Interactive treatment planning in toothwear: are we doing it right?

Question 1 – Would you be happy to increase the vertical dimension of this patient? If so, would you require a ‘pre-test’ before making change?

None of the expert panel expressed worries about increasing the occlusal vertical dimension (OVD) by the space necessary for the satisfactory aesthetics of the final restorations. The increase should be dictated by a combination of the ideal post-operative tooth length required and inter-occlusal space required for the palatal contour of the teeth. There were no concerns regarding the amount by which the OVD is increased.

The panel members were generally happy to use the Dahl concept and composite to achieve this or, if indicated, the use of a diagnostic wax-up upon casts mounted on a semi-adjustable articulator to fabricate conventional provisional crown restorations. As most of the occlusal aspects of the maxillary teeth were restored in this case, the vertical dimension of the overall occlusion was increased by a combination of direct composites on UR7, UR4, UR3, UL3, UL4 and UL5, and porcelain fused to metal crowns (PFMs) on the UR2, UR1, UL1 and UL2. The shared common view was that it was unlikely that the patient would need a ‘trial’ period of adjusting to the increased vertical dimension. The panel would reserve this for patients with a history of temporo-mandibular joint or muscle problems or those with a high level of occlusal awareness.

The vast majority of the dentists that completed the questionnaire (95%) reported that they were comfortable to increase the OVD of this patient. Most (80%) would not consider a trial increase of vertical dimension necessary but 20% would want to ‘test’ a trial appliance, eg a removable occlusal splint, before making a ‘fixed’ change to overall vertical dimension.

Question 2 – Would you have chosen the treatment plan proposed for the maxillary incisors, ie crown lengthening and elective root canal therapy of UR2, UR1, UL1 and UL2? (If ‘no’ what would you do differently?) (Figures 7–13).

The view from panel members was unanimous. They did not share the view that elective devitalization and root canal therapy, to allow subsequent restoration with cast posts and cores of UR2, UR1, UL1 and UL2 was necessary to restore the maxillary incisors predictably. All panel members supported the need for the crown lengthening surgery (CLS) of UR2, UR1, UL1 and UL2; followed by either conventional PFM crowns (with metal on palatal surfaces being the ideal choice) or adhesive all-ceramic dentine-bonded crowns for UR2, UR1, UL1 and UL2. They expressed that ‘in their hands’ enough retention would be achieved with this procedure without the need for post cores. Some voiced the view that the adhesive ceramic restorations were more predictable on the grounds of the likely intrinsic erosive aetiology (evidenced by the history of the patient and the fact that the mandibular dentition displayed little wear).

Most experts felt that direct composite restorations would not be very predictable for UR2, UR1, UL1 and UL2 owing to their severe wear and lack of enamel on the palatal and palato-gingival areas. However, some felt that there was little to be lost by giving direct composite ‘a go’ and that such restorations could provide the first part of a two-stage approach.

The expert panel was generally happy to suggest PFM crowns for UR2, UR1, UL1 and UL2, in combination with an increase in overall vertical dimension and with the use of palatal metal as the long-term treatment modality for this patient.

Members of the audience and the web survey results disagreed with the expert panel on this issue. Half of the dentists who completed the web-based questionnaire agreed with the treatment carried out and would both root treat and crown lengthen UR2, UR1, UL1 and UL2. A good proportion of dentists in the audience felt that adequate retention and resistance form for UR2, UR1, UL1 and UL2 (single crowns) could only be achieved by the use of both crown-lengthening in conjunction with the post and cores in this particular case. It was expressed that retention challenges are different for worn teeth supporting single crowns when compared to bridges. It was suggested by some that this is an important area for future clinical research.

This marked difference in view of the web and audience survey to the generally united view of the expert panel may be a reflection of personal differences in experience and training. Those who have worked within different UK dental hospitals will often come across with strong and, at times, inflexibly held views on treatment planning. The wise clinician will enthusiastically embrace the practice, the different philosophies available, consider the available evidence and make up his/her own mind about which works best.

In an ideal world, there was agreement that good standard elective endodontics can be expected to be successful.6^,7^,8 Similarly, post crowns placed within single teeth with good ferrules, when done well, will likewise be expected to last well. Unfortunately, there is UK evidence that dentists commonly experience technical problems with posts, such as iatrogenic deviation and around 50% of such teeth are associated with radiographic evidence of peri-apical periodontitis.9 There is also evidence to suggest that, in the UK, we struggle to achieve technically gold standard root fillings, even for single-rooted teeth.10^,11 This may also support the general view of the panel of experts that it might be most sensible initially to avoid the additional risk to the long-term outcome of the UR2, UR1, UL1 and UL2.

Comment was also made that one could always consider the post-core option at the first failure cycle of the restorations provided with CLS alone, especially considering that the first failure cycle of post crowns is often complicated by root fracture, rendering the tooth unrestorable.

Question 3 – When do you decide that a worn tooth is too short to support a conventional crown (even with CLS) and that it should be either reduced for use with an over-denture abutment or extracted? (Figures 7 and 11).

The general view from the experts was that 3 mm of crown height (axial wall of the tooth preparation) is usually enough to retain a single crown.12 However, several commented that many worn teeth display uneven wear and that, as a result, each tooth needs to be assessed on an individual basis. The panel also commented that a short tooth in a parafunctional patient represented a greater challenge to future crown retention than a tooth damaged by erosion, highlighting the importance of accurate diagnosis prior to treatment planning.

There were marked differences in the opinions of those in the web-based survey, with 66% willing to use teeth shorter than 3 mm for the support of fixed indirect restorations. The web-based answers varied considerably: 7% of dentists indicated that anything below 5 mm would not retain a crown; 27% felt the cut-off was 3 mm; 33% felt it should be 2 mm and, surprisingly, 33% considered only heights below 1 mm as too short for a crown rather than an over-denture abutment.

The reasons for this may well relate to the fact that 50% of the surveyed dentists would also consider elective root treatment and the use of post-core restorations (in combination with crown lengthening), where a minimum cervical collar/ferrule of 2 mm is required.13 This approach may allow for very short teeth to be built up with fixed restorations, but it is likely in some patients to prove unpredictable, particularly in the presence of parafunction. With such an approach, additional tooth height is achieved from direct or indirect core material rather than from natural tooth tissue. Our discussion clearly established the need for clinical studies in this area to address the minimum height of tooth required to retain a direct and indirect restoration, especially as adhesive techniques may mean reduced need for conventional preparations aimed at increasing retention and resistance form.

Question 4 – Would you use direct composite resin on the palato–occlusal aspects of the maxillary canines and premolars? If ‘yes’ would you build them up ‘free-hand’ or with the aid of a diagnostic wax-up and matrix? (Figures 9, 10 and 12).

The general view of the panel supported the preference for the ‘free-hand’ direct composite approach to the build-up of the canine and premolar teeth. They were also keen to optimize the properties of composite by placing the restorations in some bulk, in combination with an increase in vertical dimension, as mentioned earlier and supported by the literature.14

The view was that direct composite was likely to perform well for these teeth owing to the presence of enamel and their moderate, rather than severe, level of wear. The personal choice of most panel members was free-hand application, with the added benefit of avoiding unnecessary resource allocation/making a cost saving. It was felt that familiarity with laboratory-based procedures during training makes clinicians more comfortable with building things up free-hand. There was some comment that present dental training involves less exposure to laboratory skills.

Only 35% of the web-respondents agreed with the panel's view and were happy to apply the composite by hand, with the majority (65%) preferring the use of a pre-formed matrix constructed from a pre-op wax-up. Some audience members made a valid point; a pre-formed matrix allows for a more convenient method of forming the palatal/lingual shapes of toothwear build-ups with direct composite resin and hence more careful control of the desired occlusal scheme.

Question 5 – How would you restore the palato-incisal wear of UL6 and UL7? (Figure 3)

In this case, the UL6 and UL7 were not restored as the use of fluoride applications and better oral hygiene improved the symptoms. The panel was split between the use of conventional and adhesive cast metal indirect restorations and composite resin.

Again, it was felt that there was little to lose (other than time and some cost) in using direct composite restorations first and then moving on to indirect restorations if they prove unpredictable. Of web-questioned dentists, 42% would use adhesive gold, 21% direct composite and 37% conventional ceramic +/- metal crowns. The panel favoured cast metal on the grounds of robustness and relatively conservative tooth preparation. Comment was made that, if PFM restorations were to be used, then metal and not ceramic should be used on the occlusal surface. There was clearly much support from both the panel of experts and the audience for adhesive cast gold to restore UL6 and UL7, with some evidence that they will improve the pulpal sensitivity present.15

Question 6 – Would your hospital department take on this patient for treatment?

This question was aimed at the dilemma of secondary care providing treatment for toothwear patients. Of the web-responders, 42% would accept (or expect acceptance) of this patient for treatment within a secondary care environment; 58% would refer back (or expect return) to the referring practitioner with a treatment plan. There was concern from the panel and audience that the NHS can no longer absorb such treatment loads, as there are other more important priorities, such as cancer, trauma, developmental disorders and severe medical compromise. In this respect, what the Restorative Dentistry Team of an acute NHS hospital trust can provide is going to be very different from a dental teaching school with greater treatment capacity by under-and postgraduate students.16

There was discussion about improving the availability of specialist prosthodontists to the NHS (within Managed Clinical Networks). It was agreed that toothwear patients are time-consuming and expensive to treat within secondary care environments. As a result, 21st century dental practitioners will need to have the skillsets to treat such patients within their practices. Toothwear and the restoration of compromised dentitions will remain a big part of UK dentistry for the foreseeable future.

The point was also made that there needs to be an incentive within any future NHS General Dental Services contract to allow such patients to be managed within primary care. For instance, a specialist in primary or secondary care could provide the crown-lengthening surgical aspect of care for this patient and the referring general dental practitioner could undertake the remainder of the treatment.

In addition, the trend is towards adhesive technology and the broad acceptance across the UK that the Dahl concept is safe and allows many wear patients to be treated in a simpler and cheaper manner.17