MAINTENANCE
It is a common public misconception that a restoration requires less care than a natural tooth; however the introduction of an interface between the restoration and tooth surface presents a ‘weak-spot’ that is prone to both biological and mechanical failure. It is important that for any intervention, a maintenance programme is developed for each patient to reduce future problems. Oral hygiene instruction and home care form major parts of a preventive programme for each patient, and can reduce the incidence of future disease1.
Whenever any restorative intervention has been undertaken, there is an implication that disease (caries) or mechanical failure has occurred. To place a restoration without considering these factors will expose the restoration to an uncontrolled and unstable environment with an increased likelihood of failure. A correct diagnosis is essential before any treatment and in all cases, aetiological factors should be controlled as much as is possible.
For example, if mechanical failure has presented as multiple fractures of teeth or restorations, provision of an occlusal splint to control and distribute the excessive occlusal forces would be of benefit.
Similarly, where failure is due to recurrent caries or there is a high caries risk, the importance of regular exposure to fluoride should be remembered and appropriate fluoride supplements (e.g. mouthwash) should be advised.
Although the above steps will help to avoid failure, deterioration of restorations is inevitable. All restorations will fail, i.e. dental restorations do not have infinite service life in normal clinical conditions.
Survival time of simple restorations has been shown, in several surveys, to be of the order of 5–10 years2–5. With high quality treatment and a good preventive programme, then restorations may remain 153
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serviceable and functional for considerable periods of time. However, as failure is likely to occur at some point, regular review and an observant/aware patient will help to detect problems at an early stage when simple remedial treatment rather than extensive treatment may be performed. The recognition, management and replacement of dental restorations is therefore a routine component of the provision of continuing dental care.
FAILURE
Although there are many studies addressing failure/longevity of dental restorations, many of these do not provide useful information, as the definition of failure is often not given. There is variation between studies with regard to definition of failure with a variation from minor deterioration to a need for operative intervention or replacement of a restoration all being cited. The adoption of criteria for evaluation of dental restorations set by the United States Public Health Service (USHPS)6 has helped to standardise assessment criteria, but there still exists a wide variation in the methodology of clinical trials available to support longevity figures for various types of restorations. Commonly identified risk factors2,3,7,8 for increased likelihood of failure of a restoration include gender (higher failure in males), presence of occlusal contact (worse marginal deterioration), number of surfaces (three surface restorations have up to 1.8× risk of failure compared with two surface restorations) and operator (failure rates vary between operators with many failures being due to poor technique).
Recognition of failure
Failure of a restoration may take many forms and may be due to major defects (such as fracture and loss of a portion of the supporting tooth or restoration) or may be due to minor defects such as marginal deficiencies, staining or microleakage. When a restoration has failed, but does not involve loss of restoration or tooth bulk, it is unlikely that the failure will be noticed by the patient unless there are symptoms or there is a visible aesthetic problem. This is apparent for both direct and indirect restorations9. A delay in treatment of a failed restoration may result in further damage to the tooth or render repair impossible and as such it is important that an appropriate maintenance programme for a patient with a restored dentition includes frequent
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recall appointments, at which deterioration or failure can be recognised at an early stage by a clinician.
Most marginal defects are directly observable. In addition to clinical examination, radiographs are a useful adjunct to identify interproximal marginal defects/deficiencies or caries that may otherwise go unnoticed10. Also given the incidence of loss of vitality of teeth with indirect restorations, especially long-term11, periapical radiographs may be useful to detect peri-radicular pathology.
It is easy to replace a failed restoration without considering the implications of failure, which are often underestimated. Situations such as sub-standard treatment, incorrect diagnosis (initially or of failure) or provision of restorations with a short life expectancy will all result in more frequent intervention. Quite simply, the implications of failure relate to cost, both in terms of economic implications as well as harm to the tooth.
Economics of failure
It is axiomatic that there is an economic cost implication in provision of any treatment, whether this cost is met by individual patients or is state funded. There are financial implications in treatment of failed restorations and also in preventing failure, and this should be transparent at the outset of treatment to both operator and patient.
The relationship between initial cost and longevity is not always obvious, and in some cases a more costly initial treatment option may prove to be more cost effective in the long term4.
Costs to the tooth
With any operative intervention there is a ‘cost’ to the tooth in terms of loss of tooth structure and trauma to the dentino-pulpal complex. This is true for any procedure, and loss of healthy tooth structure can be significant when restorations are removed for replacement, especially when tooth-coloured restorations are removed12. Two concepts of use are that of the ‘life cycle’ of a restored tooth, and that of the ‘stressed pulp syndrome’13. The first describes the (sometimes inevitable) progression from a minimal intervention to a larger and larger restoration eventually necessitating an indirect restoration – emphasising the cumulative destructive nature of multiple interventions. The concept of a stressed pulp arises from the supposed healing of the dental pulp following trauma during an operative procedure. With each traumatic event, the pulp heals with a degree of tertiary dentine formation
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and fibrosis within the pulp. Successive interventions leave the pulpal tissues more fibrosed and less able to respond dynamically to trauma.
Eventually, the pulp will be unable to withstand even a minor insult and may become non-vital with a relatively small intervention. These concepts suggest that whenever possible, the number of interventions during a tooth’s life span should be minimised and each ‘stage’ of a tooth should be prolonged and interventions minimised in order to prolong the overall life of the tooth.
REPLACEMENT AND REPAIR OF RESTORATIONS
Failed or defective restorations that are associated with a clinically significant loss of function, tissue inflammation, or pulpal pathology should be replaced, adjusted or repaired (if possible), providing such treatment can be expected to overcome the problem. Surface quality deficiencies alone do not constitute an adequate reason for replace-ment14. It must be remembered that the cyclic replacement of restorations is associated with loss of tooth tissue due to progressive cavity/
preparation enlargement and repeated insults to the pulp.
In recent years there has been a shift towards maintenance and repair15, rather than the replacement of the deteriorating yet serviceable restorations in patients who maintain a good standard of oral hygiene. These patients with favourable oral environment and low caries risk should receive minimum intervention.
As a clinician, one must be able to:
• Diagnose a failed restoration.
• Analyse the reason for failure.
• Design the repaired/replacement restoration.
• Efficiently remove failed restorative material.
• Apply/insert corrected restoration.
Management decision
Although a fault may be identified, operative interference may not be warranted. A minor defect of a restoration margin with no signs of caries due to microleakage is a serviceable restoration. All operative interventions carry risk of additional damage to remaining natural tissues and intervening in a situation such as this will result in unwarranted removal of healthy tooth structure. Where minor defects have occurred, it is often possible to adjust local features and avoid radical
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reconstruction for example, clear occlusal interference and remove ledges from restorations or make minimal marginal additions.
When a fault is present but is localised to one region of the restoration, then consideration should be given to repairing rather than replacing the restoration, such that the intervention is minimised.
Similarly, when caries is present adjacent to a restoration margin, then considering the lesion as a new/primary lesion and providing a localised repair will also act to preserve the health of the tooth.
Although evidence for survival of repaired restorations is sparse, there are reports of good short-term survival rates16,17. When possible the observable defect should not only be corrected but preventive factors established to reduce the incidence of recurrent problems. When such additions/repairs can be made the new preparation should be designed to be as much as possible within the old restoration and shaped so that it will afford sufficient extension to:
• Eradicate the old defect.
• Permit adequate operative access when inserting the new restoration.
• Provide sufficient resistance and retention form to retain the new restoration.
Removal of an entire restoration that has a fault may be necessary; however such radical retreatment must be undertaken in the light of cost–benefit analysis, which includes the strategic value of the tooth and the anticipated service life of the new restoration. During the removal of the old restoration, sectioning of fragments of the restoration rather than removing every bit (with attendant problems of time, vibration, visibility and over-extension) will help to minimise the amount of healthy tooth structure lost. The failed restoration should be studied to identify effective planes of section, for example, across the isthmus of old compound amalgams followed by sagittal sectioning of both key and box, thereby allowing the remaining pieces to
‘fall into’ the body of the preparation for convenient extrication.
Care should be taken when prising any remaining adherent pieces of the restoration from the preparation walls as excessive leverage may result in cusp/wall fracture. Replacement restorations are subject to the same principles of preparation design and associated operative techniques in their placement as are deployed for primary restorations.
In all cases in which a restoration is to be repaired or replaced, the likely cause of failure should be identified, the preparation modified and, if appropriate, the local environment modified (e.g. by removal
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of non-working interferences on the tooth/restoration in question) in order to ensure maximum life of the new restoration. In all cases, the preparation should be reassessed to consider its potential for clinical effectiveness, in some cases an extended, indirect or full-coverage restoration may be indicated. Blind repetition of the initial operative approach is likely to be followed by ignominious repetition of failure.
REFERENCES
1.
Axelsson P. and Lindhe J. Effect of controlled oral hygiene procedures on caries and periodontal disease in adults. Results after 6 years. J Clin Periodontol, 1981; 8: 239–48.
2.
Qvist J., Qvist V. and Mjor I.A. Placement and longevity of amalgam restorations in Denmark. Acta Odontol Scand, 1990; 48: 297–303.
3.
Qvist V., Qvist J. and Mjor I.A. Placement and longevity of tooth-colored restorations in Denmark. Acta Odontol Scand, 1990; 48: 305–11.
4.
Mjor I.A., Burke F.J. and Wilson N.H.F. The relative cost of different restorations in the UK. Br Dent J, 1997; 182: 286–9.
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NHS Centre for Reviews and Dissemination. Undertaking Systematic Reviews of Research on Effectiveness: CRD’s Guidance for Carrying Out or Commissioning Reviews, 2nd edn. NHS Centre for Reviews and Dissemination, University of York, 2001.
6.
Ryge G. and Snyder M. Evaluating the clinical quality of restorations.
J Am Dent Assoc, 1973; 87: 369–77.
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Akerboom H.B., Advokaat J.G., Van Amerongen W.E. and Borgmeijer P.J. Long-term evaluation and rerestoration of amalgam restorations.
Community Dent Oral Epidemiol, 1993; 21: 45–8.
8.
Gruythuysen R.J., Kreulen C.M., Tobi H., van Amerongen E. and Akerboom H.B. 15-year evaluation of Class II amalgam restorations.
Community Dent Oral Epidemiol, 1996; 24: 207–10.
9.
Djemal S., Setchell D., King P. and Wickens J. Long-term survival characteristics of 832 resin-retained bridges and splints provided in a post-graduate teaching hospital between 1978 and 1993. J Oral Rehabil, 1999; 26: 302–20.
10.
Faculty of General Dental Practitioners [FGDP]. Radiographs in dental caries diagnosis. In: Selection Criteria for Dental Radiography, 2nd edn.
London, FGDP(UK), 2004, pp. 41–52.
11.
Valderhaug J., Jokstad A., Ambjornsen E. and Norheim P.W. Assessment of the periapical and clinical status of crowned teeth over 25 years.
J Dent, 1997; 25: 97–105.
12.
Hunter A.R., Treasure E.T. and Hunter A.J. Increases in cavity volume associated with the removal of class 2 amalgam and composite restorations. Oper Dent, 1995; 20: 2–6.
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13.
Abou-Rass M. The stressed pulp condition: an endodontic-restorative diagnostic concept. J Prosthet Dent, 1982; 48: 264–7.
14.
Paterson F.M., Paterson R.C., Watts A. and Blinkhorn A.S. Initial stages in the development of valid criteria for the replacement of amalgam restorations. J Dent, 1995; 23: 137–43.
15.
Mjor I.A. Repair versus replacement of failed restorations. Int Dent J, 1993; 43: 466–72.
16.
Mjor I.A. and Gordan V.V. Failure, repair, refurbishing and longevity of restorations. Oper Dent, 2002; 27: 528–34.
17.
Cipriano T.M. and Santos J.F. Clinical behaviour of repaired amalgam restorations: a two-year study. J Prosthet Dent, 1995; 73: 8–11.
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