Secondary impressions in total prosthesis
PLAN
INTRODUCTION
- Definition
- Objectives, role, goals, imperatives
- Choice of impression material
- The different secondary impression techniques
- Study and description of the main analytical fingerprints
- Analytical fingerprints under digital pressure:
- Anatomical functional fingerprints
- Analytical fingerprints obtained without any pressure
- Analytical prints involving a thermoplastic material at 70°
- Analytical impressions under occlusal pressure:
- Impressions of a single-maxillary edentulism
- Analytical impressions of a bimaxillary edentulation under occlusal pressure
- Footprints seeking conditioning of the support surfaces
– Processing of secondary prints in the laboratory
- Materials used for casting models
- Formwork of the prints
- Casting the prints
- Occlusion bases
CONCLUSION
BIBLIOGRAPHY
Secondary impressions in total prosthesis
1-Definition:
It is a definitive impression from which the complete prosthesis will be built, it is obtained with an individual impression tray from the preliminary mucostatic or dynamic impression. It prefigures the prosthetic base of the future prosthesis, it must respect the anatomy and physiology of the support surfaces and satisfy all functional, aesthetic and phonetic requirements.
2- Objectives:
It must comply with the following requirements:
- Mechanical requirements:
Made up of the search for the balance of the prosthesis at rest and during all functions and facial expressions, this balance depends on the physical factors represented by adhesion, cohesion, atmospheric pressure and the anatomofunctional factors represented by:
- Anatomy and physiology of the support surface:
-The larger the support surface, the greater the adhesion and retention;
-The greater the bone relief, the greater the retention and stability;
-The stability of the prosthesis during mastication depends on the value of adhesion, depressibility and the degree of resilience of the covering tissues.
- The reflection areas of the mucosa and the underlying elements:
-The depth and the depressibility of the reflection zones of the mucosa determine the value of the peripheral seal, however the extension of the slopes of the prosthesis must be sufficient so that the play of the muscles in action applies the mucosa on its edges, thus ensuring a perfect peripheral seal.
- Anatomy and physiology of peripheral organs:
-Determine the height and thickness of the edges of the prosthesis so that stability is at its maximum during physiological movements, the prosthesis must occupy the useful passive space.
B- Biological imperatives:
Essentially consisting of respect for the integrity of the different parts of the support surface; to avoid bone resorption by osteolysis, it is necessary to prohibit any abnormal compression of the mucosa, fibromucosa or poorly protected vascular pathways.
C- Aesthetic, functional and phonetic imperatives:
The imprint must restore the aesthetics which constitute the only valid guide to the replacement of tissues in their original physiological position.
The resulting prosthesis must be stable during all functions; its edges and polished surfaces must be in harmony with all the muscles involved during the functions.
3- The different secondary impression techniques:
– Analytical fingerprints under digital pressure
– Analytical impressions under occlusal pressure
– Analytical conditioning fingerprints
A- Secondary impression under digital pressure:
- Indication:
– any compression must be excluded;
– the patient is unable to provide us with effective cooperation
– successful neuro-muscular or neuro-articular preparation;
– financial conditions are limited;
– the patient’s nervous state would not cope well with sessions that are too long.
– the time spent taking prints is limited.
- Classification:
1-Simple anatomical and functional impression:
They can successfully resolve the majority of cases, excluding those where the covering tissues are hyperemic, floating or detached from the underlying bone.
- Analytical impression of the upper edentulous arch:
- PEI mouth test:
When the individual impression tray is in agreement with the tracing on the model, the next step is to look for its functional limits in the mouth.
- Static tests:
If the individual impression tray is mobilized while no movement is made; the overextensions intervene on the very anatomy of the vestibule.
The mucosal reflection line should be visible at a distance from the PEI, the edges of which should remain set back except at the level of the paratuberous regions.
Every notch at the level of a frenulum or a muscle insertion must be noted.
- Dynamic tests:
Extreme opening, yawning, lateralities: the interference is located at the level of the paratuberous pockets and the second molars.
Secondary impressions in total prosthesis
Secondary impressions in total prosthesis
The patient is asked to raise the chin to the right and left, mouth half-closed, the interference is eliminated on the responsible side.
Forced laughter, hollowing of the cheeks: this test focuses on the activity of the buccinator which mobilizes the jugal mucosa and the lateral brakes whose functional freedom must be ensured.
Secondary impressions in total prosthesis
Mimic the kiss: it is the anterior area that is concerned; the instability can be due to an exaggerated or insufficient notch of the median frenulum or to an excess thickness of the edges.
Secondary impressions in total prosthesis
Adjustment of the individual impression tray limit at the soft palate region: the impression tray should cover 1 to 2 mm of the area extending from the hard palate/soft palate boundary to the most posterior vibration line of the soft palate without hindering the functional movements of the soft palate.
The individual impression tray is placed in the mouth, the practitioner ensures that this area is covered and then checks that it does not hinder the functional lowering of the veil by making the patient blow through the nose, with the nostrils blocked, the individual impression tray must not be expelled otherwise its distal extension must be reduced. The pterygomaxillary ligaments must be released and checked by the maximum opening.
b) Recording of the peripheral seal:
The recording is conducted methodically using green KERR paste superficially heated with the HANAU torch.
- Sectors 1 and 2: they concern the volume of the paratuberous pockets of EINSERING requiring a significant quantity of KERR paste; the patient repeats the forced opening and lateral movements in a semi-open mouth; a stability check is carried out by exerting digital pressure on the ridge on the opposite side.
- Sectors 3 and 4: they concern the recording of the activity of the buccinators and the mobility of the lateral brakes; the movements requested consist of hollowing the cheeks by sucking the operator’s finger which holds the base in place.
A clean-looking, rounded edge indicates proper recording.
- Sector 5: from canine to canine, the paste records the volume of the labial vestibule and the mobility of the median frenulum and sometimes the two small paramedian frenulums; the lip is stretched downwards, the patient simulates the kiss; a small quantity of paste is necessary. A correct recording must respect the philtral gutter and the aesthetic appearance of the face.
- Sector 6: this is the posterior seal which ensures the hydraulic blockage; the KERR paste deposited in a significant quantity 1cm wide and 3 to 4mm high in order to record the amplitude of the elevation of the soft palate in function and with light pressure, no material is placed in the areas opposite the tuberosities. The patient is asked to pronounce AH grave for as long as possible, which has the effect of raising the soft palate in its most mobile part.
The material grasps this position in slight compression. At the end of the pronunciation the veil lowers by releasing exerts a force on the material and leaves an imprint which will be the most distal part of the flexion zone of the veil. The effectiveness of the seal is checked by exerting pressure on the anterior part of the occlusal rim during the pronunciation of the low AH, the base must not come loose.
To assess stability and retention the following tests are performed:
- Pressure applied to the molar segment to check the thickness of the edge on the opposite side at the paratuberous region.
- Maximum mouth opening: to detect overextensions of the edges in the paratuberous and pterygomaxillary regions.
- Emission of A and ON determines the flexion line of the veil which must be covered by the posterior edge of the PEI.
- Emission of U and OU for interference in the anterior vestibular region.
If the retention is not or no longer effective, it is necessary to look for:
– Compression of an elastic mucous membrane area.
-A decentering of the individual impression tray when recording a sector, which has the effect of rendering previous recordings ineffective.
- Footprint of the support surface: It has a dual purpose:
- Finely record the smallest details of the support surface to allow close contact between the base and the underlying mucosa.
- Record these same surfaces whose objective is to account for their support value in quality: support zones and zones to be unloaded.
The profile of the support surfaces determines the type of impression material to be used; a flat palate with a covering mucosa that is uniform in quality and adherent to the deep planes allows for a material of medium viscosity because the evacuation of the material is easy;
Whereas a hollow palate predisposes a very fluid material to flow easily.
Depending on the anatomy of the support surfaces, the individual impression tray can be completely or partially spaced; in cases of particularly depressible and viscoelastic Schroeder zones; the creation of two vents at their center is essential.
Secondary impressions in total prosthesis
- Technique:
The material is spatulated and loaded without excess into the individual impression tray, the latter is placed in the mouth and the patient tilts his head forward. It is first inserted in its distal part then tilted and pushed forward slowly without excessive pressure.
When it is almost in place, the operator places his fingers at the level of the 5th and 6th balance centers of the future prostheses to exert this time a controlled digital pressure allowing a correct positioning of the individual impression tray. The operator is placed behind the patient to properly direct his pressure in the support polygon of the bases.
The individual impression tray is held by a single finger in the middle of the palate while the patient must repeat the gestures and facial expressions used to create the peripheral seal; during the entire polymerization of the material, the assembly is held in place without any pressure.
The quality of the surfacing is checked by ensuring the uniform thickness of the material.
- Materials used:
- Zinc oxide eugenol pastes: this is the material of choice for maxillary secondary impressions and is quickly removed from the individual impression tray.
- Polysulfide elastomers: example PERMLASTIC light; do not put too much on the Kerr paste of the peripheral seal because they contain a solvent
- Silicone elastomers: too fluid, easily eliminated at the slightest compression on the mucous membrane; medium and heavy viscosities allow the peripheral seal to be perfected, which makes them unfavorable for this use.
- Analytical impression of the mandibular edentulous arch:
- Testing the individual impression tray in the mouth:
Lateral zone : the rim provides support for the cheeks and respects the lingual volume and the available prosthetic space, taking into account muscle tone.
Anterior zone : the rim respects and exploits lingual mobility thanks to a concave internal profile in which the tongue is placed to shape the sublingual seal
- Individual tray edge adjustment tests:
Which allow the elimination of overextensions ensuring the release of muscle and ligament insertions. Medium amplitude tests are used to find interferences:
In the labial region: traction of the lower lip horizontally, the edge of the PEI must be 1 mm from the reflection line of the mucosa, the freedom of the medial and lateral frenulums is checked.
Average mouth opening for the buccinator region
Wide mouth opening for the masseter region
Maximum mouth opening for the retromolar region
Moderate movement of the tip of the tongue towards the upper lip
Tongue movement during the pretense of moistening the lip or searching for food on the arch for the mylohyoid region
Maximum tongue elevation for the frenulum region of the tongue .
Secondary impressions in total prosthesis
- Recording the peripheral seal:
Sublingual region:
The lingual edge is lined in its anterior part: from left premolar to right premolar with green Kerr paste.
The PEI is placed, held firmly while the patient is asked to perform the following movements:
- To bring the tongue level with the palate.
- Slowly lick your upper lip from the right corner to the left corner.
- Slowly lick your lower lip.
- Touch the right and left cheek.
- Pronounce “ME, MA, MI” which define three floor positions.
- To swallow.
- Pull the tongue completely out and forward (depth of the lingual frenulum
The extension is considered satisfactory in the case where the removal of the PEI is carried out with a particular suction noise, it is essential to move on to the realization of the following extensions:
- Posterior vestibular region: Kerr paste remargination is performed during large-amplitude opening movements while the PEI is held firmly on the support surface using both index fingers.
- Mylohyoid region: extension at this level is often poorly tolerated, it must be limited to 2 to 3 mm below the line.
- Footprint of the support surface:
The coating is actually the application of a thin layer of product on the intrados and the edges; there is no point in applying a large quantity which could hinder the movements required of the patient.
The loaded individual impression tray is placed in the mouth, it is first inserted into the area of the lingual flaps often slightly undercut then tilted forward. The practitioner, placed in front of the patient this time, exerts bilateral pressure at the level of the 6th and 5th balance centers of the future prostheses.
Once the PEI is assured to be in place, the patient is asked to repeat the gestures and facial expressions used to adjust and record the sublingual seal, finally the assembly is held in place without pressure while the material is completely setting.
- Materials used:
- Zinc oxide eugenol pastes: most often used for their dimensional stability quality
- Polysulfide elastomers: the marginal compression sought at the mandible as well as the reduced support surface promoting the escape of the material require the use of compressive materials.
- Polyethers: These products also work very well for mandibular secondary impressions.
- Silicone Elastomers: not very suitable for mandibular impressions.
2 – Secondary anatomical-functional impressions obtained without any pressure:
They are indicated in the case where:
- The covering tissues of the supporting surface are hyperemic, fragile, or detached from the underlying bone.
Same step as the previous technique, the elements that differ are:
- The preliminary plaster impression is essential.
- A discharge on the model of the static part is carried out with a spacing of I to 1.5 mm, during the PEI test the spacing wax will remain at the level of the intrados.
- The spacer wax remains after the peripheral seal is made.
- The PEI is perforated with a 2 cm number 12 cutter and more particularly at the level of the most fragile areas to relieve any pressure.
- The impression is taken with zinc oxide paste or other flowable material.
3 – Secondary anatomical-functional impressions using a thermoplastic material:
- Indication:
- Advanced resorption in the upper jaw with a flat, reduced support surface covered with healthy, adherent fibromucosa.
- In the mandible, in cases of narrow, high, sharp ridges.
- The principle is to exert compression in the axial direction over the entire extent of the support surface, retention is ensured by compression of the entire area of the peripheral seal.
B- Secondary impression under occlusal pressure:
- Definition :
It is an anatomical functional imprint that allows the recording of the supporting tissues in the position they will occupy under the effect of masticatory pressures.
- Benefits :
- The pressure exerted during recording is comparable to that which will be applied to the future prosthesis.
- The elimination of our fingers in the patient’s mouth results in the absence of abnormal contraction of the paraprosthetic organs.
- The physiological play of exteroception intervenes in all its fullness.
- Indication:
- Complete edentulous arch opposed to natural teeth or a partial prosthesis or existing prosthesis.
- Neuro-muscular and neuro-articular conditioning made it possible to eliminate acquired postural or occlusion reflexes.
- When the patient cooperates effectively.
- When we want the most physiological recording possible in the play of paraprosthetic organs during functions.
- Contraindication :
- Cases of mobile, poorly adherent support surfaces, red, hyperemic fibromucosal membrane.
- A progressive pathological process which risks accelerating bone resorption under the slightest compression.
- Frustrated or overly nervous patients who cannot control the pressure exerted.
- Principle:
- Single-maxillary impressions under occlusal pressure.
- Bi-maxillary impression taken with PEI.
- Bi-maxillary impression taken with duplicate of the transitional prostheses or the old prostheses.
1-Unimaxillary impression:
Identical to the technique of simple analytical impressions under digital pressure.
The particularities of this technique are:
- Determination of the vertical dimension (VD).
- Recording on the bead of the centered relation.
- This impression is made in occlusion, repeat the swallowing test several times and protraction of the lips and retraction of the corners.
2-Bi-maxillary impression under occlusal pressure:
Bimaxillary impression made with a PEI, in the same way as simple analytical impressions under digital pressure, only the means of gripping differ according to the adapted occlusal pressure system or using prostheses.
C- Analytical conditioning prints:
– Made with a delayed-setting plastic impression material ; generally taken with models as close as possible to the future prostheses.
– They can also be taken with the duplicate of existing prostheses
– They are ambulatory.
– They mold the covering fabrics of the support surface into the position they occupy during the various functions.
– They allow the rehabilitation of temporary prostheses or certain recent prostheses lacking stability
– They ensure molding of the three main parts of the future prosthesis in the best possible tissue and neuro-articular conditions.
4- Processing of secondary prints in the laboratory.
Secondary impressions in total prosthesis
Formwork of the prints:
It consists of an entablature of approximately 3 mm made around the entire periphery of the print at the level of its largest contour line.
For this purpose, sticky wax is placed on the periphery of the impression, just beyond the line of greatest bulge. It will be used to fix a horizontal strip of wax. The placement of this strip begins in the posterior part of the impression, where it runs along the entire vestibular perimeter.
In the maxilla, the entablature of the posterior limit forms an angle of approximately 30° with the edge of the impression in order to clearly materialize the latter on the model and distinguish it from the support surface.
For the mandibular impression, the retromolar trigone area requires a wider wax strip (approximately 1 cm), also inclined horizontally, to avoid a fragile area at this level.
For the lingual part, the preparation is the same but it is necessary to place a triangle of wax cut to the dimensions of the lingual space which must be closed, glued and connected to the peripheral wax strip.
Finally, a sheet of wax is glued to this entablature, perpendicularly, to create the vertical wall of the formwork, high enough to create a model whose less thick part reaches at least 1 cm.
Casting the prints:
Complete denture-specific plaster prepared according to the manufacturer’s instructions is poured into this formwork. After hardening, the wax is removed and the impression is carefully removed. The thickness of the formwork is adjusted if necessary.
Occlusion bases:
Before constructing the occlusion bases, it is advisable to trace the longitudinal axes of the edentulous ridges which are transferred to the entablature of the models.
The occlusion bases must not deform under the effect of the pressure exerted during the various manipulations of the recording, of the intermaxillary relationship. They are carried out:
- Either in acrylic resin, but they can then damage the secondary models;
- Either in rubber base (true base) with reinforcement threads.
The base edges faithfully reproduce those of the secondary impression . The use of an eraser or a piece of re-cut silicone allows the material to be pressed down at the bottom of the vestibule to give it the recorded volume.
The occlusal rim will be made of composition (Stent’s) or hard wax (Moyco extra hard type). Its shape generally reproduces the edentulous arch. This shape may have been modified in the clinic by the practitioner on the individual impression tray at the time of the secondary impression. This modification must be reported and respected on the rim of the occlusion models.
When the dimensions of the bead are not determined punctually in the office, the following values are given:
- 10 to 11 mm above the crest for its height;
- From 4 to 5 mm for its width, slightly larger than that of the individual impression tray for better stability when recording the intermaxillary relationship.
Finally, the occlusion models must be stabilized on their respective vaselined models, using zinc oxide-eugenol paste (Impression Past from ss White) in order to guarantee their repositioning in the mouths and on the models.
Conclusion :
The preliminary impression is inseparable from the secondary impression, both in the choice of materials and in the choice of technique. They are complementary. It is necessary for each practitioner to know and respect the steps in order to obtain the best possible result for the patient.
Secondary impressions in total prosthesis
Bibliographic references:
- Alfred H GEERING and M. KUNDERT; Atlas of Dental Medicine: Total and Composite Adjunct Prosthesis; Flammarion Medicine-Science.
- J. LEJOYEUX; Complete prosthesis: volume 01: Clinical examination, Preprosthetic treatment, Materials and impression techniques; 3rd edition; Maloine, SA Publisher; 1979.
- M. POMPIGNOLI, JY DOUKHAN, D. RAUX; Clinical Guide: Complete Prosthesis Clinic and Laboratory, Volume 01; Edition Cdp, November 2004.
- Website: 805 Laboratory Steps in Complete Prosthesis.
Secondary impressions in total prosthesis
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