During clinical examination, it was noted that patient has natural lower anterior teeth which occlude against the complete upper denture. Clinician is most likely to find:
A single complete denture is a complete denture that occludes against some or all of the natural teeth, a fixed restoration, or a previously constructed removable partial denture or a complete denture.
The primary consideration for a single complete denture is preservation. By opposing the natural teeth, the magnitude of force transmitted to the denture and arrangement of artificial teeth will be the major considerations while planning the denture. These will be discussed in this chapter.
Disadvantages
The unfavourable force distribution by the natural teeth can cause the following adverse changes:

Extensive morphological changes in denture foundation.
Jaw relationship extremes which make it difficult to arrange artificial teeth for the denture along the line of support.
Excessively displaceable denture-bearing tissue (flabby ridges).

Indications
A single complete denture may be desirable when it is to oppose any one of the following conditions:

Natural teeth sufficient in numbers not to necessitate a fixed or removable partial denture.
A partially edentulous arch in which the missing teeth have been or will be replaced by the fixed partial denture.
A partially edentulous arch in which the missing teeth have been or will be replaced by a removable partial denture.
An existing complete denture.

Key Concept:
The characteristic features that occur when an edentulous maxilla is opposed by natural mandibular anterior teeth, including loss of bone from the anterior portion of the maxillary ridge, overgrowth of the tuberosities, papillary hyperplasia of the hard palate’s mucosa, extrusion of the lower anterior teeth, and loss of alveolar bone and ridge height beneath the mandibular removable dental prosthesis bases – also called anterior hyperfunction syndrome (Combination Syndrome)(GPT8).
Underlying systemic disease
Post extraction bone scars
Displaceable mandibular ridge
Displaceable maxillary ridge