Treatment planning over 50 years

There has been significant change in the practice of restorative dentistry over the last 50 years. I have practised for just a little over 40 of these years and have found current practice to be much easier and with improved outcomes compared to when I started. When new materials or techniques are developed, the hope is that they will be successful. This is judged by many factors including improved biological or financial outcome and survival, a simplified application or better patient acceptance. The evidence to support these perceptions lags significantly behind. Nevertheless, some techniques have good evidence and have been adopted into regular general or specialist practice. This article highlights some of the major changes that have changed how we provide treatment for our patients today. These include adhesive dentistry, bleaching, dental implants and the use of the ‘Dahl’ concept. This article looks at how these developments have changed our treatment planning, rather than giving a historical literature review or in-depth description of technique.

Adhesive dentistry

Fifty years ago, anterior teeth were restored with silicate cement and posterior teeth with amalgam. Gold inlays, onlays and crowns were considered superior restorations. Cohesive gold restorations were still provided by many practitioners. Anterior crowns were porcelain jacket crowns, and porcelain fused to metal crowns had just been developed.

Plastic restorations were provided according to Black’s principles of retention and resistance form, with ‘extension for prevention’ also considered good practice. In the late 1960s, early composites were an improvement for appearance, but did have post-operative sensitivity, were abrasive, and did not last because they stained easily. Cavity principles remained the same as for amalgam restorations. Every speck of caries was removed, even if this led to pulpal exposure, pulp capping or probable root canal treatment. Indirect pulp capping leaving a small amount of caries was permissible on occasion, and most deep cavities were lined with calcium hydroxide or a more substantial cement.

Significant improvements have led to the modern materials we use today. They now provide excellent appearance with a whole range of shades. Bonding to enamel has always been good, and now, bonding to dentine is reliable, although clinically not quite as predictable as for enamel.¹ With this improvement in bonding, cavity preparation has changed and many techniques are now described as ‘minimal preparation’ or ‘minimal intervention’.² Absolute caries removal in many cavities is no longer necessary in vital, asymptomatic teeth because residual carious dentine can be sealed in, reducing the need for endodontic treatment. Early fissure caries used to be treated with shallow amalgam restorations. This practice has been replaced by fissure sealants or small composite restorations. This change of approach has led to greater preservation of tooth structure.

The use of amalgam has declined. This was partly because of health concerns and disposal raised at the Minamata consensus.³ A greater influence was exerted because the use of composite has become easier, and the clinical performance has improved. Patients also much prefer the appearance. Dental amalgam is no longer taught in some dental schools. It has also widened the remit for the use of composite restorations, where crowns can often be avoided, in situations where there has been significant damage to teeth through trauma or tooth wear. This has tested bonding techniques to the full. Quite broken-down teeth can be successfully restored with composite resin, perhaps with a few judicious retention grooves. The use of dentine pins or elective endodontics and post retention has markedly reduced failure rates (Figure 1).

Resin-bonded bridges

In tandem with the improvements in composite and bonding, there have been corresponding improvements in bonding metals to enamel. In 1973, Rochette⁴ described a periodontal splint with a perforated framework that was mechanically retained with composite. This was later adapted to provide a tooth replacement in the form of a bridge.⁵ Later, in 1982, Livaditis and Thompson published on the use of a non-perforated etched framework bridge with a resin cement (Figure 2).⁶ The technique was modified to using sandblasting rather than etching the retainer surface, and allowed the use of nickel–chrome and heat-treated gold alloy. When this technology was adapted to the use of onlays or palatal backings, it obviated the use of pinlays used with conventional cements.

The use of resin-bonded bridges was further simplified by employing the ‘Dahl effect’⁷ (see later) where interocclusal space is not present. Success rates for resin-bonded bridges^8,9,10 have steadily increased when used in appropriate situations, and employing good design and cementation technique.^11,12 This has reduced the need to consider conventional bridges in the minimally restored dentition, which are destructive of tooth structure. These bridges have proved to be particularly successful when used to replace single units or small spans. Cantilever designs with a large abutment tooth supporting a smaller pontic enhances success. Nevertheless, not all dentists are confident using these bridges and in North America they are still viewed as temporary replacements.

Bright white teeth

A pleasing smile has always been desired by patients requesting treatment and by the dentists providing it. For many years the only option was to provide crowns on all the teeth involved in the smile. In the 1980s, attempts to provide acrylic or mastique veneers with minimal tooth preparation were unsuccessful. Porcelain laminate veneers were introduced in 1983 by Calamia (Figure 3).¹³ Many refinements have followed, and smile makeovers were popularized by a number of flamboyant dentists such as Larry Rosenthal.¹⁴ While some of these treatments were entirely justified, many were not.¹⁵ The longevity of such treatment could be good in skilled hands, and comparable to crowns,¹⁶ but was often overestimated and the maintenance requirements were rarely discussed appropriately. Evidence is lacking on how long veneers last a second time, and often, treatment moves on to the use of crowns. It should be remembered that a veneer preparation may remove up to 30% of the tooth by volume, and full coverage crowns up 70%.¹⁷

All-porcelain crowns usually provide the best appearance when compared to porcelain fused to metal crowns and allmetal crowns. However, until the past 10 years, these crowns were not durable and porcelain fracture was all too common. Lithium disilicate crowns now provide excellent aesthetics and reasonable physical properties, so they can be used for anterior teeth and premolars.

Molar teeth are subjected to the highest occlusal forces and zirconia crowns will be durable, but have only an adequate appearance because characterization remains difficult.¹⁸ Bonding of zirconia crowns remains under development and caution still needs to be exercised when clinical crowns are short and occlusal forces high, such as those found in the bruxist patient.

Scanning, rather than taking impressions, and CAD/CAM production has gone hand in hand with these porcelain developments. The development in this field has been rapid. In the same way composite has been edging out amalgam as a filling material, porcelain may be doing the same to metal and porcelain fused to metal crowns (Figure 4).

The advent of external bleaching of teeth¹⁹ has provided a way of brightening teeth and improving smiles without damage and with minimal side effects. Combined with the increase in adult orthodontics, and, in particular, the use of aligners, external bleaching has reduced the indications for veneers considerably. In many ways, external bleaching represents the perfect treatment, while also being cost effective. Very few developments have been accompanied by a reduction in cost to the patient.

Occlusion

Two useful additions to occlusal theory have been the Dahl concept and the shortened dental arch. These are discussed separately.

The Dahl concept

In 1975, Dahl²⁰ described an anterior metal bite plane removable appliance used to create anterior interocclusal space through orthodontic movement (Figure 5). The occluding teeth intruded and the posterior teeth overerupted to close the acquired interocclusal space. These movements occurred in a matter of months in young patients. These movements can be produced with posterior bite planes and affect multiple or individual teeth. The tooth movement is predictable and occurs in 96% of cases.²¹ In most clinical situations, the appliance or restorations are fixed to the teeth, which improves patient compliance. Perhaps the most common application is in the treatment of localized anterior tooth wear with direct or indirect composite restorations (Figure 6).^22,23 Restorations can be placed in both the upper and lower jaws depending on the severity of the tooth wear. Posterior teeth can be treated in the same way. The treatment can be repeated with slightly reduced survival, allowing the approach to last over 10 years.²⁴

This approach has been applied to the use of resin-bonded bridgework with equally successful results. It has obviated the need for occlusal adjustment of opposing teeth to create interocclusal space. The tooth movements are very small because the framework thicknesses are approximately 0.5—0.75 mm. Changes in the appearance are barely perceptible to either patients or clinicians.⁷

Shortened dental arch

For many patients, a premolar occlusion is satisfactory for appearance and function. It was also noted that many patients did not wear their lower partial dentures if they replaced only molar teeth in a free-end saddle situation (Kennedy classification I and II). In 1981, Kayser and Witter^25,26 developed the concept of a shortened dental arch as pragmatic healthcare advice to reduce the need for molar replacement in the form of lower partial dentures. They were keen to stress that molar replacement was needed to provide posterior support in the following circumstances:

• TMJ dysfunction;
• Periodontal drifting of anterior teeth;
• Severe tooth wear.

This has resulted in fewer partial dentures being made in these situations (Figure 7). Short posterior conventional or resin-bonded bridges have been suggested, but dental implants are much more likely to be successful if molar replacement is considered necessary.

Dental implants

Dental implants to replace teeth had been a goal for over a century. It was not until the advent of osseo-integration in the 1960s that it became a reality. Professors Brånemark and Schroeder were the pioneers in this field (Figure 8).^27,28 Originally, the aim was to help edentulous patients who were ‘maladaptive’ and could not wear their complete dentures. Two dental implants and an implant overdenture is now recognized as the treatment of choice for failed mandibular dentures.^29,30 The long-term survival studies herald from this time, and it was much later, in the 1980s, when the technique was applied to the partially dentate patient, or for single teeth. This brought greater challenges because pathological periodontal flora were still present, occlusal loads higher and requirements for good appearance more stringent as implants were placed in the ‘aesthetic zone.’

Bone grafting and bone augmentation techniques were developed to allow implant placement in compromised situations and, latterly, to enhance the final aesthetic result (Figure 9). Many of the bone grafting procedures, developed over 50 years ago as pre-prosthetic surgery to treat edentulous patients by increasing ridge volume or the denture-bearing areas, have been moved directly into the implant world. The same is true of soft tissue grafting from established periodontal practice. Guided tissue regeneration has developed into guided bone regeneration. The concomitant use of allographs, xenografts and synthetic material has reduced morbidity and the need for a donor site for an autograft.

Peri-implantitis was recognized as an entity in 2012 (Figure 10).³¹ Hitherto, this condition had not troubled the early implant dentists who worked only with edentulous patients. The oral flora is different between partially dentate and edentulous patients. However, the change from machined surface implants to those with roughened surfaces to speed up osseo-integration may be just as significant a cause.

So, with careful treatment planning and provision of care, dental implants can be very successful with survival being approximately 95% depending on the criteria used.³² The main risk factors reducing success are:

• Lack of bone for placement;
• Periodontal disease – presence or past history;³³
• Smoking habit.

The placement of implants in young patients is inadvisable until they have completed growth (17 years for girls and 18 years for boys). Long-term outcomes are also unknown: these patients may have another 70–80 years for their implants to survive, while providing good function and appearance. Even if the fixtures survive, we would expect a number of replacements for superstructures and crowns. According to Albrektsson’s criteria for survival applied to machined surface implants, crestal bone loss of 0.2 mm per year, or 1 mm every 5 years would be expected to be normal. If this was a linear rate of bone loss, we could expect all 10-mm implants to have failed in 50 years.

Restore or replace poor prognosis teeth?

Despite the inevitable maintenance and some expected failures, the use of implants has challenged the preservation of periodontally involved teeth,³³ endodontically treated teeth,³⁴ and other broken-down teeth with a reduced prognosis. When planning treatment, a cost–benefit analysis has to be carried out, taking into account both biological and financial costs, with an estimated prognosis for each type of treatment. When a tooth requires endodontic treatment, post retention and a crown, the cost approaches that of an implant. Long-term prognosis may swing the analysis in favour of extraction and implant provision (Figure 11).

This discussion may apply to a single tooth, but also could extend to the whole dentition and assumes that implants have a better survival than teeth whatever their condition. The ‘all-on-four concept’, or ‘teeth in a day’, represents a development of implant techniques. It is of some concern to see multiple extractions of teeth of reasonable prognosis to facilitate this treatment described in the literature and social media (Figure 12). These techniques are often accompanied with severe reduction of the residual alveolus to simplify treatment and enhance aesthetics. Rehabilitation of such patients in the future when failures occur would appear daunting.

The full mouth rehabilitation

Prior to the advent of dental implants, the only way for patients to avoid large partial dentures was with extensive, and often, a full arch conventional bridge or bridges. After consideration of the abutments, occlusion and spans involved, poor prognosis teeth were removed. The quality of the remaining tooth structure, use of post retention, periodontal and endodontal status would all be taken into account. The application of Ante’s law made for safe treatment planning whereby:

‘The pericemental area of the abutment teeth should be equal to or exceed that of the replacement teeth or pontics’.³⁵

If bridges were considered to be too high risk for failure, then a fixed and removable reconstruction was made, often involving precision attachments to enhance denture stability and retention (Figure 13). Precision attachments, once popular, have markedly declined, but many types have found their way into implant dentistry to help retain implant overdentures. The concept of ‘planning for failure’ was a wise one for obvious reasons (Figure 14). Similarly, the treatment of severe generalized tooth wear or a heavily restored dentition was managed in the same way (Figure 15). So, safe practice was to remove poor-prognosis teeth.

‘Experimental gingivitis in man’ by Harold Loe et al in 1965³⁶ was a watershed moment in the management of periodontal disease. The concept of a pathological plaque, or biofilm, causing gingivitis and later, periodontitis, was born. Treatment has followed these lines ever since, and is usually effective for most compliant patients unless they fall into the most severe form of disease or ‘downhill’ group.³⁷ Until this point, the management of traumatic occlusion with occlusal adjustment was thought to be just as important an aetiological factor.

In the 1990s, the periodontal or cross arch bridge was described by Nyman et al in a series of papers.³⁸ These full-arch reconstructions were considered for patients who had resolved periodontal disease, but had lost poor-prognosis teeth in the process. Many of these bridges were built on a reduced number of abutment teeth, and certainly did not conform to Ante’s law. Careful provision of the bridges, and management of the occlusion with ongoing periodontal maintenance care was essential for success. Survival of these bridges was comparable to bridges of much smaller spans (Figure 16).

With good maintenance care for this type of work, the survival would be in the order of 10–20 years. However, even the best of work could end with spectacular failure. Such failures could occur in a short period of time if the standard of care was poor, or the patient failed to clean it. Remedial treatment would often involve large partial dentures, or even a dental clearance and complete dentures (Figure 17).

When the new technologies of resin-bonded bridges and dental implants became available, the need for conventional bridges reduced. Major tooth preparation was avoided for resin-bonded bridges (Figure 18), and avoided completely if dental implants were used (Figure 19). This should have improved the survival of teeth and reduced maintenance care for patients. This is difficult to prove. Resin-bonded bridges have not had universal acceptance by dentists in the UK, and in the USA, they are still viewed by many as temporary restorations only. As mentioned earlier, the availability of dental implants may have led to an increased number of teeth being removed as a clearance, with ‘all-on-four’ implant reconstruction being viewed as preferable. When these reconstructions fail, the only options are to repeat the treatment or revert to complete dentures. Clearly, dentists and dental technicians can ill afford to lose their prosthetic skills.

Changing patient attitudes

The possession of bright white, straight teeth is no longer a desire restricted to the younger generation (Figure 20). Many older or retired patients wish to maintain a similarly good appearance. Those in this age group are also much less likely to accept the loss of teeth and presence of a gap, or use of a denture, when a fixed replacement with a bridge or an implant is possible.

Adult orthodontics, whether with fixed appliances or aligners, is also more common. Often this will be followed by bleaching. This should reduce the need for destructive tooth preparation to achieve the same result by restorative means. When the natural teeth have darkened adjacent to brighter, but otherwise satisfactory crowns or bridges in the older patient, the option of bleaching may be preferable to replacement of the restorations.

Regular attendance to see the dental hygienist is accepted by most adult patients, particularly if they have been treated for primary disease. As the population ages and patients retain more teeth, the need for maintenance care will increase. Root caries, secondary caries and, on occasion, new caries can affect older patients. High-concentration fluoride toothpaste, such as Duraphat 5000ppm (Colgate-Palmolive (UK) Ltd), did not exist 50 years ago, but can contribute to effective preventive care in such patients. Improvements in glass ionomer cements and bonded composite restorations have proved invaluable when treating older patients for caries, but also for cusp fractures (Figure 21). It is difficult to quantify how long these restorations or repairs last. However, many dentists will have been pleased to see how successful they have been in avoiding large replacements or a progression onto crowns.

Are our patients better off?

In simple terms, all our patients want is their teeth, restorations or tooth replacements to work, look like teeth and last. Adult dental health surveys show clearly that patients are keeping more of their teeth for longer.^39,40 It is difficult to make comparisons between current dentistry and that provided 50 years ago. Statistically, failures per year⁴¹ have been substituted for Kaplan–Meier survival analysis using accepted criteria such as that developed by Cvar and Ryge.^9,24,42 Patient satisfaction surveys have broadened to include quality of life assessment. Aesthetic assessment by the operator now includes an assessment of the gingival health and appearance, together with the restoration appearance, with pink and white scores often being combined for an overall assessment.⁴³ Interestingly, it would appear that dentists are more critical of their work than their patients, which would be appropriate and very fortunate for the less gifted in our profession.⁴⁴

Dental implants have been used regularly in the UK for about 35 years, and for longer in Europe and North America. Prospective research covering all aspects of care is abundant, with some studies extending over 20 or more years. The success rate was high at the outset and improvements minimal over subsequent years. Success criteria have been difficult to standardize, but early studies would commonly show 90% success in the maxilla and 95% success in the mandible over many years.^44,46 It would be difficult to improve upon this. More recent studies may be 96% over 5–10 years.⁴⁷ This has been mirrored by other treatments, such as endodontics, when high success rates were possible in the 1980s,⁴⁸ with small extra improvements today.⁴⁹ However, endodontists will not be giving up their rotary instruments and NiTi files followed by thermoplastic gutta percha for hand instruments and laterally condensed gutta percha. It has become much easier to obtain good results. In the implant world, healing time has reduced and single-stage surgery is probably firstline treatment. Immediate placement and loading, flapless surgery and guided surgery are all options to consider. Treatment has been simplified and this should be more manageable for our patients. Much research and technique development has been aimed at improving the final appearance of dental implant restorations. The implant adage: ‘Tissue is the issue but bone sets the tone’ remains true, so socket preservation, immediate implant placement and hard and soft tissue grafting continue to be developed. When so many different techniques exist, it should be clear that there is no technique superior to the others. Such procedures remain technique-sensitive and require training and practice for clinicians to become proficient with them.

So, has undergraduate and postgraduate training improved in restorative dentistry with these advances over the past 50 years? The General Dental Council is charged with maintaining standards. As all dental schools remain open, we must assume that these have been maintained. The curriculums are busy, but the amount of operative or restorative work carried out before qualification has reduced over the past 50 years. In some schools, finding enough suitable cases for endodontics or crowns, for example, has proved difficult. Fluoridation has been particularly effective in some parts of the country.

Older dentists will remember the need to meet requirements for plastic restorations, endodontics and crowns, for example, before being able to sit final exams. A competency approach to assessment may be flawed for a variety of reasons. There is no substitute for experience, and many newly qualified dentists or specialists do not feel confident about working on their own. It may be a number of years before confidence is found and dentists work out what works for them.

For the majority of dentists, their clinical work may not be peer reviewed again until they retire, or they become involved in a medico-legal case. Practical courses on phantom heads, or postgraduate courses where patients are treated, allow for peer review. While daunting at first, the benefits of this learning experience is never lost. However, there are not enough of these courses for dentists to attend and they are also expensive with a course fee of around £30K per year for a masters programme. While attending, there is also the added sacrifice of loss of earnings from the regular job. Postgraduate courses that are purely didactic or online will improve knowledge, but not enhance clinical skills. On a practical note, it would appear that to obtain good implant survival or success rates, it may be necessary to place in excess of 50 implants.^50,51 This does not necessarily mean they are in the right place, but that they have integrated!

Dentists would be wise to carefully choose the postgraduate courses they attend so that they can improve their treatment planning and clinical skills.⁵² Fifty years ago, continuous professional development (CPD) was limited to an NHS section 63 course, or a local BDA meeting. A few dentists may have undertaken a 1-year masters course. Today, many courses exist, covering all aspects of dentistry. The GDC has looked to ensure some quality assurance of these courses.

Entry to the specialist lists started in 1998. Specialist membership examinations to gain entry to these lists used to involve a practical component. However, patients today should still be confident in their specialist’s diagnostic and treatment planning skills, but will have to hope that the clinical skills are present because they have not been assessed. Reputation is difficult to define, but many dentists in general or specialist fields gain this from their colleagues or their patients. It may still be the best way for a patient to find the right dentist for the job.

The funding for undergraduate and postgraduate training has changed over the past 50 years. Students used to run up an overdraft with the bank over their 4–5 years of training, usually the result of socializing or taking holidays that the student grant would not cover. This was easily cleared in NHS practice after a year or two. In 1998, tuition fees and student loans were introduced and very rapidly young dentists had acquired a large debt of £50–60K, which would need servicing. Postgraduate study added considerably to this debt, with perhaps £35K for each year of subsequent study. This requires a lot of hard work to clear the debt. Many will cope with this and hope that a work/life balance can be achieved in time.⁵³ Some unscrupulous dentists may look at patient mouths and look to reduce their debts with some unnecessary dentistry. It is easy to see why courses on practice management, advertising and finance remain popular. Equally popular is the need to demonstrate on social media the dentist’s ability to provide veneers, crowns and implants. Some of this work is beautiful and justified. But much of it is not, and we may be reverting to the destructive dentistry of yesteryear (Figure 22). Some patients may request a ‘Smile makeover’, but modern techniques may achieve this ethically and sensibly without the accompanying damage.

It is easier today for dentists to provide high-quality dentistry than it was 50 years ago. The world is a different place, with different demands from our patients. The specialties of conservative dentistry and prosthetic dentistry have disappeared, and have been replaced by prosthodontics. While not recognized specialties, many dentists view themselves as cosmetic or aesthetic dentists, or implantologists. Who knows what we will call ourselves 50 years from now.

Now is an exciting time for dentists to be entering the profession. Technology will continue to advance and how we provide dentistry will continue to improve (Figure 23). Let’s hope that we can remain caring of our patients and maintain our professional status in the process.