The minimal intervention dentistry approach
It is now acceptable practice to only remove “softened” carious dentine using hand excavators, initially adjacent to the enamel-dentine junction, keeping away from the deeper caries and this will lessen the likelihood of a pulp exposure.2
However, it is important to understand that it is not necessary for the cavity to be completely caries-free as this will result in sound dentine being present on the cavity floor, which will lead to the exposure of dentinal tubules that will cause pain for the patient.
Important research was undertaken by Fusayama in the late 1970s and his group classified carious dentine into two zones; “caries-infected” dentine and “caries-affected” dentine.3 This provides guidance on how the histology of the dentine carious lesion can be related to the clinical situation.3 Fusayama advocated removing caries-infected dentine, which is substantially demineralised, consists of irreversibly denatured collagen fibrils and is physiologically un-remineralisable.3 Caries-affected dentine is left behind because it is minimally infected with bacteria, partially demineralised and physiologically remineralisable.3
There is no solid evidence that it is actually necessary to remove all the caries-infected dentine. If there is enamel present at the cavity margins, then the deeper caries can be “sealed” after removal of only superficial soft caries if an adhesive restorative material is used.4
Fusayama also introduced the concept of “painless dentistry”.5 His rationale for leaving the cavity floor consisting of caries-affected dentine is that the tubules are filled with whitlockite crystals formed by reprecipitation of calcium and phosphate ions lost during the carious process and forms a so-called “barrier” to the underlying pulp.5 He wrote in 1991:
“Although dentists have heretofore believed that dental caries treatment must surely be accompanied by pain, our new concept of dental caries pathology reveals that the pain is caused by removing tissue that should not be removed”
Minimizing patients’ pain
Fusayama thereby introduced the concept of “painless” dentistry.5 If only the “soft” caries is carefully removed with an excavator then this will not cause pain to the patient and this is all the operative intervention that is required on the carious dentine. This will also minimise the risk of post-operative sensitivity because open dentine tubules present in sound dentine will not be exposed as mentioned earlier.
We should therefore consider adopting a biological approach to managing caries and cavity restoration and aim to preserve pulp vitality at all costs.
Limiting aerosol generation
An additional risk nowadays is undertaking aerosol generating procedures on patients who may have been infected with Covid-19.6 It would make sense therefore, if access cavities for caries are kept as small as possible if an air turbine is used, thus minimising its’ use followed by careful excavation of only superficial, soft, wet, “infected” carious dentine.
Pulp healing with BiodentineTM
If we are thinking biologically when we are managing carious dentine then we should also be thinking what the health of the pulp might be, particularly if the caries is deep. And it could be that if deep caries is present then the pulp could be “stressed” even if it has responded positively to a vitality test. (1982, Abou-Rass).7 If we believe this concept then, when we proceed to restoration of the tooth, efforts should be directed at minimising further stress on the tooth and consideration given to trying to remineralise the carious dentine remaining on the cavity floor prior to placing an adhesive direct restorative material.
The Bio bulk-fill procedure will allow to place Biodentine from the pulp to the top regardless how deep is the cavity. The setting reaction of calcium-silicate materials are unlikely to stress the pulp further and the calcium-silicate cement, in particular Biodentine™ (Septodont, Saint-Maur-des-Fossés, France) may have a therapeutic effect of ‘pulp-healing”.8
When managing teeth with deep caries, it makes sense from a biological point of view to attempt remineralisation and provisionalization with a “bioactive” calcium silicate cement such as Biodentine™ (and my patients will thank me for that) and a subsequent restoration with a restorative material such as direct composite resin. This may allow the odontoblasts to lay down tertiary dentine and potential pulpal healing.
Even if the direct composite resin restoration subsequently fails, the option for a partial coverage restoration may still remain. This may then delay more invasive dental treatment such as endodontics and restoration with a post and core and a full coverage crown, which could ultimately fail and necessitate extraction of the tooth.