Caries detector dye

 I was going to make a post on caries detector dye because I find it to be such a useful aid during restorative procedures. Then I realised I had already made a post about in 2020. See below.

https://dental-tidbits.blogspot.com/2020/09/a-note-on-caries-detector-dye.html

 I pretty much agree with my thoughts on the previous post. At the time in 2020 I was using the dye fairly regularly as they had it at the public clinic I was at. I think my use dropped off as I transitioned to private practice and not every clinic I worked at had access to it. Now if I worked at a clinic without access to caries detector dye it would be something I would be requesting or purchasing myself. 

Not that I need it to practice, no one needs it, but using it regularly will assist in consistency of your restorations. For proper adhesion to tooth structure, you must ensure that you are bonding to sound enamel and dentine. Therefore caries must be removed to an acceptable standard, clean margins are non negotiable. I would always run into arguments in the student clinics where the students were grossly underprepping teeth for the sake of being "conservative". In those circumstances, caries dye helped to visualise the areas where more preparation was required. To me, well sealed margins are a must and everything internal to that carries variation between practitioners. There are many ways that people use to judge where to stop caries excavation, but most are subjective. "Dentine firmness" is one, but how firm do you mean? Firm to a probe?  A sharp or blunt one? Firm to a slow speed round bur? What size? What speed? Colour? But old caries will be different colour to new caries and new caries will often look indistingushable to sound dentine. 

To achieve consistency in caries removal, what we want are objective ways to assess the remaining tooth structure. Multiple ways exist for example using fluoresence to identify carious tooth structure, using hard tissue lasers to selectively ablate caries. Caries detector dye is an easily accessible way to achieve this. It will stain infected dentine which should then be removed with a slow speed bur. I keep applying it untile I have achieved the appearance I want i.e a zone of sound dentine 360 degrees around the margins of the cavity preparation. 

To use, apply the dye with a brush and leave undisturbed for 10 seconds and then wash it away. Be wary of very narrow cavities where the brush struggles to fit in, I have found the surface tension of the dye to sometimes cause it to not flow into the base of the cavity but instead hover at the cavity entrance. For big, wide cavities, this is not a problem. 

The case below demonstrates my use of caries detector dye. I was restoring the 16M and 15D surfaces due to recurrent decay on the 16 and primary caries on the 15D. This was quite a young girl in her early 20s and the multiple carious lesions forming indicated a very high caries risk. She has a significantly large pulp cavity on the 16 and the caries is lying in very close proximity to the mesial pulp horns.

Existing restoration on the 16M aspect and white patch indicating caries on the 15D

On removing the restoration and opening up the cavity on the 15, I could see recurrent caries at the buccal aspect of the 16M. I removed the discoloured enamel and dentine and was left with a clean looking cavity with some of the remaining restorative material still at the pulpal floor of the cavity. However I was confused as the bitewing xray suggested that the caries penetrated completely under the restoration. I applied caries detector dye and the whole cavity lit up pink. I completely removed the restoration, cleared up the caries and reapplied the dye.

Cavity prep of the 16 and 15 showing caries still present at the DEJ of the 16

It is noteworthy that caries dye can only penetrate so deep into the zone of caries. It will indicate the location of the caries but can't tell you how much deeper to prep. I then rely on the tactile feedback of the slow speed bur and run it over the stained areas prioritising the DEJ area. This will dig a trough into the dentine leaving some unsupported enamel around this prepped zone. You should then come back and remove this unsupported enamel. However I like to clear the dentine caries first and then refine the preparation after I am satisfied with the caries excavation.

Cavity preparation of the 16 showing a clean zone of dentine at the DEJ and unsupported enamel at the buccal and cervical aspect.

In hind sight I would want to remove the unsupported enamel on the vertical and buccal aspect and flare the cavity prep out more. I would also probably want to remove more of the carious dentine at the cervical margin to have a thicker zone of clean dentine. I don't have a specific measurement that I follow but it just seems a tad thin to me here. The other glaringly obvious thing is that there is still caries on the occlusal aspect in the distal pit which I will have to go back at a later date and manage. Lots of things we see in hindsight that we can either ignore or learn from.

Nevertheless, this will likely be a successful set of restorations because the caries removal step was well copmleted. I am more confident that I have provided a well bonded, well sealed restoration. The only questionable aspect is the future pulp status on the 16, only time will tell. However I can proceed with confidence that I have given the pulp the best chance to recover.

Over the past couple of years, caries detector dye has become an invaluable part of my practice. I no longer see it as a learning tool for students but as a way to objectively determine the quality of my caries removal and the quality of the substrate for bonding.