Further reading
3.5.4 Secondary or recurrent caries 2
dontists who have used it for years to separate teeth before placing bands around them. A small round elastic is forced between the contact points using a special pair of applicating forceps (Figure 3.14a). After a few days the teeth are separated (Figure 3.14b). The dentist can now feel, very gently, with a probe to detect whether a cavity is present. Alternatively, a little elastomer impression material can be injected between the teeth(Figure 3.14c). After a few minutes the set material can be removed with a probe and the impression examined to see whether there is a cavity (Figure 3.14d).
Clinical-visual examination
A particular problem, with amalgam restorations is marginal breakdown or fracture, often called ditching(Figure 3.15). This has long been regarded with suspicion by clinicians, and restorations replaced as a preventive meas- ure to avoid plaque stagnation in this area. There are a number of reasons why this approach is incorrect:
• Ditching occurs occlusally in an area that is easy to clean. Recurrent caries usually occurs approximally and cervically in areas of plaque stagnation.
• Clinical study has shown ditching does not reliably predict infected dentine beneath the ditched area unless the ditch is an obvious cavity that would admit the tip of a periodontal probe (over 0.4 mm).
• When dentists remove ditched fillings, they overcut cavities by as much as 0.6 mm. The dentist may also perpetuate the error of cavity preparation and restoration which caused the ditching problem. This is often too sharp an amalgam–margin angle, which makes the edge of the filling prone to fracture. The tooth is thus in danger of entering a repetitive restorative cycle until the dentist literally runs out of tooth tissue.
Discoloration around restorations with clinically intact margins also does not reliably predict new caries beneath the restoration (Figure 3.16).
Sometimes discoloration around an amalgam can be caused by corrosion products from the amalgam or by light reflecting from the amalgam itself through the relatively translucent enamel. Discoloration around amalgam may also indicate demineralized, stained dentine, but this is residual caries left by the dentist who placed the filling. If these restorations are removed, the dentine is discoloured but either hard or crumbly and dry and not heavily infected. This does not indicate new disease. Staining around an amalgam restoration should not trigger its replacement unless a carious cavity, or a very wide ditch that traps plaque, is also present (Figure 3.17).
Colour changes around tooth-coloured filling materials may come in a number of forms. An active white spot lesion may be present and preventive treatment is indicated. A line of stain at the junction of the filling and the
E S S E N T I A L S O F D E N TA L C A R I E S 5 6
Figure 3.15. Ditched amalgam restorations.
tooth may indicate leakage around the filling, but unless the patient requests its replacement because of poor appearance, operative treatment is not required (Figure 3.18).
Stain around a tooth-coloured filling can also present as grey or brown dis- coloured dentine shining up through intact enamel (Figure 3.19). This appear- ance probably represents residual caries left when the cavity was originally repaired. Clinical study indicates that this appearance does not reliably indicate
C A R I E S D I A G N O S I S 5 7
Figure 3.16. The enamel around the amalgam restorations on the palatal aspect of the upper lateral incisors is discoloured. Is this discoloration due to caries or corrosion of the amalgam? A decision was made to replace these restorations and removal of the amalgam revealed discoloured, hard, dentine. The replacement was unnecessary.
Figure 3.17. A cavitated carious lesion, full of plaque, is present at the cervical margin of the restoration in this molar.
E S S E N T I A L S O F D E N TA L C A R I E S 5 8
b
Figure 3.19. (a) Stained dentine around a tooth-coloured restoration.
(b) The appearance of the cavity once the restoration has been removed. Stained and demineralized dentine can be seen. If this is either hard, or soft, dry, and crumbly it is likely to be residual demineralization left when the restoration was originally placed.
Figure 3.18. A line of stain at the junction of a tooth-coloured filling and the tooth.
a
infected dentine (and presumably active demineralization) beneath the filling. If the margin of the filling is clinically intact it is unlikely that active caries is present beneath and the filling does not need to be replaced.
Bitewing radiographs
Bitewing radiographs are important in the diagnosis of recurrent caries because this usually occurs cervically in the area of plaque stagnation (Figure 3.20). It follows, therefore, that restorative materials should be radio-opaque.
Sometimes a radiolucency on radiograph indicates residual caries left when the restoration was placed. Figure 3.21 shows a bitewing radiograph of an amalgam restoration in a lower first molar with areas of radiodense dentine beneath the restoration. This appearance represents residual demineralized dentine left when the filling was originally placed. Tin and zinc ions from the amalgam have passed into the demineralized area to give the radiodense appearance. This restoration does not need to be replaced.
C A R I E S D I A G N O S I S 5 9
Figure 3.20. A bitewing radiograph showing root caries cervical to amalgam
restorations. New restorations are indicated but preventive treatment is also very important.
Figure 3.21. A large amalgam restoration is present in the lower first molar and areas of radiodense dentine are present beneath the approximal aspects of the filling. These areas probably represent residual demineralized dentine left when the cavity was originally prepared. Tin and zinc ions from the amalgam have passed into these areas to give the radiodense appearance.
3 . 6 D I A G N O S I S O F C A R I E S R I S K5
The distribution of caries is highly uneven among contemporary popu- lations. How convenient it would be if those at risk of developing carious lesions could be identified, both at the level of the individual in the surgery and the population. The dentist could then target expensive non-operative treatments appropriately and at a community level preventive efforts could also be targeted. This is called a ‘high risk strategy’.
Although this concept seems both logical and laudable, it does not actu- ally work. At the individual patient level, the best predictor of caries risk is current caries experience. Thus, the patient presenting with lesions is at risk of caries progression and developing new lesions.5 This is obvious, but slightly frustrating because there is an element of ‘shutting the stable door after the horse has bolted’!
To assess caries activity in an individual patient, note how many lesions are present (both cavitated and non-cavitated) and where they are located.6 If a history of recent caries activity is available (number of lesions and fillings over the last 2–3 years) this is also valuable. A yearly increment of two or more lesions, detected clinically and/or radiographically, would indicate a high rate of lesion progression. The formation of lesions in areas such as lower incisors and buccal surfaces of molars, where salivary flow is relatively rapid, also indicates a high risk of caries progression.
3 . 7 E X P L A I N I N G A N I N D I V I D U A L’ S C A R I E S E X P E R I E N C E6
Once a dentist has assessed a patient’s caries activity status as high, an attempt should be made to identify the relevant risk factors because it may be possible to modify these and thus slow down disease progression. Some of these risk factors are listed in the box opposite.