may cause a lack of retention in function, as the functional sulcus shortens and displaces the denture base. When considering partial dentures and implant-supported overdentures (ISOD), retention becomes a much more active concept, through the use of direct clasps and retentive abutments. ISODs are considered further in Chapter 41.
Stability vs retention
I am often asked whether a denture can be stable yet unretentive – and vice versa. The simple answer is yes – to both. The technical challenge comes in ensuring that the prosthesis demonstrates both stability and retention. The key here is that the prosthesis covers the full denture bearing area – and accommodates functional movements within the periphery – the functional sulcus.
We will revisit the full anatomy of the maxillary and mandibular denture bearing areas (DBA) later – but some important anatomical and functional considerations for stability include:
The form of the edentulous ridge and palate
The degree of support offered by the ridges
The position of the polished surfaces in relation to the neutral zone (Chapter 24)
The degree to which the maxillary tuberosities are fully captured
The degree to which the disto-lingual anatomy is captured
Patients tend to learn how to improve the stability of dentures by improving muscle tone, tongue control and chewing habits. Whilst edentulous patients often have a habit of improving retention by holding dentures up with the posterior dorsum of the tongue, this appears to be a very patient-specific skill.
Important anatomical aspects for retention include:
Full coverage of the DBA
Developing an adequate border sealFully capture the maxillary tuberositiesFully capture the lingual anatomyAccounting for the insertion of buccinators into the retromolar pad
Ensuring that the denture is adequately extended, but not overextended, in function
Whilst the DBA and its extensions are very important, the position of the teeth is also critical, particularly in relation to the labio-lingual position of incisors on a lower complete denture. The concept of the neutral zone is very important and this will also be discussed later in Chapter 24. As well as the neutral zone, and impressions to record it, there are other prosthodontic techniques that can be employed to overcome challenges with fibrous ridges – such as:
The RPI design principle
The Altered Cast technique
Various mucostatic or mucocompressive impression techniques
These will be discussed further later in the book.
The gag reflex
This is discussed in more detail in Chapter 46 – however, it is worth mentioning at this early stage that the vast majority of patients presenting with a gag reflex are anticipating movement or loss of retention of their prosthesis. It may be that their current prosthesis is stable and retentive – however, most often I find that this is not the case. It is important to take the time to explain to patients that the best outcome is achieved if a stable and retentive denture is created first, which can then be used as a predictable tool for overcoming a gag reflex. Even in patients where counselling is required in order to overcome psychosocial triggers, a well-fitting prosthesis is necessarily the starting point.
4 Patient assessment for complete dentures
Arguably one of the most important elements of your patient assessment, is about taking the time to understand what the patient wants and why. It is also about making a judgement about how likely you are to succeed with your endeavours – there are a number of risk factors that can alter your chances of success and these should be discussed and recorded before the active elements of treatment begin. The majority of these factors are outlined below, largely as bullet point questions, but please do visit the recommended reading section for details of other academic texts which explore some of these concepts in further detail. Please also see the sample Complete Denture Assessment Proforma in Appendix 1.
The patient and the rationale for treatment
Why does the patient want new or improved dentures?
Is there any difficulty chewing or speaking?
Do the dentures cause pain or nausea?
Do the dentures cause gagging, and if so, is it immediate?
Are the dentures of a satisfactory appearance?
Have any of these problems got worse recently?
Prosthodontic history
What type of denture is the patient currently wearing?
How old is the prosthesis and where was it/they made?
For how many years has the patient been edentulous?
How many prostheses has the patient received before?
Is the patient willing to attend for the necessary appointments, including review appointments?
Clinical examination
Before considering removable complete prostheses, it is important to carry out a full and comprehensive extra- and intraoral assessment. The following aspects can then be considered (Figure 4.1).
Intraoral access – Can the full denture-bearing anatomy be palpated easily, and can the existing prostheses be easily inserted and removed from the mouth?
Tongue – Does this occupy a normal space, or does it exhibit lateral spread? Is there a habit of using the tongue to retain the upper denture posteriorly?
Gag reflex –
