A sizeable proportion of the dento-legal problems in restorative dentistry and prosthodontics arise in connection with the restoration of compromised teeth.
When discussing teeth, the word compromise refers to any reduction in the functional life of the tooth without it requiring any additional intervention.
The loss of significant quantities of natural tooth tissue can precipitate a compromised state if the structure of the tooth is altered, such that its resistance to fracture is reduced or the death of the pulp is precipitated.
The loss of natural tooth tissue can arise gradually (e.g. from disease processes) or suddenly (e.g. as a result of trauma).
It can occur for physical reasons as in the fracture of a previously weakened tooth, or electively (e.g. preparing a tooth to receive a fixed restoration, or cutting an access cavity for endodontic treatment).
Whatever the cause and timing of the tooth tissue loss, however, there is no doubt that each event or intervention in the life of a tooth, impacts upon the future prognosis. Assessing and communicating that prognosis to the patient before embarking on a new course of treatment can prevent future accusations that the latest treatment was in some way to blame for causing the condition of the tooth in question.
Investigations
For this reason it is important to identify any teeth that are compromised in one way or another at the very outset, during the diagnosis and treatment planning process - for example:
- Loss of periodontal support
- Endodontic/ periapical status
- Loss of natural tooth tissue
- Structural weakness (hairline cracks or suspected cusp fractures, posts etc)
- Excessive occlusal forces.
This assessment should be made in the light of the history, symptoms and signs, and any relevant investigations and special tests, each of which needs to be recorded in the clinical notes, in terms of:
(a) The investigation carried out
(b) The result.
(c) The conclusions drawn.
Endodontics
Sometimes conclusions are drawn from a variety of different sources, some of which are more helpful than others. An example of this is the combination of reported symptoms, clinical examination, radiographs, and percussion and vitality tests, that together lead to a diagnosis that a tooth requires endodontic treatment.
Decisions of this nature are not always straightforward - but they become all the more important when consideration is being given to the suitability of the tooth in question to support a crown or bridge. When assessing the tooth prior to any such restoration, therefore, it is important to record every piece of evidence that led to that decision.
It is not uncommon to find investigations yielding inconclusive results (or negative results) are not recorded in detail, or at all. In fact, it is just as important to record negative findings are as it is to report positive findings.
Clinical judgement and 'gut' feeling based upon previous experience may not sit at the top end of any hierarchy of evidence, but they should certainly not be discounted entirely.
Periodontal assessment
Assessing the quality of the periodontal support of a tooth is a balance between direct observation (e.g. of inflammatory changes), objective tests such as probing depth measurements, and other tests which rely to some extent upon subjective interpretation of objective facts (e.g. mobility, radiographs).
The clinical records should contain all of these elements, especially when the quality of a tooth's periodontal support is likely to have a long-term impact upon the prognosis of various treatment planning options that are under consideration.
Follow-up
The assumption that a compromised tooth ceases to be of concern, as soon as it has been restored, is an easy trap to fall into. Nothing could be further from the truth, and indeed, it is necessary to monitor the health of any such 'high risk' tooth on a regular basis, these reviews being chronicled in the clinical records.
Teeth that are restored following trauma are perhaps the commonest example of this, and if the gradual loss of vitality, perhaps accompanied by the development of an apical cyst or other pathological change, results in an acute problem for the patient some years later, a dentist could be vulnerable if the clinical records reveal no evidence of any monitoring of a tooth which was at a higher risk of such a complication.
Posts
Opinions have fluctuated over the years as to the status of the rootretained post within the armamentarium of restorative dentistry and prosthodontics. The fact that post crowns feature highly in failed crown and bridge work, has been well documented in the scientific literature.
From a dento-legal perspective, however, it is more valuable to look in more detail at what goes wrong, and at what can be done to minimise the potential problems.
Four main areas of risk
- Angulation (leading to perforation)
- Length (leading to loss of retention, or decementation and subsequent caries, or - if too long - interference with the apical seal)
- Strength (often related to length, width, and design as well as to the material used for its construction)
- Design (Parallel or tapering? Threaded or smooth? Cast or preformed?)
Angulation
One of the problems of providing post restorations is that the coronal tooth tissue is often reduced or missing altogether, which deprives the clinician of valuable anatomical guidance. A good preoperative x-ray is a useful starting point to minimise the chance of mesial or distal perforation, by enabling the clinician to identify the angulation and anatomy of the root which lies beneath the gingival level. Following the course of a pre-existing root canal treatment (RCT) is another time-honoured precaution (although this presumes that the RCT itself is in the correct place!).
Study models or clinical photographs of the original tooth, if available, can sometimes provide helpful clues as to the angulation of the tooth in a buccal -lingual plane, as can knowledge of skeletal and dentofacial characteristics.
The retroclined upper central incisors and proclined upper lateral incisors of the classic class II div(ii) malocclusion, with associated skeletal/ facial characteristics, is a good example. Taking due note of the anatomy of the supporting bone overlying a root is a simple further precaution to minimise the risk of perforation. In each case, the prudent clinician will pool information from all the above sources when planning the angulation of any post hole.
Length
Without doubt, one of the most common problems seen in post crown failures is that of insufficient post length. Some clinicians prefer to err on the side of caution, perhaps reflecting their fear of possible perforation, but this often proves to be a short-sighted strategy. The leverage and lateral pressures that a mobile short post creates, can easily lead to a root fracture, which may have the same terminal consequences for the tooth in question as any perforation might have done.
The break down in cementation of a post crown under a bridge that is held firmly in place by castings attached to other abutments, can lead to massive root caries and a major restorative problem unless it is identified and dealt with at an early stage. Bridges which rely on one or more posts, especially when these form the last abutments at one end or the other of a bridge, are a particular risk.
Due account needs to be taken of root morphology; fine, tapering roots are easily fractured by long posts which leave insufficient enclosing root structure and strength to survive on a long-term basis.
In shorter roots, the lack of tissue for the preparation of an adequate post length can lead the clinician to consider options such as increasing the post width, or creating an eccentric post shape to maximise retention. Either of these options can precipitate an early root fracture.
Strength
A range of new materials has been described in the literature, from carbon fibre and composite resin to ceramic and other materials. The traditional cast metal post and core is still in widespread use, but when these posts are too thin there is the ever-present risk that they will fracture off in situ, which will then create a particularly difficult restorative challenge.
Design
This is an area which continues to create much controversy. Parallel and tapering posts each have their advocates, as do cast and preformed post techniques. Each technique has wellrecognised advantages and disadvantages and will lend itself to some clinical situations, but not to others. Some believe that threaded posts are the answer, while others believe that their use is the most reliable method of splitting roots yet devised.
The key is to keep abreast of the literature and the evidence base, to take advantage of new techniques and materials, and also to learn from your own successes and failures. Certainly, there have been many failures associated with virtually every post technique, and there seems to be no magic formula which will avoid all of the potential problems, all of the time.
However, it is helpful to bear in mind that almost by definition, posts are placed in teeth which have already reached, or are fast approaching, 'last chance saloon'.
It is probably well worth reminding ourselves that a post is not a restoration in itself - its purpose is to support another restoration in some way, while preserving and protecting the residual root structure. Posts fail when they no longer satisfy either (or both) of these objectives. It is important that the patient is made aware of the limitations of the restoration.
The cracked tooth
It is a sign of the times, perhaps, that patients assume and expect that healthcare professionals will be able to make unfailingly accurate diagnoses, and to provide 'instant' remedies for any symptoms they might present with. The 'cracked cusp' or 'cracked tooth' is notoriously difficult to diagnose and treat with certainty, and it is starting to feature heavily in dentolegal cases. This is likely to be a growing problem as patients retain more of their teeth into later life.
When treating this clinical problem, these are two separate aspects that must be addressed with equal care and circumspection. One consideration is the tooth itself, where the symptoms can be thoroughly frustrating and misleading when trying to reach the 'cracked cusp' diagnosis, while excluding the many other possible alternative explanations for the symptoms. On the other hand there is the patient, who needs to be kept closely informed and presented with their treatment options at each step along the way, together with a realistic explanation of the prognosis.
Perched at the end of this clinical dilemma, in many cases, is an angry patient faced with the prospect of losing the tooth in question, or the cost of having endodontic treatment and a crown, and invariably the patient's dissatisfaction includes allegations that they have 'paid all that money for nothing' or that they 'would not have needed all this treatment if you had done your job properly in the first place'.
History and investigations
As always, the patient's clinical records should be sufficiently comprehensive to come to the practitioner's rescue if such allegations are made. Sadly, all too often, the lack of such records makes any defence of the allegations unnecessarily difficult. The first step is to record carefully the history of the symptoms as reported by the patient, remembering that negative findings can be as important to record as positive findings.
The key is to be able to demonstrate that skill, care and a logical approach is brought to bear upon the investigation process, using the full range of alternative 'tools' available.
While measurements and recordings of mobility and vitality are usually an important part of the total information to be gathered in these situations, percussion testing is perhaps the most important. A dull percussion sound can be diagnostic but here again a normal response to this test is an equally important finding which should be recorded. The presence or absence of tenderness to percussion when the cusp is struck in various directions is an essential test and needs to be recorded carefully. Further aids such as the 'Tooth sleuth' have been commercially developed to assist in the diagnostic process.
Radiographs
Radiographs are not always very helpful in the diagnosis of a cracked cusp, but they are often a necessary part of excluding other possible explanations of the patientâ€symptoms.
On the other hand, transillumination can be of particular value, and can readily detect hairline fractures and cracks that are often invisible to the naked eye.
Communication
Clinicians will be aware of the various treatment approaches to this problem, ranging from the more conservative etch-retained composite restoration to stabilise the cusp(s), to the more extensive cast restoration. Occasionally, of course, the nature and extent of a crack makes it impossible to save the tooth, and sometimes the presence of the crack of fracture is self-evident and the treatment of choice is clearly apparent from the outset.
Whether one adopts a cautious, or more radical approach, the patient must be given sufficient information in order to be able to understand what treatment is being recommended and why, and to appreciate the range of available alternatives. These discussions need to be carefully recorded in the patient's notes.. This clinical situation is highly vulnerable to the patient claiming, after the event, that they would have elected for a different treatment approach had they been made aware of its availability.
Occasionally, the need to refer the patient for a second (perhaps specialist), opinion arises, and as always this should be offered where appropriate, the fact being duly recorded in the patient's notes.
Summary
Compromised teeth are slowly becoming an everincreasing dento-legal threat as clinicians try to save teeth in a wider range of difficult clinical situations. The key to their successful management lies as much in effective communication with the patient, as it does in finding new technical solutions to longstanding clinical dilemmas.
Tempting as it may be, to seek to reassure the patient by playing down the problem (or potential problem), and conveying a confident 'we have the technology' approach, the extensively restored or otherwise compromised tooth, or the cracked tooth/cracked cusp are clinical booby-traps that can deceive and embarrass the most capable of clinicians. A cautious and careful approach, meticulously recorded in the notes, will minimise the many dento-legal risks associated with these clinical situations which are growing in frequency.