Sheiham A, Steele JG, Marcenes W The impact of oral health on stated ability to eat certain foods; findings from the National Diet and Nutrition Survey of Older People in Great Britain. Gerodontology. 1999; 16:(1)11-20
van Waas MA The influence of clinical variables on patients' satisfaction with complete dentures. J Prosthet Dent. 1990; 63:(3)307-310
Smith M Measurement of personality traits and their relation to patient satisfaction with complete dentures. J Prosthet Dent. 1976; 35:(5)492-503
Hirsch B, Levin B, Tiber N Effects of patient involvement and esthetic preference on denture acceptance. J Prosthet Dent. 1972; 28:(2)127-132
John MT, Micheelis W, Steele JG Depression as a risk factor for denture dissatisfaction. J Dent Res. 2007; 86:(9)852-856
Fenlon MR, Sherriff M, Walter JD An investigation of factors influencing patients' use of new complete dentures using structural equation modelling techniques. Community Dent Oral Epidemiol. 2000; 28:(2)133-140
Fenlon MR, Sherriff M Investigation of new complete denture quality and patients' satisfaction with and use of dentures after two years. J Dent. 2004; 32:(4)327-333
Feine JS, Carlsson GE, Awad MA The McGill consensus statement on overdentures. Mandibular two-implant overdentures as first choice standard of care for edentulous patients. Montreal, Quebec, May 24–25, 2002.2002
Rashid F, Awad MA, Thomason JM The effectiveness of 2-implant overdentures – a pragmatic international multicentre study. J Oral Rehabil. 38:(3)176-184
Brennan M, Houston F, O'Sullivan M Patient satisfaction and oral health-related quality of life outcomes of implant overdentures and fixed complete dentures. Int J Oral Maxillofacial Implants. 25:(4)791-800
Heydecke G, Penrod JR, Takanashi Y Cost-effectiveness of mandibular two-implant overdentures and conventional dentures in the edentulous elderly. J Dent Res. 2005; 84:(9)794-799
Tallgren A The continuing reduction of the residual alveolar ridges in complete denture wearers: a mixed-longitudinal study covering 25 years. J Prosthet Dent. 1972; 27:(2)120-132
Jahangiri L, Devlin H, Ting K Current perspectives in residual ridge remodeling and its clinical implications: a review. J Prosthet Dent. 1998; 80:(2)224-237
Kelly E Changes caused by a mandibular removable partial denture opposing a maxillary complete denture. J Prosthet Dent. 1972; 27:(2)140-150
Shen K, Gongloff RK Prevalence of the ‘combination syndrome’ among denture patients. J Prosthet Dent. 1989; 62:(6)642-644
Palmqvist S, Carlsson GE, Owall B The combination syndrome: a literature review. J Prosthet Dent. 2003; 90:(3)270-275
Lechner SK, Mammen A Combination syndrome in relation to osseointegrated implant-supported overdentures: a survey. Int J Prosthodont. 1996; 9:(1)58-64
Crum RJ, Rooney GE Alveolar bone loss in overdentures: a 5-year study. J Prosthet Dent. 1978; 40:(6)610-613
Budtz-Jorgensen E Prognosis of overdenture abutments in elderly patients with controlled oral hygiene. A 5 year study. J Oral Rehabil. 1995; 22:(1)3-8
Kayser AF Shortened dental arches and oral function. J Oral Rehabil. 1981; 8:(5)457-462
Jepson NJ, Moynihan PJ, Kelly PJ Caries incidence following restoration of shortened lower dental arches in a randomized controlled trial. Br Dent J. 2001; 191:(3)140-144
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Complete loss of teeth from one or both arches is a disabling condition which is usually managed by a conventional removable denture. Rehabilitation may be poorly tolerated by patients, particularly in the lower jaw, and is more difficult in situations when the anatomy of the denture-bearing area is less favourable. These situations may require specific prosthodontic or surgical techniques, or a combination of both. Prosthodontic solutions involve special impression techniques and the use of soft linings and it is vitally important to manage patient expectations in such cases. This article describes prosthodontic management options for dealing with the fibrous (flabby) anterior ridge and bony exostoses.
Clinical Relevance: Although tooth loss in the UK is diminishing, it is nevertheless important that dental practitioners are able to demonstrate good prosthodontic skills for managing an ageing population. Surgical correction of anatomical defects may occasionally be employed.
Article
Complete dentures can be challenging for both patients and the dental team at the best of times. Even well-fitting dentures require the development of some skill on behalf of the user (habituation) to maximize success. Factors such as chewing ability, dietary selection,1 speaking, smiling and socializing2 are affected by the loss of teeth and wearing dentures. Unfortunately, by their very nature, removable dentures will be less stable than fixed prostheses, which may result in greater dissatisfaction for the user.
The proportion of the population in the United Kingdom retaining some natural teeth is increasing. The 2009 Adult Dental Health Survey reports that only 6% of the adult population is edentulous compared to 37% in 1968.3 While this is encouraging news, it belies the fact that the complete denture wearers as a whole are getting older and becoming more frail. Therefore, the challenge of providing well-fitting dentures to a sizeable population will remain for the time being.
A number of factors have been investigated to see if they relate to satisfaction with complete dentures. These include the quality of the residual oral tissues,4 patient personality traits,5 patient-dentist relationship6 and depression.7 However, many of these studies used relatively small groups of patients, so it is difficult to draw accurate conclusions. Studies involving larger population groups suggest that patient use of dentures is most closely linked with the quality of the prosthesis provided. Furthermore, a complete denture wearer with a severely resorbed ridge is less likely to be satisfied or use the dentures provided.8,9 While this may seem an obvious statement, it is a relationship that has only recently been demonstrated.
The ideal treatment of the edentulous mandible is the placement of a minimum of two endosseous implants followed by the provision of an overdenture.10 This form of treatment has been extensively researched and has been shown to improve function in the form of chewing ability,11 patient comfort, and psychological acceptance leading to an improved quality of life.12 Osseointegration in the anterior mandible is known to be successful and predictable and it may be argued that it offers a more cost-effective option in the long term compared with conventional lower complete dentures.13 Unfortunately, the initial cost of implant treatment is prohibitive for many people. Furthermore, there may be reluctance on behalf of the patient to undergo the necessary surgical procedures required.
Denture construction may be made more difficult by a number of factors relating to the anatomy of the denture-bearing area. Not only is it more difficult to construct a well-fitting denture in these situations, but there is a greater likelihood that support, retention and stability will be compromised. This article will concentrate on two such anatomical difficulties: the development of a fibrous ridge; and the presence of bony exostoses.
Fibrous ridge formation
Tallgren demonstrated the continual resorption of bone in patients who were followed for a period of up to 25 years following complete tooth loss.14 The majority of bone resorption occurs in the first two years after tooth loss and continues at a reduced rate thereafter. A number of factors have been studied in relationship to the degree and extent of bone resorption. Chief amongst these is the effect of local mechanical stress,15 for example in the situation where an edentulous arch is opposed by a fully dentate one (Figure 1). In some situations, accelerated bone resorption may be accompanied by fibrous replacement. This fibrous tissue provides poor support for complete dentures and is commonly referred to as a flabby ridge.
Figure 1.
(a, b) Advanced alveolar resorption in a patient with an edentulous upper arch with a near full complement of lower teeth. Note the ulceration and hyperkeratosis associated with the trauma from excess loading.
The formation of a fibrous (flabby) upper anterior ridge was described by Kelly who coined the term ‘combination syndrome’.16 In this ‘syndrome’ Kelly described the presence of four clinical features in patients who were edentulous in the upper jaw with retained lower anterior teeth. These are summarized in Table 1.
Feature
Possible aetiology
Comments
Fibrous ridge
Traumatic occlusal load
Prevalence of approximately 24%
Enlarged tuberosities
Supererupted maxillary molars (prior to extraction)
Masticatory forces
Weak evidence suggests that enlarged tuberosities are more common when a lower RPD is not worn
Papillary hyperplasia
Candida
Nocturnal denture wear
No evidence to support the presence of papillary hyperplasia
Extrusion of lower anterior teeth
Loss of occlusal contact
Soft tissue forces
Limited supporting evidence
There is little evidence to support this ‘syndrome’ as Kelly described a very small sample size and not all subjects exhibited every feature. Fibrous ridge formation is not an inevitable consequence of an edentulous upper ridge opposed by lower anterior teeth and is only seen in approximately 24% of such cases,17,18 according to a study of patients attending a dental school.
The mechanism for fibrous ridge formation is unclear. Bone is known to resorb under compressive load, but why should it be replaced by a layer of fibrous tissue in some situations? It has been suggested that this is an inflammatory mechanism which may be related to denture wear. An upper complete denture opposing lower anterior teeth results in excessive occlusal load on the anterior part of the underlying ridge, with consequent rotation of the denture and the potential for trauma to the underlying tissues. Interestingly, fibrous ridge formation has been demonstrated in the edentulous maxilla following the placement of implants in the anterior mandible.19
Management of the fibrous ridge
The best management for the fibrous ridge is to prevent its formation in the first place. This may be achieved by:
Avoiding total extraction of teeth in the maxilla;
Retaining upper anterior roots as overdenture abutments;
Placing maxillary implants at or shortly after tooth extraction.
Retaining roots as overdenture abutments has been demonstrated to reduce alveolar bone resorption20 (Figure 2). Root retention also improves proprioception and bite force in denture wearers and is a successful treatment modality if case selection is appropriate. Overdenture provision usually requires that endodontic treatment be carried out in the abutment tooth and requires careful maintenance by the patient. Caries is a frequent finding in overdenture abutments and patients are particularly at risk if they wear their dentures at night.21 The preservation of roots and alveolar bone may also compromise the space available for restoration and so this needs to be carefully planned, particularly if root surface attachments are to be employed.
Figure 2. Preservation of roots in the anterior maxilla will prevent the formation of a fibrous ridge. Cast copings may be required to protect the root face from fracture.
Restoration of the opposing arch provides even occlusal loading on the upper arch and can be achieved with a well-fitting denture. Meticulous planning and attention to detail can result in a prosthesis that is stable enough to meet the requirements of most patients. However, where lower anterior teeth are present there is less incentive for the denture to be worn. The concept of accepting a shortened dental arch22 and restoring the saddle areas with single unit cantilever resin-bonded bridges rather than a removable denture may be a more successful option.23,24,25 Here the provision of an occlusal table that extends far enough back to prevent tipping forces on an upper complete denture may reduce the tendency to fibrous ridge formation.
The problem of providing a denture on a fibrous edentulous ridge relates to the lack of available support (Figure 3). This may lead to pain under the denture-bearing area and rotation of the prosthesis, leading to loss of retention and stability. The problem is compounded by the extrusion of lower anterior teeth, thus compromising the occlusal plane. Techniques to manage the fibrous ridge include:
Surgical reduction of the fibrous tissue;
Impression techniques to minimize displacement of the fibrous ridge.
Figure 3.
(a) Extensively resorbed upper alveolar ridge. Note the pattern of resorption in relation to the fresh extraction socket. (b) Application of light pressure to the fibrous ridge results in distortion
Surgical reduction
Surgical reduction involves removing an elliptical wedge of fibrous tissue and may be combined with vestibuloplasty, to increase the depth of the labial sulcus, or removal of any associated hyperplastic tissue. Unfortunately, surgical techniques do not address the loss of alveolar bone and its associated problems so they are not commonly employed.
Impression techniques
Before considering any ‘special’ impression technique, it is important for the clinician to have a thorough knowledge of the anatomy of the denture-bearing area. This will not be discussed here but the reader is directed to a recent article which refers to this subject.26
Oral mucosa displaces when loaded under a denture and the degree of displacement will vary according to the thickness and quality of the mucosa. Displacement is also time dependent, the majority of it taking place soon after the load is applied, but reaching a maximum after a few hours, assuming that the load is maintained.27 In the upper arch, the mucosa overlying the palate provides a more suitable denture-bearing area than the fibrous ridge as the thinner, more tightly bound mucosa does not displace as much under load. The aim of the impression technique is therefore to displace the tissue in the palate, while the fibrous ridge tissue remains undisplaced, a so-called selective displacement technique (Figure 4). A number of techniques have been recorded in the literature28,29 which, broadly speaking, adhere to the following principles:
A primary impression is made using alginate or similar mucostatic material. Care must be taken to avoid distortion of the fibrous ridge during this impression stage;
The cast of the impression is marked to circumscribe the fibrous area and a custom tray is made which contains a window or relief of this area;
The tray is adjusted if necessary after trying in the mouth and border moulded as appropriate. A mucodisplacive impression of the non-fibrous area is recorded.
Figure 4.
(a) A special tray with a window over the fibrous tissue. (b) The tray is border moulded and a displacive impression of the non-fibrous area is made. (c) The fibrous area is recorded by syringing low viscosity impression material ‘through the window’. (d) The completed impression.
Material which flows into the region of the fibrous tissue is removed from the tray. The tray is then replaced in the mouth and the fibrous area is recorded by painting on or syringing an appropriate material, such as low viscosity silicone. This technique allows the fibrous ridge to remain undisplaced.
An alternative to this technique has been advocated by Watt and MacGregor30 and is particularly suited to extensive areas of fibrous tissue:
The primary impression is made as detailed before and a spaced custom tray is made;
The primary cast is soaked in water and an impression of it is made in compound using the custom tray;
The impression compound overlying the non-fibrous tissue is heated and border moulded as appropriate. Pressure is applied to the premolar region to displace the firmly bound tissue. The rigid compound overlying the fibrous tissue prevents the distortion in this area.
Management options for the fibrous anterior ridge are summarized in Table 2.
Treatment
Rationale
Comments
Surgical
Reduction of fibrous tissue
Reduce displacement of denture under load
Vestibuloplasty
Allow increased extension of denture base
Extensive resorption limits scope for deepening sulcus
Prosthodontic
Selectively displaced impression
Prevent distortion of fibrous tissue
Mucostatic impression of fibrous ridge may result in increased displacement under load
Provision of lower RPD
Provide even occlusal contacts to reduce load on upper anterior ridge
Incentive to wear denture may be low. A shortened dental arch with single unit resin retained cantilever bridges may be a more suitable option
Surgical plus prosthodontic
Upper implant stabilized prosthesis
Maximize stability of the prosthesis and prevent prevent displacement of the fibrous ridge
Limited bone availability may implant placement without grafting.
Jaw registration
It is important to ensure that there is minimal displacement of the denture base during jaw registration. Although more costly, a heat-cured acrylic resin, or other well-fitting hard base, allows an assessment of the available support and retention to be made and facilitates this stage. The aim of this stage is to allow provision of bilateral even contacts in centric relation. When setting the upper anterior teeth to avoid unwanted deflective contacts from the lowers, it may occasionally be necessary to position them in a crossbite (Figure 5).
Figure 5. The finished upper and lower in situ. The lower teeth on the left side were set in cross-bite as there was a perceived need to increase space for the tongue. Note the extrusion of the lower anterior teeth.
In spite of using careful technique, support and retention may still be compromised, so it is important to counsel patients about this at the outset of treatment and manage their expectations accordingly.
Bony exostoses
Palatal and mandibular tori
A torus is a benign outgrowth consisting usually of dense cortical bone covered by a thin layer of poorly vascularized mucosa. Tori are most commonly present in the palate but may also be seen in the mandible and are an incidental finding. They usually develop from the age of 30 to 50 and are thought to have both genetic and environmental predisposing factors.31 Studies have shown the prevalence of tori to be between 12 and 14% and, while they do not in themselves cause symptoms, they can make the denture construction difficult. This is particularly true in edentulous patients where full coverage of the palate is beneficial to maximize the support, retention and stability of the denture. The size, shape and position of the torus will determine whether it is likely to cause a problem (Figure 6). A flat torus can usually be covered by a denture base with light relief of the fitting surface. If the torus is larger or lobulated, a decision needs to be made as to whether to reduce surgically or avoid coverage. A palatal torus which is situated close to the junction of the hard and soft palate may interfere with the posterior palatal seal and require surgical removal.
Figure 6.
(a) Palatal torus in an edentulous patient which is anterior to the position of the posterior denture border. It is usually possible to cover a torus of this size with some relief of the fitting surface. (Courtesy of Professor Paul Wright). (b, c) Palatal torus and enlarged tuberosities in an elderly patient requiring an upper denture. It will not be possible to extend the denture onto the torus and surgical removal would be very traumatic.
Mandibular tori frequently interfere with correct extension of the lower complete denture so that their removal is more likely to be warranted (Figure 7).
Figure 7. Mandibular torus with buccal exostoses. Surgical removal will be necessary to allow correct extension of the denture base.
Enlarged tuberosities
Enlarged tuberosities, like tori, can cause problems with correct extension of the upper denture, resulting in a compromised border seal. It has been proposed that enlarged tuberosities, as with tori, may be associated with genetic factors and increased occlusal stress through parafunctional habits.32 Management of enlarged tuberosities will vary according to:
Site, ie unilateral vs bilateral;
Size of the tuberosity;
Displaceability of the overlying mucosa.
If the tuberosity is relatively small and the mucosa overlying it can be displaced, it may be possible to negotiate the undercut region without any special management techniques. A larger, but unilateral undercut tuberosity may be negotiated by adopting a rotational path of insertion whereby the denture is first engaged into the undercut area and rotated into the non undercut side. This may require slight relief of the fitting surface of the denture but has the advantage of retaining some mechanical undercut in addition to the border seal. Bilateral undercut areas may be blocked out on the master cast, if they are not too big, so that a fully extended base can be made (Figure 8). Alternative strategies include the use of soft lining materials to engage the undercut areas33,34 with the risk of increasing the bulk of the prosthesis; or underextending the base with the risk of making an unretentive denture.
Figure 8.
(a–c) Bilateral enlarged tuberosities in a patient with restricted mouth opening due to scleroderma. Surveying and blocking out the undercut area on the master cast allowed construction of a fully extended base and maintenance of peripheral seal. Care needs to be taken to ensure that the base does not interfere with the coronoid process of the mandible when the patient opens wide.
Other bony prominences
Patients with severe resorption of the mandible may demonstrate prominent mylohyoid ridges and/or genial tubercles (Figure 9). Although not true exostoses, these structures may nevertheless cause problems with denture construction. In most cases, relieving the denture in the offending area will be adequate and surgical reduction is rarely indicated. A denture flange which overlies a sharp mylohyoid ridge typically causes pain on chewing or swallowing. In order to relieve the denture correctly, it is placed into the mouth following the application of a thin layer of pressure indicating paste. The denture is loaded on the occlusal surface of the molar teeth and twisted from side to side, and it is a good idea to warn the patient that this may cause some discomfort. On inspection, the impingement of the mylohyoid ridge will be seen to be short of a correctly extended flange (Figure 10). This is an important point because the flange may unwittingly be overtrimmed with a resultant reduction in stability of the denture.
Figure 9. Prominent mylohyoid ridges (black arrow) and genial tubercles (yellow arrow) associated with a severely resorbed ridge.Figure 10. Lower denture with pressure indicating paste applied to disclose the position of a sharp mylohyoid ridge (arrowed). The denture can be relieved in this area without cutting the flange back.
Conclusion
Much of the evidence supporting conventional prosthodontic techniques is empirical. Undergraduate teaching in removable prosthodontics is reducing,35 while the population requiring complete dentures is getting older and perhaps more difficult to treat. Skilful management of the ‘anatomically difficult’ patients is required to maximize support retention and stability while ensuring comfort. Special impression techniques or the application of soft lining materials may be of use in selected situations. Oral surgery may occasionally be necessary so that a multidisciplinary route to care is adopted.
