Dental Dentures

111 (Partial Dentures: Anchorage with Precision Attachments)

Many misunderstandings between dentist and laboratory technician occur because the dentist cannot seat a cast partial denture in the mouth, although the model was correctly surveyed. The cause is as follows:

In order for the retentive arm of a clasp to properly spring over the height of contour, an inclined surface must be present above the survey line just as an inclined surface must be present below it, leading into the retentive undercut.

The problem here is that frequently an inclined surface above the height of contour is missing.

Although natural, unchanged teeth often possess such inclined surfaces, these eventually disappear through tipping and/or abrasion. Upon insertion, the result is that the clasp rests on a flat surface.

If one is unaware of this situation and applies too much pressure in an attempt to further seat the partial denture, the clasp will be bent (Fig. 111).

112 (Partial Dentures: Anchorage with Precision Attachments)

Typical in this situation is that the height of contour is located quite far occlusally and above it no inclined surface to gradually open the clasp is present. In such cases, scraping the diagnostic model is again required to ascertain the amount and location of preparation necessary on the tooth itself (Fig. 112).

113 (Partial Dentures: Anchorage with Precision Attachments)

Again, failure was caused by a lack of adequate preparation of the teeth to be clasped. Here, too, if more care had been taken during preliminary surveying of the diagnostic model, the problems would have been recognized initially (Fig. 113).