Treatment of different edentulousness by PPAC Pre-prosthetic treatment

Pre-prosthetic treatment:

• orthodontic trt 
  •             periodontal treatment: Treatment of the periodontal pocket.             conservative dentistry treatment: root canal treatment, caries             surgical treatment: crown lengthening
  •     Production of temporary prosthesis: acrylic PPA.

             immediate partial prosthesis

            evolving prosthesis; addition of a prosthetic tooth to an old prosthesis.

• Tissue conditioning, neuromuscular and articular.

I. Preprosthetic occlusal analysis to establish a balanced occlusion

Selective grinding :

            promote centering and wedging of the mandible.

• Eliminate interference in ORC-OIM
  •          establishment or improvement of mandible guidance in propulsion and diduction.
  •          correction of egressions or malpositions to reestablish functional curves.

II. Determination of the insertion axis:

The clinical objective of the model analysis on a parallelizer is to determine “the most favorable insertion axis which allows to obtain:

 – guided insertion with gentle friction of the prosthesis, without scoliodontic action on the soft tissues,

• stabilization of the prosthesis without harming the stabilization of the supporting tooth,
•  – balanced retention,
•  – a satisfying aesthetic.”

Definition of a parallelizer

               The parallelizer is an essential mechanical device in the office and laboratory, which allows the analysis of study models along a chosen axis and the demonstration of relative parallelism for the insertion of the partial metallic removable prosthesis between the dento-periodontal and osteomucosal support structures.

• Parallelizer Description:
• -Base
• -Double-jointed horizontal arm
• -A vertical boom with an accessory at its end.
• -A base that can be moved using a ball joint.
• Parallelizer accessories: Withdrawal gauges, knives, guide rod, lead

It allows to achieve the parallelism of the guiding surfaces, the balance of the zones of

retention as well as optimizing the aesthetics of the future prosthesis with the minimum

of coronary preparations .

Treatment of different edentulousness by PPAC Pre-prosthetic treatment

ROLES of the parallelizer:

Using a parallelizer allows:

 At the office:.

– the optimal choice and determination of the axis of insertion and deinsertion of the future prosthesis    

    to dento-periodontal and osteomucosal structures.

– Objectify the anatomical obstacles to easy and non-traumatic insertion.

– Assess the corrections to be made to the anatomical structures while ensuring that they are minimal.

– Reveal areas that can be used for stabilization and retention of the prosthesis.

– Ensure an aesthetic and harmonious rehabilitation.

– highlight the undercut areas of a partially edentulous arch.

      In the laboratory:

– Development of the chassis.

– Development of prosthetic crowns with a morphology adapted to the partial metal prosthesis.

– Setting up attachments.

– The ideal outline of the hooks     

Using the parallelizer

4-1 Determination of the insertion axis

The axis of insertion is the trajectory along which the patient must insert and remove his prosthesis. The axis of insertion will always be a relative axis resulting from a compromise between aesthetics, retention and stabilization.

The insertion axis represents a compromise between the dental axes, perpendicular to the occlusal plane. It must also take into account the orientation of the edentulous ridges.

The chosen insertion axis must be: – optimal, – simple, – unique,

• Roach method (three points)

The three-point method is very simple: three points are drawn on the model, forming

thus a plane between them. The insertion trajectory will be perpendicular to this plane.

• Roth method (bisectors)

The bisector method takes into account the degree of inclination of the implantation axis

support teeth, in order to position the model in two directions: antero-posterior and latero-lateral.

• Applegate Method (Toggle)

Applegate’s method is to balance the height of the equator as much as possible

prosthetic of each supporting tooth. Ideally, the prosthetic equator should be between the cervical third and the middle third of each tooth.

Comparison of the insertion axis thus obtained with the 4 parameters.

Treatment of different edentulousness by PPAC Pre-prosthetic treatment

following:

         The chosen insertion axis must be transmitted to the laboratory .

Tracing of frontal and sagittal landmarks

4-2 Drawing the guide lines

The guide line is the set of the most salient points of the crown obtained by moving a graphite lead applied tangentially to a crown of a tooth always parallel to the chosen insertion axis.

It is different from the line of greatest anatomical contour, since the reference axis is not the same

  The guide line delimits the clearance and undercut areas along the axis

determined prosthetic.

4-3 Measuring retention depth

   The maximum retention point is determined when the withdrawal gauge is tangent to the guide line by its stem and tangent to the tooth by its collar.

It determines the location of the active retentive arm of the hook.

The gauge consists of 2 parts:

   • A rod intended to be fixed to the vertical chuck of the jib.

   • A disc on the free end of the rod and perpendicular to this rod, this disc comes in three diameters: 0.25, 050 and 0.75mm.

Determination of the point of maximum retention at the level of the disto- or mesio- vestibular angle

   The retention is all the greater as the chosen withdrawal gauge, for a given insertion axis, has a wider collar.

4-4 Analysis and preparation of guide surfaces

a) Proximal surfaces:                                                     

– reduction of the cervical convergence angle between the analysis rod and the proximal face of the tooth.

b) Lingual or palatal surfaces:      

-in order to ensure reciprocity of action

Preparation of these guide surfaces allows guided insertion of the prosthesis.

4-5 Highlighting of osteomucosal interferences

Osteomucosal undercuts constitute obstacles to the insertion of the prosthesis.

If they are not surgically corrected during the pre-prosthetic phase, these

interferences become a priority when choosing the insertion axis in relation to the withdrawal zones and guide surfaces.

Treatment of different edentulousness by PPAC Pre-prosthetic treatment