Minimal intervention dentistry and older patients part 2: minimally invasive operative interventions

Minimal intervention dentistry and minimally invasive dentistry

Minimal (or minimum) intervention dentistry is the complete holistic team-care approach to patient-centred prevention of disease and management of oral health in the long term. It is centred on managing the ‘dental caries’ process, first ‘controlling and curing’ the disease, and employing minimally invasive techniques when operative intervention is unavoidable. This concept is not a new one, given that the man frequently referred to as the father of operative dentistry, GV Black, stated that ‘The day is surely coming…when we will be engaged in preventive rather than reparative dentistry’ and there are textbooks on the subject listed as recommended reading for undergraduate students and qualified dentists alike.1^,2^,3 The breakthrough discovery of the acid-etch procedure by Buonocore in the mid 1950s laid the groundwork for the ability for clinical dentistry to adapt to a more conservative, minimally invasive approach to restorative dentistry.4 Despite the presence of MID in the dental literature, the application of this concept seems slow in its integration into general dental practice. There is no doubt that a more restrained approach to placing the first restoration in a tooth surface has a long-term beneficial effect for the longevity of the tooth.5 Unfortunately, many dentists in NHS practice feel inadequately reimbursed for preventive care to adults and this may be affecting the transition from dental surgeon to dental physician.6

Atraumatic Restorative Technique (ART)

For a number of older people reaching a dental surgery is extremely difficult or simply impossible. An estimated 410,000 older people live in residential and nursing homes across the UK.7 For these people and those unable to leave their homes, care may need to be provided on a domiciliary basis. When treating older patients with restricted mobility in the domiciliary setting, atraumatic restorative technique (ART) can be invaluable and has shown comparable survival rates to conventionally placed restorations.8^,9^,10 A meta-analysis showed that there is no difference in survival results between single surface ART restorations and amalgam restorations in the permanent dentition over three years.11 The technique involves the use of hand instruments only, to remove carious dental tissue, and restoration of the cavity with an adhesive material such as glass ionomer cement (Figures 1 and 2). This technique can also benefit elderly patients who have a dental phobia as it does not require the use of anaesthesia or rotary instruments. ART may also be aided by chemical caries removal systems such as Carisolv^® (MediTeam) (Figure 3). This 0.1% hypochlorite-based alkaline gel reacts with carious dentine which has undergone proteolytic breakdown of collagen, allowing for easier removal of infected tooth tissue with hand instruments.

Repair or replace?

Replacement of existing restorations accounts for 50–71% of all restorations placed worldwide.12 When treating secondary caries, it is more conservative to repair rather than replace a restoration unless the defect is very large.13^,14^,15 The replacement of restorations results in loss of tooth structure and ultimately a reduction in the longevity of the tooth as cavity sizes increase when restorations are removed.16 Depending on the reason for failure, complete removal of the restoration may be avoided. Repair rather than replacement slows down the rate of the restorative cycle and prolongs the longevity of the tooth. There is a ‘demographic bubble’ of patients now between 30 and 65 years who have retained much of their natural dentition but with high levels of dental disease treated by fillings and other restorations – a so-called ‘heavy metal generation’. The question of repair versus replacement will become increasingly important in the coming decades as these people grow older and these restorations begin to fail. The most recent Cochrane review on the replacement versus repair of defective amalgam restorations in adults did not identify any randomized controlled trials suitable for inclusion that compared the effectiveness of managing defective amalgam restorations by replacing them (with amalgam) versus repairing them (with amalgam) in permanent molar and premolar teeth.17 The need for research in this area was highlighted. They also identified a need for investigators to explore qualitatively the views of patients on repairing versus replacement of amalgam restorations and themes around pain, distress and anxiety, time and costs which are all relevant for effective patient care and satisfaction.

A repair or refurbishment procedure may be indicated in cases of localized marginal defects or staining, bulk fracture of a limited portion of a restoration or secondary caries which has not undermined the restoration (Figures 4 and 5).18 Given the benefits of the minimally invasive approach of repair rather than replacement, several dental material manufacturers have developed products for performing chairside aesthetic and functional composite resin repairs of ceramic restorations (Figure 6). Studies have demonstrated that the application of silane significantly increases the bond strength of the composite resin repair to the fractured ceramic, enhancing the clinical success of the repair procedure.19 Given that repair of a crown or a bridge is substantially more conservative than replacement, repair of ceramics should be attempted in the first instance of failure.20^,21^,22 The combined use of different mechanisms to enhance retention, such as sandblasting and hydrofluoric acid etching, will increase the chance of an effective and long-lasting repair. It has been suggested, however, that the risk posed by the intra-oral use of hydrofluoric acid may outweigh the benefits due to the potential of significant iatrogenic damage and harm to the dentist, dental nurse and patient.19 Many older patients will present with fixed prostheses which have served them well for many years and may be reluctant to have these prostheses removed, particularly if it is likely that they will be replaced with a removable prosthesis. It must be explained to the patient that the lifespan of the repair is unpredictable, but it is undoubtedly an attractive option when compared to complete removal of the restoration with a high risk of damage to the remaining tooth structure and increased financial expense.

Shortened dental arch (SDA) concept

Many older patients are partially dentate and may seek tooth replacement for functional or aesthetic reasons. The number of teeth needed to satisfy functional demands varies between individuals.23 In 1992, the World Health Organization stated that the retention, throughout life, of a functional, aesthetic, natural dentition of not less than 20 teeth and not requiring recourse to prostheses should be the treatment goal for oral health.24 Käyser proposed the shortened dental arch (SDA) concept in 1981 as a means of limiting treatment goals to provide a functional rather than a complete dentition.25 The benefits of accepting a shortened dental arch are considerable if patients are satisfied with the appearance and function of their dentition. Studies have shown that removable partial dentures increase the risk of dental disease and are not popular with patients.26^,27^,28^,29 Many patients, however, will not have the required number of occluding contacts to fulfil the SDA criteria and may need restoration to a functional dentition. Functionally-oriented treatment options include fixed bridgework, resin-bonded bridgework and implants (Figures 7 and 8). Unfortunately, many elderly patients have a negative attitude toward dental implants as they fear pain or medical complications. A focus group of elderly patients from Montreal and Newcastle reported that elderly people believe that information about implants is based on data from younger, healthier patients and hence cannot give them an accurate indication of what to expect.30 Even when elderly patients are exempt from charges, up to one third will refuse implant treatment.31

When the occlusion is favourable, resin-bonded bridgework is more conservative of tooth tissue than conventional bridgework. In addition, restoration to a SDA using resin-bonded bridgework has a positive impact on the oral health quality of life of older patients.32 A recent randomized clinical trial demonstrated that the provision of resin-bonded bridgework to a functionally oriented treatment group involved significantly lower costs than provision of removable partial dentures to a similar group of elderly patients.33 Patients also required fewer clinical visits which may be of benefit to patients who have difficulty accessing transport.

Resin infiltration techniques

Where operative intervention of a carious lesion is required, adhesive materials should be employed to enable minimally invasive cavity preparation with maximum preservation of dental tissues. Ultraconservative approaches, such as sealing over frank, cavitated lesions or resin-infiltration of early lesions, may be sufficient to arrest caries progress.34^,35^,36^,37 DMG America, an American dental technology company (DMG America, Englewood, NJ, USA) markets a resin infiltration system under the name of Icon^® (Figure 9). This concept was first developed in Germany, at the Charité University Hospital in Berlin, from in vitro studies on the penetration of resin into caries.38 Resin infiltration differs from surface sealing techniques as the resin infuses the porous demineralized enamel by capillary action, thereby stabilizing the lesion. The technique involves application of 15% hydrochloric acid gel to the tooth surface for two minutes, followed by a low viscosity TEGDMA (tri-ethylene glycol dimethacrylate) resin with a high penetration coefficient (at least 200 cm/sec). Before the development of resin infiltration techniques, the prevailing advice was to take a ‘watch-and-wait’ attitude to lesions of this type. This required multiple appointments in the dental surgery and strict long-term follow-up, which may be difficult for older adults who cannot easily access transport or leave their homes. The benefits of resin infiltration to a patient in this situation are clear. However, the clinical experience of dental practitioners using this technique is limited. The application of this system is quite different from that of applying a fissure sealant and the treatment of a single lesion by an experienced practitioner takes approximately 20 minutes. The system is highly technique sensitive, requiring complete isolation from moisture contamination and the radiolucent resin does not allow the finished result to be seen on radiograph. The treatment also does not currently have a code for NHS remuneration, which is likely to limit its incorporation into general practices.

Conclusion

The age of a patient should not be a determining factor when planning restorative treatment, however, as with any age group, it is important to consider the physical, social and financial impacts of any treatment we provide to our older patients. Minimally invasive operative techniques offer the opportunity to improve the long-term prognosis of the older dentition and to provide older patients with a functional aesthetic dentition for life.