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References

: FGDP; 2018
Mallya M, Lam E., 8th edn. Missouri: Elsevier Inc; 2019
Kidd E, Fejerskov O, Nyvad B. Infected dentine revisited. Dent Update. 2015; 42:802-809
Rout J, Brown SC. Ionizing radiation regulations and the dental practitioner: regulations for the use of X-rays in dentistry. Dent Update. 2012; 39:248-253

Technique Tips: The Post-operative Bitewing − a Solution to an Ambiguous Bitewing Radiographic Finding: is it Recurrent Caries or Partial Caries Removal?

From Volume 47, Issue 3, March 2020 | Pages 275-277

Authors

Richard Lilleker

BDS

Gwynne Dental, 41 Cliddesden Road, Basingstoke RG21 3EP, UK (richard@gwynnedental.co.uk)

Articles by Richard Lilleker

Article

Bitewing radiographs are commonly carried out for several reasons,1 one of which is to detect recurrent caries underneath restorations, typically in proximal regions. Examples are given in Figures 1−4. Caries has the appearance of a radiolucency, which can be mimicked by several artefacts such as burnout or optical illusion.2 The recent paradigm shift towards partial caries removal may add an additional phenomenon to be considered, namely deliberate retention of caries.

Figure 1. (a) Restorations are required in UR54 and LR5. This is a young individual with a high caries rate. (b) Post-operative bitewing taken following restorations in which partial caries removal was carried out. The post-operative radiograph was justified as the caries in the UR5 was extensive and, in order to avoid a pulpal exposure, soft caries was left in situ. Due to the high caries rate, it was felt likely that recurrent caries would have a high index of suspicion, and therefore it would be prudent to allow accurate monitoring.
Figure 2. (a) LR567 all have interproximal distal root caries. The lesions have worsened in spite of intensive fluoride and IP cleaning. Restorations are required. (b) Post-operative bitewing shows that the LR7 restoration has an imperfect margin, and the LR5 a marginal radiolucency, giving in the future what would be an ambiguous appearance.
Figure 3. (a) Initial bitewing. Diagnosis is failed carious restoration of the LR7, not distal cervical caries due to the LR8, thus removal of the LR8 was not justified. (b) Prepared cavity in LR7. Note the impacted third molar is unerupted and matrix placement will be challenging. (c) Post-op bitewing radiograph. The radiograph was justified as there is a high risk of recurrent caries or caries due to the position of the LR8, or just ambiguous burnout. As it happens, the radiograph shows a reasonably clear restoration margin.
Figure 4. (a, b) Clinically, an obvious unrestored occlusal cavity, but with a strange appearance on the initial bitewing radiograph. (c) Occlusal cavity prepared for restoration and green arrows mark the well hidden buccal pit restoration, which appears superimposed upon the occlusal caries of the bitewing. (d, e) Finished restoration. What is the justification for the post-op bitewing? The superimposition may make monitoring of both restorations harder, and the initial radiolucency may have been from either or both cavities. The post-op bitewing clearly shows no significant remaining caries eliminating any future ambiguity.

Partial caries removal

Many recent developments in cariology challenge the traditional view that all caries must be removed from a lesion.3 The current thinking is that, as long as a restoration's margins are sealed against bacterial and nutrient infiltration, the caries can be left in place, reducing the insult to the pulp and maintaining structural integrity. In an ideal world, the radiographic appearance of such a restoration would be fairly obvious, namely a clear caries-free margin. But detecting a large radiolucent area under an existing restoration may make us fear for the health of the pulp and lead us to assume recurrent caries and intervene. What if simply it was originally a deep lesion and a large amount of demineralized dentine was sealed under the restoration?

There are many clinical situations where a clear margin cannot be created. For example, deep interproximal root caries can be on the limit of matrix placement and therefore the clinician tends to be reluctant to remove any remotely sound dentine.

Upon reviewing such a restoration on a later routine bitewing radiograph, a clinician can be struck by a dilemma: is this radiolucency recurrent caries under the new yet failing restoration? Or is it a successful sound restoration with retained demineralized dentine or arrested caries? One diagnosis leads to operative intervention, one does not. Which is correct?

Traditional solutions

Once in this dilemma a clinician has a few options. Direct tactile investigation of the root surface can be attempted, ideally with a contra-angle probe. This will detect a gross cavity but is unlikely to confirm a deep or early lesion.

Further radiographic monitoring can be done to detect lesion progression. Whilst effective an obvious drawback is that the active carious lesion will, by definition, become even bigger.

A clinician may decide to intervene and replace the restoration, but if it turns out that the original restoration was intact then it may lead to professional embarrassment as well as likely further loss of tooth structure and pulpal sequela.

The post-operative bitewing

Avoidance of the dilemma altogether is surely the ideal; and a solution is the post-operative bitewing.

Firstly, a suitable candidate needs to be identified. The author is not suggesting that every restoration should be radiographed after placement. This technique should be reserved for situations where a future ambiguous bitewing result can be predicted. Particular examples could be:

  • Deep root caries or tipped teeth with a high risk of an indistinct margin and burnout;
  • Situations where a correct diagnosis of recurrent caries is of increased importance, eg presence of an impacted third molar, a lesion on the limit of restorability or a lesion close to the pulp; intervention leading to invasive treatment or an extraction;
  • Restorations placed in sub-optimal conditions which are more likely to fail − this might include difficult moisture control or limited lesion access such as a tunnel preparation;
  • Restorations placed which incorporate a liner or base material which is radiolucent;
  • Situations where radiographic monitoring may be compromised, such as adjacent to another restoration (buccal, palatal or cervical) or obscured by a crown.

    • Immediately following the placement of a suitable restoration a standard bitewing radiograph is taken. This gives a benchmark for the appearance of the restoration, in the knowledge that, having just been placed, the restoration is sound. Future routine bitewings can then be judged against this comparison image, reducing the risk of an incorrect diagnosis.

    If multiple restorations are being carried out in one time period, then it would be logical to wait until all are completed.

    All radiographs are subject to governance, such that they must be justifiable, and as low a dose as practical.4 It is to be stressed that careful case selection must be carried out to identify those that are the most likely to present a dilemma when regular bitewings are next carried out. ‘Routine’ use of this technique – ie following a standard restoration – is not justifiable. It must only be used in exceptional circumstances.

    The use of radiographs outwith the FGDP guidelines requires discussion. The author suggests that the proposed concept has a precedent; that is, a similar concept is the post-op radiograph for endodontics1 and implant placement.1 These post-op radiographs are primarily taken for the purpose of a baseline for future review, which is parallel to the post-op bitewing radiograph within restorative dentistry.

    Both endodontic and implant post-op radiographs have a lack of evidence base. They are classed as ‘C’ in the FGDP document. Obviously, the value of these radiographs cannot be demonstrated by evidence per se; they are valued for their clinical purpose. Similarly, the value of the post-op bitewing can only be tested by clinical logic and experience. It is unlikely that the concept could ever be proved or disproved with a study or statistical analysis.