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A Question of Space: Options for the Restorative Management of Worn Teeth K. DYER, R. IBBETSON AND N. GREY

Abstract: The prevalence of tooth surface loss has increased in recent years. The essence of management is an effective preventive regime; however, in many instances restoration may also be necessary. A number of strategies is available for creating sufficient space to enable restoration and several techniques for restoration known. This article reviews the significance of the vertical dimension of occlusion and describes the restorative management of a patient affected by severe toothwear. Dent Update 2001; 28: 118-123

Clinical Relevance: There is a variety of ways in which the restorative treatment of worn teeth may be managed. The reader should understand the principles underpinning the different approaches to restorative care.

oothwear, defined as the pathological, non-carious loss of tooth tissue, is becoming an increasingly common problem in restorative dentistry as more patients retain their natural teeth. The aetiology is well known and there is rarely a single cause; usually it is a combination of erosion, attrition and abrasion. When damage to the dentition has been significant and restoration is necessary, the main difficulties in providing treatment are the reduced clinical crown height and the lack of interocclusal space for the restorations. If traditional crowns are required, creating

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K. Dyer, BDS, MFDS RCPS, Senior House Officer, Edinburgh Dental Institute ,R. Ibbetson, BDS, MSc, FDS RCS (Eng.), FFGDP (UK), Professor of Primary Dental Care, Edinburgh Postgraduate Dental Institute, and N. Grey, BDS, MDSc, PhD, DRD, MRD, FDS RCS (Edin.), Consultant in Restorative Dentistry, Edinburgh Dental Institute, Edinburgh.

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preparations with adequate retention and resistance form and acceptable aesthetics can be difficult. This article addresses some of the problems and presents a case to demonstrate practical steps in treatment.

CREATING SPACE FOR RESTORATIONS A number of methods can be used to create space for restorations. These may be subdivided into methods based on using: ! a conformative occlusion, where the existing position of mandibular closure is maintained; or ! a reorganized occlusion, where the position of closure is altered.

Conformative Approach This is the situation where the existing

maxillary–mandibular relationship on closure is accepted. It can be suitable for restoration of a single tooth or small group of teeth. Examples are: ! reducing the teeth in the same or opposing arch; ! surgical lengthening of the crown. Reducing the Teeth in the Same Arch or the Opposing Arch This approach would be appropriate if there were adequate tooth tissue to allow for conventional preparation, which is rarely the case. Making a crown preparation on short teeth leads to broad, wide occlusal surfaces where stability is hard to produce and the preparations beneath these restorations generally have poor resistance form. It can make sense to follow this approach when making a solitary restoration; what seems less appropriate is to do the same thing repeatedly, ending up with a reconstruction done by degrees under less than ideal occlusal relationships. If repeated restorations are necessary it is sensible to adopt some of the strategies that allow restorations with better form and mechanical properties to be made. Surgical Crown Lengthening One way of exposing more tooth structure is by surgical crown lengthening. This is a significant undertaking for both the operator and the patient. The procedure is carried out on a number of teeth and generally involves an apical repositioning of the Dental Update – April 2001

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gingival tissues following removal of crestal alveolar bone. The aim is to provide increased tooth tissue for a longer, more retentive crown preparation. A period of healing, ideally 3 months for an anterior tooth, less for a posterior tooth, is required to allow the gingiva to stabilize at its new position. A potential difficulty with the final restoration of anterior teeth that have been surgically crown lengthened is poor aesthetics related to the dark triangular spaces interproximally.1 This is a consequence of the tapering form of the roots resulting in an increase in size of the embrasures between the teeth. Additionally, localized crown lengthening of a single tooth or several teeth can leave a poor final appearance due to the differential levels of the gingival marginal tissues after surgery.

Reorganized Approach This means changing the position of closure. There are several ways in which this can be achieved: ! altering the jaw relationship (mandibular repositioning); ! localized minor axial tooth movement; ! increasing the vertical dimension of occlusion. Mandibular Repositioning In this situation a new intercuspal position is created that coincides with the retruded axis position. This can provide the opportunity for creating space for anterior restorations. However, it is useful only for people who have significant mandibular translation between their retruded axis and intercuspal positions. Localized Minor Axial Tooth Movement There is a variety of methods that combine differential intrusion and eruption of teeth to create interocclusal space. It can be produced by several different approaches, including: ! direct composite restorations; ! orthodontics; Dental Update – April 2001

! fixed or removable bite planes; or ! the definitive restorations themselves. A significant amount of space can be created in a reasonable period of time without destroying tooth tissue. The procedure is generally well tolerated2 and patients seem to adapt to the altered mandibular position. The space is created by a combination of intrusion and dentoalveolar compensation. This method was originally described by Dahl et al.3 to create space to restore worn front teeth where there was little indication for restoration of the posterior dentition. They used a removable bite-raising appliance made of cobalt chrome as an anterior bite plane in the maxillary arch. Intrusion of the incisors and over-eruption of the posterior molars created a space that could then be used for the placement of definitive restorations. The need to increase the vertical dimension of occlusion, to create the space anteriorly necessary for restoration, was avoided and consequently the posterior teeth could be spared from restoration. The conservative nature of treatment employing relative axial tooth movement frequently lends itself to combination with adhesive restorative techniques. The increasing reliability of dentine bonding has made the direct placement of composite resin an acceptable method for restoration following toothwear, especially for replacing incisal edges and palatal surfaces of anterior teeth.4 Increasing the Vertical Dimension of Occlusion This is the placement of restorations that encroach on the interocclusal space. Traditionally it has been approached with caution as it was uncertain whether patients could tolerate the increase in their occlusal vertical dimension, which becomes manifest as discomfort from the muscles of mastication and pain in the teeth. However, this does not appear to be the case. In 1946 Thompson5 suggested that the rest position was constant throughout life, and therefore toothwear was

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compensated for by further growth of the alveolar process (‘dentoalveolar compensation’). Thompson’s suggestion was supported by research carried out on Anglo-Saxon skulls,6 which found that the distance between the occlusal surface and the alveolar bone crest remains constant throughout life; therefore a constant clinical crown height is maintained. The distance between the alveolar bone crest and the cementoenamel junction was found to increase, indicating that there is further eruption of the teeth throughout life. Another study used radiographs of women aged between 20 and 81 years.7 Throughout life the lower face height increases, which could be attributed to an increase in anterior dentoalveolar height, of equal proportion in the maxilla and the mandible. In the mandible, approximately one-third of the increase in height is due to an increase in incisor length, which the researchers attributed to either extrusion of the tooth or recession of the anterior bone margin. Knowing that the effects of slowly progressive toothwear are overcome by dentoalveolar compensation indicates that the lower face height does not reduce. Consequently, placing restorations at an increased vertical dimension would result in encroachment on the freeway space. Researchers have therefore concentrated on what happens when the occlusal vertical dimension is increased and whether damage occurs as a consequence. In a widely quoted article on this subject,8 patients were given acrylic resin splints to wear; these increased the vertical dimension of occlusion by 4 mm and produced a balanced occlusion. Patients were assessed for subjective symptoms, radiographically (to measure the change in interocclusal space) and electromyographically (assessing changes in the muscles of mastication). The conclusion drawn was that all the subjects created a new postural position of the mandible. There was no evidence of disorder of the muscles of mastication, such as tenderness to palpation. Electromyography (EMG) showed decreased postural activity with the splint inserted. The article 119

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Figure 1. Labial view of the teeth in occlusion before treatment.

emphasized that these results were achieved because occlusal stability was maintained and this should therefore also be established in patients where the vertical dimension of occlusion was altered. In an earlier study,9 clinical examination and the EMG activity of elevator and depressor muscles were used to investigate the rest position. It was found that a resting range, rather than a mandibular rest position, existed. The average resting range was 11 mm, as determined by assessment of the temporal and digastric muscles. It is therefore thought that if restorations are placed within this resting range and occlusal harmony maintained, the patient will adapt without experiencing problems, such as pain or discomfort. A further paper considered that jaw muscle motor behaviour was more dynamic and adaptable than had been believed.10 A report on a number of patients whose treatment had involved increasing the occlusal vertical dimension confirmed the acceptability of this approach.11 The evidence thus indicates that the vertical dimension of occlusion is not constant throughout life and that alterations are well tolerated. There does, however, appear to be a general consensus that such changes should be accompanied by ensuring occlusal stability at the new vertical dimension.

CASE PRESENTATION This describes the integrated use of a number of the strategies available for the restorative management of toothwear. 120

A 42-year-old man presented requesting treatment to improve the appearance of his short upper anterior teeth and the dark maxillary right central incisor (Figure 1). He reported that the wear had been progressing over several years. Five years previously he had experienced trauma to his face leading to the maxillary right central incisor becoming non-vital. This had been root treated, was asymptomatic and had a satisfactory radiographic appearance. The treatment plan integrated routine care with management of the worn teeth.

Examination Examination revealed toothwear affecting the palatal surfaces and incisal edges of the maxillary teeth. This was most severe on the incisors and canines (Figure 2). The tooth surfaces appeared smooth and shiny. There was a ‘cupped’ appearance, with the enamel appearing slightly proud of the dentine due to the preferential loss of dentine. Approximately half the clinical crown height had been lost and dentoalveolar compensation had taken place to maintain contact with the lower incisors: there was an edge-to-edge incisor relationship. The incisal edges of the maxillary teeth were level with the upper lip at rest, suggesting that the crowns required lengthening cervically and incisally to produce an acceptable appearance. The molars had been restored with large amalgam restorations. Investigations were carried out using mounted study casts, radiographs and dietary analysis. The toothwear was attributed predominantly to erosion with some secondary wear due to tooth-totooth contact. The maxillary arch was mainly affected.

might make provision of crowns more difficult or not feasible. 2. To improve the aesthetics. 3. To preserve tooth tissue remaining, allowing function to be maintained. The options for treatment were discussed with the patient, as: ! A period of monitoring, having established a preventive regime, if he did not want any further treatment at this time. The dietary analysis had shown a high intake of carbonated drink and fruit juice and the preventive regime included dietary advice and instruction. ! Provision of a simple partial overdenture. ! Fixed cast restorations in the upper arch. The patient was keen to have the appearance of his teeth improved and requested the fixed option. Study casts were articulated and a diagnostic wax-up of the proposed treatment made. Owing to the severity of the toothwear and the need to reconstruct a number of posterior teeth in the maxilla, fixed indirect restorations were deemed to be the most appropriate treatment. In order to help communication with the patient, a vacuum-formed matrix was made on a stone cast prepared from the diagnostic wax-up. This was filled with temporary crown and bridge resin and placed in the patient’s mouth. It was then removed, trimmed and replaced in the mouth to allow the patient to assess the likely outcome of treatment.

Treatment Aims The aims of treatment were: 1. To address the issues surrounding the cause of toothwear and prevent further destruction of the teeth. Of concern was that further toothwear

Figure 2. Palatal view of the maxillary arch showing the results of erosion. Dental Update – April 2001

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erupt into occlusion following completion of the restorative treatment.

Figure 3. The palatal incision at the time of surgical crown lengthening of the anterior teeth.

Treatment plan The definitive treatment plan was: 1. Provision of an occlusal splint to allow a stable mandibular–maxillary jaw relationship to be established. 2. Surgical crown lengthening 3| to |3. 3. Ceramometal crowns 3| to |3. 4. Gold onlays 6|, 5|, 4| and |4 as these teeth had large amalgam restorations. This would result in the remaining molar teeth being deprived of their occlusal contacts. The last component of the plan was: 5. To allow the remaining molars to

Figure 4. Labial view of the teeth in occlusion immediately following placement of the crowns.

Figure 5. Palatal view of the maxillary arch following treatment. 122

Procedure Surgical crown lengthening of the maxillary canines and incisors was necessary to increase the clinical crown length. This allowed more retentive crown preparations to be made, and the production of crowns of an aesthetically acceptable length. Crown lengthening was carried out under local anaesthesia and the patient then left for 3 months to allow healing to take place (Figure 3). First, the upper anterior teeth were prepared for ceramometallic crowns. Full labial reduction was made but the only palatal preparation necessary was a chamfer finish line. The incisal edges were smooth and rounded. Provisional restorations were made from the matrix of the diagnostic wax-up and cemented at the increased vertical dimension of occlusion. The posterior teeth that were to be restored in their original position were stabilized with glass-ionomer cement. The provisional restorations allowed assessment of the aesthetic and functional shape of the teeth before the final crowns were made. At a subsequent visit, the anterior crowns were tried in, adjusted and cemented with glass-ionomer luting cement. The 6|, 5|, 4| and |4 were then prepared for gold onlays. At a subsequent fit appointment, the onlays were heattreated and cemented with a surfaceactive composite resin-luting agent (Panavia 21, Kuraray, Osaka, Japan). The gold margins were finished with impregnated rubber cones and zinc oxide powder. Those teeth not restored were left to re-establish their occlusal contacts. It was anticipated that relative axial tooth movement would occur, with intrusion of the teeth that had occlusal contacts and eruption of those without (Figures 4 and 5). Within 1 month this had taken place and full occlusion of all the teeth was reestablished.

Outcome The patient was pleased with the result (Figure 6) and experienced no discomfort following placement of the restorations.

DISCUSSION This case has illustrated a number of issues surrounding the treatment of the worn dentition. Toothwear has certainly become a common problem, with more patients needing restorative treatment. The latest Children’s Dental Health Survey12 found that 32% of 14-yearolds had evidence of erosion on the palatal surfaces of their maxillary incisors. As many patients retain their teeth, with ever-increasing expectations, treatment is being demanded more frequently. The extensive nature of the work undertaken in this instance reinforces the need for early diagnosis that offers the opportunity for simpler forms of management. In this case, a moderately complex approach was required. The occlusion has been reorganized. The teeth needed crowns but first they required surgical crown lengthening to make available adequate tooth structure for reasonable retention and resistance form. It was also necessary to increase the length of the clinical crowns in a gingival direction to improve the aesthetics. The surgery provided approximately 2 mm additional crown length. The crowns were placed at an increased occlusal vertical dimension and an effort was made to ensure that occlusal stability was retained around the arch. However, this was not entirely possible. The decision was made to restore only a limited number of teeth

Figure 6. Labial view of the mouth following completion of restorative treatment. Dental Update – April 2001

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and consequently the 8|, |6 and |7 were not brought into occlusion: rather, the principal of relative axial tooth movement was employed so that teeth with occlusal contacts were intruded and those without erupted. This approach does call into question some previous statements discussed in the review of the literature–that moderate increases in the occlusal vertical distance are well tolerated as long as the criteria for an ideal occlusion were achieved. This was not the case in the treatment of the patient discussed here; at least not in the month after the last crowns were placed. Where relative axial tooth movement is employed, the stability of the occlusion and the desirability of the occlusal contacts should be re-assessed once the teeth are fully in contact.

BOOK REVIEW Prosthodontics for the Elderly: Diagnosis and Treatment. By Ejvind Budtz-Jorgensen. Quintessence Books, New Malden, 1999 (266pp., £59). ISBN 0-86715-368-7. Twenty years ago a book on ‘Prosthodontics for the Elderly’ would have majored on the construction of complete dentures. In this book, only 15 of the 266 pages are devoted to the subject. This is not because the edentulous no longer exist, far from it, it is just that a whole new set of problems associated with tooth retention have become, numerically, much more of an issue. Furthermore, the options for treating them have evolved to a level which were a distant dream just a couple of decades ago. In so far as it sets out to address the major issues which currently affect the prosthodontic treatment of older adults, this book succeeds. There are 10 chapters: 4 of them cover treatment delivery and associated practical issues, such as the mechanics of providing fixed and removable prostheses; the rest cover background information on epidemiology, age changes and function, as well as treatment planning and maintenance. There are plenty of illustrations, though Dental Update – April 2001

CONCLUSIONS A case report has been used to describe aspects of restorative management of worn teeth. It illustrates that a number of strategies can be combined to produce a satisfactory restorative result. It further reflects on the processes of increasing the vertical dimension of occlusion and relative axial tooth movement.

R EFERENCES 1. 2.

3.

4.

Ward VJ. Tooth surface loss. 11. Surgical crown lengthening. Br Dent J 1999; 187: 21–24. Gough MB, Setchell DJ. A retrospective study of 50 treatments using an appliance to produce localised occlusal space by relative axial tooth movement. Br Dent J 1999; 187: 134–139. Dahl BL, Krogstad OK, Karlsen K. An alternative treatment in cases with localized attrition. J Oral Rehabil 1975; 2: 209–214. Briggs P, Djemal S, Chana H, Kelleher M. Young adult patients with established dental erosion – what

these are rather small (fewer larger ones may have been more helpful). Whilst it is successful in raising the issues, it is less successful in the aims expressed in the preface to try to base it on the best evidence available. The lack of really good evidence for a lot of what we do in prosthodontics means there is a tendency, as in this book, to fall back on clinical experience. The literature is widely, though not comprehensively, cited, but the clinical conclusions could not be said to be evidence-based. With such a heterogeneous pool of patients and clinical conditions to deal with, it is impossible for a book like this to be comprehensive. Rather than attempt this, the author uses clinical cases to illustrate various points. In some chapters this works; the material on overdentures was particularly good. There are important areas though which are not covered in the sort of detail they merit. Adhesive techniques are barely mentioned, shortened dental arch philosophy is not discussed fully and the approach to treatment planning is rather old fashioned. Overall though, this is an honest attempt to deal with a diverse clinical subject and will prove valuable to clinicians or postgraduate students with a special interest in the oral health of the elderly. Jimmy Steele University of Newcastle Dental School

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should be done? Dent Update 1998; 25: 166–170. Thompson JR. The rest position of the mandible and its significance to dental science . J Am Dent Assoc 1946; 33: 151–180. 6. Newman HN, Levers BG. Tooth eruption and function in an early Anglo-Saxon population. J R Soc Med 1979; 72: 341–350. 7. Tallgren A, Solow B. Age differences in dentoalveolar heights. Eur J Orthod 1991; 13: 149– 156. 8. Carlsson GE, Ingervall B, Kocak G. Effect of increasing vertical dimension on the masticatory system in subjects with natural teeth. J Prosthet Dent 1979; 41: 284–289. 9. Garnick JJ, Ramfjord SP. Rest position. J Prosthet Dent 1962; 12: 895–911. 10. Hellsing G. Functional adaptation to changes in vertical dimension. J Prosthet Dent 1984; 52: 867– 870. 11. Rivera-Morales WC, Mohl ND. Relationship of occlusal vertical dimension to the health of the masticatory system. J Prosthet Dent 1991; 65: 547– 553. 12. Children’s Dental Health in the United Kingdom 1993. London: Office of Population Censuses and Surveys, 1993; p.74. 5.

ABSTRACT CAN YOUR DENTAL NURSE TEACH YOU ORAL MEDICINE? Hepatitis – Which Letters Pose a Threat? I. Douglas. The British Dental Nurses Journal 2000; Winter: 8–9. This article, intended for an audience of dental nurses, clearly and concisely sets out the current situation regarding the many variants of Hepatitis. I am quite certain, however, that most dental practitioners would also find the article extremely useful! It is suggested that: ! Hepatitis B virus poses a much reduced risk for the dental team because of successful vaccines. ! The ‘escape mutants’ which have caused so many problems may be limited by the impact of a new generation of vaccines. ! Hepatitis C poses a far more serious risk to the team, and the prospects for a successful vaccine are still remote. ! On current evidence, the latest hepatitis virus, HGV, seems to pose little cross-infection risk to the team or patients. Peter Carrotte Glasgow Dental School 123