-static and muco-compressive

Exfoliative cytology of the oral mucosa under distal- extension bases recorded by two different impression techniques: mucostatic and mucocompressive was investigated in this study. Eleven, patients were selected and divided into two groups [five in each group as one did not continue to the end of the study]. Each patient in the two groups received a mandibular distal-extension removable partial denture with an opposing complete maxillary denture. The mandibular partial dentures in the first group were constructed from mucostatic impressions, while, in the second group from mucocompressive impressions. All other steps of denture construction were made in a standard manner for all patients. Cytologic smears of oral mucosa under distal-extension bases were collected, fixed, stained with Papanicolaou's stain and then examined microscopically to calculate the Keratinization index. This cytologic examination was done : at the time of delivery and after : one mouth, two months and three months of denture wear. At each time interval, buccal, crestal and lingual smears were collected at the first molar region of the right side. The three smears were examined and then a mean Keratinization was calculated. Data of the cytologic examination of all patients were collected and statistically analyzed. It was found that Keratinization Index of the oral mucosa was significantly reduced under lower distal-extension bases recorded by either: mucostatic or mucocompressive technique. Maximum reduction was detected after one month of denture wear. The reduction in keratinization Index was significantly more under dentures constructed with mucocompressive impression technique than with mucostatic impression technique

Cast cobalt-chromium clasp behaviour during six month's denture wear

This investigation aims to assess the accuracy with which cobalt-chromium clasp are made and the degree to which they are still functioning after periods of wear of one month and six months. Two groups of clasps were made; the clasps in one group had a taper form; the clasps in the other group were uniform in cross-section. The force required to deflect each clasp by 0.25mm was ascertained using the Instron Universal Testing Machine [Instron Ltd High Wycombe, Bucks, England]. An apparatus for cyclic deflection of clasps was designed. Clasps were deflected by 0.25mm 240 times [representing one month's wear] and a further 1200 times [a total of six month's wear] and their permanent deformation was measured using electronic calipers. It was found that the force required to deflect clasps of apparently identical design and dimension was very variable. Permanent deformation of clasps occurred within one month and further deformation occurred the end of six months. The clasps of uniform cross section were more resistant to permanent deformation. It is concluded that cast cobalt chromium clasps are inconsistent in performance and may not be functioning as retainers after a short priod of denture wear in the mouth