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Prosthodontics

Lec. No. 12

Complete Denture Delivery:

First, try the denture inside the patient’s mouth and, after wearing gloves, check with your fingers for any sharp areas or roughness. Adjust any rough areas with acrylic bur, and try it again in the patient’s mouth. Check the tissue area, the polish area, and the flanges again.

If the patient has an old denture, you ask him to remove it for 12-24 hours before the new denture’s try in.

The next step is pressure-indicating paste: you take some of the paste with a brush, and put a thin layer on the fitting surface of the denture. Usually we start with the area that has undercut, the most common area of which is posteriorly near the tuberosity, but some patients have it both anteriorly and posteriorly.

In the clinic, we use Zinc Oxide with Vaseline to make a cream-like consistency, then we apply it with a brush or a spatula on the fitting surface. We always apply it side-by-side because if we apply it bilaterally, the paste will wash out from some of the areas that you apply pressure on, and therefore you might wrongfully think it a pressure area and trim it. So we apply it side-by-side then simply seat the denture inside the patient’s mouth, then we take out so you can see areas that the paste washed out from. This indicates pressure areas.

How do pressure areas form?

- While taking the secondary impression with Zinc Oxide, one might not have properly shaped the green stick, so the improperly shaped areas will become the pressure areas.

How will the pressure areas clinically affect the patient?

- He will show up complaining of ulcers or erythema. This can be treated with straight hand piece with acrylic bur.

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After we finish the fitting surface, we work on the denture borders. Which can be done following the same procedure for the fitting surface, so any washing out of paste indicates overextension.

If the paste washed out from the freni, that’s because it was not properly open.

In the mandible, the most common area for undercut is lingually, in the retromyelohyoid area. But some patients have undercut anteriorly.

During insertion, you don’t need to put PIP everywhere on fitting surface. You only have to put it on undercut area, borders, and areas that you suspect are overextensions.

In postinsertion, you only put PIP in the specific area that the patient complains from.

Now we check support, retention, and stability.

*Support: resistance to movement towards the tissue.

You check it by applying pressure on the denture towards the tissue, the denture shouldn’t sink.

*Stability: resistance to lateral movement.

You check it by applying lateral movement to one side, the denture shouldn’t come out from the other side.

*Retention: divided into anterior and posterior retention.

Anterior retention check it by pulling down the incisors, you should have good resistance.

Posterior retention check it by putting your fingers on the palatal surface of the upper anterior teeth and trying to dislodge the denture outside, it shouldn’t dislodge if there is a proper posterior dam area.

In case the denture has no retention at all upon placement, think about:

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1- Improperly open freni or a clear overextension.2- No posterior dam area. In this case you have to make reline for the

denture.

Now we check the esthetic:

1- The teeth don’t move during processing.2- The upper midline aligns with the middle of the face.3- The lower midline aligns with the upper midline.4- Orientation of occlusal plane: it might change in insertion, because during

flasking, part of the flask (which has upper and lower) might not close properly, resulting in teeth movement and therefore a change in the occlusal plane. If there is pressure anteriorly and the posterior part of the flask is not closed, this will result in sinking of anterior teeth, and vice versa.

Finally, we check the phonetics.

Causes of change in occlusal relation:1. Movement of teeth during processing.2. The material that we use, such as shrinking of acrylic resin.

Laboratory remount:

-the easiest way to get the denture after the flasking process is to break the cast.

- we do indices after flasking to put the master cast with the denture according to these indices and do laboratory remount, then we do selective grinding. If we miss to do this step, we can do clinical remount after you separate your denture from the cast.

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* Categories of occlusal errors in insertion:

1) very small discrepancy (<1mm) we fix it by chair-side occlusal adjustment, no need for clinical remount.

2) intermediate (up to 2mm) we fix it by clinical remount.

3) severe when its more than 5-6mm, we neither can fix it with chair-side adjustment nor by clinical remount. So we check the upper denture again and inspect the incisal edge and height of the teeth, otherwise we have to redo the whole lower denture. If we aren’t satisfied by both the upper and lower dentures, then we have to redo both of them.

* why is clinical remount better and easier than chair-side adjustment?

1- it allows you to do extraoral occlusal adjustment.

2-eliminates continual removal and replacement of the denture.

*Problems with chair-side adjustment

1- in chair-side adjustment we put articulating paper inside the patient’s mouth, then we ask the patient to occlude in centric relation, and in this case we can’t guarantee that the patient will close his mouth in centric relation because the articulating paper blocks the view.

2-saliva : which prevents intimate contact between teeth and articulating paper. So you have to repeatedly take the denture out and dry it which is time-consuming, since sometimes you’re going to have to do it 10 or even 12 times. Therefore, clinical remount is more time-saving, cleaner, neater, and easier to perform.

** Studies suggest that patients who received dentures done with clinical remount have fewer complaints than patients who received them with chair-side adjustment in post-insertion.

Clinical remount is a must, it allows identification of interference not seen intraorally.

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Using clinical remount, you can have a lingual view, which allows you to actually see if the centric cusps fit in the fossae. You also avoid reflexes from the patient (e.g. pain and denture movement).

*How to do clinical remount:

- after being done with all the previous steps, the denture should be retentive and should have no sharp edges. Then we do a precentric record, we guide the patient into centric relation, after placing two pieces of was on both posterior teeth only. The canine-to-canine area should be wax-free (to be useful as a reerence_. So you stabilize the lower denture with your index inger, then ask the patient to go into centric relation, and you test the very first contact in order to capture any premature contact, so technically the patient is not in a complete centric relation, hence the name “precentric”. Then we check intraorally that there was no perforation of the was, that’s how you know you caught the first premature contact. Then we check extraorally if we can put the upper denture in the upper ____?easily. Now, we can dismiss the patient and we work in the lab.

We mount the upper denture, and we put it on the articulator. We block any undercuts with gauze then we put Vaseline and we pour it with plaster.

We remove the wax posteriorly, then we take incisal pin out because we preserved the vertical dimension, then we do selective grinding.

Now we ollow the sequence of adjustment:

1) Adjustment of centric relation we put articulating paper in centric on one side and we open and close the articulator several times, then we flip the paper on the other side and unlock the articulator. Then we do lateral movement. There must be an even distribution of contact on posterior teeth and no contact on anterior teeth. Whatever is causing interference in both centric and eccentric and has both colors we grind it whether its functional or not. And if it causes interference only in centric (one color), we deepen the opposing fossa.

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2) Adjustment of lateral movements (working and balancing) A- Working: BULL rule (buccal for upper and lingual for lower). If we have

interference in centric functional cusp, we don’t touch the functional cusp, instead we adjust the interference by grinding buccal inclinator for upper lingual and lingual inclination for lower buccal.

Why don’t we trim the functional cusp? Because we will lose vertical dimension and free way space.B- Balancing relationship: if you move the mandible to one side, the

contace on working side will be buccal-buccal, and on the balancing side it will be lower buccal-upper lingual. If we have interference on working side, we trim the buccal. Low incisal inclination of lower buccal cusp, buccal inclination of upper palatal cusp. In balancing, we do our adjustment on lingual inclination of lower buccal cusp, this is more esthetic than buccal inclination of upper palatal cusp.

3) Adjustment of protrusive movement:In protrusion, our aim is to have simultaneous contact anteriorly and posteriorly.Adjustment in protrusion: two scenarios: either contact anteriorly and separation posteriorly or contact posteriorly and open bite anteriorly. If we don’t have proper contace anteriorly, we check the posterior teeth, if there is interference we adjust it(distal inclination of upper buccal cusp, mesial inclination of lower buccal cusp), if there is no interference posteriorly we adjust the anterior teeth (height of lower teeth or palatal of upper teeth).

-if we have heavy contact anteriorly and separation posteriorly ,we do adjustment on posterior aspect o upper incisal edges and labial aspect of lower incisal anteriorly (reduce height of lower teeth) .**we do the adjustment in 45 degree to prevent the formation of sharp edges.After finishing adjustment we should have:1-no anterior contact in centric relation.2-similtinious,uniform contact bilaterally in centric relation.

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3-similtinous contact in eccentric .4-similtanious contact in protrusive movement.

Then we remove the denture from the articulator ,polish it and finally give it to the pt.**intraorally:we use articulating paper to check the contact in centric,lateral,protrusive movement ,the contact should be the same we find it in articulator. How we polish the denture?1-pomis that we wet it with disinfectant such as chlorhexidine .2-polishing burs and sand paper.

Mastication with new denture: you have to ask the patient to eat soft food in small bites for at least one week bilaterally to stabilize the denture, then he can eat whatever he wants.

Speaking: Despite proper vertical dimension, proper freeway space, and proper position of anterior teeth, some patients might still be unsatisfied with their phonetics. So the best way to get used to it is by instructing them to go home and read something loudly, in this way it will take them hours instead of days to get used to it.

Oral hygiene: by using soft toothbrushes after each meal, brushing it from internal side, fitting surface, and polishing surface, at least with water. Its better to instruct them not to use toothpaste, because most patients use abrasive toothpaste that contains particles. They definitely have to brush their gums to stimulate circulation.

At night time they shouldn’t wear the denture, they should put it in a cup of water. They should have3 a minimum of 8 hours of rest for the patient, either at night time or day time.

The denture should not be cleaned by hot water because the acrylic will be affectied, it will not be usable anymore. So we just use tap water.

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Adhesive:

Not to be used regularly for new denture. If the denture has been done properly especially the upper one, we don’t use adhesive even if the upper denture is resorbed, we can give the patient retentive upper denture without adhesive.

Lower denture: most patients have lower denture with less retention than upper, which is normal, because we have much less surface area there.

The only time that we instruct the patient to use the adhesive:

1- psychologically new denture wearer that fears that the denture will move during eating or speaking, so we instruct him to use it just for the first few days or weeks, and to use only a small amount of it until he gets used to it.

2-in cases where the mandible is severely resorbed and the patient can’t get implants.

Minimum standard of care that you should ofer to your patient is upper conventional denture and lower implant retain, but because most patients can’t pay for implants so we make them a conventional denture for the lower.

Conventional denture patient with severe resorbed mandible and can’t afford implants we can give him adhesive in a specific amount and follow up every 3-6 months.

A specific type of adhesive that contains Zinc eugenol can cause Zinc toxicity, especially if the patient uses it in large amounts.