Composite prosthesis

Introduction :

The removable partial prosthesis with a metal framework (PAPIM), when properly designed, can still provide many services in the context of restorative therapy for partially edentulous arches. When conditions permit, it is preferable to combine metal frames with fixed prosthesis elements prepared by milling, to optimize prosthetic balance.

1. Definition:

A composite prosthesis is a so-called mixed or hybrid prosthesis , consisting of a fixed part and a removable part that must fit perfectly, connected to each other by attachments and/or precision preparations (milling). It can be a simple or complex situation depending on the clinical case.

2. Indications: The composite prosthesis is indicated:
   • In the restoration of decayed teeth entering into the therapy of PPA.
   • To improve the aesthetics and balance of a PPA.
   • Remaining teeth have a good periodontal prognosis.
   • Oral hygiene is sufficient or can be improved through motivation.
3. Contraindications:
   • Pathologies with high infectious and hemorrhagic risk.
   • Insufficient or even absent oral hygiene.
   • Remaining fragile teeth (Direct passage to PAT).
   • Poor and unstable periodontal prognosis.
   • Condition of the ridges unfavorable to the insertion of prostheses (strong undercuts).

4. Objectives of composite prosthesis:
   • Improved biocompatibility and comfort thanks to better distribution and quality of dental and mucosal support.
   • A more discreet positioning of the hooks or their removal in favor of attachments to improve aesthetics.
   • Achieving better prosthetic balance in relation to the optimization of Housset’s triad.
5. Milling : Additional devices made in the laboratory, also called machined fittings for fixed prostheses; The extreme precision they require requires the use of a milling machine . They increase stabilization and retention by friction of the walls

prepared on the guide surface and avoid the constraints inherent in the insertion and removal of the prosthesis. They can be differentiated into primary millings and secondary millings.

1. Main millings:

They are used in treatments using “complex” composite prostheses, i.e. using retention by attachments.

• Provide a large part of prosthetic balance.
• Indicated for terminal edentulism.
• Located mesially on the fixed element in the shape of a cylinder or dovetail or omega.
• Allows for three-dimensional locking.
• Free the distal face for attachment.

“Omega” shape of the main milling

5. 2. Secondary milling :

Secondary millings are represented by preparations for support bars, wedging arms and additional supports (occlusal stops)

• They have a secondary role.
• Mainly opposed to rotational movements of the prosthesis.
• Strengthen the structure of the prosthesis by stiffening it
• Located on the palatal or lingual surfaces and must have a minimum thickness of 0.5mm.
• Must have a height of at least half the clinical crown on posterior teeth.

Secondary milling for cingulate support bar

3. Benefits of milling : Milling allows:
   • To include the hook in the lingual or vestibular bulge of the prosthetic teeth, avoiding the creation of an overhang at the gum level. This overhang would hinder correct food deflection and lead to food retention.
   • Correct occlusion of the supporting tooth; the occlusal support disappears into the space created in the crown.
   • Correct realization of the contact point by creating a contact area in the insertion axis of the PPAC
   • To integrate the PAP into the original morphology of the supporting tooth.
4. Disadvantages of milling:

• The rigidity of the millings which requires the joining of several dental elements.
• The height required to achieve them requires compromises at the level of the embrasures.
• The volume of milling results in significant mutilation of the supporting teeth, very often indicating their loss of pulp.
• Since retention is ensured by friction, in the event of wear there is a loss of friction without the possibility of correction; this is why millings are used in conjunction with attachments which, in most cases, can either be activated or replaced.

5. Production technique:

Milling is carried out in the laboratory along the insertion axis on the wax models or directly on the cast crown, the insertion axis being previously fixed to the parallelizer.

Laboratory milling machine

Preforming of millings using a wax milling cutter and grinding of a milling after casting

6. Attachments:

The attachment is a mechanical system made up of two parts; male and female. These two elements are the exact negative of one in relation to the other. The male part, also called the matrix, is most often attached to the fixed prosthesis and the female part, also called the matrix, is most often attached to the removable prosthesis.

According to the topography, these attachments are classified into:

• Extracoronary attachments
• Intracoronary attachments
• Axial attachments
• Connection bar or conjunction

7. Composite prosthesis treatment plan :

The success of this type of more or less complex prosthesis requires absolute respect for the design stages.

• Clinical examination : In order to establish a diagnosis, to put forward therapeutic hypotheses, and then to make a decision in agreement with the patient, the practitioner carries out a clinical examination and collects additional data (radiographic assessment, study models).
• Drawing the outline on the study model : It is the role of the practitioner, designer of the prosthesis, to draw the outline of the frame on the study model. To do this, the study models are studied with a parallelizer in order to determine the insertion axis of the future prosthesis.
• The creation of a master montage:

In the event that the current occlusal pattern is disturbed, it must be reworked as part of a global prosthetic project using a guide assembly .

Depending on the extent of the occlusal disturbances and the extent of the edentulism, this guide assembly can be represented by diagnostic waxes on the residual teeth and/or by models fitted with prosthetic teeth compensating for the edentulism.

Diagnostic waxes and the PAP master assembly prefigure the expected final result. They allow for a better visualization of the project and the identification of certain obstacles to the planned treatment and the highlighting of subtractive coronary artery reconstructions to be performed.

• Impression of the fixed prosthesis:
  • Preparation of the teeth affected by the joint prosthesis: The space required for milling is created by increased dental preparations.
  • Impression of the preparations: taken with a double viscosity addition silicone
  • Casting the impression: the impression is cast twice in extra-hard plaster: the first model is prepared for the production of the fixed elements (trimming, setting in die); the second model for the production of an occlusion model in order to put the two models in an articulator. This model can be transferred in an identical situation to the working model of the joint prosthesis.
• The temporary prosthesis: A temporary fixed prosthesis generally obtained by self-molding from diagnostic waxes is put in place.

• Making the fixed prosthesis caps: at this stage, the attachments are first positioned parallel to the insertion axis before being secured to the fixed prostheses.
• Precision preparation (Milling): The milling is oriented along the insertion axis and must be machined in the laboratory.
• Testing of metal infrastructures: they are clinically tested, validated, then returned to the laboratory for the development of the ceramic.
• Sealing of fixed elements: Depending on the complexity of the finished fixed prosthesis. Two options can be considered

• When dealing with single crowns without attachment support, they should be permanently sealed before the impression intended for PPA (immediate sealing).
• When it comes to fixed crowns, with complex milling or attachment support crowns, it is advisable to train these fixed prosthesis elements in the secondary impression intended for the development of the frame. The fixed elements in this case will be sealed on the day of the PPA installation (deferred sealing)
• Production of the removable partial prosthesis with metal frame:

An over-impression or a position impression will therefore be made; this is a particularity of the composite prosthesis when the fixed prosthesis elements must be driven into the secondary impression (complex case of milling and attachment).

This impression is intended to obtain on the working model a precise positioning of previously made fixed elements; and not sealed in order to be able to make the chassis

metal directly onto them using a casting technique called over-casting, which consists of directly casting the frame of the partial removable prosthesis onto the fixed prosthesis elements made from an alloy of the same family.

An Occlusion Registration is required for the design of the chassis plate; it is performed using the occlusion models

After the frame has been made, a second recording is made with the frame plate for mounting the artificial teeth.

Noticed :

For unsealed copings or crowns taken into the secondary impression for the production of the removable prosthesis; the ceramic is fired after the

casting of the frame and wax mounting of the prosthetic teeth.

To connect the attachment system to the removable prosthesis there are two solutions:

• Either the attachment is connected to the resin of the prosthesis.
• Either it is brazed onto the metal frame.

After having carried out all the necessary fittings concerning the aesthetics and the good adaptation of the finished prostheses ; advice on hygiene and maintenance of the prosthesis is given, insisting on the need for a regular check-up every six months to ensure the durability of the prosthetic restoration.

Conclusion :

Despite the rise of implantology, composite prosthesis still constitutes an attractive alternative; however, the guarantee of its success requires a systematic multidisciplinary approach, a codified and rigorous methodology based on respect for tissue health, the temporization and validation of aesthetic and functional results by fixed and removable provisional prostheses, the correct choice of the outline of the metal frame, millings and attachments.

Bibliography:

1. begin.m, “treatment of partial edentulism with composite prosthesis: sliding attachments, ADF notebooks – No. 8 – 2nd quarter 2000
2. Fouilloux I, Hurtado S. Begin M. Composite prosthesis: clinician-prosthetist communication. Prosthetic strategy. 2002; 2 (1): 15-27.
3. Begin M, Fouilloux I. The removable partial prosthesis: design and layout of the frames. Paris, Collection Réussir,

Quintessence International, 2004.

4. Santoni P. Mastering the removable partial prosthesis. Paris, JPIO Collection, CdP editions, 2004.
5. Begin.M, Cheylan.Jm , what are the particularities of impressions in composite prosthesis, Prosthetic Strategy February 2005 • vol 5, n° 1
6. Cheylan.JM, Fouilloux.I, Creation of a removable prosthesis with milled crowns,

Clinical Realities 2013. Vol. 24, No. 3: pp. 237-246

Composite prosthesis

  Wisdom teeth can cause infections if not removed in time.
Dental crowns protect teeth weakened by cavities or fractures.
Inflamed gums can be a sign of gingivitis or periodontitis.
Clear aligners discreetly and comfortably correct teeth.
Modern dental fillings use biocompatible and aesthetic materials.
Interdental brushes remove food debris between teeth.
Adequate hydration helps maintain healthy saliva, which is essential for dental health.
 

Composite prosthesis