BIOMECHANICAL FACTORS IN JOINT PROSTHESIS

BIOMECHANICAL FACTORS IN JOINT PROSTHESIS

1. INTRODUCTION: the fixation of artificial dental elements in a joint prosthesis does not mean in any situation that the prosthetic reconstruction is safe from any destabilization, the control or not of the different factors involved in the stabilization and destabilization of fixed prostheses plays a primordial role in the success of the treatment and the durability of the Dento-prosthetic complex.
2. DEFINITIONS:
   1. Retention: militant forces against 

shear  

2. Stabilization: militant forces against compression

 to pull-ups 

3. Sealing Cement: fixing materials which 

Need mechanical factors to fill 

its sealing mission.

4. Collage: adhesion system reserved for elements 

Film coated 

such as veneers and bonded bridges. 

BIOMECHANICAL FACTORS IN JOINT PROSTHESIS

3. BIOMECHANICAL FACTORS  :
4. Retention: Retention prevents the detachment of the prosthesis in the direction of its insertion axis or that of the preparation. The sealing cement is subjected to traction and shear.

-For good retention we can intervene on the following factors: 

1. Mechanical means:  
   1. The draft: the angle of a face of the preparation with its major axis is the draft of this face. The more the draft increases, the more the retention decreases, over the

Preparing a taper 

(i.e. the angle formed by 

the faces of the preparation) 

Less than 10 ^o is always 

Tolerable, the ideal is 

to achieve convergence 

occlusal of 6 ^o Per prey.

2. The extent and shape of the preparation: retention increases with increasing tooth surface area. The greater the surface area of ​​the luting cement between the reconstruction and the preparation, the better the retention. The more walls a preparation has, the more retentive it is. (Next figure) 

3. The surface condition of the preparation: Retention by the sealing cement is achieved through the microroughness of the dental surface; a surface that is too rough, on the other hand, influences the wettability of the cement, in other words it blocks the spreading of the cement. The best compromise must be found between a smooth and polished surface and a slightly rough surface.   
4. The cervical limit: a prosthetic piece without defects and perfectly adapted to the preparation provides primary retention before sealing. The precision of the dento-pothetic joint after sealing depends essentially on the thickness of the cement film interposed between the two surfaces. This thickness is a function of many factors related to the physicochemical properties of the cement.
5. Geometric means:
   1. The insertion axis: Retention is improved by geometrically restricting the number of possible paths for disinsertion of the reconstruction.

( a single axis of I, in b several axes because of the exaggerated conicity of the preparation)

3. Chemical means: 
   1. Sealing or bonding: 
4. Stability: Resistance which opposes the mobilization of the prosthesis under the effect of oblique compression forces and others, it depends on:
5. The lever arm  : it is the distance 

between the crown axis and 

the point of application of a force 

eccentric. This phenomenon 

translates when it comes to 

of a wide crown on 

a narrow preparation or well 

of a cantilever bridge 

(bridge with 2 elements, one of which is 

in extension)

Cantilever bridge

2. Preparation height : The height of the preparation increases the stability of the crown , for the same height of the preparation the highest crown is the least stable. For the same height of crown the highest preparation is the most stable.
3. the width of the preparation: for the same height of preparation the widest (a) is the most stable (b).
4. the draft : the draft and the stability are inversely proportional, the more the angle of the preparation increases the less the stability will be.
5. Rotation: around a vertical axis Reducing this phenomenon is a priority which is satisfied by the creation of grooves and boxes especially at the proximal level to combat this rotation. 
6. Retention of partial reconstructions: it obeys the same principles above taking into consideration that these constructions occupy cavities cut in the teeth concerned, with the exception of veneers.
7. CONCLUSION: biomechanics in joint prosthesis is the key to the success of fixed prosthesis, neglecting these principles puts in danger all the therapeutics that the patient awaits with enthusiasm.

BIOMECHANICAL FACTORS IN JOINT PROSTHESIS

  Sensitive teeth react to hot, cold or sweet.
Sensitive teeth react to hot, cold or sweet.
Ceramic crowns perfectly imitate the appearance of natural teeth.
Regular dental care reduces the risk of serious problems.
Impacted teeth can cause pain and require intervention.
Antiseptic mouthwashes help reduce plaque.
Fractured teeth can be repaired with modern techniques.
A balanced diet promotes healthy teeth and gums.
 

BIOMECHANICAL FACTORS IN JOINT PROSTHESIS