7 Restorative dentistry 3: replacing teeth

Solutions for missing teeth will vary depending on the number, their location and function, and the patient’s wishes. A minimally invasive approach is preferable where possible. 21 or more is considered the minimum number of teeth consistent with a functioning dentition. Replacement of missing teeth, therefore, isn’t always necessary. The Adult Dental Health Survey in 2009 showed that 86% of dentate adults had 21 or more natural teeth but this proportion ↓ significantly as age ↑.¹ In 2009, 6% of adults aged 16 or over were edentulous compared with 37% in 1968. These edentulous patients are also in the older age groups.

For those with insufficient teeth for satisfactory function and aesthetics, fixed or removable prosthodontic solutions will be needed. The use of bonding techniques and implants can help minimize unnecessary destruction of valuable tooth tissue.

Active listening in order to clarify the patient’s aims and expected outcomes is essential.

It is important to enquire about previous denture history (just because a patient is not wearing a denture does not mean that they have not had one) and assess the reasons for failure or success.

Medical factors can impact upon availability for treatment and ability to cope with dentures. Some drugs may ↓ salivary flow.

Other considerations may affect treatment, e.g. transport arrangements.

EO and IO exam, including a thorough assessment of any pathology, remaining teeth, existing restorations, periodontium, and edentulous areas (ridge form and extent, compressibility of mucosa). Assess tongue size, tonicity of the lips, and the volume and viscosity of saliva. An evaluation of any current dentures: what to copy and what to correct. Some patients present with a collection of unsuccessful dentures!

Radiographs/sensibility testing (especially of potential bridge abutments). Mounted study models and wax up in partly dentate cases.

are then listed and will allow appropriate treatment planning after considering the treatment options. If pre-existing denture problems are diagnosed, some could be addressed via modifications to the existing dentures prior to embarking on construction of replacement prostheses.

First consider whether benefits of replacing missing teeth (improved mastication, speech, occlusal stability, and aesthetics) outweigh disadvantages (↑ oral stagnation, tooth preparation, cost). If not, then replacement is C/I. An occlusion with first premolar to first premolar present in each jaw (shortened dental arch) is usually functionally adequate.

( Bridges, p. 268.) Have advantage that they are fixed. Resin bonded cantilever design are minimally invasive. Conventional bridges can have good appearance, but destructive of tooth tissue, moderately expensive and require lengthy clinical time.

Can be fixed or removable and have the advantage of avoiding preparation of natural teeth but involve surgical procedures and are expensive. They help maintain supporting bone and have a high level of predictability if carefully planned and carried out.

( Removable partial dentures—principles, p. 282.) Can be minimally invasive as only minor (or no) tooth preparation required but ↑ plaque accumulation/changes in composition. Damage to soft tissues and remaining teeth is exacerbated by poor denture design and/or lack of patient care. Can be a good option when there are multiple edentulous areas or as a training/interim appliance prior to F/F. Can be used to replace missing soft tissue and aesthetics can be very good but patients dislike removable prostheses.

Indicated for patients who have already mastered wearing a partial denture and whose remaining teeth have a poor prognosis.

Require patient compliance as well as good clinical and technical management for success. They can replace hard and soft tissue but patients tend to dislike them and successful denture control can be difficult for patients to master.

In the older, partially dentate patient it is important to assess whether the patient is likely to retain some functional teeth for the remainder of their lifespan. If this is improbable, some advocate providing F/F dentures while the patient is still young enough to adapt.

If replacement is indicated: ? fixed or removable prosthesis. A number of factors affect this decision (see Table 7.1).

These factors need to be favourable if expensive and complex bridge-work is required. Removable prostheses are indicated if general or local factors are less than ideal. Always consider implants or shortened dental arch therapy.

must be clearly explained to the patient with the advantages and disadvantages of each. This is essential in the management of expectations and to allow informed consent.

A prosthetic appliance that is definitively attached to remaining teeth and replaces a missing tooth or teeth.

A tooth which provides attachment and support for a bridge.

The component that is cemented to the abutments to provide retention for the prosthesis.

The artificial tooth that is suspended from the abutments.

The component that joins the pontic to the retainer. May be rigid or non-rigid.

The area of edentulous ridge over which the pontic will lie.

Number of units = number of pontics + number of retainers.

Prevents removal of the restoration along the path of insertion or long axis of the preparation.

The ability of the abutment teeth to bear the occlusal load on the restoration.

Prevents dislodgement of the restoration by forces directed in an apical or oblique direction and prevents movement of the restoration under occlusal forces.

The pontic is anchored to the retainers with rigid connectors at either end of the edentulous span. Both abutments provide retention and support. Both preparations must have a single line of draw.

The pontic is anchored rigidly to the major retainer at one end of the span and via a movable joint to the minor retainer at the other end (Fig. 7.1). The major abutment provides retention and support whilst the minor abutment provides support only. This design allows some independent movement of the minor abutment and has the advantage that the preparations need not be parallel.

Pontic is anchored at one end of the edentulous span only.

A tooth-retained, mucosal-supported bridge. The retainer and pontic are remote from each other and connected by a metal bar which runs along the palate. Usually an upper incisor is replaced from the premolars or a molar. It is useful where there is an anterior diastema or if the posterior teeth are heavily restored; however, they are often poorly tolerated. These are rarely used now.

Retained by resin composite ( Resin- bonded bridges, p. 278).

Combination of >1 of types listed.

Can be removed by dentist for maintenance.

All of these restorations have been used as retainers in conventional bridgework. They are listed in order from most retentive to least retentive. Wherever possible one of the first two should be used, as the failure rate of the last three is much higher. Post crowns should be avoided if possible, and onlays or inlays should only ever be used as minor retainers in fixed–movable bridges.

General factors must be taken into account, e.g. caries status and existing restorations. Also two other considerations specifically relate to bridgework—retention and support.

Retention offered by a potential abutment tooth depends on clinical crown height and the available surface area. Obviously, larger teeth offer more retention and should be chosen in preference to smaller ones. The teeth of both arches are listed in Table 7.2 in order of the amount of retention offered (if a full coverage restoration is used).

Three factors are important:

The teeth of both arches are listed in Table 7.3 in order of the support offered, assuming that the periodontal tissues are intact.

This type of pontic should make (minimal) contact with buccal aspect of ridge. Gives good aesthetics and is the most popular type.

Makes point contact with tip of ridge. Can be used for posterior bridgework.

Aims to address the issue of emergence profile in the maxillary anterior region. Has greater mucosal contact and applies light pressure to the underlying mucosa. Needs a smooth, convex surface to allow flossing. The patient must have excellent OH.

Does not contact saddle, therefore supposedly easy to clean but can still be challenging. Unaesthetic, therefore limited to molar replacement.

Extends over ridge buccally and lingually, therefore difficult to clean. Should not be used.

First control periodontal disease. Then ? bridge indicated. Fixed–fixed type of design preferable to splint teeth together. Consider fibre-reinforced resin composite fixed partial dentures for this specific indication.

This is the central abutment in a complex bridge that supports pontics on either side, which are in turn anchored to the terminal abutments. In this situation the pier abutment can act as a fulcrum and when one part of the bridge is loaded the retainer at the other end experiences an unseating force which can lead to cementation failure. To overcome this a stress-breaking element must be introduced, e.g. fixed–movable joint, or avoid pier abutments by simplifying the design.

Occurs most commonly following loss of a molar. There are several approaches if bridgework is planned:

The canine is often the keystone of the arch, and a very difficult tooth to replace. The adjacent teeth are poor in terms of the amount of retention and support that they offer and the canine is often subject to enormous stresses in lateral excursion (in a canine-guided occlusion). If a canine is to be replaced with a bridge the occlusal scheme should be designed to provide group function in lateral excursion—never canine guidance.

As always, thorough history and examination are required ( Treatment planning for patients with missing teeth, p. 264). It is essential to clarify the patient’s attitude to and expectation of treatment. They must be assessed for active disease due to poor OH or diet and for pre-existing TMPDS. The response to initial treatment to stabilize active disease should be monitored before embarking on definitive treatment. If bridgework is planned, the following stages are carried out:

Patients should be warned about these prior to treatment. Crown and bridgework is responsible for the greatest proportion of negligence claims against dentists.

Depending upon type and extent of problem:

Before replacement of a bridge is embarked upon, a careful analysis of the reasons for failure is necessary. Minor problems in an otherwise satisfactory bridge should be repaired if at all possible. Fractured porcelain can be repaired with one of the specialized repair kits available (e.g. CoJet™). Secondary caries or marginal deficiencies, if small, can be restored with traditional GI cement.

A survey of bridges placed by GDPs in Sweden found that 93.3% were still in service after 10yrs.³ The most common reason for failure was loss of vitality. This is not necessarily an indication for removal of the bridge because RCT can often be carried out through the retainer of the abutment.

To remove intact, try a sharp tap at cervical margin with a chisel or preferably a slide hammer. Orthodontic band-removing pliers can also be used but these require a small hole to be cut in the occlusal surface. If only one retainer is loose, support bridge in position while trying to remove it so that it does not bind.

Retainers can be cut through, but this will destroy the bridge.

This technique involves bonding a cast metal framework, carrying the pontic tooth, to abutment teeth using an adhesive resin. This type of bridge is almost exclusively used for cantilever adhesive bridgework, i.e. one abutment and one pontic (Fig. 7.2). Fixed–fixed designs have been problematic, with one retainer debonding being a common clinical finding. The resin bonds to the abutment tooth using the acid-etch technique and to the metal framework by either mechanical or chemical means. Fibre reinforced bridges are also available.

Chemical retention to a sandblasted metal surface is now used virtually exclusively. A dual-affinity cement (e.g. Panavia™ 21) is used, which chemically bonds to both enamel and non-precious alloys.

As for conventional bridgework. If orthodontic treatment is needed to localize space or upright adjacent teeth, it is advisable to retain with a removable retainer for at least 3 months prior to bridge placement.

Is usually cantilever. If a fixed/fixed design is used and there is a debond of one retainer, caries can develop quickly and undetected under this retainer. Fixed/fixed design may be used if periodontal splinting is required or retention required following orthodontics.

There is debate as to what is the ‘ideal’ preparation and some advocate no preparation. The need for preparation will be defined by the individual clinical situation.

NB Tooth preparation should usually be confined to enamel, and the framework should be designed with maximal coverage (to ↑ surface area available for bonding).

Following tooth preparation an elastomeric impression of the abutment teeth is taken plus an alginate impression of the opposing arch. At the try-in stage the bridge should be assessed for fit, aesthetics, etc., and then the fitting surface thoroughly cleaned with alcohol (assessment of occlusion may not be possible until after cementation). Contamination of the fitting surface with saliva must be avoided and cementation is best done under rubber dam. Following etching and washing of the abutment(s), and placement of a dentine adhesive system, the wings of the bridge are coated with Panavia™ 21 and the bridge seated into place and held firmly until set. Use of acetate strips and Super Floss^® at this stage will clear most of the excess cement and prevent it adhering to the adjacent teeth. The cement must then be covered with a substance known as OxyGuard^®, which prevents O₂ inhibition of the surface layer. After 5min or so the rubber dam is removed and any excess cement removed.

That part of a denture which rests on and covers the edentulous areas and carries the artificial teeth and gumwork.

Joins together component parts of a denture.

Resistance to vertical forces directed towards mucosa.

Components which resist displacement of denture.

Resistance to rotation about clasp axis by acting on the opposite side to the displacing force.

Axis around which a tooth- and mucosa-borne denture tends to rock when saddles are loaded.

Resistance to lateral movement.

Two or more parallel surfaces on abutment teeth used to limit path of insertion, and improve retention and stability.

Indicates the maximum bulbosity of a tooth in the plane of the path of withdrawal.

Edentulous area posterior to the natural teeth.

A device allowing movement between saddle and the retaining unit of partial denture.

A tissue-borne partial denture which can ‘sink’.

Has complete separation between tooth- and mucosa-borne parts.

Has a labial retaining bar or flange which is hinged at one side of the mouth and locks at the other.

Made in two or more sections which are then fixed together with screws or other devices.

Describes the pattern of tooth loss (Fig. 7.3):

I Bilateral free-end saddles.

II Unilateral free-end saddle.

III Unilateral bounded saddle.

IV Anterior bounded saddle, only.

Any additional saddles are referred to as modifications (except Class IV), e.g. Class I modification 1 has bilateral free-end saddles and an anterior saddle.

Describes the denture type:

Approximately 75% of the dentures provided in the UK have an acrylic connector and base. Although metal bases are generally preferred because the greater strength of metal permits a more hygienic design, an acrylic base is indicated for:

However, where financial constraints C/I a metal base, attention to the following may avoid the production of a gum-stripper:

can be made entirely of acrylic or have a sub-framework of metal overlaid by acrylic.

are an extension of the denture onto a tooth to provide support &/or prevent over-eruption. Occlusal rests are used on posterior teeth (usually over either the mesial or distal marginal ridge and fossa) and cingulum rests on anterior teeth. Rests may be wrought or cast; the latter is preferred for strength and fit.

provide direct retention by engaging the undercut portion of a tooth (Fig. 7.4 and Fig. 7.5). The action of a clasp must be resisted either by a non-retentive clasp arm above the maximum bulbosity of the tooth or by a reciprocal connector. Clasps can be classified by their position (occlusally approaching or gingivally approaching) or by their construction and material.

(cobalt chrome) clasps are stiff, easily distorted and liable to #. However, provided they are limited to undercuts of 0.25mm, the advantage of being able to cast them as an integral part of a denture framework offsets these drawbacks.

clasps are usually attached by insertion into the acrylic of a saddle. SS is the most commonly used alloy, but gold clasps are more flexible and easily adjusted (and distorted).

The stiffer the wire the smaller the undercut that can be engaged. This can be offset by reducing the diameter of the wire to ↑ flexibility (but ↑ the likelihood of #) or by increasing the length of the clasp arm (e.g. gingivally approaching clasp). Cast cobalt chrome can be too stiff for occlusally approaching clasps on premolar teeth. The actual design used depends upon:

In addition to joining parts of the denture together, the connector can also contribute to support and retention (Table 7.4).

Fig. 7.4 and Fig. 7.5 show the two most commonly used types of clasp.

P/P design is carried out after assessment of the patient and with reference to any previous dentures. A set of accurately articulated study models is essential.

Objectives:

If the path of insertion is at 90° to the occlusal plane insertion of the denture will be straightforward; however, where the teeth are tilted or few undercuts exist, an angled path of insertion may be advantageous. Which provides more resistance to displacement during function is controversial.

A survey line can then be marked on the teeth to indicate their maximum bulbosity in the plane of the path of withdrawal. This is done using a dental surveyor.

This presents a particular problem because of a lack of tooth support and retention distally, small saddle area compared to force applied, and distal leverage on abutment tooth in function (which ↑ with resorption). Possible solutions include:

Can sometimes avoid unsightly clasps anteriorly by the use of:

A horseshoe design, which utilizes guide planes for retention, may be indicated.

Acrylic mucosa-borne dentures can be rebased at the chair-side with self-cure materials, but difficulty may be experienced in removing the denture in the presence of undercuts, and the materials are generally inferior to the original denture base. Alternatively, P/P can be rebased in the laboratory by means of a technique similar to that used for F/F ( Rebasing, p. 304). Alternatively, make a new denture. For cast metal dentures an impression can be recorded of saddle area using an elastomer or ZOE, whilst holding denture by the framework. In all cases care must be taken to avoid the introduction of occlusal errors, e.g. ↑ OVD.

When the remaining teeth have a poor prognosis the transition from the partly dentate to edentulous state must be managed carefully. Patients must be warned about the effects of resorption and the need for early rebasing/replacement. Treatment planning must be thorough.

Flanged dentures are preferable as they afford better retention and make subsequent rebasing easier. However, where a deep labial undercut exists into which it would be impossible to extend a flange, the choice is either surgical reduction or an open-face denture. Most patients choose the latter.

These are similar to F/F except that the plaster teeth are removed and the cast trimmed to mimic the changes that will occur in the hard and soft tissues following extraction, before final processing.

See The extraction of teeth, p. 357 and Minor preprosthetic surgery, p. 400.

The resistance of a denture to displacement. Dependent upon: (i) peripheral seal; (ii) contact area between denture and tissues; (iii) close fit; (iv) viscosity/volume of saliva. Neuromuscular control has more to do with stability than retention.

The ability of denture to resist displacing forces during function. Influenced by forces acting on polished and occlusal surfaces, as well as the form of the supporting tissues.

The area where the muscular displacing forces are in balance.

These are, in order of ↓ prevalence:⁶

Tissues must be healthy before final impressions are recorded. If necessary use tissue conditioner in present F/F ( Tissue conditioners, p. 304).

Classically, two sets of impressions are recorded of the edentulous mouth. The purpose of the first is to record sufficient information for a special tray to be made in which to record the second or master impression.

These are recorded using an (edentulous) stock tray and alginate, elastomer (both preferable for undercut or flabby ridges) or impression compound. A line should be marked on the impression to indicate to the technician the desired extension of the special tray. In the upper, the posterior limit should be the hamular notches and the vibrating line, and in the lower the retromolar pads.

can be made in self-cure or light-cure acrylic. The space left for the impression depends upon the material to be used: ZOE = 0.5mm; elastomer = 0.5–1.5mm (depending on viscosity); alginate = 3mm. For trays with >1mm space use greenstick stops clinically to aid positioning.

These aim to record the maximum denture-bearing area, and to develop an effective border seal, the functional width and depth of the sulcus. The special tray should be modified by reducing any over-extension and the peripheries adapted by the addition of greenstick tracing compound. It is important that the trays are not perforated so that a peripheral seal with the upper tray can be demonstrated before taking the impression. Gently manipulate the patient’s soft tissues and ask them to slightly protrude their tongue to imitate functional movements.

A muco-compressive impression technique is sometimes advocated to give a wider distribution of loading during function and to compensate for the differing compressibility of the denture-bearing area, thus preventing # due to flexion. ZOE or composition is used. However, dentures made by this method are less well retained at rest, which is the greater proportion of time. Alginate is said to be more muco-static. Tissue adaptation following a period of use probably reduces the clinical difference between the two techniques.

This is used for recording the neutral zone in patients with limited natural retention for -/F.

Classically occurs under a F/- opposed by natural lower teeth. If mild, then an impression recorded with alginate or elastomer in a tray perforated over the flabby area may suffice. For more severe cases a two-stage technique is required, using a special tray with a window cut out over the flabby tissue. First, an impression is recorded in the tray with ZOE and the paste trimmed away from the flabby area. This is then re-seated and low-viscosity elastomer or impression plaster placed into the window to complete the impression. NB Combination type cases should have the dentures constructed on a semi-adjustable articulator to minimize occlusal displacing forces.

Tissue conditioner is placed inside the patient’s existing denture. After several days of wear a functional impression is produced.

When recording the occlusion with wax rims mounted on rigid acrylic or shellac bases the aim is to provide the technician with information for constructing trial dentures.

As head posture can affect FWS, position the patient so that the Frankfort plane is horizontal. A wax trimmer and a heat source are required to adjust the rims.

Ideally, the artificial teeth should lie in the space occupied by the natural dentition. The extent to which it is possible to compensate for a Class II or III malocclusion depends upon the retention afforded by the ridges. In the natural dentition the upper incisors lie ~10mm anterior to the posterior border of the incisive papilla. With resorption this comes to lie on the ridge crest, therefore the artificial teeth should be placed labial and buccal to the ridge, to give adequate lip support and a nasolabial angle of ~90°.

Posterior teeth should be narrow to ↑ masticatory efficiency. Low cusped teeth are preferred, but cuspless teeth are useful for patients with poor natural retention or a ‘wandering’ ICP. When considering the colour, mould, and arrangement of the anterior teeth, the patient’s age, facial appearance, and most importantly their opinion, must be taken into account. If you disagree about the suitability of their choice, document it.

Most textbooks advocate semi-adjustable or average value articulators for F/F dentures. However, most dentures are made on simple hinge articulators to the satisfaction of the majority of patients, probably because they are able to adapt to the occlusion that results. An average value type will give some degree of balanced articulation which can then be refined in the mouth and will help avoid the introduction of occlusal interferences, and is the preferred method.

Trial dentures are constructed by setting-up the prescribed teeth in wax on acrylic or shellac bases. Both the dentist and patient must be satisfied before the dentures are processed in acrylic.

Some advocate getting patients to sign an acceptance slip before going to finish.

This should be placed just anterior to the vibrating line on the palate, which can be assessed by asking patient to say ‘Aah’. The degree of compressibility of the tissues is assessed and the depth of the post-dam cut accordingly (usually ~1mm). The post-dam is recorded by marking the master impression with indelible pen and prepared on the upper cast with a wax knife in the shape of a Cupid’s bow.

This should include:

A new try-in will be required if large errors are being corrected or if any doubt still exists about the occlusion.

Some adjustment of completed dentures is inevitable following processing. On average, a 0.5-mm increase in height occurs and a slight shift in tooth contact posteriorly. The main steps are:

First, smooth any roughness and if necessary gradually reduce the bulk of the flanges in areas of undercut until the denture can be easily inserted without compromising retention.

The vertical dimension of the dentures is maintained by contact between the upper palatal and lower buccal cusps, therefore adjustment of these should be avoided if possible.

Verbal and written instructions should be given.

The patient should be seen 1–2 weeks after fitting to ease the dentures and adjust the occlusion. Localization of the cause of any irritation due to a flaw on the fitting surface can be helped by:

Stress the importance of regular review of all patients with dentures.

Review patients with F/F annually. Regular maintenance will help prevent damage due to ill-fitting dentures and will ↑ the likelihood of early detection of oral pathology.

As a result of resorption all dentures become progressively ill-fitting, leading to loss of retention and stability. Movement of dentures in function may result in:

All of these are exacerbated by wear of the occlusal surfaces.

The terms ‘rebasing’ and ‘relining’ are commonly used interchangeably. Strictly speaking relining is replacement of the fitting surface (e.g. with a temporary material) and rebasing is replacement of most or all of the denture base.

Rebasing is indicated where the only feature of F/F that requires improvement is the fitting surface; otherwise consider replacement F/F using copy method. For rebasing the material of choice is heat-cure acrylic ( Denture materials—rebasing, p. 662), but this necessitates the patient being without their dentures while the addition is being made. Self-cure acrylic applied at the chair-side appears attractive, but its properties are inferior. For a heat-cure rebase, a wash impression (ZOE or low viscosity elastomer) must be recorded inside the denture.

To avoid an ↑ in OVD, record the impression for one denture at a time.

An alternative method for inflamed tissues is to record a functional impression ( Functional impression, p. 297) over several days with a tissue conditioner (e.g. Visco-gel^®), in which case the resulting impression needs to be cast immediately.

These are resilient materials which give a more even distribution of loading and thus promote tissue recovery. They are particularly useful where ill-fitting dentures have caused trauma, as it is important to allow the tissues to recover before impressions for replacement dentures or a rebase are taken.

Relieve any areas of pressure on the fitting surface and reduce any over-extension. A minimum thickness of 2mm is required and the material should not be left for >1 week. Repeated applications may be necessary.

Tissue conditioners can also be used after pre-prosthetic surgery. They become less soft with time therefore they should be replaced at least weekly.

For patients who have very atrophic ridges and who struggle with denture wearing, a definitive soft lining aimed at distributing stresses more evenly to the denture bearing area may be helpful, e.g. GC reline™, Permasoft^®. GC reline™ may also be used to engage bony undercuts.

are indicated for:

It is wise to make a new denture first in acrylic and adjust the occlusion, before placing soft lining. A minimum thickness of 2mm is required, which may significantly weaken a lower denture necessitating placement of a metal strengthener on the lingual aspect. No material is ideal and soft linings are best avoided ( Soft liners, p. 662).

When new dentures are fitted the importance of regular, thorough cleaning, especially of fitting surfaces with soap, water, and a brush to prevent the build-up of plaque, stain, and calculus should be emphasized. Unfortunately, few patients are sufficiently diligent, due in part to being conditioned by advertising, to expect to use a denture cleaner.

Advise patients to clean their dentures over a basin of water to act as a safety net (see Table 7.5).

Hypochlorite solutions are effective for acrylic dentures when used overnight, but if used with hot water are liable to cause bleaching, therefore warn patient.⁷ The peroxide cleaners are popular but are ineffective if used for only 15–30min as the manufacturers advise. See Table 7.6.

The most common complaints are of pain &/or looseness, which can be due to denture errors or patient factors. The latter should be foreseen and the patient warned in advance of the limitations of dentures. Unless the cause is immediately obvious, e.g. a flaw on the fitting surface, a systematic examination of the fitting, and polished and occlusal surfaces (including the jaw relationship) should be carried out.

This can be due to a variety of causes, including roughness of the fitting surface, errors in the occlusion, lack of FWS, a bruxing habit, a retained root, or other pathology. Forward or lateral displacement of a denture due to a premature contact can lead to inflammation of the ridge on the lingual or lateral aspect, respectively. With continued resorption bony ridges become prominent and the mental foramina exposed, which can lead to localized areas of specific pain.

This more commonly affects the lower than the upper denture (Table 7.7).

This can be due to: (i) local causes: e.g. ↑ OVD or sensitivity to acrylic monomer, or be unrelated to the denture (e.g. irritant mouth washes, candidiasis); (ii) systemic causes: e.g. the menopause, deficiency states, cancerophobia, xerostomia.

See Table 7.8.

Check first that teeth are in neutral zone. If satisfactory, ↓ buccal ‘overjet’, i.e. reduce buccal surface of lower molars (provided normal bucco-lingual relationship).

Resorption is progressive with time, which is a good argument for avoiding rendering young patients edentulous. The mandible resorbs more quickly than the maxilla, which exacerbates the problem of retention for -/F. Management is dependent upon the severity of the problem and the patient’s biological age.

Apart from carelessness, this is usually caused by occlusal faults or fatigue of the acrylic due to continual stressing by small forces. Flexing of the denture can occur with flabby ridges, palatal tori, and following resorption. Notching of a denture, e.g. relief for a prominent fraenum, can also predispose to #. Treatment depends upon the aetiology, but in some cases provision of a metal plate or a cast-metal strengthener may be necessary.

Candida is a common oral commensal. It becomes pathogenic if the environment favours its proliferation (e.g. dentures, ↑ carbohydrate intake, antibiotic alteration of the bacterial flora) or the host’s defences are compromised Oral candidosis (candidiasis), p. 414.

Also known as denture sore mouth, a misnomer because the condition is usually symptomless. Classically, seen as redness of the palate under a F/- denture, with petechial and whitish areas. 90% of cases due to Candida albicans, 9% to other Candida, and <1% to other organisms, e.g. Klebsiella spp.

A common condition, having been reported in 30–60% of patients wearing F/F. It affects F more commonly than M, in a ratio of 4:1, and usually affects the upper denture-bearing area only.

is still not completely understood.

See Chronic candidosis, p. 414.

Successful function with complete dentures depends to a marked degree upon the patient’s ability to control them. This ability is learnt during a period of denture use. When replacement dentures become necessary, it is helpful if the new appliances require as little adaptation as possible to the existing skills. This is generally considered to be particularly important for the older patient. Not only may skills have been developed over a long period, but also the ability to relearn may be diminished. So-called denture copying techniques provide a more reliable method for provision of replacements.

Before undertaking treatment it is essential to decide which features of the previous dentures are satisfactory, and which require modification, and by how much. Consider:

A number of techniques have been described. They vary in the materials used, and these in turn affect the acceptability of laboratory work, and the clinical freedom to incorporate ‘corrections’. In general, copies of the old appliances are used as substitutes for record blocks, and as special trays. Typical method:⁸

Other methods use alternative materials (e.g. alginate for impressions of existing dentures, wax, and shellac to form the copy dentures). Choice will depend on acceptability to both clinic and laboratory. In no instance, however, is an all-wax copy regarded as being acceptable, since rigidity is inadequate for use as an impression tray.

In patients with successful P/P, for whom extraction of the remaining teeth is planned, the transition to complete dentures can be facilitated by using a copy technique.

Correct under-extended flanges with greenstick and then take impressions of the dentures with putty in stock trays (see F/F technique E Copying complete dentures, p. 312). Record an alginate impression of the opposing arch, if no denture is planned for that arch.

Wax/shellac or acrylic replica of partial denture is constructed.

Use the replica denture to develop the prescription and then record a wash impression inside the base with a light-bodied silicone. Record the occlusion using bite registration paste. Finally, take an overall impression in a stock tray with the modified replica denture in situ.

The impression is cast and used as a base for articulating the wax replica with the cast of the opposing arch. The teeth prescribed are then set up, and the wash impression retained in the replica, for the try-in.

Try-in and finish as for complete immediate dentures Immediate complete dentures, p. 292.

An overdenture (OD) derives support from one or more abutment teeth or implants by completely enclosing them beneath its fitting surface. It can be a partial or complete denture.

Alternatives include:

are useful for ↑ retention of dentures or bridges, especially in cases with tissue loss (e.g. trauma or CLP), but they ↑ loading on abutment teeth, and are expensive and difficult to rebase and repair. Usually of two parts, which are matched to fit together. One part is attached to the abutment tooth and the other to the denture. A variety of attachments are available, including stud/anchor (e.g. Rotherman eccentric clip), bar (e.g. Dolder), and magnets.

Since precision attachments require the highest technical skill and are highly dependent on patient and professional maintenance, it is wise to first use a basic OD and then reassess the need for additional retention. Hybrid dentures are partial dentures that utilize precision attachments (either intra- or extracoronal) on the abutment teeth for retention. Implants which are inserted in edentulous areas can be used with precision attachments to ↑ retention.

If abutment preparation is limited to crown reduction:

If precision attachments or copings to be used:

The most important are:

Implantology in restorative dentistry is based on the principle of osseointegration, i.e. a direct functional and structural connection between a load-carrying titanium implant with bone with no intervening connective tissue. See also Implantology, p. 402.

This concept has revolutionized tooth replacement in recent years (Fig. 7.7). Successful osseointegration depends on meticulous planning. There is little point in a successfully integrated implant in the wrong place!

There are two aspects to treatment planning:

Achieved by thorough history, clinical examination of hard and soft tissue availability, periodontal health, dentition, occlusion, available interdental and interocclusal space, and mouth opening ability. Smoking and untreated periodontal disease are risk factors for implant placement. Poorly controlled diabetes, immunosuppression, scleroderma, use of bisphosphonates are possible C/I to implant placement. Radiographic examination looks at the quality and quantity of bone and adjacent anatomical structures (e.g. ID canal/maxillary sinus), and any bony pathology. All prosthetic options (i.e. no treatment, removable partial denture, fixed bridge, or implant) are considered.

This uses the ‘top-down’ approach. This means deciding on tooth position first using wax-ups on mounted study models. If there is insufficient bone available in the right place then either bone augmentation is required or other prosthetic options need to be considered.

Bone augmentation may be achieved by onlay grafting, ridge expansion, sinus elevation, or distraction osteogenesis. The material used may be autogenous bone or allografts, xenografts (e.g. Bio-Oss^®) or alloplastic materials. Barrier membranes (e.g. Bio-Gide^®) may be used to support the graft material. Bone morphogenetic proteins may be used as bioactive mediators.¹³

The wax-up is used to produce a radiographic stent which is used to help plan the appropriate size and position of implant. A surgical stent is also made to help guide implant placement. Digital implant planning systems (e.g. SimPlant^®) are now available. These allow for 3-D planning and the production of surgical guides.

Careful technique is required to avoid overheating bone resulting in bone necrosis. There are many implant systems available. Some use a two-stage technique where the implant is buried while it integrates and has to be exposed at a later date. Others are transmucosal while they integrate.

Traditionally the time from placement to integration and loading has been accepted as 3 months in the mandible and 4–6 months in the maxilla. There is now some evidence that, in certain circumstances, implants may be loaded earlier than this.¹⁴

Once integrated (and, if necessary, exposed) an abutment is connected to the implant. This allows the prosthetic superstructure to be manufactured and connected via the abutment to the implant.

Implant superstructures may be single tooth crown, implant retained bridge, or implant retained overdentures.

Implant retained restorations need to be carefully maintained by the patient. The implant needs to be followed up long term clinically and radiographically by the clinician. Implant failure may be early or late. Early failure may be due to inadequate site preparation, overheating of bone, infection, premature loading, or lack of primary stability. Late failure may be due to overloading or infection (peri-implantitis). Literature shows maintenance of restorations will be an ongoing problem for the implant patient, e.g. # screws, clips, porcelain, acrylic.

From a chronological and social and healthcare planning perspective, being elderly means being >65yrs old. This is entirely different from biological age. Two factors are mainly responsible for the ↑ relevance of dentistry for the elderly: an ↑ in the proportion of the elderly in the population and the improvements in dental health that have resulted in more people keeping their natural teeth for longer. The proportion of edentulous adults in the UK fell from 37% in 1968 to 6% in 2009.¹⁵

Age changes are defined as an alteration in the form or function of a tissue or organ as a result of biological activity associated with a minor disturbance of normal cellular turnover.

↓ microcirculation, ↓ cellular reproduction, ↓ tissue repair, ↓ metabolic rate, ↑ fibrosis. Degeneration of elastic and nervous tissue. These result in reduced function of most body systems.

A ↓ in the thickness of the epithelium, mucosa, and sub-mucosa is seen. Taste bud function ↓. With age, an ↑ occurs in the number and size of Fordyce’s spots (sebaceous glands), lingual varices, and foliate papillae. Recent evidence suggests that stimulated salivary flow rate does not fall purely as a result of age. However, medications, head and neck radiotherapy or systemic disease can affect salivary output.

Enamel becomes less permeable with age. Clinically, older teeth appear more brittle, but there is no significant difference between the elastic modulus of dentine in old or young teeth. The rate of 2° dentine formation reduces with age, but still continues. Occlusion of the dentine tubules with calcified material spreads crownwards with age.

Toothwear is an age-related phenomenon and can be regarded as physiological in many cases. However, excessive and pathological wear can be caused by parafunction, abrasion, erosion (dietary, gastric, or environmental), or a combination of these factors ( Tooth wear/tooth surface loss, p. 244).

↑ fibrosis and ↓ vascularity mean that the defensive capacities of the pulp ↓ with ↑ age, therefore pulp capping is less likely to succeed. Also ↑ 2° dentine and ↑ pulp calcification.

↑ fibrosis, ↓ cellularity, ↓ vascularity, and ↓ cell turnover are found with ↑ age. Gingival recession has been previously thought to be an age change but is now known to be a part of periodontitis.

A ↓ in cell-mediated response and ↓ in number of circulating lymphocytes leads to an ↑ incidence of autoimmune disease as well as a ↓ in the older patient’s defence against infection. Also an ↑ in neoplasia is seen. Steroid treatment for autoimmune disease may complicate dental treatment.

Ageing involves both a physiological decline in function and dysfunction associated with age-related disease (e.g. strokes, parkinsonism, trigeminal neuralgia). A ↓ in acuity compounds the problem.

Hypertension and ischaemic heart disease worsen with age. Anaemia is more common in the elderly. In general, the greatest problems arise when a GA is required, or the practice is on the second floor.

Lung capacity ↓ with age and chronic obstructive airways disease ↑ in prevalence.

Diabetes is more common.

↓ bulk, slower contractions, and less precision of control occur.

Poverty, impaired mobility, ↓ taste acuity, and ↓ masticatory function can result in nutritional deficiencies in the elderly. These can manifest as changes in the oral mucosa.