The stone models, provided by the dental technician at this stage, are more accurate than those cast from the primary impressions, they are also far more hard-wearing than the initial (plaster) models, and give the dentist a clearer indication of the patient’s mouth.
Occlusal wax rims are arch-shaped blocks of wax which are positioned where the false teeth will eventually be on the final denture. These occlusal rims are made to what is predicted to be the correct height of the teeth, if accurate they should feel reasonably comfortable to the patient when in situ in the mouth and the patient is at rest, i.e. the patient shouldn’t feel as if they are over closed or propped wide open. The occlusal rims sit on a baseplate, which is often also made of wax. The base plate is moulded into shape on the model to represent the overall shape of the final denture.
Once the patient is in the dental chair the wax blocks (both upper and lower) are fitted in their mouth. The dentist ensures that the height and position of the occlusal rims is correct and makes any adjustments if necessary. The dentist also measures the patient’s facial height when the patient is at rest, this is done using a ‘Willis Bite Gauge’, which fits underneath the patient’s nose at one end and fits underneath the patients chin at the other end, there is a measurement guide within the bite gauge which allows the dentist to get an accurate reading in millimetres. Some dentists will also mark the wax where they believe the midline is where the canine teeth should be positioned and some will mark the wax to indicate where the patients lip line is- providing as much information as possible for the dental technician.
When the necessary measurements have been taken and the dentist is happy with the result the wax blocks will be secured together by softening the wax on the biting surfaces, fitting them in the patient’s mouth and asking the patient to bite together, allowing the separate blocks of wax to mould together, resulting in one wax block instead of two.
The dentist then discusses with the patient the shape and shade of teeth to be placed on the denture, as well as discussing any other relevant factors concerned with the teeth or denture e.g. whether or not the patient would like a diastima between upper central incisors or whether any clasps are to be placed.
The next prescription is written by the dentist and the bite blocks are cleaned (in cold water) and disinfected and fitted back onto the patient models. The models and bite blocks are wrapped in a protective covering e.g. bubble wrap, and are placed back into a bag, ready to be sent back to the dental technician with an updated laboratory slip – which prescribes the next stage of the denture making process – the try-in.