FINISHING MOUNTING WAXES
1.INTRODUCTION:
Once the functional test is completed, the next step will take place in the laboratory, this step goes through several phases from the finishing of the waxes to the cooking of the prostheses.
2. DEFINITION:
This phase consists of finishing the wax assembly and reproducing as much as possible the reliefs of the oral mucosa to mainly fulfill the aesthetic requirements and secondarily the functional requirements of making a prosthesis.
3.OBJECTIVES:
- Biomechanics: The condition of polished surfaces contributes directly and indirectly to improving biomechanical factors and different functions.
– Retention: facilitate the passive action of the paraprosthetic muscles on the extrados by controlling the volumes of the prosthetic bases, exploiting all favorable support surfaces to increase contact with saliva.
-Stability : a good distribution of the thicknesses of the wax models contributes to the release of muscle movements, ensures a balance between the buccinato-labial strap and the tongue.
-Mechanical resistance of prostheses through adequate control of wax volumes, to avoid fractures of the prostheses.
- Functional:
-Aesthetics: harmonious support of the lips and cheeks. -Restore the most natural smile possible by better finishing the gingival festoons and interdental papillae.
-Phonation: the finishes on the palatal vault must be as physiological as possible to improve the support of the tongue in this region.
-Chewing : the vestibular slopes must ensure better kinematics of the food bolus in the mouth and good deflection of the crushed food, for this it is necessary to sculpt these slopes well so that they are as natural as possible.
- Psychological: the finishes give the prostheses a more natural appearance, closer to the original teeth, which will improve the social integration of patients.
- Prophylactic: facilitates oral and prosthetic hygiene for the patient and reduces food retention on future prostheses
- Finishing of polished surfaces: Polished surfaces (wax) must respect the principles defined by Fish, namely: be oriented in such a way that the muscles in question tend to apply the prosthesis against the support surface.
- Conventional technique: the technique most used by technicians and practitioners consists of giving the models shapes appropriate to each region.
- The mandibular prosthesis:
- Conventional technique: the technique most used by technicians and practitioners consists of giving the models shapes appropriate to each region.
- Incisive region: vestibular and lingual concavity.
- Canine region: slight vestibular convexity and lingual concavity.
- 1st molar region : slight vestibular convexity and slight lingual concavity.
- 2nd molar region: vestibular concavity and slight lingual concavity.
- Trigone region: vestibular concavity and slight lingual concavity.
- The maxillary prosthesis:
- Incisive region: slight retroincisive convexity with straight or slightly convex vestibular profile.
- Canine region: slight palatal and vestibular convexity.
- Molar region: palatal concavity, slight vestibular convexity.
- Tuberosity region: palatal and vestibular concavity.
b. Special technique:
This technique consists of sculpting the polished surfaces of the extrados in their most physiological position, using the tertiary impression method.
-This technique consists of applying a moldable plastic material to the extrados of the prosthetic models which can be a delayed-setting resin or oral temperature plastic wax such as Adheseal. The practitioner makes a functional recording of the polished surfaces.
5. Gingival festoon position: These finishes concern the separation line between the necks of the artificial teeth, the mounting wax and the false papillary gingiva.
-The line of collars must be symmetrical on the right and left of each half-arch.
-Central incisors (IC) and canines (C) on the same line.
– Lateral incisors a little lower (because a little shorter) than IC and C.
-The parallelism between the level of the collars and the smile line (generally parallel)
6.finishing protocol:
a/ Thickness control : the thickness of the wax must be 1.5 mm at the level of the palatine vault, tuberosity and trigone region, without affecting the thickness of the peripheral seal.
For better control, a periodontal probe can be used
b/ Addition of wax and homogenization: wax is poured along the vestibular and buccal gingival festoon to adjust and homogenize the thickness of the gum using a hot spatula.
c/Gingival scalloping: using a sculpting spatula, a line is drawn at the level of the collar lines chosen in relation to age, the smile line, and even in relation to the patient’s wishes.
d/Sculpture of the false gum:
-false marginal gum: we will try to reproduce its natural curve, but without sculpting the gingivo-dental groove and this for reasons of hygiene.
-false papillary gingiva: the sculpture here aims to give this gingiva a concave appearance with a junction extending to the point of contact.
– Attached false gum: it is sculpted so as to reproduce, if possible, the curves of the false roots corresponding to each tooth.
e/Simulations: the bunoid papillae can be simulated at the level of the false palate for good integration of the prosthesis in the oral environment.
f/Final finishing: once the sculptures are finished, we finalize by quickly passing the models over the flame or using a flame blower.
POLYMERIZATION OF THE PROSTHESIS
1. Definition: Polymerization is the laboratory step consisting of replacing the wax of the teeth assembly with a material (acrylic resin), bio-compatible, resistant to oral pressure, physical and thermal shocks and allowing the fixing of prosthetic teeth.
2. Preparation of assembly models Checking the thickness of each model: must be uniform at all points (1.5 mm center and 2.5 mm periphery).
-To secure the models: the wax must be poured over the entire periphery of the support surface, thus creating a flawless seal.
-Finishing of waxes: in order to considerably reduce the time spent in the laboratory after polymerization and especially to avoid having to touch up the surface of the extrados of the prosthesis, the superficial layer of which is the most compressed, the most homogeneous and the best polymerized.
3. Mittens : a mitten must include:
-A base part in which the model and its template will be placed,
-A counterpart in which the artificial teeth will be housed.
-A cover,
-A guidance system ensures the adaptation of the different parts,
-A fixing system (flange or keys)
Choice of blocks: depends on the dimensions of the models. There are the flange block and the key block.
Their choices are rather managed by the practical conditions and their availability in the laboratory. It is necessary to check:
-That the model fits completely into the muffle
-The posterior regions do not interfere with the mitten
-Any undercut on the model that could block the demoulding must be removed.
-The counterpart if it does not interfere with the model
-the ratio of the teeth to the ceiling of the counterpart
– the intimacy of contact between the two parts of the mitten before and after trying on the models.
4. Putting in a mitten
The imperatives:
– Be carried out in a muffle of width and length in relation to the volume of the model and its mock-up.
-Ensure a plaster thickness at all points exceeding 1cm.
-Allow recovery of models.
-Ensure the separation of the different parts of the muffle.
-Predict and compensate for all expansions of the acrylic resin during polymerization.
-Remove, eliminate any risk of excess thickness, distortion or porosity.
Practical implementation:
-Vaseline the base of the model (insulation) to ensure its easy recovery after polymerization,
-Vaseliner or varnish all parts of the mitten,
-The undercut areas of the model will be unloaded,
-Fill the part of the mitten with a plaster of fluid consistency,
-Place the model and the mock-up so that the incisal block and the anterior alveolar rim are placed vertically,
-Before setting the plaster, remove all undercut areas,
-Remove all traces of plaster from the edges of the muffle and the wax model,
-Let the plaster crystallize, then the Vaseliner to separate the two parts,
-Place the counterpart in good contact with the part,
-Place the muffle on a vibrator and fill the counterpart,
-After one hour of crystallization, the muffle is placed in a container of water,
– When boiling, the muffle is removed, the two parts will be separated and cleaned, until all traces of wax have completely disappeared,
-The varnish is then applied with a brush, after having dried both parts properly.
5. SCALDING
Definition: This is a step that consists of melting the wax of the assembly to prepare the space for the resin of the future prosthetic base. Clean the models and the teeth of any impurities that could contaminate or harm the resin.
6. STUFFING:
Definition: This is the laboratory step that consists of stuffing the resin into the space left by the melted wax. This step begins with the choice of resin and ends with the closing of the mittens.
-Materials used: the materials must have biological, physical, aesthetic and technical properties, the practitioner generally has two types of resin: chemo-polymerizable R. and thermo-polymerizable R., we generally opt for hot R. for their biological, physical and aesthetic quality.
-The rules of mixing:
-Respect the powder/liquid ratio (polymer/monomer) according to the supplier’s instructions, for better dimensional stability and fewer allergic effects.
-The principle of dosage is the complete saturation of all the molecules of the polymer by the monomer
-The purity of the mixture is a very important condition for the success of this step, hence:
-The use of an insulator compatible with the materials used
-Avoid using petroleum jelly.
-Ensure the cleanliness of mixing containers and mixing instruments
-Cover the resin while it sets
-Cleaning hands during handling
-After placing a sheet of cellophane between the part and the counterpart, the muffle is closed and placed under pressure.
7. The cooking cycle:
Once the stuffing is finished and the mittens are closed, we move on to cooking the thermo-polymerizable resin, this cooking is done according to a cycle composed of three temperature stages:
1: heating up to 100°C
2: temperature stabilization at 100°C for 30 minutes
3: turn off the heat and let it cool for up to 15 hours according to SANGIUOLO
8. De-muffling:
-Separation of the model after separation of the different parts of the muffle.
-The prostheses are carefully separated from their models,
-A metal or carborundum tip can be used to remove all peripheral burrs from the resin,
-A first polishing is undertaken with sandpaper pads mounted on a mandrel,
-A second polishing with brushes of different sizes and pumice stone,
-The last polishing with alumina powder and a special brush,
-The prostheses are washed carefully.
9. Handling errors
– Wrong orientation of the model and its mock-up in the muffle
– Presence of traces of humidity before stuffing or poor quality insulation,
– Failure to respect the powder/liquid ratio,
-The presence of impurities,
– Absorption of water and liquid
– Too rapid or too sudden rise in temperature during polymerization as well as rapid cooling after polymerization,
-Opening the muffle before cooling,
These errors are the cause of either deformations or porosities in the prosthesis.
FINISHING MOUNTING WAXES
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Misaligned teeth can cause difficulty chewing.
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Antiseptic mouthwashes reduce bacteria that cause bad breath.
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A soft-bristled toothbrush preserves enamel and gums.