As dentists we are often needing to acquire a physical copy of the dentition and surrounding soft tissues, and currently the quickest and easiest way to do this is by taking an impression.
Whilst this may not be our most favourite pastime, it is usually something the patient struggles with more than we do. Our patients’ protective gag reflex immediately fires into action, having potential to disclose their dietary secrets.
A good impression is essential if we are to have any chance of our technicians fabricating prosthetics of any use. It is still the case that the GDC’s largest area for complaints is provision of dentures, starting with a good impression would be advantageous in more ways than one.
Where to start with some advice? It has to be materials, ideally instantly setting, smelling of a summer meadow, tasting of paradise and with controllable flow to prevent the stuff squirting unchecked down the oro-pharynx, thereby initiating the inevitable.
Bad news, this stuff does not exist. Next best option, control what we can. Whilst the nurses I work with have eventually got used to me (it’s taken a while) we have some strategies in place for the most predictable technique.
Primary impressions, alginate, of course. I say of course, but only recently I was being harangued by a post graduate student on the implant course, to consider the ‘benefits’ of compound, aka compo.
So, we accept our irreversible hydrocolloid as the best of the currently available options, choose our properties to suit, at one80dental we have 5 different alginates (just for me, I think the orthodontist uses another one) and get mixing.
Wait, don’t forget I’m a total control freak, just ask my long suffering nurses. Alginates are mixed with water, so to maintain control keep a steady eye on the powder:water ratio, and a thermometer in your water, after all you want to get the best impression in just one go, don’t you?
Did I forget to mention the tray? A good fit essential, bit of extra space a bonus, you don’t want the material to be too thin, equally the patient can’t accommodate an excessively oversized tray.
Adhesive, a must. We all know that the patient will be trying their best to ruin your attempts at getting a good impression, coughing, spluttering, heaving and salivating are just some of techniques they will be using.
We have to counter their attempts, and adhesive on the tray will help the material to remain in the tray rather than in their mouth, more importantly reduce the chance of the muscle tension pulling the material off the tray, even only a small amount.
Your nurse will deliver to you a smooth mix of your preferred alginate without air bubbles of course, just before it is loaded into the tray, take a small amount of material and with a finger wipe the material into the occlusal surface of any teeth, thus minimising air blows.
An extension of this technique is to load material into a syringe and express this into the sulcus, and over occlusal surfaces. Seat the tray firmly, but without force. The material needs to be fluid at this stage, without resistance. A common problem is seating a material that is effectively already set, which creates significant distortion.
So a decisive and speedy approach is required. Keep light finger pressure on the tray and have the patient half close their mouth. When removing the tray encourage the patient to keep mouth half closed, as by opening wide they will increase the chance of muscle tension pulling the material off the tray.
What about the major gaggers? Distraction technique is useful. Wiggle their toes (ask them to do it!), raise their feet, massage their chin, sit them up, talk, joke anything to keep their mind off their planned disruption.
Inspect your impression, it should be a good 9 out if 10, accurate without airblows and encompassing all the information you need. Disinfect and send to lab.