To fabricate another set of an existing denture . This procedure has certain indications which will be discussed in detail .
During the first visit of a patient , proper examination should be conducted in order to construct a proper treatment plan .
A complete denture consists of 3 surfaces :
1. Fitting surface
2. Polish surface
3. Occlusal surface
Each of the 3 surfaces should be examined thoroughly .
We start with the fitting surface . We can assess the fitting surface by first inspecting the oral tissues , and looking for any ulcers or lesions caused by ill fitting dentures . Another way to assess it is by applying alternative pressure on both sides of the denture intraorally. An ill fitting denture will rock , due to irregular resorption of bone in different areas . The patient’s own complaints are also taken into consideration.
Unretentive denture is not a very reliable factor , as many errors could cause the denture to be unretentive .
Then we move to the occlusal surface .We start by visually observing the occlusion by instructing the patient to bite on his teeth and looking for any occlusal problems. The patient’s complaints are also of significance ; a common complaint coming from patients wearing old dentures is that their denture is not cutting food efficiently anymore mainly due to wear of teeth . A problem which can be clearly identified even extraorally .
Reduced lower facial height caused by low VDO could also be observed . Leading to multiple problems such as angular cheilitis and accentuated wrinkles.
Polish surfaces are also examined by visual examination first . We inspect the denture and note if there is any discoloration or pores . These unpleasant features are not critical in deciding to fabricate a replica though , as these features could be easily eliminated by rebasing . Intraorally we make sure that the lips are seating the denture properly and thus help in retention and don’t dislodge the denture out of place . What really matters in deciding on a replica is that the patient has been wearing his denture for a long time , and so , close adaptation of the oral cavity and surrounding muscles and tissues has developed to the existing denture .So this close relationship is what we aim to preserve by creating a replica .
Regarding the support the denture provides to the circumoral tissues , we don’t expect it to be a problem since the denture is old and any problems regarding the support of the lips and cheeks should have been addressed at the time of insertion long ago .
After inspecting the denture thoroughly , taking into consideration the previous aspects , a sound decision to make a denture duplicate could be made .
Treatment options :
Different scenarios will be discussed .
* All the surfaces of the denture are acceptable , such as when a patient presents to your clinic informing you that his denture is perfectly fine . But that he can’t at any minute afford to lose or break his denture . In this case , denture duplication is appropriate , as a spare denture .(1)
* The fitting surface is not acceptable , it is not stable and it is causing tissue ulceration . The rest of the surfaces are acceptable .The treatment option in this case should be rebasing or relining , depending on the percentage of The defective surface ( if the entire surface was ill fitting , we tend to do rebasing ) (2)
* The fitting surface is satisfactory .The occlusal surface is not stisfactory , eg. the teeth were suffering severe attrition causing low VDO . Attempting to correct the occlusion should be considered first . The usual occlusal adjustments could be carried out . Clinical remounts , using aticulating paper , or even removing the teeth and replacing them with wax rims and have a new set of teeth placed . If those adjustments did not work , a new replica is constructed and the occlusal modifications are carried on the new denture .
Another similar scenario is when the patient is skeptical about the modifications to be carried out on his denture , and he fears that the dentist is going to ruin it . In that case we fabricate a duplicate denture , adjust the new denture to our satisfaction , all the while the patient is keeping his old denture . And then the new denture is delivered to the patient to judge its improvement .(3)
* The fitting surface and the occlusal surfaces are not acceptable , but the patient is hanging on to his denture saying that he's been wearing it for a long time , but recently it has become loose and doesn’t cut food efficiently . A denture duplicate can be fabricated , or a new denture if the patient gives his consent and is comfortable with the new one . In most cases , a denture duplicate is what the patients want since they are old and cannot adapt easily to a new denture , even if their old denture lacks stability or retention . But as it has been a part of their mouths for a long time , the muscles learn how to seat the denture and keep it in place . (4)
Oral proprioceptors are responsible for the adaptation process . And the younger the patient , the easier the adaptation . Which is an aspect of major importance in this field of dentistry . Therefore , a denture replica might be the only solution in some cases .
*If upon examination , neither the dentist nor the patient is satisfied , a new denture is needed .(5)
Very old patients with very old dentures . This is the first solution that jumps into mind , as they are considered ideal candidates for this procedure . Unless there is sufficient bone , and the patient can afford them , implants are also an option . Or an implant retained over denture , with 2-4 implants .
Worn occlusal surface , with satisfactory other surfaces .
A patient with unpleasant experience with previous dentures .In this case, we ask the patient to choose the most comfortable denture of the ones he has . That denture is duplicated and adjusted , so that you don’t have to start from scratch .You’re merely improving a denture that the patient thinks is the most satisfactory of the ones he has .
For a patient satisfied with his existing denture , but needs a spare denture to be available at all times .
Advantages of denture duplication :
Preserving satisfactory features in a denture , and further improve it .
Occlusal registration is a little easier than the conventional method
The number of clinics needed is reduced . 3 sessions if the fitting surface is to be adjusted . 4 sessions if the fitting and occlusal surfaces are defective .
Accurate alteration of undesirable features .
Techniques of fabrication of a denture duplicate
Many techniques exist to accomplish that . Naming :
The flask method , which is the most common one .
The agar container method .
The soap container method .It is an easy and simple method , therefore , it will be discussed in details in this lecture .
The soap container method :
- Used if no alterations are needed to the denture .
In the first visit proper examination is done first . Then the old denture is obtained from the patient as the new denture duplication is pure laboratory work in which the old denture is needed .
In the same visit , a new teeth shade could be selected if the old shade is not pleasing .
Laboratory steps :
4 measures of alginate mix are placed in one compartment of the soap box , after mixing them with the right water ratio ( the measure could differ according to the size ) . The denture is then placed on top of the mix with the fitting surface directed upwards and squeezed in so as the borders of the denture are in level with the top of the mix and the upper borders of the soap box . Enough alginate should be used in order to avoid pockets and bubbles .
Another alginate mix ( approximately 4 measures ) is prepared and placed on top of the fitting surface and into the other compartment of the soap box and then the two compartments are joined together tightly so as the ledge on the box is closed .Excess material should flow out of the box , indicating that enough material was used .
Note that after the first mix of alginate becomes set , petroleum jelly is spread over the alginate ( not the denture ) to avoid adhesion between the two compartments as they join together .
After all the alginate has set , the two halves are separated and the denture removed .2 sprues or tunnels are carved , through which the acrylic material will be poured into the space previously occupied by the denture .
The zone occupied by the teeth is filled with wax . The best way to do that , is by shaping the wax sheet into a roll , heating it until it melts and dripping the molten wax into the space until it reaches the neck of the teeth .
The two halves are then joined back together , making sure that the ledge is closed to ensure that the complex closed in the same way as before . And then a rubber band is placed to secure the complex .
Flowy auto-polymerization resin is then poured from one side until it floods from the other side .We try to use excess material , in attempt to compensate for the polymerizing shrinkage that occurs .
If no alterations are needed , the denture is placed on the articulator and the teeth are set precisely in place of the wax teeth . Then a try-in procedure is done. If all is satisfactory , the denture is sent back to the lab , flasked , processed and finished in the conventional way . And the denture is now ready to be delivered to the patient .
-If any alterations are needed to the fitting surface ( supposing they do not change the occlusal relationship ) , an impression is made during the try in stage with a light body material using the denture itself as a tray . This step is also done if we doubt the accuracy of our procedure even if no alterations to the fitting surface are needed , since acryl is not a stable material and some changes might occur during the polymerization of the cold cure acrylic .
The impression is made using the closed mouth technique to ensure that the occlusal relationship has not changed . The denture is then sent to lab to be processed in the conventional method .
-If occlusal alterations are needed , they are also addressed at the try in stage .
Loss of VDO is common in old dentures . Sometimes the free way space could measure up to 20 mm . Reducing it back to the normal 4 mm is very hard , even if it was gradual , as the patient might need a set of 5-6 dentures to achieve that gradual change . So some form of compromise is required here . Reducing the FWS to 8 or 10 mm is considered acceptable . It is acceptable for the patient , as he is not irritated by a vast increase in the VDO causing his facial muscles to stretch , and for the dentist , as the FWS is at least half way to the normal , helping the patient avoid the disadvantages of reduced VDO .
So if the dentist decided to raise the bite , he should determine exactly how much he wants to raise it during the first visit.
In the try in stage , first the dentist should make sure that the teeth are kept in their original location , as they make a part of the polish surface and it’s not in our plan to alter it .
Aluwax ( aluminum containing wax ) is used to raise the bite . Aluwax is soft when heated and hardens when it cools , making it ideal for occlusal registration. Some excess is used to account for the material that flows due to the occlusal force when biting on it . Then the denture is sent back to the lab for processing .