Techniques for the restorative management of localized and generalized tooth wear

Tooth wear is a multifactorial problem that can be managed in several ways. The overriding principle for management of most dental problems is to keep it straightforward since restoration survival is finite. Planning for future failure and keeping treatment relatively simple is preferable to managing failing complex and/or extensive restorations. Furthermore, the countless different presentations in young and old, full arches or missing teeth, will require a personalized approach to restoration of the worn dentition. This article describes the application of different techniques and materials.

To increase or not to increase the vertical dimension of occlusion

The rate of progress of tooth wear will depend on aetiology, the duration and the frequency of its effect on the teeth. Fortunately, age-related, or physiological, tooth wear is probably a slow process at an average steady-wear rate on occlusal contact areas of enamel of 29 microns per year for molars and approximately 15 microns per year for premolars.¹ Maxillary and mandibular incisors were reported to wear by an average of 1.01 mm and 1.46 mm, respectively by 70 years of age, which is less than the wear rates for the aforementioned study on posterior teeth.² The net result of wear progression may be a reduction in occlusal vertical height (or OVD) with an increase in free-way space or maintenance of the OVD by the process of dento-alveolar compensation. In practice, the degree of compensated wear will depend on the intra-oral presentation: the number and position of missing teeth; patient age; aetiological factors; and the duration of effect. The determinants regarding whether an increase in OVD is needed are dental aesthetics, smile line and the space required for restoration.

A fundamental and initial step in the treatment-planning stage is the determination of the available space to build up worn teeth. It is easier to see this anteriorly than posteriorly. Closing the mandible along the terminal or retruded hinge axis into a retruded contact position (RCP) may result in a gap between upper and lower incisors sufficient for palatal and incisal composite build-up. Posteriorly, cupping on occlusal surfaces means that an enamel ring is higher than the exposed dentine such that the cup can be filled with composite up to and including the enamel rim without a significant OVD increase. Working within the existing OVD is a cautious approach, although a small increase in OVD of 1 mm had a protective effect on anterior composite restorations irrespective of the severity of pre-treatment tooth wear, tooth type or restoration failure.³

When the maxillary anterior teeth are worn and there is a normal free-way space or less, the classical treatment approach has been the removable Dahl appliance, which is an upper palatal bite platform against which the lower incisors occlude. Intrusion of the lower incisors and extrusion of the posterior teeth, possibly with some condylar repositioning, provide the anterior space for restoration. The removable appliance has been superseded by the placement of restorations using the Dahl concept, which in effect de-compensate by the same method of axial tooth movement.⁴ Compensation can present unilaterally depending on the habits that may have caused the wear, such as holding objects between teeth on one side of the mouth or having a preferred side to brux. Bizarre patterns of wear occur, and Figure 1 illustrates one such case.

When an OVD increase is required, should the desired increase be achieved in stages, for instance by use of a splint, or in one go? The conclusion in a review by Abduo and Lyons was that use of a removable splint to increase OVD for temporomandibular disorder (TMD)-free patients was not indicated because it might generate signs and symptoms related to splint wearing, rather than OVD increase.⁵ An important finding of the work by Dahl and others was that patients adapted to an increase in the OVD within 2 weeks.^6–8 The belief that uncontrolled tooth movement is unacceptable is less firmly held because of the adaptive capacity within the stomato-gnathic system. Furthermore, a change in the OVD does not result in TMD, although mild self-limiting symptoms may occur, which are without major consequence.⁹ Increasing the OVD with full-arch fixed restorations, however, is an option that is complex, lengthy and not reversible. Therefore, the first technique to be discussed in this article is the application of direct hybrid composite in both local and generalized wear cases.

Direct and indirect composite restoration and build-up

The European consensus paper firmly promoted reversibility and that restorative treatment for severe tooth wear should be as conservative as possible, embracing a minimally invasive strategy.¹⁰ Direct and indirect placement composite fulfils this by being additive rather than subtractive. Polyalkenoate or glass ionomer cement (GIC) can be applied to non-carious cervical lesions (NCCLs) where abrasion is the aetiology, but if acid erosion is involved, it would be best practice to avoid GIC because it is susceptible to acid dissolution. The role of the composite restoration is not just to replace lost tooth tissue, but also to protect underlying tooth substance. The composite is worn away and, in effect, sacrificed whenever physiological or pathological wear continues.

It is important to consider the survival and performance of direct composite restorations placed for tooth wear. In a systematic review of 10 studies that met the inclusion criteria, survival ranged from 50% to 99.3% for anterior and posterior direct composite restorations.¹¹ This compares favourably to survival of posterior composites placed for caries.

Three interlinked factors in the direct restoration of worn teeth by adhesive means are the nature of the worn surface, method of bonding and the choice of composite or other restorative material. Table 1 shows the materials and manufacturing processes available.

Enamel etching and bonding is well understood and predictable. Ideally enamel prisms should be etched end on to optimise resin tag formation down the length of the prism. But many worn surfaces will have a greater surface area of dentine than enamel, and therefore predictable bonding to dentine is also important. The composition of sound dentine is approximately 70% inorganic, 20% organic and 10% by weight water, which makes a strong stable bond that is not susceptible to hydrolysis and degradation difficult to achieve. Furthermore, dentine structure differs from the outer mantle to the inner circumpulpal dentine. Outer or mantle dentine is less mineralized and thus, mechanically more resilient to dissipate forces.¹² Dentinal tubules are cone shaped, and have the widest diameter and tubule density toward the pulp.¹³ In theory, therefore, etching and bonding to deep dentine will produce deeper resin tags and more resin tags than onto shallower dentine.

The tooth wear process, however, removes and alters dentine. Attrition can be a slow process, such that deposition of peritubular dentine leads to sclerotic dentine with less inherent water, less dentinal fluid and a highly mineralized surface (Figure 2). This will favour the use of etch and rinse systems or total etch compared with self-etch resins.

Figure 3 shows the compensated maxillary incisors with low gingival zeniths in contact with the opposing mandibular incisors. A high lip line may have required crown lengthening, but fortunately the patient had a low lip line. Bonded composites at the existing OVD obviated the need for a Dahl approach.

Eroded surfaces can have a partially demineralized, surface-softened layer of between 1 and 5 µm with exposed collagen fibrils. Erosion enlarges dentinal tubules, and peritubular dentine becomes rough and porous.¹⁴ This surface will also be altered by tooth contacts during function not to mention abrasives in the diet. A further consideration is the effect of tooth surface preparation on the dentine. A smear layer is formed on cut/abraded tooth surface, the thickness of which depends on the mode of preparation. Diamond bur and carbide fluted bur smear layers were reported to be up to 2.8 µm and 1.8 µm thick, respectively.^15,16 Etch and rinse removes the smear layer, whereas self-etch adhesives partially demineralize and expose collagen, resulting in a hybridized smear layer between the adhesive layer and the hybrid layer.¹⁷ There is no consensus on the ideal protocol for bonding to eroded dentine, but self-etch and universal adhesives based on 10-MDP (10-methacryloyloxidecyl dihydrogen phosphate) provide good bond strength because the acidic monomer dissolves the smear layer and the superficial part of the underlying dentine resulting in a hybrid layer infiltrated by the adhesive monomer.¹⁴ Furthermore, the functional monomer, 10-MDP, forms a stable nanolayer together with calcium salt–MDP deposition at the adhesive interface, increasing mechanical resistance and minimizing hydrolysis.¹⁸ Hybrid layer thickness depends, therefore, on the bonding system (self-etch vs total etch), dentine structure (superficial vs deep), and nature of the dentine (sclerotic vs eroded). The clinical challenge for the dentist is knowing what is the nature of the worn surface to which an adhesive is applied. Laboratory and clinical studies on bond strength and restoration survival in tooth wear cases are therefore important. Bonding techniques are discussed later.

Nano-hybrid composite was less susceptible to erosion and combined erosion/abrasion in vitro compared to a micro-hybrid composite.¹⁹ Micro-filled composites are polishable because of the greater resin content, and are more likely to undergo two- and three-body wear of the resin matrix, although hydrochloric, phosphoric and citric acid, without abrasion, had no effect on a micro-hybrid composite.²⁰ Several recent studies have supported the use of direct composite within and at an increased OVD to restore worn teeth.^21–26 A highly filled material is desirable in situations where occlusal loads are high, such as are found in bruxism, and nano-hybrid composite is the material of choice in wear situations.

Direct composite placement is probably the most conservative and least involved method to restore worn teeth. Whichever technique is chosen, the identification of risk factors and behavioural change by the patient is ideally required, but not essential prior to treatment. Not all patients will be compliant, so a pragmatic, sensible approach to management may direct the dentist to the most conservative treatment anyway. In the author's experience, many patients want to improve their appearance, but do not necessarily want a ‘Hollywood’ smile. Older patients are often partially dentate and may not have worn dentures, but have reasonable function. Discussion with the patient regarding their concerns and expectations is always the first step in planning. Some degree of compromise will be appropriate to provide a personalized treatment plan, and patients should be informed of any difficulty regarding treatment.

The extra-oral assessment of the lips at rest and on smiling can indicate difficulty. A low lip line favours a more conservative approach whereas a high lip line showing gum margins and attached gingiva may mean elective crown lengthening periodontal surgery is needed, which risks black triangles and an unfavourable crown-to-root ratio. The smile arc refers to the curvature of the lower lip, which should follow the upper incisor edges and be slightly inferior.²⁷ Wear flattens this curve, which is unaesthetic.

The decision on how to approach the worn dentition depends on the site, extent and severity of the wear. Localized wear is easier to manage than generalized wear. Anterior tooth wear is often localized to the palatal and/or the incisal edges of the maxillary incisors and canines. The first step is to determine whether there is enough space to build up the worn teeth. Space between the upper and lower anterior teeth may not be present in ICP, but may be gained by closure of the mandible along the retruded axis of rotation into RCP. Even if only a millimetre is gained, this may be sufficient to add restorative material to the palatal aspects. Determining inter-occlusal space posteriorly is difficult. It may be helpful to ask the patient to bite into a piece of carding wax. After its careful removal, it is possible to estimate the space between the teeth. Articulated study casts facilitate planning, and act as record of the pre-operative status. Where anterior teeth require composite build-ups, it is often necessary to request a diagnostic wax-up and a matrix in order to visualize and optimise the aesthetics, but it is important that wax-ups are performed on duplicate casts.

Localized wear on a few posterior teeth may be amenable to direct composite freehand build-up without the need to take impressions. As mentioned previously, bonding to the enamel rim provides a durable seal and may obviate the need for an increase in the vertical dimension. Even if an increase of less than a millimetre is made, axial intrusion should occur with re-establishment of the OVD. Figures 4–6 show cases with varying degrees of anterior wear manged by direct composite using the Dahl concept.

Occlusal considerations

In cases where the tooth wear is generalized, the question arises of where to start. Supporting cusps on unworn molars are in contact with their opposite number and maintain the vertical dimension and therefore should not be adjusted or reduced. Hence the BULL rule in complete denture construction, whereby the buccal upper and lingual lower cusps can be adjusted without changing the vertical. The upper palatal cusp and the lower buccal cusp in a normal Class I bucco-lingual relationship are the supporting cusps, also termed stamp cusps or functional cusps. The buccal upper and lingual lower being guiding cusps. Similarly, the lower incisal edges should be viewed as supporting cusps and the opposing palatal surfaces are guiding surfaces equivalent to guiding cusps. Consequently, the mandibular anterior teeth should be the first to be restored, then the maxillary anterior teeth.²⁸ This allows the anterior guidance to be either shallow or steep as the lower incisal edges are set first, and the anterior guidance can be established accordingly. Similarly, the lower posterior teeth are restored before the uppers. This approach is not set in stone, but acts as guidance for the dentist confronted with treatment in many, if not all, sextants. Figures 7 and 8 show mandibular incisors restored with direct composite despite the limited space. The rare case illustrated in Figure 9 presented with lingual erosive wear of the mandibular incisors, managed with strategically placed direct composite in order to reduce sharpness of the incisal edge.

Most of the literature on restoration of tooth wear has focused on direct composite. Indirect composite has some advantages over direct material placement: greater conversion resulting in less monomer and thus less risk of post-operative sensitivity; better wear resistance; better marginal adaptation and better marginal bond strength.^29,30 Restoration using indirect composite also has the advantage of less chairside time, but requires impressions and laboratory time. Artglass (Heraeus Kulzer, Hanau, Germany) indirect palatal composites (n=75) placed in 12 wear patients reportedly only resulted in minor failures in 13% of cases and were deemed effective over the 2-year observation period.³¹ The choice to use direct or indirect will depend on many factors, including the extent of wear, the patient's wishes and operator skill/experience. For instance, a few small localized cupped lesions will be amenable to direct placement, whereas all six worn palatal surfaces require significant chairside time to restore directly, and indirect placement may be more appropriate.

Ceramic crowns

Ceramic technology has improved considerably since the original porcelain fused-to-metal crown. Feldspathic porcelain is brittle and weak, but has excellent optical qualities. However, feldspathic resin-bonded or dentine-bonded crowns were placed to restore the eroded maxillary four incisors in a patient with bulimia nervosa and functioned over several years.³² Because this was an erosive aetiology rather than attritive, porcelain was used successfully. The fitting surface was HF acid etched and bonded to the dentine using an early adhesive resin. Feldspathic resin-bonded crowns were also used in the case shown in Figure 10.

Leucite-reinforced feldspathic material has better flexural strength and fracture toughness, but is still insufficient to withstand parafunctional or even functional occlusal loads (Figure 11). Glass-based ceramic, such as lithium disilicate, has excellent mechanical properties, but is still not advisable in parafunctional situations, although some manufacturers provide zirconia-containing lithium silicate with superior properties.³³

Zirconia is a polycrystalline ceramic without a glass matrix and exists in three phases: monoclinic; tetragonal; and cubic. It has the unique ability to stop crack propagation by transformation toughening. Under stress, a 3% volumetric increase occurs when the tetragonal phase changes to monoclinic, creating compression at the crack tip, thus preventing further crack propagation. The yttrium partially stabilized tetragonal phase of zirconia (Y-TZP) is used in dentistry, but the proportion of yttria varies from 3mol%, 4mol% or 5mol%, as does the proportion of tetragonal and cubic forms of zirconia.³⁴ The properties, and thus the indications, differ, such that dentists need to know which zirconia is best suited in a particular wear situation. The 5Y-TZP materials have greater translucency, but have lower flexural strength and lower fracture toughness than both 3Y and 4Y-TZP. Furthermore, transformation toughening is mostly lost in 4Y and 5Y-TZP as the cubic crystal content increases from 25% to 50%. They are recommended for indirect anterior restorations, but should be avoided in bruxists or when using crowns to increase the OVD in the Dahl approach because the high occlusal loads may lead to fracture. The so-called first generation of 3Y-TZP are stronger, but are opaque and thus need layering with feldspathic material, or the pre-sintered porous zirconia can be infused with metal oxides or metal oxide powder can be mixed with zirconia powder.³⁵ Most of the failed 3Y-TZP anterior crowns were in the bruxism group but nonetheless, 84.5% of the Lava (3M-ESPE, Seefeld, Germany) crowns performed well with an estimated mean survival time of 74 months.³⁶ Out of a total of 161 anterior zirconia crowns, 25 failed, of which seven suffered major failure or total debond, while the remaining 18 exhibited minor chips or delamination within the layered ceramic.³⁶ This was of no major concern to the patients who continued to function normally. Overall survival and success rates of monolithic zirconia restorations in bruxists and non-bruxists on teeth and implants were not significantly different, although veneered zirconia restorations and single-tooth abutments exhibited a higher rate of complications in the bruxist group.³⁷ A recent randomized controlled trial of 64 patients with extensive tooth wear compared survival and clinical performance of 362 lithium disilicate crowns with 351 3Y-TZP crowns over an observation period of up to 6 years.³⁸ The overall survival of both types of crown was 99.7%, with no difference between the two crown types. The authors concluded that adhesively bonded high-strength ceramics are the key factors for the long-term success of ceramic crowns in extensive tooth wear cases, regardless of the specific aetiology.³⁸ Modern materials, such as zirconia, have their place for restoration of the worn dentition, but dentists need to be aware of the specific design requirements (Figure 12). Excellent marginal fit with zirconia is illustrated in Figure 13, and Figure 14 shows what can be achieved with zirconia crowns. Tried and tested older materials, however, with anterior guidance on palatal metal surfaces and gold occlusal surfaces posteriorly are still advocated.³⁹ The use of full coverage crowns was deemed an important treatment option for tooth wear, particularly when composite fails.⁴⁰

Veneers, onlays and overlays

Anterior teeth

Resin-retained cast-metal palatal veneers in gold or nickel-chrome alloy were described in early reports on the management of palatal erosion.^41–45 Alumina blasting and oxidation pre-treatment of gold palatal veneers prior to cementing with Panavia 21 (Kuraray, Japan) improved durability.⁴⁵ Gold veneers on the palatal surfaces on the upper incisors risks shine through if the incisors are thin, but improvements in composite and adhesive technology have probably rendered this treatment modality less favourable.

The application of separate veneers on palatal and labial surfaces has been termed the ‘sandwich technique’. There are different variations to this approach with palatal veneers in indirect composite,⁴⁶ gold⁴⁷ or porcelain,⁴⁸ and labial veneers in composite or ceramic.^46,47 No major failure of the restorations was reported after a mean observation time of 50.3 months for the 70 palatal veneers and 49.6 months for the 64 feldspathic labial veneers placed on eroded anterior teeth in 12 patients.⁴⁶ Indirect composite veneers are also possible, with the advantage of improved wear resistance, although laboratory time is required. Figure 15 shows a case using indirect composite, although the outcome was less than ideal given the mid-labial margin. Design features for veneers include:

• Labial thickness of at least 1.0 mm (reduction in wear cases may not be needed);
• Chamfer margins;
• Finish the margin on enamel, if possible.

Posterior teeth

Onlays cover at least one cusp, while overlays cover all cusps, also termed full cuspal onlay. They can be used to build up worn posterior teeth and can be direct or indirect and in various materials, including gold alloy, non-precious alloy, composite, glass ceramic and non-vitreous polycrystalline ceramic. Metal onlays require less space than ceramic or composite and have high strength in thin section, unlike ceramic. The oxide layer formed after alumina (Al₂O₃) sandblasting on the non-precious alloy fit surface allows bonding to the tooth with a 10-MDP adhesive luting resin. High costs and the unaesthetic nature of metal are the main rawbacks.

Tooth-coloured partial restorations are conservative and have good medium-to long-term survival according to three recent systematic reviews, albeit none of the studies determined survival in the worn dentition.^49–51 Only 4% of inlays, onlays or overlays failed in 13 included studies owing to fracture/chipping, with a 95% survival over 5 years and 91% after 10 years of follow-up, and this was regardless of the ceramic material.⁴⁹ Tooth type did not affect survival rates, but restorations survived longer on vital teeth.⁴⁹ Although composite had lower, but acceptable survival compared with feldspathic ceramic reinforced with leucite or lithium disilicate, the authors opined that the use of composite onlays could be justified based on its cost–benefit ratio.⁵⁰ The systematic review by McGrath and Bonsor reported that the survival of direct resin composite onlays and indirect tooth-coloured onlays ranged from 73.1 to 100% of the included studies, with most studies (21/30) having survival rates over 90%.⁵¹ A randomized controlled trial of CAD/CAM lithium disilicate onlays, termed ultrathin occlusal veneers, compared with direct composite onlays on posterior teeth found that survival was not statistically significantly different for e.max (Ivoclar UK, Enderby) CAD compared with Lava Ultimate (3M Espe, St Paul, MN, USA). The pooled Kaplan–Meier 3-year survival rate for ultrathin occlusal veneers or onlays with a maximal thickness of 1.3 mm over cusp tips was a highly acceptable 88.4%.⁵²

Monolithic zirconia, which is not veneered with porcelain, can be used posteriorly where aesthetic concerns are less important. Inability to etch zirconia means that conventional retention and resistance forms may be required, although tribochemical sandblasting the fit surface with 50–60 µm silica-coated alumina at a low pressure below 2 bar increases the surface area for subsequent adhesion with a 10-MDP resin. The hardness of zirconia has the potential to wear opposing enamel, particularly if glazed. Polished zirconia, however, has been shown to be less abrasive than enamel and that surface treatment methods must be applied to minimize tooth wear.^53,54Table 2 shows the different methods of intaglio/fit surface preparation prior to bonding of ceramic. All fit surfaces must be clean and free of contaminants otherwise the bond is compromised.^55,56

Design features for all-ceramic onlays are:

• Rounded line angles to minimize stress concentration;
• No sharp edges;
• Chamfer margins of approximately 1.0 mm;
• Finish the margin on enamel, if possible;
• Occlusal thickness of at least 1.0 mm (occlusal reduction may not be necessary if increasing OVD);
• Any occlusal reduction should attenuate the surface, i.e. follow occlusal contours;
• Alumina-based ceramics require 2.0 mm occlusal thickness;
• Lithium disilicate requires 1.5 mm occlusal thickness;
• Zirconia thickness requirements vary. Occlusal thickness for translucent 5Y-TZP is 1.5 mm whereas opaque monolithic restorations need 1.0 mm.

Steps prior to bonding and techniques for bonding

Bonding techniques to the worn tooth, to glass ceramic, and to zirconia need to be considered, but first the steps for direct composite placement are discussed.

For a successful outcome to be achieved, the dental technician's involvement is important. A clear prescription outlining which teeth require wax-up, and the amount of increase in the OVD must be included on the laboratory prescription. Technicians working in a dental laboratory far from the surgery will need as much detail as possible (Figure 16). Often an edge-to-edge incisal relationship is required, and a thick or wide incisal edge (Figure 17) will provide a relatively flat anterior guidance reducing off-axial forces and keeping composite build-ups under compression, which is preferable to tensile forces.⁵⁷ Waxing-over the remaining labial enamel means a better composite bond, the so-called ‘composite bandage’, which should provide longer survival. For a full depth of cure, the thickness of wax should not exceed 3.0 mm.⁵⁸ Matrix techniques have been reviewed recently, but the material must be translucent to facilitate curing.⁵⁹ The lab card will need to have all these details.

Bonding to enamel is more predictable than to dentine because of dentine's heterogeneous composition with a higher water and organic content. For direct composite, the enamel margin on labial surfaces should Ideally be bevelled which will:

• Remove any aprismatic enamel;
• Expose prisms end on, resulting in the optimal Type I etch pattern;
• Graduate the composite from the body of the restoration to its margin and improve aesthetics;
• If extending inter-proximally, contact points should be broken to aid polishing, inter-dental cleaning and reduce risk of caries.
• A fluted tungsten carbide bur will cut enamel resulting in a more suitable margin than a diamond bur which grinds resulting in a thicker smear layer (Figure 18).

The bond to eroded dentine was improved after roughening with a diamond bur.⁶⁰ This will:

• Increase surface area for bonding;
• Remove some of the salivary pellicle that resists acid etching;
• Pellicle removal will also improve wetting by the adhesive;
• Partly or wholly remove the demineralized (surface-softened zone) on eroded surfaces.

To roughen, run a slow speed stainless steel round bur across the dentine with light pressure, enough to see some dentine debris, as shown in Figure 18. If using an etch and rinse system, etch both enamel and dentine for 20–30 seconds, which will remove any smear layer and demineralize deeply, resulting in a hybrid layer that is thicker (up to 5 µm) than with self-etch resins (less than 1 µm).⁶¹ Hybrid layer thickness does not correlate with bond strength.⁶² Remember that hypermineralized dentine is acid resistant and the requirement to etch/condition dentine for slightly longer than recommended is acceptable. There were no complaints of post-operative sensitivity in a large clinical study using this protocol.²⁴Table 3 shows the steps needed when bonding direct composite resin.

The correct viscosity of the composite is vital to prevent slumping while syringing composite onto the worn tooth and into the stent. Conversely, some wide bore syringes hold a very solid composite, which is unsuitable. The dentist needs to use a syringeable nano-hybrid composite that is runny enough but firm enough to apply. When seating, the matrix must not be squeezed over the tooth to be restored, but some excess is desirable lest marginal gaps occur. PTFE tape on either side of the tooth being built up will prevent composite sticking to adjacent teeth (Figure 19).^59,63,64 The narrow ultra-fine diamond burs, as shown in Figure 20, are excellent for trimming excess at the gingival margin. Polishing and finishing should not take long because the shape and micro-anatomy should be replicated from the matrix. Figures 21 and 22 show what can be done using direct composite. Older patients often present with a heavily restored dentition, deranged occlusion and advanced wear as shown in Figure 22. Taking a pragmatic treatment approach, understanding patient expectations and accepting a degree of compromise can lead to excellent outcomes even when the dentition is seemingly failing. The older gentleman shown in Figure 22 was motivated to return to his GDP enquiring about further treatment and dentures.

Removable prosthodontics

Removable prostheses are indicated in tooth wear cases where teeth are missing. These cases are common in older patients with multiple missing posterior teeth and wear of the remaining anterior teeth, which is often advanced. The absence of posterior teeth or lack of posterior support means that the dento-alveolar complex does not compensate for any loss of OVD. Consequently, the free-way space is often increased. Partially dentate patients with missing posterior teeth and wear affecting the remaining anterior teeth typically present with non-compensated tooth wear and a loss of occlusal vertical dimension making it necessary to provide treatment with removable prostheses.⁶⁵

Three types of removable prosthesis are possible:

• Onlay denture covers the occlusal and/or the incisal surfaces;
• Overlay denture as above, but additionally cover the labial/buccal surfaces;
• Overdenture covers the worn roots.

The provision of partial dentures in wear cases should follow standard steps and techniques. Most dentures will be tooth borne, but some, such as bilateral free-end saddle cases, may be tooth and mucosal borne. The dilemma regarding dentures is that older patients often present complaining of worn anterior teeth, but have never worn partial dentures to replace missing posterior teeth or attempted to do so, but failed to manage them. Reduced adaptive capacity in older patients means denture habituation is difficult. Dentists should warn patients about this, but mixing direct restorations and removable appliances is possible, although direct restorations may be under increased loads should dentures not be worn. Depending on the amount of occlusal wear, undercut for clasps may be absent on posterior teeth. Surveying casts is vital to establish a path of insertion and determination of how much undercut is available for denture retention. Mucosal-borne dentures are best avoided, particularly in cases requiring an increase in OVD.

Some workers have advocated a diagnostic phase with an acrylic occlusal splint with or without teeth, or a provisional appliance to test changes in the occlusal vertical dimension for aesthetics, phonetics and function but acrylic is bulkier than metal-based dentures and may not be well tolerated.⁶⁵

In an audit of 50 patient records treated for advanced tooth wear with dentures, fracture or wear of the incisal or occlusal surfaces was the common cause of failure. The authors concluded that regular maintenance was required.⁶⁶ Provision of chrome frameworks with occluding surfaces in metal may reduce the tendency for acrylic teeth to fracture (Figure 23) and extension of the metal backing palatal to teeth may also be beneficial.⁶⁷ Onlayed acrylic needs retention to the underlying metal framework as shown in Figures 24 and 25.

Patients with worn and depleted dentitions are usually in the older age group. Despite the psychological advantage in keeping teeth, dentures in such tooth wear cases can have significant issues as illustrated in Figure 26. Plaque control is more difficult with increased risk of caries and gingivitis. Regular recall is essential particularly in cases with overlay and overdentures.⁶⁸

Anterior teeth

The shape and size of acrylic anterior teeth is dictated by the amount of free-way space. Furthermore, the worn remaining crown of anterior teeth presents a difficulty for denture placement. Onlay dentures have a butt joint on the worn anterior teeth, which precludes their use in high lip-line cases, thus an overlay is indicated. But here too, difficulties can arise with the gingival fit of the denture as shown in Figure 27. Overlaying worn anterior crowns without a labial flange is aesthetically difficult. An overdenture on root faces flush with the gingivae is easier insofar as space for any metal framework and acrylic is often available, particularly if the patient is overclosed. The case shown in Figure 28 illustrates this point. Retained roots support an overdenture, but any bony undercut will prevent a fully extended flange.

Removable prosthodontics has a part to play in the restoration of a depleted and worn dentition and can provide excellent aesthetics as shown in the cases presented in Figures 28 and 29. Careful planning and close liaison with the technician will prevent some of the treatment problems that can arise. And as mentioned previously, regular patient review and reinforcement of plaque control is important to maintain the health of the remaining dentition.

Conclusion

The author prefers direct composite for restoration of worn teeth as it adheres (forgive the pun) to the minimally invasive philosophy and when failure occurs, repair or an alternative treatment option is hopefully still possible. The cases highlight the satisfactory results achieved with composite. Explanation of treatment options to patients is part of the informed consent process, and generally patients opt for less time-consuming treatment and most appreciate that restorations have a finite life span. An information sheet outlining what treatment has been done and the importance of good plaque control should be given to the patient at the end of treatment.⁶⁹

In a publicly funded health system such as the NHS, tooth wear treatment prerogatives are cost effectiveness, reasonable survival in the medium term (say 5 years), prevention of further wear and low maintenance. If we, as clinicians, act in the best interests of patients, then this is also true for private dental care. There is little, if any, practical or predictable benefit in drilling sound tooth structure on worn teeth.⁷⁰ The author has always taken a pragmatic, practical approach when treating patients, particularly older patients who typically have depleted and severely worn dentitions. The dentist–patient partnership relies on mutual understanding of each other's difficulties, expectations and possibilities. Most patients were content to have an improved appearance rather than a perfect one. Wabi-sabi, in Japanese aesthetics, means there is perfection in imperfection.