|Year : 2012 | Volume
| Issue : 4 | Page : 150-154
Proposed technique for fabricating complete denture
Abdulsalam Ali Zwiad
Dental Department, Faculty of Medical Sciences, Queen Arwa University, Yemen
|Date of Web Publication||5-Feb-2013|
Abdulsalam Ali Zwiad
P.O.box 2436 Sana`a
Source of Support: None, Conflict of Interest: None
Introduction: Reduction of the visits for fabricating complete dentures are welcomed by both dentists and patients and this might be an aspect of the new changes in prosthodontic treatment according to the suggested new methods. Clinical Innovation: Complete dentures fabricated by the technique described in this report reduce processing time, cost and efforts since the technique does not require the use of gypsum materials, metal flasks or other related materials to obtain a mold for packing the heat cured acrylic resin as might be needed with the conventional method. This method requires only an appropriate volume of silicone impression material to provide the required mold and a heat pressure machine for processing and polymerization of the heat-cured acrylic resin. Although this technique might be difficult to be applicable by all dentist but it could be consider an advisable method. Discussion: Because the record base in this technique is made of heat cured resin, it provides a reliable denture base with better retention and stability and it overcomes the shortcomings that may be faced during registration of vertical dimension. This technique meets the basic requirements for a successful complete denture which is well tolerated by the patient's mouth.
Keywords: Acrylic, denture, polymerization, technique
|How to cite this article:|
Zwiad AA. Proposed technique for fabricating complete denture. Dent Hypotheses 2012;3:150-4
| Introduction|| |
Fabricating completedentures commonly requires five visits. Reduction of the number of these visits would be welcomed by both dentists and patients.  Various aspects of prosthodontic treatment may change as a result of new treatment options and evidence from studies.  Complete acrylic dentures may be polymerized by many methods including conventional, injection and microwave techniques.  These techniques usually utilize plaster gypsum material, metal flasks and other equipment to prepare the required mold in which the polymethyle methacrylate dough is injected and polymerized. Acrylic resins were introduced in dentistry in 1937, and to date, no other material does as well in conveying the appearance of oral soft tissues and, as a result, it is widely used for the construction of complete dentures. , Skinner and Cooper  have suggested that a certain lack of dimensional stability must be accepted because the polymethyl methacrylate denture base undergoes unavoidable thermal expansion on heating and contraction on cooling, , To a certain extent, these contractions may be balanced by expansion resulting from water absorption. , Dimensional change in the conventional molding technique can be inevitable as a result of overfilling of the mold.  The injection molding technique results in a slightly reduced increase of the vertical dimension of occlusion than does the conventional technique.  The time provided for a dough acrylic to be moldable should be not less than 5 minutes (ADA specification No.12). The current technique may also allow processing single tooth partial dentures, surgical splints or repairing acrylic dentures.  By increasing the polymerization temperature, the monomers are diffused more effectively into acrylic resin polymer teeth, increasing the bond strength between the polymer teeth and the denture base polymer. 
This study suggests an alternative technique for polymerizing a polymethyl methacrylate denture base to serve both as a record base and a denture base. The technique assists in providing a stable record base and accurate measurements of vertical and centric relations.
| Clinical Innovation|| |
- Mark the vibrating line inside the patient's mouth before making the maxillary impression.
- Make the maxillary final impression using irreversible hydrocolloid impression material, ensuring that the imprint of the vibrating line is transferred clearly onto the final impression.
- Pour a mixture of stone gypsum material into the final impression to produce the maxillary working cast including an imprint of the vibrating line.
- Make the vibrating line bolder then carve the post-dam area on the stone cast [Figure 1].
|Figure 1: A view of the vibrating line imprinted on the maxillary working cast|
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- After making the mandibular impression, pour the stone gypsum material into it to produce the mandibular working cast as with the conventional method.
- Rather than using a separating medium, immerse the working casts in a tap water bath for few minutes to liberate air-bubbles.
- Mix the polymer and monomer hot curing acrylic resin (Triplex hot- Type I Class I, Ivoclar Liechtenstein) at a 1:3 ratio to prepare acrylic resin dough.
- Place and adapt the resin dough material onto the maxillary and mandibular casts, removing any excess resin material.
- Wrap each component of the adapted resin dough and its cast in a piece of aluminum foil [Figure 2], and then introduce it into the heat pressure machine to produce a polymerized record base (denture base).
|Figure 2: Dough acrylic resin is adapted on the working cast and wrapped in aluminum foil for the polymerization cycle|
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- Set the machine at 120°C, 3 bar and 20 minutes for the polymerization cycle, then wait for the machine to shut down automatically.
- After the setting time, remove the polymerized denture base and unwrap from the aluminum foil. When the record base has cooled, separate it from its cast.
- Using a soft pen, mark and determine the borders and the notches of the record bases
- Trim and polish the record bases to their adequate forms and extensions of the border.
- Check the finished record bases on their casts as well as in the patient's mouth to ensure adequate adaptation, extension, stability and retention [Figure 3].
|Figure 3: The finished denture base on the cast. It is glossy, free from porosity and well adapted to the cast and in the patients' mouth|
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- Build up the maxillary and mandibular occlusal wax rims on the fabricated denture bases.
- Establish the vertical and centric relations and fix these relations on the articulator.
- Arrange the artificial teeth to obtain the trial denture.
- Establish an index-mold for the trial denture using the following procedures:
- While the trial denture is still attached to the articulator, manipulate an appropriate amount of polysiloxane silicone putty-type impression material (Zetaplus-Zhermack - Rovigo -Italy) and adapt it between the maxillary and mandibular teeth, pressing it to extend over all the teeth and the supporting structures.
- Draw three red arrows on the different sides of the casts to coincide with similar arrows on the silicone index-mold to serve as guide-lines during removing and replacing the index to its position.
- Be sure that the incisal pin touches the incisal table of the articulator in ultimate contact to ensure the correct occlusal relationships [Figure 4].
|Figure 4: Putty-type silicone impression material is adapted on the trial denture to form the index mold that the incisal pin and the incisal table should be in ultimate contact|
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- Release the index-mold from the articulator and melt the modeling wax by immersing it in a hot water for five minutes. Then wash and clean the silicone mold, teeth and the record bases to ensure that they are free from any particles of wax. Retain the record bases for the subsequent procedures.
- Allow the index within the artificial teeth to cool down and reposition any tilted tooth to its correct place in the mold [Figure 5].
|Figure 5: A view of the trial denture shows elimination of wax completely from the index mold and the teeth are in their correct positions|
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- Manipulate a small amount of acrylic resin hot type dough (Triplex hot-Type I Class I, Ivoclar Liechtenstein) in a 1:3 mixing ratio and press it onto the artificial teeth, using monomer to liquefy and facilitate flow of the dough material into the interproximal surfaces of the teeth.
- Seat the mandibular record base on the layer of acrylic resin dough with a slight pressure; repeat this process for the maxillary record base.
- Return the whole component of the index-mold to its position on the articulator, pressing the upper arm to ensure ultimate contact between the incisal pin and the incisal table, and that the red guide lines coincide, and then remove any excess resin material.
- Once again, separate the index-mold from the articulator, wrap the components in aluminum-foil, and introduce them into the heat pressure machine for the polymerization process (120°C, 3 Bar and 20 minutes for the cycle time).
- After the setting time, take out the complete denture, remove the aluminum foil [Figure 6], and trim any undesirable extension. Follow the conventional steps for polishing a complete denture.
- The finished denture is ready to be inserted into the patient's mouth [Figure 7].
| Discussion|| |
The denture base prepared in this technique does not show porosity when examined with the naked eye and seems to be well tolerated and very good retention in the patient's mouth. Although it has had indirect contact with the water in the processing machine and is subjected to some water absorption, it shows a correct polymerization result without signs of defects. Wong DM has suggested that such a finished denture may have contracted and these contractions may be balanced to a certain extent by expansion resulting from water absorption.  The technique described here provides a more reliable and accurate record base on which to record the measurements of vertical and centric relations as compared to use of an auto-polymerized resin or shellac record base. Moreover, the technique provides the record base serves as the final denture base due to its reliability. The accuracy of such a record base is the result of the fact that heat-cured acrylic resin has a negligible dimensional change as compared with auto-polymerized acrylic resin. As a result, the shortcomings of an auto-polymerized acrylic resin are overcome from the beginning and the record base can be checked in a stable condition without the probability of continuous drop down during the trial denture check, particularly during checking variety measurements on the upper record base for construction of the complete denture. In addition, with this technique, the denture base does not exhibit adherence of gypsum particles on the inter-proximal surfaces of the teeth as may occur with the conventional method. This is due to the fact that the current technique involves use of a smooth media of silicone material to provide the mold rather than a gypsum mold. The denture produced by this technique exhibits the basic requirements for a successful complete denture, providing adequate retention and stability. It is glossy, free from porosity and, after an acceptable level of selective grinding, the occlusal relationship is accurate. The thickness was controlled as any daily work in fabricating a denture baseduring the dough stage and followed by trimming and finishing process at final. May be not all dentists could apply the technique due to the variations in their laboratory skills, but sure any dental technique can do the technique by follow the mentioned procedures. This technique has advantages of excluding many instruments and materials that may be required for the conventional method. Concerning the residual monomer of the polymerized record base, a previous study showed it is acceptable.  used the gas liquid chromatograph test (GLCT) to evaluate two types of polymerized acrylic denture base (Ivoclar and Quyle Dent. products) in a heat pressure polymerizing machine. That study showed that the assessed residual monomers were 0.438% and 0.349% respectively and these percentages are significant as compared with the findings of Austin A.T. and Basker R.M., , who found that a percentage of 1.6% of residual monomer is reliable. Also, it has been documented that a level of more than 2% of residual monomer in an activated acrylic denture base can produce adverse effects on the mechanical properties and may cause mucosal and allergic reactions. ,
| Suggestions for Further Assessment|| |
Regarding to this innovation I suggest assessing and evaluating hardness of denture base produces by this technique in compare with the conventional method.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]