Treatment of distal edentulousness by PPMA
The therapeutic objective of PPA is not only the restoration of various functions and aesthetics but above all the preservation of the various components of the masticatory system. The treatment will be carried out according to a well-defined plan including all the stages of carrying out a PPA with a cast frame by clarifying these problems and their solutions.
2. Definitions of distal edentulism:
Distal edentulisms were grouped according to the KENNEDY-APPLEGATE classification into two classes:
- Class I : Bilateral distal edentulism
- Class II : unilateral distal edentulism
KENNEDY used complementary classes, namely:
- Class I modification 1 : bilateral distal edentulism complicated by an embedded edentulism at the level of the residual arch.
- Class II modification 1 : unilateral distal edentulism complicated by an embedded edentulism at the level of the residual arch.
3. Clinical observation
1. Interrogation
2. Clinical examination:
- Oral exo-examination
- Mouth opening examination
- Endo-oral examination
- Functional examination
- Radio examination :
- Examination of the casts : Impressions are taken from the 14th session with irreversible hydrocolloids and are poured into hard plaster.
- Examination of static casts: this examination reveals the importance and distribution of the edentulous segments in order to visualize the axis of the teeth, prepare for study with the parallelizer, and visualize the occlusal plane.
- Dynamic cast examination : on a semi-adaptable articulator. This dynamic analysis is only indicated when our clinical examination reveals occlusion disorders.
4. Therapeutic decision
Apart from the implant solution and due to the absence of the posterior pillar, these classes can only be treated with an adjunct prosthesis.
5. Treatment plan
At the end of the clinical observation, a treatment plan is determined and takes place in 3 phases:
- Preprosthetic Treatment
- Prosthetic Treatment
- Post-prosthetic Treatment
5.1. Pre-prosthetic Treatment:
Before considering prosthetic restoration, a restoration of the oral cavity is necessary in order to eliminate any pathological condition and establish favorable conditions for the design of the prosthesis.
This involves preparing the oral-dental ground for appropriate prosthetic treatment.
- Periodontal treatment
- Surgical treatment
- Endodontic treatment
- Orthodontic treatment
- Occlusal equilibration
- Conditioning
- Preparation of abutment teeth:
- Study on parallelizer:
- Definition of a parallelizer: it is an instrument intended to highlight a relative parallelism between the teeth or mucous membranes which support a prosthesis.
- Description of the parallelizer:
- Study on parallelizer:
- Role :
At the dental office:
On the study model, parallelizing it allows:
- Detect the retraction zones on the areas likely to receive a hook. If the tooth does not have a retraction zone due to its morphology, it can be created by grinding or cement restoration.
- Highlight obstacles to prosthesis insertion such as a strongly inclined tooth, ridge slope or undercut tuberosity.
- Avoid a guide line very close to the occlusal edge requiring the creation of a visible hook (unsightly)
- For the search for the guide surfaces formed by the lateral faces of the teeth which come into contact with the rigid elements of the prosthesis during insertion and removal.
- Edits should only be for email
- Choice of insertion axis: The most favorable insertion axis is the one that requires the lightest grinding and allows the prosthesis to be inserted by gentle friction on the abutment teeth without risk of damaging the fibromucosa.
- Traces of the guide line
- Determining the starting point of the hook
Preparation of the cubicles and guide surfaces
- The trace on the lateral faces of the model of the landmarks allowing the insertion axis to be objectified
In the laboratory:
On the working model resulting from the terminal imprint, the parallelizer intervenes:
- In the report of the insertion axis defined thanks to the previously traced markers
- In the development of the metal frame
Preparation in the mouth:
- Reporting of the insertion axis in the mouth
- Preparation of occlusal supports
- Preparation of the guide surfaces
- Creation of withdrawal zones
5.2. Prosthetic Treatment
5.2.1. Execution of impressions and working models: The success of a prosthetic treatment depends on the quality of the precision of the impression, which implies a judicious choice of impression material such as synthetic elastomers such as silicone. The casting is done with extra hard plaster, the model thus obtained is analyzed with a prallelizer in order to determine the insertion axis.
5.2.2. Drawing of the frame:
5.2.2.1. Factors influencing the plate layout
Type of tooth loss: we will have either
- Essentially dental support
- Mixed osteo-mucosal and dental support
Extent of the tooth gap, the main connection can be:
- A simple bar case where the tooth loss is reduced
- A double bar case or average toothlessness
- A solid plate in the presence of significant tooth loss
Biomechanical factors: To oppose the movements of the stools, take a sufficient number of abutment teeth, a mandatory presence of occlusal stops, a sufficient extent of osteo-mucosal support.
Biological factors: respect for tissue integrity (HOUSSET décolletage principle)
Clinical factors depend on:
- The extent and location of the edentulous segments
- Morphological values of the remaining elements and the support
- Patient hygiene
- His psyche
5.2.2.2. Problems related to the treatment of distal edentulousness
The 1st problem: tissue duality
- We now know, thanks to STEIGER’s work, that the tooth and the fibromucosa subjected to the same pressure undergo very different movements in proportion; this is tissue duality.
The effects under the same pressure are a sinking of the teeth of 0.1 mm with rapid and complete recovery; while the mucous film deforms by 0.4 to 2 mm but does not recover its initial shape as soon as the application of this pressure ceases but in a very slow way it is the viscoelasticity
Example: the recovery is only 67°, after 10mm in a 70 year old person, 4 to 6 hours or more will be necessary for a complete recovery while it is faster in a 24 year old subject
Difference in desmodontal and fibromucosal compressibility
Solution :
- The creation of a secondary anatomical-functional impression: it allows the best possible relationships to be obtained between the metal frame whose support is dental and the saddles whose support is osteomucosal, it allows the support to be dissociated.
- Regular monitoring and rebasing of stools: helps to remedy changes in mucoosseous support over time.
- The use of mesial secondary connection hooks allows for a balanced distribution of loads between the bone tissue and your teeth. They promote the decomposition of occlusal forces. The hooks that can be used are:
- The NALLY-MARTINET hook
- The posterior action hook
- The RPI system.
- ROACH hooks with mesial secondary connection.
2nd problem: stool movement
- For TABET, the movement of a saddle in extension can result from the combination of 6 fundamental movements in the three planes of space:
- Three translational movements
- Vertical translation
- Horizontal translation.
- Mesio-distal or distomesial translation
- Three rotational movements
- Vertical distortion rotation
- Rotation around the ridge axis
- Rotation in the horizontal plane
- Three translational movements
Solution :
- The secondary anatomical functional imprint
- The overall design of the chassis which must counteract the movements of TABET:
- The vertical translation movement is counteracted:
- In the occlusal sense: Mainly by the extent of the saddles. Partially by direct and indirect occlusal supports.
- In the occlusal direction: by the action of the retentive arms of the hooks.
- The horizontal translation movement:
- It is prevented by high ridges and steep slopes, hook wedging arms, secondary connections, fifth bar and coronaries.
- The meo-distal translation movement:
- It is blocked by the secondary connections of hooks and indirect supports, as well as the covering of the tuberosities and trigones.
- Vertical distal rotation:
- Movement towards tissues: can be limited by an anatomical-functional imprint in order to obtain broad support of the stools
- Posterior detachment is prevented by indirect supports located at a distance and by fifth boards.
- Rotation around the ridge axis:
- Due to occlusal imbalance during expansion and lack of rigidity of the frame.
- This movement is limited by a well-balanced occlusion, a sufficiently rigid frame, a wedging arm and a retentive arm alternately opposing this movement.
- Rotation in the horizontal plane:
- Arising from the occlusal forces in diagonal or transverse direction of the frame, this movement is cancelled by the rigidity of the frame and incidentally by the relief of the ridges.
5.2.2.3. Typical tracings of the different edentulisms
| Model | Maxillary | Mandible |
|---|---|---|
| ID | Main connection: Solid plate | Connection principle: Lingual bar or lingual strip |
| Secondary connection: must be reduced to the maxillae to avoid managing the tongue | Secondary connection: rigid, tissue-friendly, comfortable. | |
| Crochet – Cr Nally Marquet | Hook = SAME as for the maxi | |
| – Create a post-action | Indirect support: their presence is essential, they must be located as far as possible from the direct cleats | |
| – Cr Equipoise | ||
| – CABARRE: IY TT |
Indirect occlusal supports: their presence is not essential but they are added.
Treatment of the modification by a joint prosthesis
Treatment of the basic edentulism by a classic PPMA
| ID | Main connection: palatal plate cut ant | Edentulous side: portion of the CL I frame with |
| | Hook: Edentulous side: Nally | indirect support |
| | Toothed side: Bonwill between 6-7 for the esth | Edentulous side: Bonwill hook between 5-6 |
We treat everything by PPA
– On the saddle side: drawing II
– On the embedded saddle side: Ackers or Nally for example if we have any doubts about the conservation of the tooth
Maxillary Type C1 I Tracing
Maxillary Type C1 II Tracing
Type C1 II Mandibular Tracing
5.2.3. Preparation of the chassis in the laboratory
5.2.4. Testing the chassis in the mouth:
Once the metal frame is cast or laboratory it must be tried in the mouth. Respecting the following times:
- Examination of the casting.
- Adaptation control.
- Control of the intensity of the forces used during insertion.
- Control of occlusion ratios.
5.2.5. Anatomical-fundal impression:
- It is functional in the sense that it is made using a material that exerts slight pressure on the soft tissues and that during its creation the patient is made to exercise the different movements of the tongue, lips and cheeks. The most used impression technique remains the partial corrective impression.
- Several techniques have been described that separate the recording of hard tissues from that of soft tissues.
- Partial dissociated imprint or reconstructed model technique (the Appelgate-McCraken technique) :
- This technique described by Mac-Cracken was disseminated in Europe by J Nally. It only concerns edentulous ridges and allows the working model to be corrected in a single step from a global impression on which the metal frame was developed.
- Technique:
- The frame is tried in the mouth, in order to check its good adaptation, it is then repositioned on the model and resin impression saddles are made over the grids (spaced by a thickness of a sheet of wax) which are lost in order to allow the escape of the impression material and thus reduce the displacement of the tissues of the support surface.
The shape of the edentulous ridges is recorded with plastic wax at oral temperature (Applegate McCraken technique with Correcta wax No. 4 or No. 1).
Currently, we recommend elastomers or zinc oxide-eugenol paste and Kerr® paste. A re-marking of the edges allows us to record the functional play of the paraprosthetic organs and to ensure maximum coverage of the bearing surface, thus reducing the loads borne by the tissues.
- Finally, the impression of the support surfaces is made while ensuring that the frame is held by the occlusal supports.
- After removal and inspection, the impression is sent to the laboratory.
Technique of the reconstructed or corrected model:
- Its preparation requires 4 steps:
- Removal of the material fixed on the underside of the chassis
- Removal of the corresponding part of the model.
- Attaching the chassis to the model using sticky wax.
- Formwork of the impression and pouring of the plaster.
Global dissociated footprint:
- After correction of the PEI, the recording of the peripheral joint
- Recording the support surfaces is broken down into two stages:
- The first involves recording the osseo-mucosal surfaces using a medium-viscosity material.
- The second consists of a recording of the entire arch using two viscosities (medium viscosity on the remaining dental part of the PEI and low viscosity in a very thin layer on the first recorded part and injection
- Formwork and casting of the impression is carried out as in complete removable prosthesis.
5.2.6. Occlusion registration and articulator placement:
- Maintain or restore physiological DVO.
- Occlusion recording is done in centric relation.
- Choice of the occlusal concept: in this choice, in addition to the elements already considered, we also cite:
- The extent of toothlessness.
- The nature of the antagonistic arcade
- The quality of the previous guide.
5.2.7. Fitting the assembly
- Before polymerization, it is useful to carry out several checks:
- Phonetic control
- Stability control
- Occlusion control
5.2.8. Resin saddles extent
The saddles of any partial denture should have the largest possible surface area without encroaching on the free mucosa. This involves covering the retromolar trigones in the lower arch and the tuberosities in the upper arch.
5.2.9. Placement in the mouth: When placing the prosthesis in the mouth, it is essential to check:
- Prosthesis section
- The correct setup
- Neutrality towards abutment teeth
- Stool extension
You should also check:
- Occlusion in centric relation and maximum intercuspation
- Lateral and propulsive movement
A good balance should be achieved at this stage but the final adjustment is made at the first check 2 to 3 days later to allow the stools to adapt well in the mouth.
The patient should be instructed on:
- How to put on and take off your prosthesis
- Personal hygiene rules to apply
- The regular subsequent checks that are necessary
5.3. Post-prosthetic treatment
A first check-up after 6-8 months is essential for rebasing the stools; for this, the use of an anatomical-functional impression is recommended.
6. Conclusion
The success of prosthetic treatment depends on compliance with the various operating times and scientifically proven knowledge which allows the durability of the prosthesis over time.
But lasting success is only possible if the patient strictly follows the practitioner’s advice regarding maintaining rigorous hygiene and post-prosthetic checks which he would be required to comply with.
Treatment of distal edentulousness by PPMA
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